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Heating Systems. Greenhouse Management. Reasons to Learn. Why are heating systems important in greenhouses? Why are their different types of heating systems? Why are there different fuels for heating? Why are gas prices so high?. Questions to Answer. What are some different heating system?
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Heating Systems Greenhouse Management
Reasons to Learn • Why are heating systems important in greenhouses? • Why are their different types of heating systems? • Why are there different fuels for heating? • Why are gas prices so high?
Questions to Answer • What are some different heating system? • What are some advantages and disadvantages of each? • What are some to think about when considering a heating system? • What are some fuels used to heat?
THE SUN • Greenhouse Effect • Process by which the rays of the sun entering the greenhouse as light are changed to heat energy and trapped inside. • Radiant energy • Energy that comes from the a radiant source such as the sun
Why Not Solar Alone? • Day length in the winter time. • Periods of poor weather • Different glazing have different heat loss • Not constant or always reliable
Fuel Considerations • Cost per BTU • BTU (British Thermal Unit)- heat required to raise temp. of 1lb of water one degree • Fuel Availability • Fuel Transportation Cost • Storage of large supply • Equipment cost
Types of fuel • Electricity • Only feasible on a small scale • Solar • Not enough • Wood • Equipment and expense • Natural Gas • Not available everywhere • Coal • Equipment and availability • Environmental concerns • Disposal • Fuel oil • Availability and storage
Heating a Glass House • Hot water heating system • Used in glass glazed houses smaller that 15,000 square feet • Water is heated in a boiler and pumped through pipes • Effective when there is a number of small compartments to be heated to different temperatures • 2 different types: gravity flow return system & motorized accelerated systems
Glass House cont. • Steam heating system • Used in glass houses greater than 15,000 square feet • Water heated to a boil and steam runs through the pipes • The steam looses heat to the air surrounding and then condenses back to water • Closed circuit system
Plastic Glazed House Heating • Hot air furnaces • Centrally located with air deflectors • Large greenhouses need more than one furnace • Infrared radiant heating system • Gas-fired burners heat air that is distributed through pipes to the plants • Not used often because its not effective in large houses
Plastic House • Forced-air heaters • Localized heater units that force hot air directly into a duct system • Uses combination of electricity and propane or other gas • Must be vented
Other Considerations • Double layer plastic, separated 3 to 6 inches by air, can be used to reduce heat requirement by 30 to 40%. • Twin-wall ridged plastic panels can reduce cost but can be expensive. • Heat rises and needs to be circulated