Best mounting rails for Kaneka 60w panels?

I have a Gambrel roof with space that will hold two Kaneka panels to a row, and room for ten rows. The rails would be about 80" long. The first angle of the South facing roof is 22.5 degrees. Our angle is 33 degrees.

What clips, rails, and mounts would you recomend for the mounting on top of a 2yr. old asphalt shingle roof? Would you install them as a fixed mount rails but tilted to the 33 degree angle or let them match the 22.5 degree angle of the roof?

The instruction booklet says not to put more than 5 panels in series, but doesn't address how many in parallel.

http://www.wholesalesolar.com/pdf.folder/module%20pdf%20folder/KanekaInstallation.pdf

With a total of 20 panels, how would you wire them for a FlexMax 80 controller and a new 24v, 880Ah U.S. Battery 440hc battery bank?

I always appreciate all views and insights,
Bill
Bill

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Best mounting rails for Kaneka 60w panels?

    The Kaneka panels are those "high voltage" solar panels with Voc=92 volts--For a typical MPPT charge controller with Vin-max of 150 VDC or so--just the one panel "in series" is it... Two or more, and you have 184+ volts Voc.

    You can put all of the panels in parallel, just install a 3 amp fuse/breaker in each positive leg of the panel before paralleling them all together.

    You will have to review the input ratings of the FM80--It might be (per NEC) 64 amps maximum (80% of 80 amps)... I don't agree with this derating that NEC seems to typically use--but for your system 20 panels is only 30 amps nominal, so you have way more controller than you need...

    Which does beg the question of why an 80 amp output controller?

    Note that this Kaneka panels will only work for a 12 or 24 volt battery bank. The output Vmp voltage is not high enough to reliably charge a 48 volt battery bank.

    The bank + controller needs north of ~60-62 volts input and the panels probably have Vmp (hot day, no wind, worst case conditions) of ~54 volt output. And, as I said above, you cannot run two panels in series with a 150 VDC input max charge controller without causing damage.

    The reason the manual (I am guessing) says you cannot run more than 5 panels in series is because the NEC/NRTL Vmax system rating is 530 Volts (DC? AC?) and therefor would exceed the maximum string voltage rating with 6 panels (6x101 volts at -10C = 606 volt Voc-cold).

    You can run the PV Watts program for your setup with the two different tilt angles... It probably will not make much difference overall (better in summer, worse in winter) and you should just make the structure sound and pleasing to your spouse (if needed).
    "Station Identification"
    "City:","Fort_Worth"
    "State:","Texas"
    "Lat (deg N):", 32.83
    "Long (deg W):", 97.05
    "Elev (m): ", 164
    "PV System Specifications"
    "DC Rating:"," 1.2 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.6 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 22.5"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 9.7 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 3.97, 73, 7.08
    2, 4.52, 75, 7.28
    3, 5.41, 97, 9.41
    4, 6.09, 104, 10.09
    5, 6.32, 109, 10.57
    6, 6.67, 108, 10.48
    7, 6.77, 111, 10.77
    8, 6.50, 107, 10.38
    9, 5.78, 93, 9.02
    10, 5.30, 92, 8.92
    11, 4.11, 72, 6.98
    12, 3.74, 68, 6.60
    "Year", 5.44, 1108, 107.48
    "Station Identification"
    "City:","Fort_Worth"
    "State:","Texas"
    "Lat (deg N):", 32.83
    "Long (deg W):", 97.05
    "Elev (m): ", 164
    "PV System Specifications"
    "DC Rating:"," 1.2 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.6 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 32.9"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 9.7 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 4.32, 80, 7.76
    2, 4.77, 79, 7.66
    3, 5.50, 98, 9.51
    4, 5.98, 102, 9.89
    5, 6.02, 104, 10.09
    6, 6.25, 101, 9.80
    7, 6.39, 105, 10.19
    8, 6.31, 103, 9.99
    9, 5.83, 93, 9.02
    10, 5.56, 97, 9.41
    11, 4.43, 78, 7.57
    12, 4.10, 75, 7.28
    "Year", 5.46, 1114, 108.06
    About $0.60 a year difference in power (at $0.10 per kWH).

    Bit more power in summer and a bit less in winter if you keep the panels "flat" to the roof...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Best mounting rails for Kaneka 60w panels?
    BB. wrote: »
    The Kaneka panels are those "high voltage" solar panels with Voc=92 volts--For a typical MPPT charge controller with Vin-max of 150 VDC or so--just the one panel "in series" is it... Two or more, and you have 184+ volts Voc.

    You can put all of the panels in parallel, just install a 3 amp fuse/breaker in each positive leg of the panel before paralleling them all together.

    You will have to review the input ratings of the FM80--It might be (per NEC) 64 amps maximum (80% of 80 amps)... I don't agree with this derating that NEC seems to typically use--but for your system 20 panels is only 30 amps nominal, so you have way more controller than you need...

    Which does beg the question of why an 80 amp output controller?

    Note that this Kaneka panels will only work for a 12 or 24 volt battery bank. The output Vmp voltage is not high enough to reliably charge a 48 volt battery bank.

    The bank + controller needs north of ~60-62 volts input and the panels probably have Vmp (hot day, no wind, worst case conditions) of ~54 volt output. And, as I said above, you cannot run two panels in series with a 150 VDC input max charge controller without causing damage.

    The reason the manual (I am guessing) says you cannot run more than 5 panels in series is because the NEC/NRTL Vmax system rating is 530 Volts (DC? AC?) and therefor would exceed the maximum string voltage rating with 6 panels (6x101 volts at -10C = 606 volt Voc-cold).

    You can run the PV Watts program for your setup with the two different tilt angles... It probably will not make much difference overall (better in summer, worse in winter) and you should just make the structure sound and pleasing to your spouse (if needed).

    About $0.06 a year difference in power (at $0.10 per kWH).

    Bit more power in summer and a bit less in winter if you keep the panels "flat" to the roof...

    -Bill

    I took a $60 hit for shipping and insurance to return the Outback GVFX 3648 to get the GVFX 3524, so I could use the Kaneka panels for an Off Grid system. For LESS the price of four Kyocera 135w panels (540w) shipped, I bought 1,200 watts of Kaneka panels AND the Outback MPPT 80 amp controller shipped. Grid tie may be a future option with this inverter, but not until I see a lot more professional behavior and a lot changes with this Co-Op I've been a customer with since 1977....

    Using a 48v battery bank, I'd have to use the Midnite 250 Classic controller for series strings of the Kaneka panels, and there were more and more issues surfacing. That controller was going to be over $700+, whenever it finally gets to market for the Average Joe like me, and then the high voltage combiner boxes and high voltage breakers kept pushing the cost higher and higher.

    Since I have the Outback Mate and inverter, and they have only two sizes of MPPT controllers, I was thinking that $60 difference between the 60amp and the 80 amp controller was worth having the larger model when you realize that with the solar tax credit, it's really only a $38 difference... Even though the ad for the Kaneka panels was pulled before New Years Day, if I were to find more of the free shipping/$40.00 cost for the panels, it would carry any additional wattage.

    Any insight and input about what to use for the roof mounting framework? Weight on this roof is not an issue beginning with 5/8" radiant barrier decking. The Gambrel roof rafters allow for a full 8' ceiling on the second floor, and not only are they on 16" centers, but they are 2"x 10" I-Beams.

    If you could show me how to post pictures, I'll post some showing it while I had it in the framing bones and as I progress with this project.
    Bill
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Best mounting rails for Kaneka 60w panels?

    I made a typo--That was $0.60 per year cost difference--but if you need the off-grid power during the winter, then tilting the panels up a bit does not hurt.

    Looking the total cost is always something to keep in mind--sounds like you are doing well there.

    I don't have anything to say about the mounting framework--that is not really something I am that familiar with.

    To post pictures, you can upload them using the "Paper Clip" on the top line of the message posting box. Just click and point the where the picture is on your computer.

    Try to limit them to roughly 600 pixels wide--Bigger ones tend to make the post too wide for reading on standard size screens.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Best mounting rails for Kaneka 60w panels?
    BB. wrote: »
    I made a typo--That was $0.60 per year cost difference--but if you need the off-grid power during the winter, then tilting the panels up a bit does not hurt.

    Looking the total cost is always something to keep in mind--sounds like you are doing well there.

    I don't have anything to say about the mounting framework--that is not really something I am that familiar with.

    To post pictures, you can upload them using the "Paper Clip" on the top line of the message posting box. Just click and point the where the picture is on your computer.

    Try to limit them to roughly 600 pixels wide--Bigger ones tend to make the post too wide for reading on standard size screens.

    -Bill

    Thanks for your comments and input is appreciated, and posting the pics went great. I've built this 16'x32' storage/hobby cabin in the back yard and added the porch that faces North. The rear side of the Gambrel roof is almost perfectly pointing to Solar South and is built to carry any load put on it....

    The picture of the pallet with the first 10 panels shows a unique cone to remind the motor freight fellows not to stack anything on top. The second shipment came in fine, but didn't have the "reminder", so the outside seemed scary and scarred when I signed for it...

    Thanks again for your comments,
    Bill
    Bill
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Best mounting rails for Kaneka 60w panels?

    Here are two 10-panel shipments that arrived between Christmas and New Years and the second week of January. 1,200 watts on a 24v system and an Outback FlexMax controller.

    Suggestions for rails and installation on a asphalt shingle roof?

    Thanks
    Bill