"Your electric car may not be so green"

[Jeff N]

I remember a post by Tesla Motors (not sure where, probably Facebook) when they say that the electricity to transport and refine one gallon of oil to produce gasoline is as much or even more than the Model S needs to drive the same miles as you could with that gallon of gasoline. It's really important to factor in all the pollution and cost and side effects of gasoline when comparing it to electricity.

Edit: found some good info on how much energy is used to refine oil here

This question is a frequent source of confusion.

The correct answer is that 5-7 kWh of energy, not electricity, is used to refine a gallon of gasoline. Only about 4-5% of that energy is in the form of grid electricity so therefore about 0.25 kWh of electricity is used to refine one gallon of gasoline. If you were careful you could drive about a mile on that in your Model S. The vast majority is from fossil fuels -- either natural gas or leftover unpopular (unsaleable) distillates from previous refinery output. Most of that energy wouldn't exist if you weren't already refining oil in the first place. All of the fossil energy used in refining would have to be run through an electric power plant before it could be used to power an electric car.

You can find all the details you ever wanted to know including the basic calculations and the breakdown on the different energy input types used in refining and why the recent FullyCharged episode "volts for oil" is wildly misleading here:

A petition to Toyota to build electric vehicles | Page 12 | PriusChat

 

[Robert.Boston]

Thanks, @Jeff N. A note in passing:

The vast majority is from fossil fuels -- either natural gas or leftover unpopular (unsaleable) distillates from previous refinery output. Most of that energy wouldn't exist if you weren't already refining oil in the first place. All of the fossil energy used in refining would have to be run through an electric power plant before it could be used to power an electric car.

The energy did exist, of course, stored as chemical energy in the crude oil. Had the gasoline not been needed, it would have stayed locked up, and with it all the carbon, particulates, etc. that get emitted when burned to refine the gasoline. We don't suffer from the lack of energy, but from the surfeit of carbon.

 

[ItsNotAboutTheMoney]

Thanks, @Jeff N. A note in passing:

The energy did exist, of course, stored as chemical energy in the crude oil. Had the gasoline not been needed, it would have stayed locked up, and with it all the carbon, particulates, etc. that get emitted when burned to refine the gasoline. We don't suffer from the lack of energy, but from the surfeit of carbon.

Or the pollution-be-damned way to think of it is that if you weren't burning it to help refine gasoline, you could burn all the cheap stuff to generate useful energy for other activities. For example it might be possible to burn it to produce heat, which could then be fed into a common heating system, supplanting NG heat, allowing you to use the displaced NG elsewhere for electricity generation, or other heating.

"They're not using electricity, they're using other really cheap, dirty fuel" is hardly a good excuse.

 

[dhrivnak]

Actually, I believe they do capture refining emissions since they use the GREET model as a starting point. But as William13 points out, there are many particulars that can throw off the results.

While they said they used GREET to cover car manufacturing I saw no reference, or footnote to indicate refining. Please correct me if I am wrong here.

 

[Robert.Boston]

While they said they used GREET to cover car manufacturing I saw no reference, or footnote to indicate refining. Please correct me if I am wrong here.

The GREET model from Argonne National Laboratories is the best well-to-wheel model of energy cycle costs.

To fully evaluate energy and emission impacts of advanced vehicle technologies and new transportation fuels, the fuel cycle from wells to wheels and the vehicle cycle through material recovery and vehicle disposal need to be considered. Sponsored by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE), Argonne has developed a full life-cycle model called GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation). It allows researchers and analysts to evaluate various vehicle and fuel combinations on a full fuel-cycle/vehicle-cycle basis.

 

[Jeff Miller]

Which brings me to my major complaint with this research article: the impact of EVs on the power system should be examined at the margin, i.e. what is the change in pollution? There will be no new coal plants built in the U.S. under current policies, and the older, less efficient coal plants will be shut down by 2020; the remaining, high-efficiency plants will be operating close to capacity. So where will incremental power come from to fuel an increase in EVs? Not coal, but natural gas, solar, wind, and water (and some nuclear, in some areas).

Agreed. There is an interesting recent paper which attempts to estimate the marginal carbon emissions from the current electrical generation mix by time of day (see the tables at the end of the paper) for each of the nine electricity markets. The data is from 2007-2009 so is a bit dated, but I would expect the results should still be reasonably accurate. When I used the data in the paper to calculate my carbon emissions from driving (I charge at 4 PM on the RFC grid), I think I got numbers that were close to the Prius. As coal is retired and cleaner capacity is added, marginal emissions should, as you note, decline.

 

[Robert.Boston]

I just took a glance at what my car is using right now, viewed from an average perspective rather than marginal:

That's 44% NG, 2% coal, and the rest from zero-carbon sources.

 

[Johan]

I just took a glance at what my car is using right now, viewed from an average perspective rather than marginal:
View attachment 66238
That's 44% NG, 2% coal, and the rest from zero-carbon sources.

Interesting!

Here's us:

 

[Canuck]

This is what's powering my car:

Electricity Supply & Generation

 

[techmaven]

This is what powers my Tesla:

North Anna Nuclear Generating Station - Wikipedia, the free encyclopedia

 

[Jeff Miller]

I just took a glance at what my car is using right now, viewed from an average perspective rather than marginal:
View attachment 66238
That's 44% NG, 2% coal, and the rest from zero-carbon sources.

The paper I linked to above claims (Figure 5, Panel A) that marginal emissions in New England are about twice as high as average emissions. This sort of makes sense given that the NPCC baseload is very low carbon - firing up gas plants to supply marginal demand, somewhat unusually for the US, emits much more than the baseload.

 

[Robert.Boston]

The paper I linked to above claims (Figure 5, Panel A) that marginal emissions in New England are about twice as high as average emissions. This sort of makes sense given that the NPCC baseload is very low carbon - firing up gas plants to supply marginal demand, somewhat unusually for the US, emits much more than the baseload.

Their figures also fail to capture the numerous retirements of high marginal-cost coal and oil plants in New England since 2009. It's really a shame that they didn't use current data in those markets where that was knowable. But regardless, if half of your energy comes from zero-carbon sources (nuclear, hydro, wind, solar), then almost by definition the marginal emissions will be higher than average.