Multi-effect distillation for water desalination in an offshore PEM electrolyser system

We study the integration of Multi-Effect Distillation (MED) desalination systems with Proton Exchange Membrane electrolysers (PEMEL) for large-scale offshore hydrogen production. The focus is on utilising the waste heat generated by PEMEL to drive the MED process. The developed quasi-steady-state model shows that MED can consistently meet the water demands of a 1 GW PEM electrolyser, except for electrolyser input power below 5 % of the nominal load. We find that at full load, a large part of the excess heat (up to 94.12 MW) remains uncollected, highlighting a need for further thermal management solutions. For the optimal MED design, we calculate a Gain Output Ratio (GOR) of 3.69, Specific Heat Consumption (SHC) of 631.54 kJ/kg, and a Specific Heat Transfer Area (area per kg/s distillate) of 155.12 m²/kg/s. For this configuration, MED is estimated to occupy a footprint of around 130 m² in a horizontal arrangement, while the 1 GW PEMEL occupies approximately 12000 m². • MED produced 50.64 kg/s water with GOR 3.69, SHC 631.54 kJ/kg using PEM waste heat. • 94.12 MW of excess heat was uncollected, requiring extra thermal recovery solutions. • Water shortage occurred when PEM load was below 5 %, mostly during idle periods. • MED cut disposal temp from 80°C to 41.5°C, reducing thermal impact on seawater. • MED-PEM integration is technically feasible for offshore hydrogen production.