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PowerWall 2 Interface with a Generator

Discussion in 'Tesla Energy' started by shs1, Aug 1, 2017.

  1. shs1

    shs1 Member

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    We have a grid-tied all electric home plus an MS, and hopefully soon a 3, powered by 11.4 kW of solar PV, and during power failures, a Kohler 18 kW propane generator. In the next few days we be getting a PW2, and likely soon thereafter, a 2nd one.

    The question is how the PW2 gateway interfaces with the generator. I am familiar with how the Sunny Island works during a power failure to fire up the generator if either the battery bank needs charging or the demand in the house exceeds the battery backup capacity in kWs, as would likely be the case with the PW2s when the cars are charging.

    I have been assured by my installers that the PW2 gateway will also use the generator in an intelligent way, but have seen no evidence so far that an interface exists. The only thing that is needed for control of the Kohler generator is a contact closure; I currently I have a line running to the house and a switch there so that I can turn the generator off during periods of low usage to save propane. While I am certain Tesla must have considered this need and has designed the gateway appropriately, it would be nice to hear from anyone with direct knowledge of this capability.
     
  2. pilotSteve

    pilotSteve Member

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    I would like to know the answer to this as well. We have a 20kW Kohler nat gas gen with a transfer switch currently installed and would like to understand how to interface that with a PW and solar.
     
  3. dhu1

    dhu1 Member

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    No answer yet. I put in an order for a PW2. The site surveyor came out and took a look. They said their designers are still figuring out how to interface with my generac transfer switch. It has been a month already--the latest update was that it was with their lead engineer to figure out a solution. will update once I hear more.
     
    • Like x 1
  4. miimura

    miimura Active Member

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    If I had to guess, I would say that they would put their transfer switch inside the Generac one so that the generator would look more like the grid when it is turned on. This will give them time to sync to it just like they do when they reconnect to the actual grid after an outage. The key point would be to keep the Generac from starting as soon as the grid failed, but instead start when the PowerWall wants it to.
     
  5. shs1

    shs1 Member

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    As to keeping the generator from starting when the grid fails, that is pretty easy with my Kohler generator at least, as when the transfer switch detects a power failure, it closes a contact and returns a 12V start signal to the generator. This start signal can be broken by an open contact closure or simple switch inserted in the signal path. In my case, I have routed that start signal to a switch in my house and back to the generator and thus can turn the generator off when it is not needed to save propane during a power failure. It is certainly possible to automate this control via a WiFi controlled contact closure device such as the Wemo Maker (silly name, smart device).

    Ideally, we can find some logic signal, TTL or contact closure, on the gateway or PowerWall that indicates that the PW is in discharge mode and use that logic to kill the generator when it is not needed. There also seems to be some concern about the ability of the PW to sync with the generator so preventing simultaneous generator and PW discharge might also be a good idea from that standpoint as well.

    The really surprising thing is that Tesla has apparently not worked this all out, or at least isn't saying, but seems to allow customers and local installers to figure these things out for themselves. Tesla seems to feel that generators are not really necessary, but in our case, we have been without power for a week at a time during and after a winter storm, heat the house with a geothermal heat pump and need to charge our Tesla(s). I don’t think it is practical to rely on solar and battery storage only in this case. Plus we already own the generator! Of course charging the car from a generator is a whole different subject.
     
  6. dhu1

    dhu1 Member

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    Got a call today. It seems like they have figured a solution, but only want to pilot it with a few people before they roll out more broadly. Apparently they figured out how to have the PW2 trigger first before interacting with generator transfer switch. Will keep posted as I learn more from them about the process.
     
  7. CarrollPHensel

    CarrollPHensel New Member

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    Have you got anything else to know about the process? My sister encountered the same problem a fews days ago. They decided to consult a generator repair service NJ professionals so that they can immediately find a solution for their problem.
     
  8. Atebit

    Atebit Member

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    : popcorn on this as I have pretty much the same setup as the OP (right down to the geothermal heat).

    My PV installer originally proposed what they called an off-grid system (i.e. including a battery), but I opted out of that and just went with a PV array + generator. One of the reasons was I didn't get the impression that they had a handle on the OP's scenario, which surprised me because they also do stand-alone diesel generator projects as well. Their off-grid design included Sunny Islands, but again it seemed like their designer was only taking advantage of their basic functionality and didn't "get" what I was trying to acheive.

    I was hoping that Tesla had this sorted with the PW by now. But if they went into this being generator-adverse, I can see why it's taking time. The big company I work for also likes to think "it knows best" when entering brand new markets, then often has to go back to the drawing board after customers feed back how things really are in their industry.
     
  9. dhu1

    dhu1 Member

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    apparently the pilot program is only open to 10 customers. They want to handhold the customers through the entire process to make all goes well. lots of caveats during the invitation saying that they expect issues, but will do everything in their power to ensure smooth installation. I signed the contract and they are pulling the permits now with my city
     
  10. Atebit

    Atebit Member

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    So are you # 10?
     
  11. dhu1

    dhu1 Member

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    Not sure. The energy advisor just said I was one of ten
     
  12. shs1

    shs1 Member

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    I wish I was one of the 10. My PW2 will be delivered this week and my local installer and Tesla have agreed to a installation where a manual transfer switch will be used to isolate the generator from the PW2, solar and the grid. This means no charging the PW2 from the generator or use of the generator with the PW when more power is needed than the PW2 can provide. We both recognize or hope that this is a temporary setup and when an official and hopefully more fully functional generator interface is available, we will rearrange/ rewire things to the new official setup. Hate to go through the install twice and have a manual transfer switch that will now be redundant, but that seems to be the way it is.

    dhu1, can you give me any clues as to the functionality provided by the pilot generator installation scheme?
     
  13. dhu1

    dhu1 Member

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    They way it was explained to me was that they would tesla's transfer switch ahead of my generators. Hence, powerwall will be used as the primary backup and when that is depleted, then the generator would kick in. The generator would not charge the powerwall--it will only be used for backup to the powerwall. The powerwall will have all the normal functionality with respect to its interaction with the grid (tou shifting when the new software comes out). Hope that helps
     
  14. shs1

    shs1 Member

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    dhu1, Thanks for the reply. Sounds similar to the setup I was/am getting. The only difference may be whether the switchover from solar/PW2 to the generator and back is manual in my case (long walk out to the shed), or automatic in your case?
     
  15. dhu1

    dhu1 Member

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  16. fresnoboy

    fresnoboy Member

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    Does the powerwall or gateway have an API that can tell it what to do? There is a tragically low amount of information available on the control of the system, and I think if there was an API we could build solutions that would enable all sort of the configurations that Tesla itself is not yet supporting.

    thank you
    mike
     
  17. Kbra

    Kbra Member

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    Im jealous you are actually getting your Powerwalls installed. Im still waiting on the one I won almost a year ago. Im hoping to be able to back feed to my powerwall via a mobile generator and a 220v outlet. Any insight if this might work when isolated from the grid? I want a way to recharge my Powerwall without solar when the grid is down.
     
  18. dhu1

    dhu1 Member

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    Finally got my permit approved by my city. Tesla coming to install next tuesday/wednesday. Installer mentioned that TOU /powershifting feature in app is a few weeks away from being provided in the app. Will report back after the install
     
    • Informative x 1
  19. Kbra

    Kbra Member

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    Whos the installer? Solarcity?
     
  20. dhu1

    dhu1 Member

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    Tesla energy, aka Solarcity
     

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