grid tie solar panel system

Hi everyone,
I`m new to solar system and i search informations to design a grid tie solar system. I hope you`ll give me lots of information :)
So i design 40Kw grid tie on roof solar system and
i`ll use 252 panels 150W
Pmax = 79V
Imax = 1,9A
Voc = 110V
Isc = 2,1A

and i want to design 3 10Kw and 1 12Kw fronius grid tie inverter. But,
Each inverters have 6 strings inputs which are 600V and 55,5A values.
But, when i wire panels, i fell confused abit.

Question1: Firstly, i wire 5 series and 2 paralels each input of inverters but i found that is wrong because i have to wire them according to Voc not Vmp. Is it right?
if i wire them according to Vmp ( 79V ) my inverter becomes 9000W and i will use 10000W. it is ok for me but if i wire them according to Voc (110V), my inverter becomes 11088W so i wont use my 10kW inverter.

And can you give me some advices about my project?

Comments

  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: grid tie solar panel system

    Fronius have an online tool that will help you configure the system: http://www.fronius.com/cps/rde/xchg/SID-9ABCE344-1B2D678E/fronius_international/hs.xsl/83_28226_ENG_HTML.htm#.UvJN03ddWcc

    You not only have to design for Voc, but temperature corrected Voc so that the 600V limit is not exceeded in very cold weather. The configuration tool should work all this out for you.
  • solar_davesolar_dave Solar Expert Posts: 2,394 ✭✭✭✭
    Re: grid tie solar panel system

    This is a huge grid tie system, have you talked to your utility about it? Usually they limit the residential size to like 10Kw. 252 panels is going to require a huge roof area and there may be restrictions on what areas of the roof can be used. Here the top 3 ft must be clear for the fire department to vent smoke in the case of an attic fire.

    How you back feed that much power is a big restriction as well.
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: grid tie solar panel system

    I agree with the others here--You need to work with your utility and local code folks to make sure that your system will "work" for your area. Do not buy any hardware just yet (avoid those deals on solar panels).

    In my area, more than 10kW of solar panels is a whole different level of regulatory "attention" and potential billing issues.

    I would also look at the politics in your area and with your utility. We may be heading into a time where GT solar opportunities are beginning to become less common.

    Utilities are starting to "hate" the idea of roof top GT Solar and the impact on their bottom line (going "Green" is not cheap).

    In a few places, people have followed the rules, built the GT system, and when it came time to plug in the systems, they were refused (some stories out of Canada--Not sure if I have seen any US stories yet).

    You probably should get a quote from a local installer or two and see what they say. Sometimes installer experience can be a big help with the utilities and AHJ (authorities having jurisdiction).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: grid tie solar panel system
    BB. wrote: »
    Utilities are starting to "hate" the idea of roof top GT Solar and the impact on their bottom line (going "Green" is not cheap).

    In a few places, people have followed the rules, built the GT system, and when it came time to plug in the systems, they were refused (some stories out of Canada--Not sure if I have seen any US stories yet).

    I would also add that higher powers seem to be more difficult. 8kW is often significantly easier than 40kW.
  • mylovermylover Registered Users Posts: 5
    Re: grid tie solar panel system

    Hi everone again,

    you`re right about rules for building solar array on roof. And i search about them, i will contact with local utility in my counrty.

    Stephendv, thank u for the internet web adress. it becomes perfectly usefull for designing. And i used it, i entered my values, i give me some results how many inverters could use etc.i will ask u some questions for that because some points are still darkness for me.

    That`s pdf giving me from fronuis web site.
    http://yadi.sk/d/7417gJJuHRC5M

    Firstly, if you look into FRONIUS IG PLUS 150V-3, it has 6 inputs for strings. i understand forexmaple, i can connect 2 paralel string of 8 solar panels.As a result, i can connect 16 solar panels for one strings and inverter has 6 inputs, i can connect 96 solar panels. Is it my way wrong?

    And If you look into pdf, they say; you will use 3 fronuis inverters and number of modules per string / 21*4. What is 21*4? As i said before, inverter has 6 inputs for strings. Which connection do they tell me to wire solar panels to inveters?

    Thanks for now everyone.
  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    Re: grid tie solar panel system

    4 strings of 21 panels for each inverter x 3 inverters = your 252 panels.
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • mylovermylover Registered Users Posts: 5
    Re: grid tie solar panel system
    SkiDoo55 wrote: »
    4 strings of 21 panels for each inverter x 3 inverters = your 252 panels.

    Hi SkiDoo55, you`re rigth but if 4 strings consist of 21 series panels right? Then, 21 series panel = 21*Voc = 21*110V= 2310V? inverter`s dc input accepts only 600V how that possible? i`m so confused :(
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: grid tie solar panel system
    mylover wrote: »
    Hi SkiDoo55, you`re rigth but if 4 strings consist of 21 series panels right? Then, 21 series panel = 21*Voc = 21*110V= 2310V? inverter`s dc input accepts only 600V how that possible? i`m so confused :(

    Those panels specs given in the first post are not at all suitable for grid tie installation. Nor for much of anything else.
  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    Re: grid tie solar panel system
    Those panels specs given in the first post are not at all suitable for grid tie installation. Nor for much of anything else.
    Didn't really look at panels information just from the sizing PDF he attached. Wonder if it meant 21 strings of 4 in series? Would make more sense. That's what I get reading on IPad. Missed seeing the 110Voc on them. That going to make some very expensive combiner box's.
    as you say there would be better panels for this unless they are getting them almost free. Going to make some electrician installer rich!
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: grid tie solar panel system
    SkiDoo55 wrote: »
    Didn't really look at panels information just from the sizing PDF he attached. Wonder if it meant 21 strings of 4 in series? Would make more sense. That's what I get reading on IPad. Missed seeing the 110Voc on them.

    It would have to be something like that, as you'd need four in series at 79 Volts to get operating Voltage of 316. That would be 600 Watts per string. Twenty-one strings would then be 12,600 Watts, fitting with the desire for a 12kW Fronius. Eighty-four panels total.

    Whereas normally we'd use GT panels with a Vmp of 30 and, say, 250 Watts each allowing a string of 12 to provide 360 Volts and 3kW. Four such strings in parallel makes the 12kW array. Forty-eight panels total.

    The two hundred and fifty-two 150 Watt panels is 37,800 Watts, close to his original 40kW install idea.
  • mylovermylover Registered Users Posts: 5
    Re: grid tie solar panel system

    Thank u friends,

    When i check datasheet of fronius inverter, it says fronius inverter has 6 inputs per strings. I understand that i can connnect 6 strings to inverter right? I add a photo from datasheet.
    Attachment not found.

    So fronius tell me to connect 21*4 panels to one string input to inveter. Can i use 6 inputs per strings?

    but i want to design like that;

    3 fronius 10kW inverter and 1 fronius 6kW inverter and 252 150W solar panels.

    72 solar panels per 10kW inverters and 36 solar panels 6kW inverter.

    i connect 4 series and 3 paralel for one string input to inverter and inverter has 6 strings inputs 6*12= 72 panels and 72*3 inverters = 216 solar panels
    36 solar panels to 6kw inverter, i will connect 3 series and 2 paralels = 6 panels for one string input to inverter = 6*6 inputs = 36 panels.

    So,how about that design?
  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    Re: grid tie solar panel system

    On such a large number of arrays home running the to the inverter is going to be very costly in wire. You need to think of using combiner box with appropriate fuse protection for each string, then run larger gauge wire to inverter. The racking and additional hardware etc for that number of panel for the odd voltage and low powered panels.
    what is your target output voltage. 240 VAC single phase or are you going 208 or 277 VAC 3 phase? First inverters mention where 3 phase 277 VAC. With 3 10KW and 1 6KW changes the end game.
    another question is this going on residential or commercial type of installation? Changes the rules so to speak. And will greatly influence the recommendations given
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • mylovermylover Registered Users Posts: 5
    Re: grid tie solar panel system
    SkiDoo55 wrote: »
    On such a large number of arrays home running the to the inverter is going to be very costly in wire. You need to think of using combiner box with appropriate fuse protection for each string, then run larger gauge wire to inverter. The racking and additional hardware etc for that number of panel for the odd voltage and low powered panels.
    what is your target output voltage. 240 VAC single phase or are you going 208 or 277 VAC 3 phase? First inverters mention where 3 phase 277 VAC. With 3 10KW and 1 6KW changes the end game.
    another question is this going on residential or commercial type of installation? Changes the rules so to speak. And will greatly influence the recommendations given

    My target is to generate 3~NPE 380V grid electricity. Yes, you`re right about using 6Kw inverter. The project is going commercial type of installation. What can i do for decrasing the cost ( wiring, fuses etc.) ? Should i change the solar panel?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: grid tie solar panel system
    mylover wrote: »
    My target is to generate 3~NPE 380V grid electricity. Yes, you`re right about using 6Kw inverter. The project is going commercial type of installation. What can i do for decrasing the cost ( wiring, fuses etc.) ? Should i change the solar panel?

    Am I reading 3-phase 380 Volts? Maybe you better talk to Fronius about meeting that output spec first.

    Decreasing the cost is going to be highly dependent on what you can get for what price. In the USA you'd be buying GT panels at about $1 per Watt. What you can get where you are is going to make a big difference in what you buy.

    As for the wiring, the distance between the array and the inverter will influence your choices there. Fronius makes these inverters with multiple, separate string inputs to accommodate various configurations and yes they expect one 'home run' per string. If you tie multiple strings together at the array then the wire from that to the inverter will be larger. This could be good or bad.

    Frankly for the size/type of system you are proposing you need the services of a professional designer versed in commercial installations.
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