Hybrid inverters

NZRR
NZRR Registered Users Posts: 28 ✭✭
Does anyone know if you can set up and operate a grid-tie/battery backup inverter, like the Xantrex XW4548, without batteries? I have several customers that would like to go solar, but don't want or need the batteries at this time, but would like to add them later. Will the XW series inverters operate without batteries?

One way around this would be to buy some cheap 12V batteries and use them just to get the system operating, then replace them with good batteries when the customer is ready.

Any ideas would be helpful. Thanks.

Comments

  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    Re: Hybrid inverters

    Sorry, the XW will not run without batteries. Could install a GT inverter - then add on a sunny island later to achieve a hybrid result. Or could add on a small one likke the Xantrex PowerHub to handle just critical loads. Also, there are just now becoming available high-voltage charge controllers so that you can tap into the GT array and feed your add-on inverter's low voltage battery.
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Hybrid inverters

    From the installation manual:
    The minimum recommended battery bank is 100 Ah. The inverter is designed to operate with batteries and should not be operated without them. Also, do not allow the battery bank to become completely discharged. If the voltage of the battery bank falls below 10 volts, the Xantrex XW Power System will not operate.

    So you could hook up 4 cheap 100 ah batteries in series and call it a day. The cost would be about $300 if you get deep cycle batteries from someplace like Wal-Mart. If your customer can afford a grid-tie PV system they can afford an extra $300.

    However, the XW doesn't come close to the Sunny Boy for GT efficiency. GT efficiency is key - adding an extra 4-5% to a system that will be supplying the grid for 20-25 years makes a big difference. Go with the Sunny Boy now and later you can add an off-grid inverter when they are ready for battery backup.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Hybrid inverters

    I would go with the solution Solarix proposed: get a grid tie inverter, preferably SMA, then they could add a sunny island, or even a Xantrex XW at a later date. Both of them support back feeding a battery bank with frequency control, the only difference is that the sunny island can control this using a variable function, whereas the xantrex has an off-or-on approach.
  • Seven
    Seven Solar Expert Posts: 292 ✭✭
    Re: Hybrid inverters

    Along these lines of thinking, is it possible to build an off grid system and then, later on, go the hybrid route? I am building a system now, slowly, but in the future when my array is big enough I want to tie it to the grid. Is there a way to use a Classic based off grid system and later get just a grid tie inverter? Or will I have to have a hybrid inverter?
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Hybrid inverters

    Probably would have to re-configure the PV array.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Hybrid inverters

    If you are in the 4-6kW Off-Grid inverter range (pretty big)--The XW Hybrid is pretty effective for both off-grid and later Hybrid (GT with off-grid backup).

    Otherwise, if you are just planning on removing the batteries and the Off-Grid inverter, probably not anything cost effective.

    The new Xantrex high voltage MPPT charge controller sounds interesting (if it is available yet). Would allow you to use the same Vmp~400 volts for both a pure GT inverter and the MPPT charge controller. But, again, you have the question of keeping the batteries/emergency power or not...

    Nothing with solar is cheap or easy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Seven
    Seven Solar Expert Posts: 292 ✭✭
    Re: Hybrid inverters

    I would be keeping the batteries. Actually I would replace them with better ones because I am starting with the cheap Costco ones in case I make a mistake or two with them. I am a noob, but I have a plan. Lol
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Hybrid inverters

    So, what would your initial and final system look like?

    Is your initial system worth building around a $3,000 hybrid 4-6kW inverter with at least a 600 AH @ 48 volt battery bank (for 6kW XW True Sine Wave inverter and array with good sized 5-10kW 240 VAC genset?)

    Does having a full Hybrid/Backup Solar system make sense once you have Grid? Or should you strip out the off-grid system (sell on EBay) and get a simple genset (propane/diesel/etc.) for the week or two without power?

    Does your utility even offer Net Metering/Grid Tied connections? Is the billing/service charges worthwhile for GT Solar? High minimum monthly connection fees, low $ per kWH price for power generated, etc.?

    These questions really apply to anyone looking to migrate a system (small to large, off-grid to GT/Hybrid, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Seven
    Seven Solar Expert Posts: 292 ✭✭
    Re: Hybrid inverters

    The initial system will be an off grid design. It is going to be my test system, building as I go. The expensive way.
    I think I have the answer to my question now. The answer is that I have to use a hybrid inverter. I cant add just a GT inverter to my off grid setup and have it work as a hybrid.

    Thanks!
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Hybrid inverters
    Leper wrote: »
    Along these lines of thinking, is it possible to build an off grid system and then, later on, go the hybrid route? I am building a system now, slowly, but in the future when my array is big enough I want to tie it to the grid. Is there a way to use a Classic based off grid system and later get just a grid tie inverter? Or will I have to have a hybrid inverter?

    You could do this with the SMA sunny island and sunny boy GTI inverter. The system will work as a pure off-grid system, then when you want to grid tie you'd just need to add a transfer switch.
    As a pure off-grid system it's more expensive and slightly less efficient than the other options.