Efficient management of a dehumidifier in a greenhouse under warm weather conditions

Abstract

The reduction of humidity inside a greenhouse is a key factor to ensure the quality of the crop and avoid the incidence of cryptogamic diseases. The method commonly used is a combination of heating and natural ventilation, although it is very deficient from the energy and environmental points of view. In cold and humid climates the use of a heat pump dehumidifier (HPD) can reduce energy consumption. To evaluate this technology in a Mediterranean climate, an HPD was installed in a greenhouse of the Cajamar Experimental Station in Almería. The environmental humidity inside the greenhouse decreased when using the HPD. The efficiency of the HPD was related to the value of the condensation temperature of the water vapor and to the temperature and humidity of the air inside the greenhouse. In addition, it was found that the energy efficiency of the system varied according to climate. For efficient management of HPD it is essential to know the influence of climate on energy efficiency. The flow of condensed water vapor and the power consumed presented differing behaviors. Thus, the production of liquid water correlated linearly with the condensation temperature, increasing the slope of the linear relationship with the temperature of the air inside the greenhouse. However, the power consumption was correlated linearly with the air temperature. The management of the system is efficient when the air temperature is above 15.0ºC and the relative humidity is less than 90%.