Dueling Grid Ties

Discussion in 'Solar Power' started by TomT, Jun 14, 2011.

  1. TomT

    TomT WindyNation Engineer

    I have those 2 120 watt panels out in the sun.
    With just one inverter it holds it at 15 volts and about 160 watts.
    With 2 inverters one panel on each it still is at 15 volts and about 160 watts total.
    When I hook the outputs in parallel and it goes to 11 volts and 200 watts. The 2 inverters fight back and forth and when the fan kicks on in one the other takes over most of the output into the grid till the fan kicks off.
    Has anyone else seen this kind of improvement on solar when tying the grid ties in parallel.
     
  2. leamywind1

    leamywind1 WindyNation Engineer

    Hello Tom,
    I have found using the China GTI's it is best to run things in parallel. Wind or solar.
     
  3. TomT

    TomT WindyNation Engineer

    Well I was checking it out yesterday and when it is cloudy out one of the outputs drops to 0 watts for most of the day. But during full sun close to noon they both share the power from the panels. My daily output on a full sunny day went up by .15 kw.
     
  4. Minnesota

    Minnesota WindyNation Engineer

    I have a series of videos testing 2 stacked Chinese GTIs of various types sharing a panel. Some share well and some don't. I've seen a 50/50 sharing, 100/0, and everything in between. I'd recommend 1 per panel and try to run it at about 50% of its true and know capability (such as when tied to a battery). This will allow the MPPT to do its best for that particular panel, just like a true microinverter such as an enphase.
    http://www.youtube.com/user/Fearlessthinker
     
  5. I have a similar improvement. I have two 225 watt solar panels. Two grid tie in parellel 500w(10-30) and a 600w (22-60). On low or cloudy days it uses the 500w till it hits 22v then the 600w kicks in. On a good day I've seen it up to 300w return, but if I disconnect the 500w I get less output(200w). I just started messing with this solar panel collection. This time of year(feb 5). I just wondering if it will increase during the summer.
     
  6. Minnesota

    Minnesota WindyNation Engineer

    Ken, I gave up on parallel GTIs for solar. If you go 1:1 with a 22V GTI you'll do very well. 1 panel to 1 GTI.
     
  7. I've got 4 (600w 22-60) and 8 solar panels(225w ea). For now I have to parallel two panels to one grid tie. Can't use the 500w by itself on the 225 panel the voltage goes to 29+dcv and then the red light flashes. I just thru them together cause it loads it down to 24-28 volts and they work and they throw an extra 100watts on the grid tie off the two panels. Does spin the meter can backwards some. Occasionally they'll bump 30 volts and the 500 go off line waiting for the volts to come down. Just got 2 sets working(4 panels). Just a newbee ordering the wrong parts should have orded 8 600s.
     
  8. TomT

    TomT WindyNation Engineer

    Are those 10.8-30 volt GTIs? By what you are saying it sounds like it.
     
  9. The 500watt gti is 10.-30....the 600 watt 22-60 volt gti. I observed today that I had a total output of 314 watts off the two paralleled panels(225w ea). The 600 watt gti metered 216watts and the 500watt gti produced 98 watts. The dc input was 22v 15.5a that's around 330w. I disconnected the 500 w and my output went down to 208 the dc input went up in voltage (26v) down in amps(8a). I'm stuck with this configuration but the output is impressive.

    my gti config.jpg
     
  10. With this configuration how many watts am I suppose to produce?
    The panels are 225 each.
    Today's highest was 22.5vdc @ 18amps that = 405watts. Do the watt values add together to total a possible 450watts?
    I thought they would just max out at 225watts. I need a refresh on ohms law or physical law.
     
  11. TomT

    TomT WindyNation Engineer

    Yes they do add together and so do the losses.
    ----
    I have two 120 watt in parallel they average together is 145-160 Watt total on an average day at high noon.
    On a cold absolutely clear sky at high noon I get about 180 watts.
    When it is partly cloudy on a cold day in between the clouds when it peeks out I have hit 210 watts but only for about a minute then it drops down.
     

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