INTRODUCTION

Based on the forecasts expressed by several organisations and institutions (IEA, IRENA, DNV, Bloomberg, etc.), the demand for hydrogen will grow significantly over the coming decades, initially more closely linked to current uses as a raw material and, from the 2030s onwards, developing significantly in uses linked to energy [1]

In this context, medium and large-scale hydrogen storage will become increasingly important in the hydrogen market.

According to many studies, underground storage is the most economical way to store large quantities of hydrogen for later distribution. [2] 

Regarding the possibilities of underground hydrogen storage, there is literature where a wide variety of options have been analysed:

  • Salt caverns
  • Porous media (depleted hydrocarbon reservoirs, aquifers)
  • Abandoned mines and artificial rock caverns

OBJECTIVES

The main objective is to demonstrate the suitability of underground storage as a form of large-scale hydrogen storage, considering the different existing technologies and analysing the advantages, disadvantages and degree of maturity of each of them.

DEVELOPMENT OF THE STUDY

The underground storage options described depend fundamentally on the geological conditions of the sites where this storage is to be carried out. In the study, a synthesis is made of all of them in relation to their operation, performance and potential, based on the advantages and disadvantages detected, in order to provide an overview of the status of this technology. [3]

Regarding the viability of the different options, there are currently hydrogen storage facilities in salt caverns in operation, while for the other options, only research projects are underway.

SALT CAVERNS

  1. DESCRIPTION OF THE TECHNOLOGY

Salt caverns are artificially created cavities in salt deposits. Their dimensions must be adapted to the characteristics of the salt layer, and the pressures are mainly influenced by the depth at which they are located.

These caverns can be found at depths of between 200 and 2,000 m and have a height of between 100 and more than 300 metres, which can lead to the storage of hydrogen at pressures of more than 200 bar. Thus, caverns can be found in a wide range of sizes, from 50,000 m3 to more than 1,000,000 m3.

  • ADVANTAGES

Impermeability to hydrogen.

Low reactivity.

Sealing capability due to salt plasticity.

Allows multiple injection-extraction cycles.

Technology in use.

  • DISADVANTAGES

Identification of precise locations for cavern construction.

Cavern construction costs.

POROUS MEDIA

  1. DESCRIPTION OF THE TECHNOLOGY

Porous media include depleted hydrocarbon reservoirs and aquifers, found in natural cavities, which become geological traps where hydrogen can be stored.

These reservoirs can be found at depths of 200 to 4,000 m with sizes up to more than 1,000,000,000,000 m3.

  • ADVANTAGES

Can offer larger storage capacities than salt caverns.

Locations already known and no cavity construction is needed.

  • DISADVANTAGES

There are many uncertainties regarding the behaviour of hydrogen in the interior, particularly concerning the reactivity and impermeability of porous media in relation to hydrogen.

No previous experience.

ABANDONED MINES AND ARTIFICIAL ROCK CAVERNS

  1. DESCRIPTION OF THE TECHNOLOGY

These are rock cavities, either as part of abandoned mines or as drilled and lined caverns.

The geometrical characteristics of abandoned mines depend on the previously existing excavation; in the case of lined rock caverns, depths can be up to about 200 m with physical volumes of about 20,000 m3 to 100,000 m3.

  • ADVANTAGES

Impermeability and low reactivity.

Cavity stability.

Moderate operating costs.

  • DISADVANTAGES

High construction costs.

No previous experience.

FACILITIES IN OPERATION OR ONGOING PROJECTS [4]

PROJECTTYPELOCATIONSTATE
Clemens DomeSalt cavernUSAOperation
Moss BluffSalt cavernUSAOperation
Spindle TopSalt cavernUSAOperation
TeesideSalt cavernUKOperation
HypsterSalt cavernFranceResearch
HyGéoSalt cavernFranceResearch
H2CastSalt cavernGermanyResearch
HyCAVMobilSalt cavernGermanyResearch
HyStockSalt cavernNetherlandsResearch
HyUSPRePorous mediaEUResearch
HyunderPorous media / Salt cavernEUFinished (project)
HystoriesPorous media / Salt cavernEUFinished (project)
Sun StoragePorous mediaAustriaResearch
UndergyPorous mediaSpainResearch
HyBRITLined rock cavernSwedenResearch

RESULTS AND CONCLUSIONS

Large-scale hydrogen storage is becoming a strategic link in the hydrogen value chain and the European energy strategy.

Although underground hydrogen storage technologies have been in operation in various parts of the world for decades, they are limited to salt caverns and four locations in the USA and UK.

Further study of the different existing underground storage options, which is being carried out through numerous research projects at different stages, is needed to resolve uncertainties, particularly in relation to the behaviour of hydrogen and its interaction with the storage medium.

REFERENCES

[1] DNV. (2022). Hydrogen Forecast to 2050.

[2] Tanay Sidki Uyar. (2020). Accelerating the Transition to a 100% Renewable Energy Era. Springer.

[3] Olaf Kruck, & Fritz Crotogino. (2013). Benchmarking of Selected Storage Options – “Assessment of the potential, the actors and relevant business cases for large scale and seasonal storage of renewable electricity by hydrogen underground storage in Europe”. Project Hyunder.

[4] Hydrogen TCP-Task 42. (2023). Underground Hydrogen Storage: Technology Monitor Report.