Wednesday, July 2, 2008

Electric vs. Combustion Engine Efficiency

Today I'm trying to get to grips with future vehicles and wade through all the bad information out there. So starting with Electric cars vs. petrol/diesel. The combustion engine car is inherently inefficient, mainly because of the heat losses of the combustion process, but also losses through the drivetrain and additional load such as air conditioning. Out of town, efficiency improves with 20% reaching the types.

The overall efficiency of the electric car depends most signficantly on the source of electricity. If you electric car is recharged from your own windmill, the efficiency can be as much as 80%, but if power station losses and grid losses are also included that may drop to as much as 28%. Still better than the petrol car though.

Electric-Powered GM EV1Gasoline-Powered Acura .2TL

Start with1 million BTUsStart with>1 million BTUs
Energy left after generation (39% efficiency)390,000 BTUsEnergy left after refining (92% efficiency)920,000 BTUs
Energy left after charging losses (88% efficiency)>343,000 BTUsEnergy left after transport (95% efficiency)874,000 BTUs
BTUs per kilowatt-hour3412 BTUsBTUs per gallon of gasoline115,400 BTUs
Electricity available100.6 kWhrGallons available7.6 gallons
Energy efficiency0.19 kWhr/mileFuel economy>24 mpg
Miles per million BTUs529.5 milesMiles per million BTUs182.5 miles
Equivalent mpg69 mpgEquivalent mpg24 mpg

From a bit out of date

This would suggest, even with current technology, that you are greener to buy an electric car and charge it off the grid then drive an equivalent petrol car.

Here is a more entertaining comparison of electric vs. petrol. Mythbusters converted a petrol go-kart to electric and it performed almost as well as the petrol one, which considering it was nearly twice as heavy with the batteries, wasn't bad going.

1 comment:

Phoebe Bright said...

Hacked electric motorbike - seriously cool