Solar driven atmospheric water harvesting system with integration of desiccant wheel and desiccant bed: An experimental investigation

Solar-driven atmospheric water harvesting (SDAWH) presents a promising solution to address water scarcity issues, particularly in arid and semi-arid regions where conventional water sources are limited. This paper presents a new SDAWH system, integrated with a desiccant wheel and desiccant bed. The desiccant bed adsorbs water vapour during night and desorbs in a day time. Whereas the desiccant wheel performs adsorption and desorption process simultaneously in day time. Therefore, the combination of these offers the potential to enhance water yield and energy efficiency compared to conventional sorption-based SDAWH systems in semi-arid climate. Further, an evacuated tube solar air heater for regeneration and an air-to-air heat exchanger for condensation of water vapour has been integrated. The desiccant bed releases large amount of water vapour in regeneration air but its desorption gradually decreases with time. On the other hand, the desiccant wheel releases a lesser quantity of water vapour into the regeneration air, but its desorption capacity remains almost constant. The system's performance has been evaluated in a semi-arid climate. As the system is working in closed cycle, the dew point temperature of regeneration air obtained at the outlet of the desiccant wheel is 39.4 degree celsius, which increases to 42.4 degree celsius at the outlet of the desiccant bed. The total yield of water in a day is 7.6 L, with an energy efficiency of 9 %.