Optimization of pyramidal solar still operation using floating absorbers, mirrors, and nanomaterial-enhanced PCM: experimental analysis and economic evaluation

The conventional pyramid solar still (PSS) suffers from low thermal efficiency and limited freshwater yield due to inadequate solar energy utilization and heat losses. To address these challenges, this study introduces the Floating Absorber Pyramid Solar Still (FAPSS), a novel design that employs buoyant cork elements as floating absorbers to enhance solar energy capture. Each absorber consists of a black-coated sheet metal panel and a hydrophilic wick that ensures continuous water transport via capillary action. Three configurations with four, six, and eight absorbers (FAPSS‑4A, FAPSS‑6A, FAPSS‑8A) are evaluated, and the optimal FAPSS‑6A design is further enhanced by external mirrors to amplify incident radiation, an electric fan for vapor extraction, and a silver‑nanoparticle‑enhanced phase change material (Ag‑nano‑PCM) for thermal energy storage. The dual‑phase thermal management stabilizes the system under varying irradiance and extends operation into nighttime hours. Experimental results show that FAPSS‑6A with reflectors and fan achieves a daily freshwater yield of 10,600 mL/m2 ·day – an increase of 194% in yield over the conventional PSS – and a thermal efficiency of 62%. Incorporating Ag‑nano‑PCM further raises the yield to 11,300 mL/m2 ·day, representing a 182% improvement. Economic analysis reveals a substantial reduction in water production cost: 0.011 $/L for FAPSS with reflectors and fan, and 0.012 $/L for the configuration with PCM, compared to 0.024 $/L for the conventional PSS. The proposed FAPSS system thus offers a highly efficient, cost‑effective, and sustainable solution for decentralized solar desalination. The work demonstrates a strong commitment to advancing the United Nations SDGs (Sustainable Development Goals), particularly Clean Water and Sanitation (SDG 6).