Thermoacoustic generator

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nlc
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Thermoacoustic generator




by nlc » 29/03/08, 19:17

Well, I throw this here, I haven't super deepened, I don't have the time, but you will be able to do it because the subject seems very interesting to me:

We know that on 1000W per square meter of solar energy, with a photovoltaic panel we do not recover much (yield between 10 and 15% approximately, is that right?).

In addition, photovoltaic cells are expensive.

On the other hand, a solar thermal collector is cheaper and it recovers solar energy better. The problem is that it is in the form of heat, which is difficult to transform into electricity. Some do it anyway, with solar concentration and a Stirling engine coupled to a generator.

But it's really complex and expensive because of the mechanics in motion.
there is also a way to convert heat with a peltier module, but we saw on another subject that the efficiency is poor

Not long ago, I was told about the thermoacoustic effect, which I didn't know about. Glass blowers discovered this, basically a difference in temperature can cause a sound.

By a stationary resonance and wave system this sound can be used to make cold, or generate electricity.

There are also refrigerators using this process. But since it is reversible, we can therefore generate electricity from a temperature difference.

I have not yet fully understood the principle, but from what I have understood, as the sound is a succession of pressures and depressions, the temperature of the gas varies in pressure dips and peaks.

With the effect of resonance and standing waves, we are left with a carnot cycle and the equivalent of a stirling engine but without any moving parts.

Basically, with this system, if a sound is injected, it extracts heat from the cold source to the hot source (operation in a refrigerator). And if we do the opposite, if we put a hot source on one side and a cold source on the other, it produces a sound that can be converted into electricity.

I let you dig a little more but by flanneling quickly on the net I saw that there were already a few researchers on the spot. I also saw students working on the phenomenon, and it turns out that it is very easy to implement!

I do not know if I will be able to follow a lot and participate in the subject because I do not have much free time, but I will try anyway!

A read! :D
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by nlc » 30/03/08, 01:17

An interesting starting point, and a demonstration video a little further down the page: http://www.io.com/~frg/
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by bham » 30/03/08, 19:22

Hat for your tenacity and the transformation of your motorcycle.
http://chaenel.free.fr/cmsimple/?Econom ... 9lectrique

It is true that to make Savenay / Nantes by the fast track, it is better to pass to the higher level.
Do you plan to take it to the Mines when you finish?
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by nlc » 30/03/08, 19:31

Yes ! 8)
In fact I have not much choice because it is a 500 and I do not have the motorcycle license, I must imperatively succeed in homologating it in the 11kW (15hp) category, to drive it with the car license.
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by Capt_Maloche » 30/03/08, 23:16

Hat for work on the motorcycle chassis
I can't wait to read more

For thermoacoustics, I had read an article on the subject
we must go further on the subject, I did not understand everything
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by nlc » 31/03/08, 08:24

I started to understand what is happening, but then in terms of the calculations that we want to see, there I capture a belin .....: Cheesy:

Basically on the acoustic wave, in the pressure peaks the gas rises in temperature and provides heat to the boundary layer of what they call the "stack", and in the pressure troughs the gas cools and extracts heat at the boundary layer. And then it works step by step, like a row of volunteers passing buckets of water.
On one side of the "stack" we put the hot exchanger, on the other the cold exchanger.

It is pretty well explained here: http://thermoacoustique.free.fr/

The "stack" is in fact a multitude of thin plates stacked to let the sound pass but to create boundary layers (a kind of skin), which will allow the heat to be conducted.

On this site he uses a catalytic converter ceramic, and on another site they made it with a film of a few microns wound on itself and whose windings are spaced by fishing line.
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by Capt_Maloche » 31/03/08, 10:01

Yes, I understood correctly in theory, it is necessary to grant the frequency to the step of the exchanger

and the higher the pressure, the greater the amplitude

basically, a HP in a closed volume under pressure and an exchanger whose pitch is adapted to the frequency envisaged, with a hot step and a cold step, at apparently, it is reversible

http://thermoacoustique.free.fr/

But where I pick up, it's on the link that you give above, with plates that are heated, there comes out a tension directly and, if I read correctly, it is piezzo

Solar application:
http://www.ginjfo.com/Publics/Actualite ... C3%A9.html
According to Symko, such a device could optimize the performance of solar panels which currently varies between 20% (for the mass market) and 40%, and could then be increased beyond 50%.

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Last edited by Capt_Maloche the 31 / 03 / 08, 10: 39, 2 edited once.
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by nlc » 31/03/08, 10:12

In fact the effect is reversible, so rather than sending a sound in the system to create cold, we can exploit the difference in temperature hot source / cold source to create or amplify a sound, which then creates current by l 'intermediary of a kind of HP or a piezo.

http://www.io.com/%7Efrg/history.htm
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by Remundo » 31/03/08, 12:12

Hi Nlc and Captain Maloch!

Capt_Maloche wrote:Solar application:
http://www.ginjfo.com/Publics/Actualite ... C3%A9.html
According to Symko, such a device could optimize the performance of solar panels which currently varies between 20% (for the mass market) and 40%, and could then be increased beyond 50%.



"The efficiency of converting sound waves into electricity is quite good, only 20% of sound energy is lost, on the other hand the overall efficiency, from heat to electricity, could be 20 to 25% according to Orest Symko . Indeed, the greater the temperature difference between the heat source and the cylinder, the better the efficiency. "

I look at the case ... You know that the hyperthermic trap of direct solar radiation (PHRSD, patent SYCOMOREEN) has 90% thermal trapping efficiency at 1000 ° C ...

I still fear that this system does not reach the performance of a good Stirling cycle. On the other hand, for an application in a private individual, it may be less effective, but more economical to buy because the manufacturing seems to be without moving parts ...

Finally in all this, I find that the conditional is too often used and the principle is not clearly stated ...

@+
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by nlc » 31/03/08, 12:43

Remundo wrote:Finally in all this, I find that the conditional is too often used and the principle is not clearly stated ...
@+


Look on this page: http://thermoacoustique.free.fr/effetth ... stique.htm

The explanations are succinct but we end up understanding how it works.
And look at the experience at the bottom of the page: a test tube, a piece of ceramic recovered in a catalytic converter, a heating resistance, and the assembly spits 100dB!
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