Underground hydrogen storage

Hydrogen Underground Storage (HUS) as a key element of the modern energy supply chain. It is a process consisting of liquefying, compressing and expanding hydrogen for direct injection of hydrogen into the underground storage (compression to a pressure of 20-180 bar, max. to the pressure of fracturing the rock mass) and its emptying. 

Activities in this area [underground hydrogen storage] are related to obtaining a concession for underground tankless storage of the substance. It is necessary to agree on this with the minister responsible for the management of mineral deposits.

Underground hydrogen storage will contribute to increasing the stability of power grids, increasing the share of renewable energy sources (RES), improving the efficiency of energy systems, protecting fossil energy sources, reducing the impact of energy production on the environment and, above all, is an element of the energy cycle:

energy production → conversion to hydrogen → hydrogen storage → reconversion of hydrogen to other types of energy → energy consumption 

This gives a chance to overcome barriers to the development of hydrogen energy and encourages work on selection of appropriate technology for hydrogen production, its transport and recognition of geological structures for its underground storage [in the case of e.g. contact of hydrogen with rocks, mineral reactions could be a problem, and the increase in pressure (present at greater depths) could cause them to accelerate significantly].

Transporting and injecting hydrogen through drilling into geological structures will require appropriately prepared infrastructure.

Underground storage located beneath the surface of the earth, in deep geological structures, in salt caverns, in depleted oil and gas deposits and in deep aquifers should ensure that gas injected into the deposit will be collected in the largest possible quantity and without losses caused by escapes.

Hydrogen storage in deep aquifers is almost the same as in depleted oil or gas deposits, with the difference that the porous rock matrix is filled with brine, not hydrocarbons. The advantage of this type of storage is a relatively intact geological structure. The existing limitations are higher costs of geological exploration, higher investment and operating costs, and an increased risk of gas leakage. Determination of requirements and conditions determining the selection of a deposit or geological structure for an underground hydrogen storage should be based on a thorough geological analysis using reservoir engineering..

The basic criterion for a structure intended for underground hydrogen storage is the geological tightness of the underground storage, also ensured by the tightness of the overlying layers.

The greatest probability of success of the project implemented in the area of hydrogen storage will be achieved by using hydrogen storage technology in salt caverns. The specific viscoelastic properties of salt guarantee the tightness of caverns when storing gases under high pressure and the possibility of building large voids without their artificial support. The relatively low costs of borehole cavern leaching and a small surface installation serving the storage are important.

The technical tightness of the installation is also important, which includes the tightness of the holes made in the deposit, surface devices, including gas transport pipelines. The appropriate selection of operating conditions is also key, taking into account the specificity of the deposit and the selection of the appropriate gas injection and withdrawal pressure, so as not to exceed the fracturing pressure of the rock mass (at which delamination of the rock occurs).

The location of the underground hydrogen storage should take into account the limitations in the possibilities of spatial development of the area, such as the presence of protected areas, the possibility of managing brine during the construction and operation of storage facilities in salt caverns. The location assumptions must be created based on the concept of sustainable development, taking into account natural limitations, the needs of the economy and the expectations of the local community.

It is necessary to demonstrate the need for an underground hydrogen storage facility as an element of the energy cycle that is environmentally friendly for the developing hydrogen energy sector, as well as the economic profitability of its construction.

All this requires refinement and development of new concepts and new technical solutions.

The average price of electricity will be the main cost determining the profitability of underground hydrogen storage.

In the scope of underground hydrogen storage it is necessary to assess the possibility of implementing the undertaking from the area of Wolin Island. This requires conducting appropriate research and reconnaissance work, which will provide the basis for submitting a full application for a Concession for underground tankless storage of the substance [hydrogen], as well as assessing the potential threat and limiting any risk when making further decisions, including macroeconomic ones.