Enhancing conical solar still performance using black dyed/beige eggshell powder as natural energy storage materials (bio-energy source): experimental approach and 4E evaluation

Abstract

The present study aims to use safe, available, and inexpensive thermal storage materials that can be integrated with conical solar stills to increase water production, add some important elements to the produced water, reduce production costs, and ensure environmental sustainability. This was done by incorporating the eggshell powder into the basins of the conical solar stills. The eggshell powder is characterized by natural, cost-free, effective, and safe thermal energy storage material, which is also an important element for human health. The color of the eggshell powder used in our study is beige, and to increase its ability to absorb solar radiation, it was dyed black. To illustrate the influences of the beige/black dyed eggshell powder on the performance of conical solar stills. A comparative experimental study was conducted by designing, fabricating, and testing a simple conical solar still (SCSS) as a reference unit, a conical solar still with eggshell powder beige (CSS-ESP&Be), and a conical solar still with eggshell powder black (CSS-ESP&Bl). The results showed that adding eggshell powder black (CSS-ESP&Bl) achieved the highest daily cumulative yield of 8.69 L/m² day, representing a 102.1 % improvement compared to SCSS, which had a yield of 4.3 L/m² day. Economically, the eggshell powder black (CSS-ESP&Bl) helps 50.52 % (0.005 vs. 0.0101 $/liter) reduction in water production cost compared to SCSS. Also, environmentally, the use of eggshell powder black (CSS-ESP&Bl) achieved the net mitigation of CO₂ of 36.17 tons. Moreover, carbon credits gained a yield of 524.42 $, achieved a 102 % improvement compared to SCSS.