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Alternative Heating Opportunities For Heating Greenhouses


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Presented at the 2009 ProGreen EXPO in Denver, CO on 16 January 2009.

Published in: Education

Alternative Heating Opportunities For Heating Greenhouses

  1. 1. <ul><li>Steven E. Newman, Ph.D., A.A.F. </li></ul><ul><ul><li>Greenhouse Crops Extension Specialist and Professor of Floriculture </li></ul></ul><ul><li>John A. Ray, M.S. </li></ul><ul><li>Research Associate </li></ul>Alternative Heating Opportunities for Greenhouses ProGreen EXPO – 2009
  2. 2. Energy Dollars Heat = 70-85%
  3. 3. Greenhouse Fuel <ul><li>Energy is sold in terms of units of fuel </li></ul><ul><li>Most greenhouses use natural gas </li></ul><ul><li>Natural gas is sold in units called therms </li></ul><ul><ul><li>1 therm = 100,000 Btu </li></ul></ul><ul><ul><li>1 dekatherm = 1,000,000 Btu </li></ul></ul><ul><li>Transported gas </li></ul><ul><ul><li>Gas transportation service enables natural gas customers the choice to purchase their gas from third party suppliers </li></ul></ul>
  4. 4. Natural Gas Rates <ul><li>Therm Conversion Factors </li></ul><ul><li>Natural gas is sold in units called therms. </li></ul><ul><li>A therm of natural gas is also dependent on the elevation of the site delivered. </li></ul><ul><li>The metered volumes of gas are converted to therms based on a conversion factor. </li></ul>
  5. 5. Natural Gas Prices Continue to Rise
  6. 6. Other 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
  7. 7. Other 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
  8. 8. Other Fuel Sources Wood -- (option for greenhouses, why?) Green chips 4,500 Btu/lb Dried pellets 8,500 Btu/lb Log burner boiler <ul><li>Wood burners are economical if the wood fuel is readily available and if a degree of automation can be maintained. </li></ul><ul><li>Emissions may be an issue. </li></ul>
  9. 9. Other 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
  10. 10. Alternative Fuels <ul><li>Alternative fuels, also known as non-conventional fuels, are any materials or substances that can be used as a fuel, other than conventional fuels. </li></ul><ul><li>Conventional fuels include: fossil fuels (petroleum (oil), coal, propane, and natural gas), and nuclear materials such as uranium. </li></ul><ul><li> </li></ul>
  11. 11. Alternative Fuels <ul><li>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. </li></ul><ul><li> </li></ul>
  12. 12. Alternative Fossil Fuels <ul><li>Coal reserves </li></ul><ul><ul><li>The Fischer-Tropsch process converts carbon dioxide, carbon monoxide into heavier hydrocarbons, including synthetic oil. </li></ul></ul><ul><li>Methane </li></ul><ul><ul><li>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. </li></ul></ul>
  13. 13. BioFuels <ul><li>Vegetable oil </li></ul><ul><li>Biodiesel </li></ul><ul><li>Bioalcohols </li></ul><ul><li>Bioethers </li></ul><ul><li>Biogas </li></ul><ul><li>Syngas </li></ul><ul><li>Solid biofuels </li></ul>
  14. 14. BioFuels <ul><li>Vegetable oil </li></ul><ul><li>Biodiesel </li></ul><ul><li>Bioalcohols </li></ul><ul><li>Bioethers </li></ul><ul><li>Biogas </li></ul><ul><li>Syngas </li></ul><ul><li>Solid biofuels </li></ul>
  15. 15. BioFuels <ul><li>Vegetable oil </li></ul><ul><ul><li>Edible vegetable oil is generally not used as fuel, but lower quality oil can be used for this purpose. </li></ul></ul><ul><ul><li>Used vegetable oil is increasingly being processed into biodiesel, or (more rarely) cleaned of water and particulates and used as a fuel. </li></ul></ul>
  16. 16. BioFuels <ul><li>Vegetable oil </li></ul><ul><li>Biodiesel </li></ul><ul><ul><li>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). </li></ul></ul><ul><ul><li>Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. </li></ul></ul><ul><ul><li>Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, mustard, flax, sunflower, palm oil, hemp, field pennycress, and algae. </li></ul></ul>
  17. 17. BioFuels <ul><li>Vegetable oil </li></ul><ul><li>Biodiesel </li></ul><ul><li>Bioalcohols </li></ul><ul><ul><li>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). </li></ul></ul>
  18. 18. BioFuels <ul><li>Vegetable oil </li></ul><ul><li>Biodiesel </li></ul><ul><li>Bioalcohols </li></ul><ul><li>Biogas </li></ul><ul><ul><li>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. </li></ul></ul><ul><ul><li>Biogas contains methane and can be recovered from industrial anaerobic digesters and mechanical biological treatment systems. </li></ul></ul><ul><ul><li>Landfill gas is a less clean form of biogas which is produced in landfills through naturally occurring anaerobic digestion. </li></ul></ul>
  19. 19. BioFuels <ul><li>Vegetable oil </li></ul><ul><li>Biodiesel </li></ul><ul><li>Bioalcohols </li></ul><ul><li>Bioethers </li></ul><ul><li>Biogas </li></ul><ul><li>Syngas </li></ul><ul><ul><li>Syngas is produced by the combined processes of pyrolysis, combustion, and gasification. </li></ul></ul><ul><ul><li>Biofuel is converted into carbon monoxide and energy by pyrolysis. </li></ul></ul><ul><ul><li>A limited supply of oxygen is introduced to support combustion. Gasification converts further organic material to hydrogen and additional carbon monoxide. </li></ul></ul>
  20. 20. BioFuels <ul><li>Vegetable oil </li></ul><ul><li>Biodiesel </li></ul><ul><li>Bioalcohols </li></ul><ul><li>Bioethers </li></ul><ul><li>Biogas </li></ul><ul><li>Syngas </li></ul><ul><li>Solid BioFuels </li></ul>
  21. 21. Solid BioFuels <ul><li>Wood, sawdust, grass cuttings, domestic refuse, charcoal, agricultural waste, non-food energy crops, and dried manure. </li></ul><ul><li>Second generation BioFuels – non-edible crops </li></ul><ul><li>Third generation BioFuels – oil from algae </li></ul><ul><li>Fourth generation BioFuels – conversion of vegoil and biodiesel to gasoline </li></ul>
  22. 22. Issues with BioFuels <ul><li>Oil price moderation </li></ul><ul><li>Rising food price </li></ul><ul><ul><li>&quot;food vs. fuel&quot; debate </li></ul></ul><ul><li>Carbon emissions </li></ul><ul><li>Sustainable biofuel production </li></ul><ul><li>Soil erosion, deforestation, and biodiversity </li></ul><ul><li>Impact on water resources </li></ul><ul><li>Impact on society and water for Palm Oil </li></ul><ul><li>Biofuel prices </li></ul><ul><li>Energy efficiency and energy balance of biofuels </li></ul><ul><li>Biofuels and solar energy efficiency </li></ul><ul><li>Centralized vs. decentralized production </li></ul>
  23. 23. Wood Waste <ul><li>Mountain Pine Bark Beetle killed trees </li></ul><ul><ul><li>Access </li></ul></ul><ul><ul><li>Transport </li></ul></ul><ul><ul><ul><li>Less than 50 miles </li></ul></ul></ul><ul><ul><li>Heating plant conversion </li></ul></ul>
  24. 24. Conversion to Alternative Fuels <ul><li>Availability </li></ul><ul><li>Cost </li></ul><ul><li>Modification to heating plant </li></ul><ul><li>Sustainability </li></ul><ul><li>Emissions </li></ul><ul><li>Permits </li></ul>
  25. 25. Solar Energy Solar Panels Hot air from gable Under bench heat
  26. 26. Storage of low grade heat from solar gain in under-bench TES (Thermal Energy Storage) system
  27. 27. Greenhouse earth solar thermal storage EAHE – Earth to Air Heat Exchanger SHCS – Soil Heating and Cooling System Air intake plenum Air return plenum PARAMETERS Air  T i-o Pipe Depth Pipe Material Pipe Diameter Air Flow rate Soil T Soil H 2 O & texture
  28. 28. Greenhouse earth solar thermal storage SHCS – Soil Heating and Cooling System “ Slinky” type Heat Exchange Coil trenched 5 ft deep UNDER greenhouse structure Essentially an electric heater which captures solar gain and adds “heat of compression” Higher COP (SEER rating) = less $ for electric heating Can be combined with other recovery systems; Boiler economizers, A/C condenser heat Fan/coil heat exchanger High Efficiency “variable scroll” compressor Ground Source Heat Pump
  29. 29. HOT WATER TANK High pressure refrigerant vapor condenses Circulation pump for slab Heating at night. Float valve blocks vapor from returning to low-pressure liquid supply tank Lift pump
  30. 30. The Hobbit House
  31. 31. Heat Storage Scott Skogerboe Greenhouse
  32. 32. Heat Storage Scott Skogerboe Greenhouse `
  33. 33. Heat Storage <ul><li>Phase Change Materials </li></ul><ul><ul><li>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. </li></ul></ul><ul><ul><li>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. </li></ul></ul>
  34. 34. Phase Change Salts
  35. 35. Phase Change Salts
  36. 36. Insulation <ul><li>Opaque insulation </li></ul><ul><ul><li>Rigid board insulation </li></ul></ul><ul><ul><ul><li>North walls </li></ul></ul></ul><ul><ul><ul><li>Side walls up to bench height </li></ul></ul></ul><ul><ul><li>Fiberglass </li></ul></ul><ul><ul><ul><li>Protect from water </li></ul></ul></ul><ul><ul><li>Sprayed-on urethane </li></ul></ul>
  37. 37. Insulation <ul><li>Transparent insulation </li></ul><ul><ul><li>Aircap pads </li></ul></ul><ul><ul><ul><li>Difficult to attach to glass </li></ul></ul></ul><ul><ul><ul><li>May be stapled </li></ul></ul></ul><ul><ul><ul><li>12% reduction in light </li></ul></ul></ul><ul><ul><ul><li>On outside, watch snow </li></ul></ul></ul>
  38. 38. Insulation <ul><li>Lap seal </li></ul><ul><ul><li>Transparent caulking compound </li></ul></ul><ul><ul><li>Commercially applied to glass </li></ul></ul><ul><ul><li>More economical when done during construction </li></ul></ul><ul><ul><li>Less air exchange </li></ul></ul>
  39. 39. Insulation <ul><li>Tight covering reduces heat loss </li></ul><ul><ul><li>Weather stripping on doors and vents </li></ul></ul><ul><ul><li>Good glass maintenance </li></ul></ul><ul><ul><li>Closing gaps under foundation </li></ul></ul><ul><ul><li>Lubricating vent louvers for good operation </li></ul></ul><ul><ul><li>Covering unused fans </li></ul></ul>
  40. 40. Polyethylene Film <ul><li>Double poly over glass </li></ul><ul><ul><li>Energy savings up to 50% </li></ul></ul><ul><ul><li>Reduces light transmission </li></ul></ul><ul><ul><li>Less air exchange </li></ul></ul><ul><li>Single poly over glass </li></ul><ul><ul><li>Energy savings up to 40% </li></ul></ul><ul><ul><li>Difficult to inflate </li></ul></ul>
  41. 41. Polyethylene Film
  42. 42. Single Polyethylene over Glass
  43. 43. Inflated Polyethylene Tubes
  44. 44. Movable Nighttime Insulation <ul><li>System Overview </li></ul><ul><ul><li>Construct a frame / grid to move fabric on from truss to truss. </li></ul></ul><ul><li>Support System - Supports The Drive System </li></ul><ul><ul><li>Gear Motor </li></ul></ul><ul><ul><li>Rack & Pinion Chassis </li></ul></ul><ul><ul><li>1-3/8” Steel Drive Shaft </li></ul></ul>
  46. 46. Automated Heat Curtain
  47. 47. Heat Curtains
  48. 48. Heat Transmission
  49. 49. Preliminary 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.
  50. 50. Preliminary Results Heating began with less than 25 HDH when curtains open
  51. 51. Preliminary Results Heating began with less than 285 HDH when curtains closed
  52. 52. Preliminary 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
  53. 53. Preliminary Results <ul><li>At 436 heating degree hours </li></ul><ul><ul><li>House with curtains open required 2.69 hours of heater time </li></ul></ul><ul><ul><li>House with curtains closed required 0.295 hours of heater time </li></ul></ul><ul><ul><li>Savings of 2.39 hours </li></ul></ul><ul><li>Assuming a unit heater at 250,000 Btu/hr </li></ul><ul><ul><li>Open curtains would required 672,500 Btus of fuel </li></ul></ul><ul><ul><li>Closed curtains would require 73,750 Btus of fuel </li></ul></ul>