KONGSTEIN has developed a compressed gaseous H₂ carrier vessel for the transport and direct shuttling of H₂ from an offshore wind farm to a dedicated offloading port. The work was carried out as part of the two-year OffsH2ore project funded by the Federal Ministry of Economic Affairs and Climate Action (BMWK).

The aim of the overall project was to develop a technically and economically optimized design for an integrated offshore H₂ production plant using proton exchange membrane (PEM) electrolysis, including a concept for transport of compressed gaseous H₂ (CGH2) to shore. The present results can serve as a blueprint and starting point for the development of pilot and large-scale projects and the elaboration of corresponding regulations. The offshore H₂ production on the scale of 500 MW as well as the transport of compressed gaseous H₂ has not yet been realized. With the concept presented by the consortium, a rapid and large-scale implementation has become realistic.

The concept is based on an offshore wind farm that is directly connected to a 500-MW electrolysis platform that produces up to 50,000 tpy of green H₂. The system has a scalable, modular design that can be easily adapted to different H₂ production capacities. The fresh water for the PEM electrolyzer is provided by desalination of seawater, using the waste heat from the electrolysis. The H₂ produced is purified and dried, compressed to up to 500 bar and transferred to a transport vessel that delivers 400 tons of H₂ per shipment from the offshore platform to shore. This concept is independent of H₂ transport pipelines and offers flexibility in the choice of location.

In addition to KONGSTEIN GmbH, the consortium included PNE AG, an international project developer for renewable energy plants as project coordinator; SILICA Verfahrenstechnik GmbH, a process engineering and plant construction company; Fraunhofer ISE, the largest solar research institute in Europe and active in H₂ systems; and Wystrach GmbH, a supplier of high-pressure storage systems for H₂. The OffsH2ore project thus brought together an experienced and complementary consortium of industrial partners and scientists from the entire value chain.

“Green H₂ produced sustainably from renewable energies will become an important pillar for the decarbonization of our energy systems. For countries like Germany, where the large-scale production of green H₂ is a challenge due to land-use competition, for example, H₂ production at sea with the help of offshore wind energy is an additional option” explains Marius Holst, Fraunhofer ISE coordinator in charge of the work packages. “H₂ production offshore simultaneously offers high full-load hours and the opportunity to cover the entire value chain on a national level, while at the same time decoupling offshore wind and grid expansion,” Holst continued.

The work packages of KONGSTEIN comprised the implementation of an integrated maritime H₂ supply chain, including H₂ loading arrangement, vessel design and transport concept from offshore site to shore.

“Vessel based transport of CGH2 is an alternative if pipeline-based transport is not possible and can be adopted for offshore-to-port and port-to-port logistics. It will allow us to enter markets much earlier and to react faster as well as more flexible on the energy supply chain. Direct shuttling of CGH2 allows us to transport the H₂ directly without the use of expensive intermediate storage systems. The transport of pure H₂ gives us advantages in terms of energy efficiency and reduces the additional conversion systems off- and onshore compared to derivatives,” explained Lukas Niebergall, KONGSTEIN’s project lead of the work packages.