Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Tapping the Earth For Home Heating and Cooling

kdawson posted more than 5 years ago | from the geo-exchange dept.

Power 215

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. "

Sorry! There are no comments related to the filter you selected.

"little known" ??? (5, Insightful)

Gothmolly (148874) | more than 5 years ago | (#26508423)

Ah yes, kdawson.

This technology is HARDLY little-known, but places where people need lots of heating and cooling (the Northeast) are also places where electricity is uber expensive (thank you Greenpeace), so heat pumps aren't worth the $$.

Re:"little known" ??? (5, Interesting)

Wandering Wombat (531833) | more than 5 years ago | (#26508479)

Beat me to it.

I work in construction and land development in Western Canada, and every single project we work on uses geo-exchange systems, because we get huge tax incentives to utilize energy-efficient technologies (and as strata owners, we still get to charge standard amounts for utilities). This isn't a big city, and there's THREE places that offer geo-exchange services.

Maybe it's just "little known" where people "don't care".

Re:"little known" ??? (5, Insightful)

JWSmythe (446288) | more than 5 years ago | (#26508673)

    Actually, there are lots of people who have no idea that this can be done.

    I live in Florida, and very few people that I've spoken with know anything about it. I haven't been able to find anyone that installs it either, but I'm not looking so hard now that I don't own a house any more.

    There are quite a few interesting variations on this. I won't bother mention the well system, since that's what the article talks about. :)

    One was a dry system, where you simply needed a series of tubes (intentionally said for Sen. Stevens) buried in a horizontal plane at about 10' to 20' deep. You can pump a liquid for a heat exchanger, or even just air, to stabilize the air temperature at about 60F degrees. There are all kinds of options on this. A heat exchanger, or even circulating home air through have both been done successfully. Adding a small amount of outside air can raise or lower the temperature as needed. If 65F is too cold, say 10% outside air could raise that up to 75F.

    Another uses river or lake water. This would depend on your climate to if it would work really well. A friend of mine lives beside a lake that's between 20 to 30 feet deep. Her air conditioner also works very poorly. I introduced the idea of an open loop system, where it would pump water from the lake, through a coil and back to the lake. It would need some degree of large debris filtering, but not a lot (try not to suck up the Loch Ness monster). The coil at the house would simply recirculate just as the regular air handler in the house would, except the coils would maintain about 60 degrees because of the lake. When it's close to 100 degrees outside, and the lake water is in the high 60's at the bottom, a 75 to 80 degree house is a welcome temperature. :)

    Unfortunately, most people look at it as "but, everyone else has a .....". Some people were worried about a reduction in their resale value, because if they sell their home, now there's a "nonstandard" system there. Who would want a house with an almost free heating/cooling system?

    A freon free, low energy system, that takes advantage of the difference in air and ground/water temperature is a wonderful thing.

    This wasn't news, and I wanted to say so too, but people need to be exposed to the idea.

Re:"little known" ??? (3, Interesting)

TheLink (130905) | more than 5 years ago | (#26508815)

You could remove the need for debris filtering by having a closed loop at the cost of reduced efficiency.

For example you could fill a closed loop with water, and then put one end of the loop (with coils etc) in the lake, and then the other end of the loop either gets welded to the airconditioner coils (to help make the airconditioner more efficient), or is used as you suggest.

Of course you'd still have to clean the end stuck in the lake- stuff is likely to still grow on it.

Re:"little known" ??? (4, Interesting)

samkass (174571) | more than 5 years ago | (#26510469)

I recall reading about someone in Hawaii doing something like this in order to both generate electricity and clean water by essentially using the deep ocean as the heat sink then the temperature differential to generate electricity (and the condensation for water). Apparently once you got the fluid moving it took less energy to pump it than you could generate with the heat differential in a tropical ocean island.

Re:"little known" ??? (1)

gerf (532474) | more than 5 years ago | (#26510499)

People in this area, Midwest, often build ponds when they build a new house in a rural area, and lay a closed loop in the bottom of the pond for heating/cooling. The only thing people need to be careful about is how deep things freeze, either in the pond or with the in-ground systems.

Re:"little known" ??? (1)

sribe (304414) | more than 5 years ago | (#26508995)

The coil at the house would simply recirculate just as the regular air handler in the house would, except the coils would maintain about 60 degrees because of the lake. When it's close to 100 degrees outside, and the lake water is in the high 60's at the bottom, a 75 to 80 degree house is a welcome temperature.

60 degree coils would not even get you close to 75-80 in the house. Exchange efficiency, volume of air, number of BTUs coming in through roof & walls & windows & doors, yadda, yadaa. Not. Even Close.

Re:"little known" ??? (3, Interesting)

JWSmythe (446288) | more than 5 years ago | (#26510009)

    That would all depend on the size of the heat exchanger, and the duty cycle.

    If, for the sake of argument, the typical duty cycle of a functional unit is 50% with say 12sq/ft of surface area on the evaporator, at 45 degrees at the evaporator. If you had 60 degrees at the evaporator, but increased the size to say 24 sq/ft, and the duty cycle to 90%+, it should be no problem. Consider that a system like this would require a pump similar to a swimming pool pump or smaller, which most people that have pools run for 12 hrs/day every day. A system like this wouldn't need to run at 90%+, but it would have that ability.

    In reality, it's not even required to run a pump on a system like this. There's a university (I can't remember who off-hand, but a big one) that is currently using a system exactly like this. They don't run pumps, the entire system relies on convection. The cooling itself is free, where the should have huge chillers, lots of freon, and huge power bills. They do still require power to run the fans for circulation inside the buildings, but that's it.

    For an ad-hoc system, I made the assumptions of double the size for the "evaporator", and one 1/2hp swimming pool style pond pump, that was able to handle small debris, with a bypass. If convection did it fine, then the pump was a waste. Even still, when I estimated the costs, and I am good at providing complete estimates, it was less than half the price of purchasing a new HVAC.

    But, your arguments are valid, and a good example of why people aren't willing to step away from what everyone else has. "Oh, that could never work."

    The same could be said of a Peltier/TEC based refrigerator for your car, yet they not only work, but people are very happy with them. Oddly enough, everything I've mentioned is not theory, but working proven fact, that has been implemented. Unfortunately, not widely, because people are afraid to change.

Re:"little known" ??? (1)

jbengt (874751) | more than 5 years ago | (#26510405)

Most A/C unit water coils (nit pick: there is no evaporator coil where you're using water cooled by the river or lake instead of DX) are designed on a dT (temperature difference) of around 10F to 15F between entering water temperature and leaving air temperature for practical reasons. That would mean a 60F entering water temperature would result in a leaving air temperature around 70F. This is not cold enough to do a significant amount of cooling, assuming that you're trying to maintain an indoor temperature of 5F or 10F higher. Getting a lower supply air temperature creates problems by requiring a lot of rows and fins, resulting in higher air pressure drops, and/or a lot of water being pumped through the coil. If you try to cool with the higher air temperatures, you end up needing a lot more air, which means even bigger coils, more fan power, and more water flow.
There's another, more important problem with using 60F water to cool the air (unless you're in a very dry climate). The minimum air supply temperature you can theoretically approach with 60F water is 60F, but you cannot dehumidify adequately without bringing the air down significantly below 60F.

Re:"little known" ??? (3, Interesting)

squoozer (730327) | more than 5 years ago | (#26509493)

This technology is fairly well know in the UK and it's getting more popular everyday. The main problem with it is the cost of drilling (apparently it's about double the normal price at the moment because of the Olympic games - everyone that has a drill is down there laying foundations in Londons rubbish soil) as most people don't have enough garden to lay shallow pipe work. Longer term though if a lot of people switched to this technology we would need to upgrade the electricity grid.

Re:"little known" ??? (1)

JWSmythe (446288) | more than 5 years ago | (#26509629)

    Would we though?

    I don't know how it is there, but in the US an awful lot of people here run air conditioning, heating, and heatpumps (A/C that runs in reverse to make heat above 40F outside), that all run on electricity.

    There are some areas that do have a natural gas infrastructure, so they usually heat on that. I just haven't happened to live in too many.

    In the summer time, pretty much every building in the US has an air conditioner running, either central or a window unit (or sometimes both). There are exceptions to that too, but relatively few.

Re:"little known" ??? (3, Informative)

deragon (112986) | more than 5 years ago | (#26509787)

Since we are on the subject, Toronto did something similar at a larger scale: []

Re:"little known" ??? (2, Informative)

JWSmythe (446288) | more than 5 years ago | (#26510139)

    That's a beautiful example. And, they're still using the water for drinking, which is perfectly safe, since they're running it through a heat exchanger for the system, not using it directly. :)

little store (1)

zogger (617870) | more than 5 years ago | (#26510053)

A family I know with a little country store do their cooling in the summer with such a system, All home made and really easy. It uses an old window AC unit modified to use liquids with a few new plumbing pieces. They just pump cold creek water through it, then it goes back to the stream. Works perfectly.

Re:little store (1)

JWSmythe (446288) | more than 5 years ago | (#26510187)

    I don't suppose you'd have the opportunity to take some pictures, and diagram it for me, would you? :)

    You can make an initial contact to me through the form on my site. I'll respond from my regular email account.

mental diagram (2, Insightful)

zogger (617870) | more than 5 years ago | (#26510949)

I don't live in that area anymore and didn't take pictures, but I think you can get it with this mental diagram. It's easy, Just a cheap plug in water pump and they use the existing coil and the squirrel cage blower. You'll need to use adapters to match the sizes on the coil. I guess you could use like a cheap/small used swimming pool pump, I didn't see what they were using, they just said a "water pump", sitting on a little shelf alongside the AC unit in a box. It was remarkably simple. I didn't even pick up on it until I visited their store a few times (normal cool inside like it had regular AC running, small little store) and noticed the water pipelines dropping down from the back of the unit (you could see it from the parking lot), so I went over and checked it out, then asked them about it. The guy who owned the store just took the old AC when it died and modded it. The creek is around 40 or so feet away, runs year round, little trout stream in north georgia mountains, so it is more or less pretty cold even in the summer months. They just drain it in the winter.

Thinking about it, you could build one with a car radiator and a box fan (measure window to get sizes where you need to put it), same deal, just add the pump, then maybe a little sheet metal shroud to tidy it up so it looked good. I've been meaning to build one myself, we don't use AC here, but I water the garden so much with cold well water that I keep thinking..hmmm..might as well. Just anther project, and I was going to put an underground tap out there anyway to eliminate hundreds of feet of garden hose out on the ground.

Re:"little known" ??? (4, Informative)

Anonymous Coward | more than 5 years ago | (#26510807)

I to live in Florida and have a ground water heat exchange system produced by ColdFlow.
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.

Common in Finland (3, Informative)

AliasMarlowe (1042386) | more than 5 years ago | (#26508963)

They are also quite common in Finland. Usually, a network of pipes is laid about 2 meters below ground level in the garden as the thermal reservoir (in less extreme climates, one meter deep may be enough). They have higher capital cost than the air-to-air heat pumps, but generate less noise and continue to operate even in very cold weather - unlike most air-to-air units, which get into trouble below -20C.

Re:Common in Finland (1)

Gordonjcp (186804) | more than 5 years ago | (#26509103)

They're becoming more common in Scotland too. We have relatively cheap electricity provided by wind, hydroelectric or nuclear power stations, and we've got the space to spread these things out. They work, too. In Scotland's mild climate (never much colder than 10C, never much hotter than 20C) they work pretty well.

Re:"little known" ??? (1)

RandomChars (1455331) | more than 5 years ago | (#26509331)

Also in western Canada, the local university here uses river water for its cooling. Not really a geothermal situation I would guess, but still the same idea. I sort of wonder what the longterm effects of these sorts of practises will have on the environment down the road. Don't get me wrong, its probably way better than burning coal etc, but I still wonder.

Re:"little known" ??? (4, Informative)

Zadaz (950521) | more than 5 years ago | (#26510863)

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.

Re:"little known" ??? (5, Informative)

ach1lles (671687) | more than 5 years ago | (#26508531)

Its been around since at least the 1940s. The building I live in (downtown Austin) uses it and it was built in 1938.

Re:"little known" ??? (0)

Anonymous Coward | more than 5 years ago | (#26508589)

Yup, I have seen houses built in 1970s that had these. Also they are being built nowadays more and more. I would estimate that every home builder knows about the technology. They opt in for air heat pumps instead because of the smaller sunk cost though. (Some of the new models work still well even in sub zero conditions.)

Re:"little known" ??? (5, Interesting)

artson (728234) | more than 5 years ago | (#26508773)

When I built my house in 1985, I built a passive solar home (three sided, two-story concrete box with south facing glass and air conduits built into an insulated slab). We placed four solar hot water heaters on the roof as well. The house has repaid the investment many times over, but my one regret is that I allowed myself to be talked out of putting in a geo heat pump system. At the time the experts told me it was too expensive for the projected return. They were wrong of course.

I don't know much about accounting, but it has always seemed to me that carbon cap trading schemes are just a gigantic boondoggle that allow bad actors to continue acting badly. For my money, if governments (Canadian in my case) want to encourage green technology and lower the country's carbon footprint, then they need to very strongly encourage geo heat exchangers in new construction and particularly for green renovations. Solar heating is not always possible, especially this far north, but geothermal exchange is always there.

As a post script, for anyone thinking of installing solar hot water panels on their roof, think again. If it is possible to mount them at ground level on a rack, you achieve two things: A. no holes in your expensive roof, and B. it is much easier to maintain them at ground level.

The good news is that you are SO wrong (3, Insightful)

WindBourne (631190) | more than 5 years ago | (#26509603)

The heat pump that you are talking about has the condensor in the air. That is a horrible choice because yes, parts of the east (and midwest) can hit -40F (or C). If you are heating to say 70F, then you are looking at 110F difference (or ~50C). That IS inefficient and you are better off just doing straight heat from electricity.

But a geo-thermal HVAC is different. The condensor is piping that is 5-10' down in the ground. The temps are around 55-60F. IOW, you are pulling with maybe 18F/5C range. That is EXTREMELY efficient. In fact, if American were on these, our cooling in the summer would use something like 25% less electricity and our heat bill for the majority of the US would be a fraction of what it is. Even here in Colorado, a front range home who spends 150 for gas heating (a cold month) would expect to only pay about 50-60 for the heating.

One of the nice things about this, is most of the east coast's fuel oil actually comes from Venezula. If the east coaster would switch to this, we would see our imports from Venezuela drop to about 1/4 to 1/3 of the current amount (Venezuela oil is apparently low grade with lots of sulfur in it; pretty much used for diesel and home heating oil). BTW, EU makes heavy use of Russian natural gas for heating (which is why these games come into being during these times). The best thing that the west can do is move homes to geo-thermal and for American insulate better.

Re:"little known" ??? (1)

rasjani (97395) | more than 5 years ago | (#26510343)

Maybe its the Euro thang ... you know, those pescy 's but here in Finland where we really do need need electricity for heating, we kinda use these to cut down the costs..

Will you please just leave the Earth alone? (-1, Troll)

Anonymous Coward | more than 5 years ago | (#26508427)

I am TRYING to masturbate!

Re:Will you please just leave the Earth alone? (1, Funny)

Anonymous Coward | more than 5 years ago | (#26508801)

Just think of it as mother earth.

Heat Pump (1)

conureman (748753) | more than 5 years ago | (#26508525)

My dad has a couple exchangers outside his house I've often marveled at the "efficiency", particularly when they are covered in snow, or basking in the sun on a forty degree centigrade day.

Depends on the ground (2, Informative)

Anonymous Coward | more than 5 years ago | (#26508535)

Be warned - this won't work well in all kinds of ground. We've had such a heating system installed in our 200m house about 20 years ago (Germany, with our oil prices we had to get creative a bit earlier than ppl in the US) and we had a lot of trouble with freezing probes (the things that go into the groud) because in the karst (ground with lots of lime in it and thus lots of small caves) they wouldn't keep proper contact with the earth.

Re:Depends on the ground (4, Funny)

Facetious (710885) | more than 5 years ago | (#26508683)

Am I the only one who read that as 200 milliamp? For a moment I was astounded by the home's efficiency.

Re:Depends on the ground (1, Informative)

Anonymous Coward | more than 5 years ago | (#26508705)

It was meant to mean 200 square meters...

Re:Depends on the ground (3, Insightful)

Yvan256 (722131) | more than 5 years ago | (#26508887)

Slashdot, which is supposed to be run by nerds, still doesn't support UTF-8. Simply use HTML entities next time.

Re:Depends on the ground (1)

rrohbeck (944847) | more than 5 years ago | (#26509383)

Am I the only one who read that as 200 milliamp? For a moment I was astounded by the home's efficiency.

That just depends on the voltage you're using.

Re:Depends on the ground (4, Funny)

HisMother (413313) | more than 5 years ago | (#26509001)

200 milli-Angstroms? That's a damn tiny house...

Re:Depends on the ground (5, Funny)

sokoban (142301) | more than 5 years ago | (#26509141)

I tried to stop by his place, but since I knew its momentum exactly I couldn't find it.

NOT NEW (-1, Flamebait)

Anonymous Coward | more than 5 years ago | (#26508613)

I've been tapping ass for years. Nothing like a tight wet pussy to warm up my dick. Kevin Dawson wouldn't know about that, though.

Done a lot around here (4, Interesting)

Timo_UK (762705) | more than 5 years ago | (#26508637)

Here in South Germany about 25% of the new houses built in our neighborhood have it. Old hat. If you use your garden as the storage medium your plants will flower later than your neighbor's....

Re:Done a lot around here (1)

srothroc (733160) | more than 5 years ago | (#26508731)

So what happens when people all over the world start using it, since it's touted as being "environmentally safe"? Literal "global warming"?

Re:Done a lot around here (1)

Kompressor (595513) | more than 5 years ago | (#26510735)

And global cooling in the winter! O noes!

Then again, they might just balance out and leave the entire planet temperate...

Re:Done a lot around here (3, Funny)

nurb432 (527695) | more than 5 years ago | (#26509101)

Ya, its pretty common here too.

The story writer must live under a rock... no wait...

Re:Done a lot around here (1)

Rotaluclac (561178) | more than 5 years ago | (#26509243)

My girlfriend and their neighbours (living in Germany) built this system for their houses too. In summer, heat from the Sun is stored directly underneath the houses. In winter, the hot soil is used to heat water and to heat the house itself. If soil temperature drops too much, a heat pump is used. That's of course powered by the photovoltaic cells on the roof. Rotaluclac

What about DX? (5, Interesting)

unixluv (696623) | more than 5 years ago | (#26508655)

This technology has been around for some time, but it fails to generate much PR. You can get a measley $8000 US federal tax credit for installing one. A few enlightened states (not mine) will give you some additional tax credits for installing one.

The expensive part seems to be drilling the earth and laying the hose. However, what they fail to mention is that once its installed, it will last 50+ years.

The parent also mentions open and closed loop, but fail to talk about direct exchange aka DX, which would make more sense for a lot of people.

From []

"The direct exchange (DX) system is a series of copper tubes buried 4 to 6 feet below ground level. Refrigerant gas is then fed through these tubes creating a direct heat exchange between the temperature of the ground and the heat transfer medium, which in this case is the refrigerant gas. Because of this direct exchange feature these systems operate at considerably less operating cost than water source systems and because they do not require the additional water pumping cost and, DX does not suffer the heating or cooling loss associated with transferring the water temperature to the refrigerant as is common with these systems. DX is also cheaper and easier to install as it requires no well drilling or plumbing costs. As copper is a more efficient heat transfer medium than PVC pipe as found in water source, trenching costs are less due to less ground mass being required by DX." [] []

Re:What about DX? (1)

unixluv (696623) | more than 5 years ago | (#26508661)

Ooops... typo in above post... It should be $2000 USD.

Re:What about DX? (2, Informative)

Anonymous Coward | more than 5 years ago | (#26508807)

Live in upstate NY - turned on our ground-source closed-loop heat pump end of November 2008. So far, so good.
Last year when we bought the system nobody was talking about DX (and in this neck of the woods, they're still not.)

Couple of things I would speculate about with respect to DX:
1 - copper pipe is MUCH more expensive than plastic geo-tubing and susceptible to oxidation and mechanical failure (e.g. you can punch a hole in a copper pipe pretty easily.)
2 - the refrigerant is likley NOT to be environmentally save (a closed-loop ground-source heat-pump system uses a 50/50 mix of food grade glycol and water - leaks are claimed not to have any environmental impact. The same cannot be said for most refrigerant gasses.
3 - I would expect the cost of install for a DX system to be higher than the ground-source closed-loop (as refrigerant costs more than glycol) so you'd want to factor that into your total cost and ROI calculations
4 - Residential installs can get a rebate in certain states as well (NY / California / not sure of the others). I think it maxes out at 2k or 3k. I'm not aware of a federal rebate for a non-commercial install (e.g. single-family home.)
5 - Ignorance expressed here: not sure if you can tie in the residential hot-water to a DX system (just don't know if they come with such a system tie-in available.) On our ground-source system, we ordered it with a built-in heat exchanger that heats our domestic hot water whenever the system is running. (Cuts your water-heating expense by 50~75%)

Hope this helps.

Re:What about DX? (4, Interesting)

rhakka (224319) | more than 5 years ago | (#26508817)

DX systems suffer because they are burying copper in the ground (which is often aggressive to copper), and then pumping refrigerant through them. any puncture or breach would cause a leak of refrigerant instead of non toxic glycol solution.

DX and "Pump and Dump" geo-exchange systems are both, IMHO, likely to be outlawed in areas with environmental and building codes. Existing systems would probably be grandfathered but in the end I believe closed loop well or "slinky field" type systems will end up the winners.

Re:What about DX? (0)

Anonymous Coward | more than 5 years ago | (#26509033)

It's the coward from Upstate NY again...
Regarding closed-loop wells - water quality can present a significant problem. Water quality around here ranges from fabulous to hard to iron to hydrogen sulphide (sulphur water) due to deposits in the ground (most places that have natural gas wells have some kind of sulphides dissolved. Hydrogen sulphide gas ends up decomposing into a black powdery substance and sulphuric acid - which eats copper - supporting my previous post.) These are SIGNIFICANTLY corrosive (both to geo pumping and heat-transfer systems). Iron in the water can clog intakes and cause sludge build-up. All potentially detrimental to the lifetime of a system (hence my decision to go closed-loop rather than well-based.)
Final thought regarding "slinkys" is that they'll do if you don't have the space to run uncoiled. But if you have the space, I would pass on the slinky and get as much length to your system as possible. Slinkys are likely to be less efficient than a straight-run system if only due to the fact that a) there is less physical space in which to transfer heat from your system to the ground and b) the "crossing points" generated by the slinky design (where the pipes touch one another in the coil) are likely to make the system less efficient (as the heat or cool that is supposed to be transferred to the GROUND is instead transferred back into the pipe conveying the GeoThermal Fluid - aka gtf.

If I was to re-install my system today, rather than digging trenches and burying the plastic pipe, I'd dig a pond (8 feet / 3 meters plus deep) and simply toss slinkies into the bottom of it. A trench would still need to be dug from the house to the pond, but heat transfers between plastic and a fluid (the water in the pond) MUCH more efficiently than it does between the plastic pipe and dirt. Plus you get the benefit of convection currents of the fluid in the pond being able to take away either the heat or the cold from the lines.

Re:What about DX? (1)

rhakka (224319) | more than 5 years ago | (#26509193)

closed loop wells don't use copper as the well sleeve, . they also don't replentish their water (that is why they are closed loop). right?

slinkies are not ideal... DX is, except for the breach and refrigerant issue. closed loop wells are 2nd though, AFAICT at least.

pond loop is interested, but submerging anything in water long term presents possible longevity issues as well.

Re:What about DX? (1)

jbengt (874751) | more than 5 years ago | (#26509623)

"Closed-loop wells" refers to an actual closed loop of piping, using double pipes with return bends at the bottom installed in well holes. Pumping well water up and using it directly,whether or not the well water was returned to the ground, would be known as an open loop, since the pipes are open at one (or both) end(s). Such open loops are almost never used anymore, due to environmental concerns about wasting water or returning possibly contaminated water to the underground source.

Re:What about DX? (4, Interesting)

kimvette (919543) | more than 5 years ago | (#26508819)

How does the lifetime compare to PVC though? I've seen PVC that has been buried for 30 years and looks absolutely brand-new (the above-ground portions though - not so much thanks to UV). How does copper compare, since copper corrodes?

Re:What about DX? (0)

Anonymous Coward | more than 5 years ago | (#26508913)

Copper won't make it a couple of decades below ground. Which is why no one uses copper below ground for things like water or gas supplies: it's all PVC or cast iron. Putting raw copper piping in the ground sounds like a supremely dumb idea.

Re:What about DX? (3, Informative)

unixluv (696623) | more than 5 years ago | (#26509537)

Actually they have found underground copper piping used by the Egyptians thousands of years old. If copper was so fragile, there would be no copper to be found there.

Copper can be used underground and was used for many years for water supplies. [] []

As noted in the articles, very few Ph and ground conditions can corrode copper, hence I object to the absolute ban of copper in the previous reply.

And yes copper is more expensive. But most plastics (PVC) cannot be used with refrigerants, so given a choice of metal pipes, copper makes sense in certain soil conditions.

With certain precautions, copper is the way to go in DX systems. I do agree with most of the above replies that closed loop is good too. I think that you have to weigh the intended use against the pros and cons, then select the best system for that application.

Re:What about DX? (0)

Anonymous Coward | more than 5 years ago | (#26510781)

Copper doesn't just corrode from exposure to air or moisture. From one the articles you linked to yourself

"Since thermoplastics are non-conductors, they are immune to the electrolytic or galvanic corrosion that attacks and often destroys metal piping materials, particularly installed under ground."

I.e. copper can, and does, corrode quickly due to galvanic processes. It is also a rigid material and will not stand up well to the sort of movement and settling that soil experiences, especially ground which has been dug recently: for example, to lay copper pipe...

Re:What about DX? (0)

Anonymous Coward | more than 5 years ago | (#26509839)

I worked for a utility contractor for a couple summers. The main water line for the subdivisions we were making were ductile iron. All the taps for each individual building were copper lines. Would think something besides copper would be used if it were cheaper or lasted longer since these lines are buried before things like roadways and sidewalks and foundations and such. Just me experience.

Re:What about DX? (1, Funny)

Anonymous Coward | more than 5 years ago | (#26509005)

Wouldn't you substitute du for dx and then antidifferentiate? Or do I just have calculus on the brain?

Re:What about DX? (2, Interesting)

jbengt (874751) | more than 5 years ago | (#26509901)

<nitpick> In the HVACR industry, "DX" stand for "Direct Expansion", The thing you're referring to needs a different abbreviation. </nitpick>

I know this system has been used, but there can be some problems with it.
Copper piping can have a short life in many soil types.
There will be more refrigerant in the system, which can add some complications and expense.
I wonder how they handle oil return when operating in the heat pump mode?

Ground source makes cents (3, Interesting)

Anonymous Coward | more than 5 years ago | (#26508679)

Consider that heat pumps give you on average 3 times more heating or cooling per unit of electricity over resistance heating, for example baseboard heating.

If you ignore the mindless Greenpeace types, and your power is from nukes (like in France) there are no greenhouse gas emissions at all and the air stays nice and clean. Likewise, if you live in the Northwest, where hydro makes a great deal of power and electricity is cheaper and cleaner yet.

One of the big problems with conventional heat pumps is that the coils can ice up in damp cold conditions, like the Northeast USA when temps are 35 degrees F and below. If you ground source, there is no defrost cycle needed, and no noisy fan. You have probably seen a heat pump at some point blow a huge ball of steam off on a cold day at some point, that's the defrost cycle.

Re:Ground source makes cents (0, Flamebait)

Malekin (1079147) | more than 5 years ago | (#26509413)

If you ignore the mindless Greenpeace types, and your power is from nukes (like in France) there are no greenhouse gas emissions at all and the air stays nice and clean.

Greenpeace are a bunch of nutjobs and the more base generation goes nuclear the better, but it's not totally greenhouse-gas-emission free. Mining the ore and enriching it generates GHG. The many, many tonnes of concrete that go into building the plants (~200 cubic metres per MW) generate GHG. Sure, it's the total GHG/kWh is less than just about any other technology, but it's not nothing.

Glad I live where electricity is cheap (0)

Anonymous Coward | more than 5 years ago | (#26508689)

I'm glad I live where electricity is relatively cheap - in the southeast USA. We aren't as cheap as northern AL (hydroelectric), but our coal and nuclear plans have us near the bottom of the rate scale.

Combine that with natural gas for heating and underground utilities and my access to gas, electricity and water has been impacted more than 2 minutes a total of 3 times in 10 years. Water was shutoff for pipe work for about 6 hours - that was the longest impact. My gas and electric meters were replaced recently - about 20 minutes of impact.

Summer electric bills are around $130/month, but usually around $50 or less.

Winter heating is very tied to the temperature. Last month was $135, but it has been colder than normal this year. Perhaps another ice age is coming?

Water is always $17.23/month.

This is for a home about 2500 sq foot (3 bdr, 3 bath).

Reality Check (0)

Virtually Sane (1168935) | more than 5 years ago | (#26508761)

I got a quote from a UK company 2 years ago, some #1000 per KW of heating/cooling. Needless to say, there was no interest.

This was due to the compressors and pumps needed, there is also a high maintenance overhead as well

It is highly dependent on water movement through the soil structure, so putting one under a car park is a no-no.

Can anyone say... (-1)

Anonymous Coward | more than 5 years ago | (#26508769)


Re:Can anyone say... (1)

Yvan256 (722131) | more than 5 years ago | (#26508843)


What do I win?

More Articles (3, Interesting)

bosef1 (208943) | more than 5 years ago | (#26508781)

The Washington Post had an recent article [] about this technology being applied in the Washington, DC, area. Slashdot has also featured [] articles [] on similar technologies that use deep water from large lakes or the oceans themselves.

Since the article doesn't mention it... (5, Interesting)

G-Man (79561) | more than 5 years ago | (#26508805)

...I would also point out that Bush's Crawford Ranch [] uses a geothermal heat pump.

Re:Since the article doesn't mention it... (2, Funny)

ScrewMaster (602015) | more than 5 years ago | (#26509067)

...I would also point out that Bush's Crawford Ranch [] uses a geothermal heat pump.

Ah yes ... but does Al Gore's?

Re:Since the article doesn't mention it... (4, Funny)

sokoban (142301) | more than 5 years ago | (#26509159)

Al Gore doesn't have a Crawford Ranch.

Crawfish ranch (1, Funny)

Anonymous Coward | more than 5 years ago | (#26509263)

"I fondly remember ranching crawfish on my father's farm in Virginia."

Al Gore, "An Inconvenient Truth", 2006

Re:Since the article doesn't mention it... (3, Interesting)

ArcherB (796902) | more than 5 years ago | (#26510531)

...I would also point out that Bush's Crawford Ranch [] uses a geothermal heat pump.

SHHHHHHHHH! You can't say anything at all good about the president. At least not until after inauguration day!

Seriously, I find it sad that we have an article about geothermal heating and cooling that is used by the private residence of the leader of the free world and it's not mentioned. Seriously, you'd think the article would have brought it up.

Has Bush Derangement Syndrome gotten so bad that saying anything good about Bush is taboo? Or was this a simple, innocent oversight?

Firsthand Minnesota experience (5, Informative)

Anonymous Coward | more than 5 years ago | (#26508841)

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.

Washinton County School District... (1)

gandhi_2 (1108023) | more than 5 years ago | (#26508869) Utah uses GSHP for almost every school. It saves them a grundel, but takes years to pay off.

Seriously though, burying your buildings or simply building them underground would be MUCH more efficient. Ammunition bunkers I used to go to in Hawaii or now in Utah were always cool in the summer and kinda warm in the winter. And hella insulated.

Re:Washinton County School District... (3, Funny)

ScrewMaster (602015) | more than 5 years ago | (#26509091) Utah uses GSHP for almost every school. It saves them a grundel, but takes years to pay off.

What is a grundel, and why would you want to save it?

Re:Washinton County School District... (0)

Anonymous Coward | more than 5 years ago | (#26509295) Utah uses GSHP for almost every school. It saves them a grundel, but takes years to pay off.

What is a grundel, and why would you want to save it?

Considering the Google results for the word, Ganhi_2's explanation for the term could provide some informative amusement in regards to their bundled thoughts at the time they used "grundel" in their comment.

Re:Washinton County School District... (3, Insightful)

navyjeff (900138) | more than 5 years ago | (#26509367)

What is a grundel, and why would you want to save it?

A grundel [] is an Old English bipedal monster or dragon, descended from Cain. I would imagine you would want to save it for yourself in order to keep your neighbor's dog off your lawn.

Re:Washinton County School District... (2, Funny)

gandhi_2 (1108023) | more than 5 years ago | (#26509821)

The dragon also keeps the kids away from the GSHP equipment which is near the playground.

Re:Washinton County School District... (0)

Anonymous Coward | more than 5 years ago | (#26510883)

bunkers I used to go to in Hawaii or now in Utah

Are you hiding out in the bunker because of the anti-prop 8 nuts?? Good idea.

Absolutely (2, Interesting)

Swordopolis (1159065) | more than 5 years ago | (#26508895)

My parents built a new house off the beaten path almost 4 years ago, and opted to go with geo-exchange because natural gas isn't available in their area. The system costs significantly more than a standard one, but heating and cooling costs are HALF of what they were at their old house, which was significantly smaller. According to some back-of-the-napkin numbers my dad crunched, they should hit the break-even point after less than 15 years of use.

We can store carbon dioxide and use this idea. (1)

Burneypmcgillroy (1402963) | more than 5 years ago | (#26508993)

Humans can get some of that extra carbon dioxide we billow out and make a whole new industry for the idle factories and my fellow Americans. [] This is easy stuff and the payoff is less energy to modify temperature and humidity in homes for our human happiness.

I wanted to (4, Informative)

JediTrainer (314273) | more than 5 years ago | (#26509045)

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.

Re:I wanted to (1)

Zerth (26112) | more than 5 years ago | (#26509191)

Only 5 times the cost?

How much cheaper was the yearly operating costs? 5x install sounds like it could pay off in just 5-10 years.

Re:I wanted to (0)

Anonymous Coward | more than 5 years ago | (#26509289)

I'm in Vancouver - Canada. I was interested in doing it too but the company I got a quote from said it was gonna be $40k (plus they said I needed a gas furnace anyways as the efficiency level drops when temperatures reach extreme ends of the scale in winter). The gas furnace I went with was only $8k. I was already over budget on my house at that point because of the increased costs in labour skyrocketing with the exuberant house prices so I just couldn't afford it regardless of how green I wanted to make my place. Nice old technology but because fossil fuels are much cheaper at this moment its not worth it.

Re:I wanted to (1)

ducomputergeek (595742) | more than 5 years ago | (#26509275)

From everything I've head read or heard, going with a DX system makes a lot of sense if you are building new construction. It is easier to install without having to worry about the before mentioned problems of hitting existing pipes and landscaping. But for existing home construction, it's questionable.

Some day when I do build a house, the two things I want are a DX heating/cooling system and solar panels. Lump those costs in the home and use the extra money from what would have been spent on utilities to pay down the mortgage faster. Of course, if you're married, it may go towards the Mrs. shoe and purse fund instead....grumble, grumble...

Re:I wanted to (1)

dieman (4814) | more than 5 years ago | (#26509387)

Exactly. I did a 'hybrid' air source geothermal/gas system and it was still at least 3 to 4 times cheaper. I will make up the cost of the air source heat pump in 4 or 5 years, easy, too. Plus I reduced my GHG by about 30% using 'green' power purchases for the heat pump power. This is in Minneapolis too, no slouch to cold temperatures. All the AHSP needed was a little more space, not an entire tear-out of a section of my yard. I'd love to do geothermal, but its really not a solution for people just trying to fix their dead furnace on an emergency (its dead jim) basis.

Re:I wanted to (1)

jern (585127) | more than 5 years ago | (#26509569)

Yeah, I know the rebate your talking about 8000.00 CDN sounds like a lot of money when you take into account the payback of the system.

Also, what the Ontario/Cdn Gov't wont tell you is that you have to bring up the REST of your home (Read: insulation upgrades EVERYWHERE!) in order to get the 8k

Location, location, location (1)

EmbeddedJanitor (597831) | more than 5 years ago | (#26510483)

It all depends on where you live. I live in an area that was once old river bed and there is a lot of water movement through the old gravels just 5-10 metres below the surface. For me, drilling to 20 metres would be almost as good as placing the heat exchanger in the river.

This idea doesn't work worth squat ... (1)

ScrewMaster (602015) | more than 5 years ago | (#26509083)

Tapping the Earth For Home Heating and Cooling

I've been tapping and tapping, and all I got for my trouble was a broken fingernail.

Re:This idea doesn't work worth squat ... (2, Funny)

CarpetShark (865376) | more than 5 years ago | (#26509409)

I've been tapping and tapping, and all I got for my trouble was a broken fingernail.

This is why you should leave it to the professionals. I bet you just went ahead and arrogantly acted like an expert without even buying a proper pair of tap shoes.

Re:This idea doesn't work worth squat ... (1)

ScrewMaster (602015) | more than 5 years ago | (#26509459)

I've been tapping and tapping, and all I got for my trouble was a broken fingernail.

This is why you should leave it to the professionals. I bet you just went ahead and arrogantly acted like an expert without even buying a proper pair of tap shoes.

No, I just figured the ground would warm up when I tapped it.

oil is not a fossil fuel (-1)

Anonymous Coward | more than 5 years ago | (#26509117)

Dismissal of the Claims of a Biological Connection for Natural Petroleum.

J. F. Kenney

Joint Institute of The Physics of the Earth - Russian Academy of Sciences

Gas Resources Corporation, 11811 North Freeway, Houston, TX 77060, U.S.A.

Ac. Ye. F. Shnyukov

National Academy of Sciences of Ukraine

Vladimirskaya Street 56, 252.601 Kiev, Ukraine

V. A. Krayushkin

Institute of Geological Sciences

O. Gonchara Street 55-B, 01054 Kiev, Ukraine

I. K. Karpov

Institute of Geochemistry - Russian Academy of Sciences

Favorskii Street 1a, 664.033 Irkutsk, RUSSIA

V. G. Kutcherov

Russian State University of Oil and Gas

Leninskii Prospect 65, 117.917 Moscow, Russia

I. N. Plotnikova

National Petroleum Company of Tatarstan (TatNeft S.A.)

Butlerov Street 45-54, 423.020 Kazan, Tatarstan, RUSSIA

1. Introduction.

                    With recognition that the laws of thermodynamics prohibit spontaneous evolution of liquid hydrocarbons in the regime of temperature and pressure characteristic of the crust of the Earth, one should not expect there to exist legitimate scientific evidence that might suggest that such could occur. Indeed, and correctly, there exists no such evidence.

                    Nonetheless, and surprisingly, there continue to be often promulgated diverse claims purporting to constitute âoeevidenceâ that natural petroleum somehow evolves (miraculously) from biological matter. In this short article, such claims are briefly subjected to scientific scrutiny, demonstrated to be without merit, and dismissed.

                    The claims which purport to argue for some connection between natural petroleum and biological matter fall into roughly two classes: the âoelook-like/come-fromâ claims; and the âoesimilar(recondite)-properties/come-fromâ claims.

                    The âoelook-like/come-fromâ claims apply a line of unreason exactly as designated: Such argue that, because certain molecules found in natural petroleum âoelook likeâ certain other molecules found in biological systems, then the former must âoecome-fromâ the latter. Such notion is, of course, equivalent to asserting that elephant tusks evolve because those animals must eat piano keys.

                    In some instances, the âoelook-like/come-fromâ claims assert that certain molecules found in natural petroleum actually are biological molecules, and evolve only in biological systems. These molecules have often been given the spurious name âoebiomarkers.â

                    The scientific correction must be stated unequivocally: There have never been observed any specifically biological molecules in natural petroleum, except as contaminants. Petroleum is an excellent solvent for carbon compounds; and, in the sedimentary strata from which petroleum is often produced, natural petroleum takes into solution much carbon material, including biological detritus. However, such contaminants are unrelated to the petroleum solvent.

                    The claims about âoebiomarkersâ have been thoroughly discredited by observations of those molecules in the interiors of ancient, abiotic meteorites, and also in many cases by laboratory synthesis under imposed conditions mimicking the natural environment. In the discussion below, the claims put forth about porphyrin and isoprenoid molecules are addressed particularly, because many âoelook-like/come-fromâ claims have been put forth for those compounds.

                    The âoesimilar(recondite)-properties/come-fromâ claims involve diverse, odd phenomena with which persons not working directly in a scientific profession would be unfamiliar. These include the âoeodd-even abundance imbalanceâ claims, the âoecarbon isotopeâ claims, and the âoeoptical-activityâ claims. The first, the âoeodd-even abundance imbalanceâ claims, are demonstrated to be utterly unrelated to any biological property. The second, âoecarbon isotopeâ claims, are shown to depend upon measurement of an obscure property of carbon fluids which cannot reliably be considered a measure of origin. The third, the âoeoptical-activityâ claims, deserve particular note; for the observations of optical activity in natural petroleum have been trumpeted loudly for years as a âoeproofâ of some âoebiological originâ of petroleum. Those claims have been thoroughly discredited decades ago by observation of optical activity in the petroleum material extracted from the interiors of carbonaceous meteorites. More significantly, recent analysis, which has resolved the previously-outstanding problem of the genesis of optical activity in abiotic fluids, has established that the phenomenon of optical activity is an inevitable thermodynamic consequence of the phase stability of multicomponent fluids at high pressures. Thereby, the observation of optical activity in natural petroleum is entirely consistent with the results of the thermodynamic analysis of the stability of the hydrogen-carbon [H-C] system, which establish that hydrocarbon molecules heavier than methane, and particularly liquid hydrocarbons, evolve spontaneously only at high pressures, comparable to those necessary for diamond formation.

                      There are two subjects which are particularly relevant for destroying the diverse, spurious claims concerning a putative connection of petroleum and biological matter: the investigations of the carbon material from carbonaceous meteorites; and the reaction products of the Fischer-Tropsch process. Because of their importance, a brief discussion of both is in order.

I have one. (4, Interesting)

haeger (85819) | more than 5 years ago | (#26509353)

About a year ago we installed one of these in our house. The temperature around here varies between -15 C to about +30 C (get with the metric program people) and our heatpump is working wonders with our heating and economy. It cut the costs down to 1/3 of what it used to be and will have paid itself off in less than 5 years with current prices.
We drilled about 200m down which gives the best performance for the size of our house.
Also we put a large watertank that the heatpump warms up which increases the lifespan of the pump and our next project is to put solar panels that will heat the watertank during mars-oct, thereby increasing the savings even more. It will also "reload" the hole/well that the heatpump takes its heat from increasing the efficiency during winter.
Now if I could only produce electricity somehow to power the heatpump (or parts of it) things would be awsome.

I'm amazed that more people don't use this technology. In my opinion there shouldn't be an energy crisis anywhere as all the technology we need to fix things are already availible. More or less anyway.


Re:I have one. (3, Insightful)

Fallingcow (213461) | more than 5 years ago | (#26510809)

I'm amazed that more people don't use this technology.

Like most things, it's not for everyone.

Our quote for installation here was about $25,000 for a system that would heat/cool a 3000sqft house.

The house cost us less than $100,000, and we probably won't be here more than 3 years or so. No way in hell the house's value will be increased by at least the difference between our savings and the remaining cost of installation when we sell. Conclusion: we would lose money putting in that system.

It's sad, but unless these kinds of improvements become more highly-valued by home buyers or people stop being so damn mobile, for many of us it's just not worth it to make long-term energy efficiency investments in our houses.

it's the future (and now) (0)

Anonymous Coward | more than 5 years ago | (#26509541)

Near me, many people already have wells and they use propane to heat (big $). Huge savings for them if they have a place to dispose of the exit water.

If you have natural gas available and don't have a well, then it might not be the best deal.

Ground source heat pumps are least 3x more efficient than electric and with the right design, can go as high as 6x more efficient.

Check out the Goethermal Heat Pump Consortium (1)

InterGuru (50986) | more than 5 years ago | (#26509595)

The Goethermal Heat Pump Consortium [] is an industry group. Their site is full of information resources, blogs,and forums. [] -- over 7500 published book reviews.

ground-exchange? the price tag hurts... (5, Informative)

chrispitude (535888) | more than 5 years ago | (#26509709)

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

Re:ground-exchange? the price tag hurts... (1)

Buelldozer (713671) | more than 5 years ago | (#26510287)

I'm in Central Wyoming and I'm interested in something like this but I'm also tinkering around with various 'get off the grid' projects and I'm curious how much power generation I'd have to install in order to run one of these.

So, if you feel like sharing, what exactly is your kWh usage?

Re:ground-exchange? the price tag hurts... (0)

Anonymous Coward | more than 5 years ago | (#26510993)

So explain this, why am I to trust a company that clams 300% efficiency? And a 5 year warranty?? I thought 10 or more is the standard, what is wrong that they can't support a longer warranty? Too much magic talk in there ads.

"so-called geothermal energy" (1)

minsk (805035) | more than 5 years ago | (#26509715)

Any idea what would motivate someone to add a "so-called" to geothermal in the summary? It's used following its so-called "definition", and is certainly a more so-called "established" term than the so-called "geo-exchange"...

Unintended consequences? (2, Interesting)

Nimey (114278) | more than 5 years ago | (#26509959)

I can't help but wonder about what would happen if a sufficient number of people in an area used heat pumps, long term.

What would happen if the ground got abnormally warm? Would this cause any problems with ground strength, or soil moisture, or what have you?

I'm genuinely curious here. Has anyone done a study about this?

Re:Unintended consequences? (1)

DamonHD (794830) | more than 5 years ago | (#26510675)


Have a look at [] where Prof MacKay deals with this.

In practice you can mitigate the problem (which will only be a problem at all in dense population areas) by capturing solar heat in summer, eg excess not needed for solar hot water, and using that to warm the ground. Then the ground is a straight-forward heat-store, maybe a little like this: []



Geothermal pays if you can't get Natural Gas (1)

knobsturner_me (1210594) | more than 5 years ago | (#26510065)

Colder climates - If you can't get Natural Gas, then you are stuck with Propane, Heating oil, or electric. Heat pumps usually produce about 3x - 5x the energy that you put into them. Work best with heated floors. Unfortunately the installers have been installing oversized systems - it is best to make one that can't keep up on 10% of January days, and supplement with propane on those days. We stopped using approx 1ton propane/month for the winter big three months - which is about a 15 ton CO2 reduction for the house per year. Also air conditioning is just about free. Almost all buildings use it in some places in the mountains. (Propane is very expensive on a mountain). Nat gas costs 1/3 that of Propane, oil or electric.

Can be done on larger scales, using old mines... (1)

PhotoGuy (189467) | more than 5 years ago | (#26510991)

This can be done on larger scales, using old coal mines that have been flooded with water. At depth, the water is fairly constant, and the volume of water is large enough, that it can be used as a sink for heat pumps. Here in Nova Scotia, Springhill [] uses old coal mines to help with heating. From wiki:

The abrupt end of the coal mining industry presented incredible economic challenges to the town. An unexpected legacy and benefit from the closed mines is being realized in geothermal energy. The mines in Springhill were among the deepest in the world at over 14,000 feet below the surface. Since their closure, the mines have filled with ground water which is heated to an average temperature of 18 C (65F) by the surrounding earth. Beginning in the late 1980s, this heat source has been exploited by companies located in Springhill's industrial park, situated on the land where the surface facilities of the coal mines were located, reducing winter heating bills substantially.

Note that this isn't using hot steam deposits as a free geothermal heat [] source, like much of Iceland. It's simply using the water in the mines as part of a huge geothermal heat pump [] . A subtle, but important difference. (The former is a greater source of "free heat", whereas the latter still requires heat exchange like a residential heat pump.)

Load More Comments
Slashdot Login

Need an Account?

Forgot your password?