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  1. #381
    Super Star Member
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    Northern Fingerlakes region of NY, USA
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    Kubota L3830GST, B7500HST, BX2660

    Default Re: Grid-tied solar

    Quote Originally Posted by dave1949 View Post
    It should also be possible to make the inverters believe grid power is present by using a pair of automotive-type 120v, 60 hz inverters powered by a 12v battery. The DC cables on the battery could be diode protected, at least the battery wouldn't get fried if things aren't working well.
    You would have to have a pair of inverters that could parallel or it would not work well.

    Aaron Z
    A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
    Robert Heinlein, Time Enough for Love

  2. #382
    Elite Member Redneck in training's Avatar
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    South Central Iowa
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    TYM 330 HST with FEL

    Default Re: Grid-tied solar

    The best think is to use inverter that can automatically switch between grid tie or stand alone. It will fail (shut down) only if the demand exceeds available power. Google hybrid solar inverter. In example Off-Grid Inverters.*SMA Australia Pty Ltd

  3. #383
    Super Star Member dave1949's Avatar
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    Industry, Maine
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    New Holland TC40

    Default Re: Grid-tied solar

    Quote Originally Posted by aczlan View Post
    You would have to have a pair of inverters that could parallel or it would not work well.

    Aaron Z
    Yeah, two independently running 60 Hz, 120v inverters are going to cause problems with 220v circuits.

    I was thinking a generator is not really necessary. It can't take that much power for the voltage sensing lines on a couple strings of microinverters. If one of the AC devices being powered by the solar pv is a 12v battery trickle charger, it might be possible to home brew something that works without a generator running.

    Or, buy one of those hybrid inverters that Ladia linked and don't burn down the house.
    "Those were the days my friend, we thought they'd never end ..."
    When there is a huge solar energy spill, it is called a "nice day"!

  4. #384
    Super Star Member dave1949's Avatar
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    Industry, Maine
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    New Holland TC40

    Default Re: Grid-tied solar

    The March, 2013 results.

    Below the model again this month. Like last month, it was down by about 2 sunny days. This month I saw the highest daily output (30.0 AC kWh) since installation. The better days were producing 25-28 AC kWh. The first week of the month was very weak, 49 kWh in seven days.

    My net usage was 489 kWh of which the system produced 462 kWh. To date, I have taken 268 AC kWh more from the grid than supplied to the grid. For a perfect result for my grid-tied arrangements here in Maine, that number would be zero by the end of this July.

    The PVWatts model AC kWh predicted/actual:
    2012
    Aug. 383/460.7
    Sep. 394/480.9
    Oct. 369/378.6
    Nov. 283/400.3
    Dec. 331/297.2
    2013
    Jan. 388/440
    Feb. 412/375
    Mar. 509/462
    Apr. 374/TBD
    May 353/TBD
    Jun. 308/TBD
    Jul. 341/TBD
    "Those were the days my friend, we thought they'd never end ..."
    When there is a huge solar energy spill, it is called a "nice day"!

  5. #385
    Platinum Member TheGoose's Avatar
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    SE Texas

    Default Re: Grid-tied solar

    Great info Dave. At these rates how long do you think the system will payback?
    Kubota L3400 HST with FEL, R1 Tires, 4x4
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  6. #386
    Super Star Member dave1949's Avatar
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    Industry, Maine
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    New Holland TC40

    Default Re: Grid-tied solar

    Quote Originally Posted by TheGoose View Post
    Great info Dave. At these rates how long do you think the system will payback?
    I think the original payback estimate of 17-18 years back in post #3 is holding up. Cumulatively, I am 225 AC kWh's ahead of the model prediction, so I am not too worried about meeting that. When the system is new, and there is no history, the question that really matters is will the system produce what the model says it will, since that is the basis for the payback period. With some history now, I am gaining confidence that the model is in the ballpark.

    As near as I can tell from our mostly useless percentage gauges on the propane tanks (I have two 120 gal tanks), I probably under-estimated the amount of propane that was being used for domestic hot water. If so, that would reduce the payback period some.
    "Those were the days my friend, we thought they'd never end ..."
    When there is a huge solar energy spill, it is called a "nice day"!

  7. #387
    Elite Member Redneck in training's Avatar
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    South Central Iowa
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    TYM 330 HST with FEL

    Default Re: Grid-tied solar

    Quote Originally Posted by dave1949 View Post
    The March, 2013 results.

    Below the model again this month. Like last month, it was down by about 2 sunny days. This month I saw the highest daily output (30.0 AC kWh) since installation. The better days were producing 25-28 AC kWh. The first week of the month was very weak, 49 kWh in seven days.

    My net usage was 489 kWh of which the system produced 462 kWh. To date, I have taken 268 AC kWh more from the grid than supplied to the grid. For a perfect result for my grid-tied arrangements here in Maine, that number would be zero by the end of this July.

    The PVWatts model AC kWh predicted/actual:
    2012
    Aug. 383/460.7
    Sep. 394/480.9
    Oct. 369/378.6
    Nov. 283/400.3
    Dec. 331/297.2
    2013
    Jan. 388/440
    Feb. 412/375
    Mar. 509/462
    Apr. 374/TBD
    May 353/TBD
    Jun. 308/TBD
    Jul. 341/TBD
    My system also didn't reach predicted production.
    predicted/actual
    3420/3160 kWh

  8. #388
    Elite Member Redneck in training's Avatar
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    Nov 2008
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    South Central Iowa
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    TYM 330 HST with FEL

    Default Re: Grid-tied solar

    Here is a different perspective of viewing PV system performance.

    https://enlighten.enphaseenergy.com/...ems/h2eX136588 That is my system.

    https://enlighten.enphaseenergy.com/public_systems Other public access systems. Click on "e" on the map.
    When system view is displayed. Click on "Get a fresh perspective on solar monitoring. Click here to preview" on top of the screen.

  9. #389
    Super Star Member dave1949's Avatar
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    Industry, Maine
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    New Holland TC40

    Default Re: Grid-tied solar

    April is off to a good start. 193 AC kWh for the month as of this morning. That is 51% of the model prediction in 12 days. I will count today in, April 12th, since it is going to be a loser with the storm passing through.
    "Those were the days my friend, we thought they'd never end ..."
    When there is a huge solar energy spill, it is called a "nice day"!

  10. #390
    Elite Member Redneck in training's Avatar
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    South Central Iowa
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    TYM 330 HST with FEL

    Default Re: Grid-tied solar

    I just read few days back that US solar market increased 76% last year.

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