Whoa 12.96KW PV system going on my house soon.

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foosman
foosman Solar Expert Posts: 38 ✭
in Advanced Solar Electric Technical Forum #1
Guys,
I'm about to pull the trigger on a grid tied PV system for my house and looking for any last minute advice. This is a large system, here are the details:

12.96KW of maximum power
72 Solarfun SF 160-24-M(180W) modules
Fronius IG Plus 11.4 inverter

South array (almost due South): 18 modules
East array (almost due East): 54 modules
Configuration is 8 strings of 9 modules. I am located in Austin, TX/

I am getting this for a ridiculous price as the utility company is rebating $4.50/W and Obama is paying 30%. It should pay for itself in 2 years.

I'm wondering your thoughts on:
- Single inverter...single MPPT...seems like 2 inverters would be best for power tracking, but a single inverter is much cheaper. The installer has no concerns over the single Fronius.
- Reasonable (i.e- cheap) way of performance monitoring...should I also include any of the Fronius acquisition cards, etc? I've hear people have written their own SW. I'm looking for advice on if there's anything I should add to the system for this.
- Any other thoughts.

Thanks!
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
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    Re: Whoa 12.96KW PV system going on my house soon.

    i don't know if this will apply to that inverter, but you may find this thread interesting.
    http://forum.solar-electric.com/showthread.php?t=3594&highlight=fronius&page=9
    i also don't remember if the consensus was to go with separate inverters or not when dealing with 2 separate strings, but i'm sure somebody will step in and say.
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  • foosman
    foosman Solar Expert Posts: 38 ✭
    #3
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    Re: Whoa 12.96KW PV system going on my house soon.
    niel wrote: »
    i don't know if this will apply to that inverter, but you may find this thread interesting.
    http://forum.solar-electric.com/showthread.php?t=3594&highlight=fronius&page=9
    i also don't remember if the consensus was to go with separate inverters or not when dealing with 2 separate strings, but i'm sure somebody will step in and say.

    Thanks, I read this thread last night and asked the installer if they'd used any Power-One products. He was intrigued by the dual-MPPT, but had no experience with Power-One. I think they are too new to the US. I also read the Fronius white paper. It makes sense, since the power curves in the data sheets of the panels shows similar voltages at varying light intensity. If the inverter adjusts for the maximum power it should track the best sub-array and the lower output array's optimum voltage should be close. Arrays from the different orientations are in parallel, so there should be no starving.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #4
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    Re: Whoa 12.96KW PV system going on my house soon.

    The Fronius white paper is BS .. they have no field data to back it up and solar panel DO have different VOC/VMP values based on light intensity. To claim 1% difference just shows how little the author understands the technology.

    Stick with either Xantrex or SMA for inverter choices and IMHO stay far away from Fronius
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  • foosman
    foosman Solar Expert Posts: 38 ✭
    #5
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    Re: Whoa 12.96KW PV system going on my house soon.
    Solar Guppy wrote: »
    The Fronius white paper is BS .. they have no field data to back it up and solar panel DO have different VOC/VMP values based on light intensity. To claim 1% difference just shows how little the author understands the technology.

    Stick with either Xantrex or SMA for inverter choices and IMHO stay far away from Fronius

    The efficiency on the Xantrex seems poor (92.5%) wheras the SMA and Fronius are in the 95-96% range. My utility co. rebate is based off the wattage AFTER the inverter efficiency losses. Purchasing a Xantrex would cost ~ $2500 more. Also, the SMA and Xantrex warranties are 5yrs, the Fronius is 10yrs.

    Can you elaborate on why to stay far away from the Fronius?
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #6
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    Re: Whoa 12.96KW PV system going on my house soon.

    http://www.xantrex.com/web/id/172/p/2604/pt/25/product.asp

    95.9%, CEC rated 95.5% for the Xantrex line of GT inverters

    Fronius has always been quirky boxes, I tested a few and had issues with everyone of them.

    Many here have the GT's, I have 14+kw installed running on GT's .. built in PC monitoring ability is nice. SMA is also a top brand

    For GT's an 13kw, I would use 3 GT5.0's .. about 8500 street price and no multi angle roof or orientation issues

    What ever inverter you go with, match the PV wattage to the Inverters maximum, you will have times that the full STC power can be harvested. 11kw is much to small for a 13kw system
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  • foosman
    foosman Solar Expert Posts: 38 ✭
    #7
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    Re: Whoa 12.96KW PV system going on my house soon.
    Solar Guppy wrote: »
    http://www.xantrex.com/web/id/172/p/2604/pt/25/product.asp

    95.9%, CEC rated 95.5% for the Xantrex line of GT inverters

    Fronius has always been quirky boxes, I tested a few and had issues with everyone of them.

    Many here have the GT's, I have 14+kw installed running on GT's .. built in PC monitoring ability is nice. SMA is also a top brand

    For GT's an 13kw, I would use 3 GT5.0's .. about 8500 street price and no multi angle roof or orientation issues

    What ever inverter you go with, match the PV wattage to the Inverters maximum, you will have times that the full STC power can be harvested. 11kw is much to small for a 13kw system

    You are correct, I was looking at the non-GT, the GT series looks nice. My actual system is lower than I thought, it will be: 11.34kW (3.24kW/18 panels South and 8.1kW/45 panels East.) This would require 3 Xantrex inverters...can't say I'm crazy about three inverters. Fronius has a $165 card (Fronius interface card easy) that has an RS232 connection. I plan to use this to connect to a PC over CAT5 for datalogging. I'm curious what SW you are using with your Xantrex inverters. I'm thinking of developing something to auto update a web-page to give pseudo real-time logging.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #8
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    Re: Whoa 12.96KW PV system going on my house soon.

    The GT's are not large or bulky ... You could get by with two 4.0's and a 3.3 about 6200 street price for that.

    The Pictures is my new dual 4kw arrays, I have about 14kw on the roof now and a closeup of what the 3 inverters look like

    Free Software http://www.solar-guppy.com/forum/sg-view-xantrex-gt-gridtie-pc-monintoring-software-t548.html
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  • foosman
    foosman Solar Expert Posts: 38 ✭
    #9
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    Re: Whoa 12.96KW PV system going on my house soon.

    Thanks for the information and pictures. That is terrific!
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  • FL SUN
    FL SUN Solar Expert Posts: 94 ✭✭✭✭
    #10
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    Re: Whoa 12.96KW PV system going on my house soon.

    Informative thread. The built in PC monitoring and convection cooling design of the Xantrex make it very appealing. I am looking forward to incorporating one in our next job.

    SG, that is impressive. I bet you wished more than once that gable end was not on that roof.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #11
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    Re: Whoa 12.96KW PV system going on my house soon.
    FL SUN wrote: »
    Informative thread. The built in PC monitoring and convection cooling design of the Xantrex make it very appealing. I am looking forward to incorporating one in our next job.

    SG, that is impressive. I bet you wished more than once that gable end was not on that roof.

    Yes the cathedral ceiling in the living room isn't ideal for solar ... but I managed 40 of the 200 watt Evergreens, I don't have shading issues as the array is facing 225 degrees ( 45 west of south ) and in our latitude work out fine
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  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    #12
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    Re: Whoa 12.96KW PV system going on my house soon.

    Hey guppy,

    How are those 200 evergreens working so far, I am looking at the sun-205 and i understand suns and evergreens are the same except for the Ul label.

    Cheers...
    Damani
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #13
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    Re: Whoa 12.96KW PV system going on my house soon.

    Best panels I have ever owned performance wise ... I have the arrays tweaked within 2-5 watts of each other at most power levels

    I'm getting about 3700-3800 watts from each array peak right now, even with 80+ degree days .. pushing over 80kWh the last few days on the whole house
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  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    #14
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    Re: Whoa 12.96KW PV system going on my house soon.

    Wow,

    How did you go about "tweating" the panels. Is a matter of checking each and matching the output and putting strings together that closest in power output?

    Cheers...
    Damani
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #15
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    Re: Whoa 12.96KW PV system going on my house soon.
    Dapdan wrote: »
    Wow,

    How did you go about "tweating" the panels. Is a matter of checking each and matching the output and putting strings together that closest in power output?

    Cheers...
    Damani

    Pretty involved ... I use charge controllers in manual mppt mode and check each string I/V/Wattage, I then interleave the two arrays to the controller under test and finally I tweak the home runs ( 2AWG from the switch board/combiners ) to match the wattage closer , for example, I added a 6AWG on the home run of the lower performing DUT to increase the array 15 watts. End result is 2-5 watts from 100-3400 watts measured by a pair of Yokogawa WT130's ( power analyzers )
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  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    #16
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    Re: Whoa 12.96KW PV system going on my house soon.

    Ok gup,

    you basically did this tweaking by controlling your line losses...cool.

    Cheers...
    Damani
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