Electric cars

redux

redux wrote: »

It's a good thing that smart meters are coming soon for houses.

The faster that fast charge gets for Tesla owners on the motorway, the greater proportion of a neighbouring town that will have to have all of the fridges turned off.

almillar wrote: »

Can't tell whether this is a joke or not, but just in case anyone believes it - it's rubbish.

Is it?

There are people talking about 210kW Tesla chargers either already or coming soon. I've seen 12 Tesla chargers at one motorway station, with 8 of them in use.

So it is foreseeable that 2 MW of charging could happen at a busy site. Or more.

That might be about the same as 10,000 houses.

We are told that when all premises have smart meters, this could be used to regulate load in busy times by turning off some devices.

That sets up dilemmas about electric cars. Charging gently overnight at home is one thing, but widespread demand for fast charge of cars during peak times is going to cause problems in prioritising load. Some factories use more power than homes, but factories won't want to be switched off.

There are already some rumblings of discontent and potential conflicts of interest. A while ago I saw Tesla owners on their forum whingeing about removal of some of their dedicated charging sites, with speculation that generic charging might be replacing those, and some rather snobby comments about inferior quality electric cars. They sounded rather more focused on their own interest than interested in the common good, either for the world at large or for all electric car users as a group.

IamNotAllowedToUseMyName

NigeWick wrote: »

Nope:- Transportation disruption will dramatically redraw the urban landscape. What will your city become? https://buff.ly/2DI6DjZ

10 times cheaper per mile is nuclear power thinking, a lot of motoring costs is taxation and will be carried over in some way. They are also wildly optimistic about the uptake of autonomous cars and how that will affect insurance. They seem to think that it will take 10 years to drain the self-driven cars off the road from a point of them being available. Wildly optimistic. You can tell this by the presumption that a car will be used 5 times more than at present so reduce the cars to one fifth of those required.

Have you thought about what those numbers imply?

I've seen that sort of report back in my steel works days. KPMG and the like come in and say that as you have capacity for 90 tonnes a day and you have an order book for 60 tonnes a day you can close 1 of your 3 mills. What happens - too many change overs and you can't meet your order book - actual capacity 50 tonnes a day. The report has simply assumed that if an individual drives 4 hours each day then a car can be used about 20 hours a day to be efficient. Unfortunately the reason we have traffic jams is that everyone drives their cars at about the same time. Unless you have a drastic change in car usage, car sharing being the norm, then that is extremely unlikely. Even with painful commutes, we have not seen a change in working practices to compensate for the wasted hour or two a day battling rush hour for many drivers.

For example, they have glossed over the issue of rush hour - note that they assume that there is capacity for the car to be there "on demand" which if nothing else changes you can assume means people still will travel at rush hour and now there will be parents ordering cars up for their kids so at school time I would expect even more journeys as mum and dad go to work and kids go to 3 different schools.

If that report is what is informing your thinking, then I think you need to think more critically about your sources.

almillar

Can most available EV's be plugged into the domestic mains, for charging? Without additional expensive leads?

Yes, but as AdrianC says, it's mostly a waste of time. So much so that a lot of manufacturers don't include a 3 - pin domestic lead - Renault for example. They will sell you one, but it'll cost you £400 odd! They really don't want you to do it, and paid for my charger installation.

Your domestic socket can do 13 amps, but anything that would take that for a long time could heat up poor cabling, so usually you're talking about 10 amps - 10a x 240v is 2.4kw. That's a theoretical 10 hours to fill a 24kWh Nissan Leaf.

At a 7kW charger, which is about the best you can do in your home (32a x 240v, on its own fuse), with single phase AC, that Leaf, if it had the 6kW on board charger, would take, theoretically, 4 hours instead.

In my examples above, you could probably buy and install the charger, cheaper than Renault would sell the cable for!

Is it?

YES!

So it is foreseeable that 2 MW of charging could happen at a busy site. Or more

Running on the assumption that those 12 chargers were just dumped there without any thought for supply or management.

There's a very easy solution, of course, to all this mega demand when lots of cars plug in - batteries, at the sites. The problems are localised, you can't just crank up a nuclear power plant in the middle of the day when a lot of people plug their cars in, but, say, 12 old Tesla batteries at the site you talk about (filled off peak, to be used on peak) would even out the demand nicely. No fridges are harmed. BTW, all these smart things get turned down, nothing gets turned off.

David_Aston

Thank you Adrian and almillar.
Can I ask, does this Renault supplied charger plug into your mains?
Also, plugging in after getting back from work, ten hour charge ready for work in the morning. Am I missing a major snag here?

AdrianC

Nothing that just "plugs in" will give you more than 13A, and pulling more than 10A for an extended period is not a good idea. Anything more than that needs to be wired to your consumer unit ("fusebox") on a dedicated circuit.

Electrickery is basic maths, for the most part.
volts x amps = watts
watts x time = watt-hours

redux

almillar wrote: »

Running on the assumption that those 12 chargers were just dumped there without any thought for supply or management.

There's a very easy solution, of course, to all this mega demand when lots of cars plug in - batteries, at the sites. The problems are localised, you can't just crank up a nuclear power plant in the middle of the day when a lot of people plug their cars in, but, say, 12 old Tesla batteries at the site you talk about (filled off peak, to be used on peak) would even out the demand nicely. No fridges are harmed. BTW, all these smart things get turned down, nothing gets turned off.

You're completely inverting this.

I said 12 Tesla chargers in a motorway service area, and 8 in use when I looked

I didnt mention it, but this was mid-afternoon.

Those Tesla owners want to drive their cars along the motorway during the day, and fast recharge them during the day.

They aren't generously leaving them there as an extra resource, as per your suggestion. Judging by their slagging off of other electric car owners who might benefit from certain sites removing their Tesla chargers (why did the contracts end, by the way?) if the speculated replacements are generic, they aren't inclined to much altruism anyway.

I stick with what I said. 2 or 5 MW for cars passing the town on the motorway is about the same consumption as tens of thousands of homes.

Are any of those Tesla owners going home a bit late going to stop and plug in somewhere to help other people cook their evening dinner, and run themselves out of range? I don't think so.

AdrianC

2-5MW for 10k+ homes? That doesn't sound right...

At 230v, 5MW is 21,000A. That's about a decent electric shower or oven each in a tenth of that number of homes.

redux

AdrianC wrote: »

2-5MW for 10k+ homes? That doesn't sound right...

At 230v, 5MW is 21,000A. That's about a decent electric shower or oven each in a tenth of that number of homes.

Those devices aren't on in all houses at once.

If nobody is at home, the fridge might be on or off, using 60W or nothing. WiFi router, central heating control box, cordless extension phone, etc, a few watts each.

Obviously electrically heated houses use more, but some gas heated houses can probably get by on 3 or 4 kWh per day, average 125-167 watts

Gloomendoom

redux wrote: »

Those devices aren't on in all houses at once.

Some houses can probably get by on 3 or 4 kWh per day, average 125-167 watts

Apparently, much of the current local distribution network was typically sized at 1.5 Kwh per house, per day, plus a small contingency.

AdrianC

Sure, but it's a safe bet that a lot more than 10% of those houses will have their ovens on at 6.30pm. Or kettles at 8am. Or, or, or.