I never like the sterling engine.
It is a great nifty device, but its not... inefficient is not the word, it just becomes troublesome to get large energy out of. As in, that big array has to be pointed directly at the sun to get an output that is less than a little generator.
The other half of the problem with sterling is you need a cold side too. And where does that come from when you are heating the air around the thing.
Boiling a refrigerant and using the steam to move a turbine or engine allows you to get more work in a smaller area. Yes, it is more complex, but it works better. You know what you need to get a pressure head, you know what that pressure differential will do. You can reliquify the refrigerant at another spot. (away from the heat collectors)
And, the ideas i am conveying are meant to power a small community.
I always envisioned sticking one half in some running water and the other half out. With today's technology, there has to be some material that could increase the temperature differences between the two sides.
Then, use touchless magnets to power a generator, to solve the torque issue.
And already, the sterling engine is getting quite complex, its simplicity, the reason for using it, diminishes.
Further, changing a liquid to a steam gives more energy out then you put in.
And yes, there are designs for a perpetual motion steam engine, if you can make each of its pieces efficient enough.
Funny enough, it is not really the difference in pressure that drives an engine. It is actually the temperature difference. So, you can say that the sterling concept applies to all engines.
I think Cody's Lab or someone put one in a vacuum chamber and it didn't run. So, if you can put it under pressure, it would also run better.
BTW, the 8-cyclinder model in the third video uses water cooling and he made it with scrap parts. And other people have already talked about using magnets to get the electricity.
Of course, they use them on nuclear subs.