Multi-effect distillation: a sustainable option to large-scale green hydrogen production using solar energy

Development of sustainable, gigawatt capacity green hydrogen will require both renewable energy and water inputs, along with careful management of the waste heat produced by these processes (i.e., 9.3–16.7 kWhth/kgH2 for a 70–80% stack efficiency, high heat value). Here we compare the water demands and operating costs for a solar-driven electrolyser facility (powered by solar PV) operating on desalinated seawater produced using reverse osmosis or low-temperature multi-effect distillation. The waste heat was managed via passive cooling, evaporative cooling or through thermal recovery. It was found that the costs for low-temperature multi-effect distillation were up to 85% lower than reverse osmosis and generated 50–270L/ kgH2 of surplus water for ancillary benefit. This work challenges conventional wisdom surrounding the use of membrane desalination for meeting the water demands, offering compelling reasons for thermal desalination to be employed in large-scale production of green hydrogen.