Experimental investigation of pyramid solar still performance enhanced by natural and volcanic pebbles-based thermal storage

Solar stills offer a sustainable solution to water scarcity, especially in arid and remote regions. Among various configurations, pyramid-shaped solar stills exhibit superior performance over traditional basin-type designs, attributable to their augmented condensing surfaces and multifaceted orientations that optimize solar irradiance capture. This study aims to experimentally enhance the performance of a pyramid solar still by integrating naturally sourced gravel and volcanic pebbles as sensible thermal energy storage media. Experimental trials were conducted under the hyper-arid climatic conditions of Ghardaïa, Algeria. The primary objective was to quantify the improvements in freshwater productivity and thermal efficiency achieved using these economical, regionally abundant, and low-cost materials. The volcanic pebble configuration yielded the paramount outcomes, with a distillate production that was 75% higher than that of the conventional pyramid solar still. Under direct natural irradiation the pyramid solar still equipped with volcanic pebbles, reached 30.79°C for the natural gravel configuration still. The thermal efficiency of the volcanic pebble-based pyramidal solar still reached 90%, markedly surpassing the natural pebbles system's efficiency of 62%. This superior performance is attributed to the mineral-rich architecture of the volcanic pebbles, which improves solar energy absorption and thermal heat retention. Furthermore, the pyramidal solar still design proved cost-effective, with a cost per liter of 0.0285 USD/L for the pyramid solar still with pebble integrated variant and 0.0494 USD/L for the conventional pyramid solar still.