Cyclic testing of renewable hydrogen storage in a small salt cavern

Topic description

Specific Challenge:

The combination of variable renewable energy, electrolysers and geological stores can provide a means for capturing and holding renewable energy at scale. A fully renewable system in EU will require very large volumes of hydrogen storage and the ability to transfer hydrogen in/out of the stores at various rates across the day/year, with associated variations in pressure level. Considering this challenge, it is important to understand whether geological stores can be used in a time-varying cyclic manner to accept high charge and discharge rates, together with any impacts on the gas transportation system or downstream applications.

Hydrogen storage in salt caverns is well established, but salt caverns have not been subjected to time-varying rates of hydrogen input and output to reflect the variable profiles of renewable power and hydrogen/energy demand (as will be required if they are to act as a dynamic buffering option to enable sector coupling and a more resilient energy system).

The main objective of this topic is to examine the feasibility of cycling a salt cavern, fed by an electrolyser that follows an intermittent renewable power profile while hydrogen is discharged from the cavern to cover a specific hydrogen demand. This should provide a better understanding of how to integrate and balance intermittent renewables in the EU energy system. The results should offer sufficient learnings for decisions on scaling-up large underground storage of renewable hydrogen.

A suitable salt cavern should be identified for undertaking a pilot scale demonstration involving a MW scale electrolyser and essential infrastructure equipment. The size of the cavern, the electrolyser and the profile of hydrogen demand should be such that over the duration of the project the cavern will be cycled a few hundred times, e.g. at least daily cycling.

The transient performance of the system should be assessed in a temporally precise manner when it is subjected to a variety of relevant renewable input and hydrogen/energy demand profiles. The electrolyser response times should be compliant with providing grid services in future balancing markets, as may be required to achieve a fully renewable energy system. Through an extensive test and demonstration programme, the project should establish the technical (geological, geochemical, microbiological) and economic capabilities and limitations of salt caverns to act like a ‘lung’ for the energy system (absorbing variable renewable energy and discharging hydrogen as required to match supply and demand across very different periods and response times).

For this demonstration pilot, preferably hydrogen produced directly from renewable sources should be used for providing the working volume, while the cushion gas may come from other sources. “CertifHy Green H2“ guarantees of origin should be used through the CertifHy platform [61].

The application model to be considered in the project should be parameterised (e.g. the fuel utilization factor with respect to the overall amount of pressurized fuel stored in the cavern), in order to identify positive business cases and the highest replication potential of the pilot case in caverns of various size. To achieve a deep understanding of how the project could be scaled up and applied across the EU energy system, it should study a real case of sector coupling by considering one or a combination of the following options: hydrogen consumption by the industrial sector, hydrogen mobility, injection into the gas grid (of hydrogen or synthetic methane) and stationary power generation.

It is expected that the replicability and scalability of the project would be fundamental to facilitating further deployments of renewable hydrogen storage underground in salt caverns. The project should therefore liaise with relevant bodies and other projects to share and disseminate learnings including RCS issues.

TRL at start of the project: 5 and TRL at the end of the project: 7.

Any safety-related event that may occur during execution of the project shall be reported to the European Commission's Joint Research Centre (JRC) dedicated mailbox JRC-PTT-H2SAFETY@ec.europa.eu , which manages the European hydrogen safety reference database, HIAD and the Hydrogen Event and Lessons LEarNed database, HELLEN. A draft safety plan at project level should be provided in the proposal and further updated during project implementation (deliverable to be reviewed by the European Hydrogen Safety Panel (EHSP)).

The project consortium should involve geologists to undertake expert analyses for any structural, geochemical or other effects that the cycling of the cavern with hydrogen could lead to.

The maximum FCH 2 JU contribution that may be requested is EUR 5 million. This is an eligibility criterion – proposals requesting FCH 2 JU contribution above this amount will not be evaluated.

The grid connection, building and the electricity for the commissioning phase are within the scope of the topic. The electricity used during demonstration/business operation shall not be considered in the scope of the topic.

Expected duration: 3 years

[61] https://fch.europa.eu/page/certifhy-designing-first-eu-wide-green-hydrogen-guarantee-origin-new-hydrogen-market

The project should:

• Demonstrate the cyclic operation of a salt cavern when subjected to hydrogen input variations that respect typical variations in renewable power generation and energy demand (e.g. hydrogen consumption by industry, hydrogen mobility, heat or power generation), as well as the possible impact in the gas transportation system;
• Establish the technical feasibility of safe and effective underground storage of renewable hydrogen by considering the possible geological and environmental issues, and the operational, inspection and maintenance requirements (e.g. the range of pressure levels required, degradation, humidity levels, etc.);
• Evaluate the scalability of renewable hydrogen storage for large scale replication and propose the engineering of specific solutions;
• Clarify issues relating to hydrogen purity and composition after the injection/extraction processes, the geological and the environmental impacts, pressure level variations and the level of measurement/instrumentation required among other issues;
• Aim to reach the 2020 H2 storage MAWP target of System CAPEX of €450/kg of H2 stored or an additional cost to H2 released of €1/kg.

The conditions related to this topic are provided in the chapter 3.3 of the FCH2 JU 2020 Annual Work Plan and in the General Annexes to the Horizon 2020 Work Programme 2018– 2020 which apply mutatis mutandis.