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Do Electrical Cars Produce Less CO2?

Last Updated on Monday, 23 October 2017 10:49





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Do electric cars produce less CO2 given that the electricity they consume is from a fossil fuel electricity grid?

Many consider that electric cars produce no CO2. Well in operation this is true they do not, however when they are charged they take electrical energy from the electrical power grid which has in turn been generated by 80% fossil fuels.  The upshot is that using an electric car will also produce CO2, but according to the calculations below it is about half that of a car powered by internal combustion and in the UK it could cost 3 times less than petrol!  This is great, but the technology infrastructure for electric cars is still some time off, so don’t run off the car showroom yet!

Taking a fairly small and efficient car, petrol (gasoline) or electric, it will require about 0.13 kWh of energy from the power source to drive it 1km at a reasonable speed.

Internal car efficiency Source energy required per km Volume / Amount of fuel source required per km Price per km CO2/km
Petrol 20 % 0.65 kWh 0.07 l/km 7.55 pence/km 0.155 kg/km
  losses mostly in the internal combustion process and in engine idle Accounts for 80% internal losses There are 9.67 kWh of energy in a litre of Petrol (Gasoline) Based on £1.123 per litre On full combustion 1 litre will produce 2.3018 kg of CO2
Electric 80 % 0.16 kWh 0.16 kWh (grid) 2.5 pence/km 0.088 kg/km
  Losses mostly in the charge and discharge cycles of the battery some quote 83% Accounts for 20% internal losses Grid electrical energy Based on an average grid price of 0.154 pence per kWh The UK national grid emits 0.5394 kg of CO2 per kWh supplied, in 2008

The electric car at worst should produce half as much CO2 as the petrol car.   And with increases in renewable energy the use of nuclear for grid supply this will reduce further.   Interestingly the price per km indicates considerable scope to increase the cost of grid supply electricity for cars, which could in theory pay for the increased cost of renewable energy supply, or perhaps this cost advantage will be swallowed up in the cost of replacing batteries.

The paper in the link below is very good and seems to me to be accurate, but misses out any consideration for the costs of replacement batteries.

www.stanford.edu/group/greendorm/participate/cee124/TeslaReading.pdf

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