Green hydrogen at sea cheaper, more sustainable

Researchers from Wageningen University & Research have shown that the production costs of green hydrogen via electrolysis at sea can be reduced by making Ultra-Pure Water (UPW) on-site using membrane distillation. This ultra-clean water is essential for converting wind energy into 'green' hydrogen.

Researchers from Wageningen University & Research have shown that the production costs of green hydrogen via electrolysis at sea can be reduced by making Ultra-Pure Water (UPW) on-site using membrane distillation. This ultra-clean water is essential for converting wind energy into ‘green’ hydrogen.

With this research, a demonstration prototype on Texel showed that ultra-pure water could be made from seawater with residual heat released during water electrolysis (for hydrogen production). Jolanda van Medevoort, the project leader of this research and researcher within the Water Treatment & Technology program, is delighted that this pilot has been completed successfully.

“This makes the business case for green hydrogen more competitive, which is desperately needed. At the moment, green hydrogen cannot compete with grey hydrogen produced with fossil energy. And what is just as important is that the membrane distillation process is also more environmentally friendly than reverse osmosis, which is now often used. Membrane distillation uses much less electrical energy because it applies the residual heat from the electrolyser. It is also more environmentally friendly because no chemicals are needed for pre-treatment seawater. Also, in contrast, seawater hardly becomes saltier to reverse osmosis (RO), which means that the underwater environment is unaffected. Of course, no drinking water has to be used for this process.”

Ultra-Pure water with membrane distillation

The membrane distillation process to produce clean water from seawater is not new because it requires a lot of heat and energy. It is not the most economically feasible solution for all applications, but in this case, it is. The heat produced by the Electrolyzer must be dissipated quickly for the electrolysis process to run smoothly.

Using this heat for membrane distillation, cooling with seawater is no longer necessary. The ultra-pure feed water for the electrolyser is immediately produced. The costs of Ultra-Pure Water will be lower than the application of reverse osmosis (RO). This lowers the overall electrical efficiency of the entire hydrogen system. This is because reverse osmosis is an electrically driven process.

The main results of the project

The main result is the working proof of the technological principle by building an operating membrane distillation system, integrating it with the electrolyser and demonstrating the combined system on the dock of Seaport Texel.

The photo below shows the installations at the demo location. The electrolyser and membrane distillation installations are both built into containers to transport them to the demo location on Texel. The electrolyser of project partner Hydron Energy in the blue container and the grey/white adjacent to the membrane distillation installation of Wageningen Food & Biobased Research. The seawater intake (Pump with sand filter) to pump the seawater directly to the membrane distillation installation is on the right corner of the dock. The Electrolyzer has produced the expected amount of hydrogen on the water produced by the membrane distillation. This water is produced using the residual heat given off by the electrolyser.

An economic evaluation has shown that additional benefits can be gained from the amount of water produced with the residual heat. About a third of the water produced is used for hydrogen production. Two-thirds of the water produced is available for other purposes. This is pure water and is interesting in areas/periods with water scarcity, offshore, and for drinking water or industrial applications.

Green hydrogen

“Green” hydrogen is an important part of the transition to a society free of fossil fuels. It can be used, among other things, as a fuel and as a chemical raw material for various industrial processes. In addition, it is an important solution for buffering sustainable energy at peak times of both wind and solar energy. Solar and wind energy are often free at peak times, or customers are even paid for purchase to prevent network overloading.

At such moments, offshore wind energy can be converted into hydrogen. An additional advantage of producing hydrogen at sea is that the existing gas pipeline infrastructure can transport hydrogen to land. This is considerably cheaper than installing additional electricity lines to bring the wind energy ashore.

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