Grid Tie Inverter Question

If the power grid experiences a blackout does my solar grid tie system blackout too? thanks for your help.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    Re: Grid Tie Inverter Question

    A pure Grid Tie Inverter system is the least expensive to install, least expensive to maintain, and the most cost effective method to produce solar electric power.

    However, you are correct, its main drawback is that it only works when your Electric Utility lines are working.

    You can certainly install full off-grid systems (battery/inverter/solar panels/charge controller/generator) for remote sites. And there are hybrid systems that do grid tie for normal operation, but fail over to off-grid operation (sort of like a giant UPS).

    Both of these options require batteries--which is where the additional costs really come in (expensive to buy, have to keep clean and watered--if flooded cell, and replace very 5-15 years or so)...

    You can make very nice "hybrid" grid tie + off-grid systems... But it is not cheap.

    Xantrex (also sold by our host) makes a very nice "XW" system if you want a large system (4-6 kW of inverter support).

    Depending on where you live--a Grid Tie system can get your power down to $0.25 per kWhour, or less--without state or federal rebates.

    An off-grid system is probably going to cost you $1.00 per kWhr or more (usually no rebates available)...

    I don't know what a hybrid system will cost (per kWhr)--but probably somewhat closer to the $1.00 per kWhr.

    Where do you want to take this discussion?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Grid Tie Inverter Question

    any suggestion of which grid tie inverter should i get? also do i need both an ac and dc disconnect switch?
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    Re: Grid Tie Inverter Question

    Are you planning on installing the system yourself? Generally, the installer makes much of their profits based on the panel/inverter markups--so they usually have a couple inverters and manufacturers they can select from.

    But, this is a little bit backwards to select the inverter first. My two cents would be to suggest that you size the system first, then look at the inverters that will support the system and options you are looking for.

    From what I have seen, in the ~3-5 kW range, the Xantrex GT series look pretty nice--Has the AC/DC switch and does not have any fans (fans are usually the first things to fail).

    Our host stands by their product--so if you end up getting the inverter and panels through your installer--you can still reference back here to see if it is one of Wind-Sun's products and be pretty sure that the product will be reliable and have good support.

    Also, make sure you look at the cost per watt ($/watt) for your system components. You don't want to overspend. Some of the smaller systems (1-2 kW inverters) are pretty expensive. The larger ones usually seem to be more cost efficient).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RoderickRoderick Solar Expert Posts: 253 ✭✭
    Re: Grid Tie Inverter Question
    any suggestion of which grid tie inverter should i get? also do i need both an ac and dc disconnect switch?

    If you are interested in monitoring your system on your own, I'd suggest Xantrex, because their protocol is open, and several people have written software to talk with the inverter. If you pick an inverter brand with a closed protocol, it will be an uphill battle trying to talk to it without buying their proprietary hardware and/or software.

    If you're in the PG&E territory of California, AC disconnect switches are no longer required. Depending on where you live, the requirement for an external AC disconnect may no longer exist, either. If I were installing today, I wouldn't bother with the AC disconnect. The circuit breaker in the service panel can always be used to disconnect the AC if you need to work on the inverter.

    I don't know about the DC disconnect requirement - possibly, it depends on locality. Every install I've seen has included one, though, and I must admit, I've used mine a few times.
  • System2System2 Posts: 6,290 admin
    Re: Grid Tie Inverter Question
    any suggestion of which grid tie inverter should i get? also do i need both an ac and dc disconnect switch?

    FYI, I am in eastern Los Angeles County un-incorporated and the county inspector instisted on both a DC and AC disconnect, and no the AC breakers did not count.
  • mike95490mike95490 Solar Expert Posts: 8,434 ✭✭✭✭✭
    Re: Grid Tie Inverter Question
    jst3751 wrote: »
    FYI, I am in eastern Los Angeles County un-incorporated and the county inspector instisted on both a DC and AC disconnect, and no the AC breakers did not count.

    un-incorporated LA county here, and no DC disconnect required, the Xantrex GT's built-in switch qualified for me. Edison required an AC disconnect so they would not have to scan all my breakers.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 Posts: 6,290 admin
    Re: Grid Tie Inverter Question
    mike90045 wrote: »
    un-incorporated LA county here, and no DC disconnect required, the Xantrex GT's built-in switch qualified for me. Edison required an AC disconnect so they would not have to scan all my breakers.
    (will attach thumbnail photo later)


    I guess I should clarify: DC disconnect was required, but the included one for the SunnyBoy inverters was used and accepted. No seperate DC Disconnect was requried.
  • dlenoxdlenox Solar Expert Posts: 42
    Re: Grid Tie Inverter Question
    Roderick wrote: »
    If you are interested in monitoring your system on your own, I'd suggest Xantrex, because their protocol is open, and several people have written software to talk with the inverter. If you pick an inverter brand with a closed protocol, it will be an uphill battle trying to talk to it without buying their proprietary hardware and/or software.

    Rodrick,

    I have a Xantrex XW-6048, do you have links to the software you referred to? I have been looking and can't find any, if I have to I can do the software but don't want to reinvent the wheel.

    Dan
  • dlenoxdlenox Solar Expert Posts: 42
    Re: Grid Tie Inverter Question

    The Xantrex XW-6048 is what they refer to as a "hybrid", meaning that it can work in grid-tie mode even without the grid present.

    When the grid goes down I do have power - but the inverter also requires the use of a battery bank to be present at all times.

    There is no grid-tie system that can run without the grid without a battery bank so it is a necessary evil.

    Dan
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Grid Tie Inverter Question

    Rodrick was referring to the Xantrex GT series RS232 open protocal, the XW is Xanbus specific.

    Xantrex I believe opened up that as well ( XW Canbus register maps ) , I had no interest in making a SG-View type application as one has to spend 100+ bucks just for the Canbus to USB converter.
  • dlenoxdlenox Solar Expert Posts: 42
    Re: Grid Tie Inverter Question
    Xantrex I believe opened up that as well ( XW Canbus register maps ) , I had no interest in making a SG-View type application as one has to spend 100+ bucks just for the Canbus to USB converter.

    I have no problem in spending 100$ to purchase the interface, not many options here with the Xantrex XW system for logging. If I purchase the Canbus -->USB interface will the software work properly?

    thanks,
    Dan Lenox
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Grid Tie Inverter Question

    What software? there is none for the XW that I know of .. the XW line is low volume which would make it difficult for a 3rd party to do the R&D to make a stand-alone PC program ( no payback )
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