Water and heat recovery for greenhouses in cold climates using a solid sorption system

Greenhouses are basically used to create a protected growing environment for crops. In winter climates, cold air temperature and high humidity level are two major problems for greenhouse production, which induce plant diseases and yield losses. In this research, we proposed a climate control system which integrates solid sorption and sensible thermal storage. During the sorption phase, indoor vapor was captured by sorbents while sorption heat was used to increase the air temperature. During the desorption phase, vapor was released and condensed into liquid water. Heat exchanged through the water-cooling condenser was recovered and stored for nocturnal space heating. In the comparative filed experiments, pure silica gels (SG) and composite sorbents CaCl2@SG were chosen as sorbent materials, respectively. During experiments using SG, the averaged nocturnal air temperature was increased by 3.23 °C and the averaged nocturnal relative humidity was decreased by 16.91%. During experiments using CaCl2@SG, the changes were 2.58 °C and 17.39%, respectively. Moreover, CaCl2@SG significantly decreased the averaged humidity ratio by 0.40 g/kg, while SG imposed tiny effect on this parameter. The energy-saving effect of the prosed system was further discussed through simulation.