Techno-Economic Optimization of Autonomous PV/Wind/Battery Microgrid for Seawater Reverse Osmosis Desalination Plant

Seawater reverse osmosis desalination (SWROD) powered by renewable microgrid offers a sustainable pathway to meet community freshwater demand. However, optimizing off-grid system remains challenging due to the intermittency of solar and wind resources, and the variability of water consumption. This study develops a hybrid battery-tank storage model integrated with microgrid for SWROD operation to balance surplus renewable energy and deficit water demand. A fuzzy-genetic algorithm (FGA) minimizes the levelized cost of water (LCOW) with optimal component sizing while satisfying reliability constraints defined by the loss of water supply probability (LWSP). Mamdani fuzzy logic for multi-criteria decision-making comprises 27 rules implemented in MATLAB and utilizes the coefficient of variation to adaptively tune the GA parameters. A case study in Saudi Arabia evaluates six configurations based on five decision variables: SWROD capacity, water tank, PV panel, wind turbine, and battery storage. Results show that incorporating water tank significantly lowers LCOW by reducing reliance on battery storage while maintaining system reliability. Among the evaluated configurations, the PV/Wind/Battery/Tank topology proves to be the most cost-effective in terms of community-scale water supply, achieving an LCOW of 1.2004 $/m³. In contrast, systems lacking tanks or relying solely on wind exhibit higher LCOW, excess renewable energy and unmet water demand with reduced reliability factor. Project sensitivity analyses further reveal that water demand variability exhibits a stronger influence on LCOW than solar irradiance or wind speed. Overall, the proposed framework demonstrates the techno-economic viability of standalone renewable-powered desalination systems, enabling cost-effective and reliable freshwater supply for coastal communities.