Investigation of silica gel performance on potable water harvesting from ambient air using a rotatable apparatus with a solar tracking system

Abstract

Over the last century, the scarcity of clean water has emerged as a critical global issue. The changing climate and many other factors have severely strained the world’s water resources. As a result, much research has been conducted to find various methods to supply clean water, like water generation from atmospheric air. Many studies have been done in this field, but there is still a need for further developments to enhance the water generation process. So, in the current study, a single-slope apparatus was designed and constructed to study potable water collection from the atmospheric air. The experiments were done in Kirkuk, Iraq (35.4666°N and 44.3799°E). Blue silica gel beads were used as a desiccant material, and solar intensity as a heating source. The process consists of adsorbing moisture at nighttime, regenerating the moisture and condensing the vapour to generate water droplets in the daytime. The apparatus consists of two identical sections isolated from each, having dimensions of 56 cm3 × 68 cm3 × 82.5 cm3 for each. Both sections were used simultaneously to test the silica gel performance in water generation. An acrylic sheet was used as a condensing surface, and solar tracking equipment tracked the sunlight throughout the day using a DC motor to rotate the device with the sun’s movement. An internal reflector made of aluminium was installed on all apparatus walls to increase the desiccant temperature. Testing the apparatus with and without the internal reflectors simultaneously revealed that using them can raise the desiccant temperature by nearly 30°C. The find-ings of several test days in September revealed that the maximum accumulated productivity equals 107 g/m2·d, the system’s maximum thermal efficiency was 22%, and the yearly cost of producing water was 2.54 $/L. Although the relative humidity is low in Kirkuk, 107 g/m2·d has been collected. It is possible to reach higher water production levels if this process is used in another location with high relative humidity. Also, this device is a prototype constructed for tests only, so in case of enlarg-ing the dimensions of the apparatus, a larger quantity of desiccant can be used, and a much higher amount of water can be produced. In both cases, the cost of producing water will be much reduced. © 2023 Desalination Publications.