World’s first offshore hydrogen storage concept unveiled

Tractebel and partner companies have developed what they describe as the world’s first offshore infrastructure and processing facilities concept for the storage of hydrogen in offshore caverns.

The design study, unveiled by Tractebel Overdick GmbH, is said to outline an innovative solution for large-scale hydrogen storage on the high seas: a scalable offshore platform for the compression and storage of up to 1.2 million cubic metres of hydrogen.

Underground salt caverns will be used as storage and buffer for the hydrogen produced offshore, before the gas is transported via the pipeline network to the onshore grid and finally to consumers and customers, Tractebel said.

Green hydrogen from offshore wind energy is becoming an important component of the global energy transition, but current hydrogen production technologies will only make an effective contribution if production rates reach an industrial scale.

Enormous amounts of hydrogen (H2) from renewable sources will be required to supply future H2 energy demands and offshore sites are key to industrial-scale production, according to Tractebel.

In response, Tractebel developed an offshore hydrogen platform concept in 2019, followed by an optimised, scalable version the following year.

And now, the company is said to be breaking new ground with the design of the world’s first offshore infrastructure and processing facilities concept for the storage of hydrogen in offshore caverns.

This offshore platform complex consists of a wellhead platform for the operation of the caverns and a series of compression platforms that enable a staged increase in capacity.

If required, the plant can also be expanded in the future by additional modules. The study assumes a capacity equivalent to converting 2 GW of green offshore wind power into hydrogen. Extensions and individual adaptations are possible at any time.

Offshore compression and storage hubs such as these can further increase the flexibility of upcoming offshore hydrogen production. As the compression effort decreases at the wind farms’ electrolysis plants, so too shall the cost for offshore hydrogen production sites in general, Tractebel said.

”Centralised offshore hydrogen hubs also facilitate the integration of smaller-scale hydrogen production, which is to be expected within the scope of capacity expansions while re-powering offshore wind farms in the future. At the same time, they offer an economically viable option, as the export and compression of hydrogen produced offshore can be bundled. This significantly reduces the overall costs for future projects,” said Klaas Oltmann, Director Business Development at Tractebel Overdick GmbH.

The newly designed storage and compressor platforms process 400,000 Nm3/h of hydrogen, which is stored in underground salt caverns at a pressure of up to 180 bar. These storage facilities are said to buffer production peaks, optimise flow rates, and therefore enable a more economical design of the export pipeline.

An important contribution to the sustainability of large underground hydrogen storage facilities is that existing offshore infrastructures can directly use green hydrogen instead of other energy sources for their operations, contributing to the decarbonization of the entire offshore industry, according to Tractebel.

The North Sea is well suited for the solution due to its geological conditions and underground rock salt formations. Caverns are leached in these formations to create large storage volumes. The study assumes a total storage volume of up to 1.2 million cubic metres as a starting value for efficient peak coverage of offshore H2 production rates.

”This storage is also necessary in the long term, because it will be an essential building block for the success of the energy transition,” said Oltmann.

”Offshore caverns can buffer the renewable energy produced in the form of hydrogen and therefore balance out the divergence between energy production and demand profiles. In this case, the proposed size of the offshore storage facility is merely a starting point.”

In addition to Tractebel’s renewable energy and offshore experts, the engineering teams of DEEP.KBB GmbH and PSE Engineering GmbH were also involved in the design study, facilitating the concept’s complete development, from geology to processing equipment. This bundled know-how is the foundation for further optimizations of the offshore hydrogen hub and future H2 projects, Tractebel said.