Effect of ambient conditions on the performance of solar-powered atmospheric water harvesting system based on desiccant wheel: An experimental investigation

Abstract

The whole world is facing a serious freshwater crisis as the existing sources are rapidly depleting. There is an urgent need to explore a new and sustainable source of potable water to meet the current demand. Solar-powered atmospheric water harvesting (SP-AWH) is an innovative approach to extract water vapor from ambient air as drinking water. Most of the SP-AWH system available in the literature are based on desiccant bed & flat plate collector. These systems are facing limited adsorption capacity of desiccant bed and lower efficiency of flat plate collectors. The present system uses a desiccant wheel for adsorption, an evacuated tube solar air heater for the regeneration of desiccant wheel, and an air-to-air heat exchanger for the condensation of water vapor. The system is operated daily for seven consecutive days under various ambient and operating conditions. The investigation shows that the increase in DBT of ambient air and decrease in humidity ratio severely affected the performance of the SP-AWH system. Under the ambient conditions (i.e. 36 °C DBT and 20 g/kg_da humidity ratio) and operating condition (i.e.113 °C regeneration temperature and 144 kg/h air flow rate) this system achieved a water productivity of 8.6 L in a day. Further, by increasing the regeneration air temperature by 10 % the system's daily yield reaches 9.55 L in a day. Increasing the process air flow rate from 144 kg/h to 180 kg/h improved the water productivity to 10.34 L in a day with an energy efficiency of 10.2 %.