Chapter 5

Greenhouse Energy Conservation Strategies

Greenhouse Environmental Controls

Thermostats

Inaccurate and imprecise controls will waste heat by failing to maintain temperatures at the appropriate level for a crop. Mechanical thermostats are notoriously inaccurate and imprecise and should be replaced, at the very least, with electronic controls. Thermostats should be aspirated with greenhouse air and be placed near the plant canopy in locations representative of the rest of the greenhouse (not near sidewalls, fans, or doors).

Central Controllers

There are many environmental parameters that need to be controlled in a greenhouse—most significantly air temperature, humidity, carbon dioxide (CO2) levels, lighting, and irrigation. Air temperature and humidity can be controlled with heaters, fans, and louvers. Carbon dioxide can be added using bottled carbon dioxide or a carbon dioxide generator, or by increasing the amount of outside air entering the greenhouse. Lighting can be supplemented with lights or decreased using a shade curtain. In an effort to control energy costs, there are some environmental control interactions to avoid, such as running exhaust fans when the heater is on, cycling heaters and fans on and off, and operating fans while adding carbon dioxide.

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