Large-scale hydrogen storage has the potential to enable the integration of intermittent renewable energy sources in the gas grid and to support the industrial, mobility and other end-uses of green hydrogen. The aim of this flagship topic is to demonstrate the technical and economic feasibility of large-scale underground hydrogen storage to provide the flexibility to manage the imbalance between intermittent supply from renewables and variability in demand in an integrated electricity-hydrogen energy system, and to qualify all technologies and their components in an integrated storage system (TRL 8) by demonstrating large-scale hydrogen (energy) storage in underground salt caverns and/or gas fields and/or other geological structures, which are located in many places across EU.

As reflected in the EU’s Hydrogen Strategy and, more recently, in its REPowerEU Plan, hydrogen will play a key role as a decarbonised energy vector in future EU energy systems. As such, both supply (hydrogen production & hydrogen imports) and demand (hydrogen end-uses) will increase significantly in the coming decades. To balance the growing variations in supply and demand over time periods of days to seasons, hydrogen should efficiently be stored at large scale before it is transported and distributed from production/import locations to industrial, mobility and other end-uses. Large-scale hydrogen storage also has the potential to store energy when renewable electricity production is higher than the demand/capacity of the grid.

This flagship topic aims to demonstrate the economic and technical feasibility and qualify a complete storage system through testing of a large-scale underground hydrogen storage, its contribution to intermittent electricity management, security of supply, interface with hydrogen end-users as well as the economies of scale that can be realised in addition of the first steps accomplished with pilot EU funded projects (e.g Hypster^[1], Hystock^[2], HYSTORIES^[3], HYUSPRE^[4]. Project results are expected to contribute to all of the following expected outcomes:

• The achievement of the targets set out in the REPowerEU Plan and EU Hydrogen Strategy;
• Enabling higher integration of renewables within the overall energy system, in particular during an imbalance settlement of the electricity grid, through interfaces between underground hydrogen storage, electrolysers, the electric transmission grid, the hydrogen transmission infrastructures and direct feed end-users;

Project results are expected to contribute to the following objectives and KPIs of the Clean Hydrogen JU SRIA:

• For Salt Cavern:
  • CAPEX < 30 €/kgH₂ stored and salt cavern storage capacity above 3,000 tonnes H₂ (100%) - (based on the working mass of hydrogen stored, pure hydrogen considered);
  • CAPEX < 32 €/kgH₂ stored and salt cavern storage capacity between 1000 and 3,000 tonnes H₂ (100%) - (based on the working mass of hydrogen stored, pure hydrogen considered);
• For Depleted gas field:
  • CAPEX < 5 €/kgH₂ stored (capital costs include all necessary components to operate the storage system, including compression (to 120 bar max) and purification. The costs refer to the mass of hydrogen recovered from the storage).

Considering the source of electricity to be installed (wind and solar capacities), intermittency management of this electricity supply can limit the development of hydrogen production capacities. Based on prior supported projects which already demonstrate pure hydrogen underground storage, this flagship topic aims at integrating the innovation brought by large-scale underground storage to the whole value chain, to better understand how renewable hydrogen can be supplied continuously to industrial, mobility and other end-uses, while allowing production to be intermittent (daily or seasonally) due to renewable electricity supply. To this effect, large-scale underground storage will contribute to limiting the curtailment of renewable electricity and optimise the whole value chain to make energy more sustainable, more secure and more affordable for hydrogen consumers.

Proposals should address the following:

• Demonstrate how a smart large-scale underground hydrogen storage, with a potential storage capacity of at least 1,000 tonnes H₂ (for salt cavern: working mass of hydrogen stored, pure hydrogen considered/for depleted gas field or aquifers: mass of hydrogen recovered from the storage) integrated with renewable hydrogen source can contribute to higher integration of renewable electricity for hydrogen production (directly connected to power generation from renewable energy sources (RES);
• Demonstrate the transformation/conversion process of already existing underground storage from natural gas to hydrogen storage or the use of other geological structures for hydrogen storage;
• Define and analyse the interfaces of large-scale hydrogen underground storage with other elements like hydrogen producers, hydrogen consumers and/or a hydrogen dedicated distribution & transmission network;
• Analyse the sector coupling plus interaction of hydrogen underground storage in the future H2 network and overall future energy system network (including future energy scenarios) in terms of efficiency and possible technical operation modes of the hydrogen storage;
• Make recommendations about the technical and economic reproducibility of the process to other sites in EU;
• Improve overall energy and economic efficiency of the integrated system.

By the end of the project, the results should achieve a system complete and qualified (TRL 8). The proposed cyclic test program should include:

• End-to-end testing to qualify the performance, the integrity, the environmental impact and the safety of the underground storage, and the associated aboveground infrastructure;
• End-to-end testing to qualify the purity of the hydrogen recovered from the underground storage and the efficiency of the purification facilities (fluids & treatment process) required to deliver the hydrogen to the downstream parts of the value chain.
• For caverns:
  • At least a total number of 100 injection & withdrawal cycles of different pressure & volume variation. This cycling program should be representative of future operating conditions of an underground hydrogen storage in an assumed highly flexible hydrogen market. To that end, the cycling program should demonstrate the ability of underground storage to meet hourly temporal correlation;
  • Short and long-duration storage cycles (including superimposed cycles) with different net ramping rates, amplitudes, periodicities, and stand-by periods. (It is not expected to fill the cavern to 100% then empty it entirely for all 100 cycles).
• For depleted gas fields:
  • At least a complete storage cycle (injection phase followed by the withdrawal phase) that are representatives of the operating conditions of a future underground hydrogen storage in a depleted gas field in compliance with future EU regulation on hydrogen market^[5].

Proposals should also:

• Address health, safety and environmental considerations, and proof compliance to international standards (e.g. quality);
• Include plans for transport & distribution of hydrogen from / to storage site;
• Address sustainability and circularity aspects.

Applicants should provide a funding plan to ensure implementation of the project in synergies with other sources of funding. If no other sources of funding will be required, this should be stated clearly in the proposal, with a commitment from the partners to provide own funding. If additional sources of funding will be required, proposals should present a clear plan on which funding programmes at either EU (e.g. Structural Funds, Just Transition Fund, Innovation Fund, Connecting Europe Facility,…) or national levels will be targeted^[6]. In these cases, applicants should present a credible planning that includes forecasted funding programmes and their expected time of commitment.

Proposals are also encouraged to explore synergies with projects running under the EURAMET research programmes EMPIR^[7] and the European Partnership on Metrology (e.g Met4H2^[8]) concerning quality assurance measurements which aim at ensuring that the purity of hydrogen stored is at the expected grade.

This topic is expected to contribute to EU competitiveness and industrial leadership by supporting a European value chain for hydrogen and fuel cell systems and components.

It is expected that Guarantees of origin (GOs) will be used to prove the renewable character of the hydrogen that is produced. In this respect consortium may seek out the issuance and subsequent cancellation of GOs from the relevant Member State issuing body and if that is not yet available the consortium may proceed with the issuance and cancellation of non-governmental certificates (e.g CertifHy^[9]).

Proposals should provide a preliminary draft on ‘hydrogen safety planning and management’ at the project level, which will be further updated during project implementation.

Activities are expected achieve TRL 8 by the end of the project - see General Annex B.

The maximum Clean Hydrogen JU contribution that may be requested is EUR 20.00 million – proposals requesting Clean Hydrogen JU contributions above this amount will not be evaluated.

At least one partner in the consortium must be a member of either Hydrogen Europe or Hydrogen Europe Research.

Purchases of equipment, infrastructure or other assets used for the action must be declared as depreciation costs. However, for the following equipment, infrastructure or other assets purchased specifically for the action (or developed as part of the action tasks): underground hydrogen storage and interfaces of the underground storage with other elements like hydrogen producers, hydrogen consumers and hydrogen dedicated distribution & transmission network, costs may exceptionally be declared as full capitalised costs.

The conditions related to this topic are provided in the chapter 2.2.3.2 of the Clean Hydrogen JU 2023 Annual Work Plan and in the General Annexes to the Horizon Europe Work Programme 2023–2024 which apply mutatis mutandis.

[1] https://cordis.europa.eu/project/id/101006751

[2] https://www.hystock.nl/en/

[3] https://cordis.europa.eu/project/id/101007176

[4] https://cordis.europa.eu/project/id/101006632

[5] On 15/12/2021 under the Fit-for-55 package, the Commission proposed the Gas Decarbonisation Package – a new EU framework to decarbonise gas markets, promote hydrogen and reduce methane emissions; https://ec.europa.eu/commission/presscorner/detail/en/ip_21_6682

[6] Including applications for funding planned, applications for funding submitted and funding awarded

[7] https://www.euramet.org/research-innovation/research-empir

[8] https://www.euramet.org/index.php?id=1913

[9] https://www.certifhy.eu