H2Mare researches offshore technologies
Offshore wind power stations generate significantly more electricity and more regularly than their onshore counterparts. In the lead project (Leitprojekt) H2Mare, scientists are working to exploit this potential – and to produce green hydrogen and derivative products directly at sea in the future. Current progress is being made, among other things, in the coupling of wind turbines and electrolyzers.
At sea, strong and constantly blowing winds ensure the best conditions for generating renewable electricity. If this could be used directly for the production of green hydrogen, it could significantly reduce the costs compared to hydrogen production on land. Because this way not only are the costs for an intricate grid connection unnecessary but also the energy losses as a result of the additional conversion processes.
Partners from research and industry are working in the hydrogen project H2Mare on directly coupling a water electrolyzer with a wind power station and thus making available innovative technologies to produce green hydrogen offshore. In order for this to be successful, both the electrolyzer and the wind turbine must be adapted and, if possible, directly electrically connected to each other. The fluctuating power supply as the basis for the entire subsequent conversion process, including water treatment and the regulated coordination of the system, is one of the biggest challenges for the development engineers. But that is exactly what is now happening for the first time in a megawatt-scale test system.
The hydrogen lead project H2Mare
In Leitprojekt H2Mare, the offshore production of green hydrogen and other power-to-X products is being researched. Around 30 project partners from research, industry and society are working closely together for this. Next to H2Giga (series production of electrolyzers) and TransHyDE (transport and storage infrastructure), H2Mare is one of three hydrogen lead projects of the German ministry for education and research. As part of the national hydrogen strategy, the lead projects will contribute the expansion goal of ten gigawatts of electrolysis capacity by 2030.
For the first time, wind turbines are directly connected to electrolyzers
In order to practically test the direct coupling and its consequences, the H2Mare project OffgridWind in the Danish city of Floe has built a corresponding test system – for now on land. There, the H2Mare project partner Siemens Gamesa has electrically connected two electrolyzers for H2 production to the wind turbine, the way this could later happen on the high seas. With this setup, the project team can also test the switching between two systems and thus optimal operational management.
With this structure, the effects on the control system can be identified, further assessed and adjusted if necessary, as this will also be one of the critical aspects at sea. In the coming months, H2Mare will now investigate how the fluctuating electricity production affects the functioning of the system.
What a wind power station with integrated hydrogen production would look like H2Mare has likewise already analyzed: In the future, all necessary systems could be housed on a platform directly next to an offshore wind turbine.
3D model of the H2Mare wind power platform for offshore hydrogen production as well as the container systems with electrolysis and water treatment units
Source: Leitprojekt H2Mare
Test facility for seawater desalination
Seawater desalination with desalination plant in Bremerhaven, Germany
Source: Kevin Schalk, Fraunhofer IWES, Leitprojekt H2Mare
These systems also include a seawater desalination unit for electrolysis. A corresponding test system from H2Mare project partner Fraunhofer IWES in Bremerhaven has been put into operation. It filters seawater, treats it, heats it and thus produces ultra-pure water. Different from other test projects, H2Mare is actually directly working with water from the North Sea in its tests. Later, waste heat from H2 production will heat the water.
Because the treated seawater is only available at fluctuating temperatures, experts in the H2Mare project H2Wind are currently testing the system with different operating temperatures. Initial results show that water temperature fluctuations affect the start-up behavior and energy requirements of the desalination system, but only insignificantly influence the production volume of ultrapure water.
Demonstration of a power-to-X process chain at sea
But it is not just hydrogen production that is being examined in the project. Subsequent products also play a role. In the H2Mare project PtX-Wind, the production of further power-to-X products at sea, for example methane, methanol, Fischer-Tropsch products and ammonia, is being tested. For this, in addition to water, CO2 and nitrogen are needed. These should, among other things, be obtained directly on site from the air (direct air capture) or the sea.
Power-to-X containerized system for offshore use, Source: KIT
The developed concepts for all synthetic products PtX-Wind wants to test first on land. For the first demonstration of a power-to-X process chain – consisting of co-electrolysis and the synthesis of fuels – scientists at EnergyLab of the Karlsruhe Institut für Technologie (KIT) have built a power-to-liquid (PtL) containerized system. In this, fuels are produced from hydrogen and CO2 using Fischer-Tropsch synthesis. In 2025, the entire PtL process chain, coupled with a co-electrolysis from the German aerospace center (DLR) will be demonstrated on a floating platform at sea. In addition to the co-electrolysis, this will house a direct air capture system, PtL synthesis and wastewater treatment in containerized systems and produce Fischer-Tropsch products that can later be used as sustainable fuels such as diesel or kerosene.
H2Mare basic idea: Offshore wind farm with special wind turbines, each of which has an electrolyzer
Source: Projektträger Jülich on behalf of the BMBF
The results of the research activities in H2Mare will be presented to the public at the project end conference in autumn 2025.
Author: Christian Hiemisch, Fraunhofer IWES, Leuna
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