>A heat engine. So it is subject to the Carnot engine efficiency limit. No thanks. Direct solar cells ought to be much better. Perhaps surprisingly, photovolta

>A heat engine. So it is subject to the Carnot engine efficiency limit. No thanks. Direct solar cells ought to be much better. Perhaps surprisingly, photovoltaic cells are also subject to Carnot's efficiency limit! The hot reservoir temperature is the optical temperature of the Sun, and the cold reservoir temperature is the panel temperature. Plugging in numbers we can see that Carnot's theorem limits solar cell efficiency to ~95%. I do agree with your conclusion though: PV is much better. It's a simpler, cheaper system.