Hydrogen production in offshore wind parks A practicable model?

Using electrolysers in combination with renewable power plants to produce green hydrogen is a significant element in import-independent provision of this climate-friendly energy carrier.

It represents a major technical challenge because, for example, there needs to be as near as possible constant availability of renewable energy, since electrolysers run most efficiently when they can be operated without interruption and with constant output. This can put wind and solar, which are somewhat volatile renewable energy carriers, at a disadvantage. One advantage of offshore wind parks becomes clear in this context, because with the wind blowing constantly over the high seas, wind power plants attain full capacity hours that are sometimes twice as high as those of land-based sites.

On 27 January 2025, EEHH ran a forum session on the topic of offshore wind and hydrogen production. A range of concepts for producing hydrogen in combination with offshore wind parks were presented and discussed during the event. The first lecture, given by Mr Berges (NorthH2 Projektgesellschaft mbH) on the Northsea Hydrogen project, explained how a demonstrator platform was set up within the existing wind park Alpha Ventus. To do this, the existing structures are being repurposed and the components for electrolysis installed on one of the wind park’s existing platforms (in addition to the electrolyser itself, these include systems such as seawater desalination and compression). Underneath the platform, an underwater cooling system and H2 storage system is being constructed. The operation is intended to gather experience with the use of the components under offshore conditions and for maintenance, in order to enable future hydrogen production plants to be installed further away from the coast with the electrolyser running as fully automatically as is possible.

The second lecture, by Olaf Klose (OneSubsea), was about technical applications that can be transferred from the experiences of the oil and gas industry to the offshore wind/hydrogen field. For example, elements needed for wind parks and electrolysis could be relocated to the seabed. This applies to applications such as cooling of electrolysers, which is many times easier if the cooling fins are 30 metres under sea level with cold currents washing around them. It also includes AC converters – which would enable all components of the previous AC/DC converters to be moved underwater except for the DC components, which would remain above sea level on converter platforms. Many underwater technologies have already been used in offshore oil and gas extraction for many decades, and could contribute to driving forward a rapid transformation in electrolysis, while also offering potentials for optimising “pure” offshore wind parks.

A fundamental distinction can be made between hydrogen production on-site in offshore wind parks and hydrogen production on land, in which the electricity is transferred by undersea cable. In a nutshell, the findings of the event were as follows:

Where offshore wind parks are more than 120–150 km from land, offshore electrolysis is a rational alternative; parks that are closer should generate electricity (potentially with a view to electrolysis on land). The costs for a pipeline are up to 80 percent lower than costs for connecting offshore wind parks via undersea cable. For many components, experience from the oil and gas industry can be relevant. There is a regulatory framework in place, but still a lack of transparency. Initial demonstration projects, such as the Northsea Hydrogen project and H2 Mare are being launched.

These show that one decisive advantage of hydrogen production in offshore wind parks, aside from the higher number of peak-load hours, is the lower costs for pipeline connection in comparison with HVDC undersea cables, especially where the distance from the coast is greater. Additional scaling effects can be expected here when multiple H2 offshore wind parks are connected. Nevertheless, hydrogen production on the high seas entails a whole series of additional challenges. For one thing, the highly sensitive components for the electrolysis process (electrolyser, water treatment etc.) must be able to withstand the harsh conditions at sea, for example in terms of corrosion. Moreover, risks to critical infrastructure, especially in the Baltic region, have increased recently and will probably play a greater role in the future.

As an alternative to hydrogen production in wind parks, there is a possibility that electricity generated offshore can be used for hydrogen production once it reaches land. Initial pilot projects on this concept have already been realised. For example in Vattenfall’s Zeevonk project in the Netherlands. The plan here is to combine a 2 GW offshore wind park with a 1 GW electrolysis park on land. The low costs for connection to the land-based power grid are achievable here because the park is close to the coast. The primary goal is sale of electricity. So hydrogen is more of a “byproduct”. The plant is planned to be commissioned by 2029.

When the North German Hydrogen Strategy (NWS) was developed, a target was set for 1 GW offshore electrolysis output by 2030. In the 2025 site development plan published on 30 January 2025, the Federal Maritime and Hydrographic Agency (BSH) designated an area of the German North Sea and Baltic of up to 100 km2 for “other energy generation” (SEN-1). In the North Sea, this area is within the German EEZ. In the Baltic, no areas within the German EEZ have so far been designated for other energy generation.