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Returning Power From Electric Cars To the Grid

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  • by Smidge204 (605297) on Tuesday September 27, 2011 @10:12AM (#37526082) Journal

    This idea is kicked around a lot, and there are some pros and cons.

    The intention is obvious: use stored energy in parked vehicles to help smooth spikes in demand and evenly distribute the load on the grid. But the difficulty is that people will want their cars to be charged when they leave work or the train station to head home, and peak demand is usually during those hours. Not only will a lot of cars be getting unplugged right when you need them, but few people will be willing to part with charge they might need to get home.
    =Smidge=

    • Not only will a lot of cars be getting unplugged right when you need them, but few people will be willing to part with charge they might need to get home.

      It's not just the charge issue. I would be completely and utterly unwilling to lower my battery life through this extreme charge-recharge cycle. Those things are expensive.

      • by loshwomp (468955)

        . I would be completely and utterly unwilling to lower my battery life through this extreme charge-recharge cycle.

        Yawn. We've been over this a million times, but TFA was light on technical detail, so you're forgiven.

        It's not an extreme cycle, it would be managed so as to be transparent to the end user (of the vehicle), and you'd get paid handsomely for your (voluntary) participation in amounts TBD, but which would exceed amortized battery wearout cost by roughly an order of magnitude. In any case there are hundreds of dollars per month on the table.

        Also: Your traction battery has an inherent calendar life wearout me

        • by SrJsignal (753163)
          Hundreds of dollars per month. You are either purposely making stuff up, or horribly bad at math.
          I suppose you could be spouting off someone else's fake numbers, which would just make you ignorant.

          Anyway, lets do some math:
          24KWh battery (Nissan leaf, and we'll give you the entire battery, just for grins).
          I'll even grant you a ridiculous number for power cost (average wholesale energy cost in TX $0.045 / KWh) we're talking peak so lets go with $0.10 / KWh
          24KWh*$0.10/KWh*30days = $72.00 Oh and by t
          • by loshwomp (468955)

            Anyway, lets do some math

            Both you and the AC above are still on the wrong track, but since you had the courage to log in, I'll reply to you instead.

            If you don't understand the difference between energy and power, read up on that first, or there isn't much point in further discussions of V2G. V2G is about power, specifically in the "ancillary services" regulation market. It is *not* about energy, and in particular it is not about macro scale regulation, which is why your energy calculations aren't relevant. (This is also why your

      • by yog (19073) *

        I agree; I would want my (someday, future) rechargeable electric vehicle to have all its charge available to me at all times. I might want to run out to the 24-hour place for a Ben & Jerries fix at 3AM. Or, more seriously, there might be a medical emergency with a member of my family, or whatever. Who would want to limit their mobility during the off hours? It's like giving up use of your car half the time.

        I'd like to see more emphasis on charging cars at work, since the majority use case in the U.S

        • by h4rr4r (612664)

          We are talking about reducing the range for minutes at a time and by only 10% or so. Do you keep your gas tank 100% full at all times?

        • by Alsee (515537)

          parking their car all day in the *sunlight* or inside a garage that is drenched in *sunlight*, then driving home at dusk and leaving it parked all night. There's got to be a way to refill at least a few miles' worth of power during that idle daytime.

          I googled solar power figures and electric vehicle power figures and did some quick and dirty calculations. Under the ideal case of your car parked in full sunlight for a full day, facing in the ideal direction towards the sun, and with a solar panel covering a substantial area on the car, you could get maybe 2 or 3 miles of charge per day. In real world usage you'd be lucky to obtain even half that.

          My first reaction was that a mile a day is not much, but yeah it's still, kinda cool and with an optimistic v

          • by yog (19073) *

            It's not really hard to pay off the initial costs of solar panels; it just takes a long time. Rule of thumb is about 10-15 years depending on how many panels, how sunny your location, etc.

            You don't necessarily have to mount your own solar panels to your own car; a whole bunch of them on top of a garage, or on top of your shaded spot (common to have parking shades in places like southern Arizona where it can be 115 F *outside* the car, 120 or 130 inside). It's a function of how many panels are feeding into

    • by LWATCDR (28044)

      You are missing the real beauty of this system.
      1 . It takes x+n to get a full charge on the battery and they charge you for x+n.
      2. When you discharge a battery you x and then convert it to ac you only get x-n power out which is what the power company will credit your account.
      3. You will have to pay for x+n again to get back to a full charge.
      4. Profit.

  • Both (Score:4, Insightful)

    by hackertourist (2202674) <(hackertourist) (at) (xmsnet.nl)> on Tuesday September 27, 2011 @10:13AM (#37526104)

    It's genius in that it allows load levelling without much investment by the power company, it's silly because the investment will just be moved to the user: Adding one charge cycle per day means that battery life is halved.

    The only way this will take off is for users to have a financial incentive to allow the power company to do this, ie the power price during peak demand must be so high that it's cheaper to deplete your EV battery rather than draw from the grid.

    • by ITShaman (120297)

      Yeah, it's genius for the electricity generating companies, they can get the car owner to pay for the fuel to generate the electricity to charge their car.

    • Re: (Score:2, Interesting)

      by Anonymous Coward

      Exactly, the only thing holding EVs back is battery prices. There's no way you let someone borrow your $10-30k battery to run their AC.

      Current batteries cost $0.13/kwh over their lifetime, which means you need to pay me $0.20/kwh plus the regular utility rate if you want that power. If you're in a high demand area, you're up to half a buck / kwh. Might as well just keep burning gasoline to meet the demand.

    • Re:Both (Score:4, Interesting)

      by Spoke (6112) on Tuesday September 27, 2011 @12:35PM (#37527812)

      It's genius in that it allows load levelling without much investment by the power company, it's silly because the investment will just be moved to the user

      Users will only allow this if they are compensated appropriately.

      Adding one charge cycle per day means that battery life is halved.

      Typical use case won't involve anywhere close to a full cycle. Today, typical use of an EV involves a partial cycle - probably 1/3rd to 1/2 cycle. 2 half cycles is easier on a pack than one full cycle - you can probably get 2-3x more "full" cycles by only half-cycling a modern battery pack. Limit depth of charge/discharge even more and you'll get even more use out of the pack.

      That said - the real value won't come from performance large charge/discharges. It will come from many small charge/discharge events to provide grid regulation services. If a big load pops on, draw a bit of juice from batteries while conventional generators spin up. When it turns off use the excess juice to charge batteries.

      Conventional generators are not good at spinning up and down quickly to match changes in load - by buffering this load and allowing the big generator to run closer to constant load you can significantly improve it's operating efficiency. Very frequently this inability to quickly match changes in load is what causes black outs (the recent San Diego blackout is a good example).

      Worst case you're looking at a really hot or really cold day and you want to be able to draw 5 kW from storage during peak. This can go a long ways. I know that some utilities will pay [sdge.com] ~$50/year just to have the option of being able to remotely control your air conditioner to keep it on a 50% duty cycle for one hour - they'll pay up to $200/year to have the option of being able to keep it off for a whole hour - and they may never need to use it!

      So imagine being paid to simply leave your car plugged in to the grid just so the utility has the option of drawing power from it - and then being paid more if they actually use it. Having these resources available at little cost can be worth their weight in gold when they are needed.

  • It seems like the energy loss of moving energy from the grid to the cars, then back to the grid, could potentially be too great to justify the investment. I would think large arrays of dedicated stationary batteries might be a better choice.
    • by skids (119237)

      It seems like the energy loss of moving energy from the grid to the cars, then back to the grid, could potentially be too great to justify the investment.

      It's offset by the inefficiency of suddenly having to fire up coal plant turbine or keep a gas turbine in spinning reserve mode just to handle a temporary peak. Which is why storage facilities like those built by Beacon Power/A123/VRB systems can turn a profit.

      I would think large arrays of dedicated stationary batteries might be a better choice.

      No argument there. Car batteries are optimized for weight and the extra electronics for grid feedback are better bought/installed in bulk. A dedicated stationary facility can use battery/storage technology that doesn't have this restriction, and us

    • Two mistakes: first, there is not much power loss in returning power from the battery back to the grid. Second: if you have stationary batteries you have not only to buy and install them and attach them to the grid, but you also have to use them to pump energy back to the grid. With a car you can as well use the energy for what it is ment to be used: drive away!

    • by loshwomp (468955)

      It seems like the energy loss of moving energy from the grid to the cars, then back to the grid, could potentially be too great to justify the investment.

      Guess what. Smarter people than you who have actually researched it have come to the opposite conclusion.

      I would think large arrays of dedicated stationary batteries might be a better choice.

      And what would be different in that case, which is precisely identical except for requiring even more batteries to accomplish the same result, since the fleet of vehicle traction batteries would not be used to their maximum effect?

    • by necro81 (917438)

      I would think large arrays of dedicated stationary batteries might be a better choice.

      How is a parking lot full of EVs not exactly that?

      • I would think large arrays of dedicated stationary batteries might be a better choice.

        How is a parking lot full of EVs not exactly that?

        Two main things come to mind immediately:

        • Battery technology and configuration - The way EV batteries are set up in terms of input and output are optimized for driving electric motors. Voltages, amperages, etc would likely need to be stepped up or down to be delivered to the grid. And if your parking lot is 1/3 Honda, 1/3 Toyota, and 1/3 Ford, you may need to handle 3 different systems that need to be connected to the grid differently.
        • Density - An electric car is not just a battery. It has all th
    • by dr2chase (653338)

      As others have noted, smart people have worked on this. Consider that this is for smoothing peak loads, and that a big component in transmission loss is I-squared times R. The cars are close to the loads, so car-to-load transmission costs could be lower, and longer-distance variation is avoided. In particular, they could just use the car to reduce load from just your house -- no transmission costs at all.

      Compare losses for a steady current of "1", instead of 0.5 half time and 1.5 half time. 1 x 1-square

    • Currently, the most popular scheme for storing electric power is pumped (water) storage, which is about 70% efficient. So this idea can be economical even if significant losses occur. The alternative is to start up expensive peak power plants (gas turbines).

  • by elrous0 (869638) * on Tuesday September 27, 2011 @10:15AM (#37526132)

    Considering how much rechargeable batteries "leak" energy when they sit, does anyone take this into account when they're touting all these great energy savings that electric cars are supposed to provide? I mean, I drive very little. Most of the time my car is just sitting around. But with a gas-powered car, it's not like I'm losing gallons of gas letting it sit for a few days (or even a week). With an electric car, even with one of the newest batteries, I would be losing power even if I'm not driving it, right? Yet I never hear any of these green types addressing that. Just think of all the power that would be wasted just in long-term airport parking.

    • by afidel (530433)
      Modern Lithium chemistries leak 1-5% per month, so no, it's not a significant factor in their environmental impact. And cars without a properly seated cap will lose at least as much gasoline (much less so for diesel, though the vent from our storage tanks can be significant in hot weather).
    • by loshwomp (468955)

      Considering how much rechargeable batteries "leak" energy when they sit

      A common misconception, part of the myth and lore surrounding batteries, a la "charge memory" and other BS. Modern lithium traction batteries (i.e. those in cars) do not suffer any significant "self discharge". It's on the order of a few percent per year.

    • Considering how much rechargeable batteries "leak" energy when they sit, does anyone take this into account when they're touting all these great energy savings that electric cars are supposed to provide?

      Decent (I.E. not consumer grade) rechargeables hardly leak at all. The spare battery for my (semi-pro) camera sits for weeks without losing any noticeable charge at all. On the other hand, the (consumer grade) AA's I use for other purposes have a noticeably short shelf life.

      Most of the time my car

      • by kf6auf (719514)

        Nowadays almost all camera batteries provided by (computer, camera, car, etc.) manufacturers are Li-Ion and almost all rechargeable AAs are traditional NiMH, so it sounds to me like you are comparing different chemistries and erroneously concluding that the result is due to the quality of the battery.

        Li-Ion batteries and low self-discharge NiMH batteries discharge 2-3% per month. Traditional NiMH and NiCd batteries discharge15-30% per month. If you buy the low self-discharge NiMH batteries, you won't lo

    • by Orne (144925)

      No, they don't "leak" like transistor gate current or capacitor voltage. Googling around, NiCad batteries have a charge decay of over 2 months (full to empty), but my experience is that almost all electric car batteries are now lithium based, which doesn't appear to have this issue. The Chevy Volt, Toyota Prius, Toyota Highlander all use lithium-ion. Bulk-electric batteries that I've seen are lithium titanate, sodium sulfur, and some weird lead variants.

      Battery charge is usually measured by efficiency,

  • I've heard a lot that the number one concern over electric (and even hybrid) cars is the life of the battery system. It's extraordinarily expensive to replace, so I'm just not sure that repeatedly charging and draining it during the day a little bit at a time would be worth the possible wear and tear on the battery to justify such a thing. I know there has been a lot of progress towards reducing battery "memory," but still, I couldn't help but think that such a thing would cost me a lot of money a lot soo

    • there is a common misconception that it's necessary to have a large ultra-expensive highly-polluting rare-earth-metal battery pack. you don't. the conditions for not needing a $25,000 battery pack (worth stealing) are as follows:

      * the vehicle weight must be under 550kg (400kg EU Category L7E is perfect)
      * low-rolling resistance tyres are essential
      * you must be happy with a top speed of 60mph and a top cruising speed of about 55mph
      * the frontal area of the vehicle must be no more than 1.5 sqm
      * the drag coef

    • by loshwomp (468955)

      IAAEVE (I am an electric vehicle engineer) and I don't know how to combat these misconceptions other than by brute force, over and over again, so here we go:

      1) V2G is not adding many cycles to the battery. The value (and thus the money on the table) is primarily for being *available* and for being available instantly. For a utility company, the alternate source of regulation services is to ramp a generator up/or down, and that takes TIME. A fleet of vehicles can respond in milliseconds.

      2) The system woul

  • As a prius driver (Score:5, Insightful)

    by Gideon Wells (1412675) on Tuesday September 27, 2011 @10:18AM (#37526170)

    Silly as hell for now.

    I can't count how many times I parked my car with my battery being "full". I mean, if surplus energy were such a huge issue then why is Toyota releasing models now you can plug in for extra "fuel efficiency". For hybrids there can't be that much of a demand. I mean, this means I would need to use more gas to charge my car more to get my good fuel efficiency, partially defeating the purpose of the car.

    This seems even sillier for pure electric cars. You might as well argue that each home should have a pipeline to gas stations to siphon off their gas, in exchange for money, which you can buy back at the gas stations.

    That hybrid and electric car batteries may need tapped enough to use in this system is a more worrying scenario for me. What the bleep is wrong with the local grid that we are that pinched for energy? There are fluke events that make this impractical, or it happens enough which means to me there is something wrong with the regional system that needs fixed. Not my car drained of "fuel".

    Now, solar cars (maybe even cars with mini wind turbines?) I can see being part of this if you leave your vehicles outside. Once, if, your battery fills up you can sell surplus energy back as your car could be generating power during non-use unlike current electrics or hybrids.

    • by Anonymous Coward

      As a Prius driver, obviously this is not relevant to you, because you do not drive an electric car. You drive a gasoline car.

      (Unless you've got one of the very latest Priuses, or you've modded your car.)

    • Silly as hell for now.

      Hm, perhaps you should elaborate more?

      I can't count how many times I parked my car with my battery being "full". I mean, if surplus energy were such a huge issue then why is Toyota releasing models now you can plug in for extra "fuel efficiency".

      Because plugging your Hybrid into the Grid let you load it for less than a 4th of the price (than burning your own gasoline) and with perhaps 5 to 6 times the efficiency regarding CO2.

      For hybrids there can't be that much of a demand. I mean, th

  • As long as I get paid for giving electricity back to the power company. Maybe then I could make back the cost of the car by charging it at night at my house, and then plugging it in at work and selling it back at a high cost per kwh.
    • Or you could just get a bunch of batteries and an inverter and hook up a PLC to a smart meter and bam!, electricity arbitrage. Although, I would think that there are better storage mechanisms than batteries. I'm kind of left to wonder how this is patentable, as I could put something like this together quite easily and I'm not even that good.

  • by ledow (319597)

    How do you maintain availability of power for the car owner?

    Yes, sure, you might be able to harness some from, say, a haulage company at the end of the day when they shut up shop but in general you can't just steal charge from people's electric cars (because the first new-father in the middle of the night that can't drive his wife to hospital is going to create a ton of bad press for you).

    So you're basically looking for places that leave stored-charge cars alone, for a significant period of time (enough tha

    • So you're basically looking for places that leave stored-charge cars alone, for a significant period of time (enough that they will have a FULL charge by the next time they are needed even after you've discharged them), will never use them in that time, have electric fleets large enough, have the time, money and effort to implement that sort of infrastructure at all the necessary sites (pumping back to the grid requires yet-another meter and converters, surely?) and are willing to let you do so (i.e. you pa

      • by 0123456 (636235)

        Here are roughly 1000 cars "stored" underground which are not used for 9h every day. Some people work from 6:00 to roughly 15:00 and the others from 9:00 to roughly 18:00. There is plenty of options to use those cars. Especially if the bank would own them and "rent" them to the employees.

        That's great. Except when I want to go shopping at lunch-time or when I have to drive a customer to the airport or when I get a call to say my girlfriend had an asthma attack and I have to collect her from the medical clinic.

        Keep in mind: if you have a station where you can charge your car, it is only a little bit more money to be able to uncharge it and feed it to the grid.

        Keep in mind: if I've plugged my car into a charging station it's because I want to be sure it's charged the next time I need to use it.

        • You make no sense.

          Keep in mind: if I've plugged my car into a charging station it's because I want to be sure it's charged the next time I need to use it.

          Then don't buy the contract of the power company that offers you to sell power back. Or if you buy it then set your load controller to: I want at least 50% charge ...

          Or well start thinking a bit and get some common sense.

          Franky, why is everyone reacting so emotional? Do you really think "they" are "stealing your charge"? We are talking about technology her

    • by PPH (736903)

      So you're basically looking for places that leave stored-charge cars alone, for a significant period of time

      Cop cars at the donut shoppe.

  • This was discussed on slashdot in 2007:
    http://tech.slashdot.org/story/07/07/27/2312257/toyota-unveils-plug-in-hybrid-prius#comments [slashdot.org]

    And it's not a very good idea:
    http://www.nytimes.com/2007/09/02/automobiles/02POWER.html [nytimes.com]
    "The V2G potential of Honda’s full hybrid vehicles is unexplored, but the company is doubtful of using them to power homes. “We would not like to see stresses on the battery pack caused by putting it through cycles it wasn’t designed for,” said Chris Naughton, a Honda

  • I really wonder if they live in an Ivory Tower or whether the US patent sysem is indeed that retarded.

    After all research projects regarding this are up to 20 years old and working examples exist since far over 10 years.

  • I thought the point of having an electric car was to avoid using gasoline? If I have a drained battery at the end of the day and you assume that I have a combustion engine as a standby, I'd have to use petroleum to get home. FAIL. If the car is electric only and relies on the grid to charge, I'd end up walking home. FAIL.

    Now if we were talking about some sort of super capacitor that can drain and then be quickly replenished this may have a useful effect to normalize daytime power usage, but only for sho

    • by Bengie (1121981)

      Which is why you tell the system to only discharge your battery to a certain point

      "Keep my battery at: 80%" There you go, never a dead car.
      "Keep my battery at least 70% and have it at 80% by 4:30p" there you go

      We're not talking about dumb systems here.

  • Okay, so here's the deal. The power grid has to be built to support peak load, not average. If there are three days out of an entire year where the customers of a power company use more power than the whole rest of the year, then that power company has to build out their infrastructure to support the demand of those three days. There are some exceptions to this, based on energy trading from neighboring sections of the grid, but since peak demand is usually driven by time of day and current weather, you c

    • Or, you could do what developing countries do, and reduce the quality of power in case of high demand.

      resort to blackouts in case of not being able to cope up at all

  • I've heard this over and over again and usually from utility company representatives and it's a waste of time, money and effort. I think it's more of a public relations thing than anything else since there are not enough electric cars on the market or projected to make a difference.

    Why do you never read or hear anyone mention the number if vehicles required to have enough capacity to be meaningful? It's a waste of time and if anything just another way Utility companies to get funding from Public Utility Co
  • It's genius if they manage to get the patent, but it's silly because lots of people have prototype systems already, like Nissan/Renault.

  • Assuming this is voluntary or fairly priced, this can alleviate several problems that the grid faces. First there's no need to drain the battery completely and the rate at which power is to be fed back to the grid is adjustable. If the utility uses a bid-and-offer system, you can decide at what price to sell; if the offer isn't worth what you think for the fairly minor reduction in battery life, then don't sell.
    All of this can be automated and the benefits for absorption / mitigation of intermittent sources

  • I think it is time to really rethink the grid...
    We are starting to have technology of cheap and less environmental impact technologies that can power a few houses. Perhaps the grid should be cut back and in favor to small community power sources.

  • If the charging point is at my home, it's (probably) my car that's plugged in. But a public point at the railway station or the office?

    Are all the charging points now going to have to recognise my car or take a swipe card if I want to be paid? (Cue the 1984 posts.)

  • Consider long-term parking lots, used car lots, occasional-use cars etc. etc. Distributed computing has proven its value. So, Why not distributed power storage? Currently, this proposal does seem silly. But, given a much wider use of plug-in cars as well as improvements in battery technology -- combined, perhaps, with some interactive mobile apps -- it is not hard to envision scenarios wherein, by participating in the power co's storage program, one could amortize one's energy costs.

    Also future cars might

  • Bad idea. Little generators and engines are much less efficient than big ones, so using hybrids as peaking plants is a desperation move. For pure electrics, the general idea is to keep the battery charged up in case the user wants to go somewhere.

    The whole "smart grid" thing is mostly a marketing move to collect information about consumers and get rid of meter readers. All that's really needed for peak management is a system that broadcasts how much the grid needs power right now [caiso.com] and the current power pr

  • I bet it doesn't make sense when you factor in the cost of wear and tear on the very expensive batteries (that have a finite life of useful charge/discharge cycles).

  • Isn't back feeding the grid dangerous?

    In addition to people causing fires when using a generator to backfeed their home, I have read that this can harm electrical workers who are trying to fix the wires.

  • At some point, new cathodes, anodes and electrolytes, or moving entirely to something like supercapacitors may allow you to fully charge your car in 30 seconds (the electric grid will need beefing up too).

    That'll take years and years and years but at that point it may be useful. And then they can pull out this patent.

  • If i had an electric car, I wouldn't want the battery to be any less than 100% full at any time. Who knows, maybe I want to take it out on a max range trip. Therefore, there is no "spare capacity" on active car batteries that you can use.

    However, in about 10 years tens of thousands of EV car batteries will be leaving warranty. They may not have the storage density necessary for vehicles, but they will still have functional storage capacity.

    I can very easily see that those batteries then will be used to c

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