Performance evaluation of different configurations of solar humidification-dehumidification desalination system with subsurface condenser

Abstract

The solar humidification-dehumidification desalination system with a subsurface condenser is a promising renewable energy-based desalination system. This desalination system is particularly suitable for condensation irrigation in greenhouses, especially where conventional energy sources are limited. A computational model of the system comprising a horizontal solar film evaporator and a subsurface condenser is developed. A previously proposed hybrid analytical–numerical model for horizontal ground heat exchangers is modified for the subsurface condenser. An experimental setup of the subsurface condenser is also built and used to verify the developed model of the subsurface condenser. The developed model is then used to evaluate the long-term performance of several closed-loop configurations of the system and compare it with an open-loop system. It is demonstrated that the average daily water yield and Gained Output Ratio (GOR) of the closed-loop system are 115 % and 127 % higher than the open-loop system, respectively; however, the ground temperature increases significantly, which can lead to decreased respiration and root growth. According to the simulation results, using the air-cooled condenser, internal heat exchanger, and the hybrid system with both the air-cooled condenser and internal heat exchanger enhances the freshwater produced and GOR by 6.0 %, 6.3 %, and 10.8 %, respectively. The hybrid system outperforms other configurations and leads to only a 2.0 °C increase in the ground temperature over ten years of the system operation.