Thermal solar collectors and absorption system applied to greenhouse cooling

Greenhouse microclimate depends on climatic parameters, such as solar radiation, air temperature, relative humidity and wind speed. The management of the greenhouse environment aims to ensure suitable growing condition for the crop, energy savings, and also safety condition for the workers. Solar absorption systems, exploiting renewable energy sources, can be applied for greenhouse cooling in regions with high values of solar irradiation in which evaporative systems are generally used; nevertheless evaporative systems require large quantity of water that is often a scarce natural resource in Mediterranean areas. The paper presents the technical considerations on the application of thermal solar collectors and an absorption system for cooling a greenhouse in the Mediterranean area. The simulation study was realized based on the data collected at the experimental centre of the University of Bari, Southern Italy, aiming to control the air temperature of a greenhouse having a surface of 300 m2. The study aims to delineate the solar collector surface related to the greenhouse cultivated area and the potential of the system in terms of cooling capacity and energy consumption. The designed system consists of 60 m2 of evacuated-tube solar collectors, a single-effect absorption chiller having a cooling capacity of 18 kW and a pilot distribution system, which provides the cooling power for the air volume surrounding the crop. The simulation showed that the delivered yearly cooling capacity for the greenhouse was 113 GJ, the required solar energy 157 GJ and the available solar energy 234 GJ.