Comment by pfdietz

If the heat is stored at high temperature, but the demand (for heating buildings, say) is at lower temperature, it could make sense to generate power, then use that power to drive heat pumps. You could end up with more useful heat energy than you started with, possibly even if you didn't use the waste heat from the initial power generation cycle.

Alternately, if you are going to deliver the heat at low temperature to a district heating system, you might as use a topping cycle to extract some of the stored energy as work and use the waste heat, rather than taking the second law loss of just directly downgrading the high temperature heat to lower temperature.

High temperature storage increases the energy stored per unit of storage mass. If the heating is resistive, you might as well store at as high a temperature as is practical.

Gas-fired heat pumps have been investigated for heating buildings; they'd have a COP > 1.

I am interested if there are any cheap small scale external combustion engines available (steam? stirling? ORC?)