Assuming you mean there are other greenhouse gases somehow associated with the CO2 from burning gasoline, I would defer to you on the magnitude of that factor. However, there must be a corresponding factor for greenhouse gases associated with the CO2 from burning coal. Maybe not as much, but it might be easier to get a real number.

Then we could consider electrical energy production, either from coal or natural gas and energy production from a mobile gasoline engine. Then we could work out how much of the added electricity demand will come from coal.

Of course, because you produce electricity from solar, this will not be meaningful in your case. However, I see no likelihood that purchasers of the GM Volt will act as you have, whether they don’t see the point or can not afford to.

Thanks for the discussion. Yes there is more to do, but my main point is that electricity must not be considered as a source of energy without accounting for the heat lost in producing it. The plug to wheels approach does this and thus gives a fuel efficiency advantage factor of about 3 to the electric car over any car that carries its own engine.

If we have good data on the amount of CO2 that is emitted nationally in producing electricity for each of the various types of fuel, you can know quite accurately how much heat that represents. Simply knowing the amount of electricity produced from the respective fuels makes it very easy to calculate thermal efficiency. See http://www.miastrada.com/analyses.

I understand that there are some differences in energy losses and emissions in the well to burning point processing for the various fuels, but in comparing coal to natural gas, these mostly make coal worse. Oil is much more complicated since there are so many by-products, though I roughly judge it to be not too different from coal. And as far as oil goes, getting believable data is not easy. So I think I will be satisfied with making comparisons from “burn point to wheels.”

I think it is a reasonable approximation to determine greenhouse gases as the CO2 product of combustion.

The amazing thing is the widespread perception that large power plants are especially efficient. It was a surprise to me how bad they really are.

So as you point out, I believe some things and not others. However, I try to be realistically skeptical. Where there is raw data that is not subject to the possibility of biased analysis, I feel more confidence. I have some experience with how it is as an analyst working under contract to others.

In my mind, the next most important point is trying to figure out how power plants really operate. I have been stuck trying to get California data, and have had to depend on scattered information with assumptions and expert’s opinions that help, but can be well off the mark. However, the real Province of Ontario data gives some approximately valid insight. See the post of Sept 29, 4:23pm.

What you say about refineries using electricity is shocking. Do we have a way of knowing how much of that went into the many by-products of oil? But notice, even putting that full 4.7% burden on gasoline, it is still not so much in comparison with the 200% burden on electric power production.

I don’t see how you can compute the GHG per mile from thermodynamics. You need a lot of data. Wells to Wheels starts at the well for example. Then you have the GHG emissions to put it a tanker and move it to the US. Then you put it through a refinery, which has a lot of GHG emissions (they use a lot of natural gas and electricity at refineries, e.g. in 2006 refineries use 39 TWh!). I don’t see you counting refinery emissions, for example. Then you ship that gasoline to stations (more GHG emissions). Then you drive your car and emit the last GHG. You need to separately track the CO2, CH4, NO2, etc. emissions, multiply by their GWP and add up. For electricity you do the same thing, except you have to do it separately for coal, natural gas, nuclear, hydro, renewables, and other. This is not thermodynamics, it is bookkeeping. This is what ANL did in the GREET model. Just gathering the data took years, I expect. You’re welcome to second guess GREET if you want (call back in a couple of years and let me know if they were right or not).

Jim wrote, “And of course, I should practice my own advice. It is a little obscure but I have hard data from Argonne reports that the Prius engine thermal efficiency is 36% or 36-38% or 38% from various dynamometer results and a summary statement. See: http://www.transportation.anl.gov/pdfs/HV/399.pdf http://www.transportation.anl.gov/pdfs/HV/416.pdf”

Ah, you trust ANL to get this right! Actually the numbers seem about right, given that 33,694 Wh/gal * 36% / 46 MPG = 264 Wh/mi. I would have guessed motor to wheels for the Prius to be 230 Wh/mi, which is in that ballpark.

Jim wrote, “You get about 30% more CO2 per BTU produced from coal. See http://www.miastrada.com/analyses for a solid power plant efficiency calculation as well as more exact CO2 data.”

If you trust the EPA on that, why not just use their GHG/kWh for the US grid? Isn’t that a lot simpler?

Jim wrote, “Power distribution losses are around 7%. Electric motors and generators are not likely to get more than 92% efficiency. Chargers can vary a lot but I would expect about 95% efficiency from a very good one. Mechanical power ransmission losses in the Prius are, and this is a rough estimate, 10%.”

This is all fine, but it is not enough to calculate GHG emissions. Where’s the rest?

Jim wrote, “With this basic data, there is no need to argue from authority.”

How do you do the analysis without depending upon authorities for the data with which to do the GHG calculations?

Jim wrote, “I am trying to look carefully at the best balance between battery capacity and engine driven generator capacity for an experimental car I am developing. I think I have a very efficient aerodynamic concept which will make it reasonable to use both plug in and auxilliary diesel as electric power sources. Do you still think my conclusions are false?”

Which conclusion? You haven’t done one yet that I can see. You’ve outlined the start of a calculation. When you complete it, I am sure you’ll find that plug-ins charged from the US grid are less than half of the GHG emissions of gasoline powered internal combustion vehicles, and about 25% less emissions than hybrids. The answer would be even more favorable to the plug-ins if you use not the averages for the U.S. grid, but its marginal GHG/kWh.

Jim wrote, “I appreciate you pointing out where you believe I am wrong, and hope you see this as a serious answer.”

I don’t see you as wrong here, just not done. Keep going.

By the way, did you know that the 39 TWh of electricity used by US refineries in 2006 could have powered BEVs driving 4.7% of 2006 US passenger vehicle miles?

You might agree more with me if you based your thinking on thermodynamic basics and built your arguments on such. I am afraid that Argonne and EPRI are a little too dedicated to supporting the results pre-determined to be true by their financial sponsors. Even still, they do provide useful data which I appreciate.

And of course, I should practice my own advice. It is a little obscure but I have hard data from Argonne reports that the Prius engine thermal efficiency is 36% or 36-38% or 38% from various dynamometer results and a summary statement. See: http://www.transportation.anl.gov/pdfs/HV/399.pdf
http://www.transportation.anl.gov/pdfs/HV/416.pdf

You get about 30% more CO2 per BTU produced from coal. See http://www.miastrada.com/analyses for a solid power plant efficiency calculation as well as more exact CO2 data.

Power distribution losses are around 7%. Electric motors and generators are not likely to get more than 92% efficiency. Chargers can vary a lot but I would expect about 95% efficiency from a very good one. Mechanical power ransmission losses in the Prius are, and this is a rough estimate, 10%.

With this basic data, there is no need to argue from authority.

I am trying to look carefully at the best balance between battery capacity and engine driven generator capacity for an experimental car I am developing. I think I have a very efficient aerodynamic concept which will make it reasonable to use both plug in and auxilliary diesel as electric power sources. Do you still think my conclusions are false?

I appreciate you pointing out where you believe I am wrong, and hope you see this as a serious answer.

The date of the reference you cited was published in July 2001. The price of natural gas over the decade preceding this date was consistently very low, and much thinking at that time was based on very different power plant operating assumptions. The EPRI thinking seems to have been much like the Calpine thinking of that date, they of course found the reality to be drastically different than the planning basis. (Calpine went into bankruptcy, just emerging a few months ago, with a lot of very unhappy investors left behind.)

In this light it seems understandable that in 1991 they would dismiss the importance of coal and seemingly make hasty assumptions about the nature of coal power plant opertions.

As I said before, we don’t know what the real schedule is for California. However if the technology in Ontario is remotely similar, the EPRI stated assumptions are very inappropriate. Specifically they say that coal plants will not run at night when electric vehicles are being charged. In Ontario, there are 11 power plants having non-zero capability. Of these, on Sept 16 this year, one operated during the day and was turned off at night. Two ran at a continuous output level which was about a fourth of their capability. The remaining eight ran full on during the day, but were scaled back varyingly from 25% to 75% but were never close to being shut down.

This same data shows some interesting facts about dependability of wind production.

Perhaps an authority such as yourself could come up with some real power plant data for California?

I rebutted our false claims about the Prius using Wells-to-Wheels data from Argonne National Labs’ GREET 1.7 model, as run by the US EPA/DOE, and the data presented upon their webpage. GREET, as wells-to-wheels model, incorporates CO2 from all sources along the energy supply chain.

The EPRI study also used GREET (1.5). MPG doesn’t enter into it.

You’ve got it wrong, not EPRI. You’ve got no basis for making the false claims you did.

I am pasting their formula in quotes:

“This can be converted to miles per
equivalent gasoline gallon (mpeg) by dividing the electric-only fuel economy in kWh/mi into the
conversion factor of 33.44 kWh/equivalent gasoline gallon.”

One gallon of gasoline and 33.44 kWh of electricity produce the same amount of heat. However, to generate the 33.44 kWh of electricity requires approximately 100 kWh of heat. The practice of ignoring thermal conversion efficiency demonstrates lack of understanding of physics, specifically the Second Law of Thermodynamics. See Sears, Physics, Mechanics, Heat, and Sound 1950 for a good explanation that most engineering graduates should have been exposed to as college freshman. It seems many never really learned this topic. A lot of engineers never have had an occassion to think about it, but real physicists have to know it.

No doubt there will be protests that hydro, solar, and wind are not exactly subject to this rule. There is a concept of marginal capacity in power generation which is relevant. This is the capacity that is available and economically sensible to bring on line in response to an increase in demand. Since hydro, solar, and wind are already being used to their full capacity, there is no marginal capacity for this. The use of natural gas generators, which also take a huge hit due to thermodynamics, is more complicated since the marginal capacity of generators using this fuel exists for complex reasons including the fact that much of this capacity was committed to and hugely invested in when natural gas was $2 per MMBTU. Government muddies the issue with regulation and price controls. However, the only sustainable and sensible long term use of natural gas is where there is a cogeneration process going on, such that natural gas can actually be price competitive with coal.

California is not forthright in publishing their power generation fuel schedule, or at least not that I have been able to shake loose. I recently found a data resource for the Province of Ontario, where a real idea of the truth can be gleaned. I am still analyzing, it but the whole picture is there to work with for that Province. They do quite a lot of cogeneration. As far as I have been able to tell the only natural gas generators that work steadily are this kind of plants. See http://reports.ieso.ca/ public/ GenOutputCapability/ PUB_GenOutputCapability_20080916.xml

If you don’t use the right formulas and you refuse to think about how power generation works, you and EPRI can both get things wrong.