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2nd "law" violations => Heat to electric energy conversion => Topic started by: Groundloop on February 29, 2008, 01:04:12 PM

Title: Closed chamber Stirling engine generator.
Post by: Groundloop on February 29, 2008, 01:04:12 PM
Hi All,

I have got an idea on how to convert solar heat to electricity. My proposal is to use an completely closed cycle Stirling engine and convert the solar heat direct to electricity by the use of a powerfull Neo magnet and a pickup coil. The Stirling engine has just one moving part. The engine is cooled by water and the hot water byproduct can be used to heat your home or for hot water usage. The Stirling engine can use other gasses than air. Hydrogen, Helium, Nitrogen is some. The solar energy can be collected by a parabolic disk or by Fresnel lens.

I have not build this motor generator and probably never will because I lack the tools and skills to do that. In any case, this is open source information. I hope that someone with the right tools, materials and skills can take this idea into reality.

Groundloop2003.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on February 29, 2008, 04:36:27 PM
All,

At mid day in the summer the Sun will provide approx. 800 Watt of energy pr. square meter area.
A solar panel of approx. a square meter area will give you approx. 100 Watt of energy. An Stirling
engine is very effective. Maybe it is possible to convert more of the 800 Watt to electricity when we
compare the area exposed to the Sun.  What do you think?

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on February 29, 2008, 04:36:55 PM
Hi Groundloop,

Stirling usually needs two pistons. One piston variation can be imagined, though.
However, in the variant proposed I think the piston will barely move at best (very small amplitude and tiny motive force) and if it does move at all it will end stuck to the right (cold) side. I can?t see why it would leave that position once getting there.

I?ve also got excited over the time by the idea of solar-heat-electricity but shortly afterward I realized that the efficiency of a thermodynamic engine will be limited to approx. 10% (max. Carnot) considering a reasonable temperature difference of 30Celsius that can be achieved. 10% of >1Kw/sqm of solar energy may not sound too bad on paper but it actually poses a lot of technical challenges in practice because of the cumbersome cylinder and pistons which will weight proportionally to their size (about 1sqm for the displacer), thus generating a lot of friction especially also when considering the sealing requirements for the main piston. Also because at smaller temperature gradients the heat transfer is much slower, any engine of this kind will have a very low RPM ? another nightmare to be overcome.

I?ve seen enough movies of various Sterling engines but not a single one to run on solar energy, although many seemed to happily work above a cup of coffee. I wonder why.

Anyway, I am open for contributing to a thoroughly debate regarding solar-heat-electricity conversion if enough interest exists. After all, solar energy is quite abundant and at about 5USD/W in photovoltaic panels there is at least a theoretical chance to come with something cheaper.

Cheers,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on February 29, 2008, 05:16:24 PM
@tinu,

First, you havent seen much I bellive.  ;D

http://www.sandia.gov/news/resources/releases/2004/renew-energy-batt/Stirling.html

The difference with my design is that there is just ONE moving part.

Next, the temprature difference will be some 1000 Degrees or more in a solar powered Stirling.
The cold side will be approx 90 Degrees Centigrade. (Water cooling, remember.)

A closed cycle Stirling with one piston is no problem to manufacture.


Before you "doom" a project please get some information first!

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on February 29, 2008, 05:41:37 PM
@ Groundloop,

Don?t be that sensitive, now!
Figures are welcome. One moving part is great but it won?t make it workable more than 1RPD (rotation per day) or 1 RPC (per cloud  ;D). I know it because I?ve also designed my own stirling 1 moving part variant. It simply takes more than what's depicted in the above schematic.

Your project is not doomed. Who said it was? Instead, just keep elaborating on it and developing the subject to see how far it/you can go.
As about competing with Sandia that would be another story?

Cheers,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: AhuraMazda on February 29, 2008, 05:48:17 PM
The guy in this video demonstrated an engine like the one you talk about. I am not sure if this is that specific video.

http://youtube.com/watch?v=ofsxZfu9rW0&feature=related

AM
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on February 29, 2008, 05:53:56 PM
@tinu,

I did put a big smile in there, did I not?  ;D I'm terrible at math. Are you able to compute
approx. how much energy we can get from a temperature difference created from a 1 sq. meter
parabolic disc focused on the hot side of a Striling engine? What I mean, how big must the motor be to
get approx. 300 Watt from the sun? How big is a 1/2 horse power Stirling engine?

One advantage I see with my idea is the closed one piston engine. No need to use any complicated seals etc.
The piston can be made of very light material so the only weight will be the axle and magnet.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on February 29, 2008, 05:58:33 PM
@AhuraMazda,

No, the video you posted is not related.

This video is.
http://youtube.com/watch?v=3O1xacAu4jA

My big difference is to get rid of the loss by not using flywheels.
Also since the engine is closed there is no need for exspensive and difficult seals etc.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Gearhead on February 29, 2008, 06:16:07 PM
In the 1970's there was a closed, sealed, free piston stirling engine with a parabolic mirror being offered for sale in Popular Science Magazine that was claimed to be able to produce 100 watts.  I remember the story about how they kept experimenting with different weights of pistons until they got a resonant system that worked.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on February 29, 2008, 06:30:42 PM
@Gearhead,

Thank you for the information. Do you remember where or who? Maybe a web link?

I have decided to try out my idea, making a prototype. I will use a 46 cm parabolic mirror.
I will also use water cooling on the "cold" part of the engine. The maximum temperature
with a small parabola like that will be 400 - 600 degrees Centigrade on the warm side of
the motor. Depending on how much help I will get on this forum my project will take from
some few weeks to a year to complete. I have computed the total cost of this project
to be approx. 4500,- NOK. (865USD). My goal is to beet the output of a solar panel of
equal area as a 46cm parabola.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on February 29, 2008, 07:04:38 PM
@All,

Take a look at this video:

http://youtube.com/watch?v=kYKOjnCwmG8&feature=related

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: dutchy1966 on February 29, 2008, 09:36:48 PM
Hi groundloop,

I've been pondering about the same sort of stuff lately. I mainly came to the conclusion that a parabolic trough is too expensive/complicated for an amateur scientist. On the other hand Fresnel lenses are cheap and easily obtainable.
The question then becomes what best to do with the focussed sunlight. It has enormous heat potential. We can either use it through a stirling cycle as you suggested or use solar panels (not so efficient). I'm still looking at oscillating steam engines to use. The oscillations can then be used to generate power by a magnet/coil combo (as in your stirling design).

I have made a little drawing which shows a way to maximize the use of fresnel lenses in a for amateur doable way.

Maybe it is usable for your plans or it will give u some new ideas

btw the picture shows an evacuated solar tube in the center but it could also be the hot side of a stirling engine. The yellow lines are supposed to be the rays from the sun.....



regards

Robert
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on February 29, 2008, 10:00:06 PM
@Groundloop,

Late reply. I was out for dinner and I?m a bit lazy now so it won?t be a very elaborate answer.

First: I?m not an expert in Stirling engines, neither in thermodynamic ones. So, may views are subject to human errors and surely to various improvements.
Second: Pretty much like most endeavors, the burden rests on the inventor/initiator. This is said to take my views as coming from the side.

I deduce you?re from Norway. First issue would be to decide whether focusing the sun-light or not. It dry or very arid/desert area it seems more advantageous to vote for focus. But there are great disadvantages: tracking the sun (energy and money; good control mechanisms are needed), provide good mirrors often in not common geometrical shape (hard to manufacture and expensive) and keep those mirrors clean; increased risks (birds, fires, burns etc); very narrow window of high efficiency, easily affected by light clouds and other phenomena. I know that for Europe most solar water heaters are not-focused or just lightly focused using small mirrors behind collectors. My option would go into that. But if you decide to focus, well be it. However, on a large body that absorbs heat and transfer it to a sink (like a stirling engine does) 400-600Celsius will require large mirrors. How large? That can be told only after the engine is designed because it will give the amount of heat transferred from the hot to the cold side per each stroke. Also, the hot area of such setup shall be placed in vacuum for minimizing loses and also under some kind of one-way reflexive layer (but these can be bought as they are already manufactured and widely used for various purposes).

For power estimates, I'd go at a maximum of 1.2kW/sqm. It is highly arguable and subject to local conditions. That?s what I used so far. Assume 90% eff for mirrors and you have 1080W (maximum) focused on a given surface. Now a whole bunch of questions arise. Getting to the equilibrium temperature depends on each choice: surface area, color, heat capacity, heat transfer, black-body radiation. I?d go for simple experiments using a 1-2KW heater versus mirrors on a ?Stirling dummy?, starting from Q=C*Delta(T) and drawing a graph. It will go flat toward high temperatures, thus giving a better estimate about 400-600Celsius . My actual guess would be more like 200-300Celsius for a homemade setup.

How big is a 300W Stirling?
It depends on the working pressure. Higher the gas pressure, smaller the engine. It resides in p*V=N*R*T and W=p*Delta(V) as long as p can be approximated as constant.
http://youtube.com/watch?v=BBZDJn6B0cs might actually be around 300W (?) but I don?t think it will suit you. ;)

The only issue I have is that the motor you drew above will not work. Please take a closer look at it. There is nothing to make the piston to move back and forth. You still need to provide a mechanism for that. Also, please have a look on Stirling theory and also at practical devices. There is not a single one that takes power from the displacer. Displacer is always powered (usually by the piston through a flywheel) and it is used to circulate part of the working gas between hot and cold side, thus ensuring the required cycling.  Not only that the displacer (which is not air/gas-tight in respect to the cylinder) is always powered by the main piston, but the main piston is as air-tight as it can be. But in your drawing, if I understand it correctly, the gas will simply pass through the space between the displacer and the cylinder if there is such space. Very little work is transferred by the almost freely passing gas to the displacer and this gas-flow is only temporarily (until thermal equilibrium is reached). No work.
On the other hand, if I misunderstood the drawing and there is not such space and you rightfully put the name ?piston? where it is, the piston will indeed be forced to move by the developing pressure inside the gas due to heating. The piston will indeed be pushed back when you heat the hot side and will do some work in the process but then it will stay there forever, or at least until the heating cease. You need a mechanism either to stop the heating or to increase the cooling, otherwise the piston will not move from that position.
So, either way I really don?t see how it can possibly work. That was the only issue I raised in my first post.

Guess we?ll talk more tomorrow. It?s already late here.

Cheers,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: dutchy1966 on February 29, 2008, 10:15:40 PM
Hi groundloop,

You might wanna look at this nasa slide presentation about free piston sterling engines:

http://www.grc.nasa.gov/WWW/tmsb/stirling/intro_stirling/Slidepage.html

hope it is useful

regards

Robert
Title: Re: Closed chamber Stirling engine generator.
Post by: AhuraMazda on February 29, 2008, 11:56:28 PM
@dutchy
Could you please post whatever is there? I am told I need a NASA pass to look at the page.

AM
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 01, 2008, 12:14:53 AM
@dutchy1966,

Thank you for your ideas. Yes,  Fresnel lenses will work. But a parabolic dish is not expensive/complicated.
Buy a multi head (wide horizontal) ready made disc. Glue on aluminium sheets. Put one one layer of
clear sealer, and there you go. You can also use a normal (very cheep) offset antenna (for satelite TV receivers)
covered with alum. foil and clear paint.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 01, 2008, 01:07:25 AM
@tinu,

Thank you for you detailed post.

   The problem I see with my design is the lack of flywheel. But do we really need
   a flywheel? We can use other means of providing the flywheel effect. I have a coil (or coils). There is no law in nature
   that prevent us from using a tiny part of the power to make the flywheel effect electronically. (Or by magnets?)
   By doing that we can get the compression cycle to the engine.

   My drawing is a very inaccurate idea drawing only. It is there to show us that it is possible to convert the piston movement
   direct to usefull energy without any other moving parts. Since there is no need for a flywheel the design of the generator will
   be very compact and simple. It will also be airtight so that other gasses than air can be used inside the motor.

   Me living in Norway is besides the point. It will be dumb to use this is Norway anyway because we have all the energy we need
   from water power plants etc. My main goal was to spread the idea to improve current Stirling solar plants. My second goal was
   to see if my method works. I already know that by using normal Stirling engines and generators you can get the double of energy
   output compared (area wise) to Sun panels.

   Again, I must stress that my drawing is not an engineer drawing but a simple idea drawing to show that it my be possible
   to get the energy out of the motor with a magnet/coil instead of a flywheel and generator.

Placed at the focus of a parabolic mirror a Stirling engine can convert solar energy to electricity with an efficiency better than non-concentrated photovoltaic cells. http://en.wikipedia.org/wiki/Stirling_engine

 Groundloop.


 
Title: Re: Closed chamber Stirling engine generator.
Post by: Gearhead on March 01, 2008, 02:55:33 AM
@Gearhead,

Thank you for the information. Do you remember where or who? Maybe a web link?

I have decided to try out my idea, making a prototype. I will use a 46 cm parabolic mirror.
I will also use water cooling on the "cold" part of the engine. The maximum temperature
with a small parabola like that will be 400 - 600 degrees Centigrade on the warm side of
the motor. Depending on how much help I will get on this forum my project will take from
some few weeks to a year to complete. I have computed the total cost of this project
to be approx. 4500,- NOK. (865USD). My goal is to beet the output of a solar panel of
equal area as a 46cm parabola.

Groundloop.

A fellow named Beale invented the free piston Stirling engine.  Here is one for sale.

http://www.stirlingengines.org.uk/manufact/manf/usa/new6.html

This thermoacoustic engine seems to be a better way to go.
http://www.io.com/%7Efrg/tac.htm

There is a video of a working machine on the main page here.
http://www.io.com/~frg/

More Stirling info
http://www.sunpower.com/lib/sitefiles/pdf/productlit/Engine%20Brochure.pdf
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 01, 2008, 03:28:27 AM
@Gearhead,

Thanks.  :D

After seeing the TAR and the TAC systems, I start wonder why we still use those ineffective internal combustion engines.
I has become quite clear to me that the Stirling engine method is superior to any other engine in many applications.

As an energy converter, the MEMS-TAR can be printed in ganged arrays on a single panel substrate, complete with circuit wiring and power conditioning circuitry, to convert solar energy to 60 Hz electrical power at two to three times the efficiency of photovoltaic cells, and at 5% of the cost. It can be embedded into interconnecting roofing shingles for residential power--shingles that building contractors can install on new or existing homes. In large arrays, it promises a new era for independent electric utilities. Plant expansion can now be done cheaper and with no increase in fossil fuel consumption and no emissions control costs. It can also be used to convert waste heat from boilers, industrial processes and engines back into useful electrical energy.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Gearhead on March 02, 2008, 02:55:54 AM
@Gearhead,

Thanks.  :D

After seeing the TAR and the TAC systems, I start wonder why we still use those ineffective internal combustion engines.
I has become quite clear to me that the Stirling engine method is superior to any other engine in many applications.

Groundloop.

Both Ford and General Motors have built prototype Stirling powered vehicles and done extensive testing with them.  They were 10-20 percent more efficient than ic's.  There are two major drawbacks to efficient Stirling technology.

  One is that a Stirling engine takes time to start up.  Ford's prototype car took 30 seconds to develop enough power to pull away from the curb.  Pulling away from the curb does not imply that full power is even close to being avaiable.

 Number two is that an efficient Stirling requires exotic expensive material that can stand the high temperatures and pressures. 

The third problem is that it takes money to retool for a new technology.  Why change when people are still buying the same thing they have for a hundred years?  Chrysler company built 50 turbine prototypes in the 60.  They did the same thing with them that General Motors did to the electric cars they made for California.  Keeping the status quo keeps everyone happy raking in the cash.

There is a Stirling powered airplane account on the web.  It takes time to start up, but they use a bypass to reduce power so that the heat energy is available in case they need to power up and go around during a landing.   The engine is reportedly extremely smooth and quiet.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 02, 2008, 01:08:08 PM
@Gearhead,

When we use a internal combusting engine then 1/3 of the energy form the fuel goes out the exhaust port,
1/3 is lost as heat and 1/3 is used to propel your car.

With a thermoacoustic engine (or the MEMS-TAR system) we can use 1/2 of the former gas need,
now converted to electricity and then use a highly effective electric motor to run the car.

Groundloop.

Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 02, 2008, 02:53:19 PM
@tinu,

You are right. My first drawing with one piston will not work very well.
I have made a new one. Do you think that this method will work?

The "cold piston" is free to float on the steel axle. At both sides there is springs.
Two small plates welded to the steel axle will push the cold piston back and forth
but at a slight delay because of the springs. At the other ends of the welded plates
there is springs to restrict the maximum travel the warm piston can have.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on March 03, 2008, 01:19:11 PM
Hi Groundloop,

I?m afraid that it will not work either, but who really knows?!
The way I see it, the gas to the left of the hot piston is not doing well. It is heating and expanding at first. Then, it will relatively quickly reach thermal equilibrium, having basically the same temperature as Thot. Now you plan to push the red/hot piston to the left and somehow to repeat the process. But this will compress the already hot gas, making it hotter than the hot source itself. To me it doesn?t looks right; a thermodynamic engine always takes heat from the hot source and transfers it to the cold one, producing some work in the process, while here heat seems to be transferred to the hot side.

Cheers,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 03, 2008, 04:43:19 PM
@tinu,

Are you sure? If we put heat on the hot cylinder the gas inside will expand pushing the blue piston
to the right. The blue piston will compress the spring while moving right until the next spring stops
the piston. The red piston will also move to the right because the blue piston is pushing the spring.
Now we have moved a expanded hot gas to a water cooled area and the gas will cool. The blue piston
will (by the spring action) move left again and push the red piston left thus filling new cool gas in the hot
area. Since the blue piston has more mass than the red piston then the compression will happen.

Any reason that I'm wrong here?

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on March 03, 2008, 05:38:54 PM
@Groundloop,

I?m not saying you are wrong. You may be well right. But to me, the drawing is still not clear.
Question is: what is the red ?piston?? Is it a ?piston? or it is a ?displacer??
By ?piston? one usually understands a perfectly gas-tight setup. On contrary, by ?displacer? one understands that it is not gas-tight at all: there is a space large enough that allows gas to almost freely pass from one side to the other (left-right).
Usually using two pistons does not make sense (one is redundant) and Stirling is based on one piston and one displacer. The role of the displacer is extremely important; it is actually the 'heart' of Stirling engine. The ?brain? is given by a phase difference of about 90degrees between piston and displacer, that being ensured through appropriate mechanical links to a flywheel. I don?t know if a spring setup is able of ensuring the same phase difference (it may be) but until that point I was having question marks in properly reading the drawing.

Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 03, 2008, 08:14:18 PM
@tinu,

Thank you for your help. The red one is a displacer. The blue one is a piston.

I do not think I will get a phase difference of about 90 degrees between piston and displacer,
but I will get "some" phase difference because of the distance the blue piston will travel plus the distance
the springs will compress. The question is if this is possible to engineer so that the phase difference will
be close to 90 degrees?

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on March 04, 2008, 09:59:29 AM
Here is something interesting that I?d like to buy in the near future: Stirling engine used as fan (about 0.5W). A small standardized stirling engine to play with.  :D
Look for MSI PowerlessAirCooler, if interested.

Cheers,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 04, 2008, 06:19:28 PM
@tinu,

If we redesign a PC in such a manner that we put every heat generating component onto the same plane and in a small
area, then we could have used MEMS-TAR systems to recycle 1/2 the heat back into electricity again.

A very neat and cool CPU cooler indeed.  :D

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 04, 2008, 11:19:36 PM
@tinu,

Do you think this rotary Stirling engine will work?

Engine has a fixed position rotor and a sliding piston in the rotor. The piston will run flush at the cylinder walls. The heat is applied at the top of the engine and the cold side is at the bottom of the engine. Engine is a closed gas cycle, no venting to the outside of the engine.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on March 04, 2008, 11:39:47 PM
@tinu,

Do you think this rotary Stirling engine will work?

Engine has a fixed position rotor and a sliding piston in the rotor. The piston will run flush at the cylinder walls. The heat is applied at the top of the engine and the cold side is at the bottom of the engine. Engine is a closed gas cycle, no venting to the outside of the engine.

Groundloop.

Now that?s a brilliant idea!
I?d go for it as of tomorrow but I never put my hands on a wankel in my whole life, so it would probably be far beyond my actual technical capabilities.
One totally minor suggestion that I hope will not cast the slightest shadow on your ingenuity: place hot and cold on diagonal. Correct angle is to be determined as a function of elliptic and gas pressure inside chambers. Mere details! Exciting idea!!! I?m speechless?

Many thanks,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: hansvonlieven on March 05, 2008, 12:21:46 AM
G'day all,

I don't know why they would use such an idiotic system as direct heat from solar collectors such a parabolic mirrors. All you get is erratic behaviour each time a cloud passes. This problem has been solved long ago in submarines that are driven by Stirling motors. (Yes, they exist)

Instead of heating the heat exchanger directly it is embedded in a massive tank filled with aluminium oxide pellets. These pellets are heated with whatever heat source is employed. The advantage is that you get an even flow of heat into the motor  in spite of an erratic or sporadic heat source. Secondly the engine will keep running for a long time after the heat source has disappeared as the pellets store heat and only release it gradually.

Why do the guys that dream up these systems never do their homework?

Hans von Lieven
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 05, 2008, 05:45:13 AM
@tinu,

I wish that I could take credit for this idea but I can not!  :D The rotary Stirling engine is invented by Robert L. Dieter and
has a US patent number 7,185,492 B2. It was filed August 3, 2005.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 05, 2008, 05:58:00 AM
@hansvonlieven,

They use such an system as direct heat from solar collectors such a parabolic mirrors because it is much more effective than solar panels at a much lower cost.

I think that the guys that dream up these systems has more imagination then the rest of us!  ;D

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: hansvonlieven on March 05, 2008, 06:36:13 AM
Not really groundloop,

this looks like a hastily cobbled together project, using well known technology to attract investors.

Only because they have a website, passable graphics and talk big that does not give them credibility. Their project, from what I have seen, is full of holes from an engineering point of view. I doubt they have even a prototype running. This is all concept stuff.

Sorry, but this is my honest opinion until I see something more solid.

Hans von Lieven
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 05, 2008, 07:09:09 AM
Hans von Lieven,

I'm not sure what web site and guys you are referring to?

Do you state that a Stirling engine generator that are powered from the Sun is not real?

Do you state that you can't get more energy from a Stirling powered system at a lowered cost
than solar panels? (Compared to the area of solar panels vs. the area of parabolic mirrors.)

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on March 05, 2008, 04:30:17 PM
@tinu,

I wish that I could take credit for this idea but I can not!  :D The rotary Stirling engine is invented by Robert L. Dieter and
has a US patent number 7,185,492 B2. It was filed August 3, 2005.

Groundloop.

Damn, damn, damn!
Although very busy at work, I was planning to study the idea in deep details. Anyway, during the last evening it was clear to me that it?s not actually a Stirling (no isochrones at all) but still worth of investigating. Biggest challenge would be the gas-tighten requirement for sliding pistons, which is in clear conflict with low drag requirement.
Well, damn again! Nothing new under the Sun and if, by slightest chance, anything new, it?s been patented already.
So, I?ve re-made my mind: It definitely won?t work!  ;D
But we still may buy it in the next year(s).  ;)

Cheers,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 05, 2008, 04:39:01 PM
@tinu,

I had the same thought. The center steel in the piston must be very good. If the center steel is split in two with a spring in the middle then the gas-tight will be good.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: dutchy1966 on March 05, 2008, 10:21:15 PM
Hi everyone,

Afew days ago I came across a rotary stirling too, although it functions differently from the one groundloop found.
It even has construction details with it.
Maybe we can do something with that idea too....

http://www.emachineshop.com/engine

What you think?

regards

Robert

Title: Re: Closed chamber Stirling engine generator.
Post by: Gearhead on March 05, 2008, 10:36:27 PM
Hi everyone,

Afew days ago I came across a rotary stirling too, although it functions differently from the one groundloop found.
It even has construction details with it.
Maybe we can do something with that idea too....

http://www.emachineshop.com/engine

What you think?

regards

Robert
From the website this quote;

"Although this design has less points of friction than a conventional Stirling engine, it is slightly less efficient as it lacks dwell time and a regenerator, and chamber air turbulence is lower. It is not the first pseudo-rotary heat engine but it is the simplest. This site shows the simple parts needed to build the engine. The model shown has a 6 inch chamber diameter."

Rotary or reciprocating with a crankshaft are more complex and prone to breakdowns as well as requiring more machining and parts.  Free piston engines can be sealed easier and promise much longer life and less parts.
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 06, 2008, 03:25:18 PM
@dutchy1966,

Thank you for providing the link to the rotary Stirling engine.

@Gearhead,

What we need is something robust that will do the job and last a long time.

Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: xingu on March 09, 2008, 09:48:20 PM
Microgen has already developed a combined Stirling motor/generator. If I am correctly informed they can be installed in the central heating of your home using the waste heat of your central heating burner or be placed on the warm water tube spiral, to generate electricity up to a few kW a day. Now this might not be worldshocking, but at least it is a good start.
Also a dutch manufacturer of central heating systems is developing a similar device/system.
So it's not free energy, but could easily contribute to keep your energy bills low(er).
Title: Re: Closed chamber Stirling engine generator.
Post by: Overwrought on March 20, 2008, 11:47:33 PM
Hello Tinu & folks!

Please bear with me as I'm new to this forum discussion thing and I just happen to blindly find your site yesterday.
I'd like to thank all of you for your constructive & critical thoughts on the Dieter Stirling Engine.  This rotary style Stirling has been a work in progress for my father for many years.  Dad holds an earlier patent from the 70's on an internal combustion rotary which I believe fueled, (no pun intended) this concept.
I cannot tell you the number of highs and lows this animal has incited.  However, after breezing through some of ya'lls topics and issues at this site I think we're in good company.
Within the last few years Dad and I have attempted to do the following: contact, make contact and then be ignored, out right rejected, well received and let down, etc, etc. by "engineers" and "engineering / prototyping firms". On the other hand we've met some truly genuine and helpful people along the way.
For the good news.
We have engaged a firm and have a proof of concept prototype in production with an ETC of 45 days.  The primary objectives: hold compression on the seals and rotate thru the closed curve of constant width with minimal resistance introduced through the seals.  I know this will function.  I'm convinced it will run with any  heat source, solar, geothermal, waste heat exhaust, etc.  The trick is to convert that heat to work as rapidly as possible as well as dissipate the heat on the "cold side" and cycle the process.
Anyone know a good thermodynamics guy?  Optimum material choices per component will be one of our next objectives.
Thanks again to all of you who've taken your time and commented on the merrits of my Dads invention.  Any of your thoughts, constructive, critically constructive or just plain 'ol critical would be appreciated.  I'll keep you posted if interested.

Overwrought aka David Dieter
 
Title: Re: Closed chamber Stirling engine generator.
Post by: tinu on March 22, 2008, 09:24:25 AM
Hi David,

It?s very nice to have you here! Hopefully you?ll come with good news on prototyping. I?ll be very interested in hearing about any advancement. Unfortunately corporate power and money are heavy players against good ideas. See Microgen above, which I have to find some time to dig upon.
Definitely I?m interested in keeping contact with you.

Welcome again,
Tinu
Title: Re: Closed chamber Stirling engine generator.
Post by: magkor on March 22, 2008, 12:08:00 PM
The Infinia solar stirling engine (http://www.infiniacorp.com/applications/clean_energy.php) is essentially what you are trying to make. I know because I had the same idea and have a drawing I made. I then went on-line searching and discovered the idea already was in production. I have a couple variations, though, that I'd like someone to look at.

Cheers
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on March 22, 2008, 02:01:51 PM
Hi David,

Thank you for posting information here. I'm very intrested in your rotary engine. Please post
informations about your progress. The world need alternative ways of producing energy.

I have one idea to improve your engine. As I understand from your patent description the rotating
and sliding piston must be "air tight" to the cylinder. This will result in a lot of friction and wear
on the piston due to the small "foot print" of the piston to the cylinder at high rpms.

One way to counteract this wear and to keep the piston flush at the cylinder at all time is to use
"floating" spring loaded piston heads. The springs will press the piston material flush against the
cylinder at all time until the piston material is "used up". See my simple drawing.

Thanks again for posting here, I will be looking forward to see more information about your engine.

Regards,
Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Justalabrat on May 29, 2009, 09:11:03 PM
gas in light out

http://www.youtube.com/watch?v=mc_qTu6PLSE

 :)
Title: Re: Closed chamber Stirling engine generator.
Post by: Groundloop on May 29, 2009, 09:59:34 PM
Justalabrat,

This was a great video! :-) A linear Stirling engine powering a lot of LEDs. Do you know if Youtube user "lecorfec" has a web site?

Regards,
Groundloop.
Title: Re: Closed chamber Stirling engine generator.
Post by: Justalabrat on May 29, 2009, 10:45:42 PM
No, i was just surfing youtube and thought it might fit this thread.

 :)
Title: Re: Closed chamber Stirling engine generator.
Post by: Artic_Knight on December 06, 2009, 07:08:57 PM
i hope i have not joined this discussion too late. i myself am interested in owning a sterling engine but i have some ideas that may help in the overall usage and development of this.

i have a very low power idea for air conditioning systems its current tech too!
i seen these plastic advertising boards on the road, they have hollow channels or straw like structures to them, they come in black,. there is a tutorial on how to convert them to solar hot water heaters! if we use this and a large partially insulated bladder (the ground will also insulate) we can store a substantial amount of heat from the roof. use this hot water coupled with a radient style heating system for the house at the cost of just one 6v water pump! this can be coupled with a 20watt solar panel and a car battery, connected to a thermostat we can also use a cold water cooling system, this can be cold water powering a normal coil based ac system. again powered by 6volt water pump convection controls most of the system (hot air rises cold sinks) now what excess heat we have can be used for the sterling and the cold water can come from a ground loop geothermal (stays 56f or less) we have a virtually free heating and air system and during periods of excess we can power a sterling :D

the down side to the AC portion of this system is that its a bit costly as ive designed, geothermal and ground bladders arent cheep. but i think we can create a "helper system" that can keep our current AC system from turning on so much with some cheeply salvaged parts and again with a sterling can produce some electricity too!

what do you think?
Title: Re: Closed chamber Stirling engine generator.
Post by: jadaro2600 on December 07, 2009, 04:33:49 AM
Stirlings are some of the easier engines to build.  I'm surprised there aren't more being employed at nuclear facilities,.. anywhere geothermal.
Title: Re: Closed chamber Stirling engine generator.
Post by: Artic_Knight on December 08, 2009, 03:43:47 AM
perhaps we should try a open source stirling engine, the design focus of which would be on creating a easy build cheep and effecient design? the one tube design is a nice idea perhaps we could build on that get get a good working model.  i estimated design costs for my ac unit say a small scale salvaged model at 600 bux ish. that should be like any ac unit just adjust the temp and it does the rest. if we were to throw in a microcontroller we could have it siphon off extra energy into electricity automatically without user intervention.