
Let's Build a Can Stirling Engine (2000) - DanBC
http://www.bekkoame.ne.jp/~khirata/english/mk_can.htm
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scottlocklin
One of the things which really, really rustles my jimmies is computer nerds
talking about matter the way they talk about Stirling engines. Someone once
upon a time told them that Stirling engines were efficient heat engines which
work on diffuse heat sources, and suddenly, Mr nerd wants to stick them
everywhere. No. Unlike using some sorting or hashing algorithm, there are
tradeoffs and complexities in technologies involving matter beyond anything
you do in your day to day work. "Stirling engine" isn't some kind of algorithm
you can put everywhere like your favorite red-black tree implementation.

Stirling engines, like all heat engines, work more efficiently with large
temperature differentials: this means advanced materials. External combustion
immediately puts you in a weird and unfamiliar engineering place where you
have the firey bits outside the piston where you can do the usual things to
keep it under control. Cooling is also different from just farting out exhaust
and pumping water through the block in a normal engine. If you don't have a
large temperature differential you have shitty efficiency and it's not worth
doing. Practical Stirling engines which do useful work, whether for heating or
cooling, are usually large, have sealed, pressurized helium as working fluids
(oh? you don't know about working fluids in Stirling engines?), complicated
gearing mechanisms and sometimes even magnetic coupling to the outside world,
and have extremely complex and precision machine parts compared to the slop
you see in consumer grade items like a Porsche Engine. Ratios in the engine
are often tailored to a very specific use case; and will work for shit if your
heat spec is outside that very, very narrow use case. Go have a look at what
goes into designing a real world Stirling engine for example in [0].

People don't use Otto/Rankine/Brayton/whatever because of some live-steam or
anti-Stirling conspiracy: they use it because Stirling engines, outside of a
few mostly unimportant use cases, are usually expensive _and_ shit. The two
most widespread industrial uses of the things I can think of were a Chrysler
air conditioner[1] and a coleman beer cooler[2], both using the same Japanese
built Stirling cooler. Even in these use cases, which, mind you are using a
Stirling engine in reverse from what HN weebs want them for, they didn't
exactly cover themselves in glory. They were expensive, heavy, fragile and not
as efficient as would justify their bad qualities over a more standard cooling
unit.

[0][https://ntrs.nasa.gov/citations/19830022057](https://ntrs.nasa.gov/citations/19830022057)

[1] [https://docplayer.net/40169613-The-reliability-
development-o...](https://docplayer.net/40169613-The-reliability-development-
of-miniature-stirling-cryocoolers.html) (I think)

[2][https://kk.org/cooltools/coleman-
stirlin/](https://kk.org/cooltools/coleman-stirlin/)

~~~
linspace
I cannot see the relation between your rant and the article which is about a
didactic implementation by some teacher.

~~~
scottlocklin
scroll down

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kmstout
> The Gotland-class submarines of the Swedish Navy [...] are the first
> submarines in the world to feature a Stirling engine air-independent
> propulsion (AIP) system [...]

[https://en.wikipedia.org/wiki/Gotland-
class_submarine](https://en.wikipedia.org/wiki/Gotland-class_submarine)

~~~
geomark
The manufacturer of the Stirling engine for those submarines, Kokums, is the
source of the engines used for a dish-Stirling solar energy system I worked on
for a licensee of Stirling Energy Systems[1]. It was a concentrating solar
energy system consisting of a parabolic mirror focusing sunlight onto a heater
head atop the Stirling engine. Quite efficient at around 30% conversion of
direct sunlight to electricity - each unit generated about 25kW under clear
skies. Quite a simple system - just a big mirror, sun tracker, Stirling engine
and generator. Super reliable - no nasty combustion products. And not very
expensive - BOM cost about the same as a mid-size car. But dropping PV prices
ended up killing it.

[1][https://en.wikipedia.org/wiki/Stirling_Energy_Systems](https://en.wikipedia.org/wiki/Stirling_Energy_Systems)

~~~
VBprogrammer
I've come across those Stirling engine parabolic dish systems before and
always thought they looked really impressive. Definitely installed in my dream
off grid retirement place somewhere sunny.

~~~
geomark
Although quieter than ICEs, those engines are not silent. Too noisy to be
close to homes. You would need to keep that in mind in your off grid dream.

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phobosanomaly
In a similar vein, if you haven't watched a pop-pop boat circumnavigate your
bathtub, you haven't lived.

[https://en.wikipedia.org/wiki/Pop_pop_boat](https://en.wikipedia.org/wiki/Pop_pop_boat)

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nanomonkey
Can anyone point to the reason(s) why Stirling Engines appear to be
unobtainable for stationary power generation? I've been wanting a reasonably
sized one (say 2-5kW) for quite some time to run off of woodgas, or other high
temp heat sources. Size doesn't really matter, I just want something
relatively quiet, that needs much less maintenance than an internal combustion
engine.

~~~
Izkata
Heh, I actually came here to take advantage of this post to ask something
similar: Could a Stirling engine be used to, say, charge a battery using the
exhaust heat from an AC unit?

~~~
pjc50
The energy generated is related to the difference in temperature. So if you're
using AC out as hot and ambient as cold, the generation will be small, and
it's necessarily much less than the energy spent to run the AC.

~~~
regularfry
Now you've got me wondering if you could design a reverse-stirling engine that
runs off an intensely endothermic reaction of some sort.

~~~
pjc50
The engine only requires a "hot" side and a "cold" side, so there's no reason
why the cold side can't be way below ambient temperature, such as an
endothermic reaction or a tank of liquid nitrogen. Here's a video of a guy
running one of those coffee-cup-top toy engines off liquid nitrogen:
[https://www.youtube.com/watch?v=O6eEvU5piQg](https://www.youtube.com/watch?v=O6eEvU5piQg)

Some people have proposed this as yet another bulk energy storage system for
the grid; giant underground cryotanks of liquid nitrogen. With careful design
the same gear could be used in "forwards" or "reverse" mode. The limit is that
the Carnot efficiency isn't great.

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markvdb
A stirling engine might be a perfect part for a bare bones open hardware
hybrid car.

A stirling engine might not produce enough power to power the wheels directly,
but it could produce electricity quite efficiently at constant power output.
It's fairly efficient, compact, relatively quiet and simple to build.

The electricity could be stored in fewer batteries and/or supercapacitors. The
electricity from these would then power the wheels.

~~~
markvdb
A stirling powered hybrid car seems to be a popular idea, but not taking off:

\- [https://www.digitaltrends.com/cars/stirling-hybrid-
engine/](https://www.digitaltrends.com/cars/stirling-hybrid-engine/) \-
[https://www.youtube.com/watch?v=ehWbFoMfmMo](https://www.youtube.com/watch?v=ehWbFoMfmMo)
\- [https://hackaday.com/2008/11/09/dean-kamens-stirling-
engine-...](https://hackaday.com/2008/11/09/dean-kamens-stirling-engine-car/)

