Experimental and mathematical investigation of a photovoltaic-powered vacuum-assisted solar desalination unit as a component of a proposed zero-liquid-discharge process

Solar-driven desalination represents a sustainable approach for freshwater production and constitutes an important building block for future zero-liquid-discharge (ZLD) systems. In this study, a photovoltaic-powered vacuum-assisted solar desalination unit was experimentally and theoretically investigated as the principal water-recovery component of a proposed ZLD framework. The downstream crystallization and salt recovery units are presented conceptually to illustrate the overall process configuration and were not included in the present experimental validation. Year-long measurements of solar irradiance, ambient temperature, brine temperature, salinity, density, evaporation rate, freshwater production, and energy consumption were collected and compared with theoretical predictions. Good agreement was obtained between the experimental observations and the developed mathematical model. Maximum freshwater productivity was achieved during periods of high solar irradiance, with a peak production of approximately 20.4 kg m⁻² day⁻¹ . The photovoltaic-powered vacuum operation significantly enhanced evaporation while reducing dependence on external electrical energy. The results demonstrate the potential of the proposed solar desalination unit as an effective renewable-energy-driven water recovery technology that can be integrated into future ZLD systems incorporating downstream brine concentration and crystallization processes.