Steven E. Newman, Ph.D., A.A.F.Greenhouse Crops Extension Specialist and Professor of Floriculture

John A. Ray, M.S.Research Associate

Alternative Heating Alternative Heating Opportunities for GreenhousesOpportunities for Greenhouses

ProGreen EXPO – 2009

Energy DollarsEnergy Dollars

Heat = 70-85%

Greenhouse FuelGreenhouse Fuel

Energy is sold in terms of units of fuel Most greenhouses use natural gas Natural gas is sold in units called therms

– 1 therm = 100,000 Btu – 1 dekatherm = 1,000,000 Btu

Transported gas – Gas transportation service enables natural gas

customers the choice to purchase their gas from third party suppliers

Natural Gas RatesNatural Gas Rates

Therm Conversion Factors Natural gas is sold in units called therms. A therm of natural gas is also dependent on the

elevation of the site delivered. The metered volumes of gas are converted to

therms based on a conversion factor.

Natural Gas PricesNatural Gas PricesContinue to RiseContinue to Rise

Other Fuel SourcesOther Fuel Sources

Fuel Oil (used by interruptible customers)

No. 1 Slightly heavier than kerosene

No. 2 Small greenhouse heaters

No. 4 Common for boilers

No. 5 Boilers (cheap if available)

No. 6 Requires pre-heating

Other Fuel SourcesOther Fuel Sources

Coal -- (out of favor for greenhouses, why?)

Anthracite Hard coal – greatest heat

Semi-anthracite

Bituminous Soft coal

Sub-Bituminous Western coal

Lignite Low grade coal

Other Fuel SourcesOther Fuel Sources

Wood -- (option for greenhouses, why?)

Green chips 4,500 Btu/lb

Dried pellets 8,500 Btu/lb

Log burner boiler

1. Wood burners are economical if the wood fuel is readily available and if a degree of automation can be maintained.

2. Emissions may be an issue.

Other Fuel SourcesOther Fuel Sources

Gas (Most common in greenhouses)

Natural Storage tanks not required

Burns clean

Easier to maintain boiler

Propane

Butane

Same advantages as natural gas

However, must be stored on site

More expensive

Alternative FuelsAlternative Fuels

Alternative fuels, also known as non-conventional fuels, are any materials or substances that can be used as a fuel, other than conventional fuels.

Conventional fuels include: fossil fuels (petroleum (oil), coal, propane, and natural gas), and nuclear materials such as uranium.

http://en.wikipedia.org/wiki/Alternative_fuel

Alternative FuelsAlternative Fuels

Some well known alternative fuels include biodiesel, bioalcohol (methanol, ethanol, butanol), chemically stored electricity (batteries and fuel cells), hydrogen, non-fossil methane, non-fossil natural gas, vegetable oil and other biomass sources.

http://en.wikipedia.org/wiki/Alternative_fuel

Alternative Fossil FuelsAlternative Fossil Fuels

Coal reserves– The Fischer-Tropsch process converts carbon

dioxide, carbon monoxide into heavier hydrocarbons, including synthetic oil.

Methane– An alternative method of obtaining methane is via

biogas generated by the fermentation of organic matter including manure, wastewater sludge, municipal solid waste (including landfills), or any other biodegradable feedstock, under anaerobic conditions.

BioFuelsBioFuels

Vegetable oil Biodiesel Bioalcohols Bioethers Biogas Syngas Solid biofuels

BioFuelsBioFuels

Vegetable oil Biodiesel Bioalcohols Bioethers Biogas Syngas Solid biofuels

BioFuelsBioFuels

Vegetable oil – Edible vegetable oil is generally not used as

fuel, but lower quality oil can be used for this purpose.

– Used vegetable oil is increasingly being processed into biodiesel, or (more rarely) cleaned of water and particulates and used as a fuel.

BioFuelsBioFuels

Vegetable oil Biodiesel

– Biodiesel is produced from oils or fats using transesterification and is a liquid similar in composition to fossil/mineral diesel. Its chemical name is fatty acid methyl (or ethyl) ester (FAME).

– Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol.

– Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, mustard, flax, sunflower, palm oil, hemp, field pennycress, and algae.

BioFuelsBioFuels

Vegetable oil Biodiesel Bioalcohols

– Biologically produced alcohols, most commonly ethanol, and less commonly propanol and butanol, are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches (easiest), or cellulose (which is more difficult).

BioFuelsBioFuels

Vegetable oil Biodiesel Bioalcohols Biogas

– is produced by the process of anaerobic digestion of organic material by anaerobes. It can be produced either from biodegradable waste materials or by the use of energy crops fed into anaerobic digesters to supplement gas yields.

– Biogas contains methane and can be recovered from industrial anaerobic digesters and mechanical biological treatment systems.

– Landfill gas is a less clean form of biogas which is produced in landfills through naturally occurring anaerobic digestion.

BioFuelsBioFuels

Vegetable oil Biodiesel Bioalcohols Bioethers Biogas Syngas

– Syngas is produced by the combined processes of pyrolysis, combustion, and gasification.

– Biofuel is converted into carbon monoxide and energy by pyrolysis. – A limited supply of oxygen is introduced to support combustion.

Gasification converts further organic material to hydrogen and additional carbon monoxide.

BioFuelsBioFuels

Vegetable oil Biodiesel Bioalcohols Bioethers Biogas SyngasSolid BioFuels

Solid BioFuelsSolid BioFuels

Wood, sawdust, grass cuttings, domestic refuse, charcoal, agricultural waste, non-food energy crops, and dried manure.

Second generation BioFuels – non-edible crops

Third generation BioFuels – oil from algaeFourth generation BioFuels – conversion

of vegoil and biodiesel to gasoline

Issues with BioFuelsIssues with BioFuels

Oil price moderation Rising food price

– "food vs. fuel" debate Carbon emissions Sustainable biofuel

production Soil erosion, deforestation,

and biodiversity

Impact on water resources Impact on society and water

for Palm Oil Biofuel prices Energy efficiency and

energy balance of biofuels Biofuels and solar energy

efficiency Centralized vs.

decentralized production

Wood WasteWood Waste

Mountain Pine Bark Beetle killed trees– Access– Transport

• Less than 50 miles

– Heating plant conversion

Conversion to Alternative FuelsConversion to Alternative Fuels

Availability Cost Modification to

heating plant Sustainability Emissions Permits

Solar EnergySolar Energy

Solar PanelsSolar Panels

Hot air fromHot air fromgablegable

Under benchUnder benchheatheat

Storage of low grade heat from solar gain in Storage of low grade heat from solar gain in under-bench under-bench

TES (Thermal Energy Storage) systemTES (Thermal Energy Storage) system

Air intake plenum

Air return plenum

PARAMETERSAir Ti-o

Pipe DepthPipe Material

Pipe DiameterAir Flow rate

Soil TSoil H2O & texture

Greenhouse earth solar thermal storageGreenhouse earth solar thermal storageEAHE – Earth to Air Heat ExchangerEAHE – Earth to Air Heat Exchanger

SHCS – Soil Heating and Cooling SystemSHCS – Soil Heating and Cooling System

Greenhouse earth solar thermal storageGreenhouse earth solar thermal storageSHCS – Soil Heating and Cooling SystemSHCS – Soil Heating and Cooling System

Fan/coil heat exchanger

High Efficiency “variable scroll” compressorGround Source Heat Pump

“Slinky” type Heat Exchange Coiltrenched 5 ft deepUNDER greenhousestructure

Essentially an electric heater which captures solar gain and adds “heat of compression”Higher COP (SEER rating) = less $ for electric heating

Can be combined withother recovery systems;Boiler economizers, A/C condenser heat

HOTWATERTANK

High pressure refrigerant vapor condenses

Circulation pump for slabHeating at night.

Float valve blocksvapor from returningto low-pressure liquid supply tank

Lift pump

The Hobbit HouseThe Hobbit House

http://www.sunnyjohn.com:///index.html

Heat StorageHeat Storage

Scott Skogerboe Greenhouse

Heat StorageHeat Storage

Scott Skogerboe Greenhouse`

Heat StorageHeat Storage

Phase Change Materials– A phase change material is a substance with a

high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy.

– Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage (LHS) units.

Phase Change SaltsPhase Change Salts

Phase Change SaltsPhase Change Salts

InsulationInsulation

Opaque insulation– Rigid board insulation

• North walls• Side walls up to bench height

– Fiberglass• Protect from water

– Sprayed-on urethane

InsulationInsulation

Transparent insulation– Aircap pads

• Difficult to attach to glass

• May be stapled• 12% reduction in light• On outside, watch snow

InsulationInsulation

Lap seal– Transparent caulking

compound– Commercially applied

to glass– More economical

when done during construction

– Less air exchange

InsulationInsulation

Tight covering reduces heat loss– Weather stripping on doors and vents– Good glass maintenance– Closing gaps under foundation– Lubricating vent louvers for good operation– Covering unused fans

Polyethylene FilmPolyethylene Film

Double poly over glass– Energy savings up to 50%– Reduces light transmission– Less air exchange

Single poly over glass– Energy savings up to 40%– Difficult to inflate

Polyethylene FilmPolyethylene Film

Single Polyethylene over GlassSingle Polyethylene over Glass

Inflated Polyethylene TubesInflated Polyethylene Tubes

Movable Nighttime InsulationMovable Nighttime Insulation

System Overview– Construct a frame / grid to move fabric on

from truss to truss.Support System

-Supports The Drive System

– Gear Motor– Rack & Pinion Chassis– 1-3/8” Steel Drive Shaft

1-3/8” PUSHTUBE

ALUM. ANGLE

7/8” ALUM.LEAD EDGE

GALV. 2” SQ. TUBING

INT. TRUSS MEMBER

ALUM. ANGLE

INTERMEDIATE ROLLER BRACKETS

COVERING MATERIAL

GALV. ANGLEIRON

STATIONARYLINES

Retractable CurtainsRetractable Curtains

Automated Heat CurtainAutomated Heat Curtain

Heat CurtainsHeat Curtains

Heat TransmissionHeat Transmission

0 0.2 0.4 0.6 0.8 1

U value, Btu/hr sq ft °F

No curtain

Porous Cloth

Non-porousmaterial

Aluminizedmaterial

Preliminary ResultsPreliminary Results

Cumulative run time or the amount of time that the heating device was in operation during a heating cycle in hours.

The heating degree days in a season are derived by summing the difference between the average outdoor temperatures above a base (e.g., 65 °F) each 24 hours and the base temperature. Heating degree hours (equal to heating degree days x 24) are used in computing seasonal energy flows in a building due to both conduction and convection.

Preliminary ResultsPreliminary Results

Heating began with less than 25 HDH when curtains open

Preliminary ResultsPreliminary Results

Heating began with less than 285 HDH when curtains closed

Preliminary ResultsPreliminary Results

At 436 HDH and curtains open, 2.69 hours of heater time were required

At 436 HDH and curtains closed, 0.295 hours of heater time were required

Preliminary ResultsPreliminary Results

At 436 heating degree hours– House with curtains open required 2.69 hours of

heater time– House with curtains closed required 0.295 hours

of heater time– Savings of 2.39 hours

Assuming a unit heater at 250,000 Btu/hr– Open curtains would required 672,500 Btus of

fuel– Closed curtains would require 73,750 Btus of fuel