An augmented pyramid distiller combining thin-film evaporation, reflectors, water heater, and cover cooling: Thermo-economic-environmental approach

Abstract

This paper presents a pyramid solar still with modifications to enhance energy, exergy, economic, and environmental performance, comparing a conventional distiller to a modified version with advanced features for improved efficiency. The system incorporates several innovative features to enhance performance. First, it includes a pyramid-shaped distillation unit integrated with evacuated tube technology with 200 L capacity storage, utilizing thin-film evaporation through a black jute structure for improved heat transfer. Second, four flat reflectors are strategically positioned around the pyramid distiller, aligning with the water heater to focus additional solar energy onto the system, further boosting the thin-film evaporation process. Lastly, a water cover cooling system, operating at a rate of 4 L per hour, was incorporated to regulate the increased evaporation rate resulting from these enhancements. The three modified distillers attained a daily yield of 5.78, 7.31, and 9.36 L/m2 while the reference distiller did not exceed 3.32 L/m2. In other words, the modified distillers achieved productivity improvement ratios of 83.49, 120.18, and 193.42 %. The last case (best case) achieved daily exergy and energy efficiencies of 5.16 and 48.82 %, respectively, which was higher than those of the reference distiller by 125.60 and 43.42 %, respectively. Considering the heat transfer coefficients, the last case exhibited a daily average value of 59.89 W/m2·K which was 146.36 % higher than the reference distiller. From an economic and environmental perspective, the last case reduced the cost of water to 0.0124 $/L along with carbon dioxide mitigation of 5.64 tons CO2. © 2025 International Solar Energy Society