Either a bit of an RE twist or a crazy idea.
Gary will have to decide.
Places in the US south west use geothermal for A/C. It raised the ground temperatures in some areas.
Here, and anywhere it gets down to -20, A/C is probably a low priority except for a couple weeks a year? More worried about heat.
If doing all that digging anyway, why not trench a few strips 3' deeper, lay in some cheap black plastic pipe.
A small cheap solar drain back system to heat water starting in maybe mid June, and run it through the deeper pipes to raise the localized ground temperature.
It would not take much cost or complexity to move a whole lot of summer BTUs down there into storage for winter use.
I would think it could increase the ground temp considerably, thus increasing the heating efficiency.
G-
Hey Glen,
That seems like a sensible idea to me.
We were looking at a new home for sale here in Bozeman the other day. It has a big geothermal field, and solar collectors. The builder was there and we talked about doing just what you mention. I offered to help with the numbers, but have not heard back from him as yet. He seemed very interested in the idea (which he had already thought of himself independently) -- he liked the idea that very little extra cost is involved.
Heard another interesting idea for in ground heat stores.
The idea would be to basically enclose a fairly large chunk of earth in an insulation "umbrella" (a bit like the PAHS homes). You would normally think about doing this by digging up a good sized area, installing the poly pipes to add and remove heat, then insulating the sides as you backfill, and putting an insulation lid on then more backfill. Lots of digging a labor and mess.
This persons idea was to not disturb the earth that is used for storage. He wanted to install the poly tubes with one of the gadgets that kind of plows them through -- a heavy vehicle basically pulls the pipes through behind a blade that penetrates the earth.
Then dig a narrow trench around the periphery and insulate it -- this might be done with a heavy duty trencher. Then install insulation over top -- presumably with a layer of dirt and grass over it.
This would be heated with solar collectors starting some time in the summer.
Heat would be extracted in the winter and distributed to (say) a radiant floor in the house.
Seems like two things tend to make seasonal heat storage tough to do successfully. First is the relatively high heat losses of homes -- even new ones built to code -- you need something that is well on the road to a Passive House Institute level of insulation to have a chance to store enough heat in the summer. The other thing is the cost of putting in the very large storage -- which your idea and the other idea might address.
Its not easy even with a well insulated home:
http://www.builditsolar.com/Projects/SolarHomes/SandBed/RamlowSandbed.htmBut, your thought on adding heat to a geothermal field that is already there is really cheap to implement, and cheap to run -- just a circulating pump.
In the same general area, the Drakes Landing folks seem to be doing pretty well with their project:
http://www.dlsc.ca/They are predicting being up to a 90% solar fraction soon.
Gary