Swimming pool and domestic heating and heat pumps

Posted by kdawson on Sunday January 18, from the geo-exchange dept.

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. ”

And some comments:
1.
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”.

2.

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.

3.
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.

4.
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.

5.
I think it’s highly doubtful that the electricity grid would need to be upgraded. Think of the demand in the summer due to A/C. It might be different in the UK but in North America there’s a huge electricity draw due to A/C in the summer. Geothermal heat pumps are more efficient at cooling than an air to air(i.e. central air, or external air to air heat exchanger) A/C unit. Thus the demand for electricity in the summer would be lower than A/C if everyone was using geothermal exchange.

6.
Since we are on the subject, Toronto did something similar at a larger scale:

7.
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.

8.
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.

9.
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.

10.

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.

11.
Its been around since at least the 1940s. The building I live in (downtown Austin) uses it and it was built in 1938.

12.
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.

13.
As I see it, the big problem is that cap and trade is spectacularly susceptable to rent seeking and regulatory capture [volokh.com]. A carbon tax levied on non-renewable energy to offset negative externalities is much easier to both administer and understand while providing incentives through economics.

14.
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.

15.
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….

16.
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 http://www.geoenergyusa.com/technology.htm [geoenergyusa.com]

“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.”

17.
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.

18.
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?

19.
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.

20.
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.

21.
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.

22.
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.

Haeger

23.
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.

24.
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 [gotohallowell.com] 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 [chrispitude.net]

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

25.
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?

26.
I’ll get to the point but first a little background.

It is an odd reversal here, but because sewer rates are so high here and city water metering was the way to measure sewer use. People in the suburbs started drilling wells in my area because it has an easy to get at artesian water table. Without the the use of city water there was no way to tax the sewer use. Got the idea and how it is going to apply?

So the city in it’s infinite wisdom decide that wells were ‘verboten’ no matter what over the whole area. There is no way that you can get a permit.

Now you may think that explaining what you want to do to heat your home would get you a variance. Not simply because the city won’t budge, but even more ludicrous is they think you will cheat and not put the water back in the ground as that costs more, but will dump the water into the sewer and increasing the water to the plant for free on your side. Thus making you a thief before found to be one. So easier and cheaper for them is to ban wells period no matter how well intentioned you are to green the planet.

It’s to bad I wrote this late as it is not likely to be moderated high enough to get noticed and other point out a similar problem in their area that stops this type of system dead before it lives.

27.
I have always thought that combining one of these systems with a passive solar heat storage block and a Stirling engine to help power the pump would be fantastic.

28.
Am I the only one who read that as 200 milliamp? For a moment I was astounded by the home’s efficiency.

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