Thinking of buying an electric car and saving the planet?
If you look at the diagram above (Sorry for the poor quality), you’ll see what is required to get the power for the car battery from the source.
Lets look at the efficiencies of the various parts of the diagram, starting with the generating station first. Even a non CO2 emitting nuclear plant is at best 30% efficient due to the lower steam temperatures employed. That’s a start down the slope.
Next comes the step up transformer. Ever wondered why they have to be oil cooled? Using a step up transformer to increase the voltage does not give you something for nothing. As the voltage goes up, the current goes down by the same proportion. The power equation shows that the overall power remains the same.
P=V x I Power = Voltage x Current
In reality, the power output is always less than the power input because the changing magnetic field in the core creates currents (called eddy currents) which heat the core. This heat is then lost to the environment, it is wasted energy. It’s actually not too bad at 2%. But 2% never the less.
Now we come to transmission of this power. This is usually transmitted at voltages of around 133kv in the UK for long distances. Here again we lose energy. Estimated at approximately 6%.
Of course we now have to transform it down again to a realistic voltage for consumers to use. Another 2% lost.
Bearing in mind charging the batteries of your electric car is going to involve turning that AC voltage into a DC voltage and step down to a voltage that will be suitable for your battery, the efficiency falls further. Lets say another 2%.
Overall by my reckoning that makes the whole jiggery pokey to have you on the road is about 58% efficiency overall.
Contrasting that to a modern common rail fuel injected diesel engine at 50% efficiency, the efficiency is not vastly better.
Of course you have to buy the car first before you can drive an electric vehicle on the open road. Now the agony really becomes real. Even with a generous government subsidy (£5,000), a Nissan Leaf is going to set you back a whopping £25,990.
And for that price you only (On a good day) get a mileage of 109 miles between charges.
And finally the cost of a replacement battery will set you back over £5,000. (Conservative price. Some sites have reckoned it could be as high as £8,000).
Still want to buy one? Me. I’m sticking to my diesel powered car, which has a range of 350 miles even when my heater is on in the winter. I don’t want to take 3 days to visit my son. (And three days back) After all, who would feed the cats?
