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Managing Supercharger demand in partnership with the utilities

Discussion in 'Charging Standards and Infrastructure' started by ka9q, Jun 24, 2018.

  1. ka9q

    ka9q Member

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    Just being a little pedantic -- kWh (kilowatt-hour) is a unit of energy. kW (kilowatt) is a unit of power, i.e., the rate of energy flow.

    I've often noticed varying supercharger power levels. I can think of several possible reasons aside from the obvious one (contention from the paired spot). One of the most plausible is site demand management; particularly during peak hours, utility demand charges are substantial at commercial sites (that's how they make their money) so it's quite possible that a Tesla supercharger site tries to limit the total demand of all the chargers at a site to stay under some limit unless it's clear that the site can consistently make use of higher power levels for an entire month.

    Also, many sites now have stationary battery plants to help limit utility demand, and it's entirely possible that the SC power levels are adjusted depending on their state of charge. Some have PV panels (e.g., Kettleman City) and their production could also be a factor.

    If I were Tesla, I would definitely be negotiating with electric utilities to let the utility remotely control a SC site's total demand in real time in exchange for substantial rate discounts. The entire electricity industry is definitely headed in this direction, and EV charging is one place where it makes a lot of obvious sense.
     
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  2. AMPd

    AMPd Active Member

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    No offense but thank God you’re not Tesla.

    Good luck advertising a charging network that takes 3 hours to charge a 100D.
     
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  3. ka9q

    ka9q Member

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    You can rail against the laws of physics, reality, and the facts of life, or you can work with them.
     
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  4. ka9q

    ka9q Member

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    I should point out that real-time utility load management doesn't always mean enduring slower charging to save money.

    Running an electric grid is a constant balancing act to ensure that supply and demand are exactly matched at all times. This is getting more challenging because of increasing renewable generation along with "must take" rules that require the grid operator to use electricity from renewable sources whenever available and technically feasible.

    Unlike fossil generation, renewable sources are usually non-dispatchable, meaning that something must make up for any fluctuations in renewable power generation plus the usual fluctuations in total demand. Ideally those fluctuations are absorbed by hydroelectric generation, the one renewable electricity source that can (now) be rapidly dispatched. But hydro is limited, so in many cases much of the variation must be tracked by fast-acting natural-gas-fired turbines. (And in the future, by batteries.)

    Some of the load-minus-demand difference can be forecasted, some of it is just random noise. For example, in California we have something called the "duckbill curve", the daily requirement for fossil generation that climbs very rapidly in the late afternoon as solar generation is shutting down and evening loads are picking up. It's now typical to see fossil (nearly all gas) generation ramp up at 3 gigawatts per hour or even faster.

    Problem is, even many gas turbines can't change their power levels on a dime so the CAISO (the grid operator for most of the state) has to dispatch gas turbines in advance to be ready when the forecasts show increased load. While they're ramping up, there can just as easily be a surplus of electricity as a deficit even though it may be nominally during the late afternoon "peak" period. (Right now, some wind and solar energy actually has to be curtailed -- wasted -- because of this problem.) This creates an excellent opportunity for a grid operator to solve the problem by ordering large EV chargers (and other loads that can be easily dispatched in real time) to absorb the excess generation at a very low price until the forecasted load actually materializes.

    None of this is an argument against either renewable energy or electric vehicles; I'm a huge fan of both, and these engineering problems simply must be solved. But it also means the electricity industry that we see as customers will be different from what we're used to. Sure, you can say we Tesla drivers are so rich that we (or Tesla) should just buy our way out of the economic realities that the hoi polloi must face. I don't know about you, but one of the main reasons I drive a Tesla is because I see it as something much more than a rich person's toy. I see it as a prototype for what nearly everyone will be driving in another generation or so.
     
  5. AMPd

    AMPd Active Member

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    I read all of that and none of it had anything to do with your original statement.
    You said if you were tesla then you’d want the superchargers throttled for a FINANCIAL incentive.

    If your goal is to screw customers to SAVE money, then your company is not long for this world.

    The fact is to get people to switch to electric means of transport then you need as few drawbacks as possible. The supercharger network went through some issues a while back where many sites were experiencing slow charging speeds. So slow in fact my wife no longer wanted to take the model s on our weekend trips.


    The reason I bought my tesla is because it has no drawbacks vs an ice, but if one day Teslas supercharger network is being throttled because they want to save money by shaving electrical load, then I’m out.
     
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  6. GSP

    GSP Member

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    As @AMPd points out, superchargers are used when drivers are on long trips, and they want to charge quickly and be on their way. They are not good candidates for managed charging. Stationary batteries would be a better way to manage demand charges at superchargers, even though they will cost more.

    However, destination chargers and home chargers are prime candidates for providing the managed charging that @ka9q describes (sometimes called "V1G"). Car owners could just enter the time that they need the battery to be finished charging (and percent SOC or rated miles needed). Utilities could then start, stop, or change the rate of charging to help match supply and demand.

    GSP
     
  7. Lasttoy

    Lasttoy Member

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    Charging at SC has nothing , zero, to do with local power company. I have interviewed several workman installing the SC.
    The local firm supplies 480 volts AC power. End of story for them.
    Tesla installs the inverters, AC to DC to car. There are 2 chargers for each inverter. 1A 1B. 2A 2B and so on.
    When you get on the same inverter, your charge rate drops. Walk over and listen, they are huming .
    Now to your charge rate,
    There are 100 varibles, i keep a very detailed log, i have been in 20 states, many cities. Never ever the same numbers.
    I drive to DC often, 5 stops, same places, never ever same rate of charge.
    Outside temp. Amount you want, alone, time of day, leave ac on? Etc etc
    I can charge to the max 250 miles, but rarely do.
    I have 120k miles, love it.
     
  8. lklundin

    lklundin Active Member

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    Munich
    Right, and as for the solution to variable electricity prices, I believe that Tesla is installing their own powerpacks on at least some stations - so they can buy electricity when it is cheap and deliver the promised power when they need to.
     
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