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Tapping the Earth For Home Heating and Cooling
suraj.sun recommends a CNet post giving details of a still little-known energy technology: the ground source heat pump or geo-exchange system. This is distinct from so-called geothermal energy, which taps the heat in the earth to provide energy. Geo-exchange is suitable in scale for small industry — the article describes one commercial re-development of an old mill into apartment and commercial space that put in a geo-exchange at about half the cost of traditional fossil fuel-based alternatives. Even some individual homeowners are opting for this green method of heating and cooling, at a premium in price of about 50 percent (but costs are very much per-project, largely because drilling is involved). "Rather than use underground heat, geothermal heat pumps attached to buildings capitalize on the steady temperature of the ground or deep water wells. In effect, they treat the Earth like a giant energy savings bank, depositing or withdrawing heat depending on the time of year. "
Its been around since at least the 1940s. The building I live in (downtown Austin) uses it and it was built in 1938.
I bought a house in Minnesota (cold winters, hot summers) that was a part of a pilot program in the 80s by Northern States Power (now Xcel Energy), whereby the installation cost was subsidized by NSP for this home and a handful of others.
Upon learning about this from the previous owners, I was naturally concerned about the system's efficacy at heating and moreover cooling the split-level home as compared to traditional gas furnace and air conditioning. It wound up performing identically on both counts, providing as much heated or frosty air as desired seasonally, all for only the price of operating the heat pump; I believe the annual electric cost was roughly $80/year.
To top things off the house was furnished with a traditional gas furnace as a safety backup.
Recently we installed a new furnace (Ontario, Canada). My wife and I had it priced out.
Turns out that although there were several grants we could receive, totalling $7000 approximately, it was still not worth it.
By the time all was said and done, it would have cost $30k to install. They would have torn up our lawn, which would have necessitated new landscaping. They also couldn't guarantee that they wouldn't crush our water and sewage lines with the drilling trucks.
All in all, it wasn't 50% more expensive. After rebates, it would have been about 4 or 5 times what a 96% efficiency natural gas furnace cost us.
You can accomplish anything you set your mind to. The impossible just takes a little longer.
Side note to the OP, the phrase "geothermal" to most homeowners does mean ground-source heat pump technology, not the stuff they use in Greenland.
I have a modest 2000sqft home in northeastern PA (Poconos area, I'm 8 miles south of Camelback ski resort). I had two contractors out to quote ground-source DX (direct exchange) systems, and both quotes were in the mid-$20k range. Too rich for my blood.
I went with a Hallowell cold-weather heat pump for pleasantly less than half that. The Hallowell is mostly sold in Canada and upper New England, but it's been slowly working its way south. When I called them to ask about my application, the guy laughed and said "Man, you're in the tropics!"
It's only been running for a few weeks now, but I've been very impressed so far. It hit -3F two nights ago and the heat pump still ran entirely off the first compressors in stage 1 (stage 2 was still not needed). The air coming out of the vents was warm to the touch. In fact, the system has yet to resort to resistance heat down to -3F exterior temperatures. We keep our house set to 66F. I've been able to kick the heating oil furnace and storage tank to the curb. No more timing oil pre-buys against market prices, no more noisy power venters, no more oil storage tank taking up basement space, no more yearly burner tuneups and vent pipe cleanouts. I even get nice 18 SEER air conditioning to replace my builder-grade central air conditioning unit.
Pictures of the complete home renovation are at:
my house renovation
The entire system is on a dedicated subpanel, and I've put a subpanel meter on it to measure total kWh usage. This will allow me to directly measure operational cost each month.
Another factor that steered me away from ground-source is balancing the break-even time versus the system lifetime. If it takes me 20 years to break even on the ground-source and the system needs replaced not too long after, I haven't really gained anything. If the Hallowell takes me 7 years to break even and the system lasts 2-3 times longer than that, I've saved quite a bit of money. Break-even isn't everything; it has to be balanced against the expected lifetime of the system. Plus, I'd have to factor in the cost of repairing the yard after the loops were dug and installed. They claim that just a 3' circle of ground is disturbed to drill the loops, but one of the guys eventually admitted the machines rip up the yard pretty bad as they drive around the hole to drill the loops at different angles.
I found the guys at Hallowell to be very helpful to talk to. I don't work for them and I have nothing to gain. I simply speak as a satisfied customer. For new construction, rolling a ground-source system into the mortgage would be the way to go. For my existing construction with an established yard, simply setting the Hallowell on an outdoor pad was an excellent path forward for me.
- Chris
I to live in Florida and have a ground water heat exchange system produced by ColdFlow. http://www.coldflow.com/
My system is old enough I don't need to used an enclosed loop. Nice thing about that is every time the unit is running my yard is getting watered too. These systems are very efficient and with being in a cinder block house my electric bill runs about $100 a month.
We've been getting virtually free heating and cooling on our 64,000 cubic foot storage building for 20 years. We simply ran a 30 foot extension from the drainage tile in the neighboring field and put a fan on the end of it. Constant 60f air. Paying electricity for a medium sized fan beats the hell out of $3,000+ heating bills in February when it gets and stays below zero or August when it gets above 100f.
If a farmer could hack this together from spare parts 20 years ago, I can only hope that the technology has gotten much better since then.