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bgraham111 t1_j4m9v5b wrote

Reply to comment by FluxD1 in How do non electric heat operated fans work? by ranman12953

I grew up in Amish country (even been to an Amish wedding reception), and know they use steam engines... never a Stirling engine. But those steam engines are beautiful.

I interviewed at a company that was planning on building Stirling engines back in 2008. They told me (no idea how true) that other than little toys and novelty sterling engines, there were less than 300 large sterling engines in the world (and they wanted to produce 3000 a month). They went out of business.

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Blazin_Rathalos t1_j4mavdk wrote

...What was even their business plan for making that many then?

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bgraham111 t1_j4mbg0j wrote

Solar power. Use parabolic mirrors, track the sun, heat up the Stirling engine. The prototypes worked, and worked well. Better than photovoltaic cells.

The trick is manufacturing the Stirling engines, which.... is not easy.

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Inutilisable t1_j4mfa65 wrote

What is tricky about the manufacturing exactly?

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SacredRose t1_j4n4dfc wrote

You need to build something with as little friction as possible and it needs to run super smooth all the way around. I imagine the precision machining needed to build larger versions is gonna be pretty high and tricky so it won’t be cheap.

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Inutilisable t1_j4n7mm4 wrote

I designed lab equipments with precision pistons made of graphite in glass tubes. It’s really good but it is expensive, especially in low quantities, something like >40$ for 1/2” diameter piston, a few inches long. There was no other way to get low friction. I imagine that other constraints gets involved when you want to get any useful energy from it, at large scale.

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joalheagney t1_j4pb3u8 wrote

The other big issue is the driving gas. You want something with a really low molecular mass for maximum thermal expansion. Hydrogen gas would be ideal if it didn't have a distressing tendency to diffuse into and through metals. And. You know. Explode in contact with heat and Oxygen.

Helium is half as good (twice the MM) ... but incredibly expensive and almost as hard to contain. Doesn't explode though which is good.

And then you're into N2, O2 and you may as well use air for obvious reasons. At about 14 times the MW of hydrogen gas. :/

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Turksarama t1_j4oxg1d wrote

I remember when people thought that solar Stirling generation might become a thing. Then the price of PVs never stopped plummeting.

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ozspook t1_j4q8opp wrote

Stirling cryocoolers were quite popular for superconducting high-q microwave and mobile phone base station filters, for a while.

Pretty good 2nd hand source for making Stirling engines.

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