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Why Grid-Tie?

Discussion in 'Home Power and Microgeneration' started by Jimes, Jul 2, 2006.

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  1. Jimes

    Jimes Guest

    Reading the posts I get the impression that Grid-Tie systems are used pretty
    much only when one wants to sell power back to the grid. I've seen very
    little about having a grid-tied system as a backup. When my batteries are
    flat and I've not seen the sun for a week, then I can at least still get
    power from the grid (without manual intervention). That's the advantage of
    grid-tie for me.

    The other angle is that I could design my system at some reasonable
    capacity, and then draw on the grid only when I have a peak demand.

    Am I misunderstanding something?

  2. This is really where they shine, the grid becomes your battery, and
    saves you a ton of money. While you can have a grid-tied system with
    battery backup, it's quite a bit more expensive than grid-tie without
  3. Jim Baber

    Jim Baber Guest

    JIm Baber replies:
    That is a very minor reason, and seldom practical in the United States.

    1. Best reason I think is to shift your usage pattern from very
    expensive heavy user surcharged rates to lower rates. In some
    cases, this may be all you want or need to do.
    2. Reduce the impact of future rate increases. A good idea for
    retirees, to help with planning your retirement funds.
    3. Feel good about helping the environment and the reduction of
    pollution's impacts for you and your heirs.
    4. No batteries are necessary. Reduces the overall cost of the
    system, but does prevent the PV system from working as a full
    backup to a failed grid
    Grid-tied Solar PV systems are NOT backups for regular grid-tied utility
    power, UNLESS, they are expressly designed to serve that function. To
    do that backup function, they need several otherwise unnecessary components.

    1. Sufficient battery capacity to provide the ampere hour capacity to
    support the power load they are intended to support for the length
    of time the power will be needed.
    2. Inverter / charge controller that will maintain the storage
    batteries in an optimal fashion, they are too expensive to
    mistreat like we do our automotive batteries.
    3. Automatic power line isolation is legally required to isolate any
    backed up circuits from the grid when the grid is down (anti
    islanding). This safety based law / code requirement is true for
    generator backups as well.
    That's OK and reasonable, but a small to medium sized generator might be
    another idea to serve as a boost under these conditions, and might avoid
    minimum charges from your utility.
    Not really, I am producing more than I need, last year I lost a credit
    of $330 to my grid utility at my annual trueup June 14th. I plan to use
    this kind of surplus in the near future in a PHEV (Plugin Hybrid
    Electric Vehicle) to offset some of the currently obscene gasoline
    prices. That $330 utility credit would have moved a CalCars Toyota Prius
    PHEV conversion 13,200 miles. I want one!

    Jim Baber
    1350 W Mesa Ave.
    Fresno CA, 93711
    (559) 435-9068
    (559) 905-2204 (Verizon IN cellphone (to other Verizon IN accounts))
    See 10kW grid tied solar system at ""
    See solar system production data at ""
  4. Guest


    You are thinking on correct lines. Thats how exactly I desinged my system, I
    use my own generated power first and if needed grid tie kick in to charge
    the battery incase no solar or wind gene power available. So far workin fine
    with me.

    GUYS: WATCH OUT FOR GRAHAM ASSHIOLE......... he has the title of
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