Blog for newenergydirection.com

As a follow up on the last post Cost Of Electric Vs. Gas Powered Vehicles, I decided to compare the annual greenhouse gas production of a vehicle that burns gas, and of a coal generating plant that charges an equivalent electric vehicle.

Using my Corolla as an example, as before, it produces 5.90 US tons of greenhouse gas (CO₂) annually (ref: http://www.fueleconomy.gov). Using data for my car as taken from the latter website, 5.90 tons is equivalent to 15,000 miles of combined city and highway driving.

Using 33 mph as the average city and highway driving speed (ref: http://auto.howstuffworks.com/28004-epa-fuel-economy-explained1.htm), the total time to drive 15,000 miles = 15,000/33 = 454 hours. This speed of 33 mph is based on a weighted average of 55% city driving (at an average speed of 20 mph), and 45% highway driving (at an average speed of 48 mph).

Since it takes roughly 5 hp = 3.7 kW to maintain an average speed of 33 mph (ref: http://pics.tdiclub.com/data/516/Fuel_Economy_2.pdf) for an equivalent electric powered car (to overcome air drag and friction), the total net electrical energy consumption is 3.7×454 = 1680 kWh. Assuming a combined motor and battery efficiency of 68% (explained in the last post), the total electrical energy input into the car is 1680/0.68 = 2470 kWh.

Now, coal generating plants produce roughly 2 kWh/kg-coal of electricity. And each kg of coal produces roughly 1.83 kg of CO₂ (ref: http://en.wikipedia.org/wiki/Coal).

Assuming 90% power line efficiency, we can estimate the annual CO₂ emissions produced by a coal plant to charge your car for one year, assuming average city and highway driving.

Annual greenhouse emissions = (2470/0.90)x(1.83/2) = 2510 kg = 2.8 US tons.

This is an interesting result. It says that using gas for your vehicle is much more polluting (5.90 tons of CO₂/year) than using a coal burning plant to charge an equivalent electric vehicle (2.8 tons of CO₂/year).

Burning coal produces less than half the pollution that burning gas does. Of course, coal burning plants must be phased out anyway, but even as one of the dirtiest means to produce power they are still much less polluting than gas for the same amount of energy.

This entry was posted on Saturday, October 25th, 2008 at 12:14 pm and is filed under Electric Vehicles. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.