A compact photovoltaic–thermal (PV/T) desalination system : device development and performance optimization

Abstract

Utilizing waste heat from photovoltaic (PV) panels for desalination offers a practical pathway for cascading energy use and addressing the energy–water nexus. A compact photovoltaic–thermal (PV/T) interfacial evaporation desalination system was developed that integrates capillary-driven evaporation, membrane distillation, and condensation directly into the PV panel assembly. The system harnesses the waste heat from the PV backsheet (typically accounting for 80%–85% of incident solar energy) to drive water evaporation through a cotton fabric wick, while a distillation membrane separates vapor from brine. A SiO₂-nanocoated aluminum condenser with high hydrophobicity (contact angle 107.9°) is equipped with sea–island fiber guides and dual bottom outlets, achieving a freshwater collection efficiency of over 90%. Indoor experiments at three inclination angles (5°, 15°, and 25°) under controlled irradiance conditions (400–1000 W/m²) show that the inclination angle has no significant effect on freshwater productivity under constant irradiance. Outdoor testing in Hong Kong at a fixed 22° inclination yielded a cumulative daily freshwater production of 1.73 L/m² and a daily GOR of 0.348. Sun-tracking mode, achieved through manual surface azimuthal adjustments every 10 min, increased incident irradiance by 23.5%, GOR by 5%, and the daily water yield by 53.8% to 2.66 L/m². This compact, cost-effective system offers a practical solution for distributed solar desalination, particularly in water-scarce, sun-rich regions, and demonstrates the potential for efficient utilization of solar energy.