Thursday, 12 November 2015

Electric Cars - How Green Are They ?

Two blog posts today from guest posters - one on electric cars and the other on wind farm layouts.

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” 


  1. I deal briefly with this issue in video No 6 at 12.18 minutes in or google "valmartinireland you tube" . My figures are roughly the same as given here. Sales of these cars has slumped and a sighting of one being charged is a rare event. It is understandable that the public may not know about the intricacies of mains electricity generation, synchronisation etc, However, I cannot understand why they would believe electric cars run on nothing. They seem to believe the electricity coming out of the socket is "just there", provided by nature. How can such ignorance prevail after all that was spent on education. Some say computers have dimmed peoples brains, but I do not know. Meanwhile it was reported in yesterday's newspaper that the Irish government will create 260,000 jobs in exporting industry. With the 3rd highest electricity prices in the world, deluded again.

  2. The true environmental impact of all proposed technologies would be known if the Government had carried out a proper Strategic Environmental Assessment prior to finalising the National Renewable Energy Action Plan in 2010.
    Not too much evidence of that during last year's public consultation on the Green Paper on Energy Policy in Ireland, and not much evidence since then either. Adherence to doctrine at all costs is the mantra - critical thought is the heresy.

  3. Just another good article! Day by day, I'm getting lots of interesting articles on electric cars. This one is even much better that I read from the morning. You have made a good analysis on the carbon dioxide concentration that emitted by the fossil fuel and that result from the electric car. Really interesting comparison. Thanks a lot for sharing.