Optimization of a hybrid solar still–HDH system via parametric study for lightweight desalination in remote areas

Freshwater scarcity in remote and arid regions necessitates desalination systems that are not only productive but also lightweight, low-cost, and easy to deploy. In this study, a transient numerical model of a hybrid solar still–humidification–dehumidification (SS–HDH) desalination system is used to perform a comprehensive parametric analysis aimed at minimizing system weight while maintaining a target freshwater productivity. Key operational parameters (basin water depth and air mass flow rate) and design parameters (basin material and thickness, glass thickness and material, and absorber material) are systematically investigated under summer and winter climatic conditions. The results show that reducing basin water depth to 0.5 cm and air mass flow rate to 0.1 kg s⁻¹ increases total freshwater productivity by up to 15% compared to the baseline configuration while enabling operation under natural convection. Replacing a stainless-steel basin with black-coated cotton reduces the total system mass from 486.6 kg to 131.7 kg (≈ 73%) with negligible impact on productivity, while minimizing basin and glass thickness further decreases weight without affecting thermal performance. Using aluminum fins and glass covers remains preferable to preserve high productivity, whereas plastic covers and cotton absorbers cause productivity reductions of 10–15%. An optimized configuration increases freshwater production by 31% in winter and 26% in summer relative to the reference case. These results demonstrate that selecting optimal parameters can significantly enhance portability and efficiency, enabling practical deployment of hybrid solar desalination units in off-grid and resource-limited communities.