[jaapz]

> But storing the heat they produce has not been possible

Many heat pumps are installed with a large insulated buffer of water (for ex. 300L), which stores heat pretty well?

And homes that use underfloor heating in concrete can store heat pretty well too. Many people use that to heat up the home when energy is cheap and disable the heat pump when it is expensive.

[V__]

Water (given enough volume) is a pretty good heat storage.

https://youtu.be/Bm7L-2J52GU?t=270

[mock-possum]

It can be a pretty good ‘battery’ too

https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...

[BrtByte]

It's not that heat storage didn't exist, it's that this is closer to a "thermal battery" than a thermal flywheel