What can you tell me about Stirling engines?

I'm interested in using a Stirling engine in a solar energy project. From reading around and doing some numbers it looks like I'll need around 1.5 kilowatts, and something in the vicinity of 30% efficiency or upwards would be nice, though I realise this may be overly optimistic. So, what's available, how much will it cost, what temperature differential is ideal, how big and heavy are these things, etc. Any info I get would enormously helpful. Cheers, Daniel.

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LinuxH4x0r8 years ago
I'm also interested in using solar for sterling engines. I like the idea of using boiling oil or water heated in a parabolic dish or trough.
SolarFlower_org (author)  LinuxH4x0r8 years ago
Parabolic troughs are easy to make and use, but quite inefficient and large. Much more efficient is a parabolic dish, but then you need to keep it very accurately pointed at the sun.
Right. But for small homes a less efficient easier method might be more realistic
SolarFlower_org (author)  LinuxH4x0r8 years ago
Yup. Especially if you've got something like a roof where you can take up some space. What information have you found so far? Any numbers?
Not a whole lot. Once the snow clears up I'll try tinkering around until I get something. You might be interested in gutting old rear projection TV to get their enormous lenses
SolarFlower_org (author)  LinuxH4x0r8 years ago
Ok, stay in touch with anything you figure out. Good idea bout the lenses, I was wondering where I could source those. Wish it was snowing here in Scotland. Although I did get hailed on sideways yesterday...
PKM8 years ago
Yes, I know exactly the website you want. Check out stirling-tech.com first, they sell a commercial cogeneration engine that sounds a lot like what you want.

The tl;dr of their calculations is that you can run the engine, generating about 4kW of electricity and something like 30kW or 115000 BTU/hour (who uses BTU? srsly) of heating from recovered heat, with a heat input of 38kW. This could be achieved by burning 6-10 cords of wood per year (38,000 lbs or about 17 tonnes), but presumably if you can heat the thing externally you might be able to use concentrated solar. A 38kW concentrated solar system in someone's back yard would be a sight to see :)

This site (translated from German) appears to sell what you are looking for (a 500W Stirling) with exposed heat receiver so you could presumably heat it however you want to. I have no idea if the site is still current or not but it looks quite promising. His old site (again might be abandoned but has more information).

This site, difficult to read but an absolute treasure trove, has possibly everything practical you'd ever want to know about Stirling engines and heat engines- it's where I found the link to stirling-tech and all sorts of other obscure stuff.
PKM PKM8 years ago
Am I to assume that you want to build some sort of solar-stirling power generator? Additional stuff that I forgot just then- 30% efficiency is pretty optimistic in terms of heat to shaft power. For a commercial high-temperature-differential engine figure more like 10-20%, for a home-built one it will be less. Them's the rules, it seems.
SolarFlower_org (author)  PKM8 years ago
Wow... that's... terrible.
Luckily, before this information had a chance to get me too frightened and depressed, I found this:


Sunpower EG-1000, 30% efficient (or more), 1kW (or more) pretty small.
I'm still trying to find out how much it costs, but at least if these guys have done it means it can be done. Part of their mission statement apparently is doing these things as cheap as poss.

Cool! I was unaware of that engine, it sounds a lot better for what Linux seems to want anyway. I think the one I described had two main aims, being reasonably cheap to produce (air as working fluid rather than hydrogen, etc), and having an exposed external heat exchanger so you could run it on logs, wood pellets, agricultural waste etc. It's also designed for cogeneration (heat and power from the same fuel) so might be designed to produce enough heat to heat a house simply with electricity efficiency as a secondary aim. The Sunpower unit looks a lot more futuristic, is specifically designed for electricity generation so is better at generating electricity but is probably hellishly expensive, and I'm not sure how well it would take to alternative fuels. Still, they were producing the engines for the Sandia CSP solar farm so the EG-1000 might be great for use with solar. I'd love one of those engines to experiment with...
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