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Power Transportation

Returning Power From Electric Cars To the Grid 247

Posted by timothy
from the electrifying-news dept.
First time accepted submitter icensnow writes "NRG is patenting a means of returning electric power from charged but inactive electric cars to the grid, essentially turning parked electric cars into an energy storage system for the grid. I'm having a hard time deciding if this is genius or silly."
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Returning Power From Electric Cars To the Grid

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  • Re:Both (Score:2, Interesting)

    by Anonymous Coward on Tuesday September 27, 2011 @11:05AM (#37527430)

    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 @11:35AM (#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.

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