[jnsaff2]

Why too good to be true?

There are significant trade-offs with this technology.

It's storing heat, so if you need electricity then you eat a lot of efficiency. I think Vernon said ~45% round trip efficiency. Batteries are 90%+.

The storage is at a high temperature (500-600C) which means that you can't use heat-pumps to produce the heat to be stored. This means that you miss out on ~400% energy gains possible from converting electricity to heat.

So the efficiency is pretty low.

That said, solar PV is really cheap and moving large amounts of earth into a pile is also a very much solved problem so in some cases, notably higher latitudes which have very long days and low heat/electricity demand in the summer and the opposite in the winter, it could still be a very good solution.

[Sharlin]

The whole point is that the thermal energy is used directly, via district heating. These are not meant to store energy for electricity production (though they could do that if really needed – emergency power for various facilities? Maybe not worth it compared to diesel.)

Heat from existing thermal power plants can be stored directly and later distributed with no conversion loss; excess electricity from renewables can be turned to heat at 100% efficiency, but the problem is that peak heat demand and peak electricity supply do not typically coincide. Heat batteries are meant to solve that problem.

[jnsaff2]

The link in the OP comment is however talking about electricity generation (not excluding heat use tho) and energy being stored from excess PV.

[Sharlin]

Ah, sorry, missed the context.

[HPsquared]

Yeah the efficiency is much less than 40% if you compare to heat pumps. It'll be something like 15% compared to those.