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 Greenhouses Opportunities for Greenhouses ProGreen EXPO – 2009
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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 fuelMost greenhouses use natural gas Natural gas is sold in units called therms
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.
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.
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.
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
AvailabilityCostModification to
heating plantSustainabilityEmissionsPermits
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
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
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