Heat expands a gas, pushes a piston which couples to some gears which turns a crankshaft which turns a wheel of copper wire between magnets which makes electricty.

Okay, can't we make the sun be our heat source?

But Unit capacity is only 25 KW. Still, that's enough to power 8 to 10 houses. One might want to design new residential areas around such devices into areas like the Southwest

The future Desert Sun Farm:

An optimized calculation shows that 100% US Electrical needs could be meet using this technology over an area about 20% the size of Nevada. Reality is probably 5 times worse.