The first offshore green hydrogen pilot project in Europe, Sealhyfe, has been towed back to Quai des Frégates in Saint-Nazaire, France after six months of producing H2 at sea.

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The 1MW PEM electrolyser, supplied by Plug, was initially launched in September last year with eight months of testing at quayside, before being towed to the SEM-REV offshore testing hub in May.

This hub was also the site of a Floatgen floating offshore wind turbine, engineered and operated by BW Ideol, which provided Sealhyfe with power.

The project’s developer Lhyfe announced in June that it had successfully produced the first volumes of hydrogen from the pilot, which has a nameplate capacity of 400kg per day.

Now that Sealhyfe has been towed back to dock, Lhyfe will compare operational data between the tests at quayside and at sea.

The developer will also analyse offshore-specific information, including reliability of H2 production in an isolated environment, how the platform’s motion responded to environmental stressors such as waves, and how well the electrolyser’s hydrogen production software and algorithms worked.

Lhyfe expects to build on its results with its next offshore H2 project, HOPE, which will have 10MW of electrolysis capacity capable of producing four tonnes of hydrogen a day for export to shore via pipeline.

Proponents of H2 production at sea argue that offshore wind is the only way to produce vast volumes of the zero-carbon gas at scale in Europe, given insufficient available land for massive wind and solar projects, with some analysts modelling cheaper costs for hydrogen produced at sea and transported via pipeline as opposed to building expensive transmission cables to an electrolyser onshore.

HOPE has already received a €20m ($21.8m) grant from the European Commission via the Clean Hydrogen Partnership programme.

“We’re already benefiting from the experience we’ve gained and putting it to good use in our next steps towards offshore production,” said Matthieu Guesné, founder and CEO of Lhyfe.

“The production of hydrogen at sea is now a reality, and the countdown to scale up has begun!”