Direct-drive photovoltaic electrodialysis via flow-commanded current control

Abstract

Renewable powered, brackish groundwater desalination is an underutilized resource in the developing world, where there are unreliable energy sources and reliance on increasingly saline groundwater. Traditional renewable desalination technologies require sizable energy storage for sufficient water production, leading to increased cost, maintenance and complexity. We theorize and demonstrate a simple control strategy—flow-commanded current control—using photovoltaic electrodialysis (PV-ED) to enable direct-drive (little to no energy storage), optimally controlled desalination at high production rates. This control scheme was implemented on a fully autonomous, community-scale (2–5 m3 d−1) PV-ED prototype system and operated for 6 months in New Mexico on real brackish groundwater. The prototype fully harnessed 94% of the extracted PV energy despite featuring an energy storage to water productivity ratio of over 99% less than the median PV desalination systems in literature. Flow-commanded current control PV-ED provides a simple strategy to desalinate water for resource-constrained communities and has implications for decarbonizing larger, energy-intensive desalination industries. Desalination of brackish water powered by renewable energy sources is a promising approach to obtain clean water in environmentally constrained communities, but high energy storage requirements hamper its development. Direct-drive photovoltaic electrodialysis is now shown to efficiently produce desalinated water while requiring minimal energy storage.