In the case where biosecurity or insect exclusion is a priority, a closed greenhouse with a fan and pad system may be necessary. When a fan and pad system cannot be justified, in some situations passive ventilation with open sided greenhouses may provide adequate cooling for a given crop without using any energy. Depending on your situation, the cooling capacity of a fan and pad system may or may not be significant enough to justify that level of investment.įan and pad systems need to be sized appropriately to achieve the maximum cooling efficiency. greenhouse, cooling pad equipment cost can be anywhere from $1800-$2000. Cooling pads are not going to be able to achieve 100 percent efficiency. Even in a well-designed greenhouse, air can easily pick up over 8 to 9 ☏ as it passes through the greenhouse. The reduction in air temperature only occurs around the exhaust side of the cooling pad. Represents the cooling potential that can be reached through evaporative cooling.Ĭalculated from historic weather data from weather station located at the Mobile Regional Airport WBD (☏) = Dry Bulb Temperature - Wet Bulb Temperature. The data suggests that during 64 percent of the hours, intake air temperature could be reduced by over 5 ☏ during July 2014. WBD was calculated for what was considered the warmest time of day (11 a.m. summarizes WBD in Mobile, one of the most humid areas of the state. Because of the high humidity in Alabama, the ability to cool with evaporative cooling is somewhat limited, but may be significant depending on the situation. WBD represents how much the air can be cooled through evaporative cooling.Īs humidity increases, the gap between wet and dry bulb temperature decreases resulting in less efficient cooling. This difference is the Wet Bulb Depression (WBD). The ability to cool with evaporative cooling can be estimated by taking the difference between wet and dry bulb temperatures. In Alabama we have exceptionally high humidity, especially along the Gulf Coast. Wet Bulb DepressionĮvaporative cooling becomes more efficient as the relative humidity drops.
Cellulosic pad materials are the preferred choice by most growers as they last longer than aspen pads. Common pad materials include cellulosic materials or aspen fiber pads. This large surface area allows for quick evaporation.
This technique utilizes the cooling effect produced when water evaporates and cools the air as it is pulled through the pad.Ĭooling pads cool by creating large amounts of surface area that are exposed to air being drawn into the greenhouse by exhaust fans.
A “fan and pad” system uses exhaust fans to pull air through evaporative cooling pads. Evaporative CoolingĮvaporative cooling is a tool that can be used to reduce greenhouse temperatures. During the summer months, extra cooling beyond what fan ventilation can provide may be necessary. The greenhouse environment can quickly become too hot for healthy plant production, even in the winter.