Efficiency assessment of a solar heating cooling system applied to the greenhouse microclimate

The solar thermal storage is an important issue for greenhouse applications in winter period. For the reason that greenhouse operations, such as heating and cooling, consume a large amount of energy. The thermal storage is important to minimize the cost of greenhouse production. Surplus air thermal energy (SATE) is available in greenhouses during all the year, even in the cold period, hence its use in greenhouse applications is possible. In this present work, a solar heating cooling system (SHCS) with quartzitic sandstone as thermal storage material to store and use the SATE in greenhouse production was operated for cooling and heating processes and its performance was evaluated during winter period. This system consists of a quartzitic sandstone and including thermal storage blocks and pipes with fans to manage those processes in greenhouse. This system was located in the Souss-Massa region, Morocco. The heating and cooling of inside air by SHCS can improve the greenhouse microclimate and tomato yield. The results show that the air temperature in greenhouse equipped with SHCS exceeds than that of the control one about 3 °C at night and 6 °C lower during day, with fewer fluctuations. Moreover, the relative humidity was 10% lower at night. The SATE stored was varied between 15.68 and 140 MJ/day in plastic greenhouse with an area of 165 m2 during day, and 65% of this heat recovered at night. The SHCS was improved the tomato yield about 1.74 kg/m2 than that of normal production. An economic analysis revealed that this system is very profitable and could generate profits for farmers.