Stirling engines for the third world

[bptdude___2569]

and now, back to the theorists.

lots of people call many variations Stirling engines. if a purist things the whole world has gone mad and they are all wrong and have strayed from the absolute pure and true, well, who knows. but the notions of a sealed fluid machine that works by having a hot end, a cold end, and a cycle of expansion and compression seems to unite people to at least have a common term for their favorite underdog technology.

Rev Stirling devised the regenerator, something that soaks up the heat when it is coming from the hot end to the cold side, and gives it back to the cold stuff on its way back to the hot side, for the purpose of saving fuel. Modern people have fancy names for why and efficiency numbers. Stirling was trying to save fuel, for reasons never known for sure.

Another way to improve the Stirling action is to either make the hot end hotter and the cold end colder. I see many power Stirling engine designs that seem to ignore the cold side. The st-5 is a notorious example. A few cooling fins exposed to the air doesn't seem to me to really be a strong effort. Also, burning husk in a piece of junk wood box really doesn't seem a serious attempt to fire up the hot end. If the ST-5 needs improvement, heating the hot and cooling the cold seems a lot more bang for the buck than reinventing the regenerator.

I was chatting with my teenage son about this stuff last night. We have a coffee cup Stirling engine. As I was trying to explain theory of regenerator, he wanted to show me something. He put the thing on an ice pack, then took the hair dryer and heated the top side. The thing went so fast, it flew apart, with the propeller flying across the kitchen. Everybody broke out laughing, except him, who thought he was in trouble. Naw, he wasn't, I laughed too, and we put the thing back together pretty easy. The point was made quite clear to me.

Lets say I have some Stirling engine and I want to use it for power production, for me, at my home, given my unique conditions. There are things that I can do to increase the effectiveness, hopefully to make it practical. The purist would say these things are very complicated and take from the efficiency. But that is really really true, or doesn't have to be.

Like, Rev Stirling, I want to get the most from my fuel, which we will say is firewood in my case. There are things I can do to make the hotter end hotter. Let's say I'm using a wood stove to burn the wood. If I put my wood stove inside a kiln, with the hot end of the Stirling coming right into the kiln and into the stove, this thing will heat up much more just from physical construction.

Now, let's say I take a separate little Stirling I buy, that runs off the stove heat to spin a fan, and use it to force air into the stove, turning it into a wood furnace. I have plenty of heat to spare, and I don't have to "rob" my main Stirling to do things to help it. This is also an example of feedback I was also trying to explain to my son. As the little Stirling fan force blows air into the furnace, the furnace gets even hotter, making the little Stirling spin even faster, making the furnace even hotter, up to the limit of the wood capacity or the stove goes meltdown on me.

Here is the link to the little stove fan for my theoretical example:
http://www.kk.org/cooltools/archives/001525.php

Also, we know at home, in my real wood furnace, that we don't want truly seasoned wood, and some wood burns hotter than others. If I use harder wood and let it dry completely and put that in my furnace, the heat becomes too much too easily. So, I could make my theoretical Stirling furnace use the hottest driest wood fuel. The would increase heat quite a bit.

Now, on the cold side, I buy a second little stove-top Stirling fan, and use it to slowly pump the very very cold water from the well under the house up to the bathtub-from-the-junkyard I am using for my water cooling tank on the cold end of the Stirling, instead of air cooled fins. The tub is allowed to drain out the drain hole, and back into the ground through the septic system, which will never affect the temperature in the well.

As you can see, what I am doing is "cheating" on the Stirling cycle, and trying to turbo charge the process.

None of this is my "big idea", that has to do with a regenerator. But, I think you can see where this is going.

A purist would cry foul, and throw me out of the Stirling engine genius contest.

But, if people in real need in parts of the world where unconventional energy sources would save the day, people who have real expertise in such machines should encourage them to do anything practical and some things even silly, if it would help them to help themselves. Solutions can be unique to situations to overcome the perceived doom-to-failure belief, when a little creative Yankee inspiration might just push the heat engine theory over the mark.

- Joe

[hislop]

Todd,

Here we go again! I agree that alphas, betas and gammas plus the acoustic version all the conform to my criteria for a Stirling engine (I’ll stretch a point for the acoustic in which the piston takes the form of a diaphragm); also that there can be LTD and HTD versions of any of them. The rotary I am not so sure about – it depends on the nature of the cycle. If the charge gas cycle takes the reversing, unsteady state form normally provided by reciprocating motion, then I will go along with it being a Stirling cycle – if not, not. Where I disagree is on the role of the regenerator. All the formats you mention have, and crucially depend on, a regenerator. Without it, the laws of thermodynamics tell you loud and clear that in the Stirling cycle as globally understood you will get little or no net power output and horrendously low efficiency. That is why the hot air engine was never a commercial item competing with the steam engine until Stirling gave it a new cycle by inventing the regenerator. If you think you have a heat engine that produces useful power at reasonable efficiency without a regenerator then you do not have a Stirling engine.

Why go on about this at great length? For the simple reason that if you want investment in your engine for developing countries, and have found a solution that works, it is counterproductive to call it a better Stirling engine if, in fact, it is something different. And the reason for that is also simple: investors are not stupid – they can easily look up the dismal history of 70 years of attempts to commercialise the Stirling, and will ask – so what’s different? Their engineering advisers will quickly distinguish between a hot air engine (no pun intended) that is a Stirling without a regenerator and much worse than the Stirling, and a completely new idea which might actually do the job and be investable. I want to avoid failure and disillusion on the part of enthusiasts for developing world solutions. On this issue, I was interested to note that your investable package included plans for a production facility: no investor I know would consider such issues unless and until there was at the very least a working prototype.

On your third paragraph, the answer is simple. Assuming you have no mechanical, thermodynamic or gas friction losses, you would indeed be describing the ideal Stirling cycle, but for one point. That point is that your compression ratio is ratio is infinite, which is what allows you to eliminate the regenerator. But, first, you no longer have a Stirling cycle, and, second, the ideal Stirling cycle cannot be achieved – we can only go as far as the inevitable losses and cost constraints on design etc will allow us. So, have you got a heat engine with a different cycle (not a Stirling) that does the job that everyone agrees needs doing? I cannot tell from what you have provided, and I understand that confidentiality may prevent you from disclosing more. Have you built a prototype – even a small one? If so, we can all look forward to publication of the results of independent tests. If not, it would help all of us looking for solutions if you could do so, but please, do not further confuse discussion by calling it a Stirling engine if it is not a Stirling engine!

Drummond

[hislop]

To Joe,

Rest assured, no purist (I assume you are referring to me!) would disagree with what you are doing - indeed, it is common practice to get the hot end as hot as possible and the cold end as cold as possible - all you are doing is increasing the Carnot (theoretical) efficiency. What the purist will say is that if you ask an engine to operate between higher hot end and lower cold end temperatures than it was designed for, you should probably change the dimensions of the heat exchangers and the regenerator to get the maximum output and efficiency from your new conditions. But if your original design has a bit of leeway on these things, you will certainly see improvements in output, and almost certainly improvements in efficiency as well (also provided the power needed for your fans does not exceed the extra power from the engine). Good luck!

Drummond

[dai.davies]

Just a quick note - thanks for all the comments posted (and sent directly) - I haven’t disappeared in fact I sent a comprehensive description of the relevant (to me) factors brought up so far and a bulleted response to some of the direct points (5 pages)2 day ago... seems like it never arrived as I think that bill gates chose that very moment to send urgent updates and while I was making a well deserved coffee my machine restarted.... file is gone message didn’t arrive and I am thinking of changing to Linux!!

I did think at one point that the message had been moderated as it did contain a lot of non-technical and specific geo-social background but the title of the thread suggests that the "third world" discussions are entirely relevant and that arguably the "application" is equally as important as the "engineering"...

Case in point... the wind up radio... Trevor Bayliss arguably did not invent the WUR he rediscovered the technology and applied it to generating electricity... of course the output was limited so the radio was the only real practical application... but it didn’t fly... we had batteries so what was the point... I believe it took 20 years for the idea to catch on and it may never have done so without bad circumstance and good luck... HIV/AIDS and Nelson Mandela... Mandela heard a radio interview with Bayliss and recognised that access to radio wasn’t a luxury... it was and still is vital for communication and information dissemination. The WUR provided the means to supply health education to the remotest areas and incidentally by emphasising this social worth also largely solved the problem of affordability. Buy one (here) get one free (there)

Am not suggesting a direct correlation but just pointing out that in some instances commerciality/efficiency/cost is a function of application rather than engineering...?

I will adress the various comments individually but for now I can offer some general explanations…

Why the Niger Delta? Demographics/Economics/Politics/Culture/Tradition/Geography. Short version… River Deltas (worldwide) are flat and fertile and lots of water so lots of people… Niger Delta provides enough oil to make Nigeria the 6th largest oil economy in the world (not poor)… 50 years of corrupt government (ably assisted by the Oil Companies)… Lack of awareness of root causes and potential solutions that are familiar in a developed society… historical acceptance of fate and lack of knowledge of alternatives… Climate and topography makes easy solutions such as wind, solar and hydro less attractive.

There is a deeper problem of deliberate underdevelopment to facilitate the exploitations but that’s not a short version… the fact is that due to all of the above:

“There is no power or running water in Oloibiri, [Bayelsa State] the town that hosted Nigeria's first oil well and few visible signs of progress after five decades of oil production. The clinic and hospital, built by the oil giant Shell's Nigerian subsidiary, stands empty for lack of staff and equipment.” (Source; Africa confidential Vol 46 Number 7, 1st April 2005)

Logic doesn’t apply here but there is logic to the needs… the following was written as a complaint about loss of power but ideally describes its value to the remote communities:

DARKNESS: A Free Gift…

Gifts often bring joy to the recipient! It is also a common believe that a gift should not be rejected. But must one receive any and all gifts without complaint. The Eastern Obolo people have learnt to receive darkness without grumbling. They have adapted to a nocturnal way of living.

The Electrical installations in the communities were a welcomed development in the area. The people had celebrated the dawn of electricity in their locality. They had sang praises of their cables and transformers. In the late 90’s, the three ‘urban’ communities, Iko Town, Okorongakmboho and Okoroette, were as busy as Abuja at nights. The children were always gathered, at the few houses with television sets, to watch movies. The towns were full of hustling and bustling. But gradually the story has changed. The communities are perpetually thrown into darkness. Often times than not, there might be epileptic power supply. The day’s businesses like Hair saloon, Movie house, Bars, Restaurant and other electrically sustained businesses are distressed. The Nights are not even different. The old men have reverted to their ancient habit of sitting out for cool air from the Atlantic. The youth roam the towns far into the nights and the children play out late into the night. Everyone finds a means of being exhausted before retiring to bed in other to avoid heat.

Well since there is nothing else for them to do, the Eastern Obolo people have towed the traditional line by accepting the ‘Free Darkness’ from the National Electric Power Authority (N.E.P.A), without complaints. They take it as their fate.
But a question arises in our heart .Must we always be resigned to fate? Can’t we find away out of the maze? Is there ever a solution to the unending problem with N.E.P.A.? If there is, what can it be?
.
SAYS IT ALL FOR ME

Dai

[dai.davies]

Well it seems that I have been moderated... just had this in.

Please restrain yourself from adding extraneous remarks
of geo/political, off-topic and/or non-technical remarks.
The BBS Forums at are to be used
to discuss Stirling, and Hot Air,s engines.

W. S. Hornbaker

Apologies if I have offended anyone but the corresponder doesn’t make it clear exactly what where and how but I plead guilty to all.
As I pointed out the thread is entitled "Stirling engines for the third world" and in my view it is therefore either necessary to discuss the particular conditions that apply there or there is little point to the thread - there are several other appropriate options in "power producing" to explore the non third world arguments.

Geo/political context is essential to define appropriateness and explore market potentials and I believe may be the key to providing the interest and funding to develop a useful sterling application. Unless this forum serves merely to allow endless discussions of theoretical improvement to a machine that is destined to remain either a toy or a museum piece then I suggest that non-technical practical application input is to be welcomed.

The off topic accusation may be partially valid for those that do not see why I used the references to show circumstance and need but I thought it useful to point out some of the mistaken perceptions and erroneous comments made in earlier post without causing offence.

I first wrote on this thread several years ago, I returned to find if any progress had been made. I may return in several years time to check if its moderators still merely want a talk shop and thanks to the advice and information supplied by the members themselves it could be that I will have some technical on-topic inputs from actual working sterlings from the field.

I am grateful to those who appreciated my efforts and you are welcome to email me with further information anytime. dai.davies@nddi.org

Thanks and best wishes to all

Dai

PS a comment was made earlier on waste management through energy generation - an excellent idea and I am advising the United Nation Environment Programme on just such a scheme planned for Liberia. Would like to discuss ideas with the contributor but won’t go into detail as it may be off topic here;-)

[stan.hornbaker]

This is the Power Producing Stirling Engine Forum and as such is intended for discussing Stirling engines.

Pros and cons of various fuels as pertain to their operation are acceptable. Discussions/dissertations/of geo-political/social-economic/racial-issues are out of place and will be considered Off Topic and subject to removal of the entire post regardless of any other material therein.

If you stuck your foot in it be carefull to avoid a second mis-step.

[bptdude___2569]

Hey Dai,

Since you talked about social issues, which hopefully you can understand the people who run this thing don't want to "get their foot stuck in it", it has been very quiet.
But, I still have been digging and thinking. If you want to read more of my ramblings, I will be moving over to the area that discusses the thermoacoustic engine. It is a very exciting concept that is still a Stirling engine and holds great promise.

More good news, is I have an authoritative answer for your problem. The clever little elves at Los Alamos National Labs who first came up with the first true thermoacoustic Stirling for an exotic super long range spacecraft have been busy transforming the idea into something to help the poorer people of the world who live by open fire just to sustain life. This is a device with no moving parts if you just want heating and cooling and very simple dynamo to convert output sound energy into electricity. I am very interested in getting my hands on one of these for use here in a nice developed country, like my backyard and home running off my wood furnace.

This is all current information, with updates on the project expected to be released in early to mid 2008. Here are the links.

http://www.score.uk.com/research/default.aspx

http://peswiki.com/index.php/Directory:Acoustic_Generator:SCORE:Stove_for_Cooking,_Refrigeration_and_Electricity

http://research.nottingham.ac.uk/NewsReviews/newsDisplay.aspx?id=334

http://www.mace.manchester.ac.uk/postgraduate/research/funding/studentships/jaworski_further_particulars.pdf

http://blogs.zdnet.com/emergingtech/?p=574

http://www.qmul.ac.uk/research/newsrelease.php?news_id=558

http://www.physorg.com/news98035683.html


I do believe this is the magic silver bullet you have been asking for and resolves this thread "Stirling engines for the third world"

Best of luck with it!

Cheer,
Joe

[wall43211]

It is certainly important to have relative inexpensive energy alternate for the 3rd world. However I think it is even more important to have them in place here in the developed world. This will result in reduction in dependence on fossil fuel from volatile regions and thus making the world a safer place.

Here in Canada I can have an approx. 40 to 50 centigrade difference between to two ends very inexpensively throughout the year. That can be done by solar water heater giving me a constant 40 to 60c degree water temperature and the atmosphere temperature ranging from -10 to 20c (cold water assisted during summer months)on the other colder end.

This much temperature difference does not exactly meet Joe's Icepack/Hairdryer experiment but certainly worth something in terms of Stirling Technology.

Let us assume that space is not an issue and there is a contact 40-50c difference between to cold and warm end, can a hypothetical system be developed for 5KWh energy generation. I believe if some thing can be developed at a cost of $20k it can be sold to masses specially new house builders.

John

[gurmitchauhan]

I have developed a Low Temperature Heat Engine, it operates at 70-80 degrees celsius only. I made a prototype which turns a 2 KW DC Permanent Magnet Generator. It is very compact and can be mounted on rooftop. Heat source could be solar or industrial waste heat.
I am trying to upscale it to 5 KW, I hope to succeed.
If I succeed it will be the answer for Global Warming and Climate Change.
Because of it's Low operational temperature, it can operate at night through solar ponds and does not need a hybrid system.
Recently, I also won Lockheed Martin Innovation award 2008 for this breakthrough technology : http://www.indiainnovates.in/Medalists2008.pdf

[bptdude___2569]

Gurmit,

Perhaps you are "the one" to break the practical barrier. I went to your link, and hope you don't mind if I copy the details here. The following is taken from your link.

Some purists may want to debate if this is truly a Stirling. I personally do not care, as long as it works, and I can get one going.

Huge kudos to you, for your award!

- Joe


"Technology No. 314
Technology Name Solar Thermal Engine
Sector Energy
Technology Description:
The technology is a Solar Thermal Engine that can covert solar heat directly into
mechanical energy to generate electricity. The engine is a simple compact device
with few moving parts for harnessing solar energy to heat. It operates directly upon
the application of heat to a portion of the SMA (Nitinol) wire chain. Its purpose is to
convert heat energy to useful work while executing a cycle by extracting the tensile
energy of straight nitinol wire. The device can easily be mounted on rooftop and can
meet the electricity needs of household."