philaphonic wrote:Running through some publicly available stats, I thought I was going to come up with some zinger of a condemnation against the refinery industry, in the sense of energy used to refine a gallon of gas. But unless I got some basic math wrong, it looks pretty efficient. Feel free to verify:
In 2005, US refineries processed 6,250,625,000 barrels of crude oil, and 48% of the output was gasoline (1). They used 48,891,000,000 kWh of electricity to do so (2), resulting in 89.4 Wh electricity consumed for every gallon of refined gasoline produced.
48891000000 / 6250625000 = 7.822 kWh/bbl crude oil
42 gallons/bbl -> 7.822/42 = 186 Wh/gal crude oil
186 * 48% = 89.4 Wh/gallon refined gasoline
The chemical energy in one gallon of regular unleaded gasoline is 33.44 kWh (3).
Good analysis! I've been looking for this information for awhile and I think you most likely have a good ball park number.
However, there are a couple of complicating factor that we may have to take into account.
1. You assume that since 48% of the output of the refineries is gasoline, that 48% of the energy is used to create gasoline. I do not know if this is proportional. I would guess that some of the products of the refinery would need less processing, and therefore less electricity (motor oil, fuel oil, etc) and some would need more. In the end your assumption may be correct, but I would tend to think it would underestimate the energy needed.
2. Another assumption is related but subtly different. Can we assume since 48% of the output is gasoline it is the direct processing of 48% of the input? Put another way, are ingredients added or removed during the process for the different products so that 1 gallon of gas takes more (or less) than 1 gallon of crude oil to produce? I did find this bit of information, but I think it may make it even more confusing. In it are links to some other pages that seem useful...just don't have the time to chase them all down. http://fatknowledge.blogspot.com/2007/0 ... arrel.html
So in the end, let's say your number is just a bit low, and we round it up to an even 1kWh/gallon of gasoline. If the national average of fuel economy is currently about 20mpg, this would mean that in addition to the gasoline burned, every car is also using about 5kWh or electricity to go 100 miles. This means for every gas car that is replaced by an EV, the net demand on the grid goes up not by 25kWh/100miles (approx) but only 20kWh/100miles.