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Re: 7.5 kWh of electricity to produce a gallon of gasoline?

Fri Dec 09, 2011 9:55 pm

drees wrote:
TRONZ wrote:Ahhhh! OK then. So this statistic says that by NOT producing the gallon of oil, the 7.5Kwh of lost electricity is never wasted in the first place?!?
Not electricity, but energy - most likely oil used to power drilling rigs and ship it to the refinery.

Some electricity is probably used, but as others have mentioned most of it comes from byproducts of the refining process.

Basically think of it this way: For every barrel of oil you pull out of the ground, you use 17% of it to get the next barrel out.
The 7.5kwh/gal of gasoline doesn't come from exploration, production and transport energy. It is mostly the thermal energy used in the refinery (attributed to gasoline only, even though there are other refined products).

Here's some different data that pretty much boils down to the same results discussed so far, from Profile of the Petroleum Refining
Industry in California
(contains data for all of the US, too) It's 2001 data, but the relationships probably haven't changed much.

In 2001 US refineries consumed about 3.3 quadrillion Btus (Quads or 10^15 Btu) of primary energy to produce all their refined products. Primary energy for a refinery means natural gas and crude oil. Electricity purchased from the outside is converted to primary energy using the prevailing rate for the mix on the grid being considered (usually a factor of about 3 for the whole US). You can convert the 3.3 Quads to about 9.7x10^11 kWhs, but this is not electricity, just thermal energy of fossil fuels reported in kWhs. If it was electricity, at something better than 3 mi/kWh wall to wheel for an EV, you could indeed drive all the 3 trillion US vehicle miles traveled (VMT). Although, a lot of those vehicle miles are heavy trucks that couldn't get 3 mi/kWh. Anyway, if you really wanted to take the primary energy consumed in oil refineries and turn it into electricity, you'd have to suffer the roughly 3 to 1 thermal to electrical efficiency of a thermal cycle plant, and you could now power about 33% of US VMT.

Still, it is striking that this is only the energy consumed in the refineries for their operation. It is not any of the energy of the refined products coming out. Nor does it include any of the energy of exploration, production or transportation, as many have already pointed out.

By the way, if you divide 9.7x10^11 kWhs by the roughly 1.3x10^11 gallons of gas a year consumed in 2001 your will get something pretty close to the 7.5kWh/gallon figure.

When it comes to electricity purchased from the outside by oil refineries, they use a comparatively small 34 billion kWhs, good for 100 billion miles of driving at 3 mi/kwh, or only about 4% of US VMT in 2001. Onsite co-gen facilities generate some of refinery electricity from process heat (about 25% of total electrical consumption).

This is no defense of the oil industry. I think these numbers point out that they use a shocking amount of energy to process gasoline fuels, not to mention all the other activities necessary to deliver this fuel, but I though it was worth trying to be more explicit about the particular number being discussed and what it really means, although it has already been pretty well beaten to death here and elsewhere. EVs are clearly a vast improvement over the this inefficient, oily morass of petroleum.


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Re: 7.5 kWh of electricity to produce a gallon of gasoline?

Sun Dec 18, 2011 1:40 am

I did this calculation and for Alberta oil sand with an EROEI of 3 this works out to being able to drive just as far with your EV simply on the natural gas that would otherwise be required to extract and refine an equivalent amount of gasoline to drive a regular gasoline powered car the same distance. ... tric-cars/" onclick=";return false;

It blows my mind that people can believe we aren't running out of oil when global oil production hasn't increased in 10 years, and we have to now rely on oil sand with an EROEI of 3, and the whole deposit amounts to 6 years of global oil consumption. It's mass media brainwashing, keeping the facts away from the average person. And the oil companies want to put in a nuclear power plant to refine the oil sand. So ... we have to build a nuke plant to ... provide energy to extract energy from ... another energy source? It's the most ludicrous thing I've ever heard. But our politicians and corporations have become so blinded by their short term profit that they don't understand what they are proposing.

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