Experimental study on water extraction from atmospheric air using tubular solar still

Abstract

For the first time and as alternative source of bootable water, water extraction from atmospheric air using tubular solar still was tested experimentally under extremely low humid air conditions (12%) of Hail city, Saudi Arabia (27.64 oN, 41.75 oE). A rectangular trough filled with black cotton cloth bed filled with calcium chloride desiccant was used. The device is equipped with a small air fan to circulate ambient air inside tube at night hours (absorption process). The absorption process was tested under 5 different air speed conditions (natural, 0.5, 1, 3 and 4 m/s). The fan removed and the tube sides closed during day hours causing evaporation of the water from desiccant solution, the vapour condensed on the inner tube surface (regeneration process) and extracted outside the device. The evaporated water was measured at the end of the regeneration process. Results revealed a maximum water production of 467 mL/m2day for 4 m/s air speed with 25% thermal efficiency, while the minimum production was 230 mL/m2day for natural air circulation with 12.2% thermal efficiency. The water production cost was US $0.4/L for natural air circulation and US $0.2/L for 4 m/s air speed. The present study proofed the feasibility of water extraction from low humid regions in desert places. The proposed device still needs more research effort to be mature enough. The proposed device can be used directly in desert places without any need for infrastructure.