[GSBN] ground source heat pumps

[Tom Hahn]

Hi everyone - I echo David's considerations, and add one that's 
pertinent here in the southwest US...

Low soil moisture content...  Apparently, no matter how temperate the 
soil is, if the soil is quite dry (at coil burial/drill depths) then 
the heat transfer coefficients with the coil will also be low.  So, 
more coil for the same amount of heat transfer potential is 
necessary, raising digging/drilling and coil costs.

Generally, I've seen the best locations for geothermal heat pumps are 
places that have relatively cool soil temperatures, higher soil 
moisture levels, and easy digging/drilling soils.  Of course, all of 
that is obviated by a pond that can be used, but "natural" ones 
aren't very common here in Arizona, so we haven't been able to try 
that.  However, on a consulting project, we discussed integrating a 
GSHP coil into a large swimming pool at a resort (though that has its 
own environmental impacts...).

Tom


>Dear colleagues -
>
>Can someone shed some light on so-called geothermal heating systems, 
>and their cost-effectiveness for a typical home?
>
>I imagine the pay-back in energy saved has something to do with how 
>many heating degree days in a specific climate.  But then, I 
>understand they can also be reversed for cooling.
>
>This seems like an expensive technology that is dependent on 
>electrical service... can it be powered by solar/
>
>Thanks for any insight offered.
>
>
>Sincerely,
>Catherine Wanek
>Co-director
>Builders Without Borders
><mail at builderswithoutborders.org>
>www.builderswithoutborders.org
>575-895-5400