Hydrothermal well

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Retired Defense Industry Engineer xxx
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New England
I'm putting together some ideas for a house I might someday build. I'd like it to be energy efficient, and a couple of things that come to mind are solar for some electricity with battery storage, and hydrothermal for heating and cooling. I would like to do an earth-sheltered building, so the HVAC loads would be small.

I've just started to research a little on hydrothermal. Where I live, electricity is fairly expensive, and NG isn't available everywhere, plus, it's a fossil fuel, I'd like to avoid. Propane is worse, and even more expensive. But, I think solar with some battery storage might make that almost free (obviously, the upfront costs could be substantial!).

Most places don't have much of a soil cover, so buried loops probably wouldn't work. Not that many ponds or lakes in the area I'm thinking of, so submerging it there probably wouldn't work, and warming the water of a smaller one might be an issue. So, that leaves drilling a well. We are called the Granite state for a reason!

It seems like something about 650' or so deep would provide enough water volume for HVAC. I'd like to also do a snow-melt, as I'm getting older, and shoveling or plowing a driveway and sidewalks, or paying someone to do it (nicer to have them always clear of ice and snow!) is harder to find reliable, affordable help.

Anyone point me to resources that give an idea of the volume of water required in a recharge type well (you return the water you pull out) per say ton of cooling or heating? In the general area, according to the Feds, water depth is typically less than 10' down in my area, but of course, that could vary plot to plot, but as an average, in a 650' well, that would leave 640' column of water, not counting whatever may be passing through.

It would be nice to not have to heat it at all, but while there's areas in NH that are considered hot enough for energy production (radioactive decay in the native rocks), the required level is WAY deeper than you could reasonably drill a well, at least as a homeowner. It's over 200C north of me, but at 13Km down! In something practical, probably about 10C at 650', depending on the season.

Anyone have any experience with this sort of thing here? Until I actually design something, don't know what amount of energy I'd need, but trying to get a feel for it.

From some of the limited research I've seen, for say a 2000sqft home, costs average $10-40K, depending on whether it's a retrofit (cheaper) or new construction, and payback typically can be in the 4-7 years depending on the local electric costs...making your own it would almost be free, so it would end up being whatever your costs to build it or finance it, not a recurring utility cost.


Cary Austin
Staff member
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Lubbock, Texas
Do a little research on a standing column well. You will need a certain amount of bleed to keep the well from banking up the cold. The bleed water will have to go somewhere? Switching from gas to batteries is switching from fossil fuels to mining rare earth materials. Neither of those things would be a problem if there weren't too many people for the planet to sustain, which is the real problem nobody wants to admit.
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