I felt kinda bad about the last post, as Bill has been very nice to me, especially in private emails. Here is something nicer, then.
The Stirling has the theory to be the best of the heat engines. Nobody seems to be able to make one even close to the theory, or even cost effective or with adequate power.
There are other externally heated engines;
The Rankin engine, a close cycle engine that uses state change from liquid to gas and back. It has it uses too.
The Organic Rankin engine, which uses a lower state change temperature. People have built these from used auto parts and power them by very cheap solar trough. Why more people don't build this in their backyard I have no idea. Look up a project at MIT to see more.
The steam engine. A workhorse of a century, engineered to near perfection. An open cycle used in both piston and turbine. These are still used for coal and nuclear plants, and will be around for a long time. Not as dangerous as they used to be.
And our favorite, the Stirling. The best in theory but nobody seems to be able to figure out how to give birth to the wonder we all hope for. I'm not sure people are focused on why.
Yeah, so, we all know that.. and ... ?
The Stirling-acoustic is an example of perverting definitions. The passing back and forth of the hot/cold boundry is not gradual, but a compressed wall in the gas. A compressed wall in gas of equal temperature is what classic sound is, actually a wave of compression. But, it happens to be close enough to the same thing. The compression wave of a Stirling-acoustic can be heard and can be very loud.
The Stirling having no state change and capable of being built into Stirling-acoustic configurations is still early in the design stages. The use of resonat cavities is done a bit, and was the secret of the Stirling-acoustic that got launched on the space probe to run a 100 years without needing tweaking.
I say all this, because I want you to not lose faith in the Stirling, yet understand, that all we know, is not really nealy enough, even for those who spent much of their life on it.
I had a dream the other night. I dreamed I got massive funding to develop a Stirling engine for a submarine. Not to power it, but as a sonic weapon. It was a dark dream as we all must have, but why and how to make the Stirling the engine of the future for peace is out there. I sorta know what needs to be done.
Please forgive when I write harshly.