Virtual Cafe Scientifique, University of Southampton

Virtual Cafe Scientifique

What Wrong with EVs?

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In the UK in 2013 there are around 32 million cars on the roads. If only a third of us bought electric cars then the UK couldn’t generate and transmit the quantity of electricity that would be needed to charge all the cars. 

The Proof

If we assume that slow charge cars require 3kW to charge them over 8 hours and fast charge cars require 7 kW over 4 hours, and the majority of people will want to charge their cars overnight ready for the next day then: 

10million cars plugged in randomly overnight would draw a peak of 20 GW electricity to be generated from about 10.30pm onwards. On a winter’s night we currently need 55 GW so the extra 20GW would mean that we were running our generating stations at full power all the time. 

If more than 10 million cars were bought then the UK generating systems could not produce enough electricity. 

The Cables under our Roads

There’s another problem: the current we draw to run everything in our houses is transmitted along underground cables under our roads. When the national grid was put in, in the 1960’s, houses had far fewer electric gadgets. Typically the cables in the road can carry 100kW for 10 houses (10 kW maximum demand expected per house).

If half of those houses bought electric cars, then the demand would be 

5 cars x 6 kW on average = 30kW

Add this to the current level                                

(10 houses  x 10 kW  )  +  (5 cars x 6 kW)  = 130kW 

So the cables under the roads would need to carry far higher currents than they were designed to do. If many of us bought electric cars, then the cables under the roads would have to be replaced – with all the inconvenience and cost that that entails.