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Assessment of Propane Fired Gas Air Conditioning, Heat Pumping and Dehumidification Technologies, Products, Markets and Economics
Submitted to:
Mr. Gregory Kerr Director of Research & Development
Propane Education & Research Council Street: 1140 Connecticut Ave. N.W.
1140 Connecticut Avenue, NW, Suite 1075 Washington, DC 20036
Technical Review for PERC by: Richard Sweetser
President EXERGY Partners Corp. 12020 Meadowville Court
Herndon, VA 20170
Submitted by: Dr. William Ryan
Energy Resources Center The University of Illinois at Chicago Energy Resources Center (MC 156)
1309 South Halsted Street, 2nd Floor Chicago, Illinois - 60607
January 19, 2007
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Table of Contents
Executive Summary .................................................................................................................... vii Introduction and Focus .................................................................................................................1
What is “Gas Cooling”?.............................................................................................................................1 Report Approach.......................................................................................................................................1
Chapter 1: Gas Cooling Technology Background.........................................................................3 Overview...................................................................................................................................................3 Lithium Bromide Absorption Chillers ........................................................................................................3
Operation..............................................................................................................................................................3 Lithium Bromide Absorption Chillers Application ..................................................................................................3 Large Lithium Bromide Chiller (> 100 RT) Markets and Economics .....................................................................4 Small Lithium Bromide Chiller (< 30 RT) Markets and Economics ......................................................................5
Ammonia Water Cooling Systems............................................................................................................6 Absorption Chillers ...............................................................................................................................................6 Ammonia water absorption heat pump .................................................................................................................6
Propane Firing ..........................................................................................................................................6 Issues with Small Absorption Chillers.......................................................................................................6 Ammonia Water Refrigerators ..................................................................................................................7 Engine Chillers..........................................................................................................................................8
Operation..............................................................................................................................................................8 Engine Heat Pumps..................................................................................................................................9
Issues with Engine Heat Pumps ...........................................................................................................................9 Operating Engine-Driven Chillers and Heat Pumps on Propane ........................................................................10
Solid Desiccant Systems ........................................................................................................................11 Operation............................................................................................................................................................11 Propane Firing ....................................................................................................................................................11 Desiccant System Applications...........................................................................................................................11 Recent Developments in Solid Desiccant Systems ............................................................................................12
Liquid Desiccant Systems.......................................................................................................................14 Chapter 2: History and Issues in Gas Cooling Development......................................................15
The Origins of Gas Cooling ....................................................................................................................15 The Residential Gas Air Conditioning.....................................................................................................15 Specific Developments and Lessons Learned .......................................................................................17
Engine Heat Pumps............................................................................................................................................17 Triathlon..............................................................................................................................................................17 Thermo King .......................................................................................................................................................18 Goettl ..................................................................................................................................................................18
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Desiccant Systems: A Different History..................................................................................................19 Chapter 3: Propane/Gas Fired Cooling Equipment ....................................................................20
Commercially Available Cooling Equipment...........................................................................................22 Broad 4.5 RT Double Effect HW Chiller..............................................................................................................22 Rotartica .............................................................................................................................................................23 Robur Air Conditioning .......................................................................................................................................24 Robur Heat Pump...............................................................................................................................................24 Yazaki Energy Systems......................................................................................................................................26
Cooling Systems under Development ....................................................................................................27 Ambien Heat Pump/Cooling System ..................................................................................................................27 Chemisorption Systems......................................................................................................................................28 Cooling Technologies Cooling System ...............................................................................................................29 Energy Concepts, Inc. ........................................................................................................................................30 Thermax Ltd (Thermax-USA) .............................................................................................................................31 GEDAC Engine Heat Pump................................................................................................................................32
Propane Refrigerators ............................................................................................................................33 Propane Refrigerators ............................................................................................................................34 Commercially Available Desiccant Dehumidification Systems...............................................................35
SEMCO Revolution ............................................................................................................................................36 Munters...............................................................................................................................................................37 NovelAire Residential Gas-Fired Dehumidifier ...................................................................................................38
Desiccant Dehumidification Systems under Development.....................................................................39 Mississippi State Residential Desiccant .............................................................................................................39 Kathabar Liquid Desiccants ................................................................................................................................39 AIL Research Liquid Desiccant Development.....................................................................................................41
Chapter 4: New Applications for Propane Fired Cooling ............................................................43 The Hotel/Resort Market for Desiccant Dehumidification.......................................................................43 Remote Eco-Tourist Hotels.....................................................................................................................44 Heat Pump Swimming Pool Heaters. .....................................................................................................45 The “Snowbird” Desiccant Dehumidifier .................................................................................................45 The Remote Vacation Home ..................................................................................................................46 High End Homes with Unreliable Electric Supply ...................................................................................47
Chapter 5: Propane Opportunity in CHP with Thermally Driven Cooling...................................48 Smaller Reciprocating Engine Generating Systems ..............................................................................50
Hess Microgen....................................................................................................................................................50 Coastintelligen.................................................................................................................51
Tecogen..............................................................................................................................................................51 Microturbine Generators .........................................................................................................................53
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Capstone Turbine ...............................................................................................................................................54 Ingersoll Rand ....................................................................................................................................................54 Elliott Microturbine ..............................................................................................................................................55
Small Generator Summary .....................................................................................................................55 Application of Thermally Driven Cooling to On-Site Generation ............................................................56
Applied Systems.................................................................................................................................................56 Packaged Systems.............................................................................................................................................56
An Economic Overview of CHP on Propane ..........................................................................................58 Appendix: Available State and Federal Incentives..............................................................................................60
Chapter 6: Economic Analysis of Propane Fired Air Conditioning.............................................61 The Economic Situation..........................................................................................................................61 Using the Economics Charts ..................................................................................................................62 Economic Analysis of Cooling and Heat Pump Systems .......................................................................65 Propane Air Conditioning in a Conventional Application ........................................................................66 Propane Fired Heat Pumps ....................................................................................................................68 The Commercial Rooftop Market for a Propane Heat Pump..................................................................73
Economics of a Commercial Heat Pump ............................................................................................................73 Business Issues in the Commercial Rooftop Market ..........................................................................................77
Third Party or Propane Dealer Financing ...............................................................................................78 The Third Part Financing Proposition .................................................................................................................79
Economic Analysis on Desiccant Systems.............................................................................................80 Opportunity .........................................................................................................................................................82 Snowbird Residential Desiccant System ............................................................................................................83
Heat Pumps with Heat Recovery............................................................................................................87 Operation............................................................................................................................................................88 Economics ..........................................................................................................................................................88
Economic Proposition for the Propane Dealer .......................................................................................91 Chapter 7: Summarized Results and Suggested Directions for Propane Driven Air Conditioning Development and Commercialization .........................................................................................94
Opportunity Summary.............................................................................................................................94 Suggested Research and Development Directions................................................................................95
1. Propane Commercial Engine Driven Heat Pump............................................................................................95 2. Snowbird Desiccant System..........................................................................................................................95 3. Desiccant Hotel Dehumidification ..................................................................................................................96 4. Propane Fired Absorption or Engine Driven AC in Off-Grid Homes ..............................................................96 5. Propane Fired Cooling with Heat Recovery...................................................................................................96 Opportunities Noted that Do Not Involve Propane Fired Cooling........................................................................97
Markets Not Recommended...................................................................................................................97
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Propane Absorption Heat Pump.........................................................................................................................97 Propane Engine Driven AC.................................................................................................................................98 Propane Fired Absorption AC.............................................................................................................................98 Off-Grid Propane Driven Cogen & Cooling .........................................................................................................98
Suggested Directions for Additional Market Research...........................................................................98 Market Forces Affecting Propane Fired Cooling...................................................................................100
Deregulation and the Condition of the Electric Generating System in the US ..................................................100 The Condition of Propane Supply.....................................................................................................................101
Appendix 1: Desiccants and Energy ........................................................................................102 An Example – Movie Theater in a Humid Climate ............................................................................................102 Ventilation Air ...................................................................................................................................................107
Summary...................................................................................................................................109 Appendix 2: Glossary...............................................................................................................110
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Executive Summary This report is an overview of the current opportunities for the propane industry for gas cooling. Available equipment, current developments, and national economics are pulled together to find areas where propane can serve as the fuel of choice for cooling systems. This involved understanding that 1) exploiting existing equipment is more practical than expensive completely new research developments, 2) the propane dealer must have a reason for promoting any resulting systems, 3) customer must have a good reason to want the system and, 4) that customers are motivated by economics, enhanced comfort or other specific benefits.
Specific markets are summarized in the table on the next page. Markets were selected based on operating costs, enhanced customers features and first cost. The chosen markets in priority order are:
1. Propane Driven Engine Driven Heat Pump and Propane Absorption Heat Pump – (Residential Cold Climate Market, All Commercial Markets) Both systems reduce winter propane load and expands summer load. Equipment includes the GEDAC, Aisin Seiki, and Yanmar engine heat pump. Opportunities include Dealer Finance Packages for Commercial Applications.
2. The “Snowbird” Desiccant System – (Southern Humid Market) Using a propane fired desiccant dehumidifier to preserve unoccupied humid climate homes in the summer without running air conditioning. This provides customer savings and enhanced dehumidification during occupied periods.
3. Desiccant Hotel/Resort Dehumidification – (Southern Humid Market) Using a propane-fired desiccant system to dehumidify ventilation air, reduce indoor humidity, odors, and mold, and preserve furnishings. Currently available equipment uses solid desiccant wheel technology with future opportunities in more efficient and compact liquid desiccant systems.
4. Propane Absorption AC with Heat Recovery – (Hot Climate Market) Propane-fired air conditioning system capable of recovering heat for heating loads such as domestic hot water or pool heating.
5. Propane Driven AC in Off-Grid Homes and Off Grid Propane Driven Cogeneration Cooling – (For Remote Locations Not Served by the Electric Grid) Both systems improve the economics of providing modern comforts to residences and small commercial buildings where connection with the utility grid would be either impossible or expensive.
All of these opportunities are based on the adaptation of existing equipment and have the potential for near-term addition to the propane load and to the number of propane customers.
The following tables summarize these opportunities. Table 1 shows the potential technologies and
Table 2 shows the potential return to the propane dealer from added propane load from these new system. In the “Opportunity Summary” section of Chapter 7, an estimate is done of what a market roll out of one of these technologies could benefit the overall propane industry. In the example, the sale of 100,000 engine heat pumps to customers in mild climates that would have otherwise used electric heat pumps would be a total 10 year revenue addition of $741 million, and an estimated margin addition of $95 million.
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Market Market Size
Operating. Cost on Propane
Equipment Available
Maintenance Needs
First Cost
Premium
Better Comfort
Propane Load
Added
MARKETS RECOMMENDED
Snowbird Desiccant System
Desiccant Motel Dehumidification Commercial Engine Driven Rooftop Heat Pump
(GEDAC System)
Engine Driven Split System Heat Pump (Aisin Seiki Type)
Ammonia Absorption Heat Pump
Ammonia Absorption AC in Off-Grid Homes
Bromide/Water Absorption AC: Off-Grid Homes
Gas Engine Heat Pump: Off-Grid Homes
Off Grid Propane Driven Cogen & Cooling
Propane Absorption AC with Heat Recovery
MARKETS NOT RECOMMENDED
Propane Engine Driven AC
Ammonia Absorption AC
Lithium Bromide/Water Absorption AC
On Grid Propane Driven Cogen & Cooling
Large Region Niche
Good Fair
Poor
Domestic Foreign
Develop
Low Fair
High
None Yes High
Yes No
Good Fair
Poor
Table 1: Summary of Technologies
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Customer New Technology Conventional Technology
Return to Propane
Dealer Per Unit
Type and Climate Heat Cool Type Heating COP
Cooling COP
Propane Use
Propane Use
Added Propane Use
MBH RT Gal./Yr
Gal./Yr Gal./Yr
Residential Hot 60 5 1.4 1.2 1071 Furnace/ AC 162 909
Residential Mild 80 5 1.4 1.2 1027 Furnace/ AC 711 316
Residential Cold 100 5
Propane Heat Pump
1.4 1.2 1155 Furnace/ AC 1076 79
Residential Hot 60 5 1.4 1.2 1071 Elec. HP 0 1071 Residential Mild 80 5 1.4 1.2 1027 Elec. HP 0 1027
Residential Cold 100 5
Propane Heat Pump 1.4 1.2 1155 Oil
Furn/AC 0 1155
Commercial Hot 120 10 1.4 1.2 2142 Gas Rooftop 323 1819
Commercial Mild 160 10 1.4 1.2 2054 Gas Rooftop 1421 633
Commercial Cold 200 10
Propane Heat Pump
1.4 1.2 2310 Gas Rooftop 2153 157
Commercial Hot 120 10 1.4 1.2 2142 Elect Rooftop 0 2142
Commercial Mild 160 10 1.4 1.2 2054 Elect Rooftop 0 2054
Commercial Cold 200 10
Propane Heat Pump
1.4 1.2 2310
Elect Rooftop 0
2310
Residential Hot Humid
400 CFM System Snowbird System 200 Elect. AC
/Dehum 0 200
Commercial Hot Humid
10000 CFM System
Desiccant Ventilation Dehumidifier 3600 Elect.AC
/Dehum 0 3600
Margin Calculation at $0.25 per Gallon Equipment Life Assumed to be 15 Years
Table 2: Summary of Propane Dealer Financial Opportunities
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Introduction and Focus Both large and small scale fuel fired cooling systems have had a long history of application across wide areas of the built environment. The focus of this report is on smaller scale cooling and dehumidification systems and technology from larger systems that might scale down to sizes applicable to residential and/or light commercial propane-based systems. This report reviews existing and emerging gas cooling systems 25 refrigeration tons (RT) and below and reviewing technologies between 25 RT and 200 RT that could be adapted to residential and light commercial loads would be most amenable to propane firing.
What is “Gas Cooling”? The expression “Gas Cooling” or “Gas Air Conditioning” is more a marketing term than a technical one. Over the years, “Gas Cooling” has come to mean any gaseous fuel driven system that can produce either sensible cooling, or dehumidification. As a gaseous fuel driven system, the most historically prevalent fuel has been natural gas. However, the market for propane fired systems, which will be largely where lower cost natural gas is not available, is less widely explored.
Technologies included under the heading of gas cooling are:
• Absorption chillers and Heat Pumps
• Engine chillers, air conditioners, and heat pumps
• Desiccant dehumidification systems
Report Approach This report is divided into distinct chapters:
Chapter 1: Gas Cooling Technology Review – which will cover the fundamentals of the processes and description of available technologies.
Chapter 2: History and Issues in Gas Cooling Development – includes general market data and reasons for success/failure to penetrate the markets.
Chapter 3. Products and Current Developers of Gas/Propane Fired Air Conditioning - covering specific product and technologies providing “Consumer Reports” type assessment of each product/technology.
Chapter 4. New Applications for Propane Fired Cooling
Chapter 5. Propane Opportunity in CHP with Thermally Driven Cooling
Chapter 6. Economic Analysis of Propane Fired Air Conditioning
Chapter 7. Summarized Results and Suggested Directions
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Chapter 1: Gas Cooling Technology Background
Overview The technologies applied to Gas Cooling are diverse. Absorption and engine driven chillers, heat pumps and desiccant cooling/dehumidification systems are the main technical approaches. In this chapter, the basics of these technologies will be reviewed to provide the appropriate technical background for the report.
Lithium Bromide Absorption Chillers
Figure 1 - Vapor Compression Cycle
Operation In a conventional electrically driven cooling system, a refrigerant is boiled at a very low pressure. At low pressure, the refrigerant boils at a low temperature, producing a cooling effect. The refrigerant vapor is then compressed to a high pressure in an electrically driven compressor. At this high pressure, the refrigerant will condense at higher temperature and reject the heat to the outdoor environment. The liquid refrigerant is then passed back to the low pressure and the process continues.
Absorption chillers use a heat driven chemical process to completely replace the electrically driven compressor in an electrically powered cooling system. Two chemical are involved in any absorption chiller. One chemical, the “absorbent”, is distilled by using heat from a fuel. This occurs in the “generator”. This purified solution then absorbs the second chemical, a refrigerant vapor, at a very low pressure. This occurs in the “absorber”. Once the refrigerant is absorbed, the chemical passes back to the generator and the refrigerant is boiled out at a high pressure. In this way, the heat activated chemical process moves the refrigerant from a low to a high pressure and replaces the electrically driven compressor.
Lithium bromide absorption chillers are available in two versions. One is a lower efficiency single effects cycle which can operate on low temperature heat. These are used today for producing cooling from waste heat streams, particularly from cogeneration systems. The other is a higher efficiency double effect absorption cycle, which is operated either on high pressure steam or directly fired by a fuel burner.
Figure 2 - Absorption Cycle
Lithium Bromide Absorption Chillers Application Lithium Bromide absorption chillers are typically applied to large commercial buildings. These systems are used to produce chilled water which is then distributed throughout the building and used to cool air via remotely mounted water cooled coils. Lithium Bromide “Water Chillers” are
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capable of Coefficients of Performance1 of up to 1.0 (direct-fired). These systems require a cooling tower to reject heat to the environment. Cooling towers which are typically used in large buildings are less common in small applications because of water use and maintenance. The exception to this is Broad Air Conditioning, which has developed a 4.4 to 30 RT product line with integrated cooling tower which the claim requires only annual maintenance.
Large Lithium Bromide Chiller (> 100 RT) Markets and Economics Lithium Bromide chillers are produced by all the major American HVAC equipment manufacturers including Trane, York, and Carrier, and have been traditionally used in areas where summer electric power is expensive, where gas company programs encouraged their use, or where electric service was too limited for electric chiller use. Currently, the largest domestic applications are replacing existing chillers, where summer steam is abundant (New York City), where waste heat streams are available (processes) and where on-site generators supply waste heat that is used to power the chiller.
Globally, absorption chillers are used where regulation or rates discourage
the use of large power consuming electric chillers that operate during the summer, which tends to be the highest electric demand period of the year.
Absorption chillers are more expensive than electric chillers. In larger sizes, single effect absorbers tend to be roughly 25% more expensive and double effect absorbers roughly 100% more expensive than “standard efficiency” electric chillers.
The current North American market penetration of large absorption chillers is roughly 5% of the overall market for large chiller systems. At current fuel prices, application of absorption chillers today tend to be only where summer electricity is extremely expensive, in particular the large urban areas along the East Coast or where a waste heat stream that can be used to drive an absorption chiller at low cost. The most common waste heat stream is heat rejected from power generation in cogeneration (CHP) systems.
The future market potential for large absorption systems depends on the future course of electric deregulation and energy prices. Open electric contracting is becoming an opportunity in industrial and commercial markets. Commercial buildings draw a summer peak power demand that exceeds the peak demand throughout the remainder of the year. Open contracting for electricity, depending on the structure of the contract, may make covering this cooling system peak expensive and motive more sales of absorption chillers to operate on any available fuel natural gas, propane, or oil, depending on availability.
1 The Coefficient of Performance, often referred to as the COP, is, in this case, the amount of cooling developed per unit of fuel or heat input to the absorption chiller. Measuring the amount of cooling and heat input in Btu/Hr results in a COP value that is dimensionless (a simple ratio)
Figure 3: Absorption Chiller for Larger Commercial Buildings (Courtesy of York International.)
Figure 4: First Costs Per Ton of Capacity of Large Chillers
Small Lithium Bromide Chiller (< 30 RT) Markets and Economics
Figure 5 – 4.4 RT Lithium Bromide Chiller (Courtesy of Broad.)
Small Lithium Bromide absorption machines are now being produced by foreign suppliers. The Broad small absorption chiller, a Chinese product, is shown in . Another innovative system being produced in Spain is the Rotartica unit. The Rotartica system is only recently entered the market and should, at present, be considered a development effort.
Figure 5
Figure 6: Rotartica Cooling System (Courtesy of Rotartica.)
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Ammonia Water Cooling Systems
Absorption Chillers Ammonia Water Absorption chillers have been traditionally used for small cooling systems. These systems also produce chilled water but use an air cooled condenser coils for rejecting heat to the environment. This allows these systems to be packaged into the same type of small air cooled outdoor units common on residences or small commercial loads. Popular in the 1960’s, these systems fell out of favor in American residential air conditioning due to low efficiency and high installed cost. Coefficients of Performance of 0.65 are as high as has been achieved in production systems to date. There is only one European supplier of these systems.
Ammonia water absorption heat pump The sole manufacture of ammonia water air conditioners, Robur has, has recently introduced a heat pump into the market. Information published on this heat pump indicates that heating efficiency cbe as high as 140%, based on fuel consumption. This technology may be of interest to the propane industry. Although a heat pump would reduce fuel used during the heating season, the fuel used to meet air conditioning loads during the summer would, in most cases, increase the annual fuel usage. In amore of the fuel would be used in the cooling season and less ithe high demand heating season.
an
ddition n
Propane Firing Large absorption chillers are either fired by a boiler or are direct fired by a gas burner. By using the appropriate burners direct
fired units can be driven by natural gas, propane, or even fuel oil. Steam driven units can be driven by a boiler burning any fuel.
The small ammonia water absorption chillers discussed above, are currently available from the manufacturer with either a natural gas or propane burners.
Issues with Small Absorption Chillers Smaller absorption chillers have had a traditional challenge with electric chillers and air conditioners based on high first cost and a lack of sufficient operating cost savings to produce a reasonable payback. In addition, the installation service network for small cooling systems is unfamiliar with absorption systems, which can make both installation and maintenance costly. On the positive side, absorption systems can often be left for long periods without regular maintenance.
Figure 8- Small Ammonia Water Gas Air Conditioner
(Photo Courtesy of Robur)
Figure 9: Small Ammonia Water Gas Heat Pump
(Photo Courtesy of Robur)
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Ammonia Water Refrigerators Absorption or a “gas refrigerators” were common in the domestic market before 1950.
Absorption refrigeration cycles are still produced in volume in both the United States and Europe, for use in three markets.
One is the recreational vehicle market. Absorption refrigerators are used in recreational vehicles as they can be operated on either electricity or propane. Recreational vehicles operate the refrigerators electrically while is on the road, and switch to propane while the vehicle is parked, thereby saving the battery.
The second market for absorption refrigerators is hotel room refrigerators and mini-bars. Absorption refrigerators have no moving parts and therefore operate soundlessly. This is a substantial advantage in the hotel rooms. In these applications, the refrigerators are operated by electricity.
The third market for absorption refrigerators is for remote locations such as cabins and campgrounds. A number of manufacturers make refrigerator that resemble residential refrigerators for these applications, all propane fired.
Absorption refrigerators use an ammonia water cycle, similar to the
ammonia water absorption cycles discussed previously. Instead of having a solution pump or any moving parts, small refrigeration cycles use natural recirculation to send solution around the system. The cycle requires only a source of heat to operate. When driven by propane, a small burner is used. A resistance heater is used when the cycle is driven electrically.
The use of propane to operate small refrigerators suggests expanding to other propane applications based on similar consumer needs. Mobile refrigeration on a small scale can be met by this type of refrigeration cycle. In general, the cycles are used only when the overall cooling load is less than a 1/2 of one ton of refrigeration. In addition, these cycles are not as efficient as larger ammonia water absorption chillers. However, the simplicity and long life of the cycle with no moving parts, often makes up for the low efficiency in small-scale cooling applications.
Figure 10 - Modern ropane Refrigerator for
Residential Use P
(Courtesy of Danby)
Figure 11 - Drawing of the Absorption Cycle Loop on a
Propane Refrigerator (Courtesy of Danby)
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Engine Chillers
Operation Another approach to gas cooling is to use the same cycle as an electric air conditioning system with a fdriven engine to drive the compressor, replacing the electric motor. With such a system, a Coefficient of Performance as high as 2.0 is possible. Engine chillers have been built in large sizes for commercial building with some domestic marketplace success. Systems down to 15 tons have been produced though the smallest size currently available is 50 RT. When built in smaller sizes, the systems are put into an air cooled package that sits outside the customers building, provides cooling water, and requires no
cooling tower. Coefficients of Performance in Cooling for smaller systems are generally in the 1.0 to 1.2 range.
uel
Two manufacturers, York and Tecogen have been producing engine chillers for the last ten years. Although not new, these chillers have only achieved a minimal penetration into the market.
Figure 12 - Large Engine Driven Chiller for Use in a Larger Commercial Building.
(Photo Courtesy of York International)
Figure 13 - Small 50 ton Air Cooled Packaged Engine Chillfor Smaller Scale Application
er
(Photo Courtesy of Tecogen)
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Engine Heat Pumps During the 1980’s, in parallel with the development of engine chillers, a number of small scale engine heat pumps were developed for the 3-50 ton market. These systems are air cooled and directly replace electric heat pumps. These small systems have not been successful to date in the United States although over 40,000
systems have been installed in Japan2.
Unlike engine chillers, engine heat pumps provide both cooling in the summer and wheating. Heat rejectedby the engine allows engine heat pumps to provide efficient heating at lower outdoor temperatures than electric heat pumps. Although an engine heat pump will add propane load during the summer, the heating function is generally at COP’s above 1.0, and therefore will not add as much propane load in the winter as a conventional
furnace. Engine heat pumps may be most attractive to the propane industry in areas where electric heat pumps are the major competitor for propane heating.
inter
Issues with Engine Heat Pumps Although engine heat pumps can offer customers a more highly efficient system than absorption based gas cooling, the engine will require regular maintenance, including oil and spark plug changes. Significant progress is being made by engine heat pump manufacturers in extending these service intervals up to 10,000 operating hours.
Unless these systems are maintained, they will be damaged or fail to operate entirely. Given that the electric heat pump and propane furnace service network is not attuned to doing essential maintenance, this can be a major cultural change in the distribution channel for heating and cooling systems. Propane suppliers may wish to provide or contract for this service to assure that proper maintenance is done, as well as develop a new line of business that with little expert competition. In this way, service contracts could be packaged with the overall sale and standard service charges might be included with the propane billing.
2 The Gas Heat Pump, Presentation by Colin Heap – Advantica Technologies Ltd, UK Heat Pump Network – 19th March 2002
Figure 15 - Schematic of an Engine Heat Pump
(Drawing Courtesy of Advantica)
Figure 14 - Engine Heat Pump in Operation
(Photo Courtesy of Yanmar)
Figure 16 - Mitsubishi Engine Heat Pump
(Photo Courtesy of Mitsubishi)
Operating Engine-Driven Chillers and Heat Pumps on Propane Engine-Driven chillers and heat pumps have generally been operated on natural gas. In order to adapt the systems to propane, carburetion systems and engine timing would need to be adjusted to handle the different fuel chemistry. In general, operating on propane may involve some degrading of the engine, as propane may cause the engine to knock if not retuned.
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Solid Desiccant Systems
Operation Desiccant systems are a variation in gas cooling. Desiccant systems supply “pure
dehumidification” and are generally used in buildings that are otherwise conventionally cooled. Desiccants have particular advantages for any application that can gain from enhanced dehumidification over and above that normally done by conventional cooling systems. Applications include any building in a humid climate that requires significant amounts of outdoor air. Schools, movie theaters, and motels are major examples. Another market is any application that can gain from very low indoor humidity like ice arenas and cold storage warehouses.
Figure 17 - Solid Desiccant Dehumidification System
(Drawing Courtesy of Munters) Solid desiccant systems are composed of a solid desiccant material or material with a desiccant coating, often arranged into a wheel. Air passes through the majority of the wheel and is dehumidified. The wheel rotates slowly in the air stream as the humidity is adsorbed onto the wheel. To remove this water from the wheel, a small segment of the wheel is heated to drive the humidity off and away to the outdoors. The dried surface of the wheel rotates back into the air stream and repeats the cycle.
Propane Firing Desiccant systems use the heat from a burner to generate hot
air which is then used to drive the humidity off of the desiccant wheel. The fuel used in this burner does not affect the process. To date natural gas is largely been used for this function. Propane can be used by equipping the system with the appropriate burner.
Figure 19: Desiccant Wheel Structure
(Drawing Courtesy of Novelaire)
Figure 18: Desiccant Dehumidifier Structured for Industrial Applications
(Photo Courtesy of Munters)
Desiccant System Applications Unlike engine or absorption cooling systems, which simply replace the electrically driven air conditioning or cooling system, desiccant systems are used specifically to remove humidity, thereby reducing the overall air conditioning load. In many applications the desiccant systems ability to reduce humidity to a greater extent than is possible with conventional air conditioning systems is a significant customer benefit.
For instance, in ice arenas, desiccant systems are
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commonly used to reduce humidity to an extremely low level, thereby preventing condensation on the ice sheet. This improves ice quality and reduces the overall load on the refrigeration system used to maintain the ice sheet.
In commercial buildings, the most common application for a desiccant system is to remove humidity from outdoor ventilation air. In humid climates, a large flow of ventilation will often build up indoor humidity to a level that cannot be adequately controlled by conventional air conditioning systems. By using a desiccant system to produce dry outdoor ventilation air, the cooling load is reduced and the tendency to build up humidity is eliminated.
These applications illustrate that desiccant systems can be used to produce costumer benefits that can not be produced in any other way. Therefore, desiccant systems are often used in applications where their benefits exceed a simple operating cost advantage. This means that desiccant systems are often used where there is a need that extends beyond simple economics savings, for example in manufacturing production processes that require low humidity, in commercial buildings that can be damaged by humidity, or in commercial applications where customer comfort is the paramount concern. In these types of
applications, desiccant systems are generally used regardless of operating costs.
Recent Developments in Solid Desiccant Systems Enhancing the dehumidification capability of air conditioning with desiccant systems has broken
down in recent years to three approaches. Each tends to be appropriate to different situations.
The first approached is passive desiccant dehumidification. In a passive desiccant dehumidifier, the desiccant wheel dehumidifies ventilation air as it enters the building. The desiccant wheel is then regenerated by using exhaust air from the building. Exhaust air at 70°F to 80°F will provide only a mild regeneration of the wheel, which in turn results in the wheel doing only a small amount of dehumidification of
the air entering the building. Also, there is no direct control as to how much dehumidification will actually occur. However, in a moderately humid climate, a passive desiccant system may improve dehumidification adequately during hot summer
periods.
The second approach, which has emerged in recent years, is using the heat rejected from a vapor compression (electric) cooling system to regenerate the desiccant wheel. This provides regeneration air to temperatures as high as 100°F to 115°F. As this is a higher temperature than the building exhaust air, the desiccant wheel is more thoroughly regenerated and provides greater dehumidification. However, there are three disadvantages to the system. First, the dehumidification provided by the system is still quite limited. The desiccant wheel is not capable of taking large amounts of humidity out of the outdoor air. Second, the desiccant wheel can
Figure 20: Desiccant Dehumidifier Structured for Treating Outdoor Air for a Commercial Building
(Photo Courtesy of Munters)
Figure 21: Passive Desiccant System (Drawing Courtesy of Munters)
Page: 13
only be regenerated when the air conditioning system is actually operating. This keeps the desiccant system from removing humidity during periods of cool damp weather. Third, thereno capability to independently control the degree of dehumidification that is occurring. As with the passive wheel, the customer must accept the amount of humidity removal being delivered
Finally the most effective way of regenerating a desiccant wheel is to use a fuel fired heater.
is
ater, the
is
This allows regeneration air to be as hot as 150°F to 160°F. This hot regeneration air will dry the desiccant wheel thoroughly, allowing the desiccant wheel to provide substantial dehumidification. In addition, by using an independently operated fired desiccant hedehumidifier can be operated at any time, whether or not the air conditioning system is in operation. This allows for independent control of humidity and temperature. In general, thtype of system would be best justified in the most humid climates with the added benefit of being able to operate the during humid cool winter weather
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Liquid Desiccant Systems Liquid desiccant systems are also used for dehumidification, largely in industrial processes. Applications to commercial space conditioning dehumidification loads have been tested at a number of locations.
Rather than using a desiccant wheel, a liquid desiccant system sprays a lithium chloride and water salt solution through the air stream to be dehumidified. As long as the lithium chloride concentration is high enough, the solution will draw humidity directly out of the air stream and into solution. Once the solution is diluted, it is taken to a “regenerator”. In the regenerator the solution is heated and sprayed through an outdoor air stream. The solution gives up moisture to
Liquid desiccant systems hanumber o
the outdoor air and is re-concentrated and the cycle repeats.
ve a f advantages over solids
ger
r, s
itation
of two components, the be
e
tage for
quid desiccant systems under development have the potential to operate
s, particularly
systems. These include:
Scalability: Liquid desiccant systems can be built to larsizes and capacities than soliddesiccant systems. As solid desiccant systems become largethe size of the wheel becomelarger in diameter, finally reaching a size that is structurally impractical. Liquid desiccant systems have no such lim
Component Arrangement: A liquid desiccant system consistsdehumidifier and the regenerator, interconnected by piping. These two components can located separately as is convenient for the installation. For instance, the dehumidifier could blocated indoors near the area requiring dehumidified air and the regenerator located outdoors. In addition, if desired, a single liquid desiccant regenerator can be used to operate multiple dehumidifiers in a piped desiccant system serving a number of dehumidified air loads.
Air Sterilization: Liquid desiccant systems spray a strong salt solution through the dehumidified air stream which has been proven to kill pathogens in the air, an advanmedical applications.
Higher Efficiency: Liat higher energy efficiencies than that of solid desiccant systems by using heat recovery heat exchangers to reduce the amount of heat needed in the regeneration process.
New System Designs: New heat exchanger designs for liquid desiccant systemthose aggressively using plastic plate technologies, hold the promise of making these systems more compact and affordable and therefore more suited for commercial applications.
Figure 22 - Liquid Desiccant Dehumidification System
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Chapter 2: History and Issues in Gas Cooling Development
The Origins of Gas Cooling Gas or fuel fired cooling systems have a history that goes back to the beginnings of the refrigeration industry. Early refrigeration systems developed in the nineteenth century used one of the two methods of operation. One was a conventional refrigerant system using a compressor not dissimilar to modern electric refrigeration systems. However, at that time, larger electric motors were not available and electricity was extremely expensive. These refrigerator systems were generally driven by steam engines which obtained their steam from a boiler, and were therefore fuel fired refrigeration systems.
Absorption systems were also commonly used at that time, for low temperature refrigeration applications, mainly making ice. These absorption systems used acid solutions rather than the lithium bromide solutions used today.
Absorption systems fell out of favor for ice making systems early in the twentieth century. However in the 1930’s and 1940’s, absorption was adapted to making cold water for air conditioning in large buildings. During that period, natural gas also became available in many large urban areas, replacing the far more expensive manufactured gas that had been previously used. At this point, absorption systems became a major player in the market for large commercial air conditioning. By the 1960’s, half of all large air conditioning systems sold in the United States were absorption chillers. Since that time, the market share has declined to roughly 5% due to advances in electric chiller design and reduction in electric prices in the 1970’s and 1980’s.
The Residential Gas Air Conditioning Production of very small air conditioning systems for homes and small commercial applications began in the 1950’s. Electric air conditioning systems of the time were both expensive and relatively expensive to operate. The availability of extremely low priced natural gas made gas air
conditioning an opportunity.
During the 1950’s, gas fired ammonia water absorption air conditioning system were developed by a number of manufacturers, most prominently Carrier, and introduced into the market. During much of the 1960’s gas air conditioning enjoyed a substantial market share.
During the same period, the number of new homes built with central air conditioning systems expanded. There was a steady reduction in electric prices during the 1970’s which led to a larger volume of electric air conditioning systems being sold. This larger volume led to a sreduction in the first cost of electric air conditioning systems making the competitive market for gas air conditioning more difficult.
Although a number of efforts were made to reduce the cost and increase the efficiency of gas air conditioners during this period, the overall result was a substantial first cost disadvantage for gas air conditioning systems by 1970.
ubstantial Figure 23: 1960’s Arkla-Servel (Now Robur) Gas Air Conditioner Installation
(Photo Courtesy of Robur)
With the energy crisis of the 1970’s, new gas connections were curtailed in suburban areas where new homes were being built. The belief that natural gas availability was diminishing had more to do with the regulatory environment of the time than any real resource limitation. This was realized by the late 1970’s and new home construction was once again opened to gas connections. However, during this connection hiatus, new gas air conditioning system sales declined substantially. This led a number of manufacturers to leave the gas air conditioning market with only one manufacturer remaining by the 1980’s. This manufacture was later bought out by Robur, the one remaining manufacturing the small gas air conditioners today.
During the late 1980’s and much of the 1990’s, the price of natural gas was in decline. This was particularly true for natural gas delivered during the summer. The predominant use for natural gas is heating. This means the natural gas was in substantial oversupply during the summer, which set the stage for low summer prices. In reaction to this, the natural gas industry once again began to promote the use of natural gas for air conditioning.
At the same time, both the natural gas industry and the Department of Energy began work on natural gas fired heat pumps. The attraction of a gas fired heat pump is a higher level of the heating efficiency than is possible with natural gas furnaces, and the removal of summer cooling load from an overloaded summer electric generation and distribution system. Significant development work was devoted to gas heat pump technology during this period, with overall financial support from both the gas industry and the department of energy totaling in excess $50 million. One product that has been commercialized the from these efforts is the Robur heat pump
The current environment for natural gas prices is far more volatile than it was during the nineteen nineties.
• Deregulated and open markets have affected natural gas prices.
• Higher oil prices have brought natural gas prices up, as many users have switched from oil to natural gas.
• The oversupply of natural gas in the summer is no longer as major an issue, as natural gas is now extensively purchased for storage systems during the summer, eliminating the much of the summer oversupply for natural gas.
• More natural gas is now used for generating electricity, particularly in summer.
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Specific Developments and Lessons Learned
Engine Heat Pumps
Triathlon The Triathlon was a 3 ton engine driven heat pump developed by the Gas Research Institute in the late 1980’s, commercialized by York International, and featured an engine built by Briggs and Stratton. Although over 3000 of the units were sold and installed, the product was not a success in the long run. Lessons learned in the overall development and commercialization include;
• The unit used a Briggs and Stratton engine developed solely for this application. During the commercialization process of a product of this type, sales volume was too low to make engine manufacturing practical. Using an engine that is also applied in other markets would have helped generate greater production volume and lower production costs.
Figure 24 - Triathlon Engine Driven Heat Pump (Photo Courtesy of Battelle)
• Overall production cost of the product was quite high and the commercialization involved a subsidy from the gas industry. As this subsidy declined during the commercialization processed, the manufacturer attempted to go through a cost reduction process on both the heat pump system and the engine. Unfortunately, although early production units were extremely reliable, the cost reduction process affected reliability of the unit. Subsequent unit failures in the market were a major cause for the unit to be withdrawn.
• The dealer network was a major problem in the commercialization. Installers were unfamiliar with the usual installation process involved and mistakes were commonly made. In addition, the unusual installation process prompted installers to charge a substantial installation premium. A gas heat pump product with an installation process that is typical of other products in the industry would have aided commercialization
• During the commercialization process, it became clear that customers desiring this heat pump were early adopters interested in the technology. This group tended to be composed of more affluent customers who possess larger homes than could be easily handled by a three ton heat pump. Unfortunately due to the dedicated engine, it was not practical to expand the product line to a larger size range as a new engine would have had to have been developed. Using an existing production engine line might have allowed for greater ease in increasing the size of the product to conform to these homes.
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Thermo King The Thermo King unit was brought out at the same time as that of the Triathlon. Thermo King is
a major manufacturer of engine-driven refrigeration systems for use in mobile applications such as refrigerated trucks. Thermo King undertook the development of a rooftop s15 ton commercial cooling system based on their existing refrigeration packages.
tyle
Unfortunately, the Thermo King package was quite expensive. Thermo King’s manufacturing approach was industrial in style, using more expensive materials that are common in the HVAC industry. Thermo King ultimately decided that the profit margins in the HVAC industry were not sufficient to maintain their interest in the product, in comparison to the higher margins in their normal refrigeration business.
Goettl Taking lessons learned from the Triathlon product development, Goettl air conditioning developed an engine heat pump in the late nineteen nineties. Goettl is a regional air conditioning manufacturer in the southwestern United States. Goettl developed and commercialized a 15 and 20 ton engine driven roof top heat pump.
The engines were supplied by Volkswagen Industrial engines. This avoided the complexity and expense of developing a proprietary engine, and allowed for a number of sizes to be built. More importantly, as these engines are sold into the industrial market for multiple uses, Goettl could obtain the engine in low volumes, as needed, without concern that the engine manufacturer would drop the engine line.
Ultimately, Goettl decided that the sales volumes were not sufficient to maintain their interest and the product was dropped. However the use of an existing engine line and a more conventional rooftop installation approach were of value in this product introduction, as many of the problems seen with the Triathlon were avoided.
Figure 25: Thermoking Engine Driven Rooftop AC (Photo Courtesy of Thermoking)
Figure 26 - Goettl Engine Heat Pump (Photo Courtesy of Goettl)
Desiccant Systems: A Different History The history of desiccant dehumidification systems is considerably different than that of other gas cooling technology options. Desiccant systems began almost entirely as industrial equipment.
When dehumidification is provided by conventional air conditioning systems, the removal of moisture from the air is a byproduct of the cooling process. In many applications, there is a desire for dry air to dehumidify, without reducing the temperature of the space. This is one of the prime applications of desiccant systems in industrial processes.
Desiccant systems also allow humidity to be reduced to a level that cannot be supplied by conventional air conditioning systems. Some manufacturing processes require extremely dry environments to operate properly, and desiccant systems are essential in these processes.
The first major application for desiccant systems in the 1930’s was cargo preservation. By dehumidifying the holds of ships, cargoes sensitive to humidity could be carried without damage.
After the Second World War, desiccant systems became widely applied to preserving the ships themselves. A large number of naval vessels were placed into storage at the end of the war, generally at storage docks, and desiccant systems were widely used to prevent internal rusting.
Further industrial applications were developed throughout the 1950’s and 1960’s. Desiccants became common for providing very dry air for pharmaceutical pill packing operations, chocolate preservation in candy manufacturing, and a number of other specific manufacturing applications.
Beginning in the late 1980’s, the gas industry began to see desiccant systems as a gas cooling opportunity. Desiccant systems were extensively explored as a potential air conditioning system, in which the desiccant system would be teamed with an evaporative cooler to provide a full fuel fired air conditioning system. However the overall cost of desiccant materials and the size of the resulting air conditioning systems made this approach impractical.
Starting in the early 1990’s, a new focus for desiccant systems was found. Desiccant systems were targeted to provide highly dehumidified ventilation air for commercial buildings. Specific commercial building applications where humidity posed a problem were selected. The most successful of these applications is in ice arenas and supermarkets. By the late 1990’s, a large segment of the new ice arena market was using desiccant systems to provide ventilation air. In addition a number of major national chains began to specify desiccant systems for new supermarkets in humid climates.
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Chapter 3: Propane/Gas Fired Cooling Equipment A survey was done on small capacity fuel fired cooling equipment that is currently available on the global market. This survey included absorption chillers, engine driven chillers, engine heat pumps, and desiccant a dehumidification systems. A large number of systems are available globally; however, many of these systems are in a larger size range that is of interest for this report.
A table of the available small systems can be seen below.
Manufacturer Cooling Capacity
(RT) Vol.
ft3/RT Type lbs / RT $ / RT Cooling COP
Hot Water Input
Cooling Water Use
(GPM/RT)
Propane Fired Status
Broad 4.5 -33 10.6 Bromide 207 $2,000 1.14 Direct Fired 3.5
Rotartica 0.85 25.8 Bromide 751 $17,647 0.50 194°F None
Robur 3 ACF 60-00 5 9.1 NH3 150 $1,220 0.64 Direct Fired None
Ambien 5 NA NH3 NA NA ~0.7 Direct Fired None
CoolTec 5 12.3 NH3 210 $1,400 0.675 Direct Fired None
Yazaki 10 Bromide 0.6-0.7 180+°F 3.5
Thermax Bromide 0.6-0.7 180+°F 3.5 Propane Fired
= Current Unit is Hot Water Driven = Current Unit is Gas Fired – Could be Converted to Propane = Propane Version Available
Status = In Development = In Production
Table 3: Small Lithium Bromide and Ammonia (NH3) Chillers
Manufacturer Cooling Capacity
(RT)
Cooling COP
Heating Capacity
(MBH)
Heating COP (Eff)
$/RT lbs / RT
Pro-pane Fired
Heating Type
Status
Robur 4 60-119 5 0.64 110.9 85.9% $1,820 195
Robur 5GAHP-AR 4.8 0.60 125%-
140% 126.2% $2,083 175
Ambien6 5 0.7 NA 140% NA NA
Propane Version = Currently Gas Fired – Can be Converted to Propane = Propane Version Available
Heating Type = Chiller/Heater = Heat Pump
Status = In Development = In Production
Table 4: Small Absorption Cooling/Heating and Heat Pump Units
3 Robur Sales Literature 4 Robur Sales Literature 5 Robur Sales Literature 6 Ammonia Absorption Technology Development for Air Conditioning Heat Pumping and Refrigeration, Distributed Energy Peer Review 2005, DOE
Page: 21
Manufact. Cooling Capacity
(RT)
Heating Capacity
(MBH)
lbs / RT $ / RT Cooling
COP1 Heating
COP1 Annual Maint.
Sound dB
Propane Potential Status
Aisen Seiki 4-16 61-229 250-
110 $1,265 1.10-1.16 1.3-1.43 Oil,
Filter, Plugs
NA
GEDAC 10-15 25.8 751 $1.200 1.0-1.2 1.4 Oil,
Filter, Plugs
NA
Sanyo 6-16 76-228 NA NA3 1.13-1.10 1.34-1.31 Oil,
Filter, Plugs
572
Yanmar 8-16 112-229 193-136 NA3 1.13.1.06 1.30-1.41
Oil, Filter, Plugs
53-582
Propane Potential = Current Unit is Gas Fired – Could be Converted to Propane = Propane Version Available
Status = In Development = Conversion to US
Market Needed = In Production
1COP’s are Fuel
Only
2At 1 Meter
3Unit Not Currently
Sold in US
Table 5: Small Engine Heat Pumps7
Manufacturer Capacity(CFM) $ / CFM Annual
Maintenance Propane Potential Status
SEMCO 8 Revolution
225 - 6000 $8-10 Belts and
Filters
Novelaire9 400 $6.25 Belts and
Filters
Munters10
1000 to 6000 $8-10 Belts and
Filters
AIL11 3000 to 6000 $9-11 Filters
Propane Potential = Current Unit is Gas Fired –
Could be Converted to Propane = Easy Propane Conversion = Propane Version Available
Prices are Retail – Not Installed
Status = In Development\ = In Production
Table 6: Small Desiccant Systems
Desiccant Systems Use Atmospheric Burners to Regenerate the Desiccant Wheel. These Burners are a Simple Conversion from Natural Gas to Propane, Little Different than Converting a Standard Furnace.
7 Yanmar Information from: The Gas Heat Pump (GHP), Colin Heap – Advantica Technologies Ltd, UK Heat Pump Network – 19th March 2002 8 Unit shown is the Semco “Revolution”, an active desiccant system equipped with gas fired regeneration. Semco does not mention a propane option in their current literature. Revolution systems also include electric air conditioning and heating equipment into a single rooftop package. 9 Unit shown is Novelaire’s only gas/propane fired units. The 400 cfm size is targeted to residential applications. 10 Units shown are structured for treating ventilation air for commercial buildings. Munters supplies a wider line for industrial applications 11 AIL Research, 18 Cameron Court, Princeton, NJ 08540, 609-452-2950 x-40
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Commercially Available Cooling Equipment
Broad12 4.5 RT Double Effect HW Chiller Broad makes a wide range of absorption chillers up to 3,300 ton in a single package. The chiller of interest in this study is a new self contained packaged unit running from 4.5 to 33 tons. This self-contained package is structured into a single outdoor unit containing all of the absorption and heat rejection components. This outdoor box then sends chilled water to the building for use in cooling via fan coils.
Standard Broad BCT 16 (4.5 RT) direct-fired double effect would cost roughly US$8,000 landed in USA. Adding 50% for dealer network yields would result in a retail price of $12,000. At the present time, these systems are not available in North America. Broad has been looking for dealers in order to make the system available.
Model BH225IX160/150-300
cooling capacity kilojoules 57,222 tons 4.5
Chilled W. outlet temp. ° C 7.22 ° F 45
Chilled W. Inlet temp. ° C 13.89 ° F 57
chilled W. flow rate L/M 306.9 GPM 9
chilled W. Head Available at Outlet Flange mm WC 124 Ft WC 26.2
pipe diameter kPa 78 In 1.5
adjustable chilled W. flow rate % 50~120 % 50~120
pressure limit kPa 393 Psig 57
Hot water Inlet ° C 170 °F 338
Hot water Outlet ° C 155 °F 311
Hot Water Flow L/M 119.2 GPM 3.5
power (208V, 1 Ph, 60 Hz) kW 1 kW 1
Length x Width x Height cm 1,118 x 660 x 1,829 inches 44 x 26 x 72
Condenser Water consumption L/M 7.5 GPM 0.22
solution wt. kg NA Lbs NA
operation wt. kg 423 Lbs 930
Table 7: Technical Specifications of the Broad 4.5 RT Double Effect HW Chiller
12 BROAD U.S.A. INC, 401 Hackensack Avenue, Suite 503, Hackensack, NJ 07601, Ph: (201) 678-3010, Fax: (201) 678-3011, E-mail: [email protected], Web: http://www.broad.com
Figure 27: Internal View of 4.5 RT Lithium Bromide
Chiller (Courtesy of Broad.)
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Rotartica13 The Rotartica system uses a proprietary sealed rotating absorption cycle. Rotartica Lithium Bromide /water absorption chillers are divided into two product lines:
Thermal SOLAR Line: Single-effect units powered by hot water, 4.5 kW (1.3 RT).
1. The SOLAR line is a single-effect Lithium Bromide /water absorption system that generates a cooling power of 4.5 kW (from 2 to 8 kW depending on conditions, see
) with a COP of 0.7. This unit is driven by hot water which could come from a solar or CHP system
Table 8
2. Gas Line: Double-effect units powered directly by a fuel fired burner, 10 kW (2.8 RT).
Rotartica is now marketing the SOLAR thermal line in Europe. The gas product line is still in its approval stage and will not be available until spring 2006.
Figure 28 shows a schematic of rotating absorption chiller. This cleverly designed device uses rotational forces to form thin films for improved heat and mass transfer rates. This translates into a very compact and lightweight absorption system.
Cost of the SOLAR unit is 4.5 kW (1.3 RT) unit is approximately $15,00014. Cost for the gas fired unit is not yet known.
13 Rotartica, Avda. Cervantes 45, 48970 Basauri (Bizkaia) Spain, Ph: (+34) 94 402 51 20, Fx: (+34) 94 402 51 21, E-mail: [email protected], Web: www.rotartica.com 14 Source ORNL - Abdi Zaltash August 2005.
Figure 28 - Rotating absorption chiller(Drawing Courtesy of Rotartica)
Figure 29: Generator unit (GU)(Photo Courtesy of Rotartica)
Table 8: Variation in Capacity for Differing Hot Water Input
Temperatures
140%1200C
115%1100C
100%1000C
90%900C
80%800C
% CapacityAvail.
Hot Water Supply
140%1200C
115%1100C
100%1000C
90%900C
80%800C
% CapacityAvail.
Hot Water Supply
Page: 24
Robur Air Conditioning The Robur Corporation manufactures and sells gas-fired central air conditioners (chillers) for residential, commercial, and light industrial use. The units are air-cooled and use a GAX15
ammonia-water cycle, and are available in 3 ton and 5 ton models. A 4 ton unit was discontinued in 1998. The 5 ton units can be used as modules and linked together to create larger configurations, up to 50 tons.
There may be as many as 50,000 Robur units in service within North America, with a lower number throughout Europe, Asia, and other countries. Robur provides distributors with training and technical support.
One or more GAX units can service multiple heating/air handler locations or zones, while electric systems generally require
a separate unit for each zone. Since the unit has few moving parts, it often lasts for over twenty years. Although Servel GAX is not as efficient as electric units, it can compete economically when natural gas prices are significantly lower than electric rates. Equipment and installation costs are roughly double those of comparable electric units. Multi-zone applications served by multi-units in a chiller link configuration can provide good seasonal and part-load efficiency. Robur’s multi-unit and multi-zone capabilities are strengths.
Originally 3, 4 and 5-ton natural gas absorption cooling units were built by Servel from the early 60’s through the late nineties. Servel was acquired by the Italian firm, Robur in 1991. Robur continued production but initially focused on distribution in Italy. The
company continued to carry the Servel product name until recently. Robur has its US headquarters in Evansville, Indiana and now markets all products under the Robur name.
Robur Heat Pump Robur’s newest product, a gas- fired absorption heat pump was introduced in Europe in 2004, and is just now being introduced in US. In addition to a 4.8 ton cooling capacity, it offers highly efficient heating capability. Although it carries higher initial purchase and installation costs than electric heat pumps, these units offer better zoning flexibility and last considerably longer than electric heat pumps. The first US installation was just completed in the northeast.
The Robur heat pump is a reversing ammonia water absorption cycle that works as an air conditioner in the cooling season and a heating source in the heating season. The same outdoor air coil that rejects
15 GAX stands for “Generator Absorber Heat Exchange”. Although technically elaborate, the concept simply productively uses heat that was wasted in older systems and uses this heat to raise the system efficiency. The result is a higher efficiency product with a somewhat higher first cost. COP’s delivered by older systems peaked at 0.48, GAX can raise efficiency up to a COP of 0.7.
Figure 30: Two 5 RT Robur Units in a Factory Packaged 10 RT
Chiller-Link
Figure 31: One Robur Chiller Feeding Chilled Water to Three
Independent Air Handlers Serving Three Different Spaces
Figure 32: Robur Air Source Gas Heat
Pump
heat in the cooling season takes in heat from the outdoor air in the heating season. This allows the unit to produce more heating than the input to the burner.
The Robur heat pump is connected to the residence or building by two water lines. In the cooling season, this water is chilled. In the heating season, warm water is delivered. Delivery within the conditioned space is generally done with a fan coil that uses the water to deliver hot or cold air.
This air source heat pump is located outdoors and therefore the only equipment needed within the occupied space is the fan coil, which can be very compact. The unit vents directly, eliminating the need for venting or any chimney stack from the building.
Robur is also advertising a gas fired water to water heat pump that could be used as a ground water, often called a geothermal, heat pump. Although the heating efficiency of a geothermal arrangement would be higher, the cost of the ground loop could add as much as $10,000 to the cost of the installation.
Just over 1,000 Heat Pump units have been sold throughout Europe since their introduction in April, 2004. About 75% of the heat pumps were air source and 25% water source. No significant problems have been reported with either unit since their introduction.
Estimated dealer prices received from Robur are:
Function Capacity Model Number
Estimated Dealer Price
Air Source Heat Pump 5 tons GAHP-AR $10,000 plus freightWater Source Heat Pump 5 tons GAHP-W $6,800 plus freight Air Conditioner 5 tons ACF60-ST $6,100 plus freight Air Conditioner with Heating Boiler 5 tons AYF60-119 $9,100 plus freight All units FOB Evansville, Indiana 47711 Freight usually runs from $175 to $350 per unit. Robur produces 5 ton units and supplies larger systems by linking units together into packages of up to 25 tons.
Table 9: Prices for Robur Heat Pumps
Page: 25
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Yazaki Energy Systems Yazaki is an international absorption manufacturer, headquartered in Japan. The North American division is headquartered in Dallas, Texas.
Yazaki offers gas fired double-effect chiller-hpackages in the 30 to 100 ton range. These uare equipped to provide either cooling or heaIn the heating mode, the system passes burneheat trough to heat the building and is not a heapump. However, this means that a direct fired unit may eliminate the need for a separate boilerfor winter heating.
eater nits
ting. r
t
Yazaki also offers hot water fired single-effect chillers in sizes down to 10 tons. These units tend to be used in specialized situations such as solar, industrial, small CHP, or other uses where
hot water is available. Yazaki claims to have over 100,000 absorption chillers operating worldwide,
Cooling Capacity (RT) 30 40 50 60 80 100 Heating Capacity (MBH) 293 391 488 586 781 976 Fuel Firing Rate (MBH) 353 471 588 706 941 1176 Natural Gas or Propane Gas Fuel, Cooling COP 1.01 – All Models, Heating Efficiency 83% - All Models
Table 10: Yazaki Small Direct Fired Chillers
Figure 33: Row of Interconnected Yazaki Chillers Mounted on a Building Roof (Photo Courtesy of Yazaki)
Page: 27
Ambien AC on Field Test (Photo Courtesy of Rocky Research)
Ambien AC System (Photo: Rocky Research)
Cooling Systems under Development
Ambien Heat Pump/Cooling System The “Ambien” gas fired cooling system development was originally set up as a joint venture between a number of gas distribution companies16. The effort was to take ammonia water gas fired air conditiontechnology developed from a number of sources, including GTI and DOE developments, and to develop a package which could then be licensed to a custom manufacturer. The utilities involved were then planning to market the system directly to gas customers.
ing
The effort with co-funded by the Department of Energy and the development work was done by Rocky Research of Boulder City, Nevada. Since the initiation of the project, the utilities involved have ended their funding. However, the Department of Energy is still
providing some development funds to move the development forward.
This new natural gas absorption air conditioning system has undergone alpha testing at Rocky Research in Boulder City, NV, and is currently in beta testing. The product is a 5-ton unit that can be linked to other units to create capacity up to 25 tons, much like the Robur product.
Four Ambien units are currently in the field performing cooling duties; one at Oak Ridge National Labs, one at a manufacturer in Corona, California, and two more in Norfolk, Virginia.
Unlike gas fired cooling systems in the past, the Ambien units can operate at part load. This allows the system to operate continuously during periods of low load. By operating at part load, the annual efficiency of this cooling system can be substantially improved as the system will cycle much less often. This is a substantial technical improvement over earlier units. Rocky Research claims that their cooling units operate at a COP of 0.7 at full load, with a seasonal efficiency of 0.8, due to the modulating capability of the system.
Rocky Research has also produced a heating heat pump based on the same cycle with a heating COP of 1.4, the equivalent of a 140% efficient furnace. However, they have not yet produced a reversible heat pump/air conditioner in one package.
The project began in 1999 and the long development time has been a concern. Ambian does not yet have the manufacturing capability to produce the units in any volume and have been unsuccessfully seeking a manufacturing partner for some time.
16 Information from Interview with Uwe Rockenfeller. President of Rocky Research. in August 2006
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Figure 34: Chemisorption System Designed for Van Cooling in Trucking (Photo Courtesy of Rocky Research)
Chemisorption Systems Chemisorption17 is another approach to fuel fired cooling. The refrigerant used is ammonia. However the ammonia interacts with a solid salt bed rather than water. This produces an absorption system that is simpler in structure than an ammonia water system. In addition, by using different salts, the cycle can be adjusted for different applications. Some salts are perfectly suited for gas cooling applications whereas others salts allow the cycle how to be adjusted down for low temperature refrigeration applications.
The simplicity of the system allows for applications that are very different than those practical with other gas fired cooling systems. For instance, Rocky Research is currently working on a very small cooling system for use the in the cabs of over the road trucks. The system would allow the engine to be turned off, and the cooling system driven directly by a diesel fuel burner, to provide overnight cooling to the sleeper cab of the truck. This small cooling system is only ¼ of a ton of cooling; making it one of the smallest and most portable fuel-fired cooling systems ever developed. The system weighs only 150 lbs., and is less than five cubic feet in size.
Given the portability of propane as a fuel, fuel fired portable cooling maybe of particular interest to the propane industry. For remote cooling applications, it is expected that this small fuel fired cooling system, will be significantly lower in first cost the than using an electric air conditioner within an on-site generator set.
Another avenue being investigated is the use of Chemisorption for refrigerators in recreational vehicles. These refrigerators have traditionally used ammonia water absorption cycles and run on electricity while the vehicle is a operating, and propane while the vehicle was parked overnight. Chemisorption can provide a smaller propane refrigeration system and one that is less sensitive to tilt, than existing propane refrigerators. In addition, chemisorption could deliver greater refrigeration capacity and a better freezer operation. This may be of interest to the propane industry for specific uses. Examples might be portable military refrigeration, camping refrigerators, medical refrigeration for field hospitals and any other application where portable refrigeration is needed.
Larger chemisorption systems operating at low temperatures can be used for food refrigeration, freezing, or food preservation. This may have an immediate aquaculture application where food quality would be improved if crops could be refrigerated or frozen in the field. In addition, these low temperature refrigeration systems could be run directly on a propane burner or operated on the exhaust heat from an internal combustion engine being used for power, transportation, or some agricultural engine driven process.
17 Information from Interview with Uwe Rockenfeller. President of Rocky Research. in August 2006
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Figure 35: Cooling Technologies 5 RT Air Conditioner
(Courtesy Cooling Tech. Inc)
Cooling Technologies Cooling System Cooling Technologies18 is a venture capital Company that was spun out of Ohio State University’s absorption development group in the late 1990’s. The company continued the universities development of an ammonia-water air conditioned using OSU’s innovative heat exchanger technology.
Cooltec developed a five ton gas fired air conditioner and produced an initial limited production of forty units. Most of these units were sold and installed on actual cooling loads. A few were tested by gas utilities such as Southern California Gas and GTI. However, increasing gas prices made the market for gas air conditioning less viable and the large venture capital investment needed to allow the company to establish a true manufacturing capability was never obtained.
Cooling Technologies is currently not in development or manufacturing of any new units, and no units have been placed in the field in the last 18 months. The company can make units available in limited quantity using a third party manufacturer. Much like the Robur product, the Cooltec concept involves a 5-ton unit that has been linked together to create capacity up to 25 tons. These larger packages have already been applied as shown in
. Figure 36
One innovative aspect of the Cooltec system is that, although originally planned for gas firing, the system has been adapted to operate on the exhaust heat from a microturbine. This microturbine/Cooltec combination forms a small cooling capable cogeneration system, and
is a good approach to building a cogeneration system in the 60-300 kW range for a commercial facility. This system has been under test at a local school and both the Toledo Art Museum and the Toledo Convention center are currently considering installing such a system. Details of this approach will be covered in the cogeneration section.
Cooling Technologies is currently discussing overseas commercialization partnerships with manufacturing firms in East Asia.
18 Information from Interview with Ron Soka. President of Cooling Technologies, Inc. in August 2006
Figure 36: Cooltec Units on Field Trial in anOffice Retail Complex in Mexico
(Photo Courtesy Cooling Tech. Inc.)
Figure 37: Cooltec Unit on Field Trial Recovering Microturbine Exhaust Heat
(Courtesy Cooling Tech. Inc.)
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Energy Concepts, Inc.
Figure 38: Thermosorber at a Poultry Processor (left), Refrigeration (+20F) Being installed at Mellon Storage to Run on
Engine Heat (Right), Freezing System Being Installed to Run on Geothermal Hot Water (Lower Left) and Waste Heat Driven Process Refrigeration (-25F) System at a Petroleum Refinery (Lower Right)
(Photo Courtesy of Energy Concepts)
Energy Concepts19 is a Maryland development firm that has been working on absorption heat pumping and cooling systems for nearly 20 years. This small company is entirely devoted to research and development and working under a number of federal and state funding agencies has produced numerous prototypes and custom absorption machines. Their focus is entirely on the ammonia/water absorption systems.
Energy Concepts has produced prototype and custom application cycles for cooling, heat pumping, and refrigeration systems, including low temperature food freezing systems, operating directly on fuel fired burners or on waste heat streams such as engine jacket heat and petrochemical flare gas, and even on hot water from solar collectors and geothermal hot water.
For propane firing at current propane prices, their most interesting technology is their cooling/refrigeration/heat pump system that they refer to as a “Thermosorber”. Intended for process applications, the system provides refrigeration and pumps the rejected heat up to a high process hot water temperature. For example, a Thermosorber at a poultry processing facility delivers 100 tons chilling (40ºF chilled water) and 3.2 MMBH hot water (136ºF hot water) while being driven by 2MMBH of steam.. As long as heat output can be productively used, this is a very efficiency approach. The heat output becomes more valuable as fuel costs rise.
Other Energy Concepts systems are their industrial heat pumps/refrigeration systems which are used for cooling and freezing operations. These are either direct fired or fired on steam or heat from an engine, solar collectors, or even geothermal heat. For example, a heat pump 19 Information from Interview with Don Erickson. President of Energy Concepts. in August 2006
demonstration at Mellon Storage produces 100 tons of refrigeration and is driven by engine waste heat. Another in Alaska produces low temperature refrigeration for ice preservation, driven by 160oF geothermal hot water.
To date, Energy Concepts systems have been largely one-of-a-kind industrial applications, although they have also developed components for smaller space conditioning heat pumps in the past. Industrial equipment is often built on a largely custom basis. However, the construction and sale of these Heat Pumps and Thermosorbers has not be converted into any free standing business independent of the research and development operation of Energy Concepts.
Thermax Ltd (Thermax-USA) Thermax Limited is a global solution provider in energy and environment engineering, specializing in energy efficient and eco-friendly solutions for business customers. They offer products and services in heating, cooling, waste heat recovery, captive power, water treatment and recycling, waste management and performance chemicals.
Thermax absorbers use a lithium bromide water cycle and offer a range of chillers starting at 10 tons and up to 1400 tons. Thermax pioneered absorption cooling technology in India, where they are based. Over 2000 Thermax absorption chillers are installed worldwide. They offer absorption chillers that work on steam, hot water or are fired directly on fuels like natural gas, LP, diesel, kerosene and custom heat-driven chillers that can work on waste heat, steam or hot water. Thermax also offers packaged solutions for industrial cooling and comfort cooling.
Thermax offers hot water driven single effect lithium bromide chillers that would integrate into a small propane fired CHP system. The Thermax Cogenie Hot Water Chiller line was designed for CHP (or Cogeneration) systems and is available from 10-80 tons.
Thermax direct fired double effect lithium bromide chillers in their Ecochill line are available from 40-76 tons, making this a viable option for smaller commercial buildings.
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GEDAC Engine Heat Pump The Gas Engine-Driven Air-Conditioning (GEDAC) group was formed as a collaborative effort between Southwest Gas and Blue Mountain Energy to develop engine driven air conditioning systems. The drive component is a Japanese engine compressor with a substantial
background of experience in the Japanese cooling market.
This engine is being packaged into a rooftop unit which is more compatible with structure of the American market. Rooftop cooling and heating systems are used in smaller commercial buildings.
In residential systems, the refrigeration system, called the condensing unit, is packaged and set outdoors and the cooling coils are mounted directly above the furnace. Conversely, a rooftop system packages all of the cooling and heating components, including the econdensing unit, into on roof-mountepackage which also includes all of the air moving equipment as shown in Figure 39.
ntire d
The plan is for the GEDAC group to do product assembly and distribution. The
product will be available the in two forms, a standard unit and a unit rated for high ambient outdoor conditions.
Figure 40: 10 Ton GEDAC Rooftop Engine Heat Pump under Assembly
Figure 39: Rooftop Unit Serving a Small Commercial Building (Return Air and Some Outdoor Air for Ventilation is Taken
Through the Heating and Cooling Coils and Blown Back into the Building. Short Ducts are all that is required to Distribute
the Conditioned Air Throughout the Space Below)
The test unit shown being assembled in Figure 40 shows all of the major components including the cooling coils, condensing coils and the compressor which in this case is driven by a fuel fired engine rather than an electric motor. As this is a heat pump, the cycle reverses to provide heating in cold weather and the cooling coil then serves as a heating coil. At present, an Aisin-Seiki engine compressor package is being used for the compressor section.
Rooftop systems are peculiar to the North American market, and are not commonly used in Japan. Therefore, the Japanese engine heat pump manufacturers have never offered a unit of this type. However, to meet the needs of the American market, a unit which fits into existing buildings and is packaged and installed in a manner familiar to the North American HVAC installers is essential in reducing or eliminating any installation cost penalty for the propane system. Current 10 ton prototypes are about 10 inches smaller than the unit shown in Figure 40, and can fit directly to the roof openings and roof curbs used by conventional 10 ton electric rooftop units.
A number of GEDAC units have been built, with units on laboratory test. GEDAC commercialization plans include developing a dealer network of certified dealers capable of providing cradle to grave service for these engine systems. GEDAC considers propane to be an important market. A special air conditioning rate from the propane industry would be helpful in obtaining applications.
One interesting approach to propane sales that was discussed with GEDAC was the possibility of independent propane dealers financing GEDAC air conditioning units. The units could then be installed at customer sites with the propane sales and lease payments bundled onto the same bill. The economics of this approach will be covered in the economics section.
The group is also negotiating with Aisin Seiki to handle the Aisin Seiki multi-zone system. This engine driven Multi-Zone unit would be used for applications where Multi-Zone arrangements are practical. The GEDAC rooftop unit will be used for the more common ducted air handling systems.
Figure 41: Aisin Seiki Multi-zone Engine Heat Pump Installation Multi-zone systems use individual cooling coils scattered around the indoor space. The units are
interconnected by refrigerant piping and the system requires no ductwork. These systems are often used in the North American market where ductwork is difficult to install. (Drawing Elements Courtesy of Aisin Seiki)
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Propane Refrigerators Even in air conditioned residences, the largest electric consumer on an annual basis is the
kitchen refrigerator20. In homes that are remote and not connected to the electric grid, a propane fired refrigerator is a technology that should be considered.
Due to the continuous nature of the refrigerator load, operating an electric refrigerator on an on-site generator is awkward. During periods when the residence is not occupied, an electric refrigerator will pose a continuing load that is often too low in electric demand to allow the generator to operate efficiency or to even continue to operate properly, and would add significant operating hours per year to the
generator, adding to engine wear.
Although Propane fired refrigerators are far less common than electric refrigerators, they are available from a number of suppliers.
Manu. Model Cu.Ft
Prop Use Lb/day
$ Feature Ship Weight
Notes Website
Servel RGE400 7.8 1.1 $1,295 167 Operates on Propane OR 120 Volt Power
Swedish Manu.
Miller 10 1.3 $1,554 180
Miller 13 1.5 $1,794 225
Danby DPR2262W 7.8 Not Listed $856 Battery
Powered Light
202 Canadian Manufacturer
http://www.danby.com/en/
Crystal Cold CC-18 18 1.5 $2,049 324
Crystal Cold CC-15 15 NL $1,849 298
Frigidaire Cabinet Amish Manufacturer
Light Optional
Crystal Cold 1806 15 3 MBH $2,249 No Light 324 Freezer Only Unit
http://www.propanerefrigerat
or.com/
UPG 15CM 13.8 1.4 $C3971 200
Price in Can. Dollars 10 &7.8 Cu. Ft.
Models Also Available Focus on Isolated
“Cabin” Market
http://www.propanerefrigerators.com/cotta
ge/
Dometic Various Var
Electric/Gas/ Kerosene
Portable and Marine Models (European
Sales Only)
http://www.dometic.com/
. Table 11: Propane Refrigerator Manufacturers
20 Energy Information Administration; A Look at Residential Energy Consumption in 1997
Figure 42: Total Electric Consumption in US Households
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Commercially Available Desiccant Dehumidification Systems The HVAC industry has been dealing with the issue of indoor air humidity build-up since the widespread introduction of improved ventilation standards in 1989. These standards dictated that more fresh air is required in commercial buildings to solve indoor air quality problems. Unfortunately, increased ventilation, particularly in humid climates has introduced more humidity into buildings than conventional systems were capable of removing. To quote from recent literature from the American Society of Heating, Refrigeration, and Air Conditioning Engineers21:
“For most commercial buildings, the key to low-cost and effective humidity control is to dry and humidify the ventilation air before that air can become a load on the other HVAC systems within the building. When using a dedicated ventilation unit for this purpose, be sure the equipment can remove or add enough moisture to compensate for internal loads as well as the loads from the ventilation air.”
Dehumidifying ventilation air traditionally meant overcooling the air to lower the humidity with a direct expansion (DX) air conditioner. This requires a lot of energy, and can make indoor conditions uncomfortably cold. Many systems use reheat, which overcools then reheats the air, which is very energy inefficient and adds complexity to the equipment. Handling this dehumidification load in humid climates is a natural market for desiccant dehumidification which can remove humidity without overcooling.
Desiccant systems have been used for decades in the industrial market to meet severe dehumidification needs. The introduction of desiccant systems into the HVAC market has been underway for the last 20 years, with desiccants initially handling problem loads. The most successful initial markets for desiccant dehumidification in HVAC was in ice rinks, where close control of humidity is essential in preventing damaging condensation, and in supermarkets, where refrigeration cases tend to provide unintentional air conditioning to aisle spaces, preventing the air conditioning from operating and causing a build up of humidity and frost on refrigerated products.
Throughout the 1990’s, both desiccant manufacturers and the gas industry pushed to apply desiccant systems to a wider market of commercial buildings including hospitals, schools, and hotels. The approach to these desiccant system applications was to apply dedicated desiccant systems to the ventilation air intakes to occupied building. Much of this equipment is available from Munters. However, the penetration into these markets was not as great as hoped. A new approach, pioneered by SEMCO, is to integrated electric vapor compression cooling and desiccant dehumidification into one package which can be used in a number of different ways in different applications including as a full stand alone air conditioning package with enhanced dehumidification capability for small buildings or as a dedicated system handling ventilation air for larger buildings that are equipped with other air conditioning packages for the remainder of the load.
21 from: Humidity Control Design Guide, ASHRAE, 2001 Chapter 10.
SEMCO Revolution The SEMCO Revolution is a combined rooftop air conditioning system and desiccant
dehumidifier. The air conditioning function is operated electrically and the desiccant system is operated by a direct fired regenerative heater. By combining the two systems into one package, the unit can be used for overall air conditioning and humidity control or can be dedicated to handling 100% outside air for ventilation in a larger commercial building.
As shown in F, the SEMCO
system integrates the air conditioning and desiccant components together and uses the cooling coil to pre-cool the air before desiccant dehumidification, which allows the wheel to dry the air more deeply. By enhancing the capacity of the wheel in this way, overall system costs are reduced. A bypass damper is included in the system to reduce dehumidification when not needed.
igure 43
Figure 44: Semco Revolutions System Installed on a Georgia Elementary School and a Florida Theater Pictures Courtesy of the Energy Solutions Center and AGA Foundation
Figure 43: Schematic of the SEMCO Revolution (Picture Courtesy of SEMCO)
The SEMCO unit is a new entry into the market for desiccant dehumidification , shows the SEMCO on field trial applications in Georgia and Texas.
Figure 44
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Munters Munters produces a large range of desiccant dehumidification systems for industrial and commercial applications. Some Munters systems are outfitted with regeneration heaters operating on gas or propane burners.
Munters HCU line, like the SEMCO Revolution, contains both cooling and desiccant dehumidification equipment in one package. Unfortunately, these systems use condenser heat from the cooling system to regenerate the desiccant wheel. This approach does not allow the desiccant system to operate unless sensible cooling is also needed
Conversely, Munters dedicated dehumidification units and their Drycool units do use gas burners to regenerate. The Drycool line includes a number of packages targeted to specific markets including the “Superaire” for supermarkets, the “Iceaire” for ice arenas, the “Freezaire” for low temperature warehousing, and the “Drycool MD” for hospital surgery applications.
Munters is the oldest and largest desiccant manufacturer in the world, and has sales operations throughout the United States.
Figure 45: Munters Iceaire System – Example of a Desiccant Package Designed for a Specific Market
(Pictures Courtesy of Munters)
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NovelAire Residential Gas-Fired Dehumidifier NovelAire Technologies DD 400-G is a gas fired desiccant residential dehumidifier designed fir residential applications. The DD 400-G uses a separate humidistat to control the humidity of the home between 45–55% RH independently of the central cooling system. The unit is a gas-fired appliance and capable of accurately maintaining the indoor humidity in the desirable range for comfort and prevention of mold or mildew.
The system can be installed in a number of ways. Figure 46 shows the system being used as a stand alone dehumidifier where either return (as shown) or outside air, or both, is dehumidified and send directly into the building. In this type of installation, dehumidification can continue even if the main air handling system is shut down. Air for regeneration of the desiccant wheel can be taken from outdoors
and air from desiccant regeneration is always vented outdoors. This warm wet regeneration air can be vented in the same manner as a clothes drier.
Figure 46: Flow Schematic of NovelAire Gas Fired 400 CFM Dehumidifier
(Picture Courtesy of GTI)
Figure 47: NovelAire Gas-Fired 400 cfm Dehumidifier
(Picture Courtesy of Novelaire)
In residential applications, the dehumidified air is often mixed into the return air to the furnace blower, allowing the large furnace blower to circulate the air throughout the home in both the winter and summer. However, independent operation is also an option which in some applications would be attractive.
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Desiccant Dehumidification Systems under Development
Mississippi State Residential Desiccant Mississippi State has developed a Center for Desiccant research that has been funded in the past by GRI and DOE. Their experience includes working on the Honeywell and ADP desiccant dehumidifiers, a small dehumidifier similar in size and application to the Novelaire system. Current projects at Mississippi State22 include work on a CHP package that will at some point incorporate a desiccant system and work on application of desiccant systems to water damage repair in the wake of Hurricane Katrina. Mississippi State is also working on a proprietary cycle for small liquid desiccant dehumidifiers that may have advantages in enhanced efficiency.
Although not covered in the conversation with Mississippi State, the use of a portable direct fired desiccant dehumidifier for use in recovery from water damage may be a natural application for propane fired desiccants. Temporarily passing a large flow of dehumidified air through a building space or residence that has experience water damage either from a flood, hurricane, roof leaks or other problems can quickly dry building materials, and may be more effective than using hot air from portable heaters. To be effective, the air should be as dry as possible, making a direct fired desiccant system attractive, and the system should be portable which takes advantage of the portability offered by using propane from on-board tanks. Only the small amount of power for the blower would need to come from another source such as the buildings power supply or a small construction generator.
Although this is not strictly a permanent cooling system, the market for humidity, flood, and mold remediation may pose a sizable propane market.
Kathabar Liquid Desiccants Kathabar is the pre-eminent supplier of liquid desiccant systems for industry. Their liquid
desiccant systems, based on the layout shown in Chapter 1, are used for applications from food processing to pharmaceuticals to electronics clean rooms. Kathabar systems operate on the principle of chemical absorption of water vapor from air. The absorbent or desiccant solution is a water solution of lithium chloride salt. This solution is non-toxic, will not vaporize, and is not degraded by common airborne contaminants.
Lithium chloride salt solution is corrosive and care has to be taken with the materials of construction of the dehumidifier as well as with filtering out the desiccant before the dried air reaches air supply ductwork. Any carryover mist from a liquid desiccant system can quickly corrode mild steel ductwork. In the past, liquid desiccant systems were constructed of highly corrosion resistant materials such as Monel,
making the cost of these systems too high for any market except for industrial applications. 22 Private Conversation with Louis Chamra of Mississippi State University , 662-325-0618
Figure 48: Kathabar Liquid Desiccant System – Large Industrial Conditioner Section
(Picture Courtesy of Kathabar Europe)
However, modern systems are often composed of plastics, such as fiberglass, which has made lower cost equipment possible.
The ability of lithium chloride salt solution to remove water vapor from air or add water vapor to air is determined by the temperature and concentration of the solution. Depending on the concentration, a liquid desiccant conditioner can deliver air at any desired relative humidity between 20% and 90%.
For a given concentration, lower air and solution temperatures enable the dehumidifier to cooler, drier air. Higher solution temperatures enable the conditioner to deliver warmer, wetter air. By controlling temperature and concentration of the lithium chloride salt solution, the system can deliver air at well controlled temperature and humidity.
Kathabar has not been active in commercial or residential markets in the past though they have developed small experimental units for commercial applications. They have also been active with AIL Research whose developments are shown in the following section.
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AIL Research Liquid Desiccant Development AIL Research23 has been working for a number of years on an innovative approach to liquid desiccant dehumidification. Unlike the Kathabar system that operated by spraying the liquid desiccant through the air to be dehumidified, in the AIL system, the air travels between a collection of plastic plates. The plates have a treated or flocked surface and a slow flow of liquid desiccant travels down the surface of each plate by gravity. As the liquid desiccant absorbs moisture from the air, heat is generated. Instead of passing this heat back to the air stream, the plates are actively cooled by aflow of cooling water on the back of each plate. This cooling allows the desiccant to absorb a greater amount of moisture before being saturated and can produce a dehumidified air stream that is close to the same temperature as before desiccant dehumidification. This has the advantage of eliminated passing the heat of
desiccation to the building where is forms an added cooling load.
eat
Plate heat exchangers can be very compact. Liquid to liquid plate heat exchangers have revolutionized the hexchanger industry over the last 30 years and this extends that technology to desiccant systems.
AIL has developed full prototype systems of their liquid desiccant dehumidifier and is currently putting these systems through laboratory testing. The larger of the two systems, rated at 6,000 cfm, is scheduled for field trial in a machine shop in Pennsylvania. The smaller of the systems, rated at 3,000 cfm, is tentatively scheduled for field testing at the Steven Institute in New York City. Systems are aimed at the commercial market.
23 Contact: Andy Lowenstein, AIL Research Inc., 18 Cameron Court, Princeton, NJ 08540, 609-452-2950 x-40
Figure 52: Psychrometric Chart Comparing a Typical Liquid Desiccant System to the AIL Research System
By Cooling the Plates, Air Passing Through the Water Cooled AIL Conditioner is Both Cooled and Dried Simultaneously.
(Drawing Courtesy of AIL)
Figure 51: Plate Type Outdoor Regenerator
(Photo Courtesy of AIL)
Figure 50:AIL Research Plate Type Figure 50: Liquid Desiccant System
(Drawing Courtesy of AIL Research)
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Like most liquid desiccant systems, the slightly greater complexity in comparison to a solid desiccant means that the market is generally for larger airflow and commercial applications. Conversely, when used on larger airflows, liquid desiccant systems are generally more compact than solid desiccant system.
Currently, the systems are structured to use 200-2100F hot water for regeneration, just slightly hotter than water used for most hydronic heating systems. Cooling of the plate heat exchangers is performed by water from the buildings cooling tower. In this form, the system fits best into a larger commercial building equipped with a hydronic boiler for heating and with a cooling tower for the main cooling chillers. However, the systems could also be outfitted with a small hydronic boiler and packaged cooling tower to comprise a complete free standing dehumidifier. At present, the initial target market for these systems is pre-treating outdoor ventilation air with heat supplied
by a hydronic boiler, which may be fired by propane, or a solar water heater system, which is outside the range of this report.
In order to commercialize this technology, AIL Research has recently formed a commercialization venture called SECA Thermal. The intended product is currently called the LDAC (Liquid Desiccant Air Conditioner).
The Seca Thermal LDAC will be offered in two sizes – 3,000 and 6,000 scfm24 – with options to run on hot water provided by an on-board propane-fired water heater or “outside” sources such as solar panels. The LDAC can also include either an on-board cooling tower or heat exchanger (for pools or applications with an available cooling water loop). Without the hot-water source and the cooling tower, the LDAC’s selling price to its sales agents after the initial “demonstration” year will be $9.35/scfm and $7.53/scfm for the 3,000 and 6,000-cfm unit respectively. At a $7.53/scfm wholesale price, the 6,000-cfm unit can be sold to customers at $9.11/scfm ($11.31/scfm for the 3,000-cfm unit) allowing for commissions and distribution costs.
A simple 6,000 scfm solid-desiccant packaged system with a cooling coil now costs the customer between $8.30 and $10.00 per scfm. These solid-desiccant systems are designed to run on steam (gas-firing is a more expensive option) and does not include the significant cost of the refrigeration system needed to work with the cooling coil. Considering its advantages—higher efficiency, smaller size and more thorough drying—the $9.11 per scfm price for the LDAC will give customers an incentive to buy the new technology as a gas-fired cooling system
24 SCFM- Standard Cubic Feet per Minute, Standard refers to air at Standard Condition of 70oF and Sea Level Air Pressure
Figure 54: Liquid Desiccant Dehumidifier Conditioner Under Laboratory Test
(Photo Courtesy of AIL)
Figure 53: Plate Heat Exchanger for Desiccant Conditioner (Photo Courtesy of AIL)
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Chapter 4: New Applications for Propane Fired Cooling In order to make propane-fired cooling systems practical, potential new applications that feature the benefits of propane may be a key element. By looking at features that only propane can provide, applications for propane-fired cooling may be practical in settings where other systems are either inconvenient or unavailable
Propane has two advantages over lower cost fuels such as natural gas. First, it can be supplied in areas beyond the natural gas distribution system. The chief use of propane today in space heating is for heating in rural or distant suburban areas beyond the reach of the natural gas system. Propane’s second advantage is the potential for portability. Propane can be packaged into cylinders and moved to a portable cooling system or carried on a mobile vehicle to provide: cooling. These advantages have benefits for both space cooling and for lower temperature refrigeration. In the case of some technologies there is also a potential for freezing. Cooling portable electronic equipment may also be a market
Propane fired cooling also has the advantage of on-site fuel storage. Even in areas served by the natural gas distribution system, a propane storage capability and the ability to run the cooling during a natural gas outage may be critical for electronic systems that have to be continuously available. In geologically stable areas of the country, natural gas systems are rarely inoperative. However, in earthquake regions, natural gas pressure may fail or be intentionally shut down after an earthquake to prevent leakage and fires. In addition, the natural gas distribution system may be a future target for sabotage and terrorism. Electronic system that must operate as a matter of national security may be another user of propane back-up. A propane back-up capability may allow an easy switch over to local fuel operation.
The Hotel/Resort Market for Desiccant Dehumidification Traditionally, hotels in the warm and humid climates have had humidity problems. Outdoor air is brought into hotels to make up for bathroom exhaust systems that operate continuously. This outdoor air is brought into a hallway spaces, passes under room doors, and enters the hotel rooms where it then travels to the bathrooms and is exhausted. This outdoor air will load the building with humidity. This is particularly severe in unoccupied rooms where the air conditioning system is not operating.
One system that has been extensively field-teby the gas industry has been equipping hotel
ventilation systems in humid climates with a dehumidifier. After outdoor air has been dehumidified, this dry outdoor air is taken into the hallways and passes to the hotel rooms and flushes humidity from both the hallways and the rooms before going to the bathroom exhausts.
sted
This dehumidification system can substantially improve the indoor conditions within the hotel by reducing humidity levels and avoiding humidity buildup in carpets, draperies, wallpaper, and furnishings, reducing their useful lifetimes due to mold build-up. Improved dehumidification reduces musty smells all too common in hotels and resorts in humid climates, as well as to extending the life of carpeting and furnishings.
Overall, there are two ways to produce this dehumidified air. One is to use a conventional electric dehumidification system which cools outdoor air to a very low temperature and then
Figure 55: Humid Climate Region in North America
reheats the air before it is admitted to the hallway spaces. Unless the air is reheated, hallways will be lowered to uncomfortable temperatures. Conversely, a desiccant dehumidification system can carry out this function operating on either natural gas or propane. For this reason this system has been extensively field tested by the natural gas industry.
Today, we see extensive development of a hotel and resort properties on barrier islands in warmer climates from Virginia to Texas. In general, most of these barrier islands are low lying and have very high water tables. As such, running natural gas distribution systems is not practical. Natural gas piping is not generally run below the surrounding water table, to avoid pipe flooding. Therefore most barrier islands do not have a natural gas distribution. Propane is a common fuel for hotels and resorts in these areas.
Due to the high cost of oceanfront property, many of these hotels are also at the higher end of the price spectrum. These high end lodging facilities tend to
cater to guests that are more discriminating about comfort issues such as humidity and odor in their selection of lodging. This makes improving the indoor conditions in these high end hotels a natural fit for a segment that is more likely to be fueled by propane rather than natural gas.
Figure 56: Dehumidified Air Flow into Motel Values shown were from field testing (Drawing Courtesy of Manor Care)
Remote Eco-Tourist Hotels There is an overall trend in the high end tourist industry toward “eco-tourism”, which involves lodgings that are often quite remote and focused on some environmental feature. Although this may be more of a trend in the international market, there are sites in North America where highly isolated hotels cater to this type of vacationer. Unlike the hotels referred to previously, these sites may be off of both the gas and electric grid. They are a potential market for both propane fired air conditioning, to remove air conditioning load from on-site generators, and propane fired desiccant dehumidification.
Ammonia water absorption refrigeration may also have a role in eco-tourist hotels. Propane refrigeration was described previously. Ammonia water refrigerators are commonly used as hotel room refrigerators, generally operated on an electric resistance heaters. These cycles have no compressor and are sold as “silent” refrigerators, useful when refrigerators are located in hotel sleeping rooms. In a remote or “eco-tourist” hotel, using propane-fired refrigeration may be an attractive option.
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Heat Pump Swimming Pool Heaters. In recent years, a market has developed for electrically driven heat pump swimming pool heaters. These heaters are generally used in the hotel market or in residential applications where natural gas is not available. In particular, rural areas and the barrier island locations previously discussed have seen a substantial assumption of this technology.
A heat pump heater will provide a high efficiency that may make them competitive to using a simple propane fired boiler type swimming pool heater. A propane fired gas heat pump may be an opportunity for the swimming pool heating market.
In addition, it is possible with a swimming pool heating heat pump to also deliver cooling to the occupied spaces of the hotel, or residence simultaneously. Effectively, this is like running and air conditioning system and rejecting the heat to the swimming pool. To date, Robur has marketed this concept only in Europe.
The “Snowbird” Desiccant Dehumidifier Another interesting market for desiccant humidification systems is in residential preservation. In southern climates, many homeowners return to the north during the summer, and many residences are unoccupied. In hot climates, when a residence is unoccupied, the air conditioning system is left in operation. Unless the air conditioning system runs throughout the summer, humidity will build up within the home to such an extent that the carpets will mold and drywall will actually be rotted. In this situation, the residence does not actually need to be cooled. The air conditioning system is merely being used to provide dehumidification. The low indoor temperature that results throughout the summer is unnecessary and represents a waste of energy.
A small desiccant dehumidification system moving a flow of dehumidified air would be able to flush this humidity out without providing any cooling to the residence. This would be a substantial reduction in overall operating cost. The interior of the residence would remain warm throughout the summer, allowing the home to be preserved without having to be cooled. Not only would the save the energy that is currently wasted in sensible cooling but the effect in dehumidification would be more pronounced. By keeping the residence warmer throughout the
Figure 57: Electric Heat Pump Swimming Pool Heater
(Photo Courtesy of Raypak)
Figure 58: Using a Fuel Fired Heat Pump to Provide Air Conditioning and Domestic Hot Water Simultaneously
(Excess Heat is Shown Being Rejected to the Swimming Pool, but a ooling Tower Could Also be Used to Dump Excess Heat to Outdoor Air
urtesC )
(Drawing Co y of Robur)
summer, the relative humidity would tend to be lower, with the same amount of dehumidification. Since mold, drywall rot, and other damage is related to relative humidity, keeping the house warm and dry would actually be more effective in preserving indoor furnishing and drywall.
One desiccant system is currently available at the appropriate size range, the Novelaire desiccant dehumidifier. Installing the Novelaire system into a humid climate home would not only allow for a substantial energy and operating cost savings during unoccupied summer months, but would also be available for operation throughout the winter. Even in the winter in damp climates, humidity can be an issue. Using a desiccant system to remove humidity in cooler damp weather would be more effective then using the air conditioning system, as the desiccant system has no tendency to over cool the home but rather produces pure dehumidification. Overall, these two benefits together can be a powerful inducement for buying desiccant equipment.
As mentioned previously, the higher end of the residential market in Florida and other costal areas tends to be on oceanfront property, much of which is on barrier islands. In general, barrier islands do not have natural gas distribution. This means these desiccant systems would have to be driven by either propane or electric resistance heaters. As such, this could be a very cost competitive market for propane in the south.
The Remote Vacation Home One of the most interesting applications for propane-fired cooling systems could be vacation homes throughout North America that are not only remote from a natural gas distribution system but are also remote from the electric distribution system. As such, these homes have to be powered by on-site generators, or the homeowner simply deals with not having electricity.
Although there may be homeowners that feel they can get by without electricity, the higher end of this market for remote homes will have some type of on-site generator that is used to provide conveniences for least part of the day.
In addition to operating the generator, there are two areas where propane fired cooling can be used in these applications. The first is food preservation refrigeration. This is an established technology and market. Propane-fired refrigerators are often used in vacation properties, as food refrigeration is a need that is very difficult to do without. Propane refrigerators may be used in a vacation homes that may or may not have electric generators. In either case the propane refrigerator is capable of operating continuously when the generator is on or off or even when the owners have left the home for an extended period.
Operating an electric refrigerator in a home that depends entirely on a generator tends to cause problems with the generator. When the home is otherwise unoccupied, the refrigerator may be the only load on the generator. In general, the refrigerator will use less than 10% of the electric power of the home at full load, will spend much of the time cycled off, and will require a large inrush current each time the compressor starts. Not only will this add operating hours on the engine generator but the low load may be difficult for the generator to carry. An engine operating extensively on low load tends to experience excessive piston ring wear.
In higher end remote vacation properties, the homeowner will require air conditioning systems, unless the property is located in an extremely cold climate. To equip the home with electric air conditioning could require expanding the size of the on site generator extensively. Typically adding a five ton air conditioning system would require adding at least 5-7 kW to the size of the electric generator just to operate the cooling compressor, and the generator must be capable of
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handling the substantial inrush current when the cooling system starts, putting further requirements on how the generator is built.
In these remote locations, the generator as well as the refrigerator, the heating system, the cooking equipment, and other appliances are probably already running on propane. A more logical move than expanding the size of the generator may be to put in a propane fired air conditioner.
High End Homes with Unreliable Electric Supply Natural gas air conditioning systems have also been installed in homes where the local electric
system is considered unreliable. High end homes with discriminating owners who desire air conditioning systems and electric power to operate continuously can install on site generators to serve as a backup for the utility grid. Natural gas air conditioning systems have also been installed in these homes to avoid having to place the very large load of the air conditioner on to an on site generator system.
If the residence has undependable electric pit is often the due to the residence being in a fairly rural location. This being the case, the residence may not have gas service and therefore thhigh end market is also a significant opportunfor propane.
ower,
is very ity
Figure 59: Gas air conditioning system on a large high end home with back-up generation
(Photo Courtesy of Robur)
Chapter 5: Propane Opportunity in CHP with Thermally Driven Cooling Combined Heat and Power (CHP) system produced both electric power and thermal energy for an industrial plant or commercial building. An on-site generator is operated continuously or on-peak and the generator’s waste heat is used for heating and or cooling. CHP systems significantly increase the efficiency of energy utilization, up to 85%, by using thermal energy normally rejected from power generation equipment for cooling, space and water heating, and industrial process heating loads.
Figure 60 - Schematic of Energy Flows for Typical Method Power Delivery in the United States Today
(Diagram Courtesy of the Department of Energy)
Figure 61 - Schematic of Energy Flows for a CHP System
The Efficiency Advantages of Cooling, Heating, and Power By productively using the waste heat from electric generation, the overall efficiency of energy delivery to the customer can significantly improve. However, transporting this heat for long distances is expensive.
One solution is to place the generator at the customer’s facility
The operating cost advantage of CHP is that the waste heat is recovered for productive uses rather than being rejected into the environment, as would be done at a conventional power plant. If the generator is recovering heat for some heating load that would otherwise need to be heated by a gas boiler, then overall fuel consumption for the boiler will be lessened.
One convenient way to view this is to subtract the fuel no longer needed by the boiler from the larger quantity of fuel used by the generator. The remainder is the amount of fuel being used to provide electricity. The more heat recovered productively, the less fuel is used strictly for electric generation. The cost of this electric generating fuel is the “net” cost for electricity generated. This effect can be seen in Figure 62.
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Figure 62 - Cost of Electricity Graphs for Engines
Chart assumes an engine heat rate of 10,660 Btu./kWh. and a maintenance allocation of $0.011/kWh for engines of less than 2 MW. Larger engine often have lower maintenance allocations. .
As shown in Figure 62, the cost of electricity generated declines for lower temperature loads, as a greater quantity of heat can be recovered as the temperature of the load declines.
Engine-generator system efficiency also plays a role in economics as shown in Figure 63.
Figure 63: Cost of Electricity Generated On-Site WITHOUT Heat Recovery versus Engine Efficiency
Efficiency Shown is Based on the Higher Heating Value of the Fuel
Most CHP systems are located in large scale commercial, industrial or campus applications which have access to the natural gas network. Propane would be more suited for smaller rural applications remote from the natural gas network.
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Two types of propane on-site power generation applications that would be attractive are:
Remote Stand-Alone Applications not served by the electric system, where on site generation of electricity is the only potential source of power. This includes customers that cannot physically be reached by the electric distribution systems as well as customers that would be required to pay an impractical sum to have the lines extended to their facility. In this case, the customer can either use propane or diesel fuel to power an onsite generator. The choice of fuel is largely a matter of cost comparison or emission issues. The customer may or may not use the rejected heat from the generator and the use of cooling equipment that operates on the rejected heat may be attractive. However, the key element in the customers purchase process is simply their need for electricity.
Rural Applications where electric power is available but the use of a CHP type system would make economic sense either because local power is expensive, or for some site specific reason. The productive use of the rejected engine heat will be a major element in the customer’s decision making process as they have alternative sources of electricity. Unless purchased electricity is very expensive, economically competing with on-site generation usually means viewing the entire CHP system as a package, including the benefits of heat recovery. Depending on the application, heat driven cooling systems may be a critical portion of the overall package sale. Heat driven cooling technology, such as absorption or desiccant systems, may often be essential in producing positive economics
Smaller Reciprocating Engine Generating Systems Engine generators are the traditional approach for smaller power generation. The majority of the engine generator systems are sold for use strictly for emergency back-up power, an application where heat recovery and long life are not important. However, the same engines are also used for continuous power applications, by operating at reduced maximum power output to reduce wear and extend the engine life. Engine speeds are limited to 1800 rpm, also to extend life.
Although smaller engine generator sets are available from traditional suppliers such as Caterpillar, Cand Waukesha, the major market players in the large generator market, some newer suppliers have come to market focusing on small CHP applications.
ummins,
The following lines of small generators are intended for continuous duty and packaged with heat recovery from both the engine jacket and the hot exhaust. Heat is recovered as hot water.
Hess Microgen25 Hess Microgen, a subsidiary of Amerada Hess, produces a line of small generators intended for continuous duty and packaged with heat recovery.
25 Hess, 12 Industrial Parkway, Unit B-1, Carson City , NV 89706, Phone: 775-884-1000, Fax: 775-884-3417
Figure 64: Hess Microgen Small Engine CHP System
(Photo Courtesy of Hess Energy Systems)
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Coastintelligen26 CoastIntelligen manufacturers a line of cogeneration equipment, powered by reciprocating
engines, ranging from 55 kilowatts to 365 kilowatts. The heat recovery exchanger recovers both engine jacket and exhaust heat. Multiple units can be linked together. Units come in a steel cabinet designed for sound attenuation. CoastIntelligen claims 12.5 MW of capacity have been installed at 86 sites.
Tecogen27 Tecogen has been producing a line of small packaged cogeneration system for 20 years. Tecogen uses a General Motors engine that has been converted for marine operation with the addition of water cooled exhaust manifolds and more durable valve materials
for longer engine life. Also contributing to engine life is the de-rating of output to 1800 rpm for cogeneration, as well as positive valve rotators, improved coolant distribution, and increased oil flow to bearings, camshaft, and cylinder walls.
Since first introduced in 1984, more than 1100 natural gas engine-powered cogeneration, chiller, and refrigeration units have run more than 15 million hours of service at 650 customer sites. Tecogen claims that their engines normally operate for about 20,000 hours between overhauls. Tecogen produces a 60 kW, a 75 kW and a new 100kW cogeneration package complete with heat recovery equipment.
The 60 and 75 kW units use an induction generator that simplifies interconnection with an electric load that also connected in parallel to the utility. The induction generator shuts down in the event of a power outage and these units cannot be used for backup power. The new 100 kW package delivers power to a rectifier, converts the power to direct current and then inverts the power back to 60 cycle AC. This allows the engine to run at any desired speed and the unit is capable of putting out up to 125 kW for a limited number of hours per month. The 100 kW unit will also operate as a back-up generator during a blackout. The new unit is on field test in Ohio and will be available for sale in January 2007.
26 CoastIntelligen, Inc.,2460 Ash Street, Vista, CA 92083, (760) 597-9090, (760) 597-2999 (fax) 27 Tecogen, 45 First Ave., Waltham , MA 02451, Phone: 781-466-6400, Fax: 781-466-6466
Figure 65: Coastintelegen unit Installed (Photo Courtesy of Coastentegen)
Figure 66: Tecogen Packaged Cogeneration System
(Photo Courtesy of Tecogen)
Hess Microgen CoastIntellegen Tecogen Sizes (kW)
Ht Rec Gen Sizes
(kW) Heat Rec Gen Sizes
(kW) Heat Rec Gen
75 55 60
150 80 75
220 150 100
350 250IC
450 250SC
365IC
365SC
420C
420SC Under Heat Recovery
=Heat Recovery Exchangers Included =Heat Recovery Exchangers Optional =Heat Recovery Exchangers Not Available
Under Generator =Synchronous Generator =Induction Generator =Rectifier - Inverter
Table 12: Available Sizes of Small Reciprocating Engine Generators with Heat Recovery
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Microturbine Generators Mini and microturbines are the newest development in gas turbine equipment. The capacities of
microturbines range in capacities from 25 kW to 100 kW and mini turbines range from 100 kW to 1000 kW. It is not uncommon to ignore the differentiation between mini- and micro- turbines. For this course, all turbines smaller in capacity than 1MW will be referred to as microturbines.
Manufacturer Capstone Ingersoll Rand Elliot
Sizes (kW) 30 70 100
60 250
250*
*In Development
These turbines can use natural gas, propane, fuel oil, and gases produced from landfills, sewage treatment facilities, and animal waste processing plants as a primary fuel.
Figure 67: Microturbine Installation (Photo Courtesy of Capstone Mictroturbine)
Table 13: Available Microturbines on the North American Market
Microturbines evolved from automotive and truck turbochargers, auxiliary power units for airplanes, and small jet engines used on pilot-less military aircraft. Microturbines have far fewer moving parts than engine generators equipment of similar capacity. Therefore, these machines have the potential for very low maintenance costs.
Figure 68: Internal Layout of Capstone Turbine (Drawing Courtesy of Capstone Microturbine)
By using recuperators, existing microturbine systems are capable of energy efficiencies in the 25-30 percent range. These turbines have a tremendous potential for on-site power generation for CHP systems, as they can be used by smaller commercial buildings, which are far more numerous than very large commercial or industrial customers.
Microturbines are intended to be operated in parallel with grid electricity. Equipment options are available to allow microturbines to operate completely off of the grid, and heat recovery options are also available.
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Capstone Turbine28 Capstone Turbine Corporation is a producer of low-emission microturbine systems, and was the first to market a microturbine product. Capstone Turbine has shipped more than 3,500 systems to customers worldwide. Systems have logged more than 12 million documented runtime operating hours. Capstone Turbine is headquartered in the Los Angeles area with sales and/or service centers in New York, Mexico City, Milan, Shanghai and Tokyo
Ingersoll Rand29 Ingersoll Rand is a diversified multi-national manufacturer of industrial and commercial
equipment. Ingersoll Rand, in mid-2000, formed Ingersoll Rand Energy Systems to manufacture microturbines. The first field test units into operation in mid-2000.
In 2001, manufacturing production capability for the 70kw induction unit was completed and engineering development of the 250kW began. 2002 began with shipments of the first commercial
induction 70kW microturbine. Energy Systems also shipped its first microturbines for use with low Btu fuels such as those found in landfills and wastewater treatment plants.
In 2003, development of the MT250 was completed and commercial manufacturing production commenced. These currently offered microturbines include fuel conditioning, maintenance and financing.
28 21211 Nordhoff St., Chatsworth , CA 91311, Phone: 866-4-CAPSTONE, Fax: 818-734-5320 29 Ingersoll Rand, 800A Beaty Street, Davidson, NC 28036
Figure 69: Ingersoll Rand 250 kW Microturbine (Photo Courtesy of Ingersoll Rand)
Figure 71: Package Layout of Elliot Microturbine (Drawing Courtesy of Elliott Energy Systems)
Figure 70: Elliot Microturbines Under Test (Picture Courtesy of Elliott Energy Systems)
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Elliott Microturbine30 Elliott Energy Systems, Inc. is a manufacturer of Microturbines for use in distributed generation, combined heat and power (CHP), biogas and offshore applications. This 100 kW Microturbine package includes heat recovery heat exchangers and can be mounted outdoors. Like the Capstone turbine, the generator operates at high speed and the power output is electronically rectified to direct current and then inverted to 60 cycle AC. However, unlike the Capstone turbine, the Elliott turbine does use oil filled bearing which may increase maintenance. Elliott Energy Systems, Inc. is a fully owned subsidiary company of Ebara Corporation of Tokyo, Japan.
The TA100 CHP Microturbine CHP system is capable of producing 100kW of electrical energy and 172kW of thermal power per hour. Cogeneration usage can consist of hot water, absorption chiller or drying system applications. Depending upon the user application, overall total thermal efficiency could be greater than 75%. Ebara, the parent company of Elliott Energy is a major Japanese manufacturer of absorption chiller systems.
Small Generator Summary
Manufacturer Type Possible Type of Cooling
lbs /kW
$ / kW w/o
Instal3,4
Form of Recover.
Heat
Recover Heat Temp
Off Grid Oper.
LP Ready
Can Be Set Out-
doors
Heat Recov Incl?
Hess Microgen Engine Single Effect
Bromide Hot Water NA
Coast-Intelligen Engine
Single Effect
Bromide $1,250-
$500 Hot Water 194°F
Tecogen Engine Single Effect
Bromide $800-
8502 Hot Water 230°F 1
Capstone Micro Turbine
Single Effect
Bromide or Aqua
Ammonia
$1,000 Hot Water or Exhaust 200°F
Ingersoll Rand Micro Turbine
Single Effect
Bromide $1,000 Hot Water 200°F
Elliott Micro Turbine
Single Effect
Bromide $1,000 Hot Water 200°F
= Included with System = Extra Cost Option = Not Available at Present 1New 100 kW Tecogen System Capable of Off Grid Operation 2Cost for New 100 kW Tecogen System $1100/kW 3Range Prices are from Low End to High End of the Size Ranges Respectively 4Cost for Installation and Interconnection with Electrical and Hot Water System Tends to Equal Equipment Cost
Table 14: Small Engines and Microturbines
30Elliott Energy Systems, Inc., 2901 S.E. Monroe St., Stuart, FL 34997 USA, Tel:772-219-9449, Fax:772-219-9448, Website: www.elliottmicroturbines.com
Application of Thermally Driven Cooling to On-Site Generation Small CHP generation equipment is installed in two different ways, as an “Applied” system or as a “Packaged” system.
Applied Systems Applied systems are custom designed for a specific application. Heat is recovered from the cogeneration system as hot water or steam. This hot water or steam is then distributed through the facility to meet any local needs for heat such as space heating or potable water heating. The thermally driven cooling equipment is installed wherever convenient and driven on the same hot water or steam distribution system. Applied systems are usually used in larger commercial buildings, hospitals, schools and university campuses, and industrial applications. Although
usually used for larger applications than may be of interest to the propane industry, applied systems have been used in small applications.
Figure 72: Schematic of an Applied CHP System with Absorption Cooling
Figure 73: A Small Applied CHP/Cooling System Using an Absorption Chiller
(Photo Courtesy of NiSource Energy)
One positive aspect of applied systems is that thermally activated cooling systems are widely available to work it in these applications. The major brands of absorption chillers are all constructed to operate on either steam or hot water.
Unfortunately, in smaller cogeneration systems, the applied approach requires a great deal of custom design and piping, which adds to the cost of the system.
Packaged Systems The other type of application is a package system. In a packaged system, the thermally driven cooling equipment is: located with or near the generator. The generator and cooling equipment operate together in some manner that simplifies the overall complexity the system components and installation. Generally packaged systems have been targeted to smaller size applications.
One way to simplify cooling operation is to duct the exhaust from the on site generator directly into the cooling system. This eliminates the need for a steam or hot water loop between the generator and the cooling system. This approach has been used on microturbine systems. With microturbines, all of the rejected heat from the turbine generator is rejected into a hot exhaust.
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This ducted exhaust approach is less suited to engine generators where only a portion of the engine generator waste heat emerges in the exhaust.
Figure 74: Carrier PureComfort System - Packaged multiunit microturbine system directly firing and exhaust driven
absorption chiller (Photo Courtesy of Carrier Corp.)
Custom lithium bromide absorption chillers are now available to operate directly on the exhaust from a microturbine. One system has recently been commercialized for use in smaller applications. In this system, shown in Figure 74, uses a number of microturbines to drive a single lithium bromide absorption chiller.
In addition, one ammonia water chiller is currently under test operating on microturbine exhaust as shown in . More test sites for this system are being planned. One advantage of tapproach is that the ammonia water systems are air cooled, and requires no open cooling towewhich is required by a lithium bromide absorpsystem.
Figure 75his
r tion
Figure 75: Single 30 kW Microturbine with Exhaust Driving a 5 Ton Ammonia Water Absorption Chiller
(Photo Courtesy of Cooling Technologies)
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An Economic Overview of CHP on Propane Using established techniques, and state-by-state average propane and electric prices, an overview of how reasonable propane is as a fuel for CHP systems in general can be developed.
Figure 76: On-Site Generation with Propane versus Buying Electricity from the grid.31
Figure 76 shows that the cost of using propane to generate electricity from a simple generator with or without heat recovery. Without recovering heat, the cost of the electricity generated is quite high, ranging from $0.14 to $0.28 per kilowatt hour across the price range of propane. However, more realistic electric generation costs can be reached depending on the level of heat recovery that achieved in a combined heat and power system.
31 Chart assumes a 30% generator efficiency against the higher heating value of propane
For cogeneration systems that are competing directly with electric power from the grid, the cost of electric generation usually has to be well below that which can be purchased from the grid to justify the cost of the cogeneration equipment. Looking at the cost of using propane in such a system, it is clear that equaling the cost of grid power in most situations is the best that can be hoped for with current electric prices.
Widespread use of propane for cogeneration systems does not seem to pose a major market opportunity. However, in areas remote from the grid where power is needed, cost for electric power from a propane fired cogeneration system can be significantly more reasonable than costs from a generator without heat recovery and the cost of the cogeneration equipment itself may be less expensive than long distances of power lines for a single customer.
In such a situation, it is generally more practical for the customer to use recovered heat to operate cooling systems than to add more generators for electric cooling. If there is not enough recoverable heat to meet all loads including the cooling load, it is still often more practical to install a fuel fired cooling system than an electric cooling system plus added generation.
Although outside the scope of this report, another potential propane market is also posed by Figure 76. With electric deregulation, some larger electric users have switched to floating or real time pricing for their electric supply. Average electric costs on real time rates are generally lower than with other rate structures but the customer bears the risk of very volatile high prices during periods of peak demand, when prices above $0.30/kWh are not uncommon.
Customers may be covering their risk by operating back-up generators during these high cost periods. However, extensive operation on diesel fuel is not only expensive but may conflict with emission regulations. Propane would be a cleaner fuel for those customers if they are not in an area where natural gas is available.
Finally, the desire for propane fired CHP in a remote application may be based more on the need for dependable power in remote areas or the lack of a nearby grid electric connection than any economic factors.
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Appendix: Available State and Federal Incentives32
32 http://www.epa.gov/CHP/funding_opps-chp3.htm
Alaska Power Project Loan Fund Loan AKAgriculture Energy Efficiency Program Grant ALCA - Energy Innovations Small Grant Program (EISG) Grant CACA Loans for Energy Efficiency Projects Loan CACA Self-Generation Incentive Program (SGIP) Rebate CACT Long-term Loans for Customer-side DG Loan CTConnecticut New Energy Technology Program Grant CTConnecticut RPS - Class III Resources Environmental
Regulations CTConnecticut Grants for Customer-Side DG Grant CTOperational Demonstration Program Loan CTOnsite Renewable Distributed Generation Program Grant CTConnecticut Property Tax Exemption Tax CTIdaho Renewable Energy Generation Benefit Grant IDIdaho Renewable Energy Equip. Sales Tax Refund Tax IDIdaho Low Interest Energy Loans Loan IDIL Clean Energy Community Foundation Grants Grant, Loan ILIN Alternative Power and Energy Grant Program Grant ININ NOx Budget Trading Program Energy Efficiency Grant INKansas State Energy Program Grants Grant KSMA NOx Budget Trading Program Energy Efficiency Environmental
Regulations MABusiness Activity Credit Tax MIAlternative Energy Property Tax Exemption Tax MIMN Renewable Development Grants Grant MNMississippi Energy Investment Program Loan MSNC Renewable Energy Tax Credit Tax NCNC Energy Improvement Loan Program Loan NCNE - Renewable Energy Tax Credit Tax NENM Industrial Revenue Bond (IRB) Financing Loan NMNM Public Facility Energy Efficiency Loan Loan NMNY CHP Performance - PON 984 Grant NYNY NOx Budget Trading Program Energy Efficiency Grant NYNYSERDA Technical Assistance Opportunity Notice Grant NYConversion Facilities Property Tax Exemption Tax OHOH Distributed Energy Grant and Loan Program Grant, Loan OHOR Small Scale Energy Loan Program (SELP) Loan OROregon Business Energy Tax Credit Tax ORPA Small Business Energy Efficiency Grants Grant PASouth Carolina ConserFund Loan Program Loan SCTennessee Small Business Energy Loan Program Loan TNVT - Clean Energy Development Fund (CEDF) Grant VTWI Renewable Energy Development Program Grant WIWisconsin Focus on Energy Implementation Grant Grant WIQualifying Gasification Project Credit - Sec 48B Tax NationalClean Renewable Energy Bond Program Tax NationalRenewable Electricity Prod. Incentive, Sec-202 Tax NationalInventions and Innovation Program (I&I) Grant NationalInnovative Technologies Federal Loan Program Loan NationalCredit for Fuel Cells and Microturbines - Sec 1336 Tax NationalAdv Power System Tech Program - Sec 1224 Rebate National
Chapter 6: Economic Analysis of Propane Fired Air Conditioning This chapter describes an economic analysis on the potential national market for propane fired air conditioning concepts. As such, the data used is based on state average costs as this is the only way to get an overall picture of the situation. Propane prices vary within a single state.
Looking at average prices will also mask specific opportunities that result from electric tariffs in a specific region. Unfortunately, electric tariffs can be very complex, each local utility can have a dozen or more tariffs and there are literally hundreds of utility regions across the United States. Electric prices tend to be highly variable across some states. For example, the average residential electric price in New York State is noted as slightly under $0.16/kWh. This averages the very high prices for electricity in the New York City area with lower prices in upstate New York.
The Economic Situation Although operating costs and payback economics are not the only issues involved in marketing propane fired cooling systems, the issue of operating costs will be important. Two situations exist when it comes to the relationship between a customer’s decision and operating costs
1. In a case where a propane technology and an electric technology can provide exactly the same benefit to the consumer, an analysis of operating and first cost differences will reveal much about the consumer’s eventual decision. An example of this would be a consumer’s decision between a propane furnace and electric resistance heat. In most cases, the heating would be equivalent in comfort, but the operating cost for electric resistance heat would be so high that the extra first cost for the propane furnace is no barrier to the market.
2. In a case where the propane technology produces a benefit that is not available from the electric technology, the operating and first cost differences reveal how much the consumer is paying for the added benefit. An example of this would be the competition between electric and propane water heating. The low capacity of the electric water heater makes the higher cost of the propane water heater a reasonable tradeoff for the customer even if operating costs were equivalent.
The current position of propane versus electricity on a state-by-state basis is shown in Figure 77. This can be very useful chart as any propane versus electric competitive situation can be presented on this chart.
However, although the chart allows for a view of the entire propane versus electric market to be seen, all the prices shown are state averages. These averages are weighted by volume. For both propane and electricity, the values were derived by determining the amount of money spent for propane or electricity in total and that value was divided by the overall statewide consumption. This means that the averages tend to be weighted toward those periods when the fuel is being consumed. For example, the winter propane price affects the average to a greater extent than the summer price as the volume consumed in the winter is greater.
Residential average prices are shown on
Figure 77. Residential rates were used throughout these economic evaluations. The target markets for all of this equipment are in smaller applications such as single family residences and small free standing commercial buildings. Commercial rate averages tend, due to the averaging process, to be skewed to the consumption of larger commercial customers, and with
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electric prices, the difference between small and large commercial customer rates tends to be larger than the difference between residential and small commercial rates.
Finally, the use of average electric prices can miss opportunities having to do with demand charges. When dealing with cooling equipment in particular, demand charges can have a significant effect as cooling equipment operation tends to peak up the maximum demand of commercial buildings in the summer. By using average costs, the demand charges being paid by the average customer are included, but they are folded in to the overall costs that the customers in each state are incurring for electric energy, electric demand, and all other utility charges, divided by the total electric usage. Therefore, although the cost of demand charges is included in the average, opportunities that target specific rate schedules by shaving peak demand, such as some fuel fired cooling opportunities are not called out.
Notice that the markets covered by this report are residential and small commercial buildings. Residential customers are rarely covered by demand charges, as the cost of demand metering is generally too high to be justified on residential loads. Depending on the utility area or the specific rate structure chosen by the customer, the majority of light commercial customers will also not be on demand charges for the same reason. Most residential and light commercial customers generally pay a simple energy charge and have inexpensive energy use electric meters. Demand charges do become very common for large commercial customers, but those cooling loads exceed the capacities of the equipment we are studying here.
Using the Economics Charts Keeping these limitations in mind, the chart can still be very useful in seeing the overall position of propane by technology.
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Figure 77: Average Current average price of propane versus electricity by State33,34
33 Electric prices from: Energy Information Administration, State Energy Data System, Table 5.6.A. Average Retail Price of Electricity to Ultimate Customers by End-Use Sector, by State, March 2006 and 2005, http://www.eia.doe.gov/cneaf/electricity /epm/epmxlfile5_6_a.xls 34 Propane Prices from Energy Information Administration, State Energy Data System, Table F6: Liquefied Petroleum Gases Consumption, Price, and Expenditure Estimates by Sector, 2004, http://www.eia.doe.gov/emeu/states/_seds_updates.html
The economics of various technologies can then be plotted on these charts. As a simple example to show how this works, Figure 78 shows a “Cost Equivalence” line between a propane furnace and electric resistance heating. Each point on this line is where the propane and electric price would need to be for the operating cost of the two systems to be equal. For example, if propane were $2.00/gallon, the customers heating cost would be such that electric resistance heating could only achieve the same cost if electricity were roughly $0.09/kWh.
Figure 78: Propane/Electric Chart with Technology Line for Electric Resistance Heating Versus a 78% Efficient Propane Furnace
(Only those states with very low electric prices are below this line. Propane heating is in a very challenging market in those states, located in the southeast and the northwest.)
The average electric cost for the states shown above the line in Figure 78 is HIGHER. Therefore, in any state above the line, propane heat is less expensive to operate than electric resistance heat. For all of the following charts, propane will be at an operating cost advantage in any state ABOVE the lines shown.
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Economic Analysis of Cooling and Heat Pump Systems The following economic analysis depends on a number of assumptions. In each case, the propane cooling or heat pumping system is compared to a certain type of conventional system:
The conventional air conditioner is a 13 SEER system, meaning that on a seasonal basis, the air conditioner will produce 13,000 Btu/Hour of cooling (a little over 1 ton) for every kilowatt of electricity consumed.
For heat pump systems, the assumptions about the size of heating and cooling loads in the same building and the duration of the cooling season are important and alter the economics. Therefore, three climates were used
Climate Type Cooling Season
Heating Season
Heating/Cooling Capacity Archetypical City
Cold Climate 600 EFLH 800 EFLH 100 MBH/5RT Minneapolis
Mild Climate 900 EFLH 660 EFLH 80 MBH/5RT Omaha
Hot Climate 1800 EFLH 200 EFLH 60MBH/5RT Phoenix
EFLH = Equivalent Full Load Hours Heating /Cooling Ratio - Size of Equipment Assumed in Economics
Table 15: Cooling Seasons Assumed for the Heat Pump Analysis
Figure 79: US Climate Zones35
35 Energy Information Agency, Department of Energy
Propane Air Conditioning in a Conventional Application The next issue to be handled is developing the same cost equivalency charts for propane fired cooling systems. Unlike typical propane furnaces, propane fired cooling systems can have a wide variation in coefficients of performance, ranging from 0.6 for some of the ammonia/water absorption systems to 1.2 for engine driven cooling systems. In this case, a family of lines will be developed showing the “Operating Cost Equivalence” between these propane fired air conditioning system and a 13 SEER electric air conditioner. 13 SEER is the current minimum efficiency allowed to be sold into the residential market under Federal regulations. Commercial systems are not governed by these regulations, commercial systems are traditionally lower in efficiency, and a SEER of 10 has been used for commercial comparisons
The Cost Equivalence lines for propane fired air conditioning versus electric air conditioning are shown Figure 80. Clearly, whether the air conditioner is at a COP of 0.6 or a much higher value, propane firing cannot compete on an operating cost basis with electric air conditioning at current electric rates and propane prices. This indicates that propane fired air conditioning systems cannot be a mass market product competing with electric air conditioning on a head-to-head basis. This does not mean that there is not a specific submarket for propane fired cooling.
For propane fired cooling to be accepted by customers, there will have to be:
• some secondary benefit that makes the propane AC desirable enough to overcome the operating cost difference or
• a non-standard application that counteracts the operating cost difference.
One note of caution on the results shown in Figure 80. In some areas, with customers that are facing high demand charges, the effective electric rate for power consumed by the cooling system may be substantially higher than the state averages shown. Therefore, if the smaller cooling systems described in this report were applied in large numbers to a larger commercial building which pays a demand charge, the economics may be more positive than what is being shown in Figure 80. However, larger customers in this situation would find that using a large centralized engine driven or absorption chiller would provide the same or better annual savings, while involving a lower first cost premium for the non-electric system than large number of small absorption or engine driven systems.
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Figure 80: Cost Equivalency Lines for Propane Fired Air Conditioning vs. a 13 SEER Electric Air Conditioner (Efficiency Measure “COP” of Current Small Gas Fired Air Conditioners is 0.6 to 1.2. Unfortunately, at Current
Propane and Electric Prices, the Efficiency of Current Gas Fired AC Systems is Insufficient to Achieve Even Equal Operating Costs Much Less a Reasonable Payback. This Chart Does Not Apply to Heat Pumps)
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Propane Fired Heat Pumps One approach to this operating cost challenge is to focus not on pure air conditioning but on a propane fired heat pumps. This will provide another avenue of economic savings to the customer, namely reduced heating costs. Figure 81 thru Figure 83 show the Operating Cost Equivalences curves for a propane fired heat pump operating in cold, mild, or hot climate areas. The conventional system used for these curves is a 78% efficient propane furnace and a 13 SEER electric air conditioner.
Figure 81: Two Cost Equivalency Lines for Propane Fired Heat Pump Vs. a Propane Furnace and 13 SEER Electric Air Conditioner in Cold Climate States.
(The Economics in Colder Climates are Attractive for Engine Heat Pump Systems as the Equivalent Operating Cost Lines are Substantially Lower than the Propane/Electric Points for Cold Climate States. This means there are
Positive Savings on Which to Base a Payback. Absorption Heat Pumps Barely Breakeven for Cold Climate States).
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As can be seen from the figures, the economics in colder climates can be reasonable at current propane and electric prices provided the efficiency of the system is quite high. The efficiencies used in these charts were type of about the best that could be achieved with an engine driven heat pump system and are substantially higher that can be expected of an ammonia/water absorption system
Figure 82: Two Cost Equivalency Lines for Propane Fired Heat Pump vs. a Propane Furnace and 13 SEER Electric Air
Conditioner in a Mild Climate (Even at High Cooling COP’s Typical of an Engine Driven Heat Pump, the Cost Equivalency Curves Show that Operating Costs are Roughly Equal in Mild Climate States and Therefore there is Little Opportunity for Payback)
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Figure 83: Two Cost Equivalency Lines for Propane Fired Heat Pump vs. a Propane Furnace and 13 SEER Electric Air Conditioner in Hot Climate States
(Even at High Cooling COP’s Typical of an Engine Driven Heat Pump, the Cost Equivalency Curves Show that Operating Costs are Negative in Hot Climate States and There is No Opportunity for Payback)
The message in these charts is clear, the heat pump saves the customer money in heating season and losses money in the cooling season. In colder climates, the overall economics are comparable or better than those of the conventional system as the heating season comes to dominate the economics. As the climate becomes hotter, the economics become worse.
The propane fired heat pump concept saves the customer the most money in colder climates dominated by the heating load. Unfortunately, much of that savings comes at the expense of reduced winter propane load as the heating function, previously done by a propane furnace is
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now being carried out by the propane fired heat pump at substantial higher efficiency. Overall, the effect is to minimize any annual increase in propane load and to spread the load over more months of the year. Therefore, there is not a strong load building argument for the propane industry to promote this equipment unless there a market issue where the propane industry is convinced that most of these new heat pump installation will be replacing all electric cooling and heating systems. In colder climates, all electric resistance heat is uncommon on single family detached homes and electric heat pumps are generally neither efficient nor commonly used. Therefore, a new propane fired heat pump for residential applications in colder climates will generally be competing with a propane furnace and a gas air conditioner, as modeled in the economics calculations.
Given the low cost equivalence lines in Figure 81 for colder climates, the payback situation was explored. It should be expected that the installed cost for an engine heat pump is going to be higher than for a conventional propane furnace and electric air conditioner. However, as the equipment for this market is in development or only currently available from overseas sources, the actual cost of the equipment should be viewed as uncertain. If the decision is made to import equipment, costs will be subject to negotiated terms. With systems in development like the GEDAC system, a market price for the equipment involves setting targets and understanding what will be practical and technically achievable. Therefore, instead of using an arbitrary or development target number for the first cost, it is more practical to map the payback situation. In this way, the number of states or the regions of the country where a heat pump at a certain first cost premium makes sense can be quickly plotted.
From the Payback Map Shown in Figure 84, a Propane Fired Engine Heat Pump with the COP’s Shown will have the Best Introductory Market in the New England States, even if the Cost Premium is in the $700 per ton Range.
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Figure 84: Cold Climate Heat Pump Application Payback Map
The Economics Map Shows the Opportunity for a 5 Year Payback for Any Technology Capable of Delivering the COP’s Shown. Any Proposed Heat Pump System Can Quickly be Plotted. The Map Does Not Assume Any Specific
Technology. Changing Propane Prices will Change the Position of the States but Will Not Affect the Lines Shown.
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The Commercial Rooftop Market for a Propane Heat Pump There is one large market segment where a propane heat pump would be competing largely with all electric systems, even in northern climates. This is in commercial rooftop systems. Although commercial rooftops heating and cooling units are available with gas heat, propane heat, and heat pumping arrangements for space heating, the majority of these systems, whether for use in cold or warm climates, have traditionally been installed with electric resistance heat. In addition, the air conditioning systems have remained fairly inefficient, with SEER’s below 10 as commercial systems are not governed under federal efficiency standards.
Alternatives to electric resistance heat is either a rooftop system with a propane fired “gaspac” which is essentially a propane furnace packaged in with the rooftop unit, or an all electric rooftop heat pump.
Unit Type Heating Type Unit Cost Installation Total Installed
Cost
10 Ton Electric Rooftop Unit Electric Resistance Heat $5,400 $700 $6,100
10 Ton Electric Rooftop Propane Heating $5,800 $700 $6,500
10 Ton Elect HP Rooftop Heat Pump $6,250 $700 $6,950
10 Ton Propane Driven GEDAC Unit Heat Pump $12,000 $700 $12,700
Economics of a Commercial Heat Pump
Figure 85: Cost Equivalency Lines for Propane Fired Heat Pump vs. Resistance Heat and a 10 SEER Electric Air Conditioner in Hot, Warm and Cold Climates
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Figure 85 shows the economic comparison between a 10 SEER air conditioning rooftop unit with resistance heat versus a propane fired engine heat pump rooftop unit of the type being developed by GEDAC. As can be seen, most of the states show a positive savings. However, one point of caution should be mentioned. Electric resistance rooftop heat is used on commercial application due to the low first cost of the unit and the ease of installation as no fuel line needs to be run to the roof. Propane fired heating sections for otherwise conventional systems already exist that can provide much of the savings shown in Figure 85.
The cost equivalency lines in Figure 85 show that there is substantial savings with the heat pump rooftop and that these savings do not vary greatly with climate. This is one technology that should be justified even in hotter climates. In these hotter climates, all electric rooftops dominate the market and therefore this may be the best competitive location. For this reason, the economics comparison shown in Figure 76 is for hot climate states.
Figure 86: 3 Year Payback Lines at Various Cost Premiums for a Comparison between a Gas Engine Heat Pump and an
Electric Resistance Heating/Electric Cooling Rooftop The Economic Map Shown Assumes that the Competitive Equipment is a Commercial Rooftop with Electric Resistance Heat and the High Allowable Cost Premiums are Largely the Effect of the High Cost of Running
Resistance Heat. This Map is Useful Because Electric Resistance Heat is Common in Rooftop Units in Hot States.
Competing a GEDAC type heat pump with a rooftop air conditioner equipped with a propane heating section is more economically challenging for the GEDAC heat pump. The economics of the conventional rooftop system with propane heating are substantially better than with resistance heating. This economic comparison is shown in Figure 87. For this comparison, the conventional system was assumed to be a 78% efficient propane furnace section and a 10 SEER air conditioning system.
As can be seen in Figure 87, the economics against a rooftop with propane fired heating are difficult with a clear 5 year payback occurring only in colder climates. Once again, the savings in the heating season are being balanced against higher operating costs in the cooling season resulting in better economics in colder climates.
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Figure 87: 5 Year Payback Lines at Various Cost Premiums for a Comparison between a Engine Heat Pump and an
Propane Heating/Electric Cooling Rooftop The ranges shown represent a span of from $500 to $700 a ton in first cost premium for the Propane Fired Engine
Heat Pump. Notice that a 5 year payback is achieved only in colder climates
The GEDAC type heat pump was also compared against electric heat pumps. This comparison is shown in Figure 88. The following efficiencies were used for the electric heat pump: a 10 SEER for cooling in all climates, and a seasonal heating COP of 3.0, 2.0, and 1.5 in hot, mild and cold climates respectively. Once this comparison was plotted for 5 year paybacks, the economics in colder climates was found to be sufficiently positive that the three year payback area was also plotted.
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Figure 88: Payback Lines at Various Cost Premiums for a Comparison between a Engine Heat Pump and an Electric Heat
Pump Rooftop The ranges shown represent a span of from $500 to $700 a ton in first cost premium for the Propane Fired Engine
Heat Pump. Notice that the competitive situation in the North is sufficiently positive that Three Year payback results are also shown.
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Business Issues in the Commercial Rooftop Market The commercial rooftop market is a very first cost sensitive market. Low efficiency equipment has dominated this market by being the lowest cost equipment available. Rooftop units are mainly used in commercial rental property, such as strip malls and convenience stores. In commercial rental situations, the owners will demand lowest cost equipment and the lease will specify that the tenant pays electricity and fuel bills. Therefore, there is no financial inducement for the owner to buy anything but the lowest first cost, most inefficient cooling system available.
With fast food restaurants the ownership of the building will generally be the owner or franchisee of the restaurant. In this case, the addition of a money saving heat pump system would pass saving directly back to the owner’s bottom line. For this reason, the fast food restaurant market may be an opportunity.
Convenience stores are generally owned by the chain with a franchised “operator” who participates in the profits. Strip mall are often all leased. In both cases, the renter or operator is not in a position to participate in building equipment decisions. To use higher priced equipment on these facilities, the decision maker, generally the building owner or the chain organization, must be approached and sold on the acceptability to their organization of the equipment. In addition, some or all of the operating cost savings must return to the decision maker.
In general, the retrofit market, that is customers who have existing facilities with deteriorated HVAC equipment in need of replacement, may be the best market, as they have a baseline of information on what their energy cost have been. If, in addition, they both own their building and pay their own energy bills, they are in a position of control to make the decision to go to a higher cost HVAC system.
All of these markets will also be highly payback sensitive. For example, a typical successful fast food restaurant or convenience store should have an overall payback on the entire operation in the range of 3 years or less. If propane fired cooling or heat pumping equipment has a longer payback than this, the owner would be better served by retaining his available capital with a focus on investing in further restaurant or store properties. The overall payback in rental property may be somewhat longer.
Finally, there is the tax situation. A propane fired air conditioner or heat pump becomes a normal part of the equipment of a building which has a very long depreciation period for the owner occupant of the building, generally on the order or 20-30 years. Conversely, all of the equipment used in the processes of the business itself, for example all the cooking and counter equipment, and all of the furnishings within a restaurant, are process equipment and can be depreciated for tax purposes in 5 years or less. This also puts an investment in a higher first cost air conditioning system at a disadvantage.
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Third Party or Propane Dealer Financing The economics indicate that although propane fired air conditioning would be a load building sale for propane dealers, the economics for the customer are not persuasive. The customer economics on a propane fired heat pump are much better, but load building argument to the dealer is not as positive.
One way for both the dealer and the customer to participate in the economic savings is a program of dealer financing of the heat pump equipment. In this way, the dealer participates in the customer’s savings by collecting on equipment financing as well as the sale of the propane commodity itself. This was a common practice in the early natural gas industry, but was largely ruled out by regulatory policy over the last 20 years. Propane dealers, being unregulated, should not face this objection. In addition and unlike regulated gas companies, propane dealers may be in competition for propane customers, and lease or financing arrangements can be used as “tying agreements” requiring a customer to stay with the same supplier for the life of the financing.
Year 1 Thru 5 6 Thru 10
Electric Rooftop System
Electric Usage 155,268 155,268
Electric Price $0.08 $0.08
Operating Cost $12,421 $12,421
Amortized Loan for Equip $1,490 $1,490
Total Annual Payment $13,912 $13,912 Heat Pump Customer
Heat Propane Use (Gal/Yr) 378 378
Cool Propane Use (Gal/Yr) 2835 2835
Annual Heating Cooling Cost $4,820 $4,820
Annual Payment $4,981 $4,981
Propane Cost $1.50 $1.50
Total Annual Payment $9,801 $9,801
Heat Pump Customer Savings $4,111 $4,111 Income to Propane Supplier
Propane Sales HP Customer 3213 4498
Propane Sale Elect HP Customer 0 0
Margin on Propane at $0.2/Gal $643 $643
Loan Payments Received $4,981 $4,981
Annual Maintenance $500 $500
Depreciation $5,000 $0
Assumed Marginal Tax Rate 40% 40%
Tax Savings $2,200 $200
Total Return $7,324 $5,324
IRR of Investment 24%
Table 16: Spreadsheet Calculation for Propane Dealer Financing of an Engine Heat Pump Rooftop System
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Finally, depending on the legal structure or the arrangement, the equipment may be depreciated for tax purposes by the dealer rather than the customer. As it is serving a structure not owned by the dealer, it may be classified as “rental equipment” allowing the dealer to depreciate the equipment for tax purposes in as little as 5 years. As mentioned before, the commercial building owner would have a longer depreciation period and a residential customer world have no depreciation option at all.
The Third Part Financing Proposition The financing option outlined in Table 16 poses the following proposition to a customer constructing a new small commercial building in need of 15 tons of cooing and roughly 180 MBH of heating in a hot climate. If the customer decides, as many are currently doing, to put in a all electric rooftop unit, the customer must pay $8-10,000 for the unit installed as part of the construction process. In operation, the unit will consume roughly 155,000 kWh per year which at an $0.08/kWh charge amounts to an operating cost of $12,400 per year. Notice from Figure 76 that $0.08/kWh is about as low as electric prices go in hot climate states.
Alternately, a propane dealer has decided to finance purchase and installation of engine heat pump rooftop units with a COP in cooling of 1.2 and a COP in heating of 1.4. The dealers overall cost during construction is suggested at $25,000 for both the unit and rooftop installation. The customer is installing all of the interior ductwork as part of the buildings construction process so the propane dealer is financing only the unit and its installation.
This arrangement provides the customer with the following proposition. The customer pays nothing up-front for the rooftop unit, and the operating cost per year is $9,800 an operating cost savings of $2,600 with no initial capital outlay. In addition, the customer is conserving capital outlay at just the moment it is most needed; during the construction of a new business.
The dealer is now selling over 3,200 gallons of propane per year to the customer that would have otherwise owned an all-electric building and is collected an added $4,981 per year in lease payments. As the dealer has also retained title to the unit, the dealer receives all of the depreciation tax credits. Even with the dealer supplying $500 per year in maintenance for oil and spark plug changes, and other system checks, the dealer’s rate of return over a 10 year period on their initial $25,000 investment is 24%.
One issue with lease options is referred to as “recourse”. A lease is more valuable if there is some recourse for the leaseholder should the lessee decides not to pay. In this case, the dealer always has the option of withholding propane but this could be supplied by another. However, by holding onto title to the unit, and because the leaseholders property is entirely located on the rooftop, the leaseholder could retain the right to remove the unit in the event of failure to pay. This would require, in most cases, only the crane that was used to set the unit on the building initially. This option would also be available if the business occupying the building fails.
Notice that the leaseholder is only obligated to supply and service a working rooftop unit. There is no need for this to be a new unit and the leaseholder/dealer would be free to transfer repossessed units to another customer.
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Economic Analysis on Desiccant Systems Desiccant systems present some challenges in economic analysis that have to be considered. Desiccant dehumidification systems are used to improve indoor comfort by providing improved humidity control. In the larger sense, improving indoor comfort is the role of all heating and cooling equipment, and there is no question, for example, that having air conditioning is more expensive than living without air conditioning. Clearly customers do buy improved comfort. However, desiccant systems are not necessarily the only way to improve comfort. The economics of a desiccant system need to be evaluated on an “equal comfort basis”, in which a conventional system is modified, if possible, to provide the same comfort as the desiccant system. Therefore, the conventional systems will also be as adapted to provide this level of comfort.
The addition of a desiccant system will not replace but can reduce the amount of conventional air conditioning required. The first cost comparison between conventional and desiccant systems must account for this potential first cost savings.
Table 17: Comparison of Tons of Cooling Required to Meet a Specific Indoor Condition in a Humid Climate36,37
This comparison was done for the SEMCO Revolution which can act as a dedicated outdoor air system (DOAS) or as a full cooling system with enhanced dehumidification
Table 17 is a calculation done by a manufacturer. The chart gives some indication of how a desiccant system will actually reduce the size of a larger conventional cooling system.
To look at specific operating costs in more detail, simulation results confirmed by actual field test data will be used. This field test used a desiccant system to dehumidify 9.700 cfm of 100% outdoor ventilation air to a movie theater in Plano Texas, as shown in Table 18. In that test system, the SEMCO Revolution supplied dehumidified outdoor air and was not otherwise part of the indoor cooling system.
36 Note 1: Supply humidity shown is the condition necessary to maintain the occupied space, at 75oF and 50% RH, assuming outdoor air at 85oF/130 grains, and lighting as per 90.1. Note 2: Tons required compares the Revolution with a conventional system sized to cool the air to reach the desired dew point. Note 3: Revolution is either applied as a dedicated outdoor air system(DOAS) or as a total conditioning unit, processing both outdoor and return air. 37 From:: Integrated Active Desiccant –Vapor Compression Hybrid Rooftop with CHP Capability, John Fischer, SEMCO Inc. December 13, 2005
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Setpoint Case Hours per
Year Over 60% RH All
Total End Use Energy Use (kWh/yr)
Total Propane Use (therms/yr)
Conventional AC 71°F 4,468 176,142 Condenser Reheat 75°F/55% RH 70 259,576 SEMCO Revolution 75°F / 59% RH 186 204,502 3,311
Table 18: Comparison Between Using a Conventional Cooling System, a Electric Cooling System with Reheat Capability
and a Desiccant System to Supply 9,700 cfm of Outside Air to a Movie Theater in Plano Texas38. The Conventional AC system uses the least energy but produces an uncomfortably humid indoor condition, inclined to encourage the growth of mold and mildew, for 4,468 hours of the year. Only by aggressively using reheat can a
conventional unit match the comfort level delivered by the desiccant system
From an operating cost point of view, these values can be used as a rule of thumb for the cost of delivering 1,000 cfm of outdoor air in a humid climate. The following values will be used to examine economics on an equal comfort basis.
Electric Use Propane Use Condenser Reheat 25,000 kWh/Yr 0 Desiccant System 20,000 kWh/Yr 350 therms
Table 19: Approximate Values for Economic Analysis Based on Field Test Results
Even though these are approximate costs, they are sufficient to point out the practicality of the desiccant approach. The desiccant system uses 5,000 fewer kWh per year in exchange for 350 therms of fuel, whether it be natural gas or propane.
38 American Gas Foundation, Final Report to Oak Ridge National Laboratory Under Subcontract Number 4000016141 Cinemark Theatre Plano. Texas March, 2005
Figure 89: Cost Equivalency Line for Propane Fired Outdoor Air Desiccant System vs. an All Electric Rooftop System with
Reheat
Opportunity From the results in Figure 89, the operating cost of the desiccant system versus the all electric system with reheat is runs directly through the bulk of the states. In this case, there is reason to believe that equivalent operating cost is sufficient to make the desiccant system attractive. There are two reasons for this.
First, the use of a desiccant system allows the indoor air conditioning system to be smaller, as shown in Table 17. In that table, the all electric central air conditioning system is overcooling the air to produce the needed level of dehumidification, and then reheating the air to prevent overcooling. The temperatures of the overcooled air are shown in the table, and can be compared to more air delivery temperatures which are from 55-60oF for smaller cooling systems. This overcooling requires greater air conditioning capacity which can then be reduced by using a desiccant system.
Second, all of the overcooling and reheating consumes energy. Using condenser heat for reheat, as modeled in the economics, removes the need for added reheat energy but the overcooling must be done by driving an oversized air conditioning system with added energy.
It is possible to install a desiccant system and have the capital cost reduction of the central cooling system cover some or all of the first cost premium for the desiccant equipment. This balance in first cost is highly application sensitive and it is difficult to make generalized statements about the added investment for the desiccant system.
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Snowbird Residential Desiccant System One suggested market for small desiccant systems is the residential market in southern higher-end homes. Larger homes are generally occupied by more comfort sensitive customers who would value the enhanced humidity removal possible with a desiccant dehumidifier. This has been the target market for the small Novelaire dehumidifier to date.
A suggested alternate to this market is what is referred to as the “Snowbird” market, homeowners or condominium owners in southern climates that are retired and occupy their southern homes only during the winter. Traditionally, these homeowners have had to leave their air conditioning systems in full operation while the home is unoccupied during the summer to prevent mildew damage. A dedicated small desiccant system would eliminate the need for this unoccupied AC operation, posing a considerable cost savings to the homeowner.
In these southern regions, all the way from Virginia, around the Florida peninsula to Texas, the highest end residences are on the barrier islands separated from the mainland coast by the inland waterway. In most of these barrier islands, the water table is too high to bury a gas distribution system buried. The only energy options available for these customers are electricity or propane. Providing a propane fired desiccant dehumidification option to these homes would be both attractive to the customer and may be the critical step needed to push the customer into installing a propane tank, and the propane system might also gain the water heater and other loads.
First, the economics of using a propane fired desiccant system to preserve the home during an unoccupied summer season must be analyzed. Using a small desiccant system to pressurize an unoccupied humid climate home with dry air is a different set of economics from that performed to this point. In this case the economics compare operating the desiccant system alone for a six month summer period, versus operating the air conditioner for the same period.
Results of residential modeling will be used to form the basis of the economic estimate. As part of a field test of the Novelaire residential desiccant dehumidifier, the following situation was found from modeling a continually occupied residence using Transys39.
CITY ELECTRIC KWH HRS>60% RH ATLANTA 4159 773
BIRMINGHAM 4697 770 MEMPHIS 5548 623 HOUSTON 7677 1420
TAMPA 8726 1010
Table 20: Use of a Standard Residential Air Conditioner in Humid Climates Results in Excessive Indoor Humidity for Extended Periods
Table 21 shows the energy consumption for three situations within the residence: 1) using conventional air conditioning only, 2) using conventional air conditioning with an added indoor electric dehumidifier, and 3) using conventional air conditioning with a desiccant dehumidifier. Table 20 shows how poorly the conventional air conditioning system handled indoor humidity as a large number of hours of the year are above the 60% relative humidity level. Although this
39 HUGH HENDERSON OF CDH ENERGY FOR DOE as Reported in Tim Cole, GTI, SGA Residential Marketing Conf. July, 2004
modeling assumed the home is occupied and the systems are all in operation 12 months of the year, these values give an indication of how the “Snowbird” arrangement might work.
Conventional AC
AC Plus Electric Dehumidifier
Conventional AC Plus Desiccant Dehumidifier
kWh kWh kWh Therms ATLANTA 4159 5941 3632.00 161.00
BIRMINGHAM 4697 6499 4163.00 160.00 MEMPHIS 5548 7217 4915.00 156.00
HOUSTON 7677 11660 7390.00 194.00 TAMPA 8726 12194 8071.00 274.00
Table 21: Energy Consumption of Three Residential AC Systems in a 2,000 SF Home – Conventional, Conventional with an Electric Dehumidifier, and Conventional AC with a Desiccant Dehumidifier
Comparison is shown on an Equal Comfort Basis with the AC System Set to 780F with the Desiccant Dehumidifier vs. 750F without the Dehumidifier to Obtain Dehumidification
For a more accurate analysis, the TRNSYS simulations should be redone for this specific “Snowbird” application but the cost of such simulations are outside the scope of this report and are sufficiently high that some estimate should be made of the practicality of this using a desiccant in this application before such costs are contemplated.
For the “Snowbird” option, a majority but not all of the hottest, most humid, hours of the year will be experienced during the unoccupied summer months. For the purpose of developing approximate economics, it will be assumed that 2/3rd of the overall cooling load will occur during the unoccupied period. Therefore, it will be assumed that consumption for the air conditioner and the desiccant system in the summer would be 2/3rd of the values in Table 21.
Conventional AC
Desiccant Dehumidifier
Electric Use - Summer 6
Months
Electric Use - Summer 6 Months
Net Electric Savings Propane Use
kWh kWh kWh Therms ATLANTA 2744.94 615.12 2129.82 106.26 BIRMINGHAM 3100.02 645.48 2454.54 105.60 MEMPHIS 3661.68 606.54 3055.14 102.96 HOUSTON 5066.82 1179.42 3887.40 128.04 TAMPA 5759.16 1164.90 4594.26 180.84
Table 22: Overall Savings Situation for Operating the Desiccant System to Preserve a Residence Rather than Operating the Air Conditioning During the Six Month Summer Season
The overall energy use situation for a desiccant dehumidifier operating in lieu of an air conditioner over the summer is shown in Table 22 for a number of cities. In Table 22, the energy use of the Conventional AC and of the Desiccant Dehumidifier over the 6 month summer period is shown in the first two columns. The last two columns show the reduction in electric consumption and the increase in propane consumption that would result form running the desiccant system throughout the summer in lieu of the conventional air conditioning.
In order to strike an average to use in the economic analysis, rather than taking the most extreme city, the results for Houston will be rounded to cover a situation where the desiccant dehumidifier option requires 4,000 fewer kWh per year but consumes 130 therms of gas.
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Once a customer installs the desiccant dehumidifier, it stands to reason that hey will also use the system to enhancehumidity control during the winter as well.
Table 23
Figure
uses the values in Table 21 to estimate the savings during the summer season. Onceagain, the values for Houston were used for the economic analysis, which added another 1,385 kWh of savings and 84 therms of propane use. Therefore, the economics assumed a grand total of 190 Therms of propane being used by the desiccant dehumidifier to reduce electric air conditioning consumption by 6,000 kWh each year. The economic results are shown in90.
AC Plus Electric Dehumidifier
Conventional AC Plus Desiccant Dehumidification
Electric Use -
Winter 6 Months
Electric Use - Winter 6 Months
Propane Use - Winter 6 Months
Net Electric Savings Net Propane Use
kWh kWh Therms kWh Therms
ATLANTA 1961 1211 53 750 53
BIRMINGHAM 2145 1388 53 757 53
MEMPHIS 2382 1638 51 743 51
HOUSTON 3848 2463 64 1384 64
TAMPA 4024 2690 90 1334 90
Table 23: Overall Savings Situation for Operating the Desiccant System Along with Conventional AC versus Using a Dehumidification Enhanced AC to Provide Equal Comfort in the Winter Season
Table 21 shows the energy consumption for three situations within the residence: 1) using conventional air conditioning only, 2) using conventional air conditioning with an added indoor electric dehumidifier, and 3) using conventional air conditioning with a desiccant dehumidifier. Table 20 shows how poorly the conventional air conditioning system handled indoor humidity as a large number of hours of the year are above the 60% relative humidity level. Although this modeling assumed the home is occupied and the systems are all in operation 12 months of the year, these values give an indication of how the “Snowbird” arrangement might work.
Figure 90: Equal Cost and Payback Lines for Operating a Propane-Fired Desiccant Residential Desiccant Dehumidifier vs.
a Conventional Electric AC System for Summer Unoccupied Home Preservation in Humid Climates (Light Colored Area Shows Paybacks to 7 Years for a $2,000 Installed Cost, Darker Area Shows Payback to 7 Years
if the Installed Cost is reduced to $1,200)
Current installed costs for this desiccant system have been running at $4,500. However, at that high a price, a reasonable economic savings cannot be found. Although the system may sell at this price, the establishment of a major market is unlikely unless installed costs can be reduced to the $2,000 range or less.
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Heat Pumps with Heat Recovery In the description of the Robur heat pump system, an installation layout was shown with the heat pump providing both air conditioning and recoverable useful heat. Given the difficulties in finding an application for propane fired heat cooling or pumps in hotter climates where operation is dominated by air conditioning, recovering heat from a heat pump in air conditioning operation suggested itself.
Robur has suggested that their absorption heat pump be installed in a position to provide air conditioning via chilled water and to reject the heat of air conditioning and the heat of the burner to either domestic water heating, pool heating, or both. With the interest in finding a practical propane fired cooling system for hot climates, pool heating may not be a major demand, but any load with a large air conditioning and domestic hot water load would be ideal for this system.
Figure 91: Fuel Fired Heat Pump Proving Chilled Water for Air Conditioning while Recovering Heat for Domestic Water
Heating and Swimming Pool Heating Loads Drawing Elements Courtesy of Robur)
Figure 92: Fuel Fired Heat Pump Proving Chilled Water for Air Conditioning while Recovering Heat for Domestic Water
Heating Only (Drawing Elements Courtesy of Robur)
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One market that has already been mention as being appropriate for propane desiccant systems is the resort/hotel market on hotter climate barrier island that traditionally do not have natural gas service. This may also be the best market here as: 1) hotels and resorts all have considerable domestic hot water loads for guest showers and, to a lesser extent in these hot climates, for swimming pools, and 2) more resorts are being built in more isolated locals where natural gas distribution is unavailable and the only alternative to propane systems tends to be electric heat. Many hotel type buildings use remote air conditioning packages in customer’s room. However, the lobby areas will require air conditioning. The Robur system could used as a space cooling system for the lobby and restaurant areas which tend to have a relatively constant cooling load independent of room occupancy levels.
Of particular interest is generating domestic hot water which has such universal applications as to make the system widely applicable.
Operation In order to use the Robur system in this way, the heat pump would have to have be applied to a chilled water system for delivering air conditioning which could either be part of a larger chilled water system or one dedicated to the Robur unit itself. In addition, the hot water rejection from the heat pump would need to be connected to an indirect hot water heater. Both of these accessories are widely available on the domestic market form a number of sources.
Figure 93: Concealed Fan Coil Unit (left) and an Indirect Hot Water Heater (right)
Given a large hot water load, the water heater would also need some other source of heat input which in most hotel applications is either electric resistance coils or a small boiler. In addition, some assurance that the water heating load is substantially larger than the heat pump heat rejection would be needed as the heat pump would not be able to operate unless hot water was being used on a regular basis.
Notice that although the equipment is a heat pump, the system is really laid out to deliver cooling and recover heat. If the system needs to be reversed for some limited heating periods, heat could be taken back from the hot water system. A secondary heating source on that hot water system would assure that the heat was available.
Economics The effect on the economics of the operation of the propane fired heat pump is quite dramatic. As can be seen in Figure 94 and Figure 95, the cost equivalency lines are impractically high for a system that recovers no heat and drop into the practical range of electric prices for 40% heat recovery.
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Figure 94: Cost Equivalency Lines for a Propane Fired Heat Pump in a Hot Climate if None or Only a Portion of the
Rejected Heat is Being Utilized to Displace Electric Use in an Electric Water Heater (This Projection Depends Only on the COP of the Heat Pump being in the 1.4 Range, which is Representative of
Either the Robur or a Modified Engine Heat Pump)
This heat recovery heat pump concept is based only on a manufacturer’s suggestion without available data on what the entire system would cost, nor even the best manner of installation. As a development concept, it is more practical to define the three year payback lines for a number of installation premiums, that is the increase in cost for this system over that of a conventional heat pump heating/cooling system.
If further investigation is done on this concept, defining the expected costs in detail is warranted and the results can then be interpreted by these three year payback lines as shown in Figure 95. A rough first cost estimate is shown in Table 24, and the results in that table are used to develop the shaded regions shown in Figure 95.
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First Cost Estimate for a 15 RT Heat Recovery Heat Pump System
Conventional Heat Pumps $2,500 3 $7,500
Installation $2,000 3 $6,000
$13,500 Robur Heat Pumps $6,800 3 $20,400
Installation $2,000 3 $6,000
Heat Recovery Piping $2,000 1 $2,000
Cooling Tower $3,000 1 $3,000
$31,400
Cost Premium Per Ton $1,193
Table 24: Rough Cost Estimate for Heat Recovery Heat Pump Installation
(Prices were Taken from First Cost Projections for the Water-to-Water Robur Heat Pump Plus Some Allowances for Other Required Equipment)
Figure 95: Three Year Payback Lines for a Propane Fired Heat Pump in a Hot Climate if 50% of the Rejected Heat is Being Utilized to Displace Electric Use in an Electric Water Heater
(System in Figure 91 and Figure 92 are Shown as a System Tied Together on Site. A Reasonable Direction for Cost Reduction Development is to Package the Components to Reduce Site Assembly Cost. Hot Climate Economics are
Shown Here. Advantage of Heat Recovery Declines in Colder Climates. Economics Were Done for Robur Heat Pump. Operating Economics Would Be Better for an Engine Heat Pump Operating in the Same Manner.)
One positive aspect of this system is that the economics are best in hot climates. The heat recovery operation produces the most economic benefit when the system is in cooling operation. This is the only system proposed in this report that has that operates more efficiently as the cooling hours of the year increase and therefore the only cooling system, aside from
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desiccants, that can be specifically recommended for hotter climates, and more importantly, would be the only system that is a perfect fit for hot dry climates.
Economic Proposition for the Propane Dealer For any propane fired cooling system to be accepted into the market, it must be promoted by the entire “value chain” which is all market participants that are involved in selling, servicing , and providing energy for the product. Most importantly, there must be a substantial financial incentive for propane dealers if they are to accept and promote the products to their customers.
Propane dealers have the most intimate customer relationship with propane users of any participant in the value chain. The dealers are delivering propane to the customer on a regular basis which involves dealer employees visiting the customer’s homes and the propane dealers are mailing bills to the customer on a regular basis. Either the visits or the bill could be an opportunity to deliver information to the customer on new propane cooling or heat pumping products. In addition, the propane dealers billing records could be used to determine which customers have been ordering fuel for how many years, records which provide a valuable insight on which customers are likely to have heating and cooling equipment which is due for near term replacement.
The propane dealer’s incentive to promote new cooling or heat pumping equipment varies widely depending on the competitive situation. In cold climates, the propane dealer may feel a limited motivation to promote a propane fired heat pump to existing propane furnace customers, as the customer may have little alternative fuel choices. In colder climates, heating customers beyond the reach of natural gas distribution can only realistically decide between propane and fuel oil when replacing their heating system. In the North Central states, heating oil has been a very minor market participant in recent years. Therefore, these customers may be largely “captive”, and the reduced heating season use of a propane heat pump may be a disincentive for the propane deal to promote this new technology.
Conversely, although heating oil is usually more expensive, there is a strong traditional use of heating oil in the Northeast. Propane dealers in this area may desire to use a propane heat pump to promote the use of propane. It is not expected that the engine heat pumps discussed in this report will ever be available for operation on heating oil.
In warmer climates, the customer’s alternatives include the use of electric heat pumps for heating and cooling, and propane dealers may need this new technology to retain existing customers, and to recruit new customers.
Table 25 shows an estimate of the dealers added revenue for fro a single sale of a variety of cooling and heat pump technologies. Table 26 shows an estimate of what a market roll out of one of these technologies could benefit the overall propane industry. In this example, the sale of 100,000 engine heat pumps to customers in mild climates that would have otherwise used electric heat pumps would be a total 10 year revenue addition of $741 million, and an estimated margin addition of $95 million.
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Customer New Technology Conventional Technology
Added Propane
Use Per Unit
Type and Climate Heat Cool Type Heating COP
Cooling COP
Propane Use40
Propane Use41
MBH RT Gal./Yr
Gal./Yr Gal./Yr
Residential Hot 60 5 1.4 1.2 1071 Furnace/AC 162 909
Residential Mild 80 5 1.4 1.2 1027 Furnace/AC 711 316
Residential Cold 100 5
Propane Heat Pump
1.4 1.2 1155 Furnace/AC 1076 79
Residential Hot 60 5 1.4 1.2 1071 Elec. HP 0 1071 Residential Mild 80 5 1.4 1.2 1027 Elec. HP 0 1027
Residential Cold 100 5
Propane Heat Pump 1.4 1.2 1155 Oil
Furn/AC 0 1155
Commer-
cial Hot 120 10 1.4 1.2 2142 Gas Rooftop 323 1819
Commer-cial Mild 160 10 1.4 1.2 2054 Gas
Rooftop 1421 633
Commer-cial Cold 200 10
Propane Heat Pump
1.4 1.2 2310 Gas Rooftop 2153 157
Commer-
cial Hot 120 10 1.4 1.2 2142 Elect Rooftop 0 2142
Commer-cial Mild 160 10 1.4 1.2 2054 Elect
Rooftop 0 2054
Commer-cial Cold 200 10
Propane Heat Pump
1.4 1.2 2310
Elect Rooftop 0
2310
Residential Hot Humid
400 CFM System Snowbird System 200 Elect.AC
/Dehum 0 200
Commer-
cial Hot
Humid 10000 CFM
System Desiccant Ventilation
Dehumidifier 3600 Elect.AC/Dehum 0 3600
Table 25: Financial Incentive for Dealer per Unit of Equipment Sold
40 Propane Use as projected by the Economic Modeling used Throughout Chapter 6 41 Assumes a Conventional 78% Efficient Furnace and Electric Air Conditioning or a Conventional Electric Rooftop Unit. Desiccant Comparisons Assumes the Addition of an Electric Dehumidifier
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Propane Heat Pump Versus Electric Heat Pump in a Mild Climate42
Year Unit Sales43
Incremental Annual
Gallons44,45
Cumulative Gallons46
Annual Revenue
Annual Margin
1 2000 2,054,000 2,054,000 $4,005,300 $513,500 2 3000 3,081,000 5,135,000 $10,013,250 $1,283,750 3 4000 4,108,000 9,243,000 $18,023,850 $2,310,750 4 6000 6,162,000 15,405,000 $30,039,750 $3,851,250 5 8000 8,216,000 23,621,000 $46,060,950 $5,905,250 6 10000 10,270,000 33,891,000 $66,087,450 $8,472,750 7 12000 12,324,000 46,215,000 $90,119,250 $11,553,750 8 15000 15,405,000 61,620,000 $120,159,000 $15,405,000 9 18000 18,486,000 80,106,000 $156,206,700 $20,026,500
10 22000 22,594,000 102,700,000 $200,265,000 $25,675,000 Total for the 10 Year Period $740,980,500 $94,997,500 Gallons/Unit 1,027 Revenue/Unit $2,003 Margin/Unit $257 Revenue/Gallon $1.95 Margin/Gallon $0.25
Table 26: Example Estimated Market Return to Propane Dealers for a Market Roll-Out over a 10 Year Period
Total Unit Sales in this Projection is 100,000 Engine Heat Pump Systems and Units are assumed to Replace Electric Heat Pumps
42 Equipment Life Assumed to be 15 Years 43 Technology Roll Out Product Sales Projection Suggested by R. Sweetser 44 Assumes 1,027 Gallons/Year Usage as Shown in for a Residential Application in a Mild Climate Table 2645 Refers to the Gallons of Propane Burned per Year from Units installed in the Same Year 46 Refers to the Gallons of Propane Burned per Year from Units installed in the Same and All Previous Years
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Chapter 7: Summarized Results and Suggested Directions for Propane Driven Air Conditioning Development and Commercialization
Opportunity Summary
Market Market Size
Oper. Cost on
Propane
Equipment Available
Maint. Needs
First Cost
Premium
Better Comfort
Propane Load
Added
MARKETS RECOMMENDED
Snowbird Desiccant System
Desiccant Motel Dehumidification Commercial Engine Driven Rooftop Heat Pump
(GEDAC System) 47 48 49
Engine Driven Split System Heat Pump (Aisin Seiki Type)
Ammonia Absorption Heat Pump 36
Ammonia Absorption AC in Off-Grid Homes 50 51
Bromide/Water Absorption AC: Off-Grid Homes 52
53 36
Off Grid Propane Driven Cogen & Cooling 54
Propane Absorption AC with Heat Recovery
MARKETS NOT RECOMMENDED
Propane Engine Driven AC
Ammonia Absorption AC 36
Lithium Bromide/Water Absorption AC 55 39
On Grid Propane Driven Cogen & Cooling
Large Region Niche
Good Fair
Poor
Domestic Foreign
Develop
Low Fair
High
None Yes High
Yes No
Good Fair
Poor
Table 27: Summary of Suggested Market Opportunities (This table summarizes the finding of the report over differing systems)
47 Operating Cost on Propane is Highly Competitive when Competing with All Electric Heating and Cooling Rooftops 48 Some Engine Heat Pump Systems are Approaching 10,000 Hours of Operation without Regular Maintenance, a Significant Advance Over Earlier Systems 49 Engine Heat Pump Systems Typically Deliver Higher Heating Air Temperature than Electric Heat Pumps, Making Spaces More Comfortable in the Heating Season 50 The only current supplier, Robur, does have limited North American marketing. 51 First Costs Evaluation for an Off Grid Home Involves the Propane Fires System Allowing for a Smaller Generator 52 Broad, a Chinese manufacturer, is the only current supplier 53 Lithium Bromide /Water Systems require an open cooling tower which tends to be somewhat more maintenance intensive than the radiators used for ammonia/water systems 54 The only current supplier for the cooling system, Yazaki, does have a North American marketing group. 55 Somewhat Higher COP’s Available from Lithium Bromide/Water Systems Improve Economics
Suggested Research and Development Directions Each of the market opportunities in Table 27 suggests issues and direction for further technical development or product introduction testing. These will be broken down individually and ranked by technical and market potential.
1. Propane Commercial Engine Driven Heat Pump GEDAC is the major developer of the rooftop version of this equipment in the United States. To date, they have been developing laboratory test models to operate on natural gas. Testing one of these units on propane to check for proper engine operation should be sufficient to validate using propane in their equipment. Beyond that, the durability testing of the GEDAC rooftop unit, whether on natural gas or propane is essential for both the gas and propane industries, and the best suggestion would be co-funding such testing. Durability test results should not be affected by the choice of gas or propane fuel. One element that would be desirable for the GEDAC unit would be a carburetion system that can handle EITHER natural gas or propane without a carburetor change-out. Distribution of this system would be easier if stocking a completely separate propane only version was not needed.
Although the GEDAC system is still in development, the large size of the potential market for this system has caused GEDAC to be ranked first in development opportunities.
2. Snowbird Desiccant System The market for this dehumidification system is localized, but the near term availability of equipment has caused this opportunity to be ranked second.
A small residential desiccant system is currently in market introduction fueled by natural gas. A burner modification kit may be needed for propane depending on the flexibility of the gas valve being used. Beyond this, the use of the system to produce proper dehumidification on an unoccupied home in a humid climate has not been field tested. Success of the system will depend on the capacity of the unit and the permeability of the houses construction. It would be best to test the system on a residence constructed in the most typical manner possible for humid climate homes.
Current field tests have carried a rather high electric use penalty for operation of the desiccant system. These tests have followed a pattern of installing the dehumidifier such that the dehumidified air is then distributed throughout the home by the central air distribution system. This means that operation of the large central blower is required.
For the “Snowbird” concept, there may be no reason to operate this central blower. It has long been known that humidity within a home diffuses rapidly and installing the system independently of the central ductwork may be sufficient. A single point of discharge from the dehumidifier may be enough to dehumidify the entire residence with reasonable uniformity. It is suggested that this be tested as part of any field test by equipping the home with multiple dispersed humidity monitors located to determine dehumidification dispersion.
In the data interpretation process for any field test, the TRNSYS model developed from previous field testing should be verified for a dehumidifier working on an unoccupied home. The model can then be used to project customer savings over a number of humid climates of varying severity. Operating cost advantages may extend beyond the Deep South into more northern coastal areas where electricity is more expensive, perhaps as far north as New England.
Another challenge for this system is the current very high installed cost. Although, the $4,500 installed costs currently seen may be little problem in the high end residential market, moving into a larger market will require a more moderate installed cost in the $2,000 range.
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3. Desiccant Hotel Dehumidification The market for this dehumidification system is localized, but the current availability of equipment has caused this opportunity to be ranked third.
A number of field tests have been performed in the past on desiccant dehumidification in hotels using natural gas fired Munters’ systems. Field tests of the new SEMCO Revolution system are underway now. Propane applications would not be enough of a technical change to require further field testing of these same systems unless justified as part of a marketing program. The suggested course of action for this market would be to use the field test data developed in the past to create informational literature for some of the larger hotel chains and discuss the concept with the major chains. In general, for hotel chain operations to embrace using the system in appropriate humid locations, the central management of the chain must approve the system. It should be noted that most major hotel chains use independent “hotel development” companies to handle the construction of new hotels and the design professionals at these companies will be an essential contact for this technical literature.
In longer term technical development, finding a more compact low cost system that could serve the commercial market with 3-10,000 cfm of dehumidified air would be a plus for this market. A more detailed investigation of the AIL Research system is suggested to determine if the plastic plate liquid desiccant could be of use in this market. If so, some cofunding of the current DOE supported work may be appropriate.
4. Propane Fired Absorption or Engine Driven AC in Off-Grid Homes This is the one market where the high first cost and operating cost of propane air conditioning would be justified as a smaller on-site generator could then be used to power the home. The combination of small on-site propane fired generator, propane refrigerator, furnace, water heating and propane fired air conditioning would be able to provide all of the services required for homes not connected to the electric grid. The economics of applying propane fired AC systems to off-grid homes are excellent. However, the limited number of off-grid homes in North America has caused this opportunity to be ranked fourth.
Absorption air conditioning is generally recommended for this market. Absorption systems require less maintenance than engine systems and have a reputation of running for years with little or no service. As off-grid homes are, by definition, remote, any need for regular service may be problematic. However, engine systems are now featuring longer service intervals which may make the system practical for remote site applications.
5. Propane Fired Cooling with Heat Recovery Even in hot markets where propane fired cooling is uneconomical; propane fired cooling with heat recovery does pose an economically attractive market, even where electricity is available. Particularly attractive applications would be in hot climates where facilities have a 12 month need for the recoverable heat, particularly for extensive domestic hot water or pool heating loads such as the hotel market.
In order to make this an attractive opportunity, the entire cooling and heat recovery package would need to be developed based on existing cooling systems such as the Robur or GEDAC system. The need for this development causes this opportunity to be ranked fifth. However, the market would be large and system would be attractive in hot dry climes such as Arizona, New Mexico, Nevada, and Southern California which are fast growing regions which are not appropriate e for the other opportunities targeted.
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Opportunities Noted that Do Not Involve Propane Fired Cooling In the research done for this report, a number of opportunities arose that do not expressly involve gas cooling which should be noted.
Propane Fueling for emergency generators at commercial facilities with no gas service is one new opportunity. Using propane on an emergency generator would allow the customer to use the generator to avoid period of high deregulated electric prices without the air quality problems that arise with extensive diesel fuel operation.
Given the current interest in indoor air quality, exploiting the portability of propane for desiccant based drying for flood and mold recovery is also an interesting potential market.
Markets Not Recommended
Propane Absorption Heat Pump For Space Heating and Cooling
To date, none of the Robur heat pumps have been installed in North America. An instrumented laboratory test, to confirm performance, and a field test, to confirm durability, of this equipment would be appropriate before marketing this equipment for space heating and cooling applications. As all of the installations to date have been in Europe, confirming that the unit will operate properly in more severe North American winter weather is important.
Part of this field test would be confirming how well the water delivery system of the heat pump integrates into American indoor fan coil packages, how quickly the system starts, how well it dehumidifies in cooling, how well the outdoor coil defrosts in heating and what level of delivered air temperatures can be achieved in heating.
Delivered air temperature in heating is important to both the natural gas and the propane industry as both have counter-marketed electric heat pumps on the basis of their low delivered hot air temperatures.
As was seen in the last chapter, customer economics on a heat pump system are poor in cooling operation and quite good in heating operation. Unfortunately, this means that this system would be most attractive to more northern customers and that the load building opportunity for propane would be limited in the north as winter heating propane consumption would be reduced.
Heat Pumping with Heat Recovery
A more attractive option for the propane industry would be the application of these absorption heat pumps with heat recovery to combat all electric systems in areas not served by natural gas. To provide the market with an acceptable package for these applications involves going beyond what can be purchased directly from Robur. The HVAC installer cannot be expected to properly integrate parts from differing sources. Rather, the full package including the heat pump, fan coils, water heating equipment, and an outdoor radiator would have to be integrated into a full working system and supplied as a completely packaged solution. This will require design work, tying together a number of suppliers, testing the overall package, and making marketing arrangements.
The flexibility of the Robur water to water heat pumps to fill various market roles needs to be explored. Recovered heat from air conditioned occupied spaces could be used for water heating or pool heating. The potential efficiencies of such an overall package of this type could be quite high. However, the package layout would have to be developed as well as a control
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and heat rejection system to allow the air conditioning to continue to operate when rejected heat is not needed.
This package development work would require both a laboratory development and a business relationship development with a North American packager willing to market the system. Although such HVAC packaging firms are common, they universally develop custom products for the commercial market, as the barriers to entry in the residential market in terms of marketing costs are too high. Therefore, it is suggested that this package be aimed at specific commercial markets. Two suggested markets would be hotels or sit down restaurants with wear washing facilities (for packages set to reject heat to swimming pools or domestic water heating).
Best applications for a heat pump with heat recovery would be southern markets with long cooling seasons. Unlike using the heat pump without heat recovery, the propane industry opportunity would be a package that could capture the air conditioning load with sufficient efficiency to provide good customer economics in cooling and to build summer propane load.
Heat Pumping for Dedicated Heating Applications
The Robur heat pump could also be used in a dedicated heating application. Swimming pool heating in areas not served by gas distribution where electric resistance or electric heat pump swimming pool heaters are currently being used is one possible market. Once again, development would be needed to establish a package matching the heat pump with heat recovery equipment.
Propane Engine Driven AC As can be seen in Figure 80, propane fired air conditioning without heat pumping used in locations where utility electricity is available would require coefficients of performance (COP) in excess of 1.2 just to achieve equal operating costs. Even these high efficiencies would not produce savings to justify the added cost of the equipment. Given that the propane market is targeted to smaller equipment, the likelihood of smaller units achieving COP’s in excess of 1.2 is unlikely, and this market does not seem appropriate for propane
Propane Fired Absorption AC Absorption systems tend to have even lower COP’s than engine systems and therefore propane fired absorption air conditioning without heat pumping or some form of heat recovery does not seem to be an appropriate market for propane.
Off-Grid Propane Driven Cogen & Cooling One variation on the off-grid operation concept would be to use the waste heat from a propane generator to drive the absorption cooling system as well as space heating and hot water. This adds some complexity to the system and requires an absorption system that can use the waste heat. In general, such absorption systems are larger than residential in size. Best applications for such systems would be in commercial facilities rather than residences. Off-grid schools, clinics and small medical facilities may be the best applications. The equipment for such systems is available but has not been widely seen in the marketplace. Field demonstrations of this approach would be a valuable part of the market promotion.
Suggested Directions for Additional Market Research This report is an overview of the opportunity posed by the concept of propane fired cooling. Approximate economics were developed to show where opportunities lay and which direction in future development would be inclined to be most productive. In order to cover a wide gamut of possible technical approaches, the economics shown in this report needed to be cursory. Once
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a few specific technologies and market segments are chosen, more detailed economics and further work in developing market analysis is warranted before large development expenditures are committed to.
In addition, the competitive picture between propane and electricity is currently in a state of considerable flux. Many areas of the country are only beginning to see the long term implication of electric deregulation and of the current situation in electric markets. Potential increases in electric prices, as described in the next section, should also revive interest in natural gas fired cooling systems and the potential for cooperative development programs between the natural gas and propane industries should increase.
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Market Forces Affecting Propane Fired Cooling
Deregulation and the Condition of the Electric Generating System in the US The economics of propane fired cooling are affected most strongly by current propane and
electric prices. On the electric side, the national market for bulk electric trading has been open fnearly 10 years. The push for open markets and electric deregulation has largely come from industrial customers that have effectively be subsidizing residential and light commercial customer electric prices for decades. This argument has been accepted by Federal regulators that have been converting the interstate market for electricity from a closed contract arrangement to an open bidding market. Given the need to assure the economic competitiveness of the American industrial sin the global market, it is likely that this trend wcontinue.
or
ector ill
The implications for electric markets are only b
3
As shown in Figure 9657, market forces after the
ake
l gas
e
of these forces are being felt now. Illinois is deregulating electric markets
g
ecoming apparent. Open markets have led to significant growth in interstate power trading. This has pushed the current electric transmissionstructure to the limit and in some cases beyond, as seen in the East Coast Blackout of 200which was blamed on higher transmission volumes due to power trading56. Focus on needed transmission capacity additions, operator training and improved control systems should be expected to add to the cost of delivered power in the long run.
Enron collaps bstantially reduced planned generation capacity additions and recent volatility in natural gas prices in the wof Hurricane Katrina have added to this uncertainty as planned capacity in naturafueled power plants now look more uncertain than ever. Over the last 3 years bulk power prices, prices paid for electricity on the open market by large customers and utilities have increased from averaging in the $25/MW rangto the $50/MW range and in many areas have been highly unstable.
Examples of the effect
e have su
on January 1 of 2007 and a 20% increase in residential electric prices has already been accepted by regulators. Maryland, is also predictina 70% electric rate increase in 2007 and other states have had similar electric price pressure that have only temporarily been delayed for political reasons by the upcoming 2006 elections. Electric prices in 2007 are inclined to be unstable in many states.
56 Final Report on the August 2003 Blackout, Causes and Recommendations, US/Canadian Power Outage Taskforce, 2004 57 2005 Long-Term Reliability Assessment, The Reliability of Bulk Electric Systems in North America, North American Electric Reliability Council September 2005
Figure 96: Projected Electric Generating Capacity Additions
(North American Electric Reliability Research Council)
Figure 97: Age of Generating Plants in the United States
(Power Plants from Before 1950 are Dominated by Hydroelectric Dams with No Known Lifetime Limits)
(Energy Information Agency)
One of the underlying market forces in electric supply n the US is the age of the electric generating infrastructure. A shown in Figure 97, many of the electric generating plants in the United States were built between 1950 and 1970 and are now being pushed into operating lifetimes that were never planned by the original designers. Nuclear plants that were originally designed for 20-25 year lives are now being widely licensed to 40 year lives or more and coal generating plants that could be replaced with more efficient coal generators are being pushed to continued operation
Rural electric utilities and cooperatives are being affected by these market forces. Many smaller rural utilities may have few in-house generating assets and depend on open market prices for the bulk of their electric supply. Although these utilities may currently have long term contracts, over time market forces will affect new contract negotiations, and increase rural electric prices. As these rural customers form the base of the propane market, the competitive situation of propane versus electricity should improve.
These market forces play a role whether a state has deregulated intrastate electricity or not. States with the traditional regulated electric utility arrangements will be as strongly influence by interstate prices and electric supplies as those that have deregulated, as their prices for electricity imported into the state will increase as will the temptation for in-state generators to sell power out-of-state.
The Condition of Propane Supply Propane and butane are produced as by-products of the natural gas cleaning process and the production of propane fluctuates directly in step with the production of natural gas. Whether propane prices are high or low, propane must be removed from natural gas before transmission system compression of the natural gas.
The damage to the Gulf supplies of natural gas from Hurricane Katrina had a direct impact on propane supply. High prices in the winter of 2005-2006 have substantially declined as repairs to the natural gas system have been carried out. The long term outlook for lower propane prices is also clear.
Propane is also not as extensively driven by crude oil prices as is natural gas. High crude oil prices tend to drive natural gas prices up as many large industrial customers are capable of burning either natural gas or fuel oil, and tend to switch between fuels as prices dictate. However, higher natural gas prices increase gas production and therefore propane production. As there is little dual fuel use by large customer of propane, high gas prices tend to increase propane production without increasing propane demand which generally moderates propane prices. A reduction in the difference between natural gas prices and propane prices would not be unexpected over the next year or two.
The foreign market for propane may also affect propane prices in the future. A number of countries such as Algeria and Indonesia that have focused on the export of liquid natural gas are now investing in technologies referred to as gas liquids production in which methane is converted by chemical processes into heavier petrochemical fractions such as propane and butane. These countries rightly see these products as having a higher value on the world market and these products are easier to transport and to receive in harbor. Propane is a way for these low gas producers to enter the American market without the construction of what has proven to be environmentally controversial liquid natural gas receiving ports.
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Appendix 1: Desiccants and Energy In any discussion on the energy benefits of differing air conditioning systems, it is essential to keep in mind the original motivation for installing an air conditioning system in the first place. Except for weakened populations as in hospitals and the like, air conditioning is rarely a life safety issue. In most cases, the desire for air conditioning is based on the need for occupant comfort. With residential air conditioning, what an older generation may view as a luxury a younger generation may view as a necessity.
In commercial buildings, such as offices, school, retail, and the like, the need to maintain indoor comfort is essential to maintaining worker productivity or customer satisfaction. Concerns about the energy efficiency of the air conditioning system must take a back seat to these concerns. A decline in worker productivity of just a few percent in an office building can easily outweigh, in dollars per day, the cost of operating any HVAC system. Consider that an office building of 20,000 square feet with typically 100 workers may have a payroll of at roughly $10 Million per year with benefits, or $40,000 per day. The 50 or so ton air conditioning system needed to cool this space is a small cost item in comparison. Any air conditioning efficiency enhancement that lowers indoor comfort and decreases productivity by even 2% adds $800 a day to payroll costs in the long run. Therefore, it is important to evaluate air conditioning efficiency enhancement on an EQUAL COMFORT BASIS. In addition, it is also practical to consider opportunities to enhance comfort, even if energy consumption is INCREASED, as a viable business proposition.
An Example – Movie Theater in a Humid Climate To look at how a desiccant system can improve indoor conditions, we will look at a specific application with needs that desiccants are particularly suited to satisfy. This is not to say that desiccants are good for all application, but rather that certain specific cooling load situations, situations that seem to be becoming more common in commercial buildings, are most appropriate for desiccant system. Movie theaters, schools, meeting rooms, and anywhere a sizable population gathers is a good example of a situation where desiccant can assist in meeting the air conditioning load.
We will use a single zone air handler for the air conditioning system in this theater. This is a good choice for movie theaters as the individual control allowed by single zone air handlers allows the system to be shut down when the theater is not in use.
We will first look at the interior loads. Seated people give off roughly 250 Btu/Hr in sensible load and 200 Btu/Hr in latent load or humidity. The latent load is large given off in exhalation. This means that the human load has a sensible heat ratio of roughly 0.55, or that is a little over half of the heat given off from people at rest is in sensible heat. In a movie theater, this will be the only major interior heat gain and even allowing for minor sensible heat gains the theater will have a sensible heat ratio of no more than 0.6.
Activity Application Total Heat (Btu/Hr.)
Sensible Heat (Btu/Hr.)
Latent Heat (Btu/Hr.)
Seated Office, School, Theater 450 450 200
Standing, Walking Retail 450 450 200
Heavy Work Factory 1450 580 870
Athletics Gymnasium 1800 710 1090
Table 28: Human Loads for Vary Activities
To maintain a condition of 78oF and 50% relative humidity in the theater, the “Room Load Line” must be at a specific slope as dictated by the Pychrometric Chart.
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Figure 98: Psychrometric Diagram of 0.6 SHR Load Line
The Room Load line is developed by drawing a line through the desired room condition at an angle determined by the Sensible Heat Ratio protractor shown in the upper left off the figure.
As long as air is admitted to the space from the air conditioning system anywhere along this “Load Line”, the air will mix with room air and remove the correct ratio of sensible and latent heat needed to maintain BOTH the temperature and humidity load. Unfortunately, cooling coils behave in the manner shown in Figure 99.
Figure 99: Layout of a Simple Cooling Coil, Cooling Coil Lines and Load Line
The cooling coils reduce the temperature of the air until the relative humidity strikes the 100% RH line and then the air temperature drops down the 100% RH line with both cooling and dehumidification occurring simultaneously. If this process were used for our example, the cooling coil would have to cool the air to roughly 38oF before releasing the air back into the room at a point INTERSECTING the room load line.
Cooling air to such a low temperature is not practical. Most air conditioning systems are built for much higher air delivery temperatures. In addition, the surface temperature of most cooling coils is 6-8oF degrees colder than the delivered air temperature desired. To deliver 38oF air, the dehumidification on the coil would be in constant danger of freezing and plugging.
To avoid this, the traditional method of meeting this type of cooing load is called terminal reheat. In a reheat system, the air can be cooled to a more achievable 52-55oF and then reheated until
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it reaches the Room Line. Unfortunately, not only does the act of reheating this air require energy but the heat input to the air is an added heat load that must ultimately be removed by the air conditioning system, expanding both the size and the energy consumption of the AC system.
Figure 100: Layout of a Reheat System, Cooling Coil Lines and Room Line The horizontal line shows the air leaving the cooling coil at 55F and being heated to a higher temperature to meet the room line.
To see the effect, cooling load calculations need to be done. The theater’s cooling load is 100,000 Btu/Hr. However, to properly maintain humidity requires 36,363 Btu./Hr of reheating, and the load on the air conditioning coil, referred to as the coil load, is 136,363 Btu/Hr.
Actual Room Load
People Sensible
Load/ Person
Latent Load/
Person
Sensible Load Latent Load Total
Load
Btu/Hr Btu/Hr Btu/Hr Btu/Hr Btu/Hr
200 250 250 50000 50000 100000
Cooling Calculation With Required Reheat Coil
Point Temp RH Enthalpy Air Density
Btu/lb cu.ft./lb
Room 78 50% 30
Exit Cooling Coil 52 100% 21 12.7
Exit Reheat Coil 61 70% 23.4 13.28
Net Cooling 6.6
Reheat Energy 2.4
Net Cooling per lb of air 6.6
lb or air required/hr 151,512
Air Density (cu.ft./lb) 13.28
Airflow Required (CFM) 3354
Coil Load (Btu/Hr.) 136,364
Coil Load (RT) 11.36
Reheat Energy Required (Btu/Hr.) 36,363
Table 29: Coil Load Calculation for Handling the Theater with a Reheat System
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Next, we look at the same application with a desiccant system.
Figure 101: Layout of a Desiccant System, Cooling Coil Lines and Room Line
Desiccant Cooling System
Point Temp RH Enthalpy Density
Btu/lb cu.ft./lb
Room 78 50% 30
Exit Cooling Coil 58 100% 25 12.7
Exit Desiccant 58 75% 26 13.2
Net Cooling 4
Reheat Energy 0
Room Load
People Sensible
Load/ Person
Latent Load/ Person
Sensible Load Latent Load Total Load
Btu/Hr Btu/Hr Btu/Hr Btu/Hr Btu/Hr
200 250 250 50000 50000 100,000
Net Cooling per lb of air 4
lb or air required/hr 25000
Air Density (cu.ft./lb) 13.2
Airflow Required (CFM) 5500
Coil Load (Btu/Hr.) 125,000
Coil Load (RT) 10.42
Desiccant Regeneration Energy Req. (Btu/Hr.) 25-35,000
Table 30: Coil Loads with Desiccant System Heat used to regenerate the desiccant is largely exhausted rather than heating the space, reducing the cooling load.
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It is not hard to find more dramatic examples. Using Table 28, for a gymnasium or athletic club, humans under exertion produce 1,800 Btu/Hr. with a full 1090 Btu/Hr. in latent heat. Even with some sensible heat load from lights, Sensible Heat Ratios as low as 0.5 are quite possible.
Figure 102: Load Line Analysis for an SHR = 0.5
In the case of a Sensible Heat Ratio of 0.5, the load line never intersects the coil line and meeting the 78oF, 50% RH condition is IMPOSSIBLE without either reheat or a desiccant system
Figure 103: What Happens in an SHR=0.5 Situation without Reheat or Desiccant Assistance
If neither reheat nor a desiccant is used, the ~52-55oF exiting temperature of the air conditioning system, the thermostat set point of 78oF, and the fixed slope of the load line will dictate that the Load Line will shift upward. In this case, the room condition will settle out at a stifling 78oF and 68% RH!
Thus far, we have looked at interior loads only and found that desiccant systems can reduce the cooling load handled by the refrigeration system for rooms that have low sensible heat ratios’ (generally below 0.65). Highly populated rooms with little other cooling load are one example of such spaces. At even lower sensible heat ratios, desiccants can be the only viable alternative to an energy wasteful reheat system in producing practical indoor conditions.
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Finally, it should be remembered that in many areas, energy codes do not allow reheat to be used in such applications as office and retail spaces. In most occupied spaces with low sensible heat ratios, uncomfortable conditions are simply being endured. Potential increases in worker productivity or customer appeal from enhanced comfort are yet to be exploited.
Ventilation Air Handling ventilation air loads is also an important issue. In this case, the humidity of the outdoor air versus the temperature dictates what the sensible heat ratio is when cooling this ventilation air. ASHRAE Standard 62 suggests 15 CFM of ventilation air for each person in high occupant applications. For a movie theater with a capacity of 200 persons, this is 3000 CFM of outdoor air.
Outdoor climate is now important in ventilation loads. Although we could focus on the design day, such conditions rarely occur. From an energy point of view, we are most interested in conditions that occur commonly throughout the year. This leads the focus to more humid climates where humid outdoor weather occurs on a regular basis.
Design conditions, even in northern climates, can be as high as 95oF DBT/78 WBT, resulting in a dew point of about 72oF, but this happens rarely. In humid climates, dew point temperatures will remain at or above 75oF for much of the year, including nights when the dry bulb temperature will fall without major decline in absolute humidity. A dew point temperature of 75oF is an absolute humidity of 126 grains./lb of dry air. Bringing this air into a conditioned space in large quantities can form a large latent air conditioning load.
For our ventilation example, we can also assume a higher sensible heat ratio at 0.75, more typical co commercial buildings. This will illustrate that in humid areas, the outdoor air alone causes problems, without the added element of low indoor SHR’s. In addition, we will look at a situation where the ventilation air is 50% of the total recirculated air, which tends to happen in highly occupied spaces such as theaters, schools, and the like.
Figure 104: Process Line for Outdoor Air Treatment Using a Conventional Cooling System at Full Load
The conventional approach is to mix the outdoor air with the return air and pass all of the air through cooling coils before returning the air to the space. Humidity control can be achieved when indoor cooling loads are high.
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Figure 105: Process Line for Outdoor Air Treatment Using a Conventional Cooling System at Part Load
As indoor loads decline on cooler humid days, the cooling coil is cut back by the thermostat and return air temperature rise, reducing dehumidification. The coil line no longer reaches the load line. This impossible situation requires the load line to rise until it reaches
the end of the coil line and closes the cycle. This requires indoor humidity to rise dramatically
Figure 106: A Dedicated Desiccant Outdoor Air Treatment System
A dedicated desiccant system for the outdoor air can sequentially dehumidify and then cool outdoor air to the indoor condition. Conventional cooling can then control the indoor load and the room condition will not vary in humidity at any load. Note that much of
the cooling can be done by outdoor air without refrigeration.
The Psychrometric charts shown in Figure 104 through Figure 106 shows how a desiccant system set up to reduce the humidity of the outdoor airflow can produce ventilation air at the required indoor condition in both temperature and humidity, leaving the conventional cooling system to air condition indoor load independently. Effectively, the conventional cooling system never sees the outdoor air load.
In more aggressive applications, the outdoor air can be reduced to an absolute humidity BELOW the indoor set point, and the dried ventilation air will remove indoor latent load by flushing this dried air through the building, thereby reducing the latent load on the conventional system.
A major energy advantage in using desiccants to dry ventilation air is that the energy of desiccation heats the air well above outdoor air temperatures, as can be seen on Figure 106. This higher temperature heat can then be largely but not entirely removed by a flow of outdoor air, without adding this load to the refrigeration system. This is not possible with conventional dehumidification on cooling coils.
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In some system, this heat of desiccation is routed back to the desiccant wheel to pre-heat combustion air to the desiccant regeneration heater, making the system even more energy efficient.
In general, this application for desiccants becomes more practical as the percentage of outdoor air required increases. For ventilation airflows below 20% of the re-circulated supply air flow, there may be little benefit from a desiccant system. However, as ventilation air flows climb, desiccants gain greater advantage.
Summary The two applications that have been examined are:
• Cooling loads with low Sensible Heat Ratios (Less than 0.65)
• Spaces with Ventilation Rates Above 20% in Humid Climates
In most popular applications to date, both of these drivers have been present. Examples include supermarkets (Very Low Sensible Heat Ratios), Movies Theaters (Low Sensible Heat Ratios and High Ventilation Rates), Motels (Dried Ventilation Air Sweeping Humidity from Unoccupied Rooms), and Ice Arena (Low to Negative Sensible Heat Ratios), generally all in humid southern climates
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Appendix 2: Glossary
Central Air Conditioner A central air conditioner model consists of one or more factory-made assemblies which normally include an evaporator or cooling coil(s), compressor(s), and condenser(s). Central air conditioners provide the function of air-cooling, and may include the functions of air-circulation, air-cleaning, dehumidifying or humidifying.
Condensate The liquid resulting when a vapor is subjected to cooling and pressure reduction. Also, liquid hydrocarbons condensed from gas and oil wells. Compare LIQUIDS, NATURAL GAS
Condensation A change of state during which a gas turns to liquid, usually because of temperature or pressure changes.
Condenser A device used to liquefy water from a moist gas stream.
Degree Day, Cooling A measure of the need for air conditioning (cooling) based on the extent to which the daily mean temperature rises above a reference temperature, usually 65oF. For example, on a day when the mean outdoor dry-bulb temperature is 75oF, there would be 10 degree days experienced. A daily mean temperature usually represents the sum of the high and low readings divided by two.
Degree Day, Heating A measure of the coldness of the weather experienced, based on the extent to which the daily mean temperature falls below a reference temperature, usually 65oF. For example, on a day when the mean outdoor dry-bulb temperature is 35oF, there would be 30 degree days experienced. A daily mean temperature usually represents the sum of the high and low readings divided by two.
Dehumidify To reduce by any process the quantity of water vapor contained in a solid or gas.
Desiccant Any absorbent or adsorbent liquid or solid that will remove water or water vapor from a material. In a refrigeration circuit the desiccant must be insoluble in the refrigerant.
Enthalpy The thermodynamic measure of heat content. Enthalpy is used as a way to quantify the amount of energy released or absorbed when a system changes from one state to another.
Gas/Electric Package Unit A single package unit with gas heating and electric air conditioning that is often installed on a slab or roof.
Heat A form of energy that is released by the burning of fuel. In an engine, heat energy is converted to mechanical energy.
Heat Balance The accounting of the energy output and losses from a system to equal the energy input.
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Heat of Compression An increase in temperature brought about by the compression of a gas.
Heat Capacity. Quantity of heat required to raise the temperature of a unit quantity of a substance one degree. Interchangeable with "specific heat" in common usage
Heat, Latent Change in heat content of a substance when its physical state is changed without a change in temperature; i.e. boiling or melting.
Heat, Sensible That heat which, when added or subtracted, results in a change of temperature, as distinguished from latent heat.
Heat, Specific The heat required to raise a unit mass of a substance through a degree of temperature difference. Also, the ratio of the thermal capacity of a substance to that of water at 60oF (15.6 degrees C). Interchangeable with “heat capacity” in common usage.
Heat Exchanger A device for transferring heat from one fluid (liquid or gas) to another without mixing the two fluids.
Heat Pump Any device for moving heat from a low temperature source to a higher temperature use. In space conditioning applications specifically, a device for moving heat from a low temperature source to serve at a higher temperature in space heating
Heat Pump, Add On An air source heat pump using a fuel fired furnace for back-up during very cold weather
Heat Pump, Air Source Any space heating heat pump used for moving heat from low temperature outdoor air to serve the indoor heating load. The system is generally reversible to serve as a cooling system in hot weather.
Heat Pump, Water Source Any space heating heat pump used for moving heat from low temperature water stream to serve the indoor heating load. The system is generally reversible to serve as a cooling system in hot weather.
Heat Pump, Ground Source Any space heating heat pump used for moving heat from low temperature water stream which is receiving heat from the ground to serve the indoor heating load. The system is generally reversible to serve as a cooling system in hot weather.
Heating Seasonal Performance Factor (HSPF) A measure of a heat pump's energy efficiency over one heating season. It represents the total heating output of a heat pump (including supplementary electric heat) during the normal heating season (in Btu) as compared to the total electricity consumed (in watt-hours) during the same period. HSPF is based on tests performed in accordance with ARI Standard 210/240 “2003 Standard for Unitary Air-Conditioning and Air-Source Heat Pump Equipment.”
Internal Combustion Engine (ICE) (Pertaining to Engines) An engine in which the fuel is burned inside the engine itself, rather than in a separate device, such as a boiler on a steam engine.
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Nitrogen Oxides (NOx) Any chemical compound of nitrogen and oxygen. Nitrogen oxides result from high temperature and pressure in the combustion chambers of automobile engines and other power plants during the combustion process. When combined with hydrocarbons in the presence of sunlight, nitrogen oxides form smog. A basic air pollutant; automotive exhaust emission levels of nitrogen oxides are regulated by law.
Refrigerating System, Absorption A system where by a secondary fluid absorbs the refrigerant, and in doing so gives up heat, subsequently releasing the refrigerant, during which heat is absorbed.
Refrigerating System, Vapor Compression A refrigerating system in which the cooling effect results from expansion of a refrigerant after it has been mechanically compression by either centrifugal or reciprocating compressors.
Refrigeration Cycle The full sequence of condensation and evaporation. The heat driving evaporation is obtained from the material to be cooled.
Refrigeration Ton 12,000 Btu per hour or 200 Btu per minute of heat removal. Originally, the amount of heat required to melt a ton of ice in 24 hours.
Seasonal Energy Efficiency Ratio (SEER) This is a measure of equipment energy efficiency over the cooling season. It represents the total cooling of a central air conditioner or heat pump (in Btu) during the normal cooling season as compared to the total electric energy input (in watt-hours) consumed during the same period. SEER is based on tests performed in accordance with ARI Standard 210/240 “2003 Standard for Unitary Air-Conditioning and Air-Source Heat Pump Equipment.”
Single Package A single package unit is an ASHP or central air conditioner that combines both condenser and air handling capabilities in a single casing.
Space Conditioning The process of heating, cooling, humidifying, filtering, drying, deodorizing, or otherwise treating air in a room or building to maintain a specified temperature and/or humidity and to remove impurities.
Split System A split system is an ASHP or central air conditioner with separate indoor (evaporator) and outdoor (condenser) units. For split systems, the energy-efficiency rating of a particular split system is based on the actual condenser-evaporator coil combination of the split system.
Thermostat An automatic device actuated by temperature changes designed to control the gas supply to the burner(s) in order to maintain temperature between predetermined limits, and in which the thermal actuating element is an integral part of the device.
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