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Vehicle 2 Grid

Discussion in 'Roadster 2008-2012' started by GSP, Sep 23, 2020.

  1. slcasner

    slcasner Active Member

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    Forgot to include again that the AC Propulsion AC 150 controller can do V2G, either pulling power to charge the battery or pushing power from the battery. So it's possible that the Roadster 1.5 PEM can do this, too.
     
  2. AEdennis

    AEdennis Active Member

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    Correct... This is the history I was referring too in so few words that you expounded on.
     
  3. wycolo

    wycolo Active Member

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    #23 wycolo, Oct 3, 2020
    Last edited: Oct 3, 2020
    > Only legal (at least where I live) if there is some automatic mechanism to prevent the car from sending power toward the grid unless the switch is thrown. [slcasner]

    It is a Y switch, 'either/or', 2 pole (of course), ahead of the main breaker providing two choices: GRID or GENSET so '2 pole double throw'.

    This would provide full isolation between grid and genset since the two are logically isolated from each other. The grid sees this the same as if you simply threw your main disconnect from ON to OFF but instead you switched the house over to GENSET to enjoy off-grid power.

    Practically you would install this in its own box ahead of your service panel and the amperage/flashover rating would at least equal that of the main breaker.
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  4. slcasner

    slcasner Active Member

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    No, you don't need to draw a picture for me, I understand it well. I have a similar switch that is part of my home solar PV system.

    When using a GENSET as you describe, the GENSET is not connected to anything when the Y switch is in the normal position so even if it were running there would be no power sent to the grid. When power fails, the switch is thrown (manually or automatically) to disconnect some or all of the home circuits from the grid and connect them to the GENSET, and then the GENSET is started. There is no possibility for the GENSET to send power to the grid.

    The equivalent scenario for V2G would be that the car is connected to a socket that is not connected to anything when the grid is up and the switch is in the normal position. That's not too useful if you want to be able to charge the car at home.

    On the other hand, if the car is hooked to an active charging outlet when the switch is in the normal position, and if the car is capable of sending power back into the charger but there is no anti-islanding mechanism, I would be surprised if that was not a code violation in WA & WY as well. The specifications for these protections in home PV system inverters come from the IEEE. (And yes, I did see your snarky denigration of CA that appears to have been edited out.)
     
  5. wycolo

    wycolo Active Member

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    > and if the car is capable of sending power back into the charger but there is no anti-islanding mechanism, [slcasner]

    Off into the ozone. (??)

    Watched a UK review of the new Honda EV, whose nose reminds of the International Scout, and who sports a 220vac outlet right there on the dash that could be handy to run into your house during a power outage. Has enough umph to run a few lights and entertainments, but better kill the water heater, range and fridge. We could hook up a similar sized inverter in our Teslas (~1.5kw) to provide emergency domestic support thru my aforementioned Y-switch. Then when the outage occurred it would only take 5 minutes or so to settle back to a semblance of normalcy. The Honda's plug on the dash is something I've not seen before - sort of a built in 'unlimited' Lithium Power Box - with luck now all EVs will feature these.
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  6. slcasner

    slcasner Active Member

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    Yes, that would work fine. The difference between the scenario you describe and the constraints I was explaining is that a separate connection from the car to a dedicated power input socket on the Y switch would be required. It seems unlikely that automakers would implement that connection at the 5kW level, though. And users would be unlikely to hook up that second cable every time the car is parked in the garage, so when the grid goes down some minutes would elapse before power to the critical circuits was restored.

    For a V2G implementation where power goes both ways through the charging cable, the wires would already be large enough for 5KW or more, and for at least some people the regular practice would be to always have the car connected to the charger when garaged. With appropriate equipment on the home side and more advanced communication to the car the switchover could be instantaneous when the grid goes down. In addition, there are several groups studying the possibility of using all the car batteries for grid regulation on an ongoing basis, that is, balancing out the short-term supply/demand differences to keep the grid voltage and frequency steady. That application does not involve transferring a significant amount of energy, just sending power back and forth on a minute-by-minute timescale.
     
  7. PV-EV

    PV-EV Member

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    You guys are killing me with this “Y” switch. It’s called a double throw switch. Number of poles depends on application, ie double pole or triple pole.
     
  8. gregd

    gregd Active Member

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    Actually, I believe the particular variant for home use is called a Transfer Switch. There are versions (sizes) that will do the entire house (main panel), or just a portion (critical circuits, partitioned into a sub-panel). Some even can be configured per-circuit for mains or backup power.

    I wouldn't mind a system that involves a manual cut-over. Anything needing / benefiting from a UPS (computers, ham radio) is already on one, so there's no panic on lashing up the secondary power source.
     
  9. slcasner

    slcasner Active Member

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    @wycolo's term, not mine.
     
  10. wycolo

    wycolo Active Member

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    Switch would have to properly be 'break before make' to protect line-personnel restoring power with bare hands and/or uninsulated tools. [We appreciate their service!] Most DPDT switches are such but it would be good to test a used switch to be sure: you could use a latching relay to test for any momentary leakage. And as mentioned before this switch must meet or exceed the rating of the main breaker that it will be mated to.

    But don't try any of my hairbrained schemes, ever, unless you carefully weigh the alternatives. Especially if you see being evicted or repossessed in the future. This transfer switch can be readily removed and the service cable connected back to the main panel easily since the cable itself did not have to be modified, first rule: do no harm.

    In this case building an off-grid solar system with battery backup is so cheap today and would solve the problem nicely. Why anyone would install a solar/battery home system and still be connected to the grid is mind boggling, but Tesla is doing this every day. All for the government handouts (we are led to believe) but off-grid is cheaper and free of public utility politics. Hooking up a proper transfer switch for your house would be a useful first step if you eventually went full-solar.
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