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Grid Tying

Discussion in 'Photovoltaics' started by Brian Graham, Mar 31, 2005.

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  1. Brian Graham

    Brian Graham Guest

    Jim Baber said,The biggest problem I have with my solar PV (grid
    tied) is when the grid is down, so is my solar.
    <<

    I can't say I know much about the setup of these systems, but is this normal?? Do all Grid-Tied systems go AWOL without the grid? If so, when I use PV it certainly won't be tied.
     
  2. Steve Spence

    Steve Spence Guest

  3. Brian Graham

    Brian Graham Guest

    Steve Spence<> March 31, 2005 12:17:14 pm >>>
    If you have no battery bank, then yes, without grid, your grid-tie
    system is useless.
    <<<<

    I didn't note the lack of batteries in the original post, but that would certainly explain it.

    Now the only thing I don't understand is the lack of batteries.. ;-)
     
  4. Steve Spence

    Steve Spence Guest

  5. Windsun

    Windsun Guest

    Then it will cost you 50% more and have 25% less efficiency.
     
  6. Brian Graham

    Brian Graham Guest

    Steve Spence<> March 31, 2005 2:07:56 pm >>>
    Typically, a grid tie system dumps power onto the grid, there is no
    local battery storage. Grid down, lights out. Put in a battery bank, now
    you have an off-grid system with grid sell back ......

    Seems like an expensive way to lower the Hydro bill. I'd rather work towards eliminating it.

    Even if you can't go off-grid completely, you could certainly keep certain circuits up & running when Hydro's out. And isn't that usually the whole point of the matter??
     
  7. Brian Graham

    Brian Graham Guest

    Windsun<> March 31, 2005 2:23:52 pm >>>
    Then it will cost you 50% more and have 25% less efficiency.
    <<

    But you'll have 100% more efficiency when the Hydro is out.
     
  8. Brian Graham

    Brian Graham Guest


    Jim's Reply to Brian:
    without the grid being up. First, the equipment that is NOT grid tied,
    is not acceptable for any inclusion as any part of the California rebate
    plan, so you would have to pay for it separately by yourself.<<<



    Rebate?? In Canada I'm not aware of any government assistance. It sure would be nice! From what I've heard, the rebates in the US are quite substantial.


    rebates is a state administered fund that all privately owned utility
    customers pay into as a percentage fee per kWh used on their bills. <<<


    Don't get me wrong, selling back surplus to further reduce your bills is not bad. But having a solar setup which goes down with the grid...

    batteries and charge controllers for the batteries are more expensive
    than just the grid tied inverters anyway. <<<


    Personally I'd rather not be connected. What's to stop the gov from mandating how much of your supply you have to sell back to them - I mean if they're in a real crunch.. And you could then be left without sufficient power for your own needs.

    some specialized knowledge. <<<


    Absolutely. But all that takes is a bit of reading and planning. Nothing insurmountable.

    Again, to clarify, my initial query was to indicate my confusion with the statement that your solar went out when the grid does. I was wondering if that was always the case with the grid-tie setup. And the answer is no - its the result of a cost-benefit analysis. Best bang for the buck, and all that. Fair enough.
     
  9. Windsun

    Windsun Guest

    And how often does that happen?

    -------------------------------------------------------------------------------
     
  10. circuits up & running when Hydro's out. And isn't that usually the whole
    point of the matter??

    In most places it is too expensive to go off the grid. You will probably
    never compete with grid prices.

    My payback for my small system is about 70-85 years not considering the
    money I spent not making interest. It's mostly a fascinating hobby.
     
  11. normal?? Do all Grid-Tied systems go AWOL without the grid? If so, when I
    use PV it certainly won't be tied.
    would be nice! From what I've heard, the rebates in the US are quite
    substantial.
    not bad. But having a solar setup which goes down with the grid...
    mandating how much of your supply you have to sell back to them - I mean if
    they're in a real crunch.. And you could then be left without sufficient
    power for your own needs.
    statement that your solar went out when the grid does. I was wondering if
    that was always the case with the grid-tie setup. And the answer is no - its
    the result of a cost-benefit analysis. Best bang for the buck, and all that.
    Fair enough.
    Just get a decent inverter. Some have "backed up" power breakers and also
    grid "backfeed" breakers facilties. You choose the circuit in your house you
    want on 24/7 and the ones that are totally grid dependant. when you are not
    using enough from your secure circuits you back feed your service for credit
    on your grid bill.
     
  12. Steve Spence

    Steve Spence Guest

    The only breaker an inverter has is to protect it from overload. You
    have to install and wire distribution panels, or pay someone to do it
    for you.

    Back feeding the grid involves a lot more than just an inverter, it
    usually involves contracts, permits, and safety disconnects. Few
    inverters are designed or approved for grid tie use.

    Our inverter powers everything in the house, with the exception of the
    washer, dryer, and well pump. Those are on a gen only circuit. WE opted
    not to go grid-tie, as the powerlines would have to be extended 1 mile
    at a cost of $15k or so. We really don't have any excess solar, and gen
    output is not allowed on the grid.

    Steve Spence
    Dir., Green Trust
    http://www.green-trust.org

    Contributing Editor
    http://www.off-grid.net
    http://www.rebelwolf.com/essn.html
     
  13. Steve Spence

    Steve Spence Guest

  14. Brian Graham

    Brian Graham Guest

    How often does it have to? Do you not have fire insurance?

    And how often does that happen?

    -------------------------------------------------------------------------------
     
  15. Windsun

    Windsun Guest

    If it is worth anywhere from 5 to 10 thousand dollars to you, losing 25% or
    so of your total solar output from inneficiencies, and increasing overall
    system costs, longterm costs, and maintenance - then sure you are welcome to
    put all the battery based grid tie type systems you want to in.

    Losing power for a few hours is hardly the equivalent of your house burning
    down.
     
  16. Guest

    How so?

    My battery bank isn't really sucking any significant energy. It stays
    topped off 99.9% of the time. It only kicks in (and incurs some
    efficiency loss) when the grid goes down. Oh, okay, and when I do an
    equalization cycle every 6 months.
     
  17. Windsun

    Windsun Guest

    1. Batteries cost money. Batteries have to be replaced. Over 20 years life
    of the system the batteries would probably end up costing you more than the
    solar panels.
    2. Direct grid tie inverters are more efficient than the grid tie with
    battery inverters in feeding max power from the panels to the grid. And you
    also have the additional losses of going from panels to charge controller to
    batteries then to grid AC. From what we have seen in installed systems the
    total loss with batteries is 15 to 25% more than a straight grid tie.
    3. The average power outage in the US for all causes averages less than 6
    hours per year.

    So, it is your choice. We sell batteries also.
     
  18. Some have to be more than that average of 6 hours per year. Each case / zone
    has it's own problems with it own "better" solutions. I think this applies
    in any field of endevour.

    Installers will tend to gravitate toward the best solution for their
    individual politics, climate and regulations. Essentially becoem "experts"
    for their area. These "experts" opinions may not be very compatible online
    where geographical boundaries do not exist sometimes.

    Have a great one. (we gettin'a snow blizzard today)
     
  19. In my location, as I stated, the payback time is 70-85 years without
    considering the interest on the monetary investment I am not getting.

    BTW: You just contradicted yourself very badly. You stated it wasn't
    location dependant and then stated it would have cost you $7500 to get the
    lines and poles installed because of your location.

    Are many of the people in this dyslexic and cannot comprehend simple
    sentences of their own or anybody else?
     
  20. Guest

    You are overstating the case by A LOT.

    I have two dozen T-105 batteries. They cost around $60 apiece,
    including any recycling fee -- that's an investment of under $1,500.

    I've had 'em for 4 years. I run an equalization cycle every 6 months.
    Takes me about an hour of my time, now that I've found the auto-fill
    bottle thingie (most automotive parts stores have 'em). I'm not seeing
    any signs of degradation. I figure they'll last me 10 years, so I'll
    have to put in another $1,500, maybe $2,000 if recycling costs go up,
    before the whole system needs to be replaced.

    I have 32 Kyocera panels. Those puppies cost around $500 apiece.
    That's $16,000 worth.

    I probably paid an extra $3,500 (including the batteries, charge
    controllers, and an inverter/charger/grid-tie-capable system) to have
    that battery bank, perhaps $5,500 over the life cycle of this system.
    For my goals, that was a relatively small cost in order to be able to
    run independent of the grid, if I have to or want to.
    The charge controllers generally don't have anything to do in my system.
    While the grid is up, they're out of the picture entirely. Excess
    power is dumped onto the grid.

    They only have something to do if the grid is down while the sun is up.
    Well, I'd be very surprised if those numbers applied to my system. I've
    got a 3kw system that supplies me with over 14 kwH per day, averaged
    over the course of a year. The panels are not on trackers, and they're
    not even at optimum elevation or azimuth.
     
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