Lloyd,
I'm sorry to have to disagree with you here, they are both quite clearly GEOTHERMAL, in that they both work with thermal energy obtained from the ground.(Greek, geo meaning earth and therme meaning heat)

You miss the fact that not all heat pumps are geothermal (or ground sourced), some can be air sourced as well. The greater thermal differential obtained from the ground loop simply increases the efficiency of the heat pump.

Just because someone doesn't agree with your definition of the terms doesn't make them wrong.
Arguably "geothermal system" describes them both equally well. What you meant to say was "geothermal electrical generating system".

And contrary to the article in Green Building Elements, neither system can generate energy. energy is never created nor destroyed, only converted from one form to another. Someone so concerned with proper terminology should know that.

Aaron - very clear and correct.

Now; is using the term deceiving?? Sure; but not because of its own fault. I think "geothermal" was added recently to heat pumps' descriptions.

"At a depth of 5 or 6 feet below the ground, the temperature is relatively stable year-round." If the above statement is true , why's my basement always colder? pleasant in summer but freezing in winter !

Praveen,

Compare the temperature fluctuation in your basement with that of the air outside. I would guess that there is not much more than a 20 degree F swing from the coldest to the warmest the basement ever gets (assuming no conditioning) where as the outside air could have, I don't know, 70F-100-F temperature difference depending where you live between the warmest or coolest days. (Yes, all of you who live in Minn. I know that you get like a 400 degree temperature swing or something).

The deeper you get in the earth, the less the temperature fluctuates between seasons.

Technically I suppose this could be argued either way. One could point out that using a ground sourced heat pump for cooling is dumping heat into the ground not utilizing the ground's heat... though one could also say it's geothermal in that it means using the thermal mass of the geo.

Having said that... I don't like the recent conflating of the two terms. It's just nice to have separate terms for such different technology. If I'm at a cocktail party and state that California really should support more geothermal... I don't want it to be taken as a suggestion that someone should start drilling holes in their garden.

I'm just wondering who this is hurting. Are people getting geothermal heat pumps being told that they are getting energy from a geyser or volcanic heat? No. Are those looking for the volcanic heat sources being sold closed loop geothermal heat pumps? No.

I'm wondering where the problem is. Is it that one group doesn't like the other group and this is a way of thumbing their noses at them?

This is most certainly a solution looking for a problem. Like we don't have enough of those already.

Your basement's colder because most of it isn't more than 6 feet underground--in fact, usually the top few feet are above grade. If you have windows down there they can be drafty too. You also might have foundation penetrations that aren't sealed, as well as a gap between the sill plate and the foundation wall.

I wonder if only the author is confused on this point. This strikes me as uninformed drive-by "journalism" if you can call it that.

Geo - Earth; Thermal - Heat;

Ground source heat pumps are geothermal in that they make use of the earth's temperature. How is that confusing or misleading?

Ah, now I see the first comment says it better than me. Glad it was clarified.

"I wonder if only the author is confused on this point. This strikes me as uninformed drive-by "journalism" if you can call it that"

I actually take serious umbrage with this comment. I have been a licenced architect for 25 years and in the last ten specified ground source heat pumps for half a dozen projects. Never once in all that time did I hear the word "geothermal" associated with it. I think it is being misused because it sounds techie and impressive, much like the word architect became suddenly a cool word in the computer world. I think it is confusing and have thought so for a number of years. drive by journalism. feh.

UPDATE: I have made a few changes to the post to clarify what I am talking about.

My sincere apologies Lloyd, but I am also in the industry and took the post as an accusation. The post in and of itself now that I read it again has no real thesis, instead points to an article that does lay out the difference fairly clearly. Fair enough.

I just don't think anyone is attempting to mislead by using the term geothermal. It is in my mind perfectly descriptive of the functionality of the ground source heat pump system.

I'd refer to IGSHPA for mor info as they are the leading researchers in the field: http://www.igshpa.okstate.edu/index.htm

Again my apologies, I read an argument in your post that clearly isn't there.

LA: thanks for your note. I will note that if you go to the IGSHPA website that you link to, and click on the tab "what is geothermal? you never see the word again, and they talk only of ground source heat pumps. I think it is sloppy watering down of the language, thats all.

Touché ;)

Kudos to Lloyd on clearing up the use of geothermal, a term that does get stretched. It's better to use "ground source" or "ground coupled" heat pump or "geoexchange", and reserve geothermal for systems that use the heat from the earth directly. Many people get misled into thinking that ground source heat pumps (GSHPs) harvest energy for free or are zero-carbon. I get that question often.

For cooling, ground source heat pumps are way better than air-cooled systems, because the thermodynamic "lift" is less, you're moving heat to a much lower temperature, 50F ground instead of 90F air. Much more efficient.

In heating mode, it's not the case. The heat pump has a coefficient of performance (COP) of 3.0 to 3.5, which means you get 3.0 to 3.5 times the energy out that you put in. But you put that energy in as electricity, and the US electric generation system is only 30% efficient (and relies heavily on coal). So the source energy winds up being very much the same, as are the emissions.

In northern climes, we spend more energy on heating than cooling so the GSHP does not always beat conventional systems.

So why not reserve "geothermal" for systems that don’t require a significant amount of electricity to get the energy, and stick with something more accurate for heat pump systems. That's what I and most of the engineers I work with have decided, and we wish that industry associations would follow suit.

Why confuse it with muddy terms and struggles over when it's "geo" and when it's "ground" or when it's "Heat" vs "thermal" and trying to get the public to accept industry-specific subtleties?

Why not just take advantage of pre-existing layperson understanding that the earth holds heat and is geothermal. John Q. Public already knows that you get more heat at hot springs and that systems may or may not provide more energy than you put in.

Even if you could change people's interpretation of the words geo and thermal, what's the point?

If I missed the point, please explain.

I just plumbed my house into the neighborhood geyser but now my air conditioning bills are too high. Any suggestions?

why do you care if the heat comes from the nuclear reactor in the sky....or the nuclear reactor under your feet?

and at which point or depth does the proportion coming from the earth reactor get deemed more 'important' than the part from the sky reactor?

regards....

Was my comment too long to read?

The point is that "geothermal" is taking heat out of the ground for free, or almost free. There's a little energy used for ancillary loads like pumping.

"Ground source heat pumps" use a significant amount of electricity. For heating, it's not usually better, economically or environmentally, than burning fossil fuel directly.

Toad,
I think you are a little too negative about the potential of ground source heat pumps for heating, using an efficiency argument. The use of electricity means that you are enabling the future use of cleanly generated electricity to heat your house. If you settle for a natural gas furnace, you are committed to a fossil fuel economy. Using an efficiency argument sometimes blinds one to the benefits of fuel switching.

That is a good point, and something worth considering if you have the option to install your own solar cells or wind turbine.

But not so applicable if you're depending on the US grid, because it's unlikely the grid will significantly wean itself off coal over the next 15 years.

My new oil-fired boiler (switched from propane) has been burning mostly biodiesel for 2+ years. There will soon be a waste oil biodiesel plant nearby, and that's about as green as I can go for heat.

I think that GSHPs make sense for small to medium commercial applications that rely heavily on cooling, and have no access to central utilities like steam and chilled water. And for residences in warm climates.

I realize that a GSHP is more efficient for cooling than heating, however here in North Iowa I know of several residences that have huge savings on their heating bills in the dead of winter. Burning LP gas, my bill was over $400 a month for Dec and Jan, at $1.50 per gal. My brother in a slightly smaller house has a GSHP and uses only about 3 dollars a day worth of electricity , (at 9 cents per kwh )to heat his house.....any commments???? thanks John

Wow, so much antagonism on this topic... and as usual, the most strident voices seem to be the least informed.

A few points, if it's not too late...

First, Lloyd is perfectly right to make this post. I've found there's considerable confusion among the public about the two technologies.

Second, semanticists like Aaron should consider the actual source of the energy concerned. "Geothermal" energy is lteerally that: latent energy stored in the earth's core from 5 billion years ago, when it coalesced as a planet. With "ground source", near the surface of the earth, the energy source is actually the sun: the earth acts as a ginormous heat sink to collect and store incoming solar radiation. Near the surface (for some 50 meters) the determinant of ground temperature is climate. The average anual ground temperature will be very close to average anual air temp, with allowances (+1 to 5 degC) made for snow cover (acts as an insulator).

But all in all, the key term distinguishing these technologies is neither "ground source" nor "geothermal". It's "heat pump".

As a gas utility engineer I regularly encounter people who use the term "geothermal heat pump" and believe they are describing a system which uses renewable energy. This confusion is evident in many of the comments here, but Dougie clears it up. The geothermal energy resource is distinct from the solar energy resource which maintains ambient ground temperatures. Normal ambient ground temperature is a heat source and sink, not an energy resource which can do work.

The power of the Earth's geothermal resource is 20 to 30 terawatts. A little is concentrated in hot spots, but typical geothermal energy flow for most of the Earth's surface is 50 mW/m2. This typical rate of geothermal heat transfer does not result from constant temperature, but from a temperature gradient of 12 to 25 C/km.

Ambient ground temperatures vary roughly with latitude and are the result of 80 petawatts of solar power, an average of 200 W/m2 or about 4,000 times the average geothermal energy flow. Geothermal power can maintain a surface temperature of 30 K without the Sun.

For tax purposes, ground source heat pumps are not geothermal property and are not solar property. See www.taxlinks.com/rulings/1981/revrul81-304.htm.

9 cents per kWh is $7 per MMBTU of source energy. If the source is coal, a GSHP emits 247 pounds of CO2 per MMBTU of heating load. $1.50 per gallon propane is about $15 per MMBTU of source energy. Based on source energy and depending on its efficiency, a furnace emits 145 to 165 pounds of CO2 per MMBTU of heating load.

Hydroelectric supplies 7% and nuclear 20% of our current electric use. DOE just announced a goal of 20% by 2030 for wind energy's share. We need to reduce electric use, not add heating loads while hoping for "cleanly" generated electricity. A GSHP is a good alternative for an air source heat pump or electric resistance heat.

Something is wrong here: both geothermal from geysers and geothermal from GSHP take heat from the ground.
One takes more and one takes less. If you use that heat to turn a crank and generate electricity ans then use the electricity to heat your house, or just heat your house you are still using energy from the ground. GSHP can use heat from the ground in places where geysers and volcanic activity isn't available. COP for geothermal heatpumps is 4 and up. You get more energy out than you put in. The "more energy" comes from the ground. If you used the electricity that powers the heat pump to heat directly your COP could never be higher than 1 (and likely much smaller). You could use a GSHP to heat water to boiling, turn a crank and make electricity or use the hot water to power a infrared photovoltaic cell

http://adsabs.harvard.edu/abs/2007ApPhL..90r3113K

but you wouldn't get nearly as much electricity as if you had a hotter heat source. Since the point is to heat the house, not make electricity it is more efficient to keep the obtained energy as heat and not take a loss in converting it into some other form. You could use something other than electricity to turn the pump in the heat pump. You would still get more energy out than you put in. And if 7 percent of electricity in the grid is hydro (clean) and 20 percent is nukes (not hydrocarbon based), then calculating the Carbon emitted as 100% coal is a bit silly. If 20 percent will be Wind, then electricity is getting cleaner.

Two non-electric powered heat-pumps:

adsabs.harvard.edu/abs/1983STIN...8416647R

www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2V-3WS6KSJ-5&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=1676e188af3a60a8d0ce23eb3df15675

This is silly. It's like saying solar thermal isn't "solar" because it's not photovoltaics.

And to answer Praveen's question, your basement is always colder even though ground temperature is roughly constant because colder denser air sinks to the basement(even under doors!) into your basement while hotter air rises. In the winter cold air enters your house above ground and moves the relatively warmer air in your basement upstairs.