Giving up the heat is going to take efficiency pretty low.

Gas is a usable short term fill-in for wind and solar. We can’t use it long term, it still puts a lot of GHG into the air and we probably don’t have a long term supply.

Storage should replace NG and, hopefully, soon.

One in which the captured heat is stored as hot water and used to reheat the air. This is likely best for smaller scale, more frequent turnover storage. A company called LightSource is working on CAES with captured heat built on shipping container scale. This could be a good solution for moving supply to demand during the daily cycle.

Modular, factory built, easy to transport and site.

One in which we store very large amounts of air for the occasional times when we need a lot of supplemental generation. For when wind and solar inputs are way down for multiple days.

If the heat could be captured and used, say in an industrial process, the gas saved by the factory could then be used to reheat the stored air on its way to the turbines.

Use the underground chamber, abandoned mine and build a factory next to it, one that needs significant heat.

We’d have ‘deep backup’ storage which would be filled with only the cheapest of electricity. The compression heat would be used as produced. Avoided gas could reheat the stored air. And if we ran out of stored air we could still run the turbines with gas and atmospheric air.

In real grid cycles they are sadly lower, still capturing some of the heat is better then nothing and a lot better then no storage. As long as it can compete with gas turbines its fine.

I looked a lot into this technology since in theory you can just seal old mine shafts and pressurize them. That promises multiple GWh* per spot and next to no impact on the landscape. But doing it on this scale basically requires you to have a usage for that heat or you pay a hefty price. I really do like this idea since a lot of Germany looks like a swiss cheese underneath and it would be so easy and elegant if it weren’t for this thermodynamic.

*There is a gas power plant “McIntosh” in Alabama US that can utilises CAES. It stores up to 2860 MWh in 538000 m³ (a proper mineshaft is a lot bigger) which can be released over 26h at a max rate of 110MW. Note, this thing needs to burn gas, it basically offsets the compressor losses of the gas turbine by using the air that was compressed earlier but this is still storages. There is an older one of those in Germany although storing way less air.