In message , at 11:41:13 on
Tue, 17 Jul 2018, The Other Mike
remarked:
What's important for the EV-charging scenario is that is if several
dozen houses are supplied by an 200A street main at 230v from the local
substation, how can more than a handful charge an EV overnight at 50
amps?
They won't all need to fully recharge a car every night.
Of the many cars parked on a street, plenty of them just aren't used
most days. And of those that are used on any given day, plenty aren't
used much - just a trip to the shops, or the school run, or to a nearby
employer.
This depends a lot on the local demographic. There are plenty of estates
where at least one breadwinner per household is likely to drive to work
(and the national average commute is 67% by car, 30mins).
Where I live that's dominated by the 35 mile round trip to Cambridge,
unless they take the fastest route which is 50 miles round trip.
So with a 35 mile round trip, maybe averaging 35mph, that's one hour
per day, or five hours usage a week, add on another hours usage for bit
for shopping etc and a day off on sunday and that leaves some 162 hours
a week for a charge to take place.
The commuter will typically be at home for 14hrs a working day, that's
98hrs. What they do at weekends is very much a lifestyle issue, but they
could never clock up another 64hrs indoors.
210 miles in a week is just under 11000 miles a year which is high by
average private motorist standards (see below)
Average motorists include those who aren't commuters.
At 18kWh/100 miles for a Nissan Leaf (BMW i3 is similar as is the claimed
performance for the Tesla Model 3) then it needs some 1980kWh per annum of
charge.
If 100% of that charge takes place at home then it can take place spread across
100 hours a week (12 hours a day weekdays + 24 hours sunday + 16 hours on a
saturday)
It needs 38 kWh per week to do those 210 miles
Ignoring charging losses that equates to an average mains supply load when on
charge of around 380W, or 1.6A at 240v
As it is the average UK private mileage is (was) 7900 miles in 2013, down from
9200 miles in 2002
https://www.bbc.co.uk/news/uk-england-28546589
So for the 'average private motorist' the average mains supply load when on
charge, for charging purely at home, drops to around 270W or 1.125A at 240v
You need to read the National Grid papers on the subject, which suggest
that even with reasonable remediation measures the whole thing falls
over at about 20% EV penetration by 2030.
--
Roland Perry