Here is your old friend again, the conservation of energy equation. Q Substitute the terms into the conservation of energy equation. We need to define the system at this point, and for this conservation of energy equation, the system is all of the tomato plants in the greenhouse. Thus, the solar radiation is the amount of energy that actually reaches all of the tomato plants. The reason we chose all of the tomato plants is that Dr. Giacomelli keeps a record of the total number of tomatoes that leave the greenhouse.
Heat transfer processes The primary purpose of greenhouses is control of temperature.
If more heat enters than leaves, then greenhouse air temperature will tend to rise. If more heat leaves than enters, then air temperature will fall. Heat transfer in the context of greenhouse environmental control is usually the net result of heat transfers to and from an object by radiation. This energy transfer can be conceptualized as photons transporting energy from the object to its environment and other photons transporting energy from the environment to the object. Emissivity is a material property that defines its ability to emit energy that it has absorbed.