(* Interesting post from another group *)
> From: "Paul Phillips" <cptrdbrd@yahoo.com>
> To:
wastewatts@yahoogroups.com
>
> Hi all
> I have been tossing around the geothermal idea for a some years
> and I am getting closer to starting work. wile doing some research
> on well drilling, I came across "driven well" this is where you use a
> special made point that threads on the end of galvanized pipe and
> you drive it into the ground up to 100-150 ft. they usually have slots
> or holes to let water into the pipe at the bottom.
> My thought is not to have the holes in the bottom. all so then you
> made a manifold on the top to allow you to make a sort of tube in tube
> heat exchanger, you could run say 3/4" pex with 1/4" of closed cell foam
> down the middle. this would give you a closed loop design. if you could
> do multiples of this like a spider design to 50-100" you may not have to
> drill expensive wells.
>
> Paul
Paul,
I have a portion of a manual called "Drilling Methods for shallow geothermal installations", that was written by a Swedish Geology Prof named Olof Anderson, date unknown.
From studies conducted in the early 1980's, they cite rammed (AKA: driven) co-axial (AKA: tube-in-tube) steel tubes as one of the possible methods for GSHP installation. Corrosion seems to be a problem. Regular steel has a mass loss of 2.15% per year and is estimated to be good for 32 years, copper has a mass loss of 1.74% per year with an estimated life of 40 years. Stainless steel appears to have negligible mass loss and is expensive.
* please see attached scans *
Regards,
-AC_Hacker