Electric Cars - How Green Are They ?
by David Whitehead. BA(Mod. Nat.Sc.)TCD, FIMMM, C.Eng.
Electric cars have to be charged using electricity purchased from the state generating monopoly ( the ESB) which generates about 90% of the electricity sold annually from burning fossil fuels ( See SEAI website).
The efficiency of the Irish fossil fuel plants is published by SEAI every year along with the CO2 intensity is about 42%, as a lot of plants are Combined Cyle Gas Turbines, which will do 55% efficiency.
A diesel engine converts fuel to motive power at the rate of 3.3 kilowatt hours( kWh) per litre but a thermal power plant converts only at the rate of 3.0 kwh per litre or 90% of the efficiency of the diesel engine. Transmission and transformation losses amount to of about 5% of the electricity generated and the efficiency of a battery charge/discharge system is reckoned at 84% . An electric motor converts electricity to motive power at 90% efficiency. Thus the overall energy efficiency of the electric car in this system is around 67.6%.
Consequently in order to generate the same motive power the electrical generating system has to burn more fuel than the diesel engine - ie 1.48 litres per 3.3 kWh. In Ireland this results in the emission of close to 50% MORE CO2 than would be emitted by burning the equivalent amount of fuel in a diesel automobile.
For the scheme to be even CO2 neutral every electric car which was brought into service would have to have a shaft horsepower substantially less than a diesel powered car AND one diesel car would have to be simultaneously be removed from service. If both of these conditions are not fulfilled the total CO2 emissions simply increase.
The benefit to the owner of an electric car is that he/she has their road tax subsidised by by the owners of fossil fuel powered cars. It is just like the users of fossil fuel generated electricity subsidising the owners of wind turbines. Quite apart from that the reticulation of charging points that will be paid for by all road users/taxpayers whether or not they make use of it.
“the policy agenda on climate change has been driven recently more by ideology and target-setting rather than being informed by a rational assessment of what is possible and what is in Ireland’s interest, given the costs and benefits involved”