> 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.
Here’s some napkin math based on a few assumptions.
Assumptions:
The article is correct and it’s an 800KW battery pack for the semi. I’m also going to go with a conservative assumption and assume 2C charging rate for the battery pack. I’m also going to assume that the semi will have the ability to take in a 480V charging current because it simplifies wiring and is easier to get in an industrial capacity.
With those assumptions, you’ll need 1.6MW of power, something that can be easily delivered with less than eight 500MCM cables (roughly 1” copper cables including insulation that weigh about 2lb a foot and are still rather flexible). This seems in line with the charging port photos I’ve seen for the semi. Neither the cables or the power needs are that dramatic, there’s wind turbines that put out that much power individually along I-70 in Kansas for example where there is thousands of them.
In general it doesn't seem like an issue. Your local grid may or may not be able to directly load balance that much energy, but even if it can't, you judge add some storage batteries at your charging station to deal with the load balancing.
> To meet Tesla’s claim of 400 miles in 30 minutes for a semi carrying 80,000 pounds would require its new Megachargers to achieve output of more than 1200 kW
1200 kw is a lot of power. That's the average amount of power used by 600 homes, or half of the output of a large wind turbine here in the Midwest, to charge a single truck.
If they use a 440 V supply to charge it, that'd be over 2700 amps.
> A 100 Amp relay good for 10kW is < $2, yet the cheapest similar EV charging system is easily $1000.
The grid operates at 10kV. Most electric cars accept voltages less than one tenth of that. The cost is creating a large transformers.
That said, large transformers like these are pretty standard in sub-stations, it's still not clear to me why our existing infrastructure can't support super charging everywhere.
Note that EVs are considered "continuous loads" under the US electrical code, so the circuit actually needs to be sized for 125% of the load (ie to charge at 80 A requires 100 A service, not 80 A service).
> I've read the transformer problem is one that California utilities are already addressing, as in as few as one or two charging at night could blow out a neighborhood transformer.
Be very careful who you trust on these issues. A typical level 2 charger is 30 amps by 220 VDC. That's 6600 watts. That's the equivalent of four standard 120 VDC, 15 amp household circuits. If two people using level 2 chargers would blow out a neighborhood transformer, there are significant design flaws with the local infrastructure, and the utility company has set themselves up for failure.
I'm not saying the increase in the number of EVs charging at night won't cause any problems at all, but utilities are heavily regulated. They have to provide reasons for rate increases, and this looks like a honey pot for them. Expect them to shout about it at the top of their lungs.
And if they do want/have to stop, imagine charging at a rate of up to 3750 kW:
> The Megawatt Charging System (MCS) is a charging connector under development for large battery electric vehicles. The connector will be rated for charging at a maximum rate of 3.75 megawatts (3,000 amps at 1,250 volts direct current (DC)).
> At 900kWh, a system like that could charge from 10% (assumed minimum reserve) to 95% (Batteries are never really charged to 100%) in under 2 hours @ 400KW, which is about the power level of the beefiest EV chargers being developed right now.
There's no particular reason charging a big, multicell battery needs to bottleneck on a single charger. (is there?) It's done with cars for what I always assumed were cost and convenience reasons.
> Where do people expect the necessary charging power to come from?
For a given size of EV fleet and usage amount it doesn't matter if they charge quickly or slowly from your power plants point of view, higher power charging means there is correspondingly fewer cars charging concurrently since they finish quicker.
"...we find that as little as 11% of heavy duty vehicles in Texas charging simultaneously can lead to significant voltage violations on the transmission network that compromise grid reliability. Furthermore, we find that just a few dozen EVs charging simultaneously can lead to voltage violations at the distribution level..."
I don't think you have a good handle on how the distribution system is sized. Single, large loads like EVs at 10-30 kW were on nobody's radar even as recently as the 2010s. yes, infrastructure was designed for rising demand but not the sudden addition of 7 kW+ of capacity in multiple homes.
A typical EV charger draws anywhere from 7 kW to 25 kW. That is the total connected load of more than one typical North American house. And typical pole-mounted transformers are around 50 -200 kVA. Two EVs added to the regular mix is all it takes to upset the balance.
Or a pile of batteries.
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