Experimental and techno-economic evaluation of a pyramid solar still across tilt angles and cover materials in a semi-arid climate

Solar stills are widely used for small-scale desalination, yet their output depends strongly on design and climate. This experimental study quantifies the effects of tilt angle and cover material on the productivity of square-pyramid solar stills under the semi-arid climate of Karaj, Iran. Six configurations were tested, G 30 , G 20 , G 10 (glass covers at 30°, 20°, 10°) and P 30 , P 20 , P 10 (plastic covers at the same angles). In parallel, cost-per-liter analysis was performed based on annualized cost and annual yield formulations, and a comprehensive water-quality assessment of the distillate was conducted. Across the monitoring period, glass covers consistently outperformed plastic covers. The 30° glass configuration (G 30 ) achieved the highest yield, reaching 1.264 L/m²/day on a representative clear-sky day and exceeding G 20 , G 10 , P 30 , P 20 , and P 10 by 19%, 36%, 40%, 81%, and 100%, respectively. Water-quality results showed a ~99% reduction in salinity proxies relative to feedwater, with the distillate meeting potability targets for pH, TDS/EC, turbidity, and major ions. Economic evaluation indicated small differences among glass-covered units: G 30 yielded the lowest CPL at USD 0.0017 L⁻¹, whereas P 20 had the highest at USD 0.008 L⁻¹ due to lower productivity. Overall, optimizing tilt angle and cover material substantially improves productivity, distillate quality, and cost-effectiveness of pyramid solar stills in semi-arid climates. Under Karaj’s conditions, G 30 offers the most favorable trade-off between productivity, water quality, and cost, supporting the broader viability of solar-driven still desalination for decentralized freshwater supply. • A cost-effective square pyramid solar still was developed and constructed. • Solar still productivity can be influenced by design and environmental factors. • The distilled water from this technology is suitable for agriculture and drinking. • The glass cover produces more distilled water than the plastic cover.