Tesla

[HPsauce]

Originally Posted by Goran

generating efficiency is ignored because the source is assumed to be the same for both, be it coal or nuclear.

We can ignore oil tanker because we assume the tanker delivers fuel to the same UK power plant for both electric and fossil fuel cars. So its trucks vs cables for comparing car efficiency.

Well, sadly no. Your maths are not logical.

[Goran]

Please elaborate.
Ok, crude oil to electricity power plant efficiency is 34% says Siemens, global coal power plant efficiency is roughly 33%
So it makes no difference, you may as well burn the crude oil to generate electricity, skip the refinery step and deliver it to electric cars. Total efficiency comparison is then (ignoring oil extraction which you must do for both)
electric car
0.34 x 0.85 x 0.68 = 0.197

diesel car
0.34 x 0.88 x 0.41 = 0.12

again generously ignoring the tanker trucks.

Please share your calculation.

[HPsauce]

I'd not include the 0.34 in the diesel calculation. So that would be nearer 30%.

No doubt there are other factors, but overall not a huge difference between electric or petrol/diesel, though my suspicion is that electric is actually less efficient if coming from fossil fuels.

I don't have a formula, remember all I initially said was:

Originally Posted by HPsauce

Greenness. This is largely down to the source of your electricity. Traditional power stations (coal, oil, gas) are no better and probably much worse at generating motive power per "CO2" than petrol/diesel. Once we get to a high level of renewables then the chain of energy delivery probably needs a rethink.

I think your formulae/calculations largely support my initial guess (highlighted in bold).

[Goran]

Originally Posted by HPsauce

I'd not include the 0.34 in the diesel calculation. So that would be nearer 30%.

No doubt there are other factors, but overall not a huge difference between electric or petrol/diesel, though my suspicion is that electric is actually less efficient if coming from fossil fuels.

I don't have a formula, remember all I initially said was:

I think your formulae/calculations largely support my initial guess (highlighted in bold).

I am happy to learn where I am going wrong. Refinery requires energy to run. It requires a lot of electricity. There are no IC engines for efficient crude oil combustion. Therefore you can't lose the power plant efficiency factor for IC engines.

Also 41% is unrealistically high for real world consumer diesel cars, I was too generous. And we didn't mix in petrol, what percentage of cars in the UK are petrol.

Of course if we said nuclear plant for electric cars then IC engines would lose out even more. There is just no way around that huge electric vehicle drive train efficiency factor of 68%.

[HPsauce]

Refineries are actually pretty efficient, as are many/most other processes in both chains.
The really BIG losses occur when hydrocarbons are burnt to generate power;
1. In power stations, typically running around 30% efficient
2. In vehicle engines, again around 30%

Electric vehicles (ignoring all the battery issues) will probably only become "better" in that competition when they can use power from alternative sources.

[Goran]

They are efficien with the electricity they receive, but does that take account of the efficiency to produce that electricity? They produce some of their own electricity and take at least 15% from the grid.

The earlier quoted efficiency of 88% is the overall internal efficiency for all products. What is the efficiency of producing gasoline and diesel? Here is one rough figure:

"U.S. refineries produce about 19 gallons of motor gasoline, 12 gallons of ultra-low sulfur distillate fuel, most of which is sold as diesel fuel, and 4 gallons of jet fuel from a 42 gallon barrel of crude oil."

http://www.eia.gov/Energyexplained/i...e=oil_refining

That does not take into account the barrels burned to deliver the fuel, or the efficiency of the electricity to produce it, and yet they still only get only 74% of motor vehicle fuels from each barrel of oil. I still maintain burning crude at a power plant to power electric vehicles is more efficient than to refine it for motor vehicles.

New info, we can use the more efficient way of generating electricity from oil, 75% replacing the earlier 34% figure putting electric vehicle efficiency from crude oil way in front.

http://www.exxonmobil.co.uk/UK-Engli...ng_fawley.aspx

[HPsauce]

That 75% is really interesting but it's actually a CHP (Combined Heat and Power) unit, so yes it's 75% efficient in that only 25% is "wasted" but a lot of it is used for heating.
Quite probably heating used in the refining process.

(PS I used to work for Esso and later BP and do know a fair bit about refineries)

By the way, refineries produce the mix of fuels that they are designed to produce and this can be adjusted or changed, though big changes are not necessarily easy.
Producing 19 gallons of petrol from 42 gallons of crude means little or nothing in efficiency terms, it's certainly not 19/42 (45%).
A better measure is how much total energy is in the output fuels vs how much is consumed in the process. That may be the 88% you mentioned.