Mechanistic modeling and thermo-economic analysis of phase change material-enhanced solar-powered membrane-based humidification-dehumidification desalination system

The escalating global freshwater scarcity, exacerbated by climate change and population growth, underscores the critical need for sustainable desalination technologies. This study presents a novel phase change material (PCM)-enhanced solar-powered membrane-based humidification-dehumidification (HDH) desalination system to address the inherent limitations of conventional systems, like intermittent operation due to solar dependency. A mechanistic model coupling heat and mass transfer was developed and validated to simulate the system behavior under the climatic conditions of Sansha City, Hainan Province, China, a region characterized by abundant solar radiation (>7.4 kWh/m2/day) and severe water deficits. The simulation results demonstrate that PCM integration extends daily operation from 12.75 h to 15.75 h, boosts freshwater production by 17.45% (from 20.86 kg to 24.50 kg), and elevates solar energy utilization efficiency from 52% to 57.62%, with an overall exergy efficiency of approximately 8.02%. A comprehensive thermo-economic analysis was also performed and the simulation results reveal robust profitability of the solar-powered HDH system: freshwater costs are $5.14/m3 (with PCM) and $3.38/m3 (without PCM), payback periods are 2.10 and 1.24 years, net present values reach $896 and $830, and internal rates of return exceed 46.92% and 79.74%, respectively. Despite the higher unit cost and longer payback period, the PCM-integrated system achieves a higher NPV, mainly due to increased freshwater yield and extended operating duration, indicating superior long-term techno-economic performance. Furthermore, the scenario and sensitivity analyses confirm financial resilience under ±10% market fluctuations, with IRRs consistently doubling the required return rate (13.23%). The PCM-based HDH system emerges as a technologically advanced and economically viable solution for solar-rich, water-scarce regions, offering enhanced reliability, sustainability, and investment potential. This work provides critical insights for optimizing decentralized desalination systems and advancing energy-water nexus strategies.