Underground storage facilities for hydrogen as central buffers

The use of hydrogen will be an important factor in the sustainable energy supply of Germany's energy-intensive industries. To ensure that sufficient hydrogen is available at all times in the future, the expansion of large underground storage facilities and the corresponding pipeline infrastructure is crucially important. ‘“Underground storage systems cannot be implemented overnight. Politicians must therefore pave the way now for investment security, while storage operators are already tackling the technical challenges in pilot projects,’” demands Alexander Holle, Head of HydroHub at the TÜV NORD GROUP.

Hydrogen will play an important role in ensuring a resilient and climate-neutral energy supply in Germany, especially for energy-intensive industrial sectors that cannot be electrified, or at least not economically. ‘Even though the market ramp-up is not progressing as quickly as expected a few years ago, hydrogen is still the best option for a number of sectors,’ emphasises Alexander Holle. ‘The Federal Government of Germany has recently introduced some important measures with the drafts for the Hydrogen Acceleration Act and the Geothermal Energy Acceleration Act. However, in order to have sufficient hydrogen available in good time, the preconditions for the expansion of hydrogen storage facilities must now be created.’

Storage facilities compensate for fluctuations

Underground storage facilities can serve several purposes in the energy system of the future:

•  As fluctuation storage: Stored hydrogen can be converted back into electricity at short notice to compensate for fluctuations in the power grid.
   
• As seasonal energy storage: Increased energy requirements during periods of low sunlight and in winter can be stored over the summer in the form of hydrogen.
   
• As an energy reserve: As a strategic energy reserve, large hydrogen storage facilities can secure supply against uncertainties caused by external influences on energy imports and price fluctuations.
   
• As a buffer: A flexible buffer can ensure the even utilisation of other infrastructure such as import terminals or pipelines.

While short-term fluctuations in the grid can also be balanced by pressure changes via the pipeline system or other storage methods such as battery storage, all other applications require both long-term and large-volume storage to achieve the desired effect. Underground hydrogen storage facilities are particularly suitable for these purposes, as they can store large amounts of energy over long periods of time, which can then be used for electricity and heat generation as well as for other industrial processes.

Salt caverns particularly suitable

Salt caverns are particularly suitable from a technical point of view, as they are chemically inert and geologically stable over the long term. Existing caverns can be converted and new ones can be created. ‘Northern Germany has very large underground salt deposits, a unique feature in Europe, making this region ideal for the construction of hydrogen storage facilities,’ explains Alexander Holle.

Industrial demand determines necessary capacity

How much storage capacity will be needed in the future depends primarily on hydrogen consumption by large consumers such as energy production and industry. The long-term scenarios of the Federal Ministry for Economic Affairs and Energy predict a sharp increase here: by 2035, demand is expected to be only 17 TWh per year – but by 2040, it will already be 55 TWh. The reason for this is the introduction of hydrogen technologies in power plants and large-scale industries during this period. By 2045, demand is expected to reach up to 80 TWh per year.

Uncertain market situation complicates investment decisions

Converting power plants and large-scale industries to hydrogen requires storage facilities to be in place at that time. This is the only way to ensure that hydrogen is reliably available throughout the year. ‘However, we are currently seeing a great deal of uncertainty in the market, as it is unclear how the energy transition and the transformation of industry will develop at the European level. For many large-volume storage projects, therefore, no final investment decision has yet been made,’ says Alexander Holle. ‘However, repurposing or creating new caverns takes an enormous amount of time, so investment decisions will have to be made in 2026 or 2027 in order to achieve the necessary capacities.’ Repurposing existing caverns takes around four to six years, while new construction lasts around 10 to 12 years. The main challenge in repurposing caverns is adapting the above-ground plant components to hydrogen, as well as the approval processes. When constructing new caverns, the time required for the so-called soling of the caverns in the salt dome, in which water is injected to dissolve the salt and create a cavity, significantly extends the time frame.

Technical challenges still unresolved

Many technical questions also remain to be answered, for example regarding gas purification, material suitability and fracture resistance under increasing pressure. Pilot and demonstration projects are currently addressing the outstanding technical issues. The standardisation of materials and processes resulting from these projects could significantly simplify the construction of storage facilities. Support for these projects is therefore essential for the ramp-up.

‘The federal government must now create clear framework conditions for the expansion of the storage infrastructure and formulate a target vision for its role in the European energy system. In addition, investment incentives should be created for the conversion and new construction of caverns,’ says hydrogen expert Alexander Holle.

Companies in the TÜV NORD GROUP support the expansion of underground hydrogen storage facilities with their expertise in geotechnical issues and technical areas.