Why Ground Source Heat Pumps Should Not Be Called Geothermal, Chapter CLXXI

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©. Mattamy Homes submission to Town of Markham

When even so-called experts don't know the difference, you must admit we have a problem here.

Up north of Toronto in Markham, Ontario, Mattamy Homes is building a new subdivision that is going for net-zero emissions. About three hundred homes will have heat pumps connected by pipes to a network of wells managed by Enwave, a company that does district heating and cooling. The company calls the system "geothermal".

network of wells

© Mattamy Homes submission to Town of MarkhamThe Canadian Broadcasting Corporation is on it, and Philip Lee-Shanok balances the story with Markham community will use geothermal in all its homes, but some critics aren't hot on it. He interviews Tom Adams, an independent energy analyst, researcher and former executive director of Energy Probe, who is skeptical.

"This is one of those things that I wish would really work," he said. "But I think we need to be kind of chastened by history." Adams says in places where there is more geothermal activity, such as Iceland or parts of California, it completely makes sense. However, experiments with the technology in Canada have been less successful.

At this point I wanted to run out of the room screaming, because if a so-called expert and the CBC do not know the difference between real geothermal in Iceland and Ground Source Heat Pumps in Markham, then clearly I have been right all these years when I have said don't call heat pumps geothermal!

I should point out first that Energy Probe is made up of a bunch of climate deniers funded by the oil industry and shouldn't be considered a reputable source, but let's skip that for now and go back to basics.

Ground source heat pumps and geothermal are two entirely different things.

Nesjavellir Geothermal Power Station in Iceland

Gretar Ívarsson/ Wikipedia/ Nesjavellir Geothermal Power Station in Iceland/CC BY 2.0

I have been complaining about the confusion that comes from calling ground source heat pumps (GSHPs) geothermal since I started writing for TreeHugger andtried to define the difference on Treehugger:

  • Geothermal systems use heat directly from natural sources like hot springs, geysers and volcanic hot spots like the installation on the right in the Iceland photo above.
  • Ground source heat pumps are essentially air conditioners that use soil or groundwater to cool the condenser instead of an outside coil and fan. It uses electricity to move heat energy from one place to another. Run it backward and it provides heat, and more efficiently than using electricity directly.

The industry says it is "a clean (no fossil fuel consumption) form of renewable energy that involves our sun heating the earth beneath our feet. Through a geothermal system (geo for earth and thermal for the heat from the sun), we use that energy in the ground to heat and cool our homes."
Fine, there is a grain of truth here. When a GSHP is in heating mode, it is indeed moving heat from the ground to the home and that heat can be assumed to be from the sun. However, in cooling mode, the GSHP is pumping heat into the already warm ground and there is zero gain of any kind from solar energy. It is not renewable, and it is running on electricity, which could well be made with fossil fuels.


ASHRAE/Screen capture

I have given up complaining about this (not really, see related links below); it's one of those things that they keep saying long enough that even they believe it and publish it in ASHRAE news, where they say the Unity Temple is powered by geothermal energy. It's not; it is powered by electricity.


Canadian Geoexchange coalition/Screen capture

The Canadian industry tried to fix this and promote the term GeoExchange, which is sexier than GSHP and actually is technically correct, but it never caught on, not even with people like Mattamy Homes and Enwave that should know better.

I know I will never change anyone's mind about the use of the word geothermal for GSHPs; it is universal now. But the CBC and Tom Adams prove once again that it is still wrong.

pipes from below

Mattamy Homes submission to town of Markham/via

Mattamy explained how the system works with these weird drawings of underground pipes that actually just show how complex things are below the pavement. Many in the green building world have given up on GSHPs and are going instead for a combo of highly efficient building envelopes and air source heat pumps that cost a fraction as much, and which would eliminate half of this mess of pipes, but that's another post.