Experimental investigation and optimization of a solar desalination unit with high heat recovery ratio using weak air compression process

•A novel desalination system with weak air compression is designed and fabricated.•The system performance is experimentally investigated and numerically optimized.•A new performance index defined as gained-output-ratio equivalent is proposed.•The experimental specific electrical consumption can reach up to 9.57 kg/kW·h. With the research objective of verifying the feasibility and improving the performance of the novel desalination system, a solar desalination system with high heat recovery ratio using weak air compression process is designed and fabricated in this paper. The experimental investigation and numerical optimization of the proposed system under different operating parameters of seawater and moist air are conducted. The experimental results in feasibility tests indicate that the system has good producibility of fresh water and self-sustainability. Meanwhile, the fresh water yield and the specific electrical consumption can reach 2.91 kg/h and 4.2 kg/kW·h at the hot seawater temperature of 70°C and the pressure difference of 10 kPa. The recommended mass flow rate of moist air is 0.016 kg/s, and the corresponding fresh water yield and specific electrical consumption are 3.2 kg/h and 4.6 kg/kW·h at hot seawater temperature of 70°C. Compared with the optimization of the humidification process and the control process of pressure distribution ratio, increasing the hot seawater temperature is the most feasible method to improve the increasing extent of specific electrical consumption. The experimental specific electrical consumption and corresponding gained output ratio can be increased to 9.57 kg/kW·h and 6.49 when hot seawater temperature increases to 80°C. Finally, a new performance index defined as gained-output-ratio equivalent is proposed to objectively evaluate the comprehensive performance from thermal and electrical energy. The gained-output-ratio equivalent of the proposed system is up to 2.60, which is one of the best records in similar researches.