I found this on a site that I usually like a number of the other articles - http://www.builditsolar.com/Projects/SpaceHeating/GSJeatPump.htm . I generally think there's some pretty fair offs on his numbers and methods.

Well, first of all, he's not making an accurate comparison.

If he's going to cite in-field performance of 3.0 for a GHP's COP, then he needs to use the avg. in-field performance of a 90%+ gas furnace. Tests show time and again that a 90% furnace usually at best sees an in-field performance of about 75% efficiency. So let's use that to begin with.

Next, we typically, with our closed loop DX systems--in Utah--see a COP of 4.5 in the field. Not just in the lab. Plug in just those numbers, and what do you have? Maybe a more valid comparison.

I argued the CoP with him and he said he's never seen a report before showing the actual in the field seasonal performance of a geothermal unit, so he's assuming the numbers from the ARI certifications are very optimistic.
I didn't know a high efficiency gas furnace tends to work so much less in the field.
I'm also inclined to think the CO2 of the natural gas is based purely on the amount of burnt by product at site, not the cost of drilling it up, pumping through the earth / etc. His figure for the electricity is based on burning coal, and I imagine but can't find full documentation that it depends on moving the coal, using a very old power plant transmission line losses / etc.
Of course, I also argued with him, if the cost of wind and solar go down, it's possible to hook a geo system to them for 0 carbon. I don't know what part of a natural gas furnace you can hook up to those.

Fundamentally his methods and premise are correct. I've brought this up before - in general the GSHP industry greatly exaggerates the environmental benefit of heat pumps in terms of CO2 production. It's a pet peeve of mine since there are a multitude of other sound reasons for using a GSHP and in many cases it is indeed one of the more environmentally sound heating methods. GSHP sellers shouldn't need to distort facts on this issue, it just undermines their credibility in other areas.

As Clark noted, this calculation is highly dependent on the assumed efficiency for the fossil fuel system and the assumed COP for the heat pump. There are plenty of systems out there with seasonal COPs of 4.5-5 or even higher, both water source and DX. Unfortunately documentation is hard to come by, but I'm pretty sure you could dig up a few studies. 75% may be a reasonable number for the typical hack-installed 90% furnace, but a high-end condensing boiler correctly sized and with good controls can definitely be over 90% efficient over the course of a season.

The other big issue is power mix and what you assume for emissions from coal, natural gas, and oil plants. Power mix varies widely by region, and there is a huge range of efficiencies and emissions among power plants. I generally use DOE data from http://www.eia.doe.gov/. Areas with a larger % of hydro, nuclear, etc will have much lower emissions per kWh.

CO2 is not the only emitted quantity to worry about, either. NOx, SOx, and particulates are of concern as well, and these also vary greatly depending on how the power is generated.

I've done a few of these analyses for people, and while I generally go into much more detail in terms of getting the power mix, efficiencies, and emissions correct, this guy's fundamental point is valid, though I'd argue slightly weighted agains heat pumps. For most areas, a low-end GSHP (which I would define as having a seasonal COP of 3.5 or lower) compared to a well-designed, modern natural gas boiler will be at best a wash in terms of emissions. However, if you compare a GSHP to an oil boiler/furnace or a coal stove, the GSHP comes out way ahead (largely due to SOx emissions which are quite high with oil). A higher end heat pump with a COP of 4 or higher also looks pretty good compared to fossil fuel.

Cyngeo, in your look at it, have you ever looked at the economics and pollution difference that comes from running a more even demand? It seems geo, usually operating at twice the general efficiency of a normal air conditioner reduces energy use during summer months when it's highest, and also makes use of all the spare capacity that ends up in the winter when people are heating.
It still seems to me that GSHP would be the best long term solution. While the amount of panels or turbines is costly now, using them with GSHP seems the only way you could get down to a "zero" carbon footprint (if you buy into the idea of building and installing a turbine or solar panel has a zero footprint).

geo pros should be noting the importance of how the electricity is produced,when they claim no greenhouse gases,
but this solar guys arguement is not taking into account that propane is being produced (and will definitely be burned)as a by product of nat gas production and propanes carbon emissions are sky high

This is the approach I am taking.  I created a tight thermal envelope to minimize the size of the geothermal system.  That, in turn, is positioning me to have a much smaller solar array to take my home to net zero when the economics of a solar PV system makes more sense to me.

It appears the home building industry may be getting on board with this thinking as well.  This month's Professional Builder had a story (see attached) about how to pitch high-performance homes.  In the article, they discussed the 3-pronged approach: 1) thermal envelope 2) geothermal, 3) solar.

Also looking at the http://www.eia.doe.gov/ site for the US the average output of all the coal fired power plants combined (in 2000) was just under 1 lb per 1kw produced. In his document he has the CO2 at almost 2 lb per 1 kw produced. Most new power plants are in the 1/2 lb per kw range. So CO2 wise geo beats nat gas hands down without even considering other energy sources.

I run our geothermal system only in an off peak situation, so I use the power when the power plants are essentially making excess power at $.054/kw and our natural gas right now is at 1.12/therm (lowest it's been in a while). Even assuming a COP of 3 and even at these rates that’s is still over a 50% savings with geo compared to gas.

One last thing he didn't take in to consideration. I have reduced our natural gas consumption by 5 therms a week since our natural gas water heater doesn't run because of the de-super heater.

I am confident I am paying about ½ to 1/3 less for energy running geothermal compared to traditional natural gas. I will admit though that if we didn't have time of use or demand electric rates the savings would only be about 75% of what the natural gas would have been.

With no offense is intended to any one here (!!!). We all tend to talk out of both sides of our mouths regarding certain things. While at least three heat pump manufacturer's claim to have the most efficient systems, we all nudge each other as we understand that they're right as long as the entering water and air temperature are right (and the sun/moon and stars are in alignment)...oh and we heat best in my climate with open loop and cool best with closed loop..... Let's not forget the discussion of the most earth friendly way to heat the pool...
Frankly my belief is that if you pay less it likely is earth friendly (as it indicates less ENERGY expended).
By the way, solar and windmill manufacturing plants are generally not run on solar panels or windmills.
J

Brock, can you point out to us where on the site you found this. I found a referance at http://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/C02.htm that claims 970 grams of CO2 is producted for every KWH of power, that's roughly 2.1 pounds of CO2. 
 

From my e-mail to him about it
Gary to me
show details 7:03 PM (14 hours ago)

Reply

Hi Seneca,
The AFUE furnace test (as I understand it) is a realistic test of the furnace and (now) even includes electrical energy to drive the fan. My understanding is that it tests the furnaces in a way that closely represents actual use in real situations with realistic on/off cycles. Can you tell me where the data is that says and AFUE 90% furnace only does 75%?

The reasoning I used to pick the default heat pump COP is explained here:
http://www.builditsolar.com/References/Calculators/Fuels/HeatPumpCOP.htm
This is the best data I know. People are free to put in any number they want to.

I know your opinion on the COPs that gshp's achieve in the field, but what I really need is DATA from a reputable source that backs it up. The material I used is the best I could find, and I'm not going to change it until I find, or someone provides better data from a reputable source.

Best,

Gary


http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/13/postid/42441/view/topic/Default.aspx

I also took a look at the calculator you use
http://www.infinitepower.org/calc_carbon.htm
If switched to using gas for the source of energy (assuming the natural gas not used for the home heating became used for energy for geothermal) it comes out to almost even, using a even the CoP of 3. Of course, that fails to take into account field operations are seen around 4.5 CoP's, and the actual in field install of a 90%+ gas furnace is usually around 75%. It's a little crippled to assume the geothermal gets less CoP's in the field than the factory statement, but that the gas furnace actually meets the efficiency stated. Also, it still doesn't factor in gas furnaces also using electricity to run.

He probably used the link to emissions at http://www.eia.doe.gov/environment.html inside the http://www.eia.doe.gov/oiaf/1605/ggrpt/pdf/statemethod.pdf file there is http://www.eia.doe.gov/oiaf/1605/state/state_emissions.html

Yes from those ^

I would love to poke holes in this guys CO2 arguement, but everything I've found so far validates his Coal CO2 figures.
http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2emiss.pdf
Granted this inforamtion is 10 years old, Coal generating stations could have made some improvements since then, but the information I have available to today says 2.1 pounds of CO2 for KWh generated.

I did come across these figures,

1 short ton of coal = 20,754,000 Btu (2000 pounds in 1 short ton)

1 kilowatthour of electricity = 3,412 Btu

Which would give you 6,000 KWh per ton of coal, which in turn equals 3 kwh generated from each pound of coal, which would give some support to generating plants today are much more efficent then those 10 years ago. But i'm doubtful this much electricity can be generated, there are definite losses in the conversion process. Actually the efficency of coal is around 31%, so that pushes the figures down to somewhere around 1 KWh per pound of coal burned. Does anyone see actual current government figures that clearly state how much CO2 is generated per KWh generated?
   

Of course this ignores the fact that if natural gas isn't burned at a local furnace for heat, it can be burned at a power plant for energy, at which point, having only a CoP of 3.5, the calculator he references puts geo just slightly greater than a 90% furnace. At which point, even if you are breaking even on the heating season, there's also a cooling season where you've just installed an A/C that's twice as efficient as an energy star one.

I recently found this -
http://www.toolbase.org/PDF/CaseStudies/MeasuredPerformanceResidentialGeothermal.pdf
It shows five units that average a heat CoP that's 99.8 of the ARI rating (albeit their CoP's are not cutting edge). That's even including one unit has the installer running his fan constantly and his pump operating more than necessary. Also, the report said two of the units had EWT under 32 which was indicative of loop undersizing.

I swore it was in that same pdf, weird. I heard on the radio the new coal plant their building in Wausau WI was suppose to produce less then 1/2 lb per kw. I don't know how many scrubbers they have or what coal they are using (or does that just affect sulfur?)

Interesting, using the site the he does for the CO2 released by coal and gas
http://www.infinitepower.org/calc_carbon.htm
Even with a low COP of 3 as he uses, you'd make less CO2 burning natural gas to power a heat pump than you would burning the same 1.11 therms in 90% efficient furnace (41 pounds for GEO, 44 pounds for Natural Gas).
Seems like if (as is the case locally) you're an electric company that also provides natural gas, and you make profit on units sold - you have an incentive to have people use any percent efficient gas furnaces instead of geothermal for heating from a natural gas power plant!

he of course leaves out the fact that the natuarl gas furnace also uses some electricity. i get this all the time, i have the only geothermal system in my town, everybody always asks me what i have for back up for when the power goes out, i tell them 'the same thing they do with a electricaly operated natural gas furnace, nothing. with out power neither puts out heat'