Tesla's self-actuating generator

[HeairBear]

I have one like this... The power of temperature differential! Very cool!

[pese]

FWIW, I remember reading 10 or so years ago about a 17 year old South African lad who had devised a refrigerator using Stirling engine to pump the freon through the its coils. It was touted in the international headlines as the answer to Africa's refrigeration problems in areas where there was no electricity.  The lad's first name was Christian, I believe; I've forgotten his last name.  All of a sudden, the story disappeared, and I have not been able to find it at all on the internet. My guess is that the design was quickly bought up by a energy interests and even more quickly shelved.  My point is that your idea may be worth further exploring, and the Stirling engine application may work well with it.  There's no reason why it shouldn't work.  I believe Groundloop has posted a design for a Stirling engine on a thread about 8 months ago. If I find it, I'll post the link.
Bob Smith

Why not.

See to the compressorless frigudaires.
that work only with an s,all heat-source.
loke 60 watt electric heater - like an small gaz-flame !
why not solarheat (in adrika shure the cheatest source ...
as transfer gaz, you can also use buta filled inside the tubings wit 2.2 bar !

Pese

This technik is not belived by industry, because to simly ...

[Thaelin]

   The stirling motor can be ramped up to a very sizeable  unit. In a location
where you have high heat, they work great. Never understood why they are
not more put to use. Even if you were where it is fairly cool, a solar reflector
to the right spot on it will make it fly.

thaelin

[tinu]

I found an interesting idea for a PM machine suggested by Nikola Tesla, see if you can find a flaw in it...

Interesting idea as a mind exercise but unfortunately not feasible.
Something is wrong in math. It boils down to nasty sums (or integrals) but spreadsheet may be helpful. Check the quoted part again, please:

If instead 5 heat pumps in series are used to pump the heat out, at a temperature gradient of 50K each, they will have an overall COP of 0.5 and will use 16.7/ 0.5 = 33.4J to keep the heat sink at 50K.

I assume you missed to increment the heat to be removed starting with the second pump in series. The first one indeed pumps 16.66J but the second one pumps more (33.33J), the third pumps even more by again adding 16.66J  and so on.

Cheers,
Tinu

[jandell254]

Thanks for all the replies.  I really think this machine works in principle, and after a few engineering challenges have been overcome I'm sure it could work in practice as well.

Interesting idea as a mind exercise but unfortunately not feasible.
Something is wrong in math. It boils down to nasty sums (or integrals) but spreadsheet may be helpful. Check the quoted part again, please:

There is no difficult maths involved, just use a few different values of Tc and Th to get an idea of the efficiency of the heat pump and the heat engine at different temperatures.  

I assume you missed to increment the heat to be removed starting with the second pump in series. The first one indeed pumps 16.66J but the second one pumps more (33.33J), the third pumps even more by again adding 16.66J  and so on.

Cheers,
Tinu

No, 16.66J is the total energy used by all 5 pumps, each individual pump has an average COP of 3.  I actually made a small mistake in my first post, I was in a bit of a rush.  The calculations for the COP of the 5 pumps in series are shown below:

Pump 1: COP = Tc/(Th-Tc) = 50 / (100 - 50) = 1
Pump 1: COP = 100 / (150 - 100) = 2
Pump 3: COP = 3
Pump 4: COP = 4
Pump 5: COP = 5

Average COP of each individual pump = (1+2+3+4+5) / 5 = 3
Therefore the 5 pumps in series act like one pump, pumping across a temperature difference of 250K, with a COP of 3 / 5 = 0.6
So the COP is 0.6, not 0.5.  It actually makes the machine work a tiny bit better.

As for the use of Freon, that wouldn't work at the very low temperatures required.  Normal refrigerants like that can cool down to -40 Centigrade (260K), apparently.  Consider a temperature difference of say 40K, with Th = 300K and Tc = 260K.
If 5 heat pumps are used, the total COP will be 6.9.
The efficiency of the Stirling engine will be tiny: 1 - 260/300 = 0.13, or 13%.

With 87J getting past to the heat sink, it will take 87 / 6.9 = 12.6J to pump it out again.  You would only get 13 - 12.6 = 0.4J out for every 100J of heat energy passing through, and this is considering that your heat pumps/engines are perfect.

This means that very low temperatures are required for this to work properly, since Stirling engines and heat pumps are not very efficient in practice due to things like friction and other dissipative forces, so there are a lot of engineering problems to be overcome, and no low-powered test version can be made.

I wanted to show it could work in principle, hopefully once it comes to the attention of other people it will eventually be built by someone with enough money to hire the engineers to put the idea into practice.