View Single Post
Old 12-07-2012, 01:56 AM   #3 (permalink)
Christ
Moderate your Moderation.
 
Join Date: Nov 2008
Location: Troy, Pa.
Posts: 8,919

Pasta - '96 Volkswagen Passat TDi
90 day: 45.22 mpg (US)
Thanks: 1,369
Thanked 430 Times in 353 Posts
That's basically the idea. The temp is relatively stable at 30" below the soil depth, and it's even moreso here because the water line is less than 3" below deck at one particular point.

The air temp, however, is basically never stable at 50* for any length of time here... it's almost always above (way) or below (somewhat).

Since the engine can work (I think) with either a positive or negative differential, I imagine (based on that) that it will work even if the air temp is below the ground temp, so the "changeover" period being as short as it is, could be overcome with a temp switch on the generator and a large flywheel to keep the motor spinning with no little resistance until it can produce power again (say, at a 5* temp difference).

Of course, to produce any power from such a small temp difference, it's going to have to be a physically massive version of the sterling motor (comparatively), but I've seen designs (for school projects and such) that produce as little as 1w at a temp differential of as little as .5*C (4*F).
__________________
"¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"

  Reply With Quote