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Power Transportation

When's the Best Time To Charge Your EV? Not at Night, Stanford Study Finds (stanford.edu) 190

Posted by BeauHD from the best-for-the-grid dept.
The vast majority of electric vehicle owners charge their cars at home in the evening or overnight. We're doing it wrong, according to a new Stanford study. From the report: In March, the research team published a paper on a model they created for charging demand that can be applied to an array of populations and other factors. In the new study, published Sept. 22 in Nature Energy, they applied their model to the whole of the Western United States and examined the stress the region's electric grid will come under by 2035 from growing EV ownership. In a little over a decade, they found, rapid EV growth alone could increase peak electricity demand by up to 25%, assuming a continued dominance of residential, nighttime charging. To limit the high costs of all that new capacity for generating and storing electricity, the researchers say, drivers should move to daytime charging at work or public charging stations, which would also reduce greenhouse gas emissions. This finding has policy and investment implications for the region and its utilities, especially since California moved in late August to ban sales of gasoline-powered cars and light trucks starting in 2035. [...]

Current time-of-use rates encourage consumers to switch electricity use to nighttime whenever possible, like running the dishwasher and charging EVs. This rate structure reflects the time before significant solar and wind power supplies when demand threatened to exceed supply during the day, especially late afternoons in the summer. Today, California has excess electricity during late mornings and early afternoons, thanks mainly to its solar capacity. If most EVs were to charge during these times, then the cheap power would be used instead of wasted. Alternatively, if most EVs continue to charge at night, then the state will need to build more generators -- likely powered by natural gas -- or expensive energy storage on a large scale. Electricity going first to a huge battery and then to an EV battery loses power from the extra stop. At the local level, if a third of homes in a neighborhood have EVs and most of the owners continue to set charging to start at 11 p.m. or whenever electricity rates drop, the local grid could become unstable.

Another issue with electricity pricing design is charging commercial and industrial customers big fees based on their peak electricity use. This can disincentivize employers from installing chargers, especially once half or more of their employees have EVs. The research team compared several scenarios of charging infrastructure availability, along with several different residential time-of-use rates and commercial demand charges. Some rate changes made the situation at the grid level worse, while others improved it. Nevertheless, a scenario of having charging infrastructure that encourages more daytime charging and less home charging provided the biggest benefits, the study found. "The findings from this paper have two profound implications: the first is that the price signals are not aligned with what would be best for the grid -- and for ratepayers. The second is that it calls for considering investments in a charging infrastructure for where people work," said Ines Azevedo, one of the co-senior authors of the study.

"We need to move quickly toward decarbonizing the transportation sector, which accounts for the bulk of emissions in California," Azevedo continued. "This work provides insight on how to get there. Let's ensure that we pursue policies and investment strategies that allow us to do so in a way that is sustainable."
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When's the Best Time To Charge Your EV? Not at Night, Stanford Study Finds More

When's the Best Time To Charge Your EV? Not at Night, Stanford Study Finds

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  • Best Time? (Score:5, Informative)

    by Thelasko ( 1196535 ) on Sunday September 25, 2022 @03:30PM (#62912973) Journal
    When the line frequency is above 60 Hz. Your power company will thank you.

    • This is great news!!! I'll just go home from work to change my EV in the morning. Oh wait...

      I mean, I guess this means we'll need MANY MANY more office chargers. But will employers pay to install them and make them cheap enough to use? LOL.... not in California.

    • When line frequency is above 60Hz something is seriously wrong since it shall be 50Hz where I live.

  • They should subscribe to the service of a charging station, which will provide the electricity along with a service charge (profit)? Rather than say, own some storage, and transfer the electricity into the vehicle at night?

    And this will be good for the environment, the grid, etc? Small but necessary side effect, the old oil companies can pivot into be charging service providers?

    They could pay off the cost of the outlay for that and come out with an asset, rather than line others pockets. Sounds about as g

    • Having tons of battery banks everywhere is terrible for the environment though.... You did know those batteries only have a limited life cycle, right? LOL...

  • Smart (Score:3, Insightful)

    by Joce640k ( 829181 ) on Sunday September 25, 2022 @03:37PM (#62912993) Homepage

    If only cars could connect to some sort of server and query the optimal time all by themselves.

    It's a really tough problem, I know, but they'll have plenty of computing power to spare when they're parked and not trying to drive themselves.

    • Re: (Score:2, Insightful)

      by grasshoppa ( 657393 )

      This doesn't really take into account people actually DRIVING said cars.

      What about those who need to drive during "off peak" hours? What about those who drive more than 200 miles a day?

      EV advocates kinda wave those concerns away, probably because it doesn't impact them, but it does impact others and should be accounted for.

      • Re: (Score:2, Interesting)

        by Anonymous Coward

        This doesn't really take into account people actually DRIVING said cars.

        Why wouldn't it? My headphones have worked out the times I typically use them and will sit in their charging case at about 80% until bringing themselves to 100% just before that time. They do this to extend battery life but the logic could easily be adapted to work for power consumption.

      • Re:Smart (Score:5, Insightful)

        by Immerman ( 2627577 ) on Sunday September 25, 2022 @05:32PM (#62913303)

        What about them? Such drivers make up a tiny fraction of the total, which means
        - there's no profit in catering to them, and trying to do so will tend to drive up the cost for everyone else
        - if they need a different charging schedule, there's so few of them that it will have a negligible impact on aggregate grid demand
        - if EVs just aren't able to satisfy their needs, they can stick with ICE or hybrid vehicles and their emissions will be a rounding error compared to the emissions avoided by everyone else.

        Basically - if you're a weird niche-case user, you don't matter to the big picture. So sit down, swallow your ego, and let people work on solving most of the problem.

        Once most people are driving EVs, and we've got all the big problems solved... if your issues haven't already been solved as a side effect of advancing technology, *then* we can worry about them. Worst case scenario you're the Luddite buying a second-hand ICE a decade after they've banned them in new vehicles - but you've probably retired by then, and your kids will have built their life around the new reality.

        Life has never come with any guarantee that you'll be able to continue doing things the same way forever.

        • That's like the saying, "freeways are built to deal with rush hour traffic."

          It's not a bad thing. If traffic were spread out evenly throughout the day and week, then driving any time would be as miserable as driving during rush hour.

          • Re: (Score:2)

            by AmiMoJo ( 196126 )

            The reason driving during rush hour is miserable is that the amount of traffic is an order of magnitude or more than the average. If you spread it out, it would not be just as bad all the time even if your freeway was smaller. Your freeway won't go from 10 lanes to 1 lane, it will go from 4 lanes to 2 or 3 lanes.

    • Re: (Score:2)

      by Burz ( 138833 )

      Do a search on "smart grid charging" and also "vehicle to grid" or V2G. The latter is more of a future thing.

      • and also "vehicle to grid" or V2G.

        I keep hearing this concept of using vehicles as a storage system to pump back into the electrical grid, but it's not going to happen. Battery capacity is shortened with each charge/discharge cycle, and nobody is going to want to use their expensive to replace EV battery in this way.

        • "nobody is going to want to use their expensive to replace EV battery in this way."

          Surely that would depend on the rates offered?

          If time-of-use rates were updated accurately reflect energy costs, it might become advantageous to do this (and fund battery replacements from grid credits).

          Alternatively, in countries where feed-in tariffs are much lower than consumption tariffs, use the V2G to power the house and lower the electricity bill, reducing demand on the grid.

    • The part you're missing is that most of the time they're parked, is at night.

      The article is specifically trying to address the current practice of overnight charging with peak availability of renewable energy. The "optimal time," according to the study, is when renewable power is the most abundant because it's use-it-or-lose-it, and charging at night when renewable energy isn't as available means fuel burning plants need to step in to cover that load.

      But the problem is that people are much more likely to be

      • Sounds like government needs to pummel businesses into the ground with hyper punitive environmental impact fees for forcing employees to unnecessarily commute to offices. 10k per employee per month should cut it. Lets see how long office culture lasts then.

      • Re: (Score:2)

        by AmiMoJo ( 196126 )

        This is a solved problem. You can get a charger that talks to your energy company and only kicks in when the price is low, or when the car's battery level is low enough that it's worth paying extra.

        You plug it in when the car is parked, and it waits until energy is cheap to start charging. If one day there isn't much renewable power, it sees that the car has 200 miles of range left and it's a Wednesday so no need to pay extra as you are only driving to work. Maybe on a Friday it looks at the forecast price

    • Are you crazy? The only justifiable reason for cars to be connected to a network is collecting telemetry. Anything else would be a security issue!

    • The summary says:

      "Current time-of-use rates encourage consumers to switch electricity use to nighttime whenever possible, like running the dishwasher and charging EVs. This rate structure reflects the time before significant solar and wind power supplies when demand threatened to exceed supply during the day, especially late afternoons in the summer. Today, California has excess electricity during late mornings and early afternoons, thanks mainly to its solar capacity."

      This is non-sensical.

      The whole point o

  • They say that instead of charging at home people should charge at work.

    That sounds great but then suddenly you have to have many orders of magnitude more chargers than exist today, and most of them have to be rapid chargers if you want cars to fill up fully in a day.

    How much does that cost to put in so many chargers? How much material us used, how much CO2 is produced in creating all these chargers, when people could otherwise just power from line power at home?

    It really does not feel like the full ecosyst

    • Re:Is ti realistic that everyone would charge at w (Score:5, Informative)

      by dhartshorn ( 456906 ) on Sunday September 25, 2022 @03:55PM (#62913051)

      "many orders of magnitude more chargers than exist today"

      And many orders of magnitude more EVs to go with them. But fewer chargers than you think. See below.

      "most of them have to be rapid chargers if you want cars to fill up fully in a day."

      Nope. Average need is around 10kWh daily. If you charge twice a week at work, for instance, you'll need 20kWh, or about 3 hours on a 7.2kW charger. If you're an 8 hour worker with an hour lunch, you're present over a 9 hour span, which means 3 cars can charge per charger, 6 cars per two day cycle. Most people can home charge with a L1 charger for weekends.

      Your numbers may vary, but not by much.

    • They say that instead of charging at home people should charge at work. That sounds great but then suddenly you have to have many orders of magnitude more chargers than exist today,

      The study was about the year 2035, and was about a time when the number of electric cars was orders of magnitude more than exist today.

      So, yes, it's reasonable that if the number of electric cars is orders of magnitude more than exist today, the number of electric car chargers would be orders of magnitude more than exist today.

    • > most of them have to be rapid chargers if you want cars to fill up fully in a day.
      No. You car is typically parked at work for ~8 hours a day - you can use the same slow charging commonly used overnight. Rapid chargers are the least-desirable option for everyone, unless you're trying to charge during a road trip rest stop.

      And you're talking exactly the same number of slow chargers whether everyone is charging at home or at work. And doing it at work means they can build relatively dense charging infr

    • and most of them have to be rapid chargers if you want cars to fill up fully in a day.

      No. I level 2 charge (and sometimes level 1 charge, cause it's free) at work, and I drive 50-70 miles a day. I've never had to rapid (level 3) charge ever except for the few long trips I've made on a weekend.

  • Today, California has excess electricity during late mornings and early afternoons, thanks mainly to its solar capacity. If most EVs were to charge during these times, then the cheap power would be used instead of wasted.

    I couldn't charge my vehicle at home then 'cause I'd be at work, with my car. As an alternative, I'd suggest getting solar panels at home, and use a generator to run really big lights to power the panels at night to charge the car.

    ... if most EVs continue to charge at night, then the state will need to build more generators -- likely powered by natural gas -- or expensive energy storage on a large scale.

    Energy storage will (continue to) get less expensive, so storing excess solar generation for use at night seems like the way to go. In addition, those could be used to store any excess power from other sources like wind farms or nuclear plants -- like the latter sometimes do us

    • As an alternative, I'd suggest getting solar panels at home, and use a generator to run really big lights to power the panels at night to charge the car.,

      As an advantage to this approach, since the distance from the lights to the power panel is static (unlike the sun relative to Earth's rotation), you can set up a vacuum chamber between the panels and the light source to eliminate the greenhouse effect over that distance.

      Good thinking, it's as efficient as solar freakin' roadways.

  • So convenient... (Score:2, Insightful)

    by cuda13579 ( 1060440 )

    Yeah, just charge it during the day...when you're conscious, and using the car. Brilliant. Are we supposed to start traveling and running errands at night?

    • I think you have it backwards. Cars are more spread out during the day, throughout suburbs. During the daytime they're largely concentrated together in parking lots at workplaces. What car doesn't park for at least a few hours during the day, a taxi? This is good. It will be easier to build out charging in parking lots than it would be to equip every home and apartment complex.
      • Oops I meant parking is more dispersed at night, out in the suburbs.

      • It will be easier to build out charging in parking lots....

        That would have made more sense even four years ago, but not so much anymore. For the large number of people working from home, it makes more sense to have charging infrastructure built into the home.

        In the past, it would have even made sense to have charging infrastructure in the grocery store parking lot. However, the increase of online grocery shopping and delivery reduces the effectiveness of that strategy as well.

        If we haven't already reached the tipping point between centralized and decentralized, I t

        • Work from home is an interesting point since it's not just a matter of parking in a different place, but driving fewer miles which would reduce the overall need for charging.

          In looking at the latest figures on total vehicle miles traveled [stlouisfed.org] though I'm not seeing much of a dent compared to pre-covid.

  • More like the the infrastructure needs to adapt to when people will naturally want to charge their cars.

  • Or some east coast focused study, for those of us not on the west coast.

  • Best for who? For the EV owner? For the utility? For global warming and carbon emissions?

    If the utility drops retail price for home owners for the 10 AM to 3 PM window and add surcharge for the 5PM to 9PM window, most homes will chill their pool and use cold water it to cool the homes. No rare earths, no complex batteries needed. A four ton A/C running for four hours, makes 0.66 short ton of ice. A 10,000 gallon swimming pool needs to be chilled by about 2 deg C to provide the same heat transfer.

    May be t

    • Needing an additional 3,750 tons of peak cooling capacity for a 250,000- square-foot addition to its Dallas headquarters, Texas Instruments chose a chilled water thermal storage system: Adding chiller capacity would have cost about $10 million, while the TES system cost about $7 million—and a $200/kW utility rebate reduced this to about $5.75 million. The new system also has cut operating costs about $1.5 million per year and allowed postponement of an expansion of the facility’s high-voltage substation.

      Looks like such systems exist. https://www.pge.com/includes/d... [pge.com]

  • Not everyone can charge at home (Score:3)

    by arosenfield ( 998621 ) on Sunday September 25, 2022 @04:32PM (#62913165)

    Many people in cities don't even have the option of charging at home because they don't have off-street parking, particularly for apartment dwellers. For those people, it's really critical that they have the option to charge at their workplaces, or that cities build out more widespread on-street EV charging options. There are some companies working on EV chargers that could be installed on street lamps, for example.

  • Go nuclear (Score:2, Insightful)

    by stikves ( 127823 )

    Another reason to go nuclear.

    It can run all night, generate no greenhouse gasses, and can keep all EVs charged, reducing daytime fossil fuel usage.

    But we can't have actual clean energy, can we?

    • Re: (Score:2)

      by Burz ( 138833 )

      But current nuclear tech cannot match demand fluctuations, unless its the type used in France. And the French are now paying dearly for reactors that have stress cracks and corrosion from varying the output/pressure all day.

      Demand fluctuates. Renewable energy fluctuates. Storage is needed, regardless... unless the plan is to keep relying on gas generators.

      Nuclear cannot meet the moment right now because that industry turned their backs on storage. But the more we let renewable energy expand grid storage

  • US "For Profit" Electric Utilities Aren't Stupid (Score:3)

    by BBF_BBF ( 812493 ) on Sunday September 25, 2022 @04:44PM (#62913187)

    Don't worry, in the US where most electric utilities are "for profit" private companies, they'll change the rate schedule to whatever makes them most money.

    Currently it's more profitable for them to have EVs charging at night since their systems are experiencing peak load vs. capacity during the day, but as soon as that changes because of transitioning to more wind and/or solar or whatever, they'll change the hours that will allow users of EV's to charge at the lowest rates. So naturally, most EV users will shift their charging patterns to use the lowest rates.

    • Though most of the U.S. power companies are private, there is still plenty of regulation, at federal, state, and local levels, even for the "deregulated" areas.

  • My power company charges a premium for daytime usage, rates are cut in half after 7 pm, so...

  • Current time-of-use rates encourage

    Most of the west coast doesn't have this. And if they're assuming that we'll have time-variable rates in the future, the entire problem they suppose could also be fixed by giving different customers slightly different rate windows. If everybody has something that turns on at 11pm... that's no longer a non-peak time, is it? Dumb. For the problem to be a real problem, the utilities have to be dumb as rocks and not even smart enough to change their rates to ensure profit. Seems like an unreasonable assumption.

  • The Big Picture: It's both, not either-or. (Score:4, Insightful)

    by BobC ( 101861 ) on Sunday September 25, 2022 @05:12PM (#62913261)

    We must view EVs as part of the grid. Though they presently are mostly grid loads, we can expect V2G adoption to rise, and perhaps become incentivized in the very near future.

    First, the load-only situation: The basic goal is to minimize the need to turn on fossil peaker plants. Whenever grid demand is below base load, it's a good time to charge. Whenever the grid has excess renewables, it's a good time to charge. If you have home solar, it's pretty much ALWAYS better to put excess energy into your EV rather than onto the grid.

    Next, the V2G situation. The goal here is for THE GRID (generators + distribution system) to be incentivized to store energy in EV batteries so it can pull it back later, instead of starting a fossil peaker plant. Tesla's VPP (Virtual Power Plant) is a good step in this direction, though industry-wide standards are needed, with buy-in by equipment and EV manufacturers. As these efforts grow, I absolutely expect an update to federal incentives to add support for V2G.

    Now, let's add home solar. The federal incentives starting in January 2023 extend current solar incentives, but for the first time also include incentives for home batteries, which I expect to also be incentivized by state governments AND local utilities.

    Taken as a whole, the grid will want BOTH your EV and home batteries to be topped-off going into times of excessive demand, and also be accessible. Grids may even be incentivized to PAY you to top off your battery(-ies), then pay you again to pull from it/them to the grid. The energy customer as a nano-grid.

    Only with this level of resource flexibility will grids be able to change their base load and peaker plant profiles. Any analysis that assumes the grid will stay the same as EV use rises is simply a BAD ANALYSIS. Done correctly, the addition of batteries to the grid should help EVERYONE involved, yielding a more reliable and less expensive grid overall.

    One other factor: If you have home solar that is making more power than your home is consuming, the grid should offer to transfer that power cheaply (or free, if virtually) to charge your EV while at work. As more multi-unit buildings get solar, the HOA should do the same for tenants. As more employers add solar, they may wish to use any excess to charge employee vehicles. This can be done separately from V2G.

    • Re:The Big Picture: It's both, not either-or. (Score:4, Insightful)

      by iAmWaySmarterThanYou ( 10095012 ) on Sunday September 25, 2022 @09:28PM (#62913607)

      You are absolutely not using the expensive car battery I paid for as part your grid cheap ass grid. I'm not free resources for your government's inability to provide basic services for the citizens.

      Every time you charge/discharge from -my- battery you are reducing its capacity and lifetime.

      Tell you what, you can use -my- battery if I get a free replacement every 5 years. What? That's fucking expensive? Government can't afford that? Yeah no shit neither can I.

      Build more power plants and stop fucking around with critical services.

  • Another reason to charge in daylight: vandals (Score:4, Interesting)

    by msk ( 6205 ) on Sunday September 25, 2022 @05:47PM (#62913331)

    Since I do not have a garage, but do have off-street parking, it looks like daytime will be the best time to charge, when I do eventually have an EV, to reduce the risk of vandalism. My neighborhood, like many, has nighttime looters who like to take things that are not secured. Thus I also expect to have an EVSE that doesn't leave wiring exposed when it's not in use.

    • Oh, wonderful. Copper thieves chopping EV charger cables. Yet another infrastructure problem most people haven't considered.

  • Is this America or communist China?! You can't have the gubbermint interfering with the markets & telling corporations & citizens when to charge their cars. It's not the American way. The American way is for the power companies to buy off the politicians to give them the freedom to price-gauge to maximise profits. Never let things like increases in future demand get in the way of next quarter's profits; that's for the next CEO &/or the gubbermint to take the blame for!

  • "Extra" power is confusing to me, with the supposed grid connecting all of the western US. Yeah, the further the power goes the less you have left, but how much excess are they talking here? And what happens when it occurs?

    I know there were crypto mining rigs that tried to use extra power in Texas, but is that the only helpful/profitable thing we could use it for?

    • "Extra" power is confusing to me, with the supposed grid connecting all of the western US. Yeah, the further the power goes the less you have left, but how much excess are they talking here? And what happens when it occurs?

      It is indeed something of a misnomer; there's never* actually any "extra" power - power generated is immediately used.

      This is because the power companies work hard to only generate what is demanded. There's some inefficiency in this, of course.

      But in general, there's different rates for both generation and consumption. So you have the marginal cost to generate that kWh, cheaper being better. Also, whether power is "dispatchable", IE "generatable on demand".
      The marginal cost is effectively zero for solar

      • Re: (Score:2)

        by MrKaos ( 858439 )

        Basically, in a future scenario with lots of solar/wind, where power production is less dispatchable and less steady than today, shifting towards more control on the demand side is good.

        I can see a day where battery systems become a permanent feature of homes, signaled to turn on and off much the same way off peak hot water heaters and street lamps work by a signal sent via the power lines themselves.

        In millions of homes this is a pretty massive augmentation of the grid.

        Charging EVs when power is plentiful seems like a good option here.

        *There may be occasional exceptions, but they're very rare.

        In some cases the EV itself could be that battery however the situation is when the home itself can take advantage of energy stored instead of it being one way.

        In any case there is an entire new industry of electrical

  • I'm not sure if the study was garbage or just the media's coverage of it. For the most part, the whole thing was just a clickbait bonanza and fuel for the anti-EV MAGA morons. Nothing to see here move on.

  • Then let the house charge during the day (or whenever it's cheapest), so that way it can charge the car at night, instead of directly from the grid. Most folks won't be charging from the office or shopping centres, not enough charging stations. You charge cars when they get parked at home for the night. So help us make that not only possible, but also more affordable by incentivizing home battery power storage.

  • "We're doing it wrong, according to a new Stanford study."

    Shut up, go to your room and don't come out until you've learned to keep your mouth shut. I swear to God, if I hear another "expert" say "You're doing it wrong", I am going to gnaw on that person's pancreas.

    I am going to charge my EV whenever it's convienient for me, and it happens to be at night. If the "experts" don't like it, well suck it up, buttercup

  • In my state (Queensland, Australia) we've started having days where we get negative wholesale rates in the middle of the day, because we have a lot of rooftop solar. Unfortunately it's hard to capitalise on this at the moment as the infrastructure isn't there yet for storage.

    We do have power companies that will sell to retail at wholesale rates but it's a bit risky because when prices go up - they go all the way up. I think we'll see more flexible tariff options soon though.

  • ...when your neighbor is away.

  • Given how most cars spend their lives stationary in the driveway or in a parking lot (attached to a business / mall etc.) it seems the best solution would be to put charge points where they get parked and then charge them from solar. Solar could even be mounted above the parking spots to provide shade. Minimal strain on the grid that way. Biggest issue of course is that this would require laws enacted and construction codes to be updated but its hardly insurmountable.

    Another option would be to incentive p

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