Stirlingengineforum.com

If you Google for "Pain Mound", that's the go-to technology for extracting heat from compost, but you really need to think in terms of large volumes- the power density of a compost heap is only about 250 Watts per cubic metre.

Tom Booth wrote: ↑Fri Jan 21, 2022 5:29 am A system of the sort proposed here is apparently in production in Sweden.

With a capacity of "23,000 Stirling engines anually on the current production line."

https://youtu.be/LsTYALSu56E

These appear to be Alpha type engines, heated with a heat transport fluid (liquid sodium) circulated within heat storage "pods" containing a molten aluminium alloy.

Having this appear in Sweden isn't surprising, since Sweden introduced the use of Stirling Engines in modern non nuclear submarines for Air Independent Propulsion in their Gotland class.

If the company no longer exists, are the designs and/or patents public domain? How would we check that?

airpower wrote: ↑Wed Dec 15, 2021 6:03 am But the reality is the company how made the SunPulse SP-500 no longer exists and as far as I know the claimed power was never independent verified.
The engine has a diameter of 1300mm (51 inches) and models a tenth of the size dont manage a tenth of the power.

^^
To my knowledge the project is at a complete stand still. Not a good sign.
Jurgen Kleinwachter and Olivier Paccoud have been demonstarting it.
The contact email used to be: i have zero idea if still operational.
Video from 2015 by Auroras eye films
https://www.youtube.com/watch?v=CK1bYvhewQ4
Personally i consider it a time waste, road to nowhere.
Much better energie options available, hemp and alcohol only two of them. Dont get much greener than hemp, sugar cane or fruit trees.
Henry Fords hemp power and build car https://youtu.be/3F5DcjwfMfY

JessIAm wrote: ↑Mon Jan 31, 2022 5:02 pm If the company no longer exists, are the designs and/or patents public domain? How would we check that?

Not sure what you mean by "public domain".

It appears that the patent is active, meaning, not anyone can just "steal" the design and start building and selling their own "Sun Pulse" engines for profit. I guess.

If you just mean publicly available to view and study sure:


The patent is over 20 pages.

https://patents.google.com/patent/DE112016001342T5/en

Personally I think it is a long way away from the best possible LTD type engine design. It's real value is just demonstrating that a little LTD type Stirling can be scaled up for useable power.

airpower wrote: ↑Tue Feb 01, 2022 1:54 am ^^
To my knowledge the project is at a complete stand still. Not a good sign.

Good to know, but that's unfortunate.

airpower wrote: ↑Tue Feb 01, 2022 1:54 am Much better energie options available, hemp and alcohol only two of them. Dont get much greener than hemp, sugar cane or fruit trees.

I respectfully disagree burning anything is green. Hemp, sugar cane and fruit all involve burning, which produces CO2 and smoke. While a compost heap produces CO2, it is contained and manageable, with techniques available to mitigate the CO2 released. Sterling engines produce power from any heat source, with many non CO2 producing sources available.

^^^^^ So what is the intention? kill every plant on earth by starvation ? Plants need co2 to survive, grow, flourish and we need plants to breath.

You can get ethanol, alcohol, biodiesel from hemp/fruit sugar whatever, but, you still need some kind of engine to convert (whatever) into useable energy, usually.

A Stirling engine may or may not be more or less non-polluting, depending on what gets burned and in what way to produce the heat to run it.

People could power a Stirling engine by burning tires or household trash, so it isn't automatically less polluting.

Compost though, generally is made from organic waste that will rot and produce CO2 in the process regardless of where it rots. Like my grass clippings and leaves will rot on the ground even if I don't compost.

Personally, I like Stirling engines for their versatility. They do the job regardless of your politics.

What incentives are available to defer the cost?
do solar panels function during overcast skies?

I'm glad that I'm not the only one who's trying to tap energy from a compost heap with a Stirling engine.
My plan is to build a aerobic compost reactor and mount a Low Temperature Difference Stirling engine.
The LTD Stirling engine will power a Stirling heat pump which transfer the compost heat to desired targets:

Compost heat -------------- >LTD Stirling engine
|
|
---------------------->Stirling heat pump(Powered by LTD Stirling engine)---------------------->Household heating, etc.

The goal is NOT making compost a major power source of electricity, but to turn it into an efficient heat source for household heating while producing fertilizers

We are suffering from a global energy crisis which natural gas is a major part the issue.
The natural gas is used in both household heating and the making of nitrogen fertilizer.
So, if we develop a good compost heat recovery(CHR) system, we can significantly reduce the need for this fissile fuel.
This CHR system must be compact enough for domestic use and it should run on materials which are readily available.

My plan is halfway done and the prototype compost reactor is ready.
It's made from discarded Styrofoam boxes, which can keep the heat inside it.
A reactor with adequate ventilation can significantly reduce the size of a aerobic compost pile.
It also can keep most heat energy produced from the heap from escaping.
Here are some pictures of it:
https://drive.google.com/file/d/1knFxcE ... sp=sharing
https://drive.google.com/file/d/15sSN5_ ... sp=sharing
I started a pile at 2022/05/08 with merely some grass and coffee grounds:
https://drive.google.com/file/d/1-LHvkw ... sp=sharing

The compost heap managed to reach up to 60 degrees Celsius and stayed above 50 degrees Celsius for 14 days.
I call it a success because this reactor is only 0.3 cubic meter in volume, which is much smaller than a minimal size of a regular aerobic compost heap(1 Cubic meter).

When it comes to the making of Stirling engines, however, things are not going well.
I've failed twice on building a LTD Stirling engine.
I don't have any skills and tools for machining so 3D printing is the only way for me to build mechanical parts.
The design I used is this:
https://youtu.be/ri_xSrEnjDY
It's a very detailed instruction and I had no problems while 3D printing the required parts.
I used a baby formula can as hot/cold end and the displacer/piston is made from steel wool.

After examining my failed engine, I think the failure is caused by air leakage from the cylinder and bad displacer size since the rubber diaphragm did not move while I was puling the displacer.

Back to the main topic of this thread, I think a compact Stirling system powered by CHR technology can reduce some of the energy cost, but it's not likely to completely power the whole house.

What was the ambient temperature?

Is the compost reactor outdoors? Inside a metal storage shed?

In what way will the engine and heat pump be coupled together?

By that, I mainly mean, in terms of the heat flow. Where will the heat pump draw heat from?

Above 50°C for two weeks seems pretty remarkable for such a small compost. It isn't really possible to determine anything without some idea of the surrounding ambient temperature. For example, big difference if the shed, or whatever is housing the setup, gets hot in the sun during the day at the equator, or if you live at the north pole.

Tom Booth wrote: ↑Sat May 28, 2022 11:23 pm What was the ambient temperature?

Is the compost reactor outdoors? Inside a metal storage shed?

In what way will the engine and heat pump be coupled together?

By that, I mainly mean, in terms of the heat flow. Where will the heat pump draw heat from?

The picture was taken when the reactor is built in the garage.
Now It's outdoor. The ambient temperature is around 23 to 28 degrees Celsius.
The heat will be draw from the compost.

gitPharm01 wrote: ↑Sat May 28, 2022 2:37 am I'm glad that I'm not the only one who's trying to tap energy from a compost heap with a Stirling engine.

Me too! Go get 'em!

gitPharm01 wrote: ↑Sat May 28, 2022 2:37 am The goal is NOT making compost a major power source of electricity, but to turn it into an efficient heat source for household heating while producing fertilizers

Brilliant application!

gitPharm01 wrote: ↑Sat May 28, 2022 2:37 am Back to the main topic of this thread, I think a compact Stirling system powered by CHR technology can reduce some of the energy cost, but it's not likely to completely power the whole house.

I respectfully disagree, since compost has been researched as an industrial heat source (mentioned previously in this thread), but at least we're both interested in the concept. My hat's off to you actually making this work!

gitPharm01 wrote: ↑Mon May 30, 2022 8:24 am

Tom Booth wrote: ↑Sat May 28, 2022 11:23 pm What was the ambient temperature?

Is the compost reactor outdoors? Inside a metal storage shed?

In what way will the engine and heat pump be coupled together?

By that, I mainly mean, in terms of the heat flow. Where will the heat pump draw heat from?

The picture was taken when the reactor is built in the garage.
Now It's outdoor. The ambient temperature is around 23 to 28 degrees Celsius.
The heat will be draw from the compost.

Thanks.

So about a 25° temperature difference.

On the last point about where the heat would be drawn from; I don't know, but suspect, a greater efficiency might be obtained by drawing the heat for the heat pump from the "waste heat" on the cold side of the Stirling engine.

That may sound rediculous, but this is my reasoning:

Otherwise the engine and heat pump will be competing for the same power/heat source; the compost. The heat pump would tend to cool down the compost. Less heat for the engine. Less power to drive the heat pump, etc. in a downward spiral. The colder the compost, the less aerobic digestion, less heat generated

On the other hand drawing the heat from the cold side of the Stirling engine might actually increase the temperature difference, as the heat pump acts as a refrigeration system. Cooling the engine increases the power available to the Stirling, which then has more power to run the heat pump, which cools down the Stirling engine even more, etc. etc. A spiraling INCREASE in the energy available to the system.

I may be completely wrong, but it might be something to consider or experiment with.

Hello all,

What a great thread. I read through it all and read various other links, papers and articles. I think the thread is flexible enough to accept other similar ideas - so I hope this is allowed.

I have a property that contains:
(a) A free-running stream, most of which is covered by rainforest, so the water is quite cool - let's say 15oC-20oC average
(b) A free-running natural spring, lower flow than the stream, but still enough to always flow. It also flows via a small dam. The key difference is this stream is not shaded by the forest, so it is warmer by the time it reaches and joins with the main stream, let's say 25oC average.
(c) an existing large metal shed with a large roof. The shed is located at a lower elevation than a convenient point to capture some flow from the cooler stream, and the warmer spring

Using no pumps, due to the elevation change, it would be possible to pass the warmed source via a thermal hot water system, leveraging the heat from the sun and the roof of the shed. I assume it would be quite feasible to add at least 10oC but probably more than 20oC to the warmer stream.

The climate is subtropical and apart from frequent but short rain events, the sun shines most days of the year.

Therefore, with very little cost and effort, I can create two significant water inputs with >20oC temperature delta, without need for any energy inputs such as pumps.

Taking inspiration from the thread and the various ideas and examples, I am very curious - is there any potential to use a sterling engine for this application for a generation of a small amount of power?

I suppose I could think of using either vacuum-sealed hot water tubes to increase the temperature of the hot side, and/or some sort of evaporative cooling solution to further cool the cold side. However, both would add cost and complexity vs the simple base case.

I would love to hear the opinions of those on this site.

Thanks,
David