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Utility Rates for EVs

Discussion in 'Energy, Environment, and Policy' started by Robert.Boston, Nov 15, 2011.

  1. Robert.Boston

    Robert.Boston Model S VIN P01536

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    I'm starting work on an article for the utility trade press on best practices for retail rate design for EVs. (Yeah, this is the sort of thing I do for a living.) While my team will do a broad survey of current practices, I'd appreciate your thoughts on what's working and what's not with your own interaction with your utility: rates, metering, etc.
     
  2. VolkerP

    VolkerP EU Model S P-37

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    my smart meter is a one-way device, transferring consumption value every quarter hour to the utility via DSL.
    I want a smart meter that accepts pricing signals from the utility and that I can program to send commands to my devices:
    - car: start charging now!
    - car: drop current to 32A
    - heat pump: now is a good time to fill the hot water reservoir
    - deep freeze: if you can, try to live 3 hours in the evening without electricity. pre-freezing would be good during 2PM to 4PM
    - dish washer: start any time you want between 22PM and 5AM

    Edit: I want full encryption of the power consumption data, of course. And no signaling back to the utility on what devices use any power at the time.
     
  3. rolosrevenge

    rolosrevenge Dr. EVS

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    From talking to Duke Energy, with charging 6.6 kW and below, the extra revenue generated from EV charging pays for the distribution upgrade. Charging at higher rates however requires heavier infrastructure and so Duke would like to charge a higher EV tariff if you home charger is more than 6.6 kW.

    Another good idea is off peak rates for EVs, though, since charging off peak doesn't result in that much of a savings, the average consumer is most likely not going to do it.
     
  4. Norbert

    Norbert TSLA will win

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    #4 Norbert, Nov 15, 2011
    Last edited: Nov 15, 2011
    I doubt these calculations are based on a future with a substantial amount of EVs. What matters then is the ability of the utility to use smart-grid capable chargers (or assigning time-slice-based lower rates to individual customers who then program their car to charge at that time) to balance the load across the night. Then, a higher charge rate actually gives the utility (and/or the customer) a higher flexibility in distributing the load. With that, only the total amount of the charge matters, not the charge rate. And that depends only on how much you drive, not on how fast you charge.
     
  5. rolosrevenge

    rolosrevenge Dr. EVS

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    No, I believe the calculations. Duke's secondary network has between 5 to 10 houses on each transformer. Assuming an average of 8 houses, with a 50% EV penetration rate you get an extra 4 EVs per transformer. With 6.6 kW that's 26.4 kW added to peak, so a 50 kW transformer needs to be upgraded to a 75 kW transformer or a 100 kW transformer depending on the current usage. Now assume 10 kWh of charging per day per EV multiplied by $0.089 per kWh by 10 years and you get $3248.5 per EV. So $12994 to upgrade the transformer. That's in the ballpark of a new transformer.
     
  6. vfx

    vfx Well-Known Member

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    My new transformer was 11K. Glad I did not have to pay for it.
     
  7. Norbert

    Norbert TSLA will win

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    No objections so far, but this doesn't seem take into account that the utilities will want to load balance night charging even then (not because of transformers, but because of other parts of the grid and because of power plant availability), and at night you'll have more power available than at peak, and at specific times during the night you'll have even more power available, so ideally you'll want EVs to overlap in that area, or even some EVs to charge only in that shorter period.

    So I'd expect that while they will want to put a limit on during-the-day charging, they will eventually welcome the flexibility that comes with higher charging rates. If the charger itself is limited to 6.6 kW, then there is no possibility to take advantage of the most optimal time in the night. Whereas otherwise the charger or the car can still be set to a lower charge rate if used during the day.

    Once you have 500 mile batteries (this is actually IBM's goal for Lithium Air batteries), and even with 300 mile batteries as the Model S will have in July 2012, with 6 kW you cannot charge it anymore during the night alone. Think of events such as when lots of them come home after Thanksgiving, and you would't want all of them to continue charging into the next day.
     
  8. Lloyd

    Lloyd Active Member

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    If you input the time you next need your car, and let the car randomize the charge time during the rate decrease, it should prevent surges, or everyone trying to start charging at 10Pm when the rates go down. I can see problems developing if eveyone sets to charge beginning at 10pm!
     
  9. SByer

    SByer '08 #383

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    So, I think PG&E has made a mess of things, especially with their SmartMeter rollout. Many of their actions seem to be a cynical attempt to avoid being dragged into the 21st century by their customers.

    We're on the E7 plan, not the E9 plan. Which would be better? Not quite sure because it all depends on when you use the juice, but my bet is that E9 would be a bit more. I charge mostly at work, when I do charge at home (rare), it's always off peak. PG&E has enough data that they could run 'what if' numbers, but I don't think anyone would trust them to allow us to switch to the plan that works best for us, not them (which is why PG&E doesn't need to know I have an EV).

    PG&E offers a 'your data' service that's not very good - the resolution is low (15 minutes?) and I don't think the data is updated until the next day. I know the meter itself has a nice optical port that could provide real-time output. Sigh. Made that issue irrelevant by having a TED installed at the same time as we had to have the house panel replaced.

    The solar tariff feedback program in CA is a joke, and I'm pretty sure it was PG&E getting it's fingers into that mess that is partly to blame. You can't get money back unless you're a net power provider, not just net negative at true up. Big donut hole.


    So, I'd have to say, the relationship is somewhat adversarial - I don't trust them, they seem to do the minimum necessary to provide the service, often only when the PUC forces them to. Some honesty from them and some genuine moves to help customers and improve efficiency would go a long way. They are just not good corporate citizens.
     
  10. Lloyd

    Lloyd Active Member

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    PG&E will pay you back this year for any net Negative at the end of the year, but don't let the $ figure negative on your bill fool you! They will only pay you back at $.04 per KWH which is only a small fraction of the negative dollar figure on your bill.
     
  11. rolosrevenge

    rolosrevenge Dr. EVS

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    All very true, but if the charger is greater than 6.6 kW, than the utility has no guarantee that you won't charge on peak. It is easier for them to set a single EV tariff. I'm not saying that it is the best solution but as I showed, it covers their concerns of keeping the lights on.
     
  12. Robert.Boston

    Robert.Boston Model S VIN P01536

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    But, if you have a smart meter, the utility can determine whether you've charged above 6.6kW on-peak and charge you accordingly.
     
  13. Norbert

    Norbert TSLA will win

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    #13 Norbert, Nov 16, 2011
    Last edited: Nov 16, 2011
    They have no guarantee with air conditioning (+ 6.6 kW, + plasma TV and whatnot) in any case, and if they had proper off-peak charging, rarely anyone would charge during the day at all. The only thing that gives them a guarantee is the smart grid. If they aren't smart, and try to cut corners instead of properly supporting EVs, the DOE will move quickly to force the smart-grid with regulations in a way that will be less pleasing to their comfort zone. ;)
     
  14. ckessel

    ckessel Active Member

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    PGE (not PG&E) has an off-peak rate of .04422 $/kWh. It's going to be insanely cheap for me to charge, something like 1/15th the cost of gasoline.
     
  15. rolosrevenge

    rolosrevenge Dr. EVS

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    But you do largely have a guarantee if you have a larger transformer, which is what they will do once a certain number of EVs are purchased on the feeder. Clearly smart grid technologies are the best. In my ideal world the utility would charge you $0.01/kWh to charge your EV whenever you plug in, and would perform V2G optimization throughout the day ala-awesome research concepts but we'll see what actually happens.
     
  16. Norbert

    Norbert TSLA will win

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    #16 Norbert, Nov 16, 2011
    Last edited: Nov 16, 2011
    And the second best is off-peak rates which are different enough from peak rates so that they keep people from charging during the day. That's 0 kW vs 6 kW. Why do they have to restrict hardware itself if it used only during the night? That's not easier but counterproductive, unless I'm missing something. Or are you saying they can't even measure according to time-of-day? Do you think it is OK to charge extra for a Tesla 10 kW charger even if the charger is never used in the day, the point being to allow charging completely during off-peak time?

    EDIT:
    And it seems that it will force them to buy transformers which are far too large, since they need to support 6 kW per EV on top off everything else (to support the worst case) at peak time, which wouldn't be necessary with smart-grid equipment.
     
  17. Robert.Boston

    Robert.Boston Model S VIN P01536

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    The off-peak rate has to be sufficient to at least pay the operating costs of whatever generators are supplying the power; if it's any kind of fossil plant, you're looking at $0.03/kWh upwards. Your point is good, though, that utilities recover a bunch of charges (transmission, distribution, capacity, competitive transition charges, conservation charges, system benefit costs, etc.) through a per-kWh charge that is constant in all hours; many of these costs should be shifted to peak usage, or eliminated from the EV tariff.

    Here's a challenge: if you exempt EVs from paying certain charges (e.g., conservation charges), how do ensure that the consumer doesn't abuse that rate by plugging other appliances into the EV meter? After all, I could run my chest freezer on the same outlet as I charge my Model S.

    Re V2G optimization (what I call "carbitrage"), we need to work out payment systems that compensate EV owners for the increased battery degradation. I'm not completely sure that people would be willing to provide V2G services unless compensation was quite substantial: we all care a great deal about preserving our car's range.

    Query: should EVs have an extra levy on our power rates that goes to the National Highway Trust? If not, explain why.
     
  18. GSP

    GSP Member

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    This could be a non-issue if V2G was designed as two-way communication, but only one-way power flow to the vehicle. The car could tell the utility its planned departure time, and how much energy it needs before then. The utility could charge when most convenient for them. If 60 MW of spinning reserves were needed, they could temporarily take 10,000 6kW chargers off-line. This would be just as good as drawing 6kW from 10,000 fully charged vehicles, without impacting battery life.

    GSP
     
  19. SByer

    SByer '08 #383

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    Are you sure about that? Everything I've found indicates that unless you produce more electricity than you use, you get nothing back, and the new net surplus compensation program, only applies to net generation, not net value, leaving a big hole in between.

    From the PG&E FAQ:

     
  20. Robert.Boston

    Robert.Boston Model S VIN P01536

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    The whole point of V2G is that it's "Vehicle to Grid". What you're describing is just intelligent charging -- valuable, but only half the pie. If the grid operator has 100,000 V2G EVs plugged in on a hot summer day, each with a 10kW dual-direction interface, it has 1,000 MW of synchronized reserves, the equivalent of a having a backup nuclear station (but instant-on). Currently we pay power plants serious bucks to operate below their maximum normal rating to provide this same spinning reserve service, which is both costly and polluting. And, as an added bonus, this power source is concentrated in urban areas (where we've parked during the workday), so the extra power is readily deliverable to load.
     

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