federal technology alert

8/14/2019 Federal Technology Alert

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FederalTechnology

Alert

A publication seriesdesigned to speed the

adoption of energy-

efficient and renewable

technologies in the

Federal sector Waste chill recovery (WCR) heatexchangers can be retrofit to commer-cial-size automatic ice makers toimprove the energy efficiency andcapacity of the ice maker. Residual

chilled water, normally sent down thedrain, is used to precool fresh makeupwater prior to operating the ice makersrefrigeration system.

This Federal Technology Alert(FTA), one in a series on newtechnologies, describes the theory ofoperation, energy-saving mechanism,and field experience for the technology,and presents a detailed methodology,including example case studies, forconducting a site-specific evaluation.

Energy-Saving MechanismWater charged to the ice maker must

first be cooled to the freezing pointbefore ice will form on the evaporatorplates. At the conclusion of the ice-making and harvesting cycle, part or allof the residual water, still at or near thefreezing point, is purged from the icemaker, and the reservoir is then refilledwith makeup water that is often muchwarmer. Some water must always bepurged because the ice-making processconcentrates impurities in the residualwater. If the impurity concentration is

allowed to grow, scale will eventuallyform on the equipment and/or the icecubes will become cloudy.

The objective of the WCR heatexchanger is to capture part of thechill otherwise lost with the purgewater by first absorbing energy from thecharge water. Reducing the temperatureof the water charged to the reservoirdirectly lowers the cooling load thatmust be served by the ice makers

Waste Chill Recovery Heat

Exchangers for Commercial-Size Automatic Ice MakersTechnology for Improving the Energy Efficiency and Increasing the

Capacity of Ice Makers

The U.S. Department of Energyrequests that no alterations bemade without permission in anyreproduction of this document.

refrigeration system and the electricityrequired to drive the refrigerationsystem.

Technology SelectionThe WCR heat exchanger is one of

many energy-saving technologies toemerge in the last few years. The FTAseries targets technologies that appearto have significant untapped Federal-sector potential and some existingfield experience. The WCR heatexchanger met these two criteria andwas selected for further review andevaluation via this FTA.

Potential BenefitsAs noted above, the direct benefit

of the WCR heat exchanger is to reducethe temperature of the water charged tothe ice makers reservoir, lowering thecooling load served by the ice makers


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refrigeration system and the electricityrequired to drive the refrigerationsystem. For ice makers with condenserslocated internal to the building, animportant secondary energy benefit alsoaccrues. Reducing the cooling load onthe ice maker reduces the heat rejectedby the ice maker to the building, whichreduces the building cooling load (orincreases the building heating load).

Because ice demand tends to be concen-trated during the summer and coolingloads tend to dominate heating loads incommercial buildings, the net effect isalmost always a reduction in a buildingsHVAC energy loads and energy requiredto drive the HVAC equipment.

Lowering the initial water tempera-ture in the ice makers reservoir alsoreduces the time required to cool thewater to the freezing point, whichreduces the entire ice making andharvesting cycle. In fact, the increasedproduction rate may be the most

valuable impact to users with inadequateice-making capacity who may otherwisebe forced to buy supplemental ice,purchase a supplemental refrigerationunit, or buy an additional ice maker. Inaddition, reducing the cooling load onthe ice maker should result in less wearand tear, resulting in lower mainte-nance costs and longer equipment life.

ApplicationThe cost-effectiveness of a WCR heat

exchanger is extremely site-specific; thepayback period could be less than 1 yearor greater than 100 years. The bulleteditems listed below summarize the keyfavorable conditions that will mostlikely result in a cost-effective applica-tion. Not all of these conditionsnecessarily need to exist for an applica-

tion to be cost-effective. Still, if themajority of these conditions do not exist,it is unlikely a WCR heat exchanger willbe cost-effective.

The annual demand for ice isrelatively high, generally greaterthan 30% of its annual productioncapacity, if operated continuouslythroughout the year.

The ice maker operates in a purgemode (as described in more detail inthe body of the FTA) to charge anddischarge its water reservoir.

The average annual makeup watertemperature is relatively high,generally greater than 60F.

The ice makers condenser is locatedindoors.

The electricity rate is relatively high,generally greater than $0.08/kWh.

Field ExperienceThe WCR technology is being used

successfully in a wide range of commer-cial applications, including hotels,restaurants, convenience stores, andschools. Although few ice machineshave been separately metered, the end-user representatives we spoke withindicated an observable decrease incycle time, indicating a lowering of inle

water temperature. Where test measure-ments were collected, the WCR technol-ogy reduced inlet water temperature byan average of 15.2F, or 21.9%. Iceproduction cycle times were reduced by2.1 minutes, on average, or 18.1%.

Technology OutlookWCR heat exchangers for commer-

cial-sized automatic ice makers arecurrently cost-effective in selectedapplications. Several factors influencecost-effectiveness, as summarizedabove. The thermal efficiency of currentWCR heat exchangers seems adequate.Assuming that scaling remains a non-problem, the key characteristic thatcould be improved is first cost. Hope-fully, mass production economies-of-scale and/or competition from multiplevendors will result in lower equipmentcosts in the future. Customer interestmay also spark more interest on the partof ice maker manufacturers to offerWCR heat exchangers as part of theoriginal equipment.


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ContentsAbstract........................................................................................................................... 1About the Technology .................................................................................................... 3

Application Domain.............................................................................................. 3Energy-Saving Mechanism................................................................................... 4Other Benefits ....................................................................................................... 4Variations .............................................................................................................. 4Installation............................................................................................................. 4

Federal Sector Potential.................................................................................................. 4Estimated Savings and Market Potential .............................................................. 4Laboratory Perspective.......................................................................................... 5

Application ..................................................................................................................... 5Application Screening........................................................................................... 5Where to Apply..................................................................................................... 8Maintenance Impact.............................................................................................. 8Equipment Warranties........................................................................................... 8Codes and Standards............................................................................................. 8Costs...................................................................................................................... 8

Utility Incentives and Support........................................................................................ 9Technology Performance................................................................................................ 9

Field Experience ................................................................................................... 9Energy Savings...................................................................................................... 9Maintenance .......................................................................................................... 9Environmental Impacts ......................................................................................... 9

Case Studies.................................................................................................................... 9Facility Data.......................................................................................................... 10

Ice Maker and WCR Heat Exchanger Data.......................................................... 11Energy Savings...................................................................................................... 12Life-Cycle Cost..................................................................................................... 12

The Technology in Perspective....................................................................................... 13The Technologys Development ........................................................................... 13Technology Outlook.............................................................................................. 13

Manufacturers ................................................................................................................. 16Who is Using the Technology ........................................................................................ 16For Further Information.................................................................................................. 16

Trade Associations ................................................................................................ 16User and Third Party Field and Lab Test Reports ................................................ 16Patents ................................................................................................................... 16References............................................................................................................. 16

Appendixes

Appendix A - Federal Life-Cycle Costing Proceduresand the BLCC Software................................................................. 18

Appendix B - Life-Cycle Cost Analysis Summary:Energy Conservation Investment Program..................................... 19


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About the TechnologyA waste chill recovery (WCR) heat

exchanger could be applied to any icemaker to improve its energy efficiency.The WCR device is basically a type ofshell and tube heat exchanger thatprecools makeup water being chargedto the ice maker with cold waste waterbeing discharged from the ice maker.A simplified, generic flow diagram of theconcept is shown in Figure 1. Relativelywarm makeup water flows through thetube while the near-freezing waste water

flows around the tube within the shell ofthe heat exchanger. Heat is transferredfrom the makeup water to the dischargewater, which lowers the temperature ofthe water charged to the ice makersreservoir. As a result, the amount of heatthat must be removed from the water bythe ice makers refrigeration system isreduced along with the electricityrequired to drive the refrigeration system.

The effectiveness of the heat exchanger(i.e., its ability to transfer heat from themakeup water to the discharge water)depends on the amount of heat transfer

surface area (tubing surface area) relativeto the amount of heat being transferredand the layout of tubing and flow channels

within the heat exchanger shell. Increas-ing heat transfer surface area enhancesheat exchanger effectiveness, butincreases its size, weight, and cost. Acounterflow layout that minimizes thetemperature difference between the twofluid streams at any point along thetubing (imagine a smaller pipe [thetubing] within a larger pipe [the shell],with the makeup water entering thesmaller pipe at one end and the dischargewater entering the larger pipe at the otherend) is best for heat transfer, but canresult in a cumbersome or complex and

costly design.The design variations are practically

endless; cutaway drawings of two WCRheat exchangers currently offered forapplication to commercial ice makers(machines with an ice-making capacityranging from a few hundred to a fewthousand pounds per day) are shown inFigures 2 and 3.

Application DomainCurrently, about 5,000 WCR heat

exchangers have been installed oncommercial ice makers, but only a few

of these have been in Federal facilities.The current stock of commercial icecube-making machines (not including

flake-ice machines) isreported to be approxi-mately 1.2 million in theU.S. (A.D. Little 1996),with about 1.5% of theseestimated to exist in theFederal sector. Whetheror not these unitsrepresent cost-effectiveapplications depends on

several site-specific

( a)

and machine-specific( b)

characteristics.Each of these andadditional factors arediscussed in more detaillater in this FTA.

Fast Ice Products,Inc. and Maximicer

Foodservice are the only firms known tooffer WCR heat exchangers as auxiliarycomponents for the equipment originallysupplied by the ice maker manufacturers.

Similar devices are not currently offeredby the ice maker manufacturers them-selves as either a standard or optionalfeature, but Manitowoc plans to offer theMaximicer WCR heat exchanger as anaccessory through its distributors in thenear future.Figure 1. WCR Heat Exchanger Concept

Figure 2. Maximicer WCRHeat Exchanger

Figure 3. Fast Ice WCR Heat

Exchanger

(a) For example, the demand for ice, makeup water temperature, and electricity rate.(b) For example, water consumption per pound of ice, water charge and discharge approach, and refrigeration efficiency.


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Energy-Saving MechanismAlthough ice is made from potable

water, the water still contains variousimpurities at different concentrationsdepending on the source. Commonimpurities include sodium, calcium,magnesium, and iron, which occur inthe form of salts. In addition to thesedissolved solids, the water may containvarious suspended solids and microscopic

organisms. The process of freezing watertends to concentrate the impurities in thewater, resulting in ice that is purer thanthe original water. In particular, iceformed relatively slowly or by thecontinuous washing of the ice interface(the technique employed in cube icemakers) results in the purest andclearest product.

While clarity is a highly desirable iceattribute, the resulting concentration ofimpurities in the residual water willeventually cause precipitation andequipment scaling if allowed to growunchecked. Thus, a portion of the watercharged to an ice-making machine iscontinuously and/or periodically dis-charged to keep the impurities within atolerable level. The problem is similarto that encountered in an evaporativecooling tower, where impurities areconcentrated in the residual water notevaporated. In an evaporative coolingtower, blowdown is the term used todescribe water continuously or periodi-cally purged to control impurityconcentration.

Water charged to the ice maker mustfirst be cooled to the freezing pointbefore ice will form on the evaporatorplates. At the conclusion of the ice-making and harvesting cycle, part or allof the residual water, still at or near thefreezing point, is purged from the icemaker and the reservoir is then refilledwith makeup water that is often muchwarmer. The objective of the WCR heatexchanger is to capture part of the chillotherwise lost with the purge water byfirst absorbing energy from the chargewater. Reducing the temperature of the

water charged to the reservoir directlylowers the cooling load that must beserved by the ice makers refrigerationsystem and the electricity required todrive the refrigeration system.

For ice makers with condenserslocated internal to the building, animportant secondary energy benefit

also accrues. Reducing the cooling loadon the ice maker reduces the heat rejectedby the ice maker to the building, whichreduces the building cooling load (orincreases the building heating load). Icedemand tends to be concentrated duringthe summer and cooling loads tend todominate heating loads in commercialbuildings. Thus, the net effect is almostalways a reduction in a buildings HVAC

energy loads and energy required to drivethe HVAC equipment. Either the primary(ice maker) or secondary (HVAC) energysavings can be greater, depending on theefficiency of the ice maker and HVACequipment.

Other BenefitsLowering the initial water temperature

in the ice makers reservoir reduces thetime required to cool the water to thefreezing point, which reduces the entireice making and harvesting cycle. In fact,the increased production rate may be

the most valuable impact to users withinadequate ice-making capacity who mayotherwise be forced to buy supplementalice, purchase a supplemental refrigerationunit, or buy an additional ice maker. Inaddition, reducing the cooling load onthe ice maker should result in less wearand tear, resulting in lower maintenancecosts and longer equipment life.

VariationsAs noted above and illustrated by

Figures 2 and 3, the design approachesfor constructing a WCR heat exchangerare nearly endless. The Fast Ice unitconsists of a flat spiral of tubing withina rectangular shell. The Maximicerconsists of a cylindrical shell withinanother cylindrical shell, with a helicalspiral tube contained within the outershell and a straight tube contained withinthe inner shell. The counterflow designof the Maximicer unit should result inbetter heat exchange between the twofluids, but its purchase price is greaterthan the Fast Ice unit as well.

A comparison of these two or any

other WCR heat exchangers mustconsider the expected reductions inreservoir water temperature and thebenefits derived (e.g., reduced electricityconsumption, increased ice-makingcapacity) from the reduced temperatures,as well as the initial costs of the units.

At the time this FTA was written,comparison testing of the two units,under the same operating conditions,was not known to have been com-pleted, so conclusive judgmentsregarding their relative performanceshould not be made.

InstallationBoth the Maximicer and Fast Ice heat

exchangers are compact devices designedto fit behind, adjacent, or underneath theice maker and its storage bin. Retrofit isrelatively simple because the interfaceoccurs outside of the ice maker andstorage bin walls. Either unit requiresfour connections; both supply anddischarge water lines are cut and re-plumbed to route each line through theheat exchanger. The discharge lineentering the heat exchanger and thesupply line leaving the heat exchangershould be insulated to prevent warmingof the chilled water and potential water

condensation on the outside of the tubing.

Federal SectorPotential

The WCR heat exchanger technologyhas been assessed by the New Technol-ogy Demonstration Program (NTDP) ashaving significant potential for energysavings in the Federal sector.

Estimated Savings and

Market PotentialPotential applications for the WCRtechnology presented in this documentare any locations where commercial-sizeice machines are found. In the Federalsector, these are found in cafeterias,kitchens, dorm-style housing, mess halls,and similar facilities.

As part of the NTDP selection process,technologies are screened to estimatetheir potential market impact in theFederal sector. For buildings-relatedtechnologies, the screening utilizes amodified version of the Facility Energy

Decision Screening (FEDS) model( a)to capture all system interaction andsecondary benefits of applicable tech-nologies. The screening for the WCRtechnology used the economic basisrequired by 10 CFR 436 and includedthe number, annual usage, and lifeexpectancy of ice machines in the Federal

(a) Developed for the Department of Energys Office of Federal Energy Management Program (FEMP), the U.S. Army Construction EngineeringResearch Laboratories (CERL), and the Naval Facilities Engineering Service Center (NFESC) by the Pacific Northwest National Laboratory(PNNL).


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sector. Potential technologies are rankedaccording to ten different criteria. Thefirst three criteria are financial: netpresent value, installed cost, and presentvalue of savings. The next rankingcriterion is annual site energy savings.Finally, technologies are ranked on theirreduction of SO2, NOX, CO, CO2,particulate matter, and hydrocarbonemissions.

The ranking results from the screeningprocess for this technology are shown inTable 1. These values represent themaximum benefit achieved by imple-menting the technology in every Federalapplication where it is considered cost-effective. The actual benefit will belower because not every possibleinstallation could be expected to berealized.

Laboratory PerspectiveThe results of laboratory and field

testing show that WCR technology offersthe potential for improving ice makingcapacity and/or reducing energy con-sumption. Cost-effectiveness, however,depends on several site-specific andmachine-specific variables. This FTAdiscusses in detail the variables affectingperformance, such as equipment charge/

discharge cycle, makeup water tempera-ture, and ice-making load.

ApplicationThis section discusses in more detail

the issues that must be considered indetermining whether or not to install a

WCR heat exchanger on an ice maker.Several site- and machine-specificcharacteristics have a significant bearingon the effectiveness of the WCR device.The variation in these characteristicsresults in some applications beingexceptionally attractive, while othersoffer practically no benefit at all. In-cluded here are general rules of thumbabout what to look for and what to avoid,

descriptions of installation and mainte-nance requirements, and information onequipment warranties, costs, and utilityprograms.

Application ScreeningThe direct objective of the WCR heat

exchanger is to reduce the temperatureof the water charged to the ice makersreservoir. Quite obviously, the refrigera-

tion system willrequire less electricityto make ice from 50Fwater than it would

from, say, 70F water.Reducing the coolingload also decreasesthe time required togenerate a batch ofice, thus increasingthe ice productionrate. In addition,for machines withcondensers internalto the building, lessheat is rejected tothe building, which

lowers the spacecooling load.( a)

Further discussion of the factors influenc-ing the effectiveness of a WCR heatexchanger can be facilitated by examin-ing each variable in the followingequations defining the potential energyand dollar savings.

IM Energy Savings = lb ice * lbH2O/lb ice * DT * Cp * 1/COPim

* kWh/3413 Btu (1)IM Dollar Savings = IM Energy

Savings * $/kWhim (2)

whereIM = ice makerlb ice = pounds of ice producedlb H2O/lb ice = pounds of water

charged per pound of ice produced

DT = reduction in inlet watertemperature achieved with WCRheat exchanger

Cp = the heat capacity of waterCOPim = the coefficient of

performance( b) for the ice makerkWh/3413 Btu = the conversion factor

equating kWh and Btu$/kWhim = the value of ice maker

electricity savings

IM Energy Rejection Reduction(IMERR) = (lb ice * lb H2O/lb ice *

DT * Cp) * (1 + 1/COPim) (3

Cooling System EnergySavings (CSES)

= IMEER/COPac*kWh/3413 Btu (4

where COPac = cooling system coeffi-cient of performance

Cooling System Energy DollarSavings = CSES * $/kWhac (5

where $/kWhac is the value of coolingsystem electricity savings

Heating System Energy Penalty(HSEP) = IMEER/effh (6

where effh = heating system efficiency

Heating System Energy DollarPenalty = HSEP/1,000,000 *

$/MMBtu (7

where $/MMBtu = heating system fuelcost

ice production (lb ice)The first question to consider is the

quantity of ice being produced. If theice maker is used very little, the energysavings will be too small to justify aninvestment in a WCR heat exchanger.On the other hand, an ice maker thatoperates continuously, or nearly so, is agood candidate. Although there is noabsolute minimum, machines with anannual capacity factor (the ratio of actual

annual ice production to the amount ofice that would be produced if the machineoperated continuously during every hourof the year) less than 30% are unlikely tobe economically attractive applicationsbased on energy savings alone, unless

(a) Conversely, reducing the amount of heat rejected to the building increases the space heating load, but more ice is generally produced during thecooling season, so the net benefit of this impact is usually positive.

(b) Actually, the ratio of total thermal load, including all sources of heat that must be rejected by the ice maker, to the sum of electric energy input tothe compressor, condenser fan, and water pump during the ice-generation mode, with thermal load and electricity input measured in the sameunits.

Table 1. New Technology Demonstration ProgramScreening Results

Screening Criteria Value Result

Net Present Value ($) 4,766,672Installed Cost ($) 4,903,310Present Value of Savings ($) 9,636,982Annual Site Energy Savings (MBtu) 36,309SO2 Emissions Change (lb/yr) 135,959NOX Emissions Change (lb/yr) 50,743CO Emissions Change (lb/yr) 2,839CO2 Emissions Change (lb/yr) 8,283Particulate Emissions Change (lb/yr) 7,813Hydrocarbon Emissions Change (lb/yr) 415


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compensated by relatively attractivevalues for the other variables inequations 1-7.

water charging ratio(lb H2O/lb ice)

The next factor in the energy savingsequation is the amount of water chargedto the reservoir per unit of ice produced.This ratio is greater than one because partof the ice formed on the evaporator platesis melted during the defrost cycle (andnot included as part of the ice production)and there must be enough residual waterleft in the reservoir to avoid the precipita-tion of impurities concentrated by thefreezing process.

It is important to note that the ratio ofwater charged to the reservoir per unitof ice may be less than the ratio of totalwater consumed per unit of ice, depend-ing on how the reservoir is charged anddischarged. Some machines purge all of

the water remaining in the reservoir atthe conclusion of the ice harvesting cycleand then refill the reservoir to a fixedlevel prior to starting the next ice-makingcycle. For this charge and dischargemode, the two ratios are the same.

Other machines charge the reservoirwith fresh water for a period of time(may be fixed or adjustable by the user),mixing new water with old water, andallowing the mixture to overflow towaste for part of the charging period tocontrol the concentration of impurities.The two mechanisms are combined on

some machines with the user able toselect the purge frequency (every third orfifth or seventh cycle, for example). Foroverflow and overflow/purge hybridcharge and discharge modes, the totalwater consumed per unit of ice is greaterthan the reservoir charge per unit of ice.All else equal, machines with higherratios of water charged to the reservoirper unit of ice will benefit the most froma WCR heat exchanger. However, thisratio tends to range between 1.2 and 1.8(A.D. Little 1996), so it is not a signifi-

cant distinguishing factor. More impor-tantly, all else is not usually equal, as willbe discussed next.

reduction in inlet watertemperature (DT)

The reduction in inlet water tempera-ture achieved with a WCR heat ex-changer is the key variable for determin-ing the cost-effectiveness of the concept.Not only does this variable represent the

most important direct impact of using aWCR heat exchanger, but the magnitudeof this factor varies significantly depend-ing on the makeup water temperature,the type of ice maker, and ice makeroperating settings.

The variation of reservoir watertemperature reduction with makeup watertemperature is illustrated in Figure 4 forManitowoc, Cornelius, and Hoshizaki ice

makers equipped with a Maximicer WCRheat exchanger (similar data were notavailable for the Fast Ice WCR heatexchanger). These data were recordedfor various types of ice makers, repre-senting different water charging anddischarging design modes and, presum-ably (but not documented), differentoperating settings. As described in theprevious paragraph, there are three basicwater charging and discharging designs:purge, overflow, and the purge/overflowcombination.

The principal consideration indesigning the water charging anddischarging mechanism for ice makers isto inhibit precipitation of impurities andmaintain high quality (clear) ice. Energyconservation is of secondary importance.Unfortunately, improving ice quality and

reducing the potential for impurityprecipitation generally increasesenergy consumption and vice versa.

Makeup water quality varies signifi-cantly from one site to the next, so mostice makers have adjustment mechanismsthat vary the amount of water consumedper unit of ice production. For example,the amount of water charged to thereservoir is usually adjustable in purge-

type machines. For overflow machines,the reservoir filling (hence, overflowing)period is adjustable. For purge/overflowmachines, the frequency of purging (iceharvesting cycles/purge) is adjustablealong with the reservoir filling period.

Therefore, energy consumptioncan be reduced simply by adjusting thereservoir charging volume, reservoirfilling period, and/or purge frequency

down. Reducing water consumptionruns the risk of causing impurityprecipitation and/or cloudy ice cubes,however, so caution is advised. On theother hand, if the current settings areconservatively set for the makeup waterquality at a specific site, changing theequipment settings to reduce waterconsumption is a simple way to saveenergy (and water) without investingin additional hardware.

Another option would be to removesome of the impurities prior to introduc-

ing the makeup water to the ice maker(e.g., via a water softener). This wouldallow less water and energy consumptionand is commonly employed as part ofindustrial ice-making systems, but iscost-prohibitive for individualcommercial ice makers.

In general, WCR heat exchangers willhave the greatest impact (potential loadreduction and energy savings) for purge-type ice makers. For these types ofmachines, all the water (near freezing)remaining at the end of an ice-makingcycle is purged from the reservoir,resulting in a significant loss of chillthat could be partly reclaimed by heatexchange with the makeup water.

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

60.0 65.0 70.0 75.0 80.0 85.0

Makeup Water Temperature, F

WaterTemperatureReduction,

F

Manitowo

Cornelius

Hoshizak

Figure 4. Maximicer Makeup Water Temperature Reduction


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For overflow-type ice makers,estimating the chill loss with or withouta WCR heat exchanger is more compli-cated. During the harvest cycle, makeupwater is not first purged (drained) fromthe reservoir prior to filling the reservoir.Rather, makeup water is added directlyto the residual water left in the reservoir.Makeup water is added until the mixtureof residual water and makeup water

overflows the reservoir for an adjustableperiod of time. Thus, much of thechill contained in the residual wateris captured in the reservoir, althoughthe overflow water is still cooler thanthe makeup water. As the filling/overflow period is lengthened, morechill is lost, and the reservoir watertemperature approaches the makeupwater temperature.

Adding a WCR heat exchanger to anice maker with an overflow type of watercharging and discharging system has thefollowing impacts. Significantly less

chill is recovered compared with apurge-type ice maker because thedischarge water is not nearly as cold.In fact, for longer overflow periods, therewould be no benefit at all, because thereservoir/discharge water approachesthe temperature of the makeup water.However, adding the WCR heat ex-changer increases the pressure drop onthe inlet line, which reduces the flowrate into the reservoir, which reduces theamount of water overflowing to dischargefor a fixed refill/overflow period.

Thus, for an overflow-type ice maker,a portion of the energy savings benefitaccrues simply because the overflowvolume per cycle is reduced and notbecause the makeup water is pre-cooledin the heat exchanger. These savingsare taken at the risk of increasing thechances of impurity precipitation and/orreducing ice cube quality. As might beexpected, the impacts described abovefor purge and overflow-type ice makersare combined for the hybrid purge/overflow ice makers. As a result, onewould expect the WCR heat exchanger

to work best with purge-type ice makers,worst with overflow-type ice makers,with intermediate outcomes for thehybrid-type ice makers.

ice maker performance (COPim)The coefficient of performance for

the ice maker translates the reduction incooling load into the reduction in electricload. Ice maker performance is morecommonly described in terms of kWh

per unit of ice production rather than byits system COP, although the latter canbe readily calculated from the formerfor a given makeup water temperature.Unfortunately, the standard coolingsystem COP is not the correct figureto use in equations 1 and 3. In general,cooling system COP is defined as theratio of the cooling duty sought (convert-ing makeup water into ice for ice makers)

to electrical energy input, with bothnumerator and denominator energiesmeasured in the same units. The cool-ing duty sought includes only the energyremoval required to cool water from itsmakeup temperature to freezing andto accomplish the phase change. Noparasitic thermal loads (e.g., coolingof water that is discharged, melting aportion of the ice formed, heating ofthe evaporator plates during defrost)are included in the numerator, althoughtheir impact is implicitly included in thedenominator as the refrigeration system

must operate to remove the parasiticthermal loads as well as the coolingduty sought.

Reducing the reservoir water tempera-ture not only reduces the cooling dutysought, but reduces the parasitic thermalloads as well (specifically, the coolingof water that is discharged). Thus, thecorrect COP to use in equations 1 and 3is the ratio of total thermal load (coolingduty sought plus thermal parasitics toelectric energy input (compressor plusfan plus water pump) during the ice-

making mode. Compressor energy inputduring the ice harvesting or defrost modeis not included in the denominator as thisenergy input is not affected by changingthe total thermal load. In short, reducingthe water temperature charged to thereservoir reduces electrical energyconsumption during the ice-makingmode in proportion to the reduction intotal thermal load. Unfortunately, thispeculiar definition of COP (i.e., COPim)is not readily available from manufactur-ers. Fortunately, detailed thermal andelectric load estimates presented in A.D.

Little (1996) for a typical ice makershow COPim to be about 1.7.

value of ice maker electricitysavings ($/kWhim)

Variation in site-specific electricityrates will certainly have a significantimpact on the dollar savings achievedwith a WCR heat exchanger and couldeasily make the difference between beinga cost-effective investment or not. In

general, $/kWhim should only includeelectricity energy charges and not theaverage $/kWh impact of electricitydemand charges. For an individual icemaker, demand savings are likely to be ator near zero. In general, the WCR deviceworks to reduce the ice harvesting cycletime rather than reducing its peak powerdemand. While demand will be reducedat the onset of the ice-making cycle as a

lower water temperature in the reservoirtranslates into a lower head pressure forthe compressor, the peak demand for thecycle usually occurs during defrost, andwould not be affected by the WCRdevice.

cooling and heatingsystem performance(COPac and effh)

For ice makers with condensersinternal to the building, an importantsecondary impact occurs. All heat

rejected from the ice maker to thebuilding must be removed by thebuildings cooling system during thecooling season. Cooling system COPsgenerally range from about 2 to 3,although window units can be poorerand larger centrifugal chiller systemscan be better (Colen 1990). Therefore,assuming a value of 2.5 for COPac isreasonable if a better estimate is notavailable.

Conversely, heat rejected from theice maker during the heating season neednot be supplied by the buildings heatingsystem. Installation of the WCR devicereduces the ice makers cooling load perlb of ice, which directly reduces theamount of heat rejected to the building.As the demand for ice is generally higherduring the cooling season than during theheating season, this secondary impactgenerally results in additional dollarsavings which should be attributed tothe WCR device. During the coolingseason, equations 3, 4, and 5 apply, whileequations 3, 6, and 7 apply during theheating season. As for cooling systems,

heating system efficiency (effh) dependson system type, but will usually bebetween 70% and 90%. A value of 80%is suggested, if no better estimate isavailable.

value of cooling system electricitysavings ($/kWhac)

In addition to electricity energysavings, electricity demand savings seemmore likely to occur for the cooling


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system than for the ice makers. Peakbuilding electric demands are drivenby space cooling loads, which, like icemaking demand, is driven by warmweather. Thus, reduced heat rejectionfrom ice makers, the resulting reductionin cooling equipment electrical demands,and peak building electrical demands areall likely to coincide.

The path for demand reduction does

not occur at a single electrical appliance,which is usually either on or off ratherthan operating at part load, but fromintegration over a large number of units.The reduced thermal load served by asingle cooling system unit will not resultin a lower peak demand, but a reductionin the amount of time the unit operatesduring the peak demand period. Inte-grated over a number of cooling systemunits (perhaps in a number of buildings)served by a single meter, the effect is areduction in peak demand that is propor-tional to the reduction in peak heat

rejection. Thus, the effect of demandcharges on the average cost of electricityshould be included in $/kWhac.

(a)

In summary, for most situations, therewill likely be more cooling system unitsthan ice makers served by a singleelectric meter. In addition, certain icemaker applications, such as food service,seem more likely to result in simulta-neous ice maker operation during thepeak demand period. Therefore, demandcharge reductions seem more likely toaccrue from multiple cooling system

units than from multiple ice makers.If space cooling is provided by a non-electric technology, such as absorptionchillers, then equations 4 and 5 would bemodified to calculate energy savings inMMBtu and dollar savings based onenergy savings and the value of energy in$/MMBtu. Similarly, equations 6 and 7would be modified to look like equations4 and 5 for electrically driven spaceheating systems.

Where to ApplyThe previous section described and

discussed the key factors affecting thecost-effective application of WCR heatexchangers to ice makers. The bulleteditems listed below summarize the keyfavorable conditions that will most likelyresult in a cost-effective application.Not all of these conditions necessarilyneed to exist for an application to becost-effective. Cost-effectivenessdepends on the specific values of the

variables identified in equations 1-7.Still, if the majority of these conditionsdo not exist, it is unlikely a WCR heatexchanger will be cost-effective.

The annual demand for ice is rela-tively high, generally greater than30% of its annual production capacity,if operated continuously throughoutthe year.

The ice maker operates in a purgemode (as described above) to chargeand discharge its water reservoir.

The average annual makeup watertemperature is relatively high, gener-ally greater than 60F.

The ice makers condenser is locatedindoors.

The electricity rate is relatively high,generally greater than $0.08/kWh.

Maintenance ImpactWCR heat exchangers are passive

devices with no moving parts that aredesigned to operate maintenance free.The principal concern is that the internalheat exchanger surfaces may becomefouled with impurities that precipitateout of the discharge water. In theory,there is some cause for concern. Thecommon carbonates that cause scalingproblems are less soluble in warmerwater than colder water. Thus, as

impurities are concentrated in thedischarge water, warming the dischargewater in the WCR heat exchanger willincrease the probability of precipitation.

Retrofit of a WCR heat exchangerinto an overflow-type ice maker increasessupply line pressure drop, which de-creases the supply flow rate and theamount of discharge water that over-flows. This will further concentrateimpurities in the discharge water andincrease the odds of precipitation. Tominimize the chances of precipitation,consider a WCR heat exchanger that

incorporates plastic components at theheat exchangers inlet and outlet toeliminate stray electric currents thatotherwise enhance scaling.

The odds of incurring scaling prob-lems are more strongly associated withlocal water chemistry and water con-sumption settings on the ice maker thanwith the WCR device; none of the currentusers contacted indicated any scaling

problems with their WCR heat exchang-ers. Still, warming the discharge watercan only increase the chances of formingprecipitate. Some passive cleaning of theheat exchanger may occur in conjunctionwith periodic active cleaning of the icemaker and storage bin surfaces, ascleaning chemicals are washed throughthe heat exchanger. Further experiencewith WCR heat exchangers will need to

be accumulated to better predict actualmaintenance requirements.

Equipment WarrantiesMaximicer will refund the customers

purchase price within 6 months ofinstallation should the customer bedissatisfied with their WCR heat ex-changer for any reasonif the customerreturns the unit to Maximicer. TheMaximicer heat exchanger is warrantedagainst any defects in materials orworkmanship for 5 years after installa-tion. Fast Ice also offers a 5-year

warranty against any defects in materialsand workmanship.

Codes and StandardsThe following standards apply to ice

makers and (presumably) to WCR heatexchangers applied to ice makers.

National Sanitation FoundationStandard 12, Automatic Ice MakingEquipment.

Underwriters Laboratories, Inc.Standard 563-84, Ice Makers.

Air-Conditioning and RefrigerationInstitute Standard 810-79,AutomaticCommercial Ice Makers.

ASHRAE Standard 29-78, Method ofTesting Automatic Ice Makers.

Plumbing codes, such as the Interna-tional Plumbing Code, will address theconnection of WCR heat exchangers tothe potable water supply and the dis-charge of purge water to the building

sanitary drainage system and will applyas adopted by various agencies.

CostsThe purchase prices for Maximicer

WCR heat exchangers are $400, $500,and $600 for ice makers with dailyproduction capacities up through 450 lb,from 500 through 1,000 lb, and from

(a) A more accurate approach would be to directly estimate the demand and demand charge reduction, but this approach would require hour-by-houror similar modeling that was judged to be more complex than justified for the relatively small investment represented by a WCR heat exchanger


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1,100 through 3,000 lb, respectively.Fast Ice offers a single WCR heatexchanger at a price of $395. Ratherthan offer multiple sizes of WCR heatexchangers, Fast Ice suggests thefollowing installation strategies fordifferent capacity ice makers. For float-control, water-filling machines with adaily capacity of 1,200 lb or less, theFast Ice WCR heat exchanger should be

hooked up to both sump and ice storagebin drains. For solenoid-control water-filling machines and all machines witha daily capacity greater than 1,200 lb,only the ice storage bin drain should behooked up. Installation is expected totake a refrigeration technician or equiva-lent personnel from 1-2 hours, resultingin a charge of about $50.

Utility Incentives and

SupportTennessee Valley Authority, Madison

Gas and Electric, and Southern CaliforniaEdison have or plan to conduct tests onthe Maximicer WCR heat exchangers.However, no specific incentives aimed atWCR heat exchangers were identified.

Technology

PerformanceApproximately 5,000 WCR heat

exchangers had been installed as ofmid-1997, with all but a few beinginstalled in non-Federal applications.

Technology performance experiencedby users and independent testers isdescribed below.

Field ExperienceThe WCR technology is successfully

being used in a wide range of commercialapplicationshotels, restaurants, con-venience stores, and schools. Althoughfew ice machines are separately metered,all the sites we spoke with indicatedan observable decrease in cycle timeindicating a lowering of inlet watertemperature. Where test measurementswere performed, the Maximicer WCRtechnology reduced inlet water tempera-ture an average of 15.2F or 21.9%. Thecycle times were reduced by 2.1 minutes,on average, or 18.1%.

The most extensive independent fieldtest was performed by the TennesseeValley Authority (TVA) using aMaximicer WCR heat exchanger ona Manitowoc Series 600 ice machinelocated at the Wall Street Deli, Kirklin

Building, Birmingham, Alabama. Theice machine was monitored for fiveperiods ranging from 6 to 8 days each.During two time periods, the machinewas operated without the WCR deviceand during the other three the machinewas switched to the WCR device.

TVA reported that the ice machineaveraged 18.0 kWh/day in normaloperation and 12.4 kWh/day with the

Maximicer WCR devicea savings of30.5%. We can extrapolate yearlysavings from the daily savings of 5.5kWh/day. If the electric rate is $0.10/kWh, the WCR device would save $198/year in energy costs. While these resultsare good, one of the monitoring periodswith the WCR device operating extendedover the Thanksgiving holiday and it wasnot apparent that any attempt was madeto normalize for a decreased ice demandover the holiday. Therefore, the savingsreported may be slightly higher thanexpected.

Another field test was performed byMadison Gas and Electric Companyof Madison, Wisconsin. MaximicerWCR devices were installed on two icemachines in a newly constructed motel.The ice machines were individuallymetered with totalizing kWh meters andoperated for several weeks during latespring 1996. The study showed thatoperating under similar conditions, aWCR device would save approximately25% in energy costs, or about 1,600kWh/year.

Although the motel management waspleased with the technical performance ofthe device, they were unable to economi-cally justify purchasing additional units.A savings of $86/year (at $0.054/kWh)produces a payback of 5.8 years. Thelow cost of electricity and the low citywater temperature (as low as 45F in thewinter) hinder the implementation of theWCR technology for the Madison region.The energy savings will likely be lessduring the winter when ice demand isreduced and the incoming water tempera-ture is lower.

Currently, a detailed monitoring studyis being performed by Southern Califor-nia Edison (SCE). However, results werenot yet available as this FTA was beingprepared. The reader should contactSCE directly for the results of this study.

Energy SavingsAs previously indicated, the field

experience has shown energy savingsranging from 10% to 30%. The energysavings for a particular installation willvary widely depending on many factors,

including the inlet water temperature(which varies between regions andmunicipalities), ice machine design, icemachine location, demand for ice, andphysical location of waste heat exhaust.In general, the WCR device shows themost potential in warmer climates orwhere municipal water temperaturesare higher.

The maximum energy savings will

be achieved on a machine that is used toproduce the same amount of ice and isable to run for a shorter period in doingso. However, if the reduced run-timeallows the machine to produce more icein the same amount of time (i.e., in-creased ice demand), a portion of theenergy savings will be traded for addi-tional ice production. The reduction inenergy consumption per pound of iceproduced will be the same in eithercase, of course.

MaintenanceThe are no routine maintenance

requirements for the WCR technology.The life expectancy of the technology isgreater than the life expectancy of anyice machine on which it would beinstalled. The main concern for this orany heat exchanger is the affect foulingand mineral deposits have on the heatexchanger efficiency. The water drainedfrom the sump at the end of the coolingcycle has a high concentration of impuri-ties. The heat exchanger coils in theMaximicer WCR devices are electrostati-

cally isolated to prevent weak electricalcurrents, which facilitate the precipitationof calcium carbonate and other minerals.

Environmental ImpactsThere are no negative environmental

impacts associated with the WCRtechnology. The device is made ofvarious plastics and polymers, coppertubing, and/or stainless steel, dependingon the manufacturer. It has no activeelectronics and can be disposed ofthrough normal trash pickup. In condi-tions where it saves energy and increases

the capacity of ice machines, it providessecondary environmental benefitsstemming from reduced electricity input,hence reduced emissions at electricitygenerating plants.

Case StudiesTwo example case studies are pre-

sented in this section to illustrate howthe cost-effectiveness of a WCR heatexchanger should be evaluated. The first


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case assumes the ice maker condenser islocated indoors; the second case assumesthe ice maker condenser is locatedoutdoors. The data presented do notrepresent any site-specific situation, butare intended to represent realisticconditions that could possibly occur.The results should not be taken asevidence that a WCR heat exchangeris generally cost-effective or not; rather,

the cases are only intended to provideinstruction on how to evaluate the cost-effectiveness of a potential application.

In general, energy savings are deter-mined by exercising equations 1-2 for icemakers with condensers located externalto the building or equations 1-7 for icemakers with condensers located internalto the building. The accuracy of theanalysis can be varied by exercising theequations over different time periods. Anhour-by-hour annual evaluation wouldprovide the most accurate assessment ifaccurate hourly data are available for all

inputs, but such is not likely the case.On the other hand, an annual averageevaluation minimizes data requirements,but may not yield the desired accuracy.The generally recommended approach,described here, is based on input data foraverage monthly conditions. Thus, thedata requirements listed below need to bespecified for each month of the year. Forseveral of the variables, a single annualaverage value may be used for eachmonth if monthly variation is unknownand likely to be minimal. Default

assumptions are presented for variablesof lesser importance that may be difficultto define. Default assumptions are notprovided for the more important variablesthat must be defined to allow an ad-equately accurate evaluation.

Facility DataThe following facility-related data

are required to determine WCR heatexchanger cost-effectiveness:

makeup water temperature, F

electricity rate, $/kWh, based onenergy charges only

electricity rate, $/kWh, based onenergy and demand charges

fossil fuel or steam rate, $/MMBtu

cooling system coefficient of perfor-mance (COP)

heating system efficiency or COP

space conditioning mode, heating orcooling.

Only the makeup water temperatureand electricity rate based on energycharges need to be specified whenevaluating ice makers with externalcondensers.

makeup water temperatureMakeup water temperature is a key

variable affecting WCR heat exchangercost-effectiveness. Fundamentally, if themakeup water is already cool, there islittle point in trying to recover chill thatis lost with the purge water. Makeupwater temperature can vary significantlydepending on the region, season, andwater delivery system. Well watertemperatures vary little seasonally, butvary from about 45-75 F regionally.Surface water temperatures vary season-ally and regionally, with the combined

effect resulting in a range from nearfreezing to around 100F.Makeup water temperature is also

affected by the length and location ofwater supply piping. Longer supply lineslocated above ground are more likely toyield temperatures close to currentambient conditions. Most supply linesare buried, however, but not too deeply.Near surface ground temperatures tend totrack seasonal variations in average dailyair temperatures, so even makeup wateroriginating from wells is likely toexperience some seasonal variation in

temperature, unless the well is practicallyadjacent to the building with the icemaker.

If makeup water temperature dataare not available, the local water supplycompany should be able to provideaverage monthly temperature data as itleaves their plant. A comparison withtheir current temperature and the currenttemperature at your facility (measuredeasily with any hand-held thermometer)provides some guidance for estimatingaverage monthly temperatures at yourfacility throughout the year. Note that the

warming or cooling of water in transitbetween the water plant and your facilitywill vary depending on the time of yearas well as supply piping length andlocation.

energy ratesThe average monthly electricity rate

based on energy charges may be simplydefined by the rate structure if flat energyrates apply or may require a quick

calculation if time-of-use rates apply. Inthe latter case, monthly electricity billscan be examined to identify total energy-related charges and kWh consumption.The ratio of these two figures can beused as the average monthly electricityrate based on energy charges. Monthlydemand charges must be added to theenergy charges and the sum divided bykWh consumption to calculate the

average monthly electricity rate basedon energy and demand charges.

The fossil fuel or steam rate, typicallya flat charge per unit of consumption,must be converted to a $/MMBtu basisif sold on another basis (e.g., $/therm,$/gallon, $/ton, $/1,000 lb). If demandcharges apply to the fossil fuel, theaverage monthly rate can be calculatedas described for the electricity rate basedon energy and demand charges.

cooling system COP

The cooling system COP will varywith the type of cooling system andambient air conditions. Systems withair-cooled condensers are affected bythe dry-bulb temperature while systemswith water-cooled condensers andevaporative cooling towers are affectedby the wet-bulb temperature as well.Average monthly COPs can be estimatedby comparing performance specificationsat rated conditions with average monthlyair temperatures. System performancedata should be documented in the usersmanual or may be obtained by contacting

the vendor.The National Weather Service should

be able to provide average monthly airtemperatures for a nearby city, althoughadequate accuracy is probably obtainedby applying ones judgment and knowl-edge of the local climate. Lacking betterinformation, a value of 2.5 is recom-mended for vapor compression coolingsystems and values of 0.65 and 1.2 arerecommended for single-effect anddouble-effect lithium bromide absorptioncooling systems, respectively.

heating system efficiencyor COP

Heating system efficiency will varywith the type of heating system, and mayvary with ambient air conditions. Again,the system users manual or vendorshould be consulted to establish itsefficiency. An efficiency of 0.80 isrecommended for fossil-fueled systemsif better information is not available.On the same basis, a COP of 2.5 is


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recommended forelectrically-drivenheat pumps.

Facility data assump-tions for the two casestudies are presented inTable 2. Note thatelectricity energy anddemand rate data andcooling system COP data

are only required whenthe building is operatingin the cooling mode,while heating fuel rateand heating systemefficiency data are onlyrequired when thebuilding is operating inthe heating mode.

Ice Maker and WCRHeat Exchanger Data

The following ice maker and WCR

heat exchanger data are required todetermine WCR heat exchanger cost-effectiveness:

ice production

water charged to reservoir per unit ofice production

makeup water temperature reduction

ice maker COP.

In addition to makeup water tempera-

ture, ice production and makeup watertemperature reduction are the keys toWCR heat exchanger cost-effectiveness.Each of these three factors can varysignificantly, depending on the regionallocation, application, type of ice maker,and type of WCR heat exchanger.

ice productionMonthly ice production, as a percent

of rated capacity (hereinafter referredto as the capacity factor), tends to berelatively high for ice makers because

their built-in storage capacity levels outshort-term peak demands for ice. Never-theless, ice maker capacity factor variessignificantly between different serviceapplications (e.g., hotel hallway applica-tions vs. restaurant applications) andvaries seasonally for a given applicationas well. Estimating ice productionaccurately may be a difficult task. Themost accurate approach would be torecord the number of ice-harvestingcycles and multiply this by the amount of

ice produced per cycle. The latter figureshould be documented in the ice makers

users manual. Alternatively, ice con-sumption can be estimated using rules-of-thumb presented in ASHRAE (1996) forseveral different ice maker applications.

water charged to reservoir per unitice production

The water charged to the reservoirper unit of ice production should not beconfused with total water consumptionper unit of ice production. The latterfigure is usually documented in the icemakers users manual and is alsoreported in the Air Conditioning andRefrigeration Institutes (ARIs)Direc-tory of Certified Automatic CommercialIce-Cube Machines and Storage Bins

(ARI 1997) for equipment they havetested. The former figure will be lessthan the latter figure for ice makers withan overflow or combination purge/overflow charge and discharge mecha-nism. Reservoir volume can be easilydetermined by pouring a measuredamount of water into the reservoir untilfull. Dividing by the amount of iceproduced per harvest (should be docu-

mented in the ice maker users manual)yields the appropriate ratio, whichtypically ranges from 1.2 to 1.8.

makeup water temperaturereduction

A reduction in makeup water tempera-ture is the fundamental thermal objectiveof a WCR heat exchanger, but is verydifficult to estimate. As previouslydiscussed underApplication Screening,

a WCR heat exchanger can be expectedto work best with purge-type ice makers,

worst with overflow-type ice makers,with intermediate results for ice makerswith a combination purge/overflowdesign. More specifically, the reductionin makeup water temperature is expectedto be greatest for purge-type ice makersand least for overflow-type ice makers.For any type of ice maker, the reductionin makeup water temperature possiblewith a WCR heat exchanger increaseswith makeup water temperature. Highermakeup water temperatures increase thedriving force controlling heat transferwithin the WCR heat exchanger and the

effective cooling capacity of the dis-charge water.

The reduction in makeup watertemperature as a function of makeupwater temperature was previously shownin Figure 4 for several ice makersequipped with a Maximicer WCR heatexchanger (similar data were not madeavailable for the Fast Ice WCR heatexchanger). The following observationsare made:

Water temperature reduction generallyincreases as makeup water tempera-

ture increases.

Water temperature reduction isgenerally greater for the Manitowocice makers than the Hoshizaki orCornelius ice makers.

There is considerable variation inwater temperature reduction for agiven makeup water temperature,depending on the type of ice maker.

Table 2. Case Study Facility Data Assumptions

ElectricityMakeup Electricity Energy & BuildingWater Energy Demand Heating Cooling Heating Space

Temperature, Rate, Rate, Fuel, Rate System System ConditioningMonth F $/kWh $/kWh $/MMBtu COP Efficiency Mode

Jan 60 0.06 0.065 4.50 2.9 0.80 heatingFeb 55 0.06 0.065 4.50 2.8 0.80 heating

Mar 50 0.06 0.065 4.50 2.7 0.80 coolingApr 55 0.09 0.100 4.50 2.6 0.80 coolingMay 60 0.09 0.100 4.50 2.5 0.80 coolingJun 65 0.09 0.100 4.50 2.4 0.80 coolingJul 70 0.09 0.100 4.50 2.3 0.80 coolingAug 75 0.09 0.100 4.50 2.4 0.80 coolingSep 80 0.09 0.100 4.50 2.5 0.80 coolingOct 75 0.06 0.065 4.50 2.6 0.80 coolingNov 70 0.06 0.065 4.50 2.7 0.80 coolingDec 65 0.06 0.065 4.50 2.8 0.80 heating


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The variation in water temperaturereduction increases with makeupwater temperature.

No data were collected for overflow-type ice makers.

The Manitowoc and Cornelius icemakers are purge-type machines, whilethe Hoshizaki is a combination purge/

overflow design. As expected, theaverage water temperature reductionreported for the two purge-type machinesis greater than for the purge/overflowmachine, but the limited data forCornelius and Hoshizaki ice makersmakes it risky to draw any firm conclu-sions. Furthermore, its not known whatthe purging frequency or filling periodwere for the two Hoshizaki machines orthe ratio of reservoir water to ice for anyof the machines. In short, Figure 2 canbe used to estimate the ballpark impactof a WCR heat exchanger on the reduc-

tion in makeup water temperature, butthere is considerable uncertainty in thiskey performance factor.

ice maker COPThe ice maker COP translates the

thermal energy savings from reducingthe makeup water temperature into icemaker electrical energy savings and areduction in thermal energy rejected atthe condenser. The appropriate ice makerCOP is defined as the ratio of totalthermal load, including all sources of

heat that must be rejected by the icemaker, to the sum of electric energy inputto the compressor, condenser fan, andwater pump duringthe ice-generationmode, with thermalload and electricityinput measured inthe same units.

Unfortunately,this measure ofperformance is notlikely included inthe ice maker

owners manual orreadily availablefrom the ice makervendor. Ice makerperformance iscommonly quotedin terms of kWh perunit of ice produc-tion at prescribedtest conditions.Unfortunately, this

figure cannot be translated into therequired COP figure without knowingthe split between electricity consumptionduring the ice-making mode (which isaffected by the WCR heat exchanger)and the ice-harvesting mode (which isnot affected by the WCR heat exchanger)and the total thermal load. Fortunately,detailed thermal and electrical loadestimates presented in A.D. Little (1996)

for a typical ice maker show its COPto be about 1.7. While this figure willvary depending on ice maker design andambient air conditions for systems withexternal condensers, the value of 1.7 isrecommended for use in evaluatingcost-effectiveness unless better dataare available.

Ice maker and WCR heat exchangerdata assumptions for the two case studiesare presented in Table 3.

Energy SavingsAnnual energy savings are calculated

by applying the assumptions presentedin Tables 2 and 3 to equations 1-7. Themonth-by-month and annual energysavings are presented in Table 4. Icemaker energy savings occur for allapplications, while HVAC energy savingsoccur if the ice maker condenser is insidethe building. Note that when the buildingis in the heating mode, ice maker energysavings translate into HVAC fuel usageor increased heating energy costs. Thecase study results also show the signifi-cance of the HVAC energy savings in

addition to the ice maker energy savings.

Life-Cycle CostThe purchase cost for a WCR heat

exchanger applicable to a 1,000 lb/dayice maker is about $500, and includes thefittings likely to be required for installa-tion. Hookup to the ice maker shouldtake from 1 to 2 hours of a plumbers orrefrigeration technicians time. Thus, thetotal installed cost is estimated to beabout $550.

Other benefits claimed by WCR heatexchanger manufacturers are 1) increas-ing the hourly production capacity,which may avoid the need for a largeror additional machine or the need topurchase supplemental ice, and 2)lowering the compressor head pressure,which may lengthen machine life and/orreduce machine maintenance. Thesebenefits may occur, but are generallyless tangible, more uncertain, more site-specific, and more difficult to quantifythan the energy savings benefits de-scribed above. Therefore, the dollarvalue of these benefits has not beenincluded in the case studies. However,the increase in ice production capacitymay be more valuable than the energysavings if the need to purchase a largeror additional machine or supplementalice is avoided. The potential for longermachine life and/or less maintenanceseems plausible, but the dollar value ofthese benefits is much more speculative.

WCR heat exchangers are passivedevices (i.e., they have no moving parts).As a result, no components are expected

to wear out or require adjustment.Periodic cleaning may be required,especially in applications with high

Table 3. Case Study Ice Maker and WCR Heat Exchanger Assumptions

Ice ProductionIce Production lb (based on Reservoir Makeup Water

Capacity 1,000 lb/day Water to Ice TemperatureMonth Factor machine) Ratio Reduction, F Ice Maker COP

Jan 0.4000 12,400 1.5 10 1.7Feb 0.4333 12,133 1.5 7 1.7

Mar 0.4667 14,467 1.5 4 1.7Apr 0.5000 15,000 1.5 7 1.7May 0.5333 16,533 1.5 10 1.7Jun 0.5666 17,000 1.5 13 1.7Jul 0.6000 18,600 1.5 16 1.7Aug 0.5667 17,567 1.5 19 1.7Sep 0.5333 16,000 1.5 22 1.7Oct 0.5000 15,500 1.5 19 1.7Nov 0.4667 14,000 1.5 16 1.7Dec 0.4333 13,433 1.5 13 1.7


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concentrations of water impurities, butcleaning has not been an issue for usersto date. Overall, uncertain cleaning costsare offset (more or less) by the uncertainbenefits cited in the preceding paragraph.

The installed cost and energy savingsdata presented above were input into theNIST BLCC model (see Appendix A) tocompare the life-cycle cost differencesbetween an ice maker with and without aWCR heat exchanger. One comparison isbased on the ice makers condenser beinginside the building, while the other is

based on an outside condenser. BLCCoutput documenting the comparison isshown in Tables 5 and 6. CorrespondingECIP form data are presented in Appen-dix B. The results show the WCR heatexchanger to have a payback period of 6years for an ice maker with an indoorcondenser and 11 years for an outdoorcondenser for the conditions assumed inTables 2 and 3. Please be cautionedthat the payback period could be lessthan 1 year or greater than 100 years,depending on the site-specific condi-tions! Site-specific conditions must be

evaluated before cost-effectiveness canbe determined!

The Technology in

PerspectiveCare must be taken in evaluating the

application of WCR heat exchangers tocommercial ice makers. Differences insite conditions and ice maker design, plusdifferences in WCR heat exchangers

offered by different vendors, have asignificant impact on cost-effectiveness.Therefore, the accumulation of additionalexperience and independent testing byelectric utilities and other organizationsshould make it easier to identify cost-effective applications in the future. Still,the potential benefits in certain applica-tions are great enough that WCR heatexchangers should be considered in theFederal sector now.

The Technologys DevelopmentWCR from ice makers is not a novel

concept. WCR equipment is commonlyimplemented in industrial ice-makingsystems, often in concert with waterpurification systems. WCR heat ex-changers have periodically been appliedto commercial ice makers in the past,according to several industry representa-tives, with mixed results. Problems withscaling were reported and/or the benefitswere not adequate to justify the initialcost. No scaling problems have beenreported as yet by users of either the FastIce or Maximicer WCR heat exchangers,

but water purity and ice maker designand operating settings affecting waterpurging (key factors affecting thepropensity for scaling) have rarely beenrecorded, so it is difficult to predict safeor unsafe application conditions.Maximicer has incorporated plastic partsto insulate the WCR heat exchanger fromany stray electric currents that enhanceprecipitate formation. However, noconsensus has been reached on thepreferred WCR heat exchanger design,

as indicated by the differences in theFast Ice and Maximicer units.

Technology OutlookWCR heat exchangers for commer-

cial-sized automatic ice makers arecurrently cost-effective in selectedapplications. Several factors affect cost-effectiveness. In general, cost-effective-ness is enhanced when 1) the annualdemand for ice is relatively high, 2) theice maker is operated in a purge mode(as described inApplication Screening),3) the average annual makeup watertemperature is relatively high, 4) the icemakers condenser is located indoors, and5) the electricity rate is relatively high.

Thermal efficiency seems adequate incurrent WCR heat exchangers. Assumingthat scaling remains a non-problem, thekey factor that could be improved is firstcost. Hopefully, mass productioneconomies-of-scale and/or competitionfrom multiple vendors will result in lowerequipment costs in the future. Customerinterest may also spark interest on thepart of ice maker manufacturers to offer

WCR heat exchangers as part of theoriginal equipment. Several ice makermanufacturers indicated that energyefficiency generally ranks somewherebetween fifth and tenth on the list of icemaker attributes that are important totheir customers. Therefore, they have nobeen particularly interested in offeringWCR heat exchangers or other energy-efficiency measures.

Table 4. Case Study Annual Energy Savings

Net Energy Net Energy

Ice Maker HVAC Total HVAC Savings with Savings with

Electricity Electricity Electricity Fuel Ice Maker HVAC Total HVAC Outside Inside

Savings, Savings, Savings, Usage, Electricity Electricity Electricity Fuel Condenser, Condenser,

Month kWh kWh kWh MMBtu Savings, $ Savings, $ Savings, $ Usage, $ $ $

Jan 32.06 0.00 32.06 0.37 $1.92 $0.00 $1.92 $1.66 $1.92 $0.26

Feb 21.96 0.00 21.96 0.25 $1.32 $0.00 $1.32 $1.14 $1.32 $0.18

Mar 14.96 14.96 29.92 0.00 $0.90 $0.97 $1.87 $0.00 $0.90 $1.87Apr 27.15 28.19 55.33 0.00 $2.44 $2.82 $5.26 $0.00 $2.44 $5.26

May 42.74 46.16 88.91 0.00 $3.85 $4.62 $8.46 $0.00 $3.85 $8.46

Jun 57.13 64.28 121.41 0.00 $5.14 $6.43 $11.57 $0.00 $5.14 $11.57

Jul 76.94 90.32 167.26 0.00 $6.92 $9.03 $15.96 $0.00 $6.92 $15.96

Aug 86.29 97.07 183.36 0.00 $7.77 $9.71 $17.47 $0.00 $7.77 $17.47

Sep 91.00 98.28 189.28 0.00 $8.19 $9.83 $18.02 $0.00 $8.19 $18.02

Oct 76.14 79.06 155.20 0.00 $4.57 $5.14 $9.71 $0.00 $4.57 $9.71

Nov 57.91 57.91 115.82 0.00 $3.47 $3.76 $7.24 $0.00 $3.47 $7.24

Dec 45.15 0.00 45.15 0.52 $2.71 $0.00 $2.71 $2.34 $2.71 $0.37

Totals 629.42 576.24 1,205.66 1.14 $49.20 $52.31 $101.51 $5.14 $49.20 $96.37


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Table 5. NIST BLCC Results for Ice Maker with Outside Condenser

************************************************************************************************************ N I S T B L C C: COMPARATIVE ECONOMIC ANALYSIS (ver. 4.3-96 ) *

***********************************************************************************************************PROJECT: Waste Chill Recovery Heat ExchangerBASE CASE: Base1ALTERNATIVE: Outside Condenser

PRINCIPAL STUDY PARAMETERS:

-ANALYSIS TYPE: Federal AnalysisEnergy Conservation ProjectsSTUDY PERIOD: 7.00 YEARS (JAN 1997 THROUGH DEC 2003)DISCOUNT RATE: 3.8% Real (exclusive of general inflation)BASE CASE LCC FILE: BASE1.LCCALTERNATIVE LCC FILE: WCR1.LCC

COMPARISON OF PRESENT-VALUE COSTS

BASE CASE: ALTERNATIVE: SAVINGSBase1 outside cond FROM ALT.

INITIAL INVESTMENT ITEM(S): CASH REQUIREMENTS AS OF SERVICE DATE $0 $550 -$550

SUBTOTAL $0 $550 -$550

FUTURE COST ITEMS:ENERGY-RELATED COSTS $292 $0 $292

SUBTOTAL $292 $0 $292

TOTAL P.V. LIFE-CYCLE COST $292 $550 -$258

NET SAVINGS FROM ALTERNATIVE Outside Cond COMPARED TO ALTERNATIVE Base1

Net Savings = P.V. of non-investment savings $292- Increased total investment $550

Net Savings: -$258

Note: the SIR and AIRR computations include differential initial costs, capital replacement costs, and resale value (if any)as investment costs, per NIST Handbook 135 (Federal and MILCON analyses only).

SAVINGS-TO-INVESTMENT RATIO (SIR)FOR ALTERNATIVE Outside Cond COMPARED TO ALTERNATIVE Base1

P.V. of non-investment savingsSIR = = 0.53

Increased total investment

ADJUSTED INTERNAL RATE OF RETURN (AIRR)FOR ALTERNATIVE outside cond COMPARED TO ALTERNATIVE Base1

(Reinvestment rate = 3.80%; Study period = 7 years)

AIRR = -5.17%

ESTIMATED YEARS TO PAYBACK

Simple Payback never reached during study periodDiscounted Payback never reached during study period

ENERGY SAVINGS SUMMARY

Energy Units Annual Consumption Life-Cycletype Base Case Alternative Savings Savings

Electricity kWh 629 0 629 4,406


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Table 6. NIST BLCC Results for Ice Maker with Inside Condenser

************************************************************************************************************* N I S T B L C C: COMPARATIVE ECONOMIC ANALYSIS (ver. 4.3-96 ) *

************************************************************************************************************

PROJECT: Waste Chill Recovery Heat ExchangerBASE CASE: Base2ALTERNATIVE: Inside Condenser

PRINCIPAL STUDY PARAMETERS:-ANALYSIS TYPE: Federal AnalysisEnergy Conservation ProjectsSTUDY PERIOD: 7.00 YEARS (JAN 1997 THROUGH DEC 2003)DISCOUNT RATE: 3.8% Real (exclusive of general inflation)BASE CASE LCC FILE: BASE2.LCCALTERNATIVE LCC FILE: WCR2.LCC

COMPARISON OF PRESENT-VALUE COSTS

BASE CASE: ALTERNATIVE: SAVINGSBase2 inside cond FROM ALT.

INITIAL INVESTMENT ITEM(S): CASH REQUIREMENTS AS OF SERVICE DATE $0 $550 -$550

SUBTOTAL $0 $550 -$550FUTURE COST ITEMS:ENERGY-RELATED COSTS $603 $31 $571

SUBTOTAL $603 $31 $571

TOTAL P.V. LIFE-CYCLE COST $603 $581 $21

NET SAVINGS FROM ALTERNATIVE Inside Cond COMPARED TO ALTERNATIVE Base2

Net Savings = P.V. of non-investment savings $571- Increased total investment $550

Net Savings: $21

Note: the SIR and AIRR computations include differential initial costs, capital replacement costs, and resale value (if any)as investment costs, per NIST Handbook 135 (Federal and MILCON analyses only).

SAVINGS-TO-INVESTMENT RATIO (SIR)FOR ALTERNATIVE Inside Cond COMPARED TO ALTERNATIVE Base2

P.V. of non-investment savingsSIR = = 1.04

Increased total investment

ADJUSTED INTERNAL RATE OF RETURN (AIRR)FOR ALTERNATIVE inside cond COMPARED TO ALTERNATIVE Base2

(Reinvestment rate = 3.80%; Study period = 7 years)

AIRR = -4.37%ESTIMATED YEARS TO PAYBACK

Simple Payback occurs in year 6Discounted Payback occurs in year 7

ENERGY SAVINGS SUMMARY

Energy Units Annual Consumption Life-Cycletype Base Case Alternative Savings Savings

Electricity kWh 1,206 0 1,206 8,440

Natural Gas MBtu 0 1 -1 -8


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ManufacturersThe two firms listed below are known

to manufacture a waste chill recovery(WCR) heat exchanger device. Contactthe manufacturers for more informationregarding their products.

Maximicer13740 Research Blvd, Suite K-5Austin, Texas 78750(512) 258-8801(512) 258-8804 Fax1-800-289-9098email: [email protected]:/www.maximicer.com/

Fast Ice ProductsEnvironmental Industries

International, Inc.4731 Highway A1A, Suite #216Vero Beach, Florida 32963(561) 231-9772(561) 231-9773 Fax

1-800-373-3423

Who is Using the

Technology

Federal SitesBastrop Federal Correction Institution

Non-Federal SitesThe WCR technology has been

installed in many hotel, food, andconvenience store locations. Thefollowing is a partial list of some WCR

customers:Hotels and Motels - Crown PlazaHotels, Holiday Inn, Hyatt, La Quinta,Marriott Hotels, Omni Hotels,Radisson, Ramada Inn, andThe Ritz - Carlton.

Restaurants - American RestaurantPartners, Pizza Hut, Long JohnSilvers, Metromedia Steak Houses,Ponderosa Steak House, Mr. Gattis,Inc., Outback Steakhouse, Inc.,PepsiCo, Inc., Taco Bell, RyansFamily Steak Houses, Inc., S&ARestaurants, Inc., Steak and Ale,Bennigans, ShowBiz Pizza Time,Inc., Chuck-E-Cheeses, Sonic Corp,

Subway Sandwich Shops, Inc., TheCounty Line, Inc., and Whataburger,Inc.School Districts/Universities -Bastrop ISD, Texas, Belton ISD,Texas, Del Valley ISD, Texas,Gatesville ISD, Texas, Leander ISD,Texas, Marriott Food Services,Leander, Texas, Round Rock ISD,Texas, San Felipe Del Rio ISD, Texas,and Southwestern University.Hospitals - Sid Peterson MemorialHospital.Convenience Stores - Diamond

Shamrock, Diamond ShamrockCorner Mart, and The Water Jug.

For Further

Information

Trade AssociationsAir-Conditioning & RefrigerationInstitute (ARI)4301 N. Fairfax Dr., Suite 425,Arlington, VA 22203(703) 524-8800

(703) 528-3816 Fax

User and Third Party Field andLab Test ReportsTennessee Valley Authority1101 Market StreetChattanooga, Tennessee 37402-2801attn: Jim Folsom423-751-7657

Southern California Edison6090 N. Irwindale AvenueIrwindale, CA 91702attn: Sheila Hartley1-800-336-2822

Madison Gas and Electric Company133 South Blair StreetMadison, Wisconsin 53703attn: Daniel J. Barker

608-252-5602

PatentsUS Patent #4,881,378 (Fast Ice)US Patent #5,379,603 (Maximicer)US Patent #5,555,734 (Maximicer)

ReferencesARI. 1997. Directory of CertifiedAutomatic Commercial Ice-Cube Ma-

chines and Storage Bins. Air Condition-ing and Refrigeration Institute. Arling-ton, VA

Arthur D. Little, Inc. 1996. EnergySavings Potential for CommercialRefrigeration Equipment. Cambridge,MA.

ASHRAE. 1996. 1996 ASHRAEHandbook: Equipment. AmericanSociety of Heating, Refrigeration, andAir-Conditioning Engineers, Inc.Atlanta, GA.

Colen, H.R. 1990. HVAC SystemsEvaluation. R.S. Means Company, Inc.

Kingston, MA.


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AppendixesAppendix A: Federal Life-Cycle Costing Procedures and the BLCC Software

Appendix B: Life-Cycle Cost Analysis Summary: Energy Conservation Investment Program


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Appendix A

Federal Life-Cycle Costing Procedures and the BLCC Software

Federal agencies are required to evaluate energy-related investments on the basis of minimum life-cycle costs (10 CFR Part436). A life-cycle cost evaluation computes the total long-run costs of a number of potential actions, and selects the action thatminimizes the long-run costs. When considering retrofits, sticking with the existing equipment is one potential action, often calledthe baseline condition. The life-cycle cost (LCC) of a potential investment is the present value of all of the costs associated with the

investment over time.

The first step in calculating the LCC is the identification of the costs. Installed Costincludes cost of materials purchased andthe labor required to install them (for example, the price of an energy-efficient lighting fixture, plus cost of labor to install it). EnergyCostincludes annual expenditures on energy to operate equipment. (For example, a lighting fixture that draws 100 watts and operates2,000 hours annually requires 200,000 watt-hours (200 kWh) annually. At an electricity price of $0.10 per kWh, this fixture has anannual energy cost of $20.) Nonfuel Operations and Maintenance includes annual expenditures on parts and activities required tooperate equipment (for example, replacing burned out light bulbs). Replacement Costs include expenditures to replace equipmentupon failure (for example, replacing an oil furnace when it is no longer usable).

Because LCC includes the cost of money, periodic and aperiodic maintenance (O&M) and equipment replacement costs, energyescalation rates, and salvage value, it is usually expressed as a present value, which is evaluated by

LCC = PV(IC) + PV(EC) + PV(OM) + PV(REP)

where PV(x) denotes present value of cost stream x,IC is the installed cost,EC is the annual energy cost,OM is the annual nonenergy O&M cost, andREP is the future replacement cost.

Net present value (NPV) is the difference between the LCCs of two investment alternatives, e.g., the LCC of an energy-saving orenergy-cost-reducing alternative and the LCC of the existing, or baseline, equipment. If the alternatives LCC is less than thebaselines LCC, the alternative is said to have a positive NPV, i.e., it is cost-effective. NPV is thus given by

NPV = PV(EC0) PV(EC1)) + PV(OM0) PV(OM1)) + PV(REP0) PV(REP1)) PV(IC)or

NPV = PV(ECS) + PV(OMS) + PV(REPS) PV(IC)

where subscript 0 denotes the existing or baseline condition,subscript 1 denotes the energy cost saving measure,IC is the installation cost of the alternative (note that the IC of the baseline is assumed zero),ECS is the annual energy cost savings,OMS is the annual nonenergy O&M savings, andREPS is the future replacement savings.

Levelized energy cost (LEC) is the breakeven energy price (blended) at which a conservation, efficiency, renewable, or fuel-switching measure becomes cost-effective (NPV >= 0). Thus, a projects LEC is given by

PV(LEC*EUS) = PV(OMS) + PV(REPS) PV(IC)

where EUS is the annual energy use savings (energy units/yr). Savings-to-investment ratio (SIR) is the total (PV) savings of ameasure divided by its installation cost:

SIR = (PV(ECS) + PV(OMS) + PV(REPS))/PV(IC).

Some of the tedious effort of life-cycle cost calculations can be avoided by using the Building Life-Cycle Cost software, BLCC,developed by NIST. For copies of BLCC, call the FEMP Help Desk at (800) 363-3732.


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Appendix B

Life-Cycle Cost Analysis Summary:Energy Conservation Investment Program

Energy/Water Life Cycle Cost Analysis SummaryOutside Ice Maker Condenser

Installation: Sample Preparation Date: 06-26-1997Location: Sample Region No. 4 Project No. SampleProject Title: Waste Chill Recovery Heat Exchanger Fiscal Year: 1997Base Date: JAN 1997 BOD: JAN 1997(a) Economic Life: 7 yearsDiscount rate: 3.80% Prepared by: D.R BrownBLCC input data files: Project: MBASE1.DAT Base Case: MWCR1.DAT

1. InvestmentA. Construction Cost $550B. SIOH $0C. Design Cost $0 Funding Amount:D. Total Cost (1A + 1B + 1C) $550 $550E. Salvage Value of Existing Equipment $0F. Public Utility Company Rebate $0 Present Value:(b)

G. Total Investment (1D - 1E - 1F ) $550 $550

2. Energy and Water Savings (+) or Cost (-)Analysis Date Savings, unit costs, & discounted savingsDate of NISTIR 85-3273-X used for discount factors: october 1995

Unit Cost Savings Annual Discount DiscountedFuel $/MBtu MBtu/Yr Savings Factor Savings (1) (2) (3) (4) (5)A. Electric $22.854 2.1 $49 5.950 $292B. Dist oil $0.000 0.0 $0 0.000 $0C. Resid oil $0.000 0.0 $0 0.000 $0D. Nat Gas $0.000 0.0 $0 0.000 $0E. Coal $0.000 0.0 $0 0.000 $0F. Demand Savings $0 0.000 $0

G. Subtotal 2.1 $49 $292

Annual Discount Discounted$/Mgal Mgal/yr Savings Factor Savings

H. Water use $0.00 0.0 $0 0.000 $0Water disp $0.00 0.0 $0 0.000 $0Subtotal $0 $0

I. Total $49 $292

3. Non-Energy Savings (+) or Cost (-)A. Annually Recurring (+/-) $0

(1) Discount Factor (Table A) 0.000(2) Discounted Savings/Cost (3A x 3A1) $0

B. Non-Annually Recurring (+/-)Item Savings (+) Occurrence Factor Discounted

Cost (-) (from BOD) (Table A-1) Savings or Cost(1) (2) (3) (4)

d. Total $0 $0C. Total Non-energy Savings (+)/Cost(-) (3A(2)+3Bd(4)) $0

4. First year savings (2I3 + 3A5 + 3Bd1/Yrs Economic Life) $495. Simple Payback Period (1G/4) 11.21 years6. Total Discounted Savings (2I5 + 3C) $2927. Savings to Investment Ratio (SIR = 6 / 1G) 0.538. Adjusted Internal Rate of Return (AIRR) -5.18%(a) BOD = Beneficial Occupancy Date (Service Date)(b) Present value is less than actual cost when investment costs are incurred after base date.


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Energy/Water Life Cycle Cost Analysis SummaryInside Ice Maker Condenser

Installation: Sample Preparation Date: 06-26-1997Location: Sample Region No. 4 Project No. SampleProject Title: Waste Chill Recovery Heat Exchanger Fiscal Year: 1997Base Date: JAN 1997 BOD: JAN 1997(a) Economic Life: 7 yearsDiscount rate: 3.80% Prepared by: D.R BrownBLCC input data files: Project: MBASE2.DAT Base Case: MWCR2.DAT

1. InvestmentA. Construction Cost $550B. SIOH $0C. Design Cost $0 Funding Amount:D. Total Cost (1A + 1B + 1C) $550 $550E. Salvage Value of Existing Equipment $0F. Public Utility Company Rebate $0 Present Value:(b)

G. Total Investment (1D - 1E - 1F ) $550 $550

2. Energy and Water Savings (+) or Cost (-)Analysis Date Savings, unit costs, & discounted savingsDate of NISTIR 85-3273-X used for discount factors: october 1995

Unit Cost Savings Annual Discount DiscountedFuel $/MBtu MBtu/Yr Savings Factor Savings (1) (2) (3) (4) (5)A. Electric $24.612 4.1 $101 5.950 $603B. Dist oil $0.000 0.0 $0 0.000 $0C. Resid oil $0.000 0.0 $0 0.000 $0D. Nat Gas $4.500 -1.1 -$5 6.071 -$31E. Coal $0.000 0.0 $0 0.000 $0F

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