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Author Topic: Closed chamber Stirling engine generator.  (Read 88806 times)

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #15 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.

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #16 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.


 

Gearhead

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Re: Closed chamber Stirling engine generator.
« Reply #17 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

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #18 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.

Gearhead

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Re: Closed chamber Stirling engine generator.
« Reply #19 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.

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #20 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.

« Last Edit: March 02, 2008, 02:09:23 PM by Groundloop »

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #21 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.
« Last Edit: March 03, 2008, 08:07:52 PM by Groundloop »

tinu

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Re: Closed chamber Stirling engine generator.
« Reply #22 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

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #23 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.

tinu

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Re: Closed chamber Stirling engine generator.
« Reply #24 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

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #25 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.

tinu

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Re: Closed chamber Stirling engine generator.
« Reply #26 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

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #27 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.

Groundloop

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Re: Closed chamber Stirling engine generator.
« Reply #28 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.

tinu

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Re: Closed chamber Stirling engine generator.
« Reply #29 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