as close as you’ll come to a perpetual motion machine

American Stirling Company FAQ

How do Stirling Engines work?
Are Stirling engines really the most efficient engines possible?
If Stirling engines are so efficient, why don’t I have one in my car?
Who was the Rev. Robert Stirling anyway?
What are Stirling engines being used for today?
Who invented this type of Stirling Engine?
The world has thousands of low temperature difference heat sources why don’t you build a full power engine that uses them?
Does American Stirling Company build any full power Stirling engines? If not, do you plan to build any?
Where can I get a 5 to 25 kW Stirling engine for my house, car, boat, etc. that will run on any fuel from cow chips to sunshine and be price competitive with a Honda generator of the same capacity?
Could a good Stirling engine be built by starting with a small-block Chevy V8, or perhaps an air compressor, and converting it to a Stirling?

I had heard about Stirling engines is passing but had never really understood them. Now that I have found this site (thanks to RJL20), it’s easier to understand.

Here in the Pacific Northwest, we don’t get as much rain as we’re rumored to, but we get very intense sunlight. Something to do with the angle of the sun or something, I think. Anyway, I’ve often wonder if there was a way to harness that for electrical generation or mechanical work. Since the Stirling engine derives its power from heat differentials, I wonder if we get enough heat/light drive one of these.

This ties into another idea that’s been bouncing around in my head. 30 years ago, during one of the oil price shocks, an uncle of mine in upstate New York switched from oil heat to a wood stove. Being a plumber by trade and a pretty clever fellow, he figured that it was all very well to generate heat, but storing it was more useful: being able to have heat without a fire — making it possible to let the fire go down at night or during a warm spell — would a good thing to have. So he built a heat vault. It was a large (6-8 foot on a side) cube of sand, in a wooden box. Inside the vault was a spiral of plastic water piping: the notion was to heat the water, pump it through the vault and heat the sand. Then later, draw the heat back out by pumping water through another pipeline.

So there are two possibly related ideas here. The heat storage idea would be useful in a cool clime like ours, but I also wonder if it could be useful in driving a Stirling power generator. It sound like the required engine would be extremely large — nothing like a Honda generator — but I could envision it being underground or in an outbuilding with the heat vault.

As the folks at American Stirling note, price per power unit is still very much against the Stirling. But that may change.