In contrast to compressed air storage, a fairly mature and widely-used large scale storage method involves pumping water from lower elevations to higher elevations. This practice is currently the most frequently used way of storing electricity, accounting for over 129 GW worldwide.
Conclusion: A number of storage technologies such as liquid air, compressed air and pumped hydro are significantly more efficient than Green Hydrogen storage. Consequently much less energy is wasted in the energy storage round-trip.
The technologies that are most suitable for grid-scale electricity storage are in the top right corner, with high powers and discharge times of hours or days (but not weeks or months). These are Pumped Hydropower, Hydrogen, Compressed air and Cryogenic Energy Storage (also known as ‘Liquid Air Energy Storage’ (LAES)).
Briefly, two other potential ways to store energy on a large scale are flywheels and a smart grid. The concept behind flywheels is fairly simple in that it is just the conversion of electrical energy to rotational kinetic energy for storage and then conversion back to electrical energy using a generator for extraction.
These are Pumped Hydropower, Hydrogen, Compressed air and Cryogenic Energy Storage (also known as ‘Liquid Air Energy Storage’ (LAES)). Fig. 2 Comparison of electricity storage technologies, from .
Even with potential safety concerns such as vessel ruptures or overheating, the storage of compressed air does not appear to be such an unreasonable method for large scale energy storage given the obvious abundance of air and relatively large amount of underground space available for storage.