stirling engine

I found out about these a few days ago.  It seems that when heated, they could run a generator.  It makes me wonder about having something that might light your room that sits on your wood stove.  Or maybe your winter fires could feed power to the house.  Or, in an emergency, you could have a wood powered generator.

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

http://www.youtube.com/watch?v=I68Ho12DK6Y

The Stirling engine was patented by Robert Stirling in 1816.

Stirling Engine at Wikipedia:  http://en.wikipedia.org/wiki/Stirling_engine

American Stirling Company:
http://www.stirlingengine.com/

Sue

You would think it would be something advertised all over the place.  Something that you would stick on your wood stove in the winter that would light a room or something.

The main problems appears to be cost vs profit.

The book from the Stirling Engine Co. would be an interesting thing to read if you understand mechanics (it's all magic to me).

You would think it would be useful for something like well pumping or lights or powering a computer or something.

As the cost of fuel climbs, we may be hearing more about it.

I was just looking up the book to see if it was in my library system or at Amazon (no), but there were a few interesting book titles:

Build a Two Cylinder Stirling Cycle Engine by David J. Gingery  (1991)

Building the Tesla Turbine by Vincent R. Gingery (2004)

Stirling Engine Design Manual by William R. Martini (2004)

Stirling and Hot Air Engines by Roy Darlington and Keith Strong (2005)

Stirling and Tesla.... now THAT would be an interesting combination, wouldn't it?

Sue

That does kinda sound like a pretty weak electrical contribution.

I wonder if it is something where if you did it right, it would run from something solar during the summer and run on your wood stove during the winter.  And generate enough to put  a real dent in the electric bill just because it is running around the clock.

I asked an engineer I know about Stirling engines and he recommended this book:
http://www.amazon.com/exec/obidos/ASIN/0971391807/greaterthingsboo, while also commenting that they just aren't economical yet.

Then, in following a link to a Stirling Engine manual, an Amazon reviewer provided this link for the entire manual as a free .pdf file: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19830022057_1983022057.pdf.

As in, they don't yet earn their keep?

I wonder if they were mass produced if they could be something you could buy for ten bucks and then they might earn their keep.

Thinking of recycling an old 90 degree v8 engine which is simply 4 of these sterling engines in a row if you change the cylinder head. Would have to take most or all of the piston rings off and get rid of parasitic drag but it would be a cheap project if it works like it looks like it does. Rocket burner powered pto shaft. An interesting way to have fun out in the garage.

http://www.animatedengines.com/vstirling.html

We built Stirling engines Freshman year in basic machining for funsies. They are easy to make and neat to see work, but not economical, hugely inefficient.

If you want power from heat simply install a Seebeck bridge, like they use in the Biolite stove?

Any idea where I would get such a contraption? Obviously solid state would be much better than the hokey mess that I am dreaming up (which probably wouldn't work well anyway). It's a great idea and to even get enough juice to charge some electronics would be a fun way to cut the power bill, on free waste heat.

There are lots of good books here too.

http://www.lindsaybks.com/

http://knowledgepublications.com/

Stirling engines base concepts are deceivingly simple. Even i built one that works, from beer cans and wire.
But while a moving engine is relatively easy, a good engine is kinda hard to do.

They are amazingly efficient if and when they are properly engineered and manufactured, but that is expensive.

Problems with stirling engines include:
Low power/volume, low power/mass ratio, high production cost.
The advances in the thermo-acoustic stirlings can solve some of that.


If you want to dream a bit though, do a search on youtube: "sunvention"
Sun powered stirling engines, cool eh?

very cool, yes, as I learn more I am realizing all the caveats to building a good one, my v8 idea also sounds like something that might run (maybe) but to get it to run and make useable amounts of power would probably take a gazillion dollars engineering when a purpose built one could do better for less. One key I am finding is that the ones that make any amount of useable power are pressurized usually with an inert gas.

One can use some engine parts and bits and pieces. But using most of the engine is not a good idea. To big and heavy parts.
You are right, most engines are pressurized but the mentioned sunvention is not. That is why ti is so big, while only giving only 1,5 kw. (man i like to have one of those, or build half as much)

The really fancy ones use He or H. The ideal gas is not inert but really light, so hydrogen is the best, but it notoriously escapes, not to mention dangerous. So most engines use helium instead as a practical compromise.

HI Y'all,
My first post:I've seen some neat little Stitling engine driven fans for circulating the hot air rising off a wood burning space heater. Getting into building a Rocket stove to heat my garage shop and will try building a fan as described above to direct some of the heat.Wish me luck....
Don

hi, I have just built this stirling engine. but there seems to be some problem. it doesn't startup. basically, it isn't running. I use a butane torch as the heat source but still there isn't enough power to run it. can I get some advice on how I can get it running. initially there was too much torque, so I reduced the stroke length but it still will not run. I am unable to identify the problem.nsome advice would be helpful, thanks
the pic of my model is in the attachment.

]

joe capcom wrote:hi, I have just built this stirling engine. but there seems to be some problem. it doesn't startup. basically, it isn't running. I use a butane torch as the heat source but still there isn't enough power to run it. can I get some advice on how I can get it running. initially there was too much torque, so I reduced the stroke length but it still will not run. I am unable to identify the problem.nsome advice would be helpful, thanks
the pic of my model is in the attachment.

Need more information. However, I might know what's going on. First of all, make sure you have a good build with no obstruction in the tubing and that you're turning the engine in the proper direction. What might be happening is that the relatively thick metal cylinders you are using present a bottleneck to the system due to low heat transfer rates. If that is the case, then what you would see is the engine start with a fairly high initial starting torque that quickly gains speed, then then almost as quickly stalls out. What's happening is that the heat in the high temperature inner cylinder wall is quickly transferred to the air and over to the low temperature inner cylinder wall on the cold side. However, the actual cylinder wall temperature difference quickly drops. This rapidly lowers the mean effective pressure of the engine, drops torque, and the engine slows down. However, since there is momentum stored in the system, then engine keeps cycling longer to take the difference in temperature even lower. Mean effective pressure then drops so low that the engine stalls once the momentum is used up.

What I recommend is the following:
(1) put a flywheel on the engine
(2) water cool the cool piston using a very small aquarium pump that just circulates water over the cylinder continually
(3) put a load on the engine that you can vary to find the optimal speed (might be an elastic belt with tension you can adjust)
(4) pressurize the air in the engine as must as practical... might connect the engine to a pressurized air tank or inner tube via a check valve to replenish leakage.

Stirling engines tend to run most efficiently at low speeds, and you want to find the speed that is ideal for the heat transfer rates presented by the cylinders.

hi marcos,

thanks for the ideas. that's some info I can use there. I am already working on some of the things which has been affecting the heat transfer and efficieny.

reccomendations:
1) I have a flywheel for this engine, not visible in the picture.
2) yup, that is my idea now and I am working on it also. I was thinknign of using an aquarium pump too. do yo know of any stirling engines which water cools using an aquarium pump??
3) ok, that would be a good idea to vary the load according the output.
4) pressurize the air in the engine, meaning I should have the internal of the engine at a higher pressure before I heat it up? how does this help with the engine efficiency or its ability to run?

thanks

joe capcom wrote:hi marcos,

thanks for the ideas. that's some info I can use there. I am already working on some of the things which has been affecting the heat transfer and efficieny.

reccomendations:
1) I have a flywheel for this engine, not visible in the picture.
2) yup, that is my idea now and I am working on it also. I was thinknign of using an aquarium pump too. do yo know of any stirling engines which water cools using an aquarium pump??
3) ok, that would be a good idea to vary the load according the output.
4) pressurize the air in the engine, meaning I should have the internal of the engine at a higher pressure before I heat it up? how does this help with the engine efficiency or its ability to run?

thanks

First, let me note that I don't have enough information to make a diagnosis. If my idea is correct, then the most important thing to do is start the engine slowly under load and let pressure stabilize slowly (rather than plummeting rapidly). As far as (4) goes, what I'm thinking is that a higher pressure will enhance heat transfer. It might be that cylinder walls are at sufficient temperature, but that the heat is not transferred to the air efficiently at such a low pressure. However, increasing pressure should be done in concert with the other changes, and increasing pressure might require a larger flywheel... but I'm speculating without specific information. Loading the engine along with water cooling should solve the problem if my idea is correct, but increasing pressure might increase engine power and efficiency.

BTW, the engine looks great... nice craftsmanship.

I see, I get it. I am actually working on some of the improvements such as reducing dead space, sealing all air leaks and making the engine look a little more presentable...

currently the most trouble I am facing is sealing the air leaks. sometime I can hear the hiss sound but just couldn't identify the leak so, I covered up all the possible leak spots with some rtv sealant.. just waiting for the sealant to dry before I fire it up for a test run.. will try to pressurize the air before I run it.

yea, thanks for the compliments.. the designing work was mine but the brass part were machined using a lathe in a machine shop. someone did it for me...

Balint Bartuszek wrote:
If you want to dream a bit though, do a search on youtube: "sunvention"
Sun powered stirling engines, cool eh?

Oh, that's so cool.



Here's the companies website, I wonder how difficult it would be to get them in the US?

Edit: heh, they sell a fancy version of the soda can heater.

I-Roof Technologies

Solar Hot Air Generator

I-Roof

Concept

With locally available low cost, corrugated roofing elements, Sunvention's special, highly transparent and extremely durable Miraflow film selective black painting, backside therma l insulation and optimized Air Channel Geometry, an effective and economic I-Roof Solar Hot Air Generator is created.

It requires no electrical energy to pump the air to be heated - the automatically created convection fulfill this task. The outlet air temperature of the I-Roof can be controlled over Air Duct Cross Section.
Applications

The I-Roof elements can be used in different configurations:

As convective Solar Dryer “I-Dryer”, typically for sea weed, bananas and all sort of fruits. It is modularly extendible, according to the local need. Beside regulating the drying temperature via the cross section of the Air Duct it is also possible to combine the “I-Dryer” with special PCM storages extending the operational hours over the day time.
As convective Solar Roof, “I-Roof”, to climatize houses and produce simultaneously domestic hot water
As Sea-Water desalination plant “I-Desal”.

Edit 2: Hmmm... I guess their more of an R&D facility? Anyone have a bunch of spare money to actually get this stuff produced beyond prototypes? Wonder what the costs are like?

joe capcom wrote:I see, I get it. I am actually working on some of the improvements such as reducing dead space, sealing all air leaks and making the engine look a little more presentable...

currently the most trouble I am facing is sealing the air leaks. sometime I can hear the hiss sound but just couldn't identify the leak so, I covered up all the possible leak spots with some rtv sealant.. just waiting for the sealant to dry before I fire it up for a test run.. will try to pressurize the air before I run it.

yea, thanks for the compliments.. the designing work was mine but the brass part were machined using a lathe in a machine shop. someone did it for me...

It's really difficult to build a Stirling engine with sufficient power and efficiency to be useful. They're great for learning about heat engine concepts, but not much more without lots of time and money thrown at it. If you want to try building something that has a chance of being simpler and providing more power and efficiency, then consider what is sometimes called an Ericsson or Brayton cycle. It's basically a gas turbine but using piston expanders/compressors, and should be in a closed cycle for best results. What you do is connect a piston expander similar to a steam engine to a piston air compressor, then connect between them to a heater and cooler. The compressor sends air to the heater then expander, and the expander exhausts to the cooler then back to the compressor. The expander drives the compressor and whatever load is provided. One of the main benefits here is that the heater may be a coil of tubing more easily placed in a furnace to pick up the heat efficiently. If solar energy were used, then this configuration could place the bulk of the engine on the ground with the heater coil elevated to the receiver of a parabolic concentrator. Note that I definitely prefer the furnace alternative for practicality. If you think this may interest you, then I continue to discuss some specifics.

that's some info we have here... yea, it does interest me. im eager to get building newer ones but, I want to make the current one run first. all others comes next.. hahah

thanks man

So much good info thanks guys!

joe capcom wrote:that's some info we have here... yea, it does interest me. im eager to get building newer ones but, I want to make the current one run first. all others comes next.. hahah

thanks man

I looked at the engine again, and while I'm no expert on small stirling engines, I have to say this engine doesn't look right.

You want there to be very little volume in either cylinder when its piston is fully retracted. I can't see how it's designed, but it seems like the glass is used as the sealing cylinder, and the pistons retract into the volume contained by the metal cylinders. I like that part, but I can't see how far the pistons retract. They should go all the way to the cylinder heads and close the volume as much as possible. I don't see the purpose of the large connecting tube that snakes around the engine unless it contains a regenerator. That fat tube is way too much dead air space that only robs efficiency since that air cannot be heated. Also, what's the purpose the the thinner tube?... why are the cylinders connected with two different tubes? It seems you should connect the two cylinders directly across with a single short tube about the diameter of the larger tube. The larger piston should be advanced 90 degrees ahead of the smaller piston with the large cylinder heated and the other water cooled. This is what I'm seeing, but I can't get inside your head, so work with me.

Marcos Buenijo wrote:

joe capcom wrote:that's some info we have here... yea, it does interest me. im eager to get building newer ones but, I want to make the current one run first. all others comes next.. hahah

thanks man

I looked at the engine again, and while I'm no expert on small stirling engines, I have to say this engine doesn't look right.

You want there to be very little volume in either cylinder when its piston is fully retracted. I can't see how it's designed, but it seems like the glass is used as the sealing cylinder, and the pistons retract into the volume contained by the metal cylinders. I like that part, but I can't see how far the pistons retract. They should go all the way to the cylinder heads and close the volume as much as possible. I don't see the purpose of the large connecting tube that snakes around the engine unless it contains a regenerator. That fat tube is way too much dead air space that only robs efficiency since that air cannot be heated. Also, what's the purpose the the thinner tube?... why are the cylinders connected with two different tubes? It seems you should connect the two cylinders directly across with a single short tube about the diameter of the larger tube. The larger piston should be advanced 90 degrees ahead of the smaller piston with the large cylinder heated and the other water cooled. This is what I'm seeing, but I can't get inside your head, so work with me.

there is actually quite some dead space inside the displacer cylinder. I had just reduced it using stainless steel tubes. the piston goes 20mm into the brass cylinder. the top of the piston now is at least lesser then 1 mm from the top of the piston when it is fully retracted. yes, the long tube contains regenerator. seems like you are reading my mind on this as I have just worked on it to reduce the length by about 2/3. so there is lesser dead space in that region too. yup, the difference between them both is by 90 degrees and the larger piston moves ahead of the smaller one...

thanks