Most cost effective way to mount this?

ZebraStripes
ZebraStripes Registered Users Posts: 25 ✭✭
I have a flat cement roof in Puerto Rico. I have a large open space for my panels to go into, but in order to make my panels fit, I need to install them in landscape orientation. The problem I have is that I know nothing about solar mounting so I don't really know where to begin. I am attaching a photo of my proposed panel layout. These are going to be Longi LR6-72PH-360M panels, and down on the photo is south. From what I understand, I am basically looking at each of those 9 rows being on their own little assemblies. Is that right? IE each row will have 8 long legs, 8 short legs, and two rails? If so, that's going to get very expensive very quickly. But if that's the way I should go with this, it's what I'll do.

Second question is: Do I need to space these rows out? If so, they may not fit anymore once I've done that, depending on how much space they require.

Third question/issue is: I have a weatherhead sticking up in this location, and I have to keep that penetration there. However, I can move the actual weatherhead elsewhere, if that's possible (IE move the weatherhead outside the array, then just conduit it to the pipe that's going through the roof, allowing me to cut it down considerably) but as this is a flat roof, I need to figure out a water tight way to do that, or I'm going to end up with water in the house.

Any advice you have is much appreciated.



Comments

  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    If this is to scale and you don't have fire codes requiring setbacks it looks like you could remove 4 panels and put 3 in portrait on the left and one in portrait on the right. The higher the tilt, the farther the space required to avoid shadowing. You're in a low enough latitude that a minimal pitch would probably work fine. Your mounting structure needs to be able to withstand high wind so I think a ballasted mount might not work for you. that being said I haven't a clue what to recommend for a flat concrete roof mount. Very likely you'll get a member here with some experience  with your kind of roof.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    At 18°N latitude tilt them south just enough to allow water to run off, I would be inclined to build one large steel wedge shaped truss rack anchored securely into the concrete roof, this would eliminate spacing requirements. Building it extremely strong would be a prerequisite given the  frequency of hurricanes in your area.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
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  • ZebraStripes
    ZebraStripes Registered Users Posts: 25 ✭✭
    Yeah the standard tilt here is 10 degrees. I'm just trying to figure out some sort of mount that doesn't involve 9 individual assemblies, which requires spacing , like you said... 
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    One possibility may be to (eg) move the northern 5 rows a bit to the west, and the southern 4 rows to the east, then tilt one array slightly east and the other to the west.  This would reduce noon current a bit, but this would be offset by a bit better early and late hours production.  This would use rails running north/south, contiguous for each array.

    Each array would have a separate charge controller, and a bit of a gap may be needed between the two arrays to avoid shading the north array from the high point of the south array.

    I used boots something like this for conduit penetrations through my (membrane over wood framed) flat roof:
    https://www.menards.com/main/building-materials/roofing-soffits-gutters/metal-flashing/dektite-reg-1-4-5-metal-roof-vent-pipe-flashing/df103g2r/p-1518593413539-c-5810.htm?tid=7704959040800782674&ipos=14
    Off-grid.  
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    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    Less than 10% will allow water to pool at the low point of the panels. This causes mud to build up and a type of either etching or calcification on the glass. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    In PR, there may also be salt spray/fog to consider as well.  That stuff seems to build up pretty quickly in some climates.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    "Less than 10% will allow water to pool at the low point of the panels. This causes mud to build up and a type of either etching or calcification on the glass.  "

    sounds like you learned this from experience?  Hmm, now I have to rethink my flat pergola solar panel array. I  really do not think I will be climbing up there and washing it off regularly. Just being realilistic

  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    many cement roofs have a knee high wall around the perimeter. if you can bolt steel square beams onto that a few inches high 9 of them would work great for a slight tilt
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    if you posted better photos of your actual roof it would help, a gray blob could be many things!
  • ZebraStripes
    ZebraStripes Registered Users Posts: 25 ✭✭
    Fair point! This is the roof area where I intend to mount the panels. That AC condenser is moving, as is my 4G antenna bucket. The weatherhead is staying though, so I need to get above it somehow. The knee wall idea is a good one, but as you can see, I don't have that on the left side, only on the right.
  • paulcheung
    paulcheung Registered Users Posts: 56 ✭✭
    That water drum going to give some shade issue. you might need to move it behind the AC condensing unit.
    XW6848+ Magnum 4448PAE (Backup) 7800 watts total mixed Panels, 370 AH @48volts battery bank. Grid assist and soon be Tied.
  • ZebraStripes
    ZebraStripes Registered Users Posts: 25 ✭✭
    edited August 2019 #13
    That water drum going to give some shade issue. you might need to move it behind the AC condensing unit.
    Yes it's being relocated to the ground once the panels are up. 
  • billybob9
    billybob9 Registered Users Posts: 141 ✭✭
    WOW , Now that's the way to build a house. Framed with Cinderblocks then cement the roof. A baja style and can be built in two days if you don't mortar the cinderblocks and just stack the blocks add rebar then fill the cells with cement. 4x8 wonder board is great for ceiling but most still use plywood to support the roof when adding the cement.