David A Stocks wrote:

A trickle-charge point is equivalent to a 13A socket inside a house. The
distribution system would barely notice that, even if everyone started
charging a car at the same time - we're talking about a system which copes
with events like a third of the nation's households putting a kettle on the
boil at the start of a TV commercial break.

Yes, but a third of the nation's households will still put the kettle on
during a commercial break... while their car is plugged in outside. Peak
loads add. (Give or take the fact that everyone's watching different
channels these days)

Fast charge points would
probably require rationing, probably by making them expensive to use. The
peaks in electricity demand tend to occur during the late afternoon when
cars are more likely to be out on the road than sat on charging points.

With a suitably non-trickle feed, the charging would be controlled so that
it takes place during the troughs in demand. You'd have to say something
like 'charge me by 7.30am' and the charger would know that if it hadn't got
enough cheap (aka trough) power by 4am it would have to charge on
'expensive' power. But you still need the grid and generating plant to
supply that. The system is a very complex series of many feedback loops, so
controlling it is quite tricky.

We're talking about a gradual take-up over the next 20 years or so, and it
should all be very predictable. I suspect the major challenge is
generating the electricity, not the distribution.

I saw a figure somewhere that a new HV national grid connection can take up
to 7 years. So you need a lot of planning.

Theo

On Mon, 25 May 2009, Roland Perry wrote:

In message , at 21:51:54 on Mon, 25 May 2009,
David A Stocks remarked:

And in London the problem is distributing the electricity from the
grid to the end users. Even if there was a plentiful source of
electricity, you'd have to do quite a lot of work to get it where
it's needed.

Just dig up the relevant bit of road/pavement and tap into the
existing domestic supply cables that are under every street. This
must have been the approach for the existing charging points, and
it's hardly rocket science.

You'll soon overload it if it's more than a few charging points per
street.

A trickle-charge point is equivalent to a 13A socket inside a house.

You want a bit more than a trickle charge - we were talking earlier about the
use of three-phase and up to 100amps.

But if you'd read either the Reg article or Mizter T's second post, you'd
know that Boris *is* talking about trickle charge - 2000 of the points are
to be 13A. Another 150 are to be 32A x 240V three-phase, which in power
terms are scarcely a problem (equivalent to about three sockets rather
than one), but will obviously access to a three-phase supply. The 200A x
500V charge points aren't given a target number, as they're still being
investigated.

Typical cars I've seen take about 3 hours at 12kw (that's 48amps) to
charge up.

That would put the amount of energy delivered at ~130 MJ.

The Reg reports that the 13A points will "charge a car over several
hours", and that the 32A ones will "deliver a decent charge to an EV in
roughly 30 minutes". The former would put the power delivered at somewhere
between 44 and 79 MJ, depending on where 'several' falls in the range 4-7
[1], the latter at 13 MJ.

That's obviously quite a disparity - or rather, two disparities, between
your number and the Reg's, and the Reg's two numbers! I don't know if
someone's missed some zeroes, or if you've just seen some real
electron-guzzlers.

tom

[1] If it was less than four, it would be a few, not several, hours, and
if it was more than seven, it would be many!

--
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gun bullets in slowar motian, juimping into a gun, dead police men,
computar hackeing, Kevin Mitnick, oven trailers, a old womans kitchen,
stairs, mature women in clotheing, head spark plugs, mechaanical squids,
Japaneseses assasins, tiem traval, volcanos, a monstar, slow time at
fastar speed, magic, wizzards, some dirty place, Kung Few, fighting,
a lot of mess explodsians EVARYWHERE, and just about anything else yuo
can names!

On Tue, 26 May 2009, Theo Markettos wrote:

David A Stocks wrote:

A trickle-charge point is equivalent to a 13A socket inside a house.
The distribution system would barely notice that, even if everyone
started charging a car at the same time - we're talking about a system
which copes with events like a third of the nation's households putting
a kettle on the boil at the start of a TV commercial break.

Yes, but a third of the nation's households will still put the kettle on
during a commercial break... while their car is plugged in outside.
Peak loads add. (Give or take the fact that everyone's watching
different channels these days)

Trickle chargers could be set up as frequency response units:

http://en.wikipedia.org/wiki/Nationa...eserve_service

Or something similar. Basically, at the point at which everyone switches
their kettles on, cars across the city stop charging for five minutes, and
resume once the tea is brewing.

Fast charge points would probably require rationing, probably by making
them expensive to use. The peaks in electricity demand tend to occur
during the late afternoon when cars are more likely to be out on the
road than sat on charging points.

With a suitably non-trickle feed, the charging would be controlled so
that it takes place during the troughs in demand. You'd have to say
something like 'charge me by 7.30am' and the charger would know that if
it hadn't got enough cheap (aka trough) power by 4am it would have to
charge on 'expensive' power. But you still need the grid and generating
plant to supply that. The system is a very complex series of many
feedback loops, so controlling it is quite tricky.

It is, but it is not (quite) beyond the wit of man. I think you're
suggesting something along the lines of what i suggested above, but
cleverer.

tom

--
unconstrained by any considerations of humanity or decency

In message . li, at
12:24:27 on Tue, 26 May 2009, Tom Anderson
remarked:
A trickle-charge point is equivalent to a 13A socket inside a house.

You want a bit more than a trickle charge - we were talking earlier
about the use of three-phase and up to 100amps.

But if you'd read either the Reg article or Mizter T's second post,
you'd know that Boris *is* talking about trickle charge - 2000 of the
points are to be 13A. Another 150 are to be 32A x 240V three-phase,
which in power terms are scarcely a problem (equivalent to about three
sockets rather than one), but will obviously access to a three-phase
supply. The 200A x 500V charge points aren't given a target number, as
they're still being investigated.

Unfortunately that number of charging points is a drop in the ocean.

Typical cars I've seen take about 3 hours at 12kw (that's 48amps) to
charge up.

That would put the amount of energy delivered at ~130 MJ.

The Reg reports that the 13A points will "charge a car over several
hours",

to *fully* charge would take 10 hours. Which is "several" in my book.

and that the 32A ones will "deliver a decent charge to an EV in roughly
30 minutes".

Decent is not full. It's enough to limp to the next charging point.

The former would put the power delivered at somewhere between 44 and 79
MJ, depending on where 'several' falls in the range 4-7 [1], the latter
at 13 MJ.

That's obviously quite a disparity - or rather, two disparities,
between your number and the Reg's, and the Reg's two numbers! I don't
know if someone's missed some zeroes, or if you've just seen some real
electron-guzzlers.

The orders of magnitude are very similar.

And having spent the last 30 struggling with a series of battery laptops
where the power characteristics were described by rabid optimists, I
have little faith that early (~ next 20 years) battery cars will be any
better.
--
Roland Perry

David A Stocks wrote:

events like a third of the nation's
households putting a kettle on the boil at the start of a TV
commercial break.

I've just thought of a solution to that problem - kettles should have a
standby mode in which they consume as much power as when they are boiling
water.

Tom Anderson wrote:
On Tue, 26 May 2009, Theo Markettos wrote:

Or something similar. Basically, at the point at which everyone switches
their kettles on, cars across the city stop charging for five minutes, and
resume once the tea is brewing.

It is, but it is not (quite) beyond the wit of man. I think you're
suggesting something along the lines of what i suggested above, but
cleverer.

Yes, that's the sort of thing I was getting at. It would have to be
carefully designed to avoid this kind of thing:

Night electricity cheap
Everyone's car is set to come on charge at 2am when electricity is cheap
Power surge, electricity expensive
Everyone's car switches off
Load dip, electricity cheap
Everyone's car switches on
etc, repeat as fast as the network can switch

At which point you've not only fried the car charging electronics, but
potentially fried the generating plant too. When there are millions of
demand-sensitive devices, the control system gets very complex. As you also
have to worry about keeping the network synchronised at 50Hz.

Not exactly a piece of cake to design, but it's not beyond the laws of
physics so it's possible.

Theo

"Theo Markettos" wrote in message
...
With a suitably non-trickle feed, the charging would be controlled so that
it takes place during the troughs in demand. You'd have to say something
like 'charge me by 7.30am' and the charger would know that if it hadn't
got
enough cheap (aka trough) power by 4am it would have to charge on
'expensive' power. But you still need the grid and generating plant to
supply that. The system is a very complex series of many feedback loops,
so
controlling it is quite tricky.

A similar mechanism already exists for off-peak domestic customers using
night storage heaters, who get a contract stating something like "you get 7
hours of cheap rate elctricity between the hours of 2300 and 0800 the
following morning", together with a radio controlled switch for that part of
the supply. The switches are used by the local suppliers to manipulate their
overall load in order to buy bulk electricity at the best market prices from
the generators.

It should be possible to come up with something similar for charging cars.
If you want a 100% charge in the shortest time possible during peak demand
you pay a premium for it. If you want a 25% top-up charge spread over a few
hours you get a cheaper rate. It should be possible to manage the overall
demand on the National Grid and local distribution networks in order to
avoid major upgrades - for a while.

D A Stocks

In message , at 01:09:37 on Thu, 28 May
2009, David A Stocks remarked:
A similar mechanism already exists for off-peak domestic customers
using night storage heaters, who get a contract stating something like
"you get 7 hours of cheap rate elctricity between the hours of 2300 and
0800 the following morning", together with a radio controlled switch
for that part of the supply. The switches are used by the local
suppliers to manipulate their overall load in order to buy bulk
electricity at the best market prices from the generators.

What they forget to mention quite as loudly is that you get charged
*more* for the daytime electricity, not just *less* for the night-time.
Unless at least a third of your consumption is overnight, you will end
up paying more overall.
--
Roland Perry

On May 28, 10:42*am, Roland Perry wrote:

In message , at 01:09:37 on Thu, 28 May
2009, David A Stocks remarked:

A similar mechanism already exists for off-peak domestic customers
using night storage heaters, who get a contract stating something like
"you get 7 hours of cheap rate electricity between the hours of 2300 and
0800 the following morning", together with a radio controlled switch
for that part of the supply. The switches are used by the local
suppliers to manipulate their overall load in order to buy bulk
electricity at the best market prices from the generators.

What they forget to mention quite as loudly is that you get charged
*more* for the daytime electricity, not just *less* for the night-time.
Unless at least a third of your consumption is overnight, you will end
up paying more overall.

Hence night storage heaters and hot water boilers with timers (a
principle that can extend to other appliances e.g. washing machines
and dishwashers).

Also, this uSwitch webpage suggests that it can make sense if one's
night-time energy consumption is "roughly 20%" as opposed to a third
as you suggested:
http://www.uswitch.com/gas-electricity/economy-7/

Still, you're quite right to say that it could well prove to be a
false economy.

Nonetheless the principle could be utilised for car charging, either
through on-street charge points or fed by the car owner's domestic
electricity supply - of course charging a car from one's domestic
supply entails being able to park the car more or less next to one's
home, and dealing with getting the cable across the pavement as well
(these problems don't apply with a driveway or garage of course).

Nearby-ish to where I live there's someone who has one of these G-Wiz
electric cars - they seem to be able to park it outside their house
most of the time (it's a quiet dead-end street) and the cable they use
across the pavement (which doesn't get a lot of traffic) is one of
those arrangements with a rubbery mat so it lies flat and appears to
largely mitigate the trip factor, but I'm not sure it'd be so workable
if the pavement was a somewhat more popular walking route.

In message
, at
04:32:18 on Thu, 28 May 2009, Mizter T remarked:
Hence night storage heaters and hot water boilers with timers (a
principle that can extend to other appliances e.g. washing machines
and dishwashers).

This is a classic example of market failure. Why should I run around
putting all those things on timers, with all the inconvenience of taking
2 days to wash clothes [wash at 2am one day, dry at 2am the next day],
just to return my bill to the level it used to be before!!

Also, this uSwitch webpage suggests that it can make sense if one's
night-time energy consumption is "roughly 20%" as opposed to a third
as you suggested:

1/3 is a sexier fraction than 1/5

http://www.uswitch.com/gas-electricity/economy-7/

Still, you're quite right to say that it could well prove to be a
false economy.

Although the rates could be adjusted.

Nonetheless the principle could be utilised for car charging, either
through on-street charge points or fed by the car owner's domestic
electricity supply

If the rates are calculated properly.

- of course charging a car from one's domestic
supply entails being able to park the car more or less next to one's
home, and dealing with getting the cable across the pavement as well
(these problems don't apply with a driveway or garage of course).

It'll make the fight for a parking space exactly outside your own house
much fiercer!

Nearby-ish to where I live there's someone who has one of these G-Wiz
electric cars - they seem to be able to park it outside their house
most of the time (it's a quiet dead-end street) and the cable they use
across the pavement (which doesn't get a lot of traffic) is one of
those arrangements with a rubbery mat so it lies flat and appears to
largely mitigate the trip factor, but I'm not sure it'd be so workable
if the pavement was a somewhat more popular walking route.

I wonder if there are any rules about that kind of thing. For example,
the car isn't directly earthed, so what if there's a fault somewhere?
--
Roland Perry