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Powerwall solarpowered off grid

Discussion in 'Tesla Energy' started by JEU, Apr 16, 2017.

  1. JEU

    JEU Member

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    Hi,
    I have a rather primitive cabin in the mountains at 60 degree North. Today its equiped with a very limited 12v solarpowered electrical system.
    I have started to dream about installing a Powerwall 2 to give 230v to the cabin. Is this feasible? What is required from the solar panels to charge the Powerwall? it dosent need to charge more than about 1/5 of the Powerwall each day.
     
    • Helpful x 1
  2. Ampster

    Ampster Member

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    I think the DC buss on the Powerwall runs at around 300 volts. You would need to reconfigure your solar panels to put out 300 volts, buy more panels or find a DC to DC converter.
     
  3. GSP

    GSP Member

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    @JEU

    To buy an off-grid system with a Powerwall, perhaps the best thing is to ask your local Tesla sales people if they can install one for you. It seems natural for them to offer off-grid systems, even if all Tesla has mentioned so far is grid-tied.

    In the meantime, a small, inexpensive, portable system like this can provide AC power for light loads, such as laptop computers. This one has built in Li-ion batteries, and is for North American 120 V loads. I am sure similar systems are available for 230 V European loads.

    Amazon.com : LB1 High Performance PB160 Solar Generator Portable Power Pack for Laptops, iPhones, Tablets, Mobile Devices, Lights, Emergencies, Camping Power Bank with Fast 2.1A USB Power Output (Black) : Patio, Lawn & Garden

    GSP
     
  4. GSP

    GSP Member

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  5. JEU

    JEU Member

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    Thanks for the replies. There are others systems out there as well providing good "powerpacks", but compared to the Powerwall they are very expensive (kWh/$$).

    And since I am waiting for my second Model X I want a Tesla Powerwall :)
     
  6. Ampster

    Ampster Member

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    You will have to ask Tesla if the Powerwall inverter will work off grid. Many grid tie inverters rely on the 60hz signal from the grid in order to operate.
     
  7. JEU

    JEU Member

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    Ok, I'll see if I can find a support-email for the Powerwall :)
     
  8. Tim

    Tim Member

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    #8 Tim, Apr 18, 2017
    Last edited: Apr 18, 2017
    Gsp, Thanks for posting this. This is an amazing little unit. Amazon also sells the 4kwh unit for $3200. With no tax and a 5% prime card discount that's an extremely good price. I dug up the manual.

    http://www.poweroak.solar/uploads/PS4020B-ESS-Manual.pdf

    The operating modes are really interesting. Peak avoid mode looks terrific for load shifting. Wonder what the cycle life is. I think for states like Hawaii where net metering is being curtailed this type of product is a game changer.

    Unfortunately no certifications yet that I can see. Wish the Powerwall had all this. Terrific design.


     
  9. Ampster

    Ampster Member

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    It works out to be just under $1000 per kWhr. I wouldn't even call that a good price. Doesn't the PowerWall come in at about $500 per kWh.
     
  10. Tim

    Tim Member

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    This includes the Pv inverter. Essentially the equivalent of an outback radian or fronius symo - although at a reduced wattage. So, pretty close to Tesla on price per kwh once that is backed out. Pretty complete(and user friendly) solution for anything off grid. While it won't meet code for a grid-tie it's clearly capable of that. Basically, this is the first box that really checked off all the functionality I imagined for a hybrid storage box. I wouldn't be surprised to see Tesla come out with v3 of the Powerwall that incorporated all this functionality too.

     
  11. macpacheco

    macpacheco Member

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    I think this conclusion is misplaced.
    One of the PowerWall I models was precisely marketed as a house/business wide UPS. Ok, so PW V1 didn't come with the inverter, but PW V2 comes with the inverter. It would make little sense if Tesla abandoned the UPS purpose of a PowerWall with V2. Besides... Tesla is selling PWs by leaps and bounds to Australia after there was a string of power problems with one of Australia regions. I'd think those customers are purchasing PW V2 with the requirement it works properly if the grid goes out.
    I don't know for a fact, but it would make very little sense if PW V2 doesn't already have an off grid inverter (or the same inverter can produce its own 60Hz wave and sync with the grid if its up).
    What little knowledge of electronics I have suggests making a grid tie inverter is more complex than producing its own 60Hz wave. The big challenge likely is having an inverter that is hybrid and can migrate between on and off grid when the AC grid power goes up/down.
     
  12. Ampster

    Ampster Member

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    I am not sure what conclusion you are referring to?
    I do agree with you that the challenge is having a hybrid inverter that can migrate between on or off grid. My search for inverters led me to believe that simple sine wave inverters were the cheapest, followed by grid tied inverters and hybrid inverters being the most expensive. I ultimately settled on a hybrid inverter because of the remote scheduling and a few other features. I don't use the grid tie feature at all because I do not want its use to be regulated by my utility. It is installed according to building codes but behind the meter so I can do load shifting and take advantage of arbitrage between charging at low rates and running my household loads when rates are high.
     
  13. Ampster

    Ampster Member

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    #13 Ampster, Apr 18, 2017
    Last edited: Apr 18, 2017
    i bought an Outback Radian 4kW inverter, for $4,000 installed it myself, spent another $2500 on materials and a Nissan Leaf pack. That worked out to be $325 per kilo Watt hour. Even if I had spent $2000 having an electrician install it the cost would have been $425 per kWhr. For a small system that PowerOak my be at a great price point but once you scale up it doesn't appear competitive by the metric of cost per kWhr of storage.
    CORRECTION/ADDITION: Apparently some of these come with Solar Panels so the value may be better than my metric implies.
     
  14. Tim

    Tim Member

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    Ampster,

    Not really arguing about cost. The key innovation the Chinese did was turn all of this into an appliance. Everything that you(and I for that matter) cobbled together is now a box on wheels. It's simpler to setup than a tv, just as easy to buy and nearly as easy to install. Just plug it in and you've got a whole house UPS, the ability to shift load to only use lowest cost TOU rates, and the ability to do grid-assisted solar with no net metering. The only thing the average homeowner would have to pay an electrician to do would be to add a generator transfer switch and sub panel. That's only a couple hours of work and a couple hundred bucks.

    IMO, it changes everything. Just imagine if everyone had to do all the permitting, engineering, and paid installation now required of solar(or the powerwall) just to install a TV or a dryer. The market for those would be tiny. This thing has me imagining grid-assisted solar that is cheap and everywhere. I'm pretty sure that boxes like these are going to transform the way people use electricity in the future.
     
  15. Ampster

    Ampster Member

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    I agree. It is great to see these kind of things hitting the marketplace. Until now the only solutions were lead acid based and the care and feeding of lead acid would scare anyone away.
     
  16. doubleohwhat

    doubleohwhat Supporting Member

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    Now what we really need for solar to take off nation-wide is a federal law that basically tells cities and HOAs to eff off when they try to block solar installations.

    For example, I got approved for panels via my HOA and was getting permits when I was told by the city that they don't allow reflective glass that is not part of a window to be installed on the exterior of a building. The city councilman who pushed that ordinance through got campaign donations from the local electric company. No one is stupid enough to not be able to see what they did there.
     
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  17. Tim

    Tim Member

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    That's some pretty nasty rent seeking and imo pretty obviously violates the dormant commerce clause. I'd probably just install them anyway and then litigate if necessary. I doubt it would come to that, but the intent of the ordinance isn't to prevent solar installation, just to make them so onerous and expensive as to be not worthwhile. I suppose Tesla roof tiles are a pretty good workaround - according to elon they're made of quartz not glass.

    Sorry JEU for hijacking your thread!
     
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  18. doubleohwhat

    doubleohwhat Supporting Member

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    That's the plan (solar tiles). The "textured glass" tiles are neither glass nor reflective like traditional panels.
     
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  19. Ulmo

    Ulmo Active Member

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    I've always wondered if you could tell two PowerWalls that whatever is connected to it is the "grid", and just have the other one be another PowerWall, each "grid"ing each other. Then, occasionally, when they go down, and you need something to "seed" the mystical actual grid, you can just go in there and physically connect the generator, and suddenly both think the "other" is grid-ing, and start working, and you can disconnect the generator. Kind of like a two way siphon.

    Of course, during the day, the solar panels can do whatever PowerWalls usually do with Solar Panels.

    Is the problem that the PowerWalls just want to chase the frequency, and both of them will have some sort of trouble with that? Isn't the solution just to get a small device you plug into the panel taking energy from the panel and pushing it into the grid ever so slightly at the correct crystal controlled frequency? That would let the PowerWalls sort of be nudged toward that point, and they would not go off into self-purgatory. Or does the frequency holder have to have depth?
     
  20. Ulmo

    Ulmo Active Member

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    Can you circumvent it by spraying a nonreflective coating onto them?

    Can you put in some ground mounts in your back yard that no one notices? Just back-feed some wall plug circuit, and call it a day ... Sounds like a seat of the pants type of area anyway.
     

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