System-level assessment of electrodialysis desalination as a flexible Power-to-Water load in isolated renewable islands

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Chinese explanation / 中文解读

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Original abstract

The large-scale integration of renewable energy sources in isolated power systems often results in significant electricity surpluses, while freshwater production remains highly energy-intensive and dependent on fossil fuels. This study proposes and assesses a Power-to-Water system that converts surplus photovoltaic electricity into potable water through electrodialysis desalination. The system is applied to Lampedusa Island, Italy, a remote Mediterranean island not connected to the mainland grid and currently supplied by diesel-based power generation and reverse osmosis desalination. The proposed layout integrates a 22 MW photovoltaic field, a 4.62 MW electrodialysis plant, 25 MWh lithium-ion battery storage, a freshwater storage basin, and a biodiesel production chain based on microalgae cultivation to further reduce fossil fuel consumption. A comprehensive dynamic model of the integrated energy–water system is developed in TRNSYS using high-resolution load profiles and component-level models. Simulation results show that the proposed configuration covers 99.35% of the island’s electricity demand through renewable electricity and supplies the entire freshwater demand through renewable-powered desalination. In particular, 97.46% of the freshwater demand is produced through the Power-to-Water strategy, while the remaining share is covered by the backup operation of the electrodialysis unit. Compared with the reference configuration, the proposed system achieves a primary energy saving of 92.62%, reduces operating costs by 34.09%, and reaches a simple payback period of 8.6 years. The levelized cost of electricity decreases to 0.160 €/kWh, while the levelized cost of water is 3.66 €/m 3 , slightly higher than the reference reverse-osmosis-based configuration. The results indicate that electrodialysis-based Power-to-Water systems can provide system-level value in isolated renewable islands by acting as flexible loads for surplus renewable electricity, although their practical deployment remains dependent on technology maturity, component costs, and site-specific constraints.

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