Greenhouse Heating
(book excerpts)Heating is a major concern to commercial greenhouse operations. This is due primarily to the costs involved in the purchase and operation of heating equipment as well as the potentially disastrous effects of a poorly designed system can have on crop production. Many types of heating systems are available for use in greenhouses. Heating systems are usually classified as central or local. In a central system, the steam boiler is located in a separate house outside the greenhouse, and the heat is distributed to the greenhouses by a distribution system. In a local system, the heat is released directly to the greenhouse space since the furnace, and thus combustion is within the greenhouse space. There are four primary systems for greenhouse heating: (1) steam, (2) hot water, (3) hot air, and (4) infrared. Some systems cost less to buy or use less expensive fuels. Others may have a higher initial cost, but they are more efficient and less expensive to operate. The main parameters for choosing the appropriate heating system are greenhouse heating requirements, available source of energy, and fluctuations in temperature gradient. Greenhouse heater requirements depend upon the amount of heat loss from the structure. The number of British thermal units (Btu) will need to be determined to heat the greenhouse. Suitable energy sources for greenhouse heating systems include natural gas, liquid petroleum (LP) gas, fuel oil, wood, and electricity. The cost and availability of these sources will vary somewhat from one area to another. Fluctuations in day and night temperatures should be considered, too, given that some heating systems are more responsive to changes in temperature than others.
Click on the following topics for more information on greenhouse heating.
Topics Within This Chapter:
- Mechanisms of Greenhouse Heat Loss and Gain
- Conduction
- Convection
- Radiation
- Infiltration
- Greenhouse Heating Requirements
- Calculating Greenhouse Heat Load
- Calculating Surface Area of Greenhouse
- Calculating Temperature Difference (Δ)
- Ascertain Heat Loss Coeffcient for Glazing Material
- Calculating Total Greenhouse Heat Loss
- Calculating Greenhouse Infiltration Rate
- Greenhouse Unit Heaters
- Types of Unit Heaters
- Vented versus Unvented Unit Heaters
- Vented Unit Heaters
- Unvented Unit Heaters
- Unit Heater Performance
- Fresh-Air Vents
- Heat Exchanger Material
- Heated Air Distribution
- Greenhouse Central Heating Systems
- Advantages and Disadvantages of Heating Plant Boilers
- Boiler Components
- Types of Heating Plant Boilers
- Firetube Boilers
- Watertube Boilers
- Condensing Boilers
- Heat Distribution from a Boiler System
- Perimeter Heating Systems
- Bench Heating Systems
- Floor Heating Systems
- Overhead Heating Systems
- Hot Water (Hydronic) Unit Heaters
- Greenhouse Infrared Heating Systems
- Benefits of Infrared Heating
- Types of Infrared Heaters
- Air Distribution in Greenhouses
- Horizontal Air Flow Fans
- Placement of Horizontal Air Flow Fans
- Shrouded versus Unshrouded Fans
- Horizontal Air Flow Fans Capacity
- Poly Convection Tubbing
- Heating with Polytubes
- Calculating Size and Number of Holes for Polytubes
- Tube Suspension
- Types of Fuels for Greenhouses
- Gaseous Fuels
- Natural Gas
- Propane
- Fuel Oils
- Biomass Fuels
- Wood Pellets
- Wood Chips
- Comparing the Cost of Heating Fuels
- Renewable Energy for Greenhouses
- Heat Pumps
- Solar Energy for Greenhouses
- Active Solar Systems
- Passive Solar Systems
- Biomass Energy for Greenhouses
- Biomass Boilers and Furnaces
- Biomass System Design
- Components of Biomass Systems
- Geothermal Energy for Greenhouses
- Geothermal Systems
- Types of Geothermal Resources
