Psychrometric and ventilation constraints for vapor pressure deficit control

A method is presented for controlling greenhouse air temperature achieving significant energy savings by use of temperature integration. The method is implemented in a commercial greenhouse control system using intelligent tools available in most modern control and management systems. Results compare the proposed technique with standard growersʹ temperature control practice based on simulation of a model greenhouse. Tests against two types of weather show how the energy savings relate to weather spectral characteristics and crop tolerance bounds. The available tools allow the user to define time windows where the temperature setpoint can be either `strictly user specifiedʹ or `model derivedʹ or `float within constraints for energy savingsʹ. The method was developed for immediate application so the grower can define his policy in a simple way, without any requirements for a priori or predicted weather information. Results presented prove the viability of the method and its potential for energy savings.