Design and simulation of an off-grid marine current-powered seawater desalination and hydrogen production system

The use of marine current energy to provide a stable supply of energy and fresh water to islands and remote areas is a promising prospect. In this study, an integrated marine current-powered seawater desalination and hydrogen production system was proposed. For higher integration and efficiency, the generator and seawater pump were integrated into the nacelle and mechanically connected to the main shaft. Four operating modes and the corresponding start-stop and maximum power point tracking (MPPT) control strategy were designed to achieve energy distribution between the two loads. Considering the frequent start-stop caused by the sinusoidal characteristic of marine current energy, a soft start-up process was designed for the RO elements, including dual hydraulic accumulators and a smooth transition process to avoid abrupt changes in feed pressure and feed flow rate. Finally, the performance was obtained by simulation. During the 6 hours of the ebb tide, the desalination system produced a total of 841.77 L of fresh water, while the electrolyzer produced 1038.5 SL of hydrogen and consumed 0.95 L of water. The average power coefficient of the turbine was 0.434, and the specific energy consumption of the desalination system was 2.03 kWh/m3, indicating good MPPT performance and high efficiency.