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Comment by naasking | Hacker News Reader

You'll get better efficiency running a Stirling engine from a lightweight solar collector. I actually wonder how it would compare if you equalize the weight.

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That's one of those areas that's been talked about in the literature ceaselessly since the 1970s with almost 0% commercialization. That's the normal scenario for energy technologies, cases like PVs and lithium batteries are the rare counterexample.

This is different. This person wants a solution that can be built with common materials with fairly standard tools and at small scale, not a scalable commercial power plant. You can build Stirling engines at home with common materials. We're not comparing 10MW power plants here.

So the question is, for a comparable weight and size as this solution, how difficult would it be to build a solar powered Stirling engine and what would the power output be? I expect the Stirling engine to easily come out on top.

rankine cycle lets you cross vapor dome to access latent heat. enables scaleup

Is there a reason? It's curious to me that you don't see many Stirling engines. Is there a big downside to them?

There is this

https://www.stirlingengine.com/why-not-popular/

I've heard that the manufacturing tolerances are tough.

One problem is that people systematically publish optimistic cost estimates for new technologies and that these don't get updated. I still see papers that cut-and-paste cost estimates for various technologies from 1970s papers and don't even bother to adjust for inflation.

You can certainly couple a Stirling engine to a parabolic dish

https://en.wikipedia.org/wiki/Solar-powered_Stirling_engine

but it just isn't cost effective with PV when you consider the cost of the engine, the cost of the dish, etc. And think of all the moving parts to maintain! A big solar thermal plant looks ready to shut down

https://www.greenprophet.com/2025/02/ivanpah-fails-value/

not just because the capital costs were high but because the operating costs are high. It's hard for anything to compete with PV because the operating costs are low (you clean them once in a while) and the capital cost keeps dropping because it is so fiercely competitive -- something that happens rarely (hydrofracking for hydrocarbons was another example)

Ivanpah failed because of the maintenance costs of the motors moving the reflectors, not the heat engine. Those motors are not really a factor in the kind of setup comparable to this article. Stirling engines actually require considerably less maintenance than combustion engines, and the maintenance is simpler because the engines are simpler.

Manufacturing tolerances are only relevant if you want to maximize efficiency for competition at commercial scale power production, which is not this case.

That's an excellent idea, especially if you have aluminized mylar or stainless steel.

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