A SIMPLE GREENHOUSE CLIMATE CONTROL MODEL INCORPORATING EFFECTS OF VENTILATION AND EVAPORATIVE COOLING

A greenhouse climate model, incorporating the effects of natural ventilation and evaporative cooling (fog-system), is proposed and discussed. Linearization of the greenhouse heat and water balance equations leads to a simple system of two equations with two unknowns (the temperature and humidity differences between inside and outside air) which represent quite well the complex coupling mechanisms between ventilation and fog observed in situ. The model predicts that a minimum inside temperature can be reached for a certain combination of these cooling processes. Crop temperature and transpiration were also estimated using the Penman-Monteith approach and the energy balance of the crop. Good agreement between measured and computed values of air temperature, air humidity, crop temperature and transpiration was observed. From a practical point of view this approach may permit improvement in on-line climate control.