How does a geological subsurface store energy?

The geological subsurface, particularly porous formations, can offer grid-scale energy storage options , , either by storing a chemical energy carrier, such as hydrogen or methane , , or by storing mechanical energy as compressed air , , , or as sensible heat (e.g., , ).

How can thermal energy storage be adapted in geological settings?

The storage of mechanical energy in the form of compressed air in subsurface caverns or aquifers is another innovative technique that can be adapted in many geological settings , , [*291]. Most underground thermal energy storage systems involve storage of heat at temperatures between 50 and 95 °C .

How do geotechnical engineers work with energy storage?

Geotechnical engineers have been involved with energy storage through the design of reservoirs for pumped-hydro energy storage, where water is pumped to a reservoir with higher elevation during times when electricity costs are low, and electricity is generated through hydro-power.

Why is energy storage important in the geological subsurface?

Energy storage in the geological subsurface provides large potential capacities to bridge temporal gaps between periods of production of solar or wind power and consumer demand and may also help to relieve the power grids.

What is used subsurface space in Geotechnical Energy Storage?

Three categories of used subsurface space have been identified and developed in the ANGUS+ project in the context of geotechnical energy storage: firstly, the “operational space” (Fig. 2 ), i.e., the space directly used by the storage operation, which comprises the technical installations and the space taken up by the injected gas or heat.

How can geotechnical optimisation of achievable power be achieved?

Geotechnical optimisation of achievable power may be achieved through innovative well design. Compressed air energy storage in geological porous formations, also known as porous medium compressed air energy storage (PM-CAES), presents one option for balancing the fluctuations in energy supply systems dominated by renewable energy sources.