Where and When You Should Charge Your Electric Car – Video


Speaker 1: If you’ve bought a new EV lately or been shopping for one, you know, the mantra you get from car makers, they always paint this perfect picture of you having level two charging installed at your home and you plug in every night, overnight, fully charged, come out the next morning, you’re ready to go. And it’s bliss of perfectly clean, worry, free electric driving. But what if that’s not [00:00:30] the best model joining me now is the lead researcher on a paper that recently came out from Stanford university. That takes a very different look at how charging should be done for the benefit of the grid and for how we benefit the environment with this clean form of transportation. Chevon Powell is the lead researcher. Chevon tell me why you started to look at charging habits in the first place before we look at what you and your team recommend, because

Speaker 2: It’s a big issue. Um, at Stanford, we work closely with a lot of utilities from [00:01:00] around the country and they highlighted to us a few years ago. This is one of their big concerns. What will charging do to their networks? First, we had to come up with a model to understand what charging will look like behaviors we see in charging data, trying to understand and trying to build models and estimate to help planners prepare for 20, 30, 20, 35 in the grid,

Speaker 1: As, as I’m sure you know, it was not, I don’t know, a few weeks ago from when we’re taping right now that the governor of California, uh, announced that California’s gonna end the sale [00:01:30] of new combustion cars by 2035. And within a few days we had one of these wicked heat waves and at many charging locations. In fact, I’ve got a photo of one. You started to see temporary science plastered up by the charging companies saying, please do not charge between four and 9:00 PM. And so it was very stark to all of us that wait a minute, we’re not necessarily ready to charge the number of electric cars we have now, which is very few let alone the future. How, how concerned are you? [00:02:00] That

Speaker 2: Was really interesting. The timing of the announcement about EVs and then this crisis for the grid. Um, but I think it also sort of highlighted one of the upsides of EV charging because it’s very flexible compared to a lot of other demand. So in our charging data, in our modeling, we see most people don’t charge every day. People charge every few days on average. And so being able to shift and sort of wait until the next day, or just shift out of that really crucial time for the grid, that’s [00:02:30] a really great option and great resource and great type of flexibility. The grid is changing. We’ll be taking advantage of that flexibility, I think, to help deal with events like that.

Speaker 1: That that’s an interesting point. Uh, you don’t have a lot of flexibility around air conditioning when it’s hot, you need to turn it on, right? Yeah. When you need to cook dinner, you need to cook dinner and those are time based things or condition based things, but yeah, you be charging us flexibility. So let’s get down to exactly what you are recommending. That is so different than what I described earlier, which is the constant overnight plugin [00:03:00] at home formula. What do you think in a nutshell is a better way for us to view how we’ll charge our cars in the, at scale future,

Speaker 2: The study looked at several scenarios of charging infrastructure in some of them, a lot of home charging, like you said, and also some with a lot of daytime charging, so less dependence on home, charging more, maybe charging while at work or charging in public. Um, and in our results, that was much better for the grid at the generation level, in every different [00:03:30] metric that we consider the recommendations, definitely not to limit home charging infrastructure, all charging infrastructure is important because it really helps people adopt and make it convenient to have an EV. But as we build out this network and install millions more chargers in the next 10 years, if there could be a focus on public daytime charging infrastructure, I think that would serve a lot more drivers. Um, and it would be better for the grid.

Speaker 1: What is it about public [00:04:00] and daytime versus residential and overnight that is better for the grid? How does that help the grid?

Speaker 2: One of them is about renewable generations. So in the Western us, we have a lot of solar and that happens in the middle of the day and happens to align really well with workplace charging. And the other reason is about demand from things other than EVs. So other sources, other things that use electricity, the peak in that demand happens in the evening. So home charging aligns with that peak [00:04:30] where the grid is already stressed and it doesn’t align with renewable generation, which is gonna be coming online more and more as we get to 2035 charging at work charging in public during the day, sort of solves both of those problems. It doesn’t align with this crunch time and other electricity uses other electricity demand and it aligns better with the renewables that will be coming online. Um, we looked at results about emissions. We found that daytime charging led to lower operating emissions that’s [00:05:00] grams of CO2 per mile, charged from the grid, um, less ramping, uh, lower increases in peak net demand, uh, better use of renewable generation. All these different metrics, uh, were better for these scenarios with daytime charging.

Speaker 1: Does the world of workplace charging need to install battery storage for that to work? Or is it because it’s daytime that they don’t

Speaker 2: Because it’s daytime that they don’t. So all of the scenarios we [00:05:30] considered are possible in some, you might need to build more generation or in, in many cases, more storage to shift generations. So if you imagine we add a lot of solar and everyone charges at night, you need some really big batteries to shift that generation and store it and deliver it to the vehicles at night in the scenarios where people just charge during the day. And it already aligns you, you skip that step. We need less storage for the grid to make everything line

Speaker 1: Up [00:06:00] by getting the power live. If you will, <laugh> from one that’s being generated. You, you take out some, some losses that are there when you put energy in a battery and get it back out. So that must also add some efficiency.

Speaker 2: We have these big targets of how much grid storage we need to install by 2030 or 2035, that is there to help solve a lot of problems. EVs. Aren’t the only new source of demand coming on the grid. So if EVs can help by shifting their demand and needing less [00:06:30] of that storage, maybe we’ll still build the same amount, but we’ll be able to use it to support electrification of other uses or provide other good services.

Speaker 1: I know you’re not a workplace researcher, but fewer people are going to the office now. Um, do you have any conjecture in your mind about how effective daytime workplace charging will be with that in mind? Or is there another location we also need to add into daytime? We, you know, we all think of shopping malls, but I’m not sure how important you think that might be

Speaker 2: In terms of the effect of, [00:07:00] you know, the pandemic and working from home. We used data from before. And so that’s not something we looked at in this study. I think it would be really interesting, um, really for the grid, what matters is the time of charging. So if we find in the future, a lot of people working from home, maybe home chargers are still a good option, but then people should be encouraged through pricing to use them during the day and not to use them overnight.

Speaker 1: There was something I thought was interesting in your paper here that kind of [00:07:30] broke it down. Um, you talk about, we compare two powerful tools that reshaped charging, which is adding charging controls and changing the landscape of charging infrastructure by decreasing or increasing the availability of different options. So with that last part, what would you turn the dial up on in terms of locations? I think we heard some of that already. What might you turn the dial down on? I’m not hearing you wanna taper any charge type yet. Is there any charge type in the future you’d like to see less of because [00:08:00] you think it’s just less efficient for the grid or the environmental outputs,

Speaker 2: Difficult to say what you would turn down because all of this infrastructure hasn’t been built yet. So there are decisions being made today about investments of, you know, where are we gonna install all of these charges? So I think the result from my study is that we should focus those on public workplace, daytime level, two charging stations. Um, but say, you know, someone who has a home charger right now, we’re not saying you should, [00:08:30] you know, stop using it or stop driving your EV like it’s still very important to have access to charging. It really makes it possible for people to drive an EV um, that these future chargers, if they were more concentrated in public workplace, wherever people are during the day, that would be the best case.

Speaker 1: The other phrase in that paragraph, adding charging controls, what does that refer to?

Speaker 2: We looked at a couple types of charging control. Charging control is the idea that once you arrive, stay [00:09:00] at home and plug in your car at 7:00 PM, it’s gonna sit there, plugged in for maybe 12 hours. You only need to charge for a couple of hours, so you can shift and control when that charging happens within that time window. Um, and so in, at home charging, most commonly, uh, utilities will provide a time of use rate. So you have a time maybe 11:00 PM or midnight or 9:00 PM after which it’s really cheap to charge. And so [00:09:30] people will set timers on their car to delay the start time until that period to save money. That’s one type of control we looked at, um, the other is at workplaces. So this is a type of control being implemented, uh, in California today, uh, places around Stanford campus at different workplaces, um, where say you arrive at work, you plug in at maybe 9:00 AM. Maybe you leave around five. This is a typical example, but you only need a couple hours really to fill up your car. [00:10:00] And so shifting when that happens during the day, doesn’t affect you as the driver, but it can have a really big impact on the grid.

Speaker 1: And the one thing that no charging control can fix yet is people who plug in when they get there at nine only need two hours of charge, but their car sits there, physically connected all day, tying up that charge location. I know that’s not what your research looked at, but that someone needs to come solve for that. Right? Some kind of an automated system that unplugs and re plugs cars while they’re sitting there getting their little slice, because your, [00:10:30] your research underlines, the fact that a lot of connectedness to a charge location can be wasted, uh, potential as a car. You know, another car can’t get in there to get its efficient two hours. You know, a lot of people don’t like EVs, you know, a lot of EV haters out there say, oh, these cars aren’t that clean. They just shove the emissions upstream somewhere else. You were looking at a slice of Western states where that is not the case, is it,

Speaker 2: We only quantified operational [00:11:00] emissions. So not sort of the emissions behind producing a vehicle, but in terms of operational emissions, we did find it was much lower per mile than a comparable sedan using internal combustion. So it is true that the emissions, they’re not at the tailpipe, they’re at, you know, a power plant somewhere, but given the mix of electricity generation in 2035 in the Western us, it’s much lower per mile than just com doing the combustion in your vehicle. The [00:11:30] focus of our study was on the different scenarios. So, you know, the home charging scenarios, the daytime charging scenarios, and we found daytime charging led to lower emissions per mile. But in all of cases, it was lower than the comparable per mile for a combustion sort of traditional car.

Speaker 1: So, uh, let’s finish up with, uh, what you’d like to the memo you’d like to send to two or three different constituencies here. First of all, uh, car makers, did they have to do anything to, uh, to move forward [00:12:00] on your team’s vision or recommendation, or is this more about site operators?

Speaker 2: We mostly looked at charging access. So I think car companies could participate maybe by improving interoperability so that, you know, once you have an EV you could charge it anywhere, not in some networks, but not others. Really what we looked at was charging access and how important it is to be able to charge in different places in public. Um, and so whatever role they could play in improving [00:12:30] that would be really helpful,

Speaker 1: Uh, utilities and developers. Then it sounds like is where you see the nexus of the best planning. There’s

Speaker 2: Also a role for policy. So different counties in California, for example, have subsidies. When you install a new charging station and those amounts vary, you get a certain amount for putting in a home charger, you get a certain amount for putting in a public charger. Those are incentives. I think help people like office owners or, you [00:13:00] know, office park developers make decisions about how many chargers to put in. And so if it were easier to do the installation process, if it were less expensive to install chargers, those are policy related decisions that could make it easier for them. You know, the office manager to say, I’m gonna put in lots of workplace charging here

Speaker 1: With all the time you and your team spent looking at this and all that you know about what’s going on with electric cars. Um, are you optimistic that this revolution is gonna work?

Speaker 2: [00:13:30] Yes. I’m optimistic. I’m optimistic. It has to work. <laugh>

Speaker 1: I’ve been talking to Chevon Powell, she’s the lead author of an interesting new study coming outta Stanford. That adds a lot of nuance to what we thought was the perfect way to charge electric.

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