Performance Evaluation of a Solar Cooling Plant Applied for Greenhouse Thermal Control

The greenhouses cultivation causes in summer season inner conditions characterized by high thermal levels such as to generate problems that can damage crops. Always more frequently for this reason it is common to provide greenhouse with air conditioning plants. In this work it will be presented an application of a solar cooling plant with absorption cooling machine for thermal control of a greenhouse and an advanced simulation model able to evaluate optimal plant configurations and controls. Solar cooling systems can be applied for greenhouse climate control in regions with high values of solar irradiation as alternative to traditional evaporative systems, allowing the reduction of primary energy consumption by exploiting the contemporaneity between the cooling requirements and the solar energy availability. The plant consists of a single effect LiBr-H2O absorption chiller fed by evacuated-tube solar collectors; the model was developed in Matlab-Simulink and is able to simulate dynamically, with time steps up to 15 minutes, the greenhouse cooling demand and the production of the solar field. Present study proposes a plant configuration with a distribution system in which the cooling power is not provided for the entire volume of the greenhouse, but only for the air volume surrounding the crop with a considerable saving of reduction of energy demand and an extremely efficient use of solar energy. The simulation study is based on the experimental data collected at the experimental center of the University of Bari, Southern Italy. The aim of the work is to demonstrate that solar cooling system could provide significant energy-saving opportunities for cooling greenhouses allowing the reduction of primary energy consumption by exploiting the contemporaneity between the cooling requirements and the solar energy availability.