The fan and pad system has been the standard system for evaporative cooling for more than 50 years. In this system, aspen or cellulose pads are mounted in one endwall or sidewall of the greenhouse. They are supplied with water from a pipe above the pads and excess water is collected in a gutter at the bottom.
Evaporative cooling, which uses the heat in the air to evaporate water from plants and other wetted surfaces can be used to cool the greenhouse as much as 10 to 12oC below the outside temperature. Although evaporative cooling is most effective in dryer climates, such as suitable for North, Central and west part of India.