DIY ThermoAcoustic Stirling Generator: Looks like a bicycle frame doubling as a range extender to me!?

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Logic11

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OK! Er... the video of this thing converting a bit of heat into electricity says it better than I ever could:

NB the movement of what would be a coil in a magnet in future designs of this small prototype, from the power of a freaking candle!
NB that a bicycle frame has a similar triangle shape, meaning this might be implemented in a bicycle frame as a range extender, for almost zero weight and space penalty..!
ie: This is a 30% efficient, (in some models) pretty quiet conversion of Gasoline, Diesel, Kerosene, whatever, into electricity!

But it gets better:
He goes on to 3D printing a lot of the bits and making it so it can be made with hand tools here:

Here he's replacing the "BRRR" bit with a 3D printed, Bi-Directional Turbine, turning a small RC motor, which should be much quieter:

If one of these these things can cover the average load of a long trip, with the std batteries and regen taking care of the peaks and troughs; you're golden and can fill up with a glass or 2 of fuel at any gas station.
Hell; it looks like even a decent size blunt would charge your battery some! :D

It's all early days in the development of the system and he's asking for suggestions etc.
There are plans etc available if you join for 99 cents.
Do feed the YouTube algorithm by liking and subscribing etc which helps fund this guy.
 
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Thermoacoustic stirling generators are notoriously inefficient, we built 2-phase heat electric convertors as a project and we managed to get less than 1% efficiency. We used dimetyl aether as a working agent and managed to get it running as low as 30C temperature delta, but the output was measured in micro watts. The main problem is, once you start taking power out, it disturbs the internal resonance and the machine stops. With actively guided stirling (displacer moving working gas), it's much more resilient and doesn't stop that easily.
 
VooteleAer said:
Thermoacoustic stirling generators are notoriously inefficient, we built 2-phase heat electric convertors as a project and we managed to get less than 1% efficiency. We used dimetyl aether as a working agent and managed to get it running as low as 30C temperature delta, but the output was measured in micro watts. The main problem is, once you start taking power out, it disturbs the internal resonance and the machine stops. With actively guided stirling (displacer moving working gas), it's much more resilient and doesn't stop that easily.
Click to expand...

Thx VooteleAer

I don't know if you looked at this other videos like his but his workmanship and technical ability is great.
ie: His chances of success are better than most with some clicks and likes etc to help.

I'm no expert either. Far from it! :)
But this guy is talking about working up to 30%!? IIRC he mentioned Helium as a working medium for that .
He certainly is talking higher delta Ts though.

Also keep in mind that if you are using the space and weight of/in a bicycle frame it does double duty..!
That improves the overall efficiency of the system (bicycle) as a whole, rather than just the efficiency of the generator...
 
This is our Heat Electric Converter, one of many prototypes we built. It has really simple principle. There's hermetically closed casing with membranes at both ends. Inside the tube are hot and cold heat exchangers and regenerator between them. The exchangers consist of fine copper honeycomb (1.5mm eye) surrounded by brass ring and water jacket. The regenerator is basically a fine ceramic mesh disc, like the one in car DPI. And the chamber is filled with dimetyl aether vapour, which vaporizes at the hot end and condenses in the cold end. This creates steady 30Hz vibration in the machine. The membranes can be tensioned and tuned to specific frequency and act like a ping-pong device. One membrane has some magnets and coil for power output. The whole device is suspended with leaf springs. Of course aether is fairly agressive chemical and it tends to degrade many rubber and plastic materials, like the nitrile rubber membranes - they will stretch out like a rubber bag if the machine is not properly vented after the experiment. And we found one old prototype that still had some aether in, the membranes just crumbled away :D
I had this idea building a linear stirling generator - the working piston (or membrane) has just some magnets and coil, but the working gas ( or fluid) is moved between cold and hot end by electromagnetically driven displacer. I even built a quick and dirty prototype of such displacer, using a coil from speaker (without the cone or springs), to test power consumption. It kinda worked, but needed many improvements on build quality to make it useful. I think the best version could be built using hard disk head/magnets with some foam sector attached at the other end, and moving in the casing like a pendulum.
 
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Logic11 said:
Thx VooteleAer

I don't know if you looked at this other videos like his but his workmanship and technical ability is great.
ie: His chances of success are better than most with some clicks and likes etc to help.

I'm no expert either. Far from it! :)
But this guy is talking about working up to 30%!? IIRC he mentioned Helium as a working medium for that .
He certainly is talking higher delta Ts though.

Also keep in mind that if you are using the space and weight of/in a bicycle frame it does double duty..!
That improves the overall efficiency of the system (bicycle) as a whole, rather than just the efficiency of the generator...
Click to expand...
I was talking specifically about thermoacoustic stirling engines.
The regular stirling can be even more efficient than 30%
However, it needs very large temperature delta to achieve this
 
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1st: Great prototype with the evaporation and condensation added!
I had a look at your YouTube channel but searching "thermoacoustic" and "stirling" both draw a blank.

VooteleAer said:
I was talking specifically about thermoacoustic stirling engines.
The regular stirling can be even more efficient than 30%
However, it needs very large temperature delta to achieve this
Click to expand...
Unless I misunderstood him, so is he!
ie: He said there is at least one (in a lab?) somewhere that is 30% efficient.

Either way, he's doing good work worthy of a few likes etc :)

I like that an existing bike frame can likely do double duty as a thermoacoustic stirling engine.
 
Logic11 said:
ie: This is a 30% efficient, (in some models) pretty quiet conversion of Gasoline, Diesel, Kerosene, whatever, into electricity!
Click to expand...
Plutonium-238

A really hot compost pile

Bunch of angry cats in a sleeping bag

McDonald's coffee

The cool thing about Stirling engines is they only need heat, not combustion. I've seen little ones that go nuts when you set them on top of a hot drink, and even one that would run from the heat of sitting in the palm of your hand.
 
Chalo said:
The cool thing about Stirling engines is they only need heat, not combustion. I've seen little ones that go nuts when you set them on top of a hot drink, and even one that would run from the heat of sitting in the palm of your hand.
Click to expand...
They look cool, yes. But you do have to keep in mind that energy isn't created, just channeled into rotational movement. Think about how much heat comes off the top of a hot drink, and think about it in terms of watts: 2 or 3? Maybe 5, at the most? Certainly enough to turn the wheel of that cute toy, not much useful after that.


Which isn't to say there aren't huge and powerful stirling engines out there, there certainly are.
 
harrisonpatm said:
They look cool, yes. But you do have to keep in mind that energy isn't created, just channeled into rotational movement. Think about how much heat comes off the top of a hot drink, and think about it in terms of watts: 2 or 3? Maybe 5, at the most? Certainly enough to turn the wheel of that cute toy, not much useful after that.
Click to expand...

Yes, size must match the load. My point was they don't need to breathe air or consume anything other than heat, to run. If you can make one side hot and the other side not-hot, a Stirling engine will go.
 
Chalo said:
Plutonium-238

A really hot compost pile

Bunch of angry cats in a sleeping bag

McDonald's coffee

The cool thing about Stirling engines is they only need heat, not combustion. I've seen little ones that go nuts when you set them on top of a hot drink, and even one that would run from the heat of sitting in the palm of your hand.
Click to expand...
That's altogether possible. Even Probable.
But this guy isn't letting those who say it's impossible get in his way! :)
He is talking about the existence of obscure and 'confidential', 30% efficient ThermoAcoustic versions producing 4.5kw here:


I have no intention of going down a ThermoAcoustic Stirling Generator 'rabbit hole', but this guy is, as a hobby, and I am glad. and wish him every success! :)
Also I'm happy to help a little by liking his posts and subscribing to his channel etc.
He does good work and interesting!

If an (almost) stock bicycle frame can be made to produce electricity from gasoline etc somewhat efficiently for next to nothing in extra weight etc; that's a win for us all.
So here's his latest video! :)
 
There's some really good Peltier thermoelectric generators available, which in my experience beat thermoacoustic stirling generators left and right.
As for stirling generators, I think the weak link is rotation. You really don't need to convert linear movement into rotation in order to generate electricity from it. It's far more efficient just to attach a coil and magnets onto piston and convert the movement straight to electrical energy.
 
VooteleAer said:
There's some really good Peltier thermoelectric generators available, which in my experience beat thermoacoustic stirling generators left and right.
As for stirling generators, I think the weak link is rotation. You really don't need to convert linear movement into rotation in order to generate electricity from it. It's far more efficient just to attach a coil and magnets onto piston and convert the movement straight to electrical energy.
Click to expand...

IIRC thermoelectric generators are at around 7% efficient? That's er... 'a little low', but no moving parts is a big +
(Relevant here is the fact that micro ICEs have a lower efficiency than Peltiers below around ~7cc and ~500w.
Sci-Hub | Scaling of Miniature Piston-Engine Performance, Part 1: Overall Engine Performance. Journal of Propulsion and Power, 29(4), 774–787 | 10.2514/1.b34638
Sci-Hub | Scaling of Miniature Piston Engine Performance Part 2: Energy Losses. Journal of Propulsion and Power, 29(4), 788–799 | 10.2514/1.b34639
(Sci-hub is your friend if the papers you want to read are paywalled)

I'm more taken with the fact that this generator is mostly 3 hollow tubes in a triangle, same as a bike frame,
which is why I posted. :)
That's close to zero added weight and construction to get a part everyone already has anyway, doing DOUBLE DUTY! Which has a positive effect on the unit/bike as a whole.

I agree that a linear coil is most likely like a far better bet. (You or I? should post at much in his Youtube comments)
This seems to be more about a generator anyone can make with minimal tools atm.
I don't think it'll be in his final iteration.
Another resonant circuit, electrical coil and cap this time, might be best?
I don't know that I have ever seen or heard of a resonant power generating circuit though..?
 
Resonant circuits exhibit ringing and can generate higher voltages or currents than are fed into them. They are widely used in wireless (radio) transmission for both transmission and reception.

Resonant circuits can generate very high voltages. A tesla coil is a high-Q resonant circuit.
Electrical resonance - Wikipedia

No talk of higher POWER (volts x amps) though..?
 
You can't get higher average power out, though you might get peaks of higher power (with proportional lower ones to make up for it). The average power will be lower than the average power in, by however much efficiency loss there is.
 
In my experience, thermoacoustic stirling engines are less than 1% effective, I have no idea how this guy managed to get 30% out of it. If true, it should be a revolution in power machines, but I suspect there's a catch somewhere
 
We had this idea of making "organ pipe" type acoustic generator. Basically you use compressed air blown into a resonant tube and take the energy out with a membrane and coil.
 

Active Stirling Engine

Micro Combined Heat and Power systems or microCHP systems generate heat and electricity for a home. Stirling engines are widely used as prime movers in microCHP applications. Stirling engine is an external combustion engine having an enclosed working fluid (as helium) that is alternately...
ir.canterbury.ac.nz ir.canterbury.ac.nz
 
VooteleAer said:
In my experience, thermoacoustic stirling engines are less than 1% effective, I have no idea how this guy managed to get 30% out of it. If true, it should be a revolution in power machines, but I suspect there's a catch somewhere
Click to expand...
This paper combined a Helmholtz resonator with a Piezoelectric 'collector' to get 38% efficiency.
Pity it's in the microwatts. :)

At a wild guess I would say its all about getting everything from the sound to the piezo contraption to the electrical circuitry all resonating at the same frequency and/or octaves..???
It seems that various things there were tunable to get resonance everywhere.


I NB that there is no flow through a Quarter Wave or Helmholtz resonator in a car/engine exhaust, which means the 'end' stays at around ambient temperature.
That means that a normal speaker might survive inside them.
There's no shortage of DB in engine exhaust!
Think vented, (opposite) tuned bass speaker box, but with both sides 'vented' into the exhaust.

Question is; will it increase a car's power to weight ratio (vs alternator) = be worth it?
I doubt it. (unless it doubles as an efficient muffler)
Not a 'rabbit hole' I'm going to go down atm.
 
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