But then you also have to re-heat it in the morning with combustibles to kickstart the generation again.

Yeah, they do, and get incinerated, unfortunately. A few every day, actually. Which is one of the reasons those never took off. Besides big upfront costs for the tower generator, there are additional costs for maintaining the generator with moving parts, and then for scraping the dead birds off the mirrors to top it off. All just to save a few pennies on mirrors instead of just chucking a bunch of solar panels into a field and mostly forgetting about them.