Storing hydrogen - Why?
Being able to store hydrogen in large quantities means making renewable energy sources flexibly available. This is essential for a decarbonised energy system in the future and the development of a hydrogen industry in Germany. We have been using large-scale storage facilities for the safe storage of natural gas for decades. We are testing underground hydrogen storage in caverns with the HPC Krummhörn project.
The Background
The storage of hydrogen in salt caverns has so far only been used sporadically in the USA and the UK. Especially for operational use with cyclical injection and withdrawal, there is not enough experience in Germany. The manufacturers do not have sufficient specifications regarding material compatibility and certifications for operation with hydrogen.
This is why we test geological conditions and all plant components for their compatibility with hydrogen in a specially constructed pilot cavern.
The experience gained here will then form the basis for larger-scale projects and the foundation for the construction of further, then commercial, hydrogen caverns at other locations.
Project description
- Commissioning of the demonstration plant in 2024
- Storage volume of up to 500,000 Nm³ hydrogen - corresponds to 1,8 GWh
- Testing the operation and technology of 100% H2 storage in real environment
- Understanding of the approval procedures and requirements
- Investigation of materials, underground and above-ground installations, and the functionality of individual components in H2 storage operation.
- Development of a storage solution for renewable hydrogen on a commercial scale
Process stages
Evaluate the status of the borehole and perform a two-stage gas tightness test
For the construction of the H2 pilot cavern, we are using the existing storage well K6. Before starting work on the cavern site, we examine the existing components of the well in various material tests to determine their suitability for hydrogen storage operation. First, we use a workover rig to restore access to the open hole and create a defined continuous borehole diameter in the uncased borehole area that is part of the test area. In addition, we subject the well to a two-stage gas tightness test using the test media nitrogen and hydrogen.
Creating a cavern by leaching
During the brine phase, we will create a pilot cavern with a geometric void volume of approximately 3,000 m³ in the lower section of the well. This configuration allows for a possible later re-solving to enlarge the cavern in order to be able to use the cavern commercially for hydrogen storage after the pilot phase. For the brine-out phase, the necessary brine-technical installations will be installed and the cavern will be connected to the brine station via the field pipeline system. In order to specifically develop the cavern shape, we use nitrogen as blanket medium.
Hydrogen leakage test and installation of a hydrogen storage completion
After the pilot cavern has been built, the solar installations will be removed and the cavern will be subjected to a new leak test with hydrogen as a medium. The test pressure corresponds to the later storage operating pressure. Afterwards, we convert the cavern for hydrogen operation. In this context, we install, among other things, a hydrogen production pipe tour with special underground components and a hydrogen wellhead. On the surface, we connect the cavern via the field pipeline system to the storage station, where the hydrogen storage components are installed.
Initial hydrogen filling and subsequent pilot storage
To evaluate the various planned tests, the operating conditions and the hydrogen suitability of the components, we install appropriate measuring equipment. After commissioning all components, we then fill the cavern with hydrogen for the first time. The brine that is still in the cavern at this point is displaced by the hydrogen and brought to the surface via a brine drainage line. After complete filling, the brine drainage line is removed from the cavern under pressure using a so-called snubbing system. The operating phase of the hydrogen pilot cavern then begins.
Project Milestones
Funding letter
After a feasibility study, Lower Saxony’s Environment Minister Olaf Lies granted €2.375M on July 25, 2022 for Uniper’s hydrogen pilot at Krummhörn, calling it ‘a key part of Germany’s energy transition.’
Mechanical integrity test
From April to June 2023 an initial gas tightness test was successfully carried out on the existing borehole using hydrogen and nitrogen
Creating a cavern through leaching
Massive underground salt deposits were leached for 8 weeks (January - March 2024) , creating a 3,000 m³ cavern (30 m high, 16 m diameter). It can store nearly 500,000 Nm³ of hydrogen—about 1.8 GWh.
Installation of a completion
From April to May 2024, a workover took place in which the brine pipes were removed and the hydrogen-compatible completion was installed.
Opening
Olaf Lies, Lower Saxony's Minister for Economic Affairs, alongside our CEO Michael Lewis and other distinguished guests, inaugurated the facility in August 2024.
Leak test
October 2024: After installing hydrogen-compatible components, a second gas tightness test was successfully carried out with hydrogen.
Converting of field pipeline
From January 2025 to January 2026 a field pipeline previously used for transporting natural gas was extensively analysed, examined, repurposed and certified for hydrogen use.
Completion of the surface facilities
December 2025: On the premises of the former natural gas storage facility, all required surface facilities for hydrogen storage and withdrawal are complete – we are ready for test operation!
