Delivering Green Hydrogen from Offshore Wind to shore: A case-study by Martin Rahtge and Michael Berges, ONP Management GmbH and Partner AquaConsult

To meet this human need, innovative technologies need to be developed faster and faster and made available for public use as early as possible. These requirements were a driving force for ONP Management and three partner companies, Heinrich Rönner Group, HF Offshore and Hy 5 Management, to establish a project company with the aim to deliver green hydrogen, produced from offshore wind, as early as 2031. Securing an offshore-site at one of the SEN-1 areas in the German EEZ (Exclusive Economic Zone), soon to be tendered by the German government, is the next step in the development.

Therefore, it does not come as a surprise that ONP Management is also part of AquaConsult. As the “One-Stop-Shop for developing green hydrogen projects from Offshore Wind” this network comprises all the expertise and know-how to support and deliver such a project from conceptualization, via offtake-approach, permitting, financing and insurance, engineering and design to contracting, execution, commissioning and operation-concepts.

Electrolysis from Offshore Wind

The use of wind energy as a power source for water electrolysis is a natural choice, as is the use of offshore wind. Slowly but surely, offshore wind farms are being sited far from shore, resulting in higher losses and costs in transmitting the electricity from point of generation to consumers ashore. As electrolysis is a high energy consumer, it is natural to think about solutions to produce green hydrogen in offshore conditions. This approach presents several advantages that make it a compelling option for meeting the increasing demand for clean energy.

Producing hydrogen in an offshore context from renewable sources offers a realistic pathway towards achieving sustainable energy goals by leveraging the abundant renewable energy resources, spatial flexibility, and proximity to end-users that offshore environments provide. By harnessing the power of offshore wind and other renewable sources to produce clean hydrogen, offshore hydrogen production has the potential to play a significant role in the transition to a low-carbon energy future.

Case Study: NORTHSEA HYDROGEN Project – ship-based transport of green hydrogen

The NORTHSEA HYDROGEN Project is an innovative venture aimed at producing green hydrogen at sea, using offshore wind as renewable energy source. The offshore wind farm, located far out at sea, generates electricity that powers electrolysis. The electrolysis-stacks are located on a platform at the edge of the offshore wind farm, enabling a highly cost-effective centralized production of hydrogen. Being produced only via renewable energy, this hydrogen is referred to as Green Hydrogen and can be stored and transported for use in various sectors such as transportation, industry, and power generation. The project represents a significant step towards sustainable and clean energy solutions, contributing to the global efforts against climate change.

Hydrogen-Flowchart (Source: NORTHSEA HYDROGEN)

Vessel Transport - Logistics Concept

The transport concept must ensure that the hydrogen produced is transported as efficiently as possible. The underlying sprinter approach for the NORTHSEA HYDROGEN Project envisions transportation by ship. The connection to a yet to be built pipeline network (i.e., AquaDuctus) is also considered.

The vessel transport concept consists of two compressed-hydrogen carriers and a double offshore loading system.

Vessel transport cycle (Source: NORTHSEA HYDROGEN)

To assure a continuous loading process, at least one vessel is connected to the offshore loading system at any time. After loading, the vessel will return to port to discharge the hydrogen and sail back to the offshore site. To guarantee a continuous loading process the empty vessel needs to be connected to the offshore loading system and be ready for loading before the other vessel is finished with loading.

At our project, a gaseous hydrogen carrier with large-volume tanks, like the Provaris H2Neo, is being considered. With a tank capacity of 26,000 m³ the vessel can carry approx. 430 t of gaseous hydrogen:

Gaseous hydrogen carrier (Source:Provaris Energy)

Loading System

A commonly used technology in the oil-and-gas industry is the Double Anchor Loading system (SAL). It is anchored into the seabed and consists of a mooring turret, a pipeline end manifold and an in-line swivel.

Double Anchor Loading system (Source: APL | NOV)

Because of the flexible hose connection, the vessel can rotate around the loading system, depending on weather, wave, and wind direction, without any influence on the loading process. The maximum weather limit of the system to connect the pipeline to the vessel is a significant wave height of up to 4.5 m. The loading process and disconnecting allows a significant wave height of up to 7 m.

For the connection between vessel and pipeline, the vessel needs to be equipped with a Bow Loading System (BLS). This system can lift and connect the loading manifold to the vessel and moor the vessel to the SAL system.

Bow Loading System (Source: APL | NOV)

Status of development and outlook

Since 2021, the parent companies have been discussing the conceptual design, gathering a directional network, and discussing the feasibility of the project with policy makers. In 2022, with the official establishment of the company, the early project development started, including the approach of potential investors and prospective off-takers.

The project team is currently maturing its concept with a focus on system integration and maximizing efficiency. Simulations are being conducted and benchmarking with similar solutions under development is executed. The project company is also participating in the public discourse on the German vision of offshore green hydrogen production, and creating awareness of the viable potential solution that this project could bring to the market.

It is expected that these efforts will culminate in one of the SEN-1 sea areas to be secured by NORTHSEA HYDROGEN in 2024/25. With this happening, the project will undergo detailed development between 2025 and 2027, with the permitting process taking place, as well as the negotiation and signing of supply agreements, culminating in financial closure. As ONP is part of the AquaConsult network, most aspects of the project development can be covered “in-house” by this unique One-Stop-Shop for Offshore-Electrolysis-Projects.

After the Final Investment Decision, between 2028 and 2030, the fabrication, installation and commissioning of the platform and equipment will take place, enabling the 30-year operational period to start as early as 2031.

For more information visit: or North H2 Sea – Offshore Farm (

About the Authors:

Acting as CEO with long-lasting experience in marine infrastructure and developing a German EPCI-contractor for offshore wind, Martin Rahtge, together with partners, founded ONP Management GmbH back in 2014. Since then, ONP has been supporting Offshore Wind and other renewable energy projects around the globe with a dedication to shaping and realizing the energy transition.

Michael Berges has been active in the Offshore Wind Business since 2011, executing Project Management for T&I-Contractors, Developers and O&M-Providers in Europe, Asia and the Americas. At ONP he is also responsible for Quality and Risk-Management, as well as developing the Business Sector of Green Hydrogen.

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