Talk:Stirling engine

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Help with this template Comments: edit – history – watch – refresh I'd like to see more support for the efficiency figures quoted in the article (50%-80%). What engine configuration is used, what are the materials etc. A few references to the technical papers would suffice.

[edit] Stirling Cycle

The article needs an explanation of the Stirling cycle, specifically: isothermal compression and expansion, and constant-volume heat transfer. A Stirling cycle is NOT a Carnot cycle! Someone put this in the article, and I had to take it out because it's incorrect. Mikiemike 21:44, 24 October 2006 (UTC)

I wonder if Stirling technology could be an answer to solar energy production, at least on a small scale. Since a direct solar -> electrcity solar cell is pretty inefficient (maybe 20% now, was only 10% for a long time), I wonder if a better approach might be to use a solar collector to heat water in a closed system, apply it to a stirling engine that then turns a generator. Since the solar collector itself is about 80% or more efficient, and the stirling engine is 50%, and the generator perhaps 85%, the overall losses are much less. Anyone think this idea has merit? I'm not sure how big a Stirling engine needs to be to be useful here, but I can envisage a (trans)portable power supply unit that would be self-contained and be great for e.g. the African or Australian bush. Graham 10:13, 5 Aug 2004 (UTC)

Check out http://www.stirlingenergy.com to see someone who is doing essentially what you've just suggested. Interesting stuff. Don't know how competative it is. --Flatline 18:04, 2005 Jun 1 (UTC)

0.8 * 0.5 * 0.85 = 0.34. 34% efficiency overall. I'm actually looking into using the excessively-hot solar collector water to drive a sterling cycle cooled by a geothermal pump. I might write this into a book too. --John Moser 23:23, 13 December 2006 (UTC)

Ive seen a demonstration engine on the internet with a solar -> electricity efficiency of 30% its possible but... - Zephyris _Talk 13:09, 24 February 2007 (UTC)

[edit] Regenerator is essential component of a Stirling Engine

From countless references including this history of the Stirling Engine:

"The Rev'd Robert Stirling applied for the first of his patents for this engine and the 'Economiser' in 1816, a few months after being appointed as a minister in the Church of Scotland at age 25. Others such as Sir. George Caley had devised air engines previous to this time (c. 1807) and other devices called air engines were known as early as 1699. The 'Economiser', or regenerator, has come to be recognized as a most important portion of the patent of 1816. These innovations were even more remarkable in light of the fact that they preceeded the birth of thermodynamics and the writing of M. Sadi Carnot by some 40 years!"

Many variants of hot air engines existed before the Stirling Engine. They are not all Stirling Engines.

Paul Beardsell 21:21, 5 Aug 2004 (UTC)

[edit] External links inflation

Some authors seem to have a misunderstanding about our linking policy. The Wikipedia is not a web directory. It would be most helpfull, if someone knowledgeable in the field would expend some time distilling the links to the most important ones only. --Pjacobi 10:46, 2005 Jan 16 (UTC)

Can you supply a link to the linking policy, please? Paul Beardsell 11:07, 16 Jan 2005 (UTC)

Sorry, it seems I was overly bold in my previous comment. Besides the sparse mentioning in Wikipedia:What Wikipedia is not, I wasn't able to find a written policy. So in contrast to the German Wikipedia, which seems to be more formalistic in this area, the handling here relies on precedent on discussion. --Pjacobi 22:39, 2005 Jan 16 (UTC)

But I agree you with you: There should be a policy. If in the "external links" section we just cut'n'paste everything returned by Google then we might as well just have one link which will always be up to date: Google search for "stirling engine". Paul Beardsell 23:06, 16 Jan 2005 (UTC)

Now I've found some bits and pieces:

• Wikipedia:External links very terse
• Wikipedia:External links/temp a proposed policy, but process seems to stopped
• non binding advice from meta: m:When should I link externally

Pjacobi 23:48, 2005 Jan 16 (UTC)

[edit] Cycle description

I'm a little unhappy with the description of the Stirling cycle in the opening paragraph - if some mechanical engineering type doesn't fix this, I may be forced to be bold. I'll have to see the "thermodynamics" article and the Carnot articles and see if there's a discussion of other thermodynamic cycles that could be referenced here. I took out the "hot air engine" link because it linked back to this article. I've tried to put back in some of the disadvantages in earlier version of the article, since they are important. There were a couple of odd-looking sentences that I zapped. And I agree, way too many external links...someone with high speed Net connection should do some pruning. --Wtshymanski 17:05, 24 Mar 2005 (UTC)

[edit] Thermoacoustics

One of the most exciting stirling applications (in my opinion, anyway) is thermoacoustics. The lack of moving parts and the potential for miniaturization are both pretty important...why no links or other mention on this site?--Joel 20:41, 9 May 2005 (UTC)

Be bold and put in what you think is appropriate. --Wtshymanski 21:20, 9 May 2005 (UTC)

---

I fail to see how the thermoacoustics article is related to Stirling cycle anything. (Remember, not all heat cycles are Stirling Cycles)

-- User:Nahaj 28aug2005

The concept of the external combustion engine with sealed internal gas is becoming generally accepted as the description of a Stirling engine. Thermoacoustics is simply running a very specialized Stirling engine backwards. The world has so little awareness of the Stirling engine, which I don't understand. Let's not split hairs on the topic and make it more difficult for people to learn about this. The process needs a name. Bptdude 03:08, 30 May 2006 (UTC)

FYI - Here is a cool (sic) sight that gives a a simple explanation of thermoacoustics currently being used by a major corporation, Unilever, in one of their ice cream divisions.

http://www.benjerry.com/assets/flash/our_company/sounds_cool/soundsCool.cfm

It never mentions the term Stirling engine, but I thought you might like it. Bptdude 03:14, 30 May 2006 (UTC)

[edit] Free Piston

Added a comment on the category of Free Piston Stirling Cycle engines, plus a reference. Note that this is one of those areas with a reasonable print publication history, but almost nothing in Google. [I notice a lot of wikipedia reflects Google, and ignores the non-net history of topics]

-- User:Nahaj 28aug 2005

[edit] Configuration

Should Franchot configurations be mentioned specificly under Alpha? [They are the only configuration I'm aware of that allows BOTH pistons to be replaced with a diaphram.]

-- User:Nahaj 28aug2005

[edit] Problems

• While the "engine out" emissions of the engine are quite low, further catalytic cleanup of NOx (oxides of nitrogen) is made challenging because of the lean (excess oxygen) nature of the exhaust.

This isn't a problem of the engine itself but the heat source. Except for vacuum engine (others ?), the engine is closed. For example, how can NOx be generated for dish-stirling engines (solar source) ? I'm not native english speaker then can somebody correct ?

[edit] Topic

When we are talking about stirling engine, Cryocoolers should not be included in the same article. Brief introduction of 1/2 lines is ok but a section should not be there .

[edit] Compression ratio

The gamma stirling description talk of a this configuration having a lower compression ratio , but this measure is only really significant in internal combustion engines. What is the article getting at here? Or is the compression ratio article wrong? Lumos3 09:36, 26 January 2006 (UTC)

The compression and power strokes are comparable in the Stirling and gasoline engines. In one, you heat the compressed air by exposing it to a hot heat-exchanger. In the other you heat the air by burning fuel in it. The article is comparing the Gamma to the Beta configurations. In the Beta, the displacer overlaps the main piston to some extent, so you can have a smaller total volume and a higher compression ratio. I don't see it as a very important distinction. Mackerm 21:19, 26 January 2006 (UTC)

[edit] solar stirling engine

I couldn't add to the top paragraph, so I'm adding a new discussion. There are small models that can be purchased, that have shiny satellite looking dishes that heat the center which drives a Stirling engine.

But the openening paragraph asked about using a solar collector to heat water to feed a Stirling engine. This really shows people's misconception of this type of device, trying to force the square peg into the round hole of what is commonly known.

To use a Stirling engine powered by solar energy to produce energy, you might find a location in Death Valley where 100 feet underground ran a cool water flow. Between these two, you built a mile square extremely simple Stirling machine, that went round and round, driving an electrical power plant.

What is holding up deployment of Stirling engines is more popular perception more than economic, evironmental, or technical issues. The public need only two pieces of information, really. How much of a temperature difference do I need for the current practical Stirling engines? How much does the engine have to cost at current oil prices to pay back an investment in X number of years? When people think of Stirling engines like they think of hydroelectric generators that produce as long as the river keeps flowing, they will begin to get the idea.

Bptdude 08:50, 14 May 2006 (UTC) Joe, bptdude@hotmail.com

I couldn't help but think of how to deploy solar Stirling engines in a desert area. I was surprised to find out there is a project underway to deploy thousands of shiny reflective dish type solar Stirling engines in the American Midwest. I saw the details but didn't record it. I'll find it again and post. The most interesting feature, besides the now financial practicality of energy generation, is that the solar Stirling engines are considered safer for the environment than wind turbines. They don't make the noise and don't kill the birds.

But I was thinking about trying to design a Stirling cycle that could use the intense heat of the day and the very cold of the night to power a large scale Stirling engine, even though the two opposite temperature sources are half a day apart. This kind of Stirling cycle might be very welcome in developing nations that don't have much in the way of other resources.

One interesting use of a solar Stirling engine might be on the surface of the planet Mercury. There, where one side always faces the sun, the line between day and night doesn't move and the temperature difference is intense between the light side and dark side. The distance between the temperature differences can be merely a matter of feet.

Bptdude 03:30, 30 May 2006 (UTC) Is a Stirling Solar Dish new technology?

OK, the following was copied without permission from the site:

http://www.stirlingenergy.com/faq.asp?Type=solar

Somehow I don't think they are going to sue me! *smiles*

[edit] ====begin of cut from web site===

The SES dish system was initially developed by McDonnell-Douglas in the mid 1980's. Since 1998 SES and Boeing have been under contract with the Department of Energy’s Sandia National Laboratories for a Dish-Engine Critical Components (DECC) program.

What geographical areas are best suited for a solar dish farm?

The southwest region of the United States is ideally suited for this. In fact, a solar farm 100 miles by 100 miles could satisfy 100% of the America’s annual electrical needs. Solar technology primarily addresses the peak power demands facing utility companies in the Southwest U.S. and other solar-rich areas.

[edit] ====end of cut from web site===

OK, I have a question. If the above is true, why isn't somebody running for president up on this soapbox?

Bptdude 10:59, 30 May 2006 (UTC)

[edit] Problems with Stirling engines - Discussion

I have moved the following discussion of the problems here from the article. :- Lumos3 04:33, 15 May 2006 (UTC)

{ note: It is pretty much accepted the Stirling engine concept is not fit for automobile engines. Heat exchangers can be as simple as solid materials that don't move. Fuel economy may not be an issue when the advantages of using unlimited but unusual fuel sources that a Stirling engine can make use of. }

{ note: It is assumed Stirling engines are used as constant run, constant speed engines. "Kick Starting" a Stirling engine shouldn't be an issue. }

{ note: again, Stirling engines are meant for constant use, constant speed industrial uses. Variable speed Stirling engines can be considered an optional enhancement. }

{ note: For very small Stirling engines for individual use, this may be true. The answer is simply to not use Hydrogen. Stirling engines run on most gases, including ordinary air. Hydrogen is the best working gas, and a very tiny rate of loss through the walls of the metal itself or through the seals becomes less important with the increased scale of the system. A large Stirling engine, used to manufacture commercial electricity to produce hydrogen as a product to be sold, for use in hydrogen cars, can use a feedback system with an extremely minute amount of hydrogen required to return to the system. }

Good. Though there coud be something in all of this, it goes in so many directions at once that it is not coherent. The constant-speed matter is already covered in the article. -Will Beback 08:29, 15 May 2006 (UTC)

[edit] Cryocoolers and heat pumps

The section Sterling Cryocoolers could use some work... it isn't clear to which parts of the machine are being referrer, or exactly what is being claimed about them. The English is also awkward... missing articles, punctuation, etc. Unsigned Posted by User:24.62.250.91

I have improved the English in this description. I think Cryocoolers and heat pumps should really have their own article, see "Topic" section above . Lumos3 11:45, 10 November 2006 (UTC)

Heat pump has an article; Cryocooler is a page that can't decide if its a stub or a disambiguation page. Please, feel free to be bold and improve any of these pages!

Atlant 14:46, 10 November 2006 (UTC)

[edit] Rotary Stirlings/Article problems

"Notably, some are in hot pursuit of the rotary Stirling engine; the goal is to convert power from the Stirling cycle directly into torque, a similar goal to that of the design of the rotary combustion engine."

This implies that rotary Stirlings don't exist yet, which isn't true. http://www.rotarystirlingengines.com/index.htm's history section documents several, but they vary so much in design that I don't know how to add them into the Configurations section.

This is a major problem with this article, i.e. the apparent POV that Stirling engines use only pistons. The Stirling cycle can use a number of different mechanical configurations besides pistons (though at present it is the most well known and common form). The differentiation needs to be made between the 'Stirling cycle' and the 'Stirling engine' which this article fails to do. While 'Stirling cycle' redirects to this article, they may be worthy of two different articles. Either way, this article needs a lot of work Nodekeeper 17:38, 10 September 2006 (UTC)

If you want, make a section just on the cycle. If it grows to contain enough content independent of the rest of the page, it can be spun off into its own page. Tom Harrison ^Talk 17:45, 10 September 2006 (UTC)

Rotary stirlings are not in service they are patents and models, so they dont need to have equal space to the main article. It would be good to see a section on them though. Lumos3 20:02, 10 September 2006 (UTC)

[edit] Hydrogen vs helium

somebody made a comment about the danger of hydrogen being dangerous. since the gas inside a sterling engine is sealed inside a machine, i suppose it would be a reasonable risk, certainly less dangerous than say a hydrogen internal combustion engine. helium is certainly safer and the expansion / heat properties are close enough.

but if/when sterling engines break out and become wildly popular, in many parts of the world, helium may not be readily available. hydrogen can be manufactured by a simple process using electricity and water. a sterling engine used to drive an electrical generator would then be able to have a tiny feedback process to create replacement hydrogen for the small amount that would leak with all but unnoticeable efficiency loss.

so, there may indeed be a future market for hydrogen based sterling engines.

Bptdude 05:52, 28 September 2006 (UTC)

[edit] Link

• Stirling engines models

[edit] Animation of Stirling Image

I made an animation of the 4 images showing the action of a stirling engine. It's not great. I probably should have made the timing on it longer so it doesn't look so jumpy. Let me know what you think. --SuperCow 23:07, 5 November 2006 (UTC)

That's pretty nice. If we could somehow let readers 'click here to animate this image' and click again to stop, that might be good. I don't know offhand how to do that. Tom Harrison ^Talk 00:02, 6 November 2006 (UTC)

I don't know how to either. Sorry I can't be of much help in that department. --SuperCow 17:16, 10 November 2006 (UTC)

Could you make it so that the cylinder itself does not vibrate? Lumos3

Well, I just stuck those 4 images into a .gif file. To make it so that the cylinder doesn't vibrate, all 4 pictures would just have to be redrawn so that they matched. I can't think of any other way of making it not jumpy. --SuperCow 17:16, 10 November 2006 (UTC)

One of the images is a bit big; scale it down. Move the other layers so they overlap properly (make them 50-80% transparent in GIMP so you can see wtf you're doing), then line that one up. Fit all the layers to canvas size. Save. I'll leave doing it up to you; you'll learn something. --John Moser 23:27, 13 December 2006 (UTC)

Alright, I tried to make it better. Let me know what you think. Still learning how to use GIMP, thanks for the input everyone, especially John Moser. --SuperCow 21:07, 17 January 2007 (UTC)

Nice work. I think it looks even better at 100px . Could you add some intermediate frames so that it runs less jerkily. Lumos3 10:38, 24 January 2007 (UTC)

Yeah, lemme try that. I think it looks better at 100px too --SuperCow 23:53, 24 January 2007 (UTC)

Had a go at it myself, is it right? im no expert... - Zephyris _Talk 21:50, 22 February 2007 (UTC)

[edit] DIY Engines

Wikibooks has a [[1]] book. Add a Stirling cycle engine section to this and do one of the can type, and maybe a metal lathed one. I'd like to build a few myself to test out. --John Moser 23:31, 13 December 2006 (UTC)

• Make a can sterling engine
• Another can engine

[edit] Efficiency Skepticism

Do we have any support for the claim of 50%-80% efficiency? That figure seems very high compared to the other values that I've seen for actual engines. Is the figure based on the theoretical maximum? If so, perhaps we should mention that.

Benjaminbishop 15:27, 29 January 2007 (UTC)

[edit] Leading Image

I have annotated the cut away diagram of a beta type engine and moved this to the head of the article. This has greater explanatory power than the generator set image previously there. I have moved the generator set to juxtapose it to the photo of the desktop engine to show the range in size and power output of the Stirling engine. Lumos3 10:20, 22 February 2007 (UTC)

[edit] Action of an Alpha type Stirling engine

1. Most of the working gas is in contact with the hot cylinder walls , it has been heated and expansion has pushed the hot piston to the top of the cylinder. Expansion continues in the cold cylinder piston, which is 90o behind the hot piston in its cycle, extracting still more work from the hot gas.	2. The gas is now at its maximum volume. The hot cylinder piston begins to move most of the gas into the cold cylinder , where it cools and the pressure drops.	Animated version.
3. Almost all the gas is now in the cold cylinder and cooling continues. The cold piston, powered by flywheel momentum or other piston pairs on the same shaft, compresses the remaining part of the gas.	4. The gas reaches its minimum volume and the hot cylinder piston will now allow it to expand in the hot cylinder where it will be heated once more and drive the hot piston in its power stroke.

Would someone who knows what they are talking about mind filling in an explanation for each step? :) The images may get improved at some point (to show changes in temp/pressure) but I think its time for me to go to bed! - Zephyris _Talk 00:49, 23 February 2007 (UTC)

Again nice work here Zephyris. However you need to show a regenerator in the pipe which is a key componant of the Stirling engine. The animated diagram here shows how it works. http://www.keveney.com/Vstirling.html Its the green box midway along the pipe.

kk, ill add it when i improve the images, unfortunately i have a bit of a crazy week coming up! - Zephyris _Talk 01:18, 26 February 2007 (UTC)

Have added my best go at captions.

I am against showing the Stirling cycle adjacent to one of the engine designs as it is a general concept which applies to all designs. Lumos3 00:30, 26 February 2007 (UTC)

It was not intended to be one of the engine designs - it is an idealised design - although it is based on the alpha for clarity... - Zephyris _Talk 16:40, 26 February 2007 (UTC)

Nice animations! Mikiemike 05:01, 24 February 2007 (UTC)

[edit] Closed cycle steam engines

Closed cycle steam engines do not recycle their working fluid each cycle but through a condenser and boiler which are external to the cylinder and recycling takes many engine cycles. This distinction is important as the Stirling engine is the only form which recycles the gas within the cylinder at each stroke. Lumos3 00:24, 26 February 2007 (UTC)

Lumos3, You make a point, and if you choose to draw your "control-volume" around the cylinder then I suppose you're correct. So, perhaps the real question is: Does an engine consist of just the cylinder and nothing but the cylinder? I think one could make arguments both ways. Anyhow, the way I learned thermo is that the term "open-cycle" means that the working fluid is open to the atmosphere. So when you mention an "open-cycle steam engine", I picture an engine with a large supply of water that is venting steam to the atmosphere. However, if the heat-engine system contains a condensor, and you trace the path of the working fluid (which may pass out of the cylinder), then it is technically a closed-cycle. Whether you agree with it or not, for the sake of the article I think one has to accept the terminology and conventions as they have been defined by the scientific community.

Most people don't know what a Stirling Engine is, so the aim of the article should be to educate the reader on that topic. The first distinction of a Stirling engine is that it is an "external combustion engine". Now, since the most common type of "external combustion engine" is the steam turbine, I think that is the most important comparison. Anyway, the article is about Stirling engines, not steam engines, so this really isn't the proper forum to debate whether the steam engine is an open-cycle or closed-cycle. With all due respect, IMHO, if it's really that important to you, then maybe you should bring the issue to the Steam engine page. Mikiemike 18:47, 13 March 2007 (UTC)

[edit] Animated images

We now seem to have two offerings of good animated diagrams to choose from, those offered by User:Zephyris and those by User:Van helsing . Both of these are excellent pieces of graphics and it is very hard to choose one over the other. I propose that the sectional diagrams are used to explain the stages in the cycle and the perspective diagram is used to show the animation. I believe this gives the reader the greatest explanatory power, which is what should be our main criteria in building an encyclopedia. Lumos3 21:40, 11 March 2007 (UTC)

Agree, though the perspective one is currently a monster in file size, so I deleted it temporarily until I find a way to reduce the file size. The problem is that the MediaWiki software (actually ImageMagick) seems very arbitrary on if it will scale down certain animated GIFs yes or not. Purges, clear caches and patience don’t seem to help with this version. --Van helsing 09:44, 12 March 2007 (UTC)

[edit] Rhombic-Drive Beta-Stirling Image

Note the port at the top of the cylinder, which was probably intended to connect to a heater-regenerator-cooler unit, as is usually done in a SE. I admit, it is a very pretty drawing of a rhombic-drive linkage, but unfortunately the drawing does not adequately represent a SE, because it lacks heat-exchanger and a regenerator which are the most important parts of a SE. Since this drawing is missing critical engine components, it is misleading to the reader. The problem with this image, is that it serves to perpetuate the myth that a SE does not require a large surface area for heat transfer as is provided by internal heat-exchangers. For this engine to run as it is shown, without internal heat-exchangers, the requisite surface-area/volume ratio would necessitate that the cylinder bore be limited to a fraction of an inch, yet there is no indication of engine size in either the image or caption. Further to the point, the unique LTD-engine, which is usually the only type of SE that uses a displacer without a regenerator, always has a displacer that is shaped optimally as a wide flat disk. Again, this is done to maximize the surface-area to volume ratio needed for good heat transfer, and is essential to make the engine run.

This problem is made worse by the refusal of one or more editors to conceed that no regenerator is present in the image. The edit-war needs to end, and at the very least this issue needs to be resolved by explaining the omission in the caption, or better yet, the image should be replaced with an image that more accurately depicts a realistic, full-functioning SE. The SE is a "heat-engine", so it needs heat to run. Mikiemike 19:41, 13 March 2007 (UTC)

Please link to an example of the type of diagram you mean anywhere on the internet. The diagram used is consistant with others on all the web sites I have come across. The port at the top of the cylinder is probably used to replenish the working gas as it seeps past the piston seals. The diagram is also consistant with those used for internal combustion and steam engines which also dont show ancillary heat exchangers, boilers, dynamoes, batteries etc. Lumos3 22:15, 13 March 2007 (UTC)

[edit] Gamma Stirling animated image

It would be good to have an animation of the Gamma configuration in the same style as the other images. There is an example of how the gamma works here [2] . Lumos3 22:11, 27 March 2007 (UTC)