Experimental comparison of solar-powered adsorption-based atmospheric water harvesting using air-to-air & water-to-air heat exchanger for condensation

Abstract

Adsorption-focused technologies for atmospheric water harvesting is of great importance. Most of the available systems in the literature use glass as a condenser, which gets heated up. This restricts vapor condensation to harvest less water and hampers the system's scalability. The effectiveness of the proposed solar atmospheric water harvesting system, which uses an air-to-air fin-tube heat exchanger to condense the vapors, is experimentally evaluated in this work. In order to assess the system's effectiveness using a water-to-air fin-tube heat exchanger, a comparison study is also carried out. The experimental setup consists of evacuated tube solar air heater having 8.46 m² area and 15 kg silica gel adsorbent. The performance metrics for comparison include adsorption & regeneration rate, thermal, overall and exergy efficiency, along with economic analyses. The system harvests 1890 mL/day of water using air-to-air heat exchanger at cost of 0.19 $/l, achieving thermal, overall & exergy efficiencies of 21.66%, 2.24%, and 6.51%, respectively. On the other hand, the water-to-air heat exchanger based system harvests maximum of 2680 mL/day of water at a cost of 0.14 $/l, achieving thermal, overall & exergy efficiencies of 25.65%, 3.34%, and 9.13%, respectively. Moreover, the produced water is confirmed to be safe for consumption.