Disaster

There's a good reason this technology has been bypassed, and it isn't due to a conspiracy by the evil oil companies. Stirling engines don't *appear* complex, but there are some crucial issues which must be addressed if they are to be more than desktop models barely able to turn themselves over.

Efficiency cannot be ignored when it is so terribly low that it would require a cord of wood to produce 150 watt-hours of electricity. Of course, Stirlings can be more efficient than that. But to get reasonable efficiency (and size), you need to use a working fluid other than atmospheric pressure air. Typically, you need to use helium at several hundred PSI.

That in turn requires very tight tolerances and provides a terrible sealing problem (helium will find the smallest leak). The shaft seal is typically the weakest point. This problem is so severe that you don't want to bring a shaft outside of the engine. The best way to design a low power Stirling generator is to incorporate the generator with the engine, all inside a hermetically sealed housing (like a home refrigerator motor/compressor). Special metal/glass seals can then bring the wires to the outside.

Now you have the problem of efficiently conducting heat into and out of the engine. Heat pipe technology can work for this, but it isn't simple or obvious, and provides more potential leakage points.

This isn't something most HSMs are willing to tackle (though I don't doubt that some here are capable of pulling it off). It is really a job for a well qualified industrial design team with manufacturing experience with high pressure helium systems, heat pipe technology, and knowledge of high reliability generator systems (you don't want to have to cut into the assembly to repair it).

Gary

Anyone who wants to build Stirling cycle engines and put them in vehicles is pretty much free to do, and have been free for the past century or more.

So?

Anyone who thinks there's some kind of Vast Conspiracy to Block Stirling Engines, a conspiracy which includes GM, Renault, Volvo, Ford, Kia, Citroen, Daimler, Chrysler, dozens of others, and even more in the past, is smoking rope.

For anyone who claims Stirling engines are cheap to build and would set the market on fire, what are you waiting for?

Oh, I see...you are clerks at Wal-Mart who fantasize about Evil Conspiracies.

--Tim May

VERY large grin!!

Harold

On Tue, 21 Oct 2003 03:11:58 -0400, Gary Coffman followed up with:

I appreciate your detailed reply, Gary, but I'd like to address some foundation issues here.

Just to clarify, my use of the word "bypassed" was not intended to suggest ANY kind of conspiracy by ANY entity. I can honestly say it never even crossed my mind. In retrospect I probably should have used the word "forgotten." Nevertheless, although the word "bypassed" arguably was ill chosen, it doesn't necessarily =exclude= "market forces" as reasons for disuse.

Although we often question historical developments, not everyone who follows is a conspiracy theorist. Regrettably, there is no USENET newsgroup for emergency preparedness and disaster response, which is my real interest and would have been my first choice for a crosspost with (only =possibly= to be followed by , because of its abysmal S/N ratio).

Based on what I've uncovered about some of the early applications for Stirling engines, I suspect the above characterization may evidence a bit of hyperbole, but I'll accept it on its face for the purpose of discussion.

I live on the northern fringe of the US "solar triangle," as identified in legacy EPRI studies. The triangle has the highest solar insolation of virtually any area in the US, and the melanoma rate parallels this data. On a clear, calm summer day the influx is about

1.2 KW/m^2. Aside from occasional minor capture with some portable PV panels that I have, essentially this entire donation currently goes unused. (In hot weather I even "import" energy to deal with this influx and improve my comfort.) If the Stirling engine for a small, portable genset was only TWO percent efficient on solar input alone, it would still diversify my field power sources and constitute a net overall improvement. My apologies if these details were lost in thread [mis]management.

In the broader context of interests, though, cost effectiveness and efficiency aren't always the parameters that drive decision making. Other priorities often take precedence. It is a longstanding dictum to be able to adapt. This orientation readily accepts the use of "forgotten" technologies, tools and techniques. Expedient or suboptimal solutions to perceived needs and wants are commonplace. They aren't necessarily anyone's first choices, or permanent solutions, but they have their justifications nontheless.

Finally, including in the crossposting (though intermittently) was intended mainly to discover possible common interest in building prototypes or doing short production runs of practical projects. Not wanting to clutter with offtopic traffic, I would have pursued discussion of any specialized development or manufacturing issues of Stirling engines in more appropriate newsgroups, because these aspects are not consistent with the charter, as seen at URL .

In closing, I note that although the thrust was not toward pursuit of bleeding edge Stirling designs, I relearned some valuable lessons concerning communication, and for that I thank you.

Lee_K [returning to shortly]

You could just have a haystack of square bales. When you want to run the genny just stack walls of hay bales around the noise.

Another possibility is to use magnetic coupling in place of a shaft seal. That is what the nuclear subs do for their reactor pumps.

Possibly my news host is running slow again, because so far I haven't seen the stimuli in this thread for ANY of the various aspersions concerning: conspiracies; "evil oil"; automotive applications for Stirling engines; =intended= applications outside of a small genset; =possible= applications outside of a well pump or machine shop overhead line shaft (and an earlier reference to a proposal by others to use Stirlings in light aircraft); cheapness; cost effectiveness; mass production; WalMart or anything remotely related. Perhaps the missing references eventually will appear. (Doubtless it will be a magical moment.)

In the meantime, since I can't ascertain the bases for your comments, the target of your sarcasm is likewise unclear. However, I'm following up because your article quoted previous posts from only Gary Coffman and myself, and Gary disclaimed "conspiracy by the evil oil companies," so there remains a hint that you were obliquely sniping at me. If this delivery was not your intent, then in the interest of engendering more constructive newsgroup traffic, kindly take the time to more accurately attribute and articulate your thoughts in future posts.

Lee_K [Setting the Followup header to alone for the sake of closure]

Hi folks, just a little humor, I read once about a guy in Oz, probably between the wars, who used to run the cinema in a little country town, found his generator was a bit noisy (possibly petrol driven) so buried a 55 gallon drum filled with rocks as a muffler, when the engine over revved the ignition was cut & on the next hot stroke the unburned fuel in the drum ignited, some of the rocks went a hundred yards. Added some realism to the film. Cheers, Ian Sutherland.

Forgotten isn't the term I'd use for it either, unless you mean that after an engineer takes a hard look at it, he says "Forget it!" There are much better ways to get a couple hundred watts of electric power from a low grade heat source.

If what you want is silent operation from a low grade heat source, then I'd recommend you look at Peltier junction devices, or even thermopiles. They're well understood, have no moving parts, an expected MTBF measured in the hundreds of thousands of hours of operation, and have been deployed at power levels up to 1 kW commercially. You can even make one cheaply at home from parts salvaged from Coleman coolers.

Gary

Without taking the time to go back and read all of the articles, the current thread map looks like this (using strn as a newsreader):

====================================================================== [1] Disaster [2] Disaster - Mufflers & quiet [3] Disaster - Stirling Engine?

(1)+-(1)+-(1)--(2)+-(2)+-(2) | | | \-(2) | | |-(2)--(2)--(2)+-(2) | | | \-(2)--(2)+-(2) | | | \-(2)--(2)--(2) | | |-(2) | | \-(2)--(2) | \-(1)--(1) |-( )--(1) |-(1) |-(1)+-(1) | |-(1)--(1)+-(1)--(1) | | \-(1) | \-(1)--(1) |-(1)+-(1)+-(1) | | |-(1) | | |-(1)--(1)+-(1)--(1)+-(1) | | | | \-(1)+-(1) | | | | \-(1)--(1) | | | \-(1) | | \-(1) | |-(3) | \-(1)+-(1) | \-(1) \-( )+-(1) \-( )--( )--(1)--(1)+-(1) |-(1)--(1)--(1) \-( )--(1)+-(1)+-(1) | \-(1)

Thanks, but the complaint was in the second paragraph. It related to article , in which Tim May quoted me, then added sarcastic comments on things that I had never mentioned or even suggested anywhere in this entire thread from the very outset, in either newsgroup. Whether intended or not, the effect was to obliquely and baselessly identify me as the stimulus for his derision, if not the target of it. I politely asked him to be more scrupulous about attribution and articulating his thoughts - that's all.

Lee_K

There used to be a least one company in New Zealand that makes sterling powered Gen-sets (and IIRC refrigeration units ??????), for boats and rural use. IIRC these units were self-contained, including an internal fuel tank. They used a propane or petroleum heater for a heat source, and in addition to providing electricity, they provided enough hot water, to supply a boat or small homes daily needs. Not very cost effective, but silent.

It was evaluated by the US Military but there were no unique requirements that it fit that were not met by other technology.