> The capacity cost of thermal storage has not been the bottleneck for commercialization, but rather the round trip efficiency.

Has there been any effort to do this directly at power plants, so there isn't a round trip?

You have a heat source that generates the same heat 24/7 (e.g. nuclear reactor). You have solar panels that generate power only during the day. So you put the heat from the heat source into storage while solar is generating, then take it back out after the sun goes down.

You're not going from electricity to heat back to electricity, you're just not converting the original heat into electricity until later in the day.