Techno-economic and environmental assessment of photovoltaic-powered electrodialysis with operating-window selection for brackish water desalination

This study develops an electrodialysis (ED)-centered techno-economic and environmental framework for brackish water desalination in Saudi Arabia. The ED process is first analyzed through a sequential operating-window selection procedure based on spacer configuration, product-water salinity, and flow velocity in terms of specific energy consumption, membrane area, stack length, number of cell pairs, and current density. Spacer A, a product salinity of 350 ppm, and a flow velocity of 0.10 m/s were selected because they provide a practical compromise between drinking-water quality, energy consumption, membrane-area requirement, and stack compactness. Under these conditions, the ED design envelope was mapped over permeate production rates of 200–500 m³/d and feed salinities of 1000–10,000 ppm. The required ED load increased from about 0.6 to 20.7 kW, while the membrane area increased from approximately 55 to 1500 m². These increases were driven by the combined effects of higher permeate production rate and higher feed salinity. The optimized ED load was then used to assess four power-supply configurations: hybrid PV-grid, fully renewable PV-battery, grid-only, and diesel-only operation. For the Dammam baseline case, the fully renewable configuration achieved the lowest annual carbon emissions of 2.71 tons/year with a competitive water cost of 0.21 $/m³. The results show that ED process optimization should precede renewable-energy sizing for reliable low-carbon desalination.