Pete C. wrote:

We have overblown project ideas on our to-do-who-knows-when lists. I
have a grand idea of converting a 3m sat dish into a parabolic solar
steam boiler to feed a steam engine generator followed by an absorption
chiller. Don't know if I'll ever get a round-tuit, but it's a neat idea.

Much better to run a high temp differential Stirling engine off solar
input. A polished 3 M dish can melt steel in seconds at the focus. A
pretty small Stirling engine can deliver a lot of power if you compress
the working fluid, and use either Helium or Hydrogen, instead of air.
There are tricks (called the Heylandt crown) to keep the hot gas off the
seals, so all the seals run at modest temperature. Then you can use
teflon-bearing seal material for piston rings, and put sealed ball
bearings on the mains and rods. This allows you to have no liquid lube
in the engine, so oil mist won't coke up in the heater tubes. You want
to run the heater tubes as hot as your materials can stand, like 600 -800 C.

You can build a hermetic machine, and put a little brushless PM
alternator inside the crankcase. Drive whatever you want with the
electrical output.

Jon