The proper term is "ground source heat pump" (GSHP). I often get questions about this technology, and I think that there are some misconceptions out there, so here goes.
How It Works
The way I think of it, there is a magical black box that can take heat at low temperatures and "pump" it up to higher ones. In Edmonton, the ground a few feet below the surface remains at about six degrees Celsius all year round. This is seasonally-stored solar energy - it accumulates in summer and doesn't cool very much during the winter because there's just so much dirt.
So, a contractor comes and drills long holes (150 - 200 feet, I think) in the back of your yard, and runs tubing down the holes. Then, when heat is needed, the heat pump runs a fluid through the tubes in the earth, and pulls solar heat from it. The exact same effect happens in reverse.
With a GSHP, you can pull 3 - 3.5 units of heat from the earth for every unit of electricity that the heat pump uses.
The Hype - Imported From Elsewhere
Using a GSHP is a brilliant idea in Manitoba or Quebec or Vancouver Island - somewhere where no natural gas is available. The thing is, if your only choice is heating with electricity, a GSHP is in effect 350% more efficient than regular electric heating. That is, with regular electric heating (like from a resistance heating baseboard heater), you get one unit of heat for every one unit of electricity invested. As stated above, the GSHP will give you up to 3.5 units of heat for every one. That's pretty good.
The brilliance of the GSHP in other locations, though, doesn't necessarily translate to Alberta. Here, natural gas is available ubiquitously. AND our electricity is mostly derived from burning coal - the enemy of the human race.
So in Alberta, the only fair comparison for a GSHP is a super-efficient natural gas furnace.
Electricity vs. Natural Gas
Most of Edmonton's electricity is generated by burning coal near Wabamun lake. The generators burn the coal, and convert about 30% of the energy in the coal into electricity. Then, it gets sent down the power line to our great city (some of it gets lost along the way, but we'll ignore that for now). If we use the electricity in a GSHP that is 350% efficient, we get 3.5 units of heat back for every 1 put in. The thing is, we're using electricity that contains only 30% of the coal's original energy value. 30% * 3.5 = 105%. A coal-fired GSHP is 105% efficient, then, when considering the energy that was initially in the fossil fuel.
On the other hand, a 94%-efficient natural gas furnace is, well, 94% efficient when considering the energy that was initially in the fossil fuel.
Considering that natural gas is a cleaner fuel than coal in the first place (something about there being more hydrogen in each atom), it's really a wash. From a climate change perspective there is no big advantage to installing a GSHP.
An excellent paper (attached to this post) by Jerry Shaw backs up my observations. His paper notes:
"...coal-fired production of electricity may result in GSHPs polluting more than [high-efficiency natural gas] furnaces"
and
"...GSHPs have a great potential to contribute to a “greener” Alberta. However, this will not occur until the coal-fired electricity production industry begins using better green house gas mission (GHG) reduction technology"
Money
If the price of natural gas deviates greatly from that of electricity, which I believe is impossible under our current system - electricity is priced based on the units that cost the most to produce (which would be the stuff from natural gas-fired electricity generators), then GSHPs might heat your home for cheaper than natural gas. However, I don't believe that it saves you money the way things presently are (I stand to be corrected - please comment if you have another perspective).
Fuel switching
To me, the most compelling reason to install a GSHP is because we're running out of natural gas. The Western Sedimentary Basin - the geological formation, spanning Alberta and some of BC and Saskatchewan, from which the bulk of our natural gas is produced - reached peak production around 2001. It's all downhill from here baby, and don't forget that under the NAFTA agreement, we are prohibited from cutting our natural gas exports to the U.S., even if we are experiencing shortages.
It scares me to think about what Edmontonians are going to be heating their houses with in 20 years. If anything, I would consider a GSHP because electricity can come from any fuel. Somehow or another, the lights will be on in Edmonton 20, 30, or 40 years. Natural gas may not be in the pipe, though. So a GSHP may be a smart investment.
If You Add Cooling...
Of course, until now I've ignored the fact that a GSHP can be run in reverse, thereby providing very cheap air conditioning. Air conditioning is always provided by electricity, so there truly is a very high efficiency gain with a GSHP.
But come on, this is Edmonton! We have 3 weeks of summer here FFS! Now that we've insulated our home, it doesn't get uncomfortably hot anymore. Sure, I walk around without a shirt for 3-4 weeks a year, and I'm sure that's quite painful for my wife and children to witness, but if your house is reasonably efficient, air conditioning is simply not needed in this climate. You're telling me that we need to heat for 10 months a year and air condition for the other 2? Buy a fan!
Conclusion
- Don't install a GSHP because you think it will save you money on your heating bills.
- Don't install a GSHP to save the planet.
- Do install a GSHP to provide your family with the security of fuel flexibility - the electricity could come wind, biomass, solar, coal, natural gas, or (God forbid) nuclear.
- Do install a GSHP if your home is so poorly built that you need to air condition it a lot. Then, the GSHP will be useful and efficient in both winter and summer. The better option, though, is to build an efficient home that doesn't require cooling.
| Attachment | Size |
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| gshp_versus_high_efficiency_natural_gas_jerry_shaw.pdf | 37.41 KB |
| GSHP_DiscussionPaper_CCC_Alberta.pdf | 149.6 KB |
Hey,
Your website is a little gem. This is the first time I've heard about your Mill Creek net Zero home project, and look forward to checking it out when I get back to town.
Thanks a lot.
Hi Conrad
Great article! Very honest and straight-forward. Just found out about this today. As someone who runs a geothermal design and consulting firm, I am painfully aware of the points you make. GSHP technology here in Alberta is definitely challenging in the residential market. Especially on smaller homes. Larger homes, multi-family dwellings and public buildings ranging from small to large can still greatly benefit from it however. Cooling, just as well as heating. As you point out, while gas supplies may be very questionable in 20 years, there will always be sources of electricity. It may even be more plentiful and cheaper. Electricity generation, even if still largely coal fired in 20 years, will be much cleaner than it is today. There are also many advances being made in the GSHP field which are improving efficiencies by leaps and bounds. Improved heat transfer fluids, dual speed or VFD driven heat pumps, and combinations of different technologies, like solar, are, as you know, making these alternate technologies more affordable and attractive.
Cheers! I would love to see your place!
Jeff
I don´t know if it counts for a reason to put in geo-thermal. I want to install geo-thermal for my house. I´ll be retro-fitting it and increasing the insullation next summer. Since I´ll be digging up my yard, I may as well add geothermal. It is a small house 1200sq. Part of my reason to do it is cause the gas company gave us a hard time when we were having some financial trouble. Besides, this months service charges are twice as much as my gas bill. We turn down our gas bill completly (about 15 degrees). I figured that since service charges and gas will always increase and eventually there won´t be any gas, I´ll rather pay for geothermal. I would like to do it more as an investment.
Geothermal doesn't have to be expensive.
I bought a used heat pump, did most of the install work myself, and was able to keep the total cost below $4000 (3-ton water-air on an open loop).
Thanks for your response Ralph. I really want to learn construction. I know nothing about it, which is why I love this site and the sept-by-step photos and comments. It´s nice to know that geothermal doesn´t have to be expensive. I just wish I had the know-how. I would like to take a course or even help a geothermal company to develope the experience. Unfortunately at the moment it is quite impossible. sigh... :( Chances are I may need to go through a contracter.
Chantal,
Although it doesn't have step-by-step instructions, UMass is the best site I've found for wood -frame construction science.
http://bct.nrc.umass.edu/index.php/publications/by-title/
-Ralph
Chantal,
I realize that you posted a while ago but if you are still thinking about putting a geo system in your house I think that best way to prepare yourself is to check out the program that they have at NAIT, the next course runs in October:
http://www.nait.ca/program_home_32016.htm
Regards,
Clayton Bond, P.Eng.
Threshold Energies Corporation
http://www.gothreshold.com
Thanks Clayton,
I am very much thinking in doing so, however I fear that finances may not permit me this year :(
I wanted to also phone some geothermal companies to find out how useful is the course. By taking it would I then be able to work for them? I have limited knowledge in construction and plumbing.
Chantal
This is a great site!
We live on an acreage and are planning to build a new house using geothermal. We've got space so we'd go horizontal rather than deep (with our trenching). We were also thinking of putting solar panels on the south side of our old house (an A-frame) to help provide electricity for our heating system.
How feasible is this (are we dreaming in technicolour?) and what is the ball park cost for geothermal?
Hi Patricia,
I've never heard a ballpark of less than $20,000 for a geothermal system, with many coming in at 30-40k. I don't understand why a 96% efficient natural gas furnace, which provides the same efficiencies at a fraction of the cost ($5000?) wouldn't be the better choice.
Maybe you can't connect to natural gas? Even then, if you're building new you have the opportunity to build efficient enough to go with propane. You could heat with wood as well. Just say no the GSHP!
Conrad
Hi Conrad (and Patricia)
I am still following your progress, thank you for taking the time ot post it so others can learn. Good work!
About GSHP, they are actually more than %100 efficient because they are a bit like a solar collector. You can get more energy out of the system than goes in because it is collecting heat from outside, rather than just burning fuel or converting electricity to heat. That being said, electricity is an expensive form of energy to be using as heat. If electricity prices rise more than other forms of energy down the road, you will have an expensive appliance to feed to heat your house.
I think Conrad has the right idea in just reducing the amount of energy you need in the first place. We have been in a long period of cheap fossil fuels so we use them inefficiently. I believe that period is coming to an end and plain old economics will make us build differently in the future.
Gshp are not feasible in Alberta and are not a green source of heat when electricity is produced by coal. Also they incorporate a refrigeration unit that if there is a failure will cost you a lot to repair. A high efficient furnace or boiler with a well insulated house is still your best bet. There is also an alternative that may hit the market soon which is called E cat. It is a green technology which produces heat with a small cold fusion reactor. It boasts a c.o.p. of 6 which is better than a heat pump but still would not be cheaper than natural gas at these prices.
No one has pointed out that electicity in Alberta will be natural gas fueled by 2020. All the coal plants on Wabamnun have to switch over completely by 2020 to natural gas. Maybe things have changed since I last heard, but thats the last I heard of that. It might be something to take note of.
Thanks for the site.
I am thinking of purchasing land in Parkland County and having either a mobile or modular home. Would solar and geothermal heating be a reasonable alternative to having natural gas lines installed?
That's another way to to add better cooling effects to HVAC.
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