PG&E: How EVs could impact the grid

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>> You've probably heard things about the grid and the impacts of the grid. I just want to give you two scenarios, here, to talk about, and illustrate really what's going on here with respect to charging and the impacts. What I have here is a very simplified, you know, picture of the grid. To the left-hand side is the transmission system, where we've got sort of the large-scale renewables interconnected to the transmission system. In the middle is a substation. This is really the hub of our distribution network. It's got a feeder that goes out from there. And then we're showing two neighborhoods. One neighborhood has two homes connected to a distribution transformer out in the area. For those of you that aren't familiar, if you look out on poles, there's a device kind of looks like a garbage can up on the top of the pole. That's the distribution transformer. That's what I'm talking about there. And then on the other -- the other neighborhood has five customers connected to that same transformer. You know, relatively -- again, kind of a stylized view here. But this is kind of the existing grid, so -- first scenario I'm gonna talk about is we're gonna look at Berkeley, not just because we think it's useful looking at that area. We are anticipating that a fair number of these vehicles are gonna be in that city. Kinda looking at those two different neighborhoods. First electric vehicle shows up in one neighborhood, on that transformer that has five customers. Electric vehicle shows up in that second neighborhood, where we've got two customers per transformer. Kind of using the example that I -- kind of the data that I gave you, that one electric vehicle looks like two homes. So now we've got essentially the equivalent of seven homes that have been now connected to that one transformer, and we've got four homes that are connected to that other transformer. Now depending on the, you know, the loading that we have in that neighborhood and, you know, exactly the condition, the size of the transformer, and so on, the impacts may be relatively modest, you know. For example, we may be able to accommodate that electric vehicle down in the neighborhood that has two homes per transformer. Whereas we might have to do an upgrade for that neighborhood has -- that now has seven homes equivalent. But it's spread out, so -- it kind of -- the impact, if it's spread out, it's likely to be less. The next thing I want to talk about is more around this notion of clustering, so -- and, you know, human behavior being what it is. Right? So first person comes home in the cul-de-sac, they come home with an electric vehicle. I'm pretty sure everybody in that cul-de-sac will know that, will notice that, and if they were thinking about electric vehicle, now's the impetus, I'm gonna be keeping up with the Joneses here. I'm gonna go get my electric vehicle as well. So this next scenario is kinda around two electric vehicles that show up in this same neighborhood. So then one shows up, drives down, get their cool car. Everybody's noticing it. Drive down the cul-de-sac. Ah, neighbor gets one, too. So what's the impact from a grid perspective is we've now added the equivalent of four homes. We now have nine homes on this transformer. So the impact from a -- if you sort of go upstream of these neighborhoods, the impact on that feeder, the impact on the substation and the transmission system is actually quite modest. And it's kinda not really a big deal. However, for that transformer, that, you know, that local neighborhood, you've now added basically a little subdivision, you know, to that. So the impact is potentially significant. And again, when people talk about the impact on the grid, at least initially we're expecting it to be very localized, and this is kind of the illustration of that. So what happens? You know, we may see that this transformer overloads. The fuses blow or the circuit breaker may blow, and these five customers are now out of power. So, not a happy experience and one that we want to be sure that we avoid.

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