Approximately 43% of all planned global capacity for “green” hydrogen production could face serious challenges due to water scarcity. Moreover, about one-quarter of announced projects – amounting to nearly 10.7 GWt of total capacity – are already slated for construction in regions that simultaneously exhibit high water consumption for electrolyzer cooling and significant freshwater deficits. This is the conclusion reached by researchers from Research Center Jülich, Rein-Westfahl Aachen University, and the University of Siegen in Germany, who for the first time conducted a comprehensive assessment of how equipment cooling affects the water footprint in hydrogen production.
Until now, global strategies for hydrogen-energy development have considered only the water directly required for electrolysis. It was assumed that producing one kilogram of hydrogen consumes about 9 liters of water, or roughly 10 – 12 liters when including water purification. However, this captures only part of the overall picture.
The reason is that electrolyzers release substantial amounts of heat during operation. If this heat is not dissipated, the equipment overheats and loses efficiency, necessitating continuous cooling. Cooling towers are most commonly used for this purpose, where water evaporates and carries away excess heat. It is at this stage that the main additional water consumption occurs.
To determine the scale of this consumption, the researchers developed a model that accounts for air temperature and humidity, regional freshwater availability, and the potential for solar and wind energy generation.
The findings show that in cold regions, producing one kilogram of hydrogen requires an average of about 19 liters of water. In hot areas, such as North Africa, the Middle East, Australia, and South Asia, this figure rises to 39 liters. Almost all of the additional volume is consumed by cooling. Moreover, during the hottest months, water consumption can increase by roughly another quarter. As a result, some regions that experience no serious shortages for most of the year find themselves in acute water deficit during summer.
The researchers then cross-referenced water consumption with regional water availability and calculated a Water Risk Index for each area. This index revealed that nearly half of all planned hydrogen production capacity falls within territories at maximum risk. These include the Middle East, North Africa, Central Asia, the interior of Australia, and the southwestern United States, precisely where some of the world’s largest hydrogen projects are currently under development, namely NEOM in Saudi Arabia, Hyphen in Namibia, and Pilbara in Australia.
Next, the researchers compared the water-risk map with areas most suitable for solar and wind farm construction. It turned out that more than 63% of territories with the highest solar potential also fall within zones of maximum water risk. This means that the primary obstacle to building solar-powered hydrogen complexes is no longer land availability or even the number of sunny days, but rather access to freshwater. The situation looks considerably better for wind energy: only 44% of the best sites fall into high-risk zones, and nearly one-third are located in regions with sufficient water reserves. This is explained by the fact that the most favorable wind areas are typically found in cooler, more humid climates, where cooling requires significantly less water.
In the researchers’ view, it is no longer acceptable to select sites for future hydrogen plants based solely on cheap solar or wind energy. In arid regions, they recommend using dry or hybrid cooling systems, as well as desalinated seawater or treated wastewater.
At the same time, the authors argue that it would be prudent to assess green hydrogen projects not only by their carbon footprint but also by their water footprint. Otherwise, in a number of regions, the expansion of hydrogen energy could further exacerbate pressure on already limited freshwater supplies.
