Assuming it's for overnight charging, I would guess a large apartment complex that offers an EV charging hub might like to install some sort of load balancing/switching mechanism to limit how much total draw. It doesn't take the full evening to charge a car, so it would sequence where to deliver the power.
Most people don't drive that much in a day. For a typical EV user nightly charging isn't even really necessary, they're probably only needing to charge once every 3 days or so so it won't take that much to top-up if they're doing it nightly. If it's a small enough building tenants might be okay with doing a sort of sign-in system to use a smaller bank of chargers when needed. Sort of like reserving a treadmill at the gym.
It doesn’t need to be that smart. Just spreading the charging time across the full evening always would reduce load significantly without transformer level coordination or smart transformers. Kick off charging when grid capacity is lower than a certain threshold, and trickle into EVs based on how much charge is needed.
EVs already let you specify when you want to leave in morning, so it’s a small extension to that.
It's sort of a microcosm of the problem of upgrading the grid to handle the additional load from charging EVs. Like the grid, I think it will happen so gradually that it will barely be noticeable, and the upgrades will just be a part of regular electrical work.
Note that you'd only need to size for average use, not peak use. With a bit of cleverness (and expense) you could set a power limit for the whole garage and distribute it between the charging cars, rather than letting everyone charge full blast. Most people will drive under 50 miles per day on average and will charge overnight, so you really only need to deliver about 1.5kW per car. (50 miles at 300Wh/mile is 15kWh, assume "overnight" is ten hours of charging.) You'd want to be able to provide more for those who need it, but that's probably a reasonable number for an average.
I have 10kW charging at home for my Model S and it's major overkill for local driving. Most public chargers are about 6kW, which would still be plenty for daily charging.
"I imagine most people would put them on charge after coming back from work or at night."
That's true, and it would indeed present a significant problem as the early evening already represents a peak demand period on many grids.
However: plugging in doesn't necessarily mean the same thing as charging. Pretty much any EV already supports scheduled charging. It's useful to take advantage of cheap off-peak energy rates that start around 10 or 11pm (here in the UK, you can get overnight off-peak rates that are about 30% the cost of a typical all-day or peak rate).
The next step is to have the chargers (or the EVs themselves) interact with the grid so that they automatically slow or stop charging during peak periods, in exchange for some incentive from your utility company.
There are already trials of these smart chargers going on with in places with high EV uptake like California and the Netherlands.
Taking that concept further, V2G will mean that your car can not only stop charging during demand peaks but actually sell some energy back to the grid. If your car needed, say, to top up 20 kWh overnight, it could first sell 10 kWh to the grid, receiving a high peak-time feed-in credit, then "buy" 30kWh later in the evening when prices are much cheaper. The net result could mean that the overall cost of charging is much cheaper or even free!
Finally, as EV range gets bigger, the need to actually charge every night less frequent. Where I live, there are several EVs that are typically parked on the street (without access to a charger) and only seem to get charged every week or so. The owners probably only average 10 miles or so a day so daily charging isn't really needed.
We already have a lot of excess capacity at night. Slowly charging EVs could even be a net-boon for required peaker plants if people could cover their own needs for the 15% of the day
My energy provider already allows a separate EV charging meter that charges a reduced rate if you charge at night. I suspect they are not alone in this.
Most electric cars will charge at night, which is when power consumption is currently at its lowest. Power stations (and other parts of the power infrastructure) have to be sized to the daytime peak, plus a safety margin to cope with at least the loss of any single element. So until the extra consumption from cars charging overnight grows above the difference between the nighttime low and the daytime peak, not much extra infrastructure is needed.
On the other hand, there will be cars charging at daytime (either at fast chargers, or while the owner is at work); and there are some power stations that can only work during the day. I don't know which of these two factors is bigger.
Very true, and it's a well understood problem. For a variety of reasons it is better to charge during the day than overnight (not the least being that solar works better during the day, helping to mooting nightly storage concerns), and so an ideal situation here is that many or even most of those charged during the day at work.
There's a lot of possibilities here though. With smart meters and cars hooked up all night, the power company has a lot of freedom to not just 100% every car instantly, but throttle and prioritize as necessary.
If they are charging during low usage times, they are already doing that. In areas where that’s at night, EVs are in a good place grid-wise if they are charging at home.
This is one of the reasons I've argued in favor of "slow, at work charging" as the default for EVs. If you put in a bunch of 240V/16A chargers (3.8kW), as people show up in the 8-9 timeframe, they start charging, and the bulk of the charging happens in the ~10AM-2PM window that's after the morning peak, as solar is ramping up, and before the afternoon cooling/evening peak. You can even restrict the chargers a bit more in the morning if needed until off peak, though I'm not sure this is worth much over just using dumb chargers that are cheap to install. An average 35 miles a day driving (in the US) requires ~10kWh, so you've got a few hours of charging that can swallow an awful lot of power during the time nothing else is using much of it.
It's far better than having to deal with evening and overnight charging.
Your model is simplistic. No sane electrical engineer would build a system where EVs charge on a uniform schedule evenly distributed across all 24 hours.
Rather, you can build a system where EV chargers are basically the inverse of natural gas peaker power plants. They turn on when grid supply is high relative to demand (and hence get off-peak rates), and then turn off when grid demand is high. Most peoples' EVs would charge while they're plugged in at work; the few stragglers would charge late at night when everyone's lights are off. Unless you are about to make a cross-country trip overnight, there is no reason to charge an EV during peak hours between 5-9 PM.
That's what GP is alluding to when they say EVs are storage.
You could feed power into the grid to offset your charging usage at night. (Perhaps even come out ahead of where you would be charging during the day, if your power utility has lower pricing off-peak.) Alternatively you could add a home battery.
I would think that EVs would largely be a net load on the grid at night since that is when they would normally be charged. It could possibly be a revenue source for those with non-standard usage patterns of course.
As an interim solution, the property owner might be able to install large batteries (for example Powerwall) that renters could use to charge their vehicles. The batteries could be charged continuously, without overloading the old electrical service
Probably this wouldn't be enough if every renter was a heavy EV user, but it could be good for a few years, and also would be useful for power outages and to take advantage of off-peak rates in future
Metering and payment would be an issue, but it should be possible to find a solution for that
And the charging is primarily done during the night, where the grid (typically) is less strained. The biggest issue is that it currently doesn't align very well with things like solar.
In my buildings parking garage there are 150 cars, where probably a good 30-40% of cars are BEVs. We're pulling a maximum of 32kW, or 400V/80A. I have yet to find my car not fully charged in the morning. It's a load balanced system, so usually I get full effect of 11kW when charging.
Likely when built the streetlights weren't LED, so the buried cables are under-capacity. Assuming they can provide 230v power at 15-20 amps, that's enough to fully charge something like a Tesla or Chevy bolt (250-300 mile range) overnight.
Most people could do fine with charging only 1 out of every 4 nights for regular commuting, the tricky part is just figuring out how to make that work logistically, but it is at least feasible. Those with schedules that allow charging during the day make things easier I'd assume.
I heard mention of charging the cars at night from the unused base load, possibly meeting the demand during the day by taking some charge from parked cars.
Even in that world, you'd still want a way to manage the load through the night so that you don't have all the chargers clicking on at 11pm and then when the cars are full have a few hours later, demand craters until morning.
With renewables the incentives for load management become even higher (per this article). The real next step after second-by-second billing would be setting up chargers with backfeeding capabilities/policies, so that you have an arrangement with your employer to charge your car at work on cheap daytime solar power, sell it back into the grid during the evening rush, then charge up again on overnight base load. Most EV batteries are way overspecced for what people need in daily use, so as long as you have a special "charge me to full and stay there" mode you can switch into, there'd be no reason (other than a bit of wear and tear) not to cycle your battery like this.
Okay, so we ask people not to charge their EVs during the day and now we won't want them to charge them at night? I know EV penetration isn't high but many utilities have good rates at night!
The best way to fix demand is to get all usage to be as efficient as possible, not restrict its use
Most people don't drive that much in a day. For a typical EV user nightly charging isn't even really necessary, they're probably only needing to charge once every 3 days or so so it won't take that much to top-up if they're doing it nightly. If it's a small enough building tenants might be okay with doing a sort of sign-in system to use a smaller bank of chargers when needed. Sort of like reserving a treadmill at the gym.
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