A floating planting system based on concentrated solar multi-stage rising film distillation process

Abstract

This work presents a floating planting system based on multi-stage rising film distillation process driven by concentrated solar energy. The proposed system applies desalinated freshwater to directly irrigate hydroponic crops, which saves land area and takes advantage of ocean resources. The hydrophilic wick is selected as the evaporator to form a rising seawater film by capillary suction. Through the vertically arranged multi-stage evaporation and condensation units, the latent heat of vapor can be recovered effectively. To obtain the maximum optical efficiency, the optical simulation of the concentrating section is carried out. Based on optimized structure, an experimental system is built to investigate the effects of different operating parameters on the internal temperature, water production rate, gained output ratio (GOR), and exergy efficiency. Under indoor steady-state conditions, the temperature difference of desalination units is found to be progressively larger under increasing irradiance. In addition, the system could achieve 1.7 of GOR and 6.1% of exergy efficiency with 900 W/m2 irradiance. Results at actual weather reveal that the daily water yield of the system could reach 9.51 kg/m2/day under azimuth tracking condition, which is 97% higher than the fully passive operation condition. Finally, under 28 consecutive days of operation, the average growth height of lettuces cultivated by the system is 13.7 cm.