Underground hydrogen storage: The techno-economic perspective

Abstract

The changes in the energy sector after the Paris agreement and the establishment of the Green Deal, pressed the governments to embrace new measures to reduce greenhouse gas emissions. Among them, is the replacement of fossil fuels by renewable energy sources or carbon-neutral alternative means, such as green hydrogen. As the European Commission approved green hydrogen as a clean fuel, the interest in investments and dedicated action plans related to its production and storage has significantly increased. Hydrogen storage is feasible in aboveground infrastructures as well as in underground constructions. Proper geological environments for underground hydrogen storage are porous media and rock cavities. Porous media are classified into depleted hydrocarbon reservoirs and aquifers, while rock cavities are subdivided into hard rock caverns, salt caverns, and abandoned mines. Depending on the storage option, various technological requirements are mandatory, influencing the required capital cost. Although the selection of the optimum storage technology is site depending, the techno-economical appraisal of the available underground storage options featured the porous media as the most economically attractive option. Depleted hydrocarbon reservoirs were of high interest as site characterisation and cavern mining are omitted due to pre-existing infrastructure, followed by aquifers, where hydrogen storage requires a much simpler construction. Research on data analytics and machine learning tools will open avenues for consolidated knowledge of geological storage technologies.

Keywords: economic requirements; energy transition; porous media; rock cavities; technical parameters; underground hydrogen storage.

Figure 1.

Countries with a carbon tax in 2020, marked if at least one sector has implemented one carbon emissions tax instrument ( a), and countries with carbon emissions trading system, marked if at least one sector is covered by one (This figure has been reproduced with permission CC BY-NC-ND 4.0 Attribution-Non-Commercial-No-Derivatives 4.0 International from 2).

Figure 2.. Comparison of storage capacity and discharge duration of above ground and underground technologies.

Figure 3.. Requirements of Lined Rock Caverns.

Figure 4.. Requirements of Refrigerated Rock Caverns.

Figure 5.. Salt caverns requirements, where H is height and D is diameter.

Figure 6.. Requirements of porous media.

Figure 7.. Cost analysis of UHS for different geological formations.

A 50 % cushion gas scenario was used for the aquifer option, and an illustrative site characterisation cost of 10 % of the area was used. Columns missing for a total installed cost, total operating expenses, total investment and annual cost/tonne are not estimated for the other options. Columns missing for compressor, cushion gas, site characterisation, cavern mining, and pipelines and wells are not estimated for the refrigerated mined caverns, while their absence in all the other geological formations reflects the negligible cost.

Figure 8.

Comparison of total cost estimation for UHS options, considering ( a) stored gas and ( b) energy. Different colors reflect the cost ranges where they exist.