Water Consumption in Hydrogen Production Through Electrolysis: Overview, State‐of‐the‐Art, and Future Trends

Green hydrogen is increasingly positioned to play a transformational role in the decarbonization of the global economy. The number of announced green hydrogen projects is growing rapidly, with a substantial portion located in water‐stressed regions. Commercial‐scale green hydrogen projects rely on PEM and alkaline electrolysis to produce hydrogen from water, powered by electricity generated from renewable sources. The objective of this article is to provide a comprehensive review of water consumption in green hydrogen production, addressing the often‐overlooked implications of freshwater use in large‐scale electrolysis. Water resources represent a critical constraint for hydrogen production, and their availability must be carefully addressed. A review of ongoing green hydrogen projects showed that most of them rely on desalinated seawater, though reclaimed wastewater is emerging as an increasingly attractive alternative source. Currently, PEM electrolysis is the most water‐efficient technology for producing green hydrogen, consuming an average of 17.5 L of water/kg of hydrogen. Of this amount, 51% is used directly in the electrolysis process, while the remaining 49% is allocated to cooling. There are opportunities to improve water efficiency in green hydrogen production by focusing on the optimization of water consumption for cooling. The most relevant ones are the adjustment of the cycles of concentration in cooling towers, the reuse of blowdown water, and the use of adiabatic cooling systems. In coastal areas with favorable bathymetric conditions, the use of seawater could also help lower the demand for cooling water.