The sounds of the season: geothermal heat pumps as renewable?

One thing is for certain during this campaign, and in recent campaign memory, similar speeches with catchphrases try to grab our attention. Words like “green,” sustainability, dependence on foreign oil, drilling, clean coal, solar, geothermal, etc. The list goes on. I think both men favor the idea of a more sustainable planet, but the route is a little different. When Governor Romney talks of renewables, I can’t decide if he’s talking about part of his energy program or a new Oscar Mayer lunch pack. President Obama can’t talk about solar without the whole Solyndra thing in the backs of people’s minds. And do you think either of them really understands the ins and outs of geothermal?

The time has finally arrived. The 44th president of the United States has been selected. For months we have been subjected to speeches, commercials, etc., featuring each candidate’s viewpoints, and, of course, what campaign would be complete without each other ripping into the other's policies.

One thing is for certain during this campaign, and in recent campaign memory, similar speeches with catchphrases try to grab our attention. Words like “green,” sustainability, dependence on foreign oil, drilling, clean coal, solar, geothermal, etc. The list goes on. I think both men favor the idea of a more sustainable planet, but the route is a little different. When Governor Romney talks of renewables, I can’t decide if he’s talking about part of his energy program or a new Oscar Mayer lunch pack. President Obama can’t talk about solar without the whole Solyndra thing in the backs of people’s minds. And do you think either of them really understands the ins and outs of geothermal?
 
Speaking of geothermal, recently I was fortunate enough to talk with Allison Bailes, PhD, founder and president of Energy Vanguard, www.energyvanguard.com, a source for training, consulting, design (HVAC), and HERS provider services. Allison contributes a blog on the site that is both informative and thought provoking. Recently, he wrote on the topic of whether a geothermal or ground-source, heat pump counts as a renewable heat source. (http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/54408/D...).
 
What I found most interesting about this was: how many of us really know the ins and outs of geothermal? According to Bailes, “I don't use the term 'geothermal heat pump.' It's too confusing. Even Thomas Friedman, the columnist for the New York Times who's written some well-received books about the environment, is confused about this. He wrote in a column a few years ago that he's using renewable energy in his home because he installed a geothermal heat pump. Really now. If a ground source heat pump is a renewable energy source, then so is a refrigerator.”
 
Interestingly, Bailes describes the confusion, “I think the source of the confusion about ground-source heat pumps and renewable energy is the unfortunate use of the term 'geothermal' in connection with these devices. When you hear the word 'geothermal,' you think of lava or geysers, of volcanoes blowing their tops. You think of heat engines being driven and doing useful work by harnessing the heat from within the earth. But that's not what ground-source heat pumps are or do. They're just like your regular air conditioner or heat pump except they use the ground instead of the air as the source or sink for heat. They still use electricity to power the pump that moves the working fluid through the loops. They still use electricity for the blower that moves the air through the duct system. They still use even more electricity to run the compressor, which is the pump for the refrigeration cycle. That electricity generally comes from outside the home, often from a power plant that burns coal or natural gas. Last I heard, most folks don't consider those fuels renewable.”
 
I asked Allison about the muse for such a blog.
JM: What was your impetus for writing this blog? And why does this make you so crazy?
AB: It's possible that my annoyance began when Thomas Friedman wrote a few years ago that he was using renewable energy because he installed a geothermal heat pump. To me, a heat pump is a heat pump, no matter where it gets or deposits the heat from a building. You put electricity in and you use it to move some heat. It's fundamentally different from capturing solar energy and putting it into hot water or converting it into electricity or from using high-grade heat from a true geothermal source.
 
JM: If not renewable, ground source heat pumps are __________?
AB: ...just like other heat pumps, air conditioners and refrigerators. 
 
JM: Do you think that there is a lack of understanding or education regarding certain topics among contractors and marketers for that matter?
AB: Absolutely! That gap is what fuels my blog. From ventilating dehumidifiers that suck in bad air from a vented crawl space to oversized air conditioners to attic kneewalls that lead to uncomfortable bonus rooms and much more, I have no shortage of topics to write about. I'm trying to raise awareness of the problems with buildings so that the occupants know enough to ask for work to be done properly and contractors can learn some of the building science behind their work.
 

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on Nov 29, 2012

I disagree with Allison Bailes about "geothermal" heat pumps, and air-source heat pumps not being renewable energy sources. Consider the ultimate source of heat that these heat pumps are gathering, in heating mode, from the low temperatures sources (ground, and outside air). That heat is coming from the sun. In the case of geothermal heat pumps, this solar energy is just being stored for a few weeks or months until it is needed by the load. Even an air source heat pump is extracting low grade heat provided by the sun - just at a lower temperature.

Consider this comparison: For a geothermal heat pump operating at a Coefficient of Performance (COP) of 3.0, two units of heat are coming from the ground (e.g. free solar sourced heat), and the remaining one unit of heat is coming from electrical energy operating the compressor. Thus 2/3 or 66.6% of the heat that gets delivered to the building is (ultimately) from the sun. Next, consider a solar thermal water heating system (which just about everyone would label as a renewable energy system). Suppose that it supplies 66.6% of the home's hot water needs from absorbed solar energy, and the remaining 33.4% from the backup electric element. Again, 2/3 of the energy delivered for used came from the sun, and the remaining 1/3 came from electricity. So, based on this comparison, both systems deliver the same effect. Why should the solar thermal system be labelled "renewable" and the geothermal "non-renewable?"

Regarding the terminology: Geothermal, ground source, etc. Technically, the "source" for a refrigeration cycle is always the low temperature heat being absorbed, and the "sink" in where the highter temperature heat is being dissipated. So, in the heating mode, it would be appropriate to consider the earth the source of heat, thus "ground source" applies. However, in the cooling mode, the source is indoor air that's being cooled and dehumidified. Thus, to be technically accurate the heat pump would be "ground sink" in the heating mode.

Technically, "earth coupled" is probably the best term considering that most heat pumps provide both heating and cooling.

I agree that our industry needs to do a better job of explaining where the heat that both air source and geothermal heat pump deliver, comes from.

Respectfully submitted

John Siegenthaler, P.E.

Roger (not verified)
on Nov 29, 2012

The reason geothermal is considered renewable is because the energy that is captured is really solar. The sun heats the ground and then the unit pulls the heat from the ground and puts it into the building. Geothermal can give you three to five times as much heat as an electrical resistance heater.
By your standards, solar hydronic systems use electric pumps to move the heated water and would therefore not be considered "renewable" either. Solar photvoltacic systems doesn't work at night or cloudy days like geothermal does, so which is saving more non renewable energy???

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