Proton Exchange Membrane Water Electrolysis is a method to split water into its components, hydrogen (H₂) and oxygen (O₂), using electricity typically sourced from renewables. It is one method for producing so-called green hydrogen. Key benefits are that it can easily start and stop, fitting well with fluctuating renewable energy sources; it produces high purity hydrogen suitable for fuel cells and industrial use; and it has a smaller carbon footprint than some alternatives.

This work explores how much water is used in Proton Exchange Membrane Water Electrolysis, which is significant in regions with low water availability, where hydrogen plants could stress supplies. The researchers looked at all lifecycle stages: manufacturing (building the electrolyser and producing materials), operation (water splitting, cooling, and purification), and end-of-life (disposal or recycling).

Their main conclusion was that most water use occurs during the operational phase, where the greatest opportunity to save water lies. Dry cooling uses much less water than wet cooling, reducing consumption by about a factor of three. In a best-case scenario with dry cooling, about 13 litres of water per kg H₂ is used, of which around 3.5 litres is lost in water treatment. This loss can be reduced by about 50% using a brine recovery system, depending on location and infrastructure.

Proton Exchange Membrane Water Electrolysis has a similar lifecycle water use to fossil hydrogen production, therefore switching to green hydrogen does not significantly increase water demand. Although hydrogen plants use comparable water to agriculture (e.g. corn farming), they generate much higher economic value per unit of water (~700×), making them an efficient use of water.

This research is significant because it shows that while green hydrogen can reduce carbon emissions, its water use must be carefully managed to ensure it is sustainable at scale.

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Research and development of hydrogen carrier based solutions for hydrogen compression and storage Martin Dornheim et al. (2022)