Dear Forum,

I have run across a very interesting machine that I was wondering if someone might could comment on. It is a version of the Sterling Engine, that uses a turbine instead of a piston. They have just completed phase I testing, and say it was successful.

The forum won't let me post a link; but just google Kender Solar, and it will come up.

They claim that the energy extracted by the solar panel produces more energy than what it takes to drive the compressor to circulate the helium, and results in: "The system produces 39 kW of power (47 kW by the turbine, less 8 kW for the compressor). That is equivalent to 53 horse power, or enough energy to supply energy for 12 homes."

Does this sound theoretically possible? Any comments would be appreciated; or please forward to anyone who might could comment.

Thank you, and have a blessed day!

Sincerely,
Thomas M. Edmonds
Christiansburg, VA

They are claiming a cycle between 293K and 33K at up to 200 atmospheres with helium as a working fluid.

Their definition of "Phase 1" is to spin a turbine and power a compressor from the energy in previously compressed helium.

http://www.kendersolar.com/index.php/The-s...ne-Phase-1.html

The technology is known and the gross concept is not patentable.
http://en.wikipedia.org/wiki/Turboexpander

Helium is the leakiest of all fluids. Very few substances can lubricate at 33K. 200 atmospheres is an insane operating pressure for a residentially emplaced device. They don't have a conventional cold reservoir. They depend on the pump to keep the cold side at abysmally low pressures.

Some people might be familiar with the Joule-Thomson effect which says that Helium cannot be expanded at constant enthalpy above its inversion temperature of 55K, but this is describing a free-expansion through a nozzle. In a turboexpander the gas does work. So I can imagine that the gas would get quite cold over a 199 atmosphere drop in pressure.

But while "Phase One" might look impressive, I don't believe that material science will allow the commercial development of such a system.

Such an engine doesn't make sense to me, for the same reasons: lack of cold source, compressing without elevating the temperature, and so on.

Any cold source below ambient temperature (or even: not too much above, in fact...) is very difficult and weak. The focus of a radiotelescope is such a source, it can absorb something like 1e-12W. That's why all thermal engines start from temperatures well above ambient.

And then, Neon or Argon would be less bad than Helium - though Nitrogen, or boiling CO2, or boiling water are excellent candidates. By the way, an expansion speed acceptable by existing turbine alloys is always better, and speaks against Helium as well.