Optimization of atmospheric water harvesting cycles for sustainable water supply in arid regions

Water shortages in arid areas threaten daily human needs. Extracting water from moist air offers a promising solution for communities facing water scarcity in these areas. This study theoretically evaluates the performance of six different adsorbent materials used for atmospheric water harvesting (AWH). A comprehensive parametric analysis is performed to assess the impact of various operating conditions on key performance indicators, including water yield (WY), energy consumption (EC), and cycle thermal efficiency. Additionally, the study evaluates the adsorption uptake of six adsorbents under varying temperatures and relative humidity levels, mapping the estimated adsorption capacities onto a psychrometric chart. This approach helps identify the most suitable adsorbents for different climatic conditions. Moreover, the response surface methodology is applied in this study to develop a regression model, optimize AWH cycle performance using a desirability optimization technique, and evaluate the most significant design factors affecting the WY and cycle efficiency. Optimization is conducted for two adsorbents, silica gel RD and MOF MIL-101(Cr). The results show that MOF MIL-101(Cr) can achieve a water yield of up to 1.08 kg_water/kg_ads/cycle, alongside a cycle efficiency of 79.3 %, whereas silica gel RD exhibits a water yield of up to 0.429 kg_water/kg_ads/cycle with an efficiency of 79.6 %. This study is essential for designing efficient AWH systems.