EV charging and hydro generation/distribution challenges

[tomh009]

I do wonder how large an EV population could realistically be charged overnight (considering that few cars will have completely empty batteries each night) given our current spare overnight generation capacity.

In theory, overnight charging is a no brainer, and basically amounts to free capacity, I don't think transmission capacity is a concern here. Local distribution capacity might be more of a problem, but fairly easy to solve.

However, the projection is that the electrical grid will become less and less clean in the next few years as there is a shift to more natural gas away from some nuclear. I think EVs efficiency should be based on the average energy emissions, rather than emissions at the time of charging...I suspect getting that detailed is probably irrelevant and at that level of detail, is going to be missing other side-effects like infrastructure investments to support charging anyway.

Interesting and unrelated tidbit. The small town I am in right now has a DC fast charger in their municipal parking lot. It makes a lot of sense because this is a destination that is at the extreme range of EVs from much of the GTA, so to support round trips a fast charger would be necessary. But it is the least efficient of EV charging, albeit also most rare.

There is some available overnight capacity indeed (though much less so in the daytime, and especially so in the summer), and it is pretty much "free". This is snipped from https://www.ospe.on.ca/public/documents/...r-2017.pdf.

   

It might be a gigawatt, or it might be five, depending on the time of year, time of day and the weather. But suppose we have 5 GW of available capacity, and 5M EVs. That's only 1000W (1 kW) per vehicle available for charging. Assume 10 hours of charging time, and 20% of cars need to be charged, and maybe the numbers work (it would provide 50 kWh per car). But it would only work when there is 5 kW of capacity available. If there is less than that, the gas generation has to kick in, or else the power available for charging will need to be curtailed (how?).

At the local level, the biggest bottlenecks will be the transformers and distribution stations, which were not designed with this level of usage in mind. Most multi-residential buildings have little spare capacity, and I suspect the neighbourhood substations may have the same challenge.