Sustainable and scalable double slope solar still: a comprehensive experimental assessment of energy, exergy, economic, environmental, sensitivity and distillate performance

In double-slope solar stills (DSS), a significant amount of solar energy is wasted as heat and reducing the system freshwater generation efficiency. To overcome this, a reconstructed double-slope solar still (RDSS) with a photovoltaic panel (PV) mounted on top is proposed which facilitates for simultaneous generation of freshwater, heat, and electricity. The PV panel partial shading is reduced by transferring the generated power to a heating element that preheats the inlet saline water, while paraffin wax phase change material (PCM) improves thermal storage. The experimental results indicated that the RDSS substantially enhanced productivity by 92.2%, with energy and exergy efficiencies improvement of 44.2% and 46.9%, respectively. The PV panel peak power output was 47.1 W, and the system had an efficiency of 14.1% (electrical), 37.1% (thermal), 88.5% (heating element), 52.1% (overall energy), and 5.9% (overall exergy). Economically, the RDSS reduced the cost per litre (CPL) of distillate by 17.3% and the payback period (PBP) by 18.2% than DSS which indicating higher financial feasibility. Additionally, the environmental study revealed that the RDSS achieved 98.2% more CO₂ reduction than DSS. In sensitivity analysis, the extending system lifespan from 5 to 25 years lowered production costs by 73.1% at a 2.5% interest rate, but CO₂ mitigation and carbon credit earned (CCE) elevated by 536%. Moreover, the RDSS had a 1.6% higher sustainability rating than DSS, though both systems generated potable water that met world health organization (WHO) requirements. Finally, these findings support RDSS as a low-cost, ecologically friendly and scalable alternative for decentralized freshwater and energy generation.