"williamwright" wrote in message
...
Says the Times. How are the charging stations going to cope with that?
Hmmm. A lot hinges on what they mean by "charges in five minutes". If the
battery is 95% charged, they can charge it to 96% in five minutes. But that
doesn't tell you much. The important statistic is how long to charge from
almost empty to almost full. In other words "every n miles, you need to
factor in a 5-minute fuel stop".
My (diesel) car has a range of about 700 miles on a 60-litre tank. Diesel
has an energy density of about 38 MJ/litre.
If (and this is a big assumption) an electric car needs about the same
amount of energy to travel the same distance, then that's 60*38 = 2280 MJ
(2.28 GJ). And that energy needs to be supplied in the stated 5 minutes (300
seconds).
OK, so the power needed is 2280/300 = 7.6 MW.
Ouch!! That's equivalent to the power used by 1000 electric showers.
But maybe that's not a fair comparison.
https://www.fueleconomy.gov/feg/evtech.shtml says that an electric car is
about 75% efficient whereas a petrol/diesel car is about 12-30% efficient
[that's a very wide range, I suppose going from a gas-guzzling petrol engine
to a more economical diesel].
So we can reduce the figures - let's say that an EV needs about 1/3 of the
energy of a diesel to take into account better efficiency.
And maybe we're happy to go back to the bad old days of a car with a range
of maybe 300 miles.
So reduce the energy needed by a factor about about 6.
That's still a charging power consumption of about 1 MW. Can the electricity
distribution system cope?
Suppose the charging process is 99% efficient - ie only 1% of the
electricity is wasted as heat. That's still a power of 1/100 MW or 10 kW. So
the batteries and the charger have got to dissipate waste heat equivalent to
three 3-bar electric fires. Gulp!
Then there's the other little matter. If new gas boilers are going to
outlawed, all the energy for people's central heating and hot water will
need to come from electricity. Oh, but we're closing coal- and gas-fired
power stations. Where the F do people think all this extra demand for
electricity is going to come from? How much of the country will need to be
covered in wind turbines?