A big stupid question for the people here

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henry1
henry1 Solar Expert Posts: 51 ✭✭✭✭
in Grid Tie and Grid Interactive Systems #1
Here is the question for the people here

Can i have a dual system set up with both a grid & off grid system .

One of the ideas is to charge the battery bank with the local power company line coming into the place and when the bank is fully charge shut off the power to the bank and run the place off the bank with solar and wind as back up when the grid is down because of bad weather or there is lot's of sunshine to recharge the battery bank

Using a income juction box switch system to switch off the main income power line to the place and use the off grid side of the set up .

Can it be done and is it worth it .The idea is to have the place run off the bank and when it need to recharge the bank with grid power or solar panel set up as need

The idea of the grid tied unit is more for the winter time when the solar sun cycle is not as good as it in the summer time in the area of Az where i'm at
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: A big stupid question for the people here

    This is actually a very popular question. It gets asked about once a week in one form or another! :D

    Can you do it? Yes. In fact there's more than one way.
    Is it practical? For occasional power outages, no.

    The reasons being that you have to invest in a battery bank and inverter capable of handling the emergency power need as well as some method (none of which are cheap or easy) of utilizing a grid-tie array for recharging (there's quite a Voltage compatibility issue there). All that equipment sits idle and returns you nothing while the grid is up. Worse, the batteries are going to deteriorate whether or not they are used; it's just a matter of how fast.
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  • henry1
    henry1 Solar Expert Posts: 51 ✭✭✭✭
    #3
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    Re: A big stupid question for the people here

    That why i'm asking the question here before i go off and spend the money on the project
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: A big stupid question for the people here

    The simplest way of doing GT with battery back-up is to use a "hybrid" inverter like the Xantrex XW or Outback Radian. One (or more) of these could be all or part of the GT system. You could also use one in conjunction with standard GT inverters.

    Another way is to use the SMA Sunny Island with conventional GT inverters. It's made to synch with their AC output (works best with other SMA units) and allow the GT system to charge batteries and provide load power. The XW can perform similarly. I'm not sure about the Radian, as it is new.

    More complicated methods involve re-wiring the GT array to feed a charge controller during power outages; the batteries being kept up by an inverter-charger or stand-alone charger when utility power is available.

    There is also the Xantrex XW 80MPPT-600, which is designed to accept the high DC Voltage of central GT inverter arrays and use it to charge 24 or 48 Volt battery banks.

    None of this is cheap, so you have to evaluate your essential emergency power needs very carefully if you want to include this function in your system.
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  • TnAndy
    TnAndy Solar Expert Posts: 249 ✭✭
    #5
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    Re: A big stupid question for the people here

    Henry,

    An inverter like the Outback GTFX series will do exactly what you're looking for. Normally, it keeps your batteries trickle charged, and all excess is sold back to the grid.

    When the grid goes down, the grid tie contacts open, and another set close, diverting batter/solar produced power to a transfer switch ( either automatic or manual ) that routes the power to your house.

    This is how I have my system set up.
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