Waves, wind and hydrogen

 "Off Helgoland, a consortium wants to produce hydrogen in the middle of the sea using wind power. Is that the future?

Lots of wind, lots of space and no neighbors who feel disturbed - the sea offers the best conditions for generating wind power. One disadvantage of power plants on the high seas is that the electrical energy generated can only be transported to the mainland with great effort. In addition to high-voltage direct current cables, this also requires expensive transformer and converter stations in the offshore wind farms. 

 

An association of companies, research institutes and public institutions called Aqua Ventus now wants to use the energy directly on site: Electrolysers are to use the wind power to produce green hydrogen in the middle of the sea, which is then brought to land through pipelines. "Pipelines have the advantage that they can transmit around five times more energy than with a cable," says Sebastian Föllner, engineer in the coordination office of Aqua Ventus.

 

The partners, including RWE, Eon, Siemens Energy, Linde and Shell, initially want to install two wind turbines off Heligoland in 2025, with platforms for the electrolysers mounted on their towers. 

 

"The systems are encapsulated in containers so that they are protected from water and the salty air," explains Föllner. According to the plans, there will also be space on the area for desalination plants that extract the fresh water required for electrolysis from the seawater. In addition, compressors are to be installed there that compress the hydrogen produced so that it can be transported away via a pipeline that has yet to be laid.

 

Hydrogen production at sea is usually cheaper than production on land with offshore wind power

Assuming the success of this pilot project, the first commercial offshore hydrogen park with an output of 290 megawatts will then be built in the German Bight in 2028. By the middle of the next decade, Aqua Ventus believes an installed capacity of ten gigawatts is feasible. One million tons of green hydrogen could then be produced there annually. This could almost halve the CO₂ emissions of the German steel industry.

Because of the less complex pipeline transport, the production of hydrogen at sea is more cost-effective than the production on land with offshore wind power, as long as the hydrogen is not consumed directly at the electrolyser. This is shown by a short study commissioned by the Federal Maritime and Hydrographic Agency. The more powerful the wind farms, the greater the cost difference. The deep-sea electrolysis also performs better the further the wind farms are from the coast. A big advantage with a view to locations that are so far out to sea that a wind farm with a connection to the power grid would not be profitable - for example in the so-called Entenschnabel, an area in the North Sea up to 400 kilometers from the German coast, that alone the Federal Republic may use economically. 

 

Wind farms closer to the mainland could then generate electricity for the grid, plants further away could generate hydrogen.

 

However, there is still a lack of the necessary legal framework for large-scale offshore electrolysis, for example with regard to the designation of areas or the approval process. And technically there are also many unanswered questions - for example, how electrolysers cope when they are supplied with energy directly from the wind turbine. "If an electrolyser is connected to the power grid, it works under constant conditions. If you connect it to a wind turbine, its operation becomes much more dynamic because the electricity generated fluctuates," explains Andreas Reuter, head of the Fraunhofer Institute for Wind Energy Systems (IWES). The quality of the offshore electricity does not necessarily correspond to that in the grid. "How all of this affects the performance and aging of the electrolysers is still unknown."

What might not work in Germany could be a future concept for other regions

The Fraunhofer researchers are now investigating these and many other questions together with partners in the H2Mare project. There, the scientists are also concerned with the processing of the hydrogen produced into synthetic fuels at sea and with salt water electrolysis. However, Reuter warns against expecting quick results. "The concept of offshore electrolysis is far from ready for the market. We are still doing basic research here," says the scientist.

The Offshore Foundation also prefers to keep the ball low. In the opinion of the managing director Karina Würtz, it is not  yet possible to conclusively assess whether it is better to use offshore wind power to produce hydrogen at sea or on land. "We therefore advocate gaining experience with both concepts - and trying out different variants, for example with regard to the transport of hydrogen on land."

This is also an advantage with a view to projects in other regions of the world. "What may turn out to be unsuitable for Germany could be very useful elsewhere," explains Würtz. After all, the National Hydrogen Strategy adopted by the former federal government in 2020 provides that the majority of demand will be covered by imports. When building the required production capacities abroad, the offshore industry could then benefit from the experience it has gained off the domestic coast."