10 250kw chargers are frequently only supplied by 1 megawatt of power supply.
They rely on the fact that it is common for some of the stalls to be empty, occupied by cars that have finished charging or can't charge at the full rate for whatever reason.
Some sites have batteries to provide a bit more power for the busiest times too. That has the benefit that those same batteries can participate in grid balancing the rest of the time (buying and selling power for profit, and getting paid for various technical grid services too).
You're right, I've done a bit more research into this. The company in question (Ubitricity) are uprating lampposts to 25A single phase at 240V, so 6 kW per post. Even though sodium (and earlier flourescent) lighting never used anything like that much current, I can't find a source to confirm whether or not the lampposts were originally rated at 25A or lower.
On your calculations of how many cars can charge at once, I would keep it simpler and say that a row of parallel parking typical in UK cities, there is one street lamp for every 5 cars. 50 kWh charge overnight, approx 300 km range for every fifth car.
Supposing 100% EV adoption - well, already not everyone drives themselves to work/kids to school in UK cities (where most on-street parking takes place) - but if they do, and have charging at work plus some nearby rapid charging, that should do the trick, assuming a typical commute by road isn't more than 50 km each way. It's certainly in the ballpark.
There's a decently high current power line available from street lights. Not sure if they're still putting them in with high current since so many are converting to LED, but sodium lights drew ~1kW iirc.
Set the filter to 3-22kW or so, and in Europe at least you will see a lot of on-street chargers. London especially.
In some places they are added to street lights, since those had a thick cable for the old sodium lights but don't need the power any more for LED lighting. In others, it's a new post between two parking spaces.
It’s almost always first come first serve, and they’re either Tesla wall chargers or Chargepoint or similar wall chargers, usually maxed out at 48 amps or so.
DC charging stations sometimes have batteries on site so that they can charge up from the grid and then deliver bursts of power from the batteries during charging. Apparently this is often worth it to avoid the high demand fees that utilities charge when you draw a lot of power at once.
I assume this will become more ubiquitous as charging speeds continue to increase.
(You're right that a megawatt is a high power draw in the context of normal household electricity usage, but keep in mind that if you can pump ten gallons of gas in a minute you're effectively drawing the equivalent of something like 20MW, so in the context of vehicle refueling it's not so crazy.)
It seems that charging points are rated in the range 25-50kWh (depending on whether they are 'fast' or not) so one fast public charging point will pull more when in use that a standard house.
So indeed if you install 100 of them in a tourist hotspot that means peaks of 5MWh, which again I suspect would take down the whole local electric subsystem and maybe the grid has not even enough capacity in the area.
Let's just say that I plan to keep my diesel car as long as economically possible...
I went to a supermarket in the UK recently that had an electric car charging area, with space for around 8 cars. Guess what the maximum charging power was?
> It also means that on the distribution grid, a charging station for 8 semis will need a dedicated 20 MVA 33/11 kV distribution transformer, plus 4 11kV/480V transformers.
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