With an evaporated cooling system, humid air containing the heat that it picked up within the greenhouse is exhausted through the vents or fans to be replaced by cooler, drier outside air. It takes 1 Btu of heat to raise the temperature of 1 pound of water by 1° F, but it takes 1,060 Btu’s of heat to convert the 1 pound to a vapor. It can cool the greenhouse to 10-20° F below the outside temperature. Evaporative cooling may be the best choice under these conditions.Įvaporative cooling is a simple system that uses the heat in the air to evaporate water from leaves and other wetted surfaces. Excessive temperature results in delayed flowering and internode stretching. Still, on summer days, the temperature may exceed the desired level that promotes good plant growth. Ventilation, either natural or fan, will remove a considerable amount of heat that is collected. Shade on the inside, if it contains aluminum foil, will reflect some of the heat back out. Shade on the outside will keep some of the heat out. The remainder of the heat must be removed through ventilation. If the greenhouse is full of plants, about half of this heat is used for transpiration and evaporation. This is equivalent to burning 32 gallons of fuel oil or 320 therms of natural gas. On a bright, sunny summer day, a 30 x 100-foot greenhouse will gather about 32 million Btu’s of heat.
0 Comments
Leave a Reply. |