I want to build a high efficiency Stirling electric generator

[Dann]

https://www.youtube.com/watch?v=adLZIDxM8tQ&t=283s

https://tallbloke.wordpress.com/2013/04 ... tinkerers/

I read that it can reach 40% efficiency.
which meant more than the otto or diesel engine.

I want to do some tests. To build or buy such a generator.

Whoever wants, help me. I haven't built stirling before.

[MikeB]

How was that 40% calculated / measured?

Most of us are used to _ slightly _ lower numbers than that...

[Dann]

From:
https://www.intechopen.com/chapters/62541
"The estimated Stirling cycle efficiency (heat to work) is about 45%. The system efficiency (fuel to electricity) is around 38.3%."
There was a company that produced such generators and sold them, but I think it went bankrupt.

Then NASA Stirling has a slightly higher efficiency than Diesel and Otto.

NASA also made a truck with a stirling engine and showed that it consumes less than an ordinary truck.
Of course, the car with a stirling engine does not have the same start, it is not as practical but it consumes less.

[Tom Booth]

American Stirling maintains a page that may be of some help:

https://www.stirlingengine.com/generators

There is a link to companies producing Stirling engine based heat and power systems:

https://www.stirlingengine.com/recommended/combined/

It's a pretty tall order.

I personally find it rather perplexing and frustrating that something that can be built as a small model, out of tin cans and balloons and pop sickle sticks by just about anyone, and with dozens of "toy" model engines on the market, billions spent in government grants etc. for various development projects, isn't more readily available to buy.

I have similar ambitions to possibly design and build and possibly get to market some kind of practical Stirling generator. Not necessarily ultra-high efficiency just affordable and available for ordinary people who might have some FREE heat source, solar, wood scraps, biogas, etc.

[Dann]

"I personally find it rather perplexing and frustrating that something that can be built as a small model, out of tin cans and balloons [...], isn't more readily available to buy."

Either there are interests, or we do not understand the disadvantages, as with the fuel cell which are many kits but are not used in practice.

Or people don't understand the benefits of the stirling engine. As was the case with the FET transistor invented 20 years before the bipolar transistor..
No one wanted to replace electronic tubes with FET traistors for 20 years.

I am looking for great efficiency.


If stirliing generators are not on the market, we could either be sad or glad that we can make one out of a lack of competition.

[Dann]

https://www.stirlingengine.com/generators

"Stirling Engines in Cars – A Bad Idea

There was a big government-funded research project to put Stirling engines in cars.

But, Stirling engines intrinsically ACCELERATE SLOWLY and they’re DIFFICULT TO REGULATE efficiently (go from idle to full power quickly).

So, it never was a good match between the technology and the application."

This is one of my projects
And I certainly invite anyone who wants to participate.

The stirling generator will generate current, And the car will have an electric motor that will be easy to control.
But all this requires a justification. Why is it better that way?
Will it be more efficient than the diesel engine or not?

[Tom Booth]

.
(...)
The stirling generator will generate current, And the car will have an electric motor that will be easy to control.
But all this requires a justification. Why is it better that way?
Will it be more efficient than the diesel engine or not?

I was thinking along the same lines not long ago:

Screenshot_20211003-182322.jpg (181.54 KiB) Viewed 9019 times

[airpower]

High pressure air power is the future. No need for unnatural lethal AC power at all.
Anything in a homestead with a motor can run of airline or tank. No need for conversions and expensive electronic.
800 watt motor almost perfect match for 1kw free piston engine
https://www.youtube.com/watch?v=AeSNEeq42t4
Average home refrigerator uses 350-780 watts

Yes i am very much interrested in free piston engine without the generator part, only attached to a airpump to fill tank.
Simpler, cheaper to build and more efficient.

[Tom Booth]

High pressure air power is the future. ...

Yes i am very much interrested in free piston engine without the generator part, only attached to a airpump to fill tank....

I agree,

Compressing air can also be a supplemental source of "waste heat" and running/using air as a power source results in cold exhaust air from the air motor.

Are you familiar with the Pneumatic Options Research Library? http://www.aircaraccess.com

The forum there is one of my other favorite hangouts on the web.

[airpower]

Heat waste can be overcome with water, commercial solution: https://youtu.be/sBF5EnK9MPs
Air powered tools last longer are cheaper and have more torque than electric counterparts.
Air powered workshop:
https://youtu.be/Oc0b4aBOyBw

Modern air motors are way more efficent the old piston driven variants. Patent and licenses restrict the progress, years pass and pass.....
https://www.engineair.com.au/
The challage is to find efficent way to get air into the storage tank. The way i see it the free piston engine is one of the best methods.

[Tom Booth]

Heat waste can be overcome with water, commercial solution: https://youtu.be/sBF5EnK9MPs

So... (In the video) The, presumably, photovoltaic (electricity out) powers water pumps, how? Logic would seem to dictate electric motors.

There is something like 25% efficiency - World record being about 40% using very expensive panels, impractical. More realistically probably 15% for commercial photovaltaic panels.

Solar generated heat to power a Stirling engine would, in theory, be vastly better, efficiency and cost-wise.

Interesting concept, using water pumped into air tanks to generate pressurized water to run turbines.

I don't think a conventional "free piston" Stirling (no connecting rods) would be capable of powering a mechanical water pump directly though. That would be a contradiction in terms, I think, probably.

Aside from all that. My point about "waste heat" from compressing air was that the heat of compression could be a direct energy resource in itself to power, or assist in powering, the Stirling engine being used to compress the air in the first place. So-called "bootstrapping".

I was thinking primarily in terms of transportation. Could such a water based pressure system be practical for a motor vehicle?

Many households with a private well, have similar air pressure tanks to temporarily store energy, so the pump does not have to run as frequently and smooth out the flow. Otherwise the pump goes on and off excessively.

I'm thinking that compressing air with water would not really eliminate the heat of compression. The water, having a very high heat capacity simply absorbs the heat. Where does that heat/energy go from there? The "up to" 81% efficiency seems dubious.

Storing the pressure tanks underground provides insulation and/or thermal mass, though the compressed air (in the video) is apparently, eventually stored above ground where it would be subject to heating and/or cooling, or both, depending on ambient temperature.

Just rambling, thinking out loud. A lot of food for thought.

My main point was that the heat of compression could be used as a resource, providing some of the heat to run the Stirling engine, rather than this heat being something to avoid or "overcome", how could it be used to advantage? Likewise in regard to the cold Exhaust produced in operating an air motor.

Compressed air systems generate a temperature differential, in essentially the same way as a vapor-compression heat pump. Compressing air generates heat. Decompressing air through an air motor or turbine produces very cold exhaust air.

Some system or arrangement should be able to make use of such a temperature differential generated by the compressed air system.

A Stirling/Compressed air power system would appear to be an ideal combination.

A system that included a large/heavy thermal mass, such as tanks of water, would probably not be practical in a system intended for personal autonomous transportation. Some mass public transport system perhaps.

[airpower]

I was thinking primarily in terms of transportation. Could such a water based pressure system be practical for a motor vehicle?

No, modern air powered cars heat the air in engine or before entering to increase range/efficiency, more or less a hybrid system. The air is stored in 250 bar (3600 psi) tanks. Refilling at home takes hours when pluged in into mains, 2-3 min on dedicated fulling station.

A Stirling/Compressed air power system would appear to be an ideal combination.

Yes, it certainly is one of the best systems going forward. On a boiling day when most cooling is needed for fridge or aircon is the time when the solar powered Stirling is producing the most power. The compressors can be powered straight from the air tank, no need for back and forth conversions to electric.
Solar panels have efficiency of 20% give or take 2 percent. With the same area used free piston setups can harvest way more solar energy.

[Tom Booth]

(...)
The challage is to find efficent way to get air into the storage tank. The way i see it the free piston engine is one of the best methods.

On the website: http://www.aircaraccess.com/ this subject; an efficient way to get air into the storage tank, is gone over quite extensively.

There is a theory put forward there, that there is, or are, (or was) a way to fill an air tank similar to the method used for filling steam engine boiler tanks with water by entrainment, using an ejector. (Or injector)

Steam injectors are a fascinating subject in themselves.

https://youtu.be/4wsiXPgfdlI

After compressed air is expanded through an air motor it exhausts extremely cold. In theory, such cold dense air could then be entrained and injected back into the tank using the high pressure air from the same tank.

This very cold air, injected into the tank then, of course, increases in temperature (and pressure) due to the surrounding ambient heat.

If this works with steam, (liquid water, after all, is just cold steam), why should it not also work by entrainment of cold air in much the same way?

There are accounts of such air powered cars that could in some way keep their air tanks full, greatly extending their range, by recycling the cold exhaust from the air motor, which could then be expanded through the engine again as it absorbed ambient heat.

This seems like a very far fetched "perpetual motion" type scheme, but rather intriguing anyway.

[airpower]

^^^^I have to see if i find it again but something like it was archived only with air with a air powered car engine.

Anyway, the whole thing in reverse. Free piston Stirling coolers arguably some of the best, (with matching price tag).
https://www.youtube.com/watch?v=ZSJFPb8030g

Operating, it might be the SC-TG08S Discontinued Model
https://youtu.be/BIMexiwnTQE

TWINBIRD Free Piston Stirling Cooler / 全商品
http://fpsc.twinbird.jp/products/list.php

[Dann]

Do I need high pressure for high efficiency? 100atm?
I'm disappointed because I can't have such pressure !

Strangely, the supplier of such generators no longer produces, is bankrupt.
And here you wanted to change the subject.
https://www.youtube.com/watch?v=j7Ja05DKZsk

Even a large company like Philips no longer produces generators with a Stirling engine. They cannot go bankrupt. What is the reason for not producing anymore.

A good explanation of how the Stirling engine works and what the regenerator does is here:
The easiest we understand from the Clapeyron diagram (P-V)
min 3.31 100 atm?????????
https://www.youtube.com/watch?v=GqIapDKtvzc

Philips invented audio cassette and audio CD? Then Philips is a great company. The explanation about Stirling in the video above is given by Philips.