3KW Stirling Engine - Pics provided

[Tom Booth]

I haven't seen the recent sand battery news, but looking into the first article that came up on the subject, this is interesting:

One of the big challenges now is whether the technology can be scaled up to really make a difference - and will the developers be able to use it to get electricity out as well as heat?

https://www.bbc.com/news/science-environment-61996520

They also say, by heating the sand to higher temperature (quite possible), conversion back to electricity would be more efficient:

"The high temperature of our storage would allow some reasonable efficiency for the electricity generation, but it still is economically challenging, as the efficiency would be in the order of 20%," says Ylönen. "We’ve actually studied this quite far, but there’s enough to do on the heat side of things for the moment. Generating electricity from heat would be straightforward, just by adding an ORC [Organic Rankine Cycle] or a steam turbine, or even a gas turbine (maybe Stirling also, but I do not see much of them commercially available yet)."

https://www.treehugger.com/viral-sand-b ... ms-5547707

This seems much more achievable from a DIY type mindset than using salts or molten aluminum alloy or something more exotic

I think the problem with all these things historically is that the developments are almost always geared towards out of reach utility scale or high tech methodologies rather than distributed, small scale, low tech homeowner scale systems.

I like the box of hot sand idea.

Even more simple IMO, skip photovoltaics to electric to resistance heating and just use direct heat storage. From a trough type collector. Much less initial conversion loss.

But in circumstances where excess electricity is a "problem", why not?

[Tom Booth]

One problem I would anticipate with a heat only distribution is, unlike parts of Finland, most communities around the world do not have pre existing, municipal hot water distribution systems.

https://youtu.be/Azaf9tKJNoA

Electricity on the other hand is more a kind of "universal solvent" as far as energy distribution and versatility. Electricity can run, or be made to run almost anything, So the recurring question in most of these articles, how to get electricity out of this "sand battery" thing

[Tom Booth]

An observation I reported on in another thread a while back:

viewtopic.php?f=1&t=2695&p=16243&hilit= ... ter#p16243

Watch the video there if you want but, what I've found, which is a bit controversial I suppose, and rather contrary to what everybody thinks regarding how a Stirling engine works ..

I've been finding, and additional research seems to support (as pointed out in the thread above) a Stirling engine works something like a dam, by actively HOLDING BACK heat.

In addition, a Stirling engine takes some percentage of it's operating energy from OUTSIDE atmospheric pressure, which in the process of operating rams compressed air (and the heat of compression) back into the hot side of the engine

In other words, a Stirling engine is always not only holding back the heat, but also, continually DRIVING the heat back into the heat source.

This is Bad news in terms of using a Stirling engine to COOL a data center, but when it comes to thermal storage? A Stirling engine not only produces power from the stored heat but acts like insulation actually retaining the heat.

Some people have vehemently disagreed with me on that point, but I'm not the only one to have made that observation.

But it runs contrary to "accepted science" i.e. the Carnot theorem of heat engine operation, which views a Stirling engine as a kind of water wheel that heat simply passes through like water through a turbine. The reality is very different IMO, making a Stirling engine an ideal solution for converting stored thermal energy back into electricity

[Tom Booth]

In reading through the above referenced "final report" from the Fort Carson inquiry. "Combined Heat & Power Using the Infinia Concentrated Solar CHP PowerDish System"

Download site: https://apps.dtic.mil/sti/citations/ADA607481

The attempt to use the Infinia Stirling generator for both heat (hot water) and power (electricity) ran into considerable difficulty largely IMO, because of the Carnot theorem.

People have been taking for granted for the past 200 years that the Carnot efficiency formula is well established, true, correct and iron clad reliable. I think nothing could be further from the truth. The Carnot efficiency formula is pure mythological nonsense without any sound foundation. There is zero empirical evidence to support it, though everybody assumes that at some point in history it must have been rigorously tested and verified. I have been able to find no evidence of any such experimental verification whatsoever.

So the Carnot theory assumes that once a heat engine takes in heat to generate an electrical output, the heat is then "rejected" and flows through to the "sink" (heating up the cooling water)

So, brilliant idea!!!

Let's generate electricity and use the hot water for space heating.

Well, that didn't work as expected. The resulting cooling water was, well, rather tepid. Not hot enough to use for any kind of space heating.

So modifications were made to the engine and to the controlling software, to keep the cooling fan shut off to get the water up to temperature.

That resulted in some kind of unspecified engine failure.

I might take a wild guess and say, perhaps excess heat caused the PM magnets to loose strength.

So after replacing the generator it was "ordered" by Infinia not to do that again.

The higher "sink" temperature that was nevertheless allowed resulted in less ∆T and generally less power output all around. So... The engine "under performed" to a rather unacceptable degree for seemingly mysterious reasons nobody could fully explain or correct.

So, today, it appears Fort Carson has several acres of photovoltaic panels, but no dish Stirling engines, (as can be viewed by entering the address into Google Earth and panning across the vicinity).

Why?

Well IMO, Carnot was wrong. The math (Carnot efficiency formula) is wrong. The heat does not "pass through" to be used twice. Once to generate electricity and then to heat hot water.

The Carnot theorem is itself a violation of the conservation of energy.

The Carnot efficiency formula for how much "waste heat" should be available results in an over estimation

In actuality a Stirling engine is much more efficient at converting heat into work than predicted by the so-called Carnot formula.

Initially, in the study, little, or nowhere near enough "waste heat" was available for space heating of the buildings. Attempting to modify the engine for more heat output had disastrous results, at best, lowering overall performance and at worst, rendering the engine entirely inoperative

The fault is not with the engine but with the theory.

[Tom Booth]

Take this unexpected outcome.

Running an LTD type Stirling on ice (really the ambient heat in the air) It would be expected that the "waste heat" passing through the engine (the room was about 64°F at the time) would be effective in keeping the surface of the ice under the engine melted.

After all, the Carnot formula would determine that at least 85% of the heat going into the engine is passing through to the "cold reservoir".

Instead as shown in the video, the ice, which was initially begining to melt at the start, re-froze solidly to the bottom of the engine.

This re-freezing continued over and over, four times over the course of about 45 minutes, before I discontinued my observations and went to bed.

https://youtu.be/2b2dIR8Eql8

There does not seem to be a whole lot of useable heat passing through these engines

The video shows the third time the ice re-froze.

After uploading the video, while writing the description, I checked, and the engine had become solidly frozen to the ice a fourth time.

[yellow88fiero]

Interesting information. I will need to research more on Carnot formula.

Based on my understanding of the Fort Carson test, the size of the dish and potential solar output should be able to do both - power the stirling at full capacity and then use excess heat for space heating. I realize they likely didn't calculate correctly or some pre-production type issue occurred. It definitely didn't produce the expected results (maybe causing the ultimate cutting of the project) but i think it would still work, but as you mention don't overestimate the excess heat.

I think the real key would be to put it up against something like a sand battery that could buffer the heat for a very long time - this would seem like it would run much more efficient and draw that energy over time - even though you need to convert the initial sun energy into the sand, but that efficiency can be quite high (90-95%). I think much better then what they were seeing by trying to do both heating and power generation at Ft. Carson. Instead conserve the energy in a big enough sand battery that allows it to run at all times. This would be the ultimate in DIY if you could design a small 1KW type stirling that can be driven by around 150-200C (or even up to 400-500C) sand in some barrel (or water heater converted).

I always like Mr. Robert Murray Smith - I think you linked to a stirling he was making with his Rocket mass stove. He recently did the sand battery as well in two videos. I really enjoyed them and see how it could all work together. He used an old propane tank converted initially for water heating, but then switched to sand with good results... Just need the correct temp differentials to make it work well.

https://www.youtube.com/watch?v=kzj1PCA_jxA

also this one

https://www.youtube.com/watch?v=9BW5GX05Fko

[Tom Booth]

Interesting, I haven't seen those videos yet, but will watch them after finishing this post.

From what I understand, or the information that was passed on to me by my friend, whom I now suspect was putting in a bid on the project...

The objective was to reduce the size of the dish to something manageable, like 5ft diameter instead of 15 or whatever.

After reading up on it recently, what the army wanted was a kind of tactical duel input solar / liquid fuel generator that was low profile and could be pulled around with a vehicle.

My military contractor buddy led me to believe that he was planning on building these smaller compact versions for domestic homeowner use people could set up in the pack yard to power their homes.

Anyway, what I proposed, with some modification of my original design, now applied to the Infinia engine as it actually existed, (my original design was from scratch, the compressor/air cycle integrated directly in one unit.

Resize_20220810_051624_4905.jpg (145.06 KiB) Viewed 21083 times

This incorporates an air cycle refrigeration system (rather than the water cooled system), also called "reverse Brayton refrigeration,

The air cycle produces Sub-Zero, near cryogenic cold temperatures. It is also a heat pump, and so produces considerable heat.

https://www.nuclear-power.com/nuclear-e ... ion-cycle/

With a little modification, I proposed such an arrangement could actually pull heat directly from the air, once it got going.

Notice the addition of a heat exchanger on the return loop.

Resize_20220810_054438_8117.jpg (153.33 KiB) Viewed 21083 times

Well, somewhat of a simplification.

The turbine, in order for it to produce cooling requires a load. That is, the turbine produces positive work output. (Not shown) I had this integrated with the engine/compressor all on the same shaft

Anyway what I sketched out here is the idea adapted to the existing engine, which I did not know the details of at the time. If I had, I might have proposed something more along the lines shown here.

Of course integrating all the components into a single unit would make the whole thing less complicated and that much more efficient.

Anyway, so my friend writes back that the response to the proposal was that it (my design proposal) "violated the second law of thermodynamics". So he was informed.

[Tom Booth]

My thinking here is that after an initial startup, using a smaller dish, using the power out to run the air cycle heat pump, the temperature differential can be increased exponentially so that the engine could produce much more power.

In actuality, there would be additional heat collected by the heat pump from the surrounding ambient environment. That extra heat would be dumped at the focal point, augmenting the solar input.

The engine would be running partly, if not entirely on ambient heat.

Little did I know at the time, Tesla had proposed the same sort of arrangement in 1900 referring to it as a "self acting engine"

A brief article on the subject:

https://medium.com/teslapower-energy/te ... b23d2a759b

[Tom Booth]

Relating this to the "sand battery" concept.

For a Stirling engine, heat is relative. What matters most is the temperature difference. It doesn't really matter if the engine runs on a box of hot sand or a box full of ice, as long as there is a difference in temperature between what's inside the box and what is outside, but, in reality, it is the HOT side that provides the actual "fuel" that in the process of running the engine gets used up.

Take the "conventional" thermal mass storage or sand battery.

Resize_20220810_105104_4817.jpg (173.96 KiB) Viewed 21060 times

The heat (or fuel for the Stirling engine) inside the box is finite/limited. It gets used up and the "battery" needs to be recharged somehow

Tesla however wrote:

Suppose that an extremely low temperature could be maintained by some process in a given space; the surrounding medium would then be compelled to give off heat, which could be converted into mechanical or other form of energy, and utilized.
By realizing such a plan, we should be enabled to get at any point of the globe a continuous supply of energy, day and night.

He was essentially talking about reversing the process by making a kind of COLD battery.

Resize_20220810_105320_0107.jpg (193.48 KiB) Viewed 21060 times

What is the advantage of that?

Well, the "fuel" becomes the accumulated heat or solar energy in the atmosphere. The source of fuel has become virtually infinite, can never be exhausted, never needs refueling.

Furthermore, because the heat energy going in is used up in the process, the heat is converted to electrical power output. The energy goes into the engine from the atmosphere as heat, then out the wire as electricity.

So, in other words, the "cold battery" is not exhausted either. Such an arrangement would run perpetually.

IMO, this was actually Tesla's "free energy" he wanted to give to the world, his life long project many of his inventions we're only elements of this one grand idea

[yellow88fiero]

That is interesting on the last picture with the cold battery - I understand what is being described, but wouldn't the use of the heat to create the electricity by the temperature differential also have a heating effect (although slight) on the cold battery (as you can't prevent the small thermal conductivity), eventually needing that to recharge as well. I could see if it was perfectly optimized that the ambient heat could be used up perfectly to match what is being produced by electricity out to not have an effect, but then just the insulation on the cold would eventually also transfer some heat and cause issues with the system as well.

Another interesting video I saw a couple months back was the plasma tunnel digging enhancements that allows for very deep holes (20KM) in very short amount of times. They propose just pumping fluid to get supercritical temperature then run standard steam engines based on this, but again whether steam or just having the temperature differential to run a stirling the key is being able to maintain something with that differential. Why not use the earth to produce that differential. I always like the fact you can dig down about 5 feet into the earth and get pretty consistent temperatures. Use this against the ambient air and effectively get some benefit thanks to the differential. This can be effectively seen as a perpetual engine, just having the correct differential with an appropriate way to convert it to a usable energy (electricity or other). Heat pumps are getting coefficient of performance ratings huge, because they aren't creating energy, just transferring it from differentials. I don't see any difference in this case either.

If you can get a stirling with some performance of 40% (difficult now) and a heat pump with a COP of greater than 2.5 couldn't you effectively have a perpetual energy maker. --> 1000W energy to bring in 2500Watts of heat (or cool), convert 2500 Watts of heat differential with efficiency of 40% to electricity and get 1000W back. So COP of 2.6 would produce extra 40 Watts, giving you "free energy". I am pretty sure my heat pump hits like 2.8 or more. Now if only I could convert 2800Watts of energy back to electricity efficiently... Your design above has the heat exchanger on it, so I am sure that is a big part of the overall machine.

Interesting stuff...

[Tom Booth]

I'm not sure if ambient heat transfer through the engine is completely avoidable. Very unlikely, but an insulated box is not going to keep out all the surrounding heat. A vacuum insulated box, like a thermos might come close.

But obviously SOME heat will get through, which is the reason for the heat pump, not just to produce an initial cold in the box, but also to keep it cold, as needed.

IMO, I would think that a Stirling engine powering a heat pump is similar to a gas engine powering a fuel pump.

Nobody cries about any violation of physics or calls a gas engine driving a fuel pump "perpetual motion".

A heat engine using a heat pump to deliver it's "fuel" (heat) seems no different to me. But... according to the 2nd law of thermodynamics, such a heat engine heat pump combination is supposed to be impossible.

But if you look for proof that it is impossible, the only "proof" given is... No one has ever succeeded and many have tried. To my mind, that is nothing more than conjecture. It's never been done so it's impossible.

But, looking into the history of such things, it looks to me like it has been done, many times, but the discoverer or inventor is accused of fraud and the invention dismissed as impossible, in spite of clearly observable evidence.

Charles Tripler is a case in point.

http://www.douglas-self.com/MUSEUM/POWE ... uidair.htm

There is a long list of similar inventors, but there seems to be a strong, irrational, almost hysterical prejudice or aversion to even considering the possibility of any such thing.

John Gorrie is another inventor who made similar claims in regard to his ice making machine. He suggested that the machine required no external, or very little, power input, because his ice making engine was powered by the same heat being extracted to make the ice.

So far, my own experiments along such lines add some additional weight to the accumulated historical evidence.

Maybe this engine will help prove it. At least I'm aiming to try

[Tom Booth]

Is this the plasma drill you mentioned?

https://youtu.be/RiZysvCDC3k

You seemed to be talking about something specific to geothermal.

We were looking into geothermal for possibly heating our home and business buildings, but neither have enough acreage for anything horizontally, so that would involve deep drilling, which would likely be expensive, but...

99% or whatever cheaper than conventional drilling.

I wonder what happens when this plasma drill thing hits water?

Continuing to look around, it seems there are a number of additional companies jumping on the bandwagon, using or developing some form of plasma drilling.

[Tom Booth]

BTW, I was at the auto parts looking for some Alan key type sockets to fit this engine to take it apart, (not necessarily right away, but to have on hand).

There was a mig welding setup inside the door with a tank of inert gas. This store manager sometimes puts things out for sale, (I bought a generator from him recently.)

Anyway, it wasn't for sale, he said he just bought it to use himself. Out of curiosity I asked where he gets his tanks filled. He told me, and mentioned that the place is also a machine shop that does quality work and is well equipped. I may be taking the engine over there this afternoon.

I also put the vibration dampener on, and tried the rubber mallet again, it went up as high as 6 volts This little meter doesn't have an amp setting, so I'm not sure about total watts yet.

6 volts is a long way from 3 kilowatts, presumably, but for just tapping the thing with a rubber mallet to produce a slight vibration, kind of impressive. I'm not sure if the dampener is the reason for the higher voltage, or maybe I'm just tapping it a little harder or found a more responsive spot to hammer on

[yellow88fiero]

...
IMO, I would think that a Stirling engine powering a heat pump is similar to a gas engine powering a fuel pump.

Nobody cries about any violation of physics or calls a gas engine driving a fuel pump "perpetual motion".

A heat engine using a heat pump to deliver it's "fuel" (heat) seems no different to me.
...

I think these points you mention are key and a very interesting way to talk to people about it. People are finally realizing heat pumps just move heat (not create) - so if you can move enough through a system that the delta of ambient temps with the earth (cooling or heating) then you can effectively run forever. It is not breaking thermodynamics - it is using the earth temperature differentials to power things...


Sorry - I missed linking the video - I will get to that in a little while.

[yellow88fiero]

Here was the geothermal video I saw:

https://www.youtube.com/watch?v=61mz4vr1EeE


It is pure geothermal, but due to 20KM depths in 100 days (if they can pull it off) the differentials will be so great they can just direct drive steam engines. Use the earth to drive energy...