Design, performance, and enviro-economic analysis of a solar-powered membrane distillation system for efficient water production

Freshwater scarcity is a growing global challenge driven by population growth, industrialization, and climate change, particularly in arid and semi-arid regions, necessitating the development of sustainable and energy-efficient desalination technologies. However, conventional seawater desalination systems are energy-intensive and environmentally impactful, limiting their applicability in off-grid and energy-scarce regions. To address this challenge, the current study aims to design, model, and optimize a solar-powered membrane distillation (SPMD) system by integrating an evacuated tube solar collector (ETC) with a direct contact membrane distillation (DCMD) unit for efficient seawater desalination. A comprehensive mathematical model is developed to simulate heat and mass transfer processes in both the collector and membrane unit, and the system performance is evaluated under varying membrane areas, tank sizes, and feed flow rates. Increasing the membrane area from 0.5 m² to 2 m² enhances daily water production, with improvements of up to 56.8 % for a 6 m³ tank at 30 L/min. For smaller tanks (2 m³), an optimal membrane area is observed at low flow rates, where productivity increases by about 25 % (0.5–1 m²) before declining due to thermal limitations. The system demonstrates strong economic feasibility, achieving an energy payback time (EPBT) of 1.6 years and a minimum unit production cost (UPC) of $17.4/m³. Environmental analysis indicates significant CO₂ mitigation of up to 7850 tons, with a Life Cycle Conversion Efficiency (LCCE) of 0.38 and improved Energy Production Factor (EPF) under extended operation. Overall, the proposed SPMD system provides an energy-efficient, cost-effective, and environmentally sustainable solution for seawater desalination in coastal and off-grid regions, with performance strongly influenced by system design and operating conditions.