Roof mounted panels with out the holes.

shiftshift Solar Expert Posts: 48
Out of curiosity (i know.. my mind never stops!) Would it be feasible to build a mount that arches over multiple peaks in effort to hold the panels in place by its own weight rather than having to bolt it down?

I realize this wouldn't be as efficient as a south facing roof, but i'm working with what i got :)

Illustration:
roof-mount

The power wires could then be ran through a hole in the attic vent spinner, conveniently only a few feet away!

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    Re: Roof mounted panels with out the holes.

    Probably not--Panels may weigh around 3 lbs per sq ft and they have to withstand winds on the order of 30-50 lbs per sq foot (some are even rated for static loads upwards of 113 PSF).

    The Solyndra system used round tubes that would make much less of an effective sail vs a flat panel--So they did ballasted racks (one of their selling points.

    Here is a thread where ballasting was discussed:

    Does anyone trust anyone's ballast calculations?


    It appears that for a roof mounted system (all things being equal--which they are not), roughly 150 lbs for a full sized panel (200-250 watts?). That worked out to just under 9 lbs of ballast per square foot.

    If you mount the panel next to the roof (a whole different discussion about panels running hot), then they might do well as long as the wind cannot get under them to pick up the array.

    If this is grid tied--your building department and power company are going to want permits, which in most areas require a professional (civil) engineer to sign off the load calculations.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    This will Not be grid tied. It will be hooked up to 2 deep cycle batteries for now for my outdoor lighting.

    My other idea was doing a mount above my sundeck on the side of the house at a 45degree angle.
    Ideally i would like to avoid making holes in the roof (last resort) the back yard is full of tress so there is few spots that would get shadeless sun for more than an hour or two.


    I was thinking of making a small gap for ventilation under the panels. Since this is more of a project than a necessity im avoiding having to do anything structural.

    Excellent link on ballasting, there is tons of info I would have never though of. IF you could some how force the wind downwards on the panel it would hold it self in place. If the bottom touched the roof and the top had a cap so wind could not get under it... The only issue there is it would hurt panel ventilation.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    A screw or lag bolt is IMHO the only thing to use for anchoring those pricy panels so that they do NOT act like a sail in the wind, however so light they may seem... they can very quickly end up on your front/back lawn... in pieces.
    Elastomeric sealant is able to stretch up to 50% and still remain viable as a seal.
     
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  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    i think you should reconsider where it is you are placing the pvs for i see major shading off on the right that indicates the southern and southeast skies will be blocked to one degree or another. the area toward the chimney looks like it would be in the clear from what i see.

    unless you have a pole mount that is high enough to clear the shading imposed by your house, the trees, and any wiring (shadow seen on the left from wires) that you will need to bolt down into the roof to properly secure it.

    too bad you don't own the house just to your north as it appears to be well aimed (though not perfectly south) and in the clear.
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    Let's not forget that many fire districts require a 3 ft ridge clearance for venting.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    you're right dave so he does have a dilemma. we aren't privy to seeing the whole property layout and what is out there to shade the property and when. the pole mount is still a good option if you have a good place for it and it may need to be quite tall to overcome the shading from your own home. i know what it's like having few options.
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    I will take some pics of the property tomorrow.. (the house just north of mine has the perfect solar roof!)
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    Hopefully this isnt to many pics, i scaled them all down.
    As you can see my yard is very treed in. The other potential spot is on the side of the house above the sundeck or pole mounted right against the neighbors yard (how ever they may not like that option)
    IMG_3641.jpg
    looking east, - fence on right is southish
    IMG_3642.jpg
    looking north-east ish
    IMG_3643.jpg
    Looking north
    IMG_3645.jpg
    right hand side fence is south.
    Could do a pole mount by the neighbors fence (on my side) and trim the tree a bit. however that may or may not be opposing on him.
    IMG_3648.jpg
    this side of house is south-west.
    A 45 degree mount starting at the beam above desk has potential.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    nice wintry scene of your property, but i find myself not knowing what direction i'm looking in and from what perspective. now what pics are depicting the area between your home/property and that northern home with the perfect roof? even the northern back yard area would be of interest, but we have to get our bearings when viewing the pics and in what compass direction we'd be looking. if trees need trimmed, it's a good idea that they be over your property to take liability away from you. if the pvs stay over your property and don't violate any ordinances, rules, or laws your neighbor then has no say-so in the matter. how much you want to get along with them in such a case is up to you. maybe you should get a feel for what his opinion might be ahead of time.
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    Hopefully this helps.

    Top of pic is north, bottom is south.
    birdseye.jpg

    I have also noted the orientation of each pic below :)
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    yes, that's a big help. now i know the front of your property is looking to the west and i have a good view of the trees that are all around you. i see that the trees in your back yard are a bit of a problem. in my opinion the best placement area for a pole mount would be in the backyard around the northeast corner of the house, but you will need to determine just how much if at all the trees will impede the illumination of the pvs. i am also noting the ground elevation the trees are on is also higher up than the house effectively making the overall tree elevation much higher. remember the pole would need to be high enough to catch the sun in the southwest and west directions without the house or the vents shadowing the pvs. winter is the worst case scenario as the sun is low in the sky and the tree in the southeast corner of your property will probably shade the pvs. summer angles probably won't be as bad as the sun will be basically east to west and will track in a more overhead type way. the tree farther into your backyard may shade a bit in the morning from spring to fall. sometime down the road as that tree to the south continues to grow it could also cast a shadow farther along your roof possibly reaching the northern portion. that would be down the road a bit though.

    are you fond of keeping those trees in the back for i think i would be tempted to cut them down for solar purposes, but at this point imho the worst offender is the one in the backyard on the southeast corner. i don't know what others here may think as they may pick up on something i overlooked and even though a pic is worth a thousand words, it pales in comparison to being there.

    i hope this helps and is only my opinion so take it with a grain.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    My thought too Niel, about the trees. I was thinking , before the sat image was posted, that the SE corner of the property might be a good location for the pole, downside is that it may be one of the farthest from the house and there is line loss to contend with. Tree pruning would be needed.
    Is it possible to mount by or on the shed? Shadows in winter?
    HTH
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
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  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    The shed was my original plan, due to the trees it will most likely be shaded part of the day.. A bit of pruning may minimize that. The trees to the left of it will most likely cause a shadow in the afternoon later in the year. Its amazing how hard it can be to find the perfect location.

    Another idea (if it had a bit of a distributed idea. was to lay some panels flat on top of the pergola (side of house) and maybe on the front aswell.. It would not be as efficient obviously but i could do a few "sub stations" instead of an all in one.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    you may be able to use the shed if you cut the trees in the back as these will shade that area without a doubt. if your other half or neighbors don't like the trees being cut and you actually care about their opinions, then just put in hedges or something that won't grow too tall. remember too that as the sun goes toward the west that the height of the house and its vents could cast a shadow to the shed.
  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    Re: Roof mounted panels with out the holes.

    If your neighbor is also interested in solar--perhaps the two of you can share the properly line... 1/2 the cut on his side, and 1/2 the cut on your side--and you both get the best sun for your arrays.

    Shading pretty much kills solar panel output... If you need the power, you don't want any (major) shading.

    Some people may get more sun in the AM (PM summer thunderstorms) or PM sun (AM marine layer)--so pointing the array SE or SW and cutting that way may be "good enough" for you.

    Also, are you looking to go GT or Off-Grid (battery or hybrid+battery) system? And how large... Placing the array in the best area and paying more for cabling is probably a better solution than saving on copper but have extensive shading issues.

    Clearing near the house may allow you to add solar thermal/hot water later--although, one guy build a thermal storage tank in a detached shed and buried insulated water pipe for heating very successfully (in a region with snow on the ground).

    Solar Shed and other Solar Thermal Links

    Size your needs first, then see what solutions out there may fit your site best.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    The south side neighbor just moved in last summer, younger guy so he may be in for solar projects. he certainly likes to build things :)

    For now i'm doing a smaller system out door landscape lighting (high powered leds). The current panel stock is have 2x30w, 2x50w and I just ordered 2x100w from over seas. I may sell some of the panels later and get more of the same once i figure out the long term purpose. Grid tie would be nice eventually but that will be later down the road once i officially buy the place. So for now.. its just high power led out door lighting.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    "...., but that will be later down the road once i officially buy the place."
    well that sheds some new light here. once you mount those pvs to a structure on your landlord's property it will most likely become a fixture of the property and belong to him.
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    It's actually my parents house, so that is not a worry. I'm just working on saving up a big enough down-payment before i get a mortgage :)

    So i know they wont steal my solar :)
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    So after some more examination on a sunny day, the side of the house above the desk is starting to get shadded from the roofs over hang, and this will just get worse as the sun rises throughout the year.

    side-sun.jpg

    The new plan may be to put the panels vertically along the deck rail (along the white slats)
    The ideal angles are as follows
    solar-angle.jpg

    Given the aesthetics of this I would probably keep the panels fairly vertical (0-20degrees) How much of an impact will this have on output versus say 40 degrees? I expect it will be a fair amount less but im running low on mounting locations with out tearing down trees.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    you will lose a significant amount of power in the summer should that overhang shade the pvs no matter what tilt angle you use with them. i am in a similar dilemma here in that i too have an overhang and wish to wall mount some pvs. it is a problem many of us face is trying to minimize shading. you have room for a pole mount in that area and if up high enough to avoid other buildings and trees you will reap a good amount of power from your pvs without much shading.

    as to the angle you propose it will do ok in the winter for you, but won't be anywhere near its potential at other times of the year. that angle is about optimal for winter production and the steepness will do 2 other things for you.
    1> it'll help keep the snow from building up on them.
    2> it'll allow for a great deal of solar reflections from snow.

    it would be good if you could widen the angle as you depict the pvs to allow for more temperate times of the year and use at least 45 degrees as you depict the angles. note that i would've said 50 degrees here, but you are placing horizontal stress to the mounts and not vertical so 45 degrees is a strange maximum when dealing with wall mounting. this also means being able to adjust the angle at least twice per year and complicates mounting the pvs. a pole mount may allow you to change angles more vastly as the stress of the mounts are going straight down instead of sideways.

    we refer to angles a bit more differently as it is an opposite. we reference a pv laying flat on the ground facing up as 0 degrees and is corresponding to one's lattitude so it would be a good overall angle for somebody on the equator. moving north (or south) by xx degrees changes the angle on the pv by raising one end up by that amount of angle toward the sun. if you were at the geographic north pole it would be 90 degrees or vertical with respect to the ground.

    with that the angles you list will be,
    winter 74 degrees, spring/fall 50 degrees, and summer as 26 degrees.
  • shiftshift Solar Expert Posts: 48
    Re: Roof mounted panels with out the holes.

    So if im understanding this correctly. Vertical would be 90 degrees.
    and on a 4' tall panel if i push the bottom out 12" it should give me approximately a 73 degree angle.

    6" ~ 81.5 Degrees
    12" ~ 73.5 Degrees
    18" ~ 65 Degrees
    24" ~ 55 Degrees


    I was looking at the solar rails today and will probably purchase 2 lengths with 2 100w panels installed for now and 2 more in the near future. (future proof my lighting project)
    I'm guessing I will end up around 73-75 degrees as i want it to blend and not stick out to far off the wall. Ill try a mach up with the box tomorrow.

    As for mounting the rails how long of a span can you go between bolts (in rail to wall)
    My current panels are approx 20 lbs each, (so 40lbs.at the moment with potential for 40-80lbs more if in the near future if i sell of my 2x 30/50 watt'ers for funding)

    Would you bold it using a piviting bracket or just bend a chunk of angled metal to accommodate bolting to the wall/degree of rail mount.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    i'm not going to double check your math, but the angle sounds about right and yes, you get what i'm saying about the angles and vertical is 90 degrees.

    20lbs per pv seems very light. are you sure that is the case?

    anyway, my weakest area is mounting pvs as i'm about as clueless on the mounts as many newbies are. i don't get to see this stuff personally as there's nothing around here like a solar store and i don't know any installers here to view things first hand. i made a mount for a unisolar 64 out of 2x2 aluminum angle and it's holding nicely from that brick wall. the us 64 is, i believe, just over 20lbs if i remember right so it will be a bit easy in that weight class to mount than the 40+lbs pvs i would like to mount and they must come away from the wall at least 1ft due to shading and due to a white coating coming off of aluminum soffit and facia that is landing on it leaving a white streak on the pv. if only i'd have realized then it would do this.

    if you do a wall mount i would be interested in the details and pics of your mount. don't use thin aluminum as it could flex and break in time. i think i used 1/8th inch thick on the angles and there is a bit of flex on it and this will eventually break on me, but it has held for about 7-8yrs or so so far. something like 3/16ths thick would've been better for me if it actually is available in that thickness, but i could not go to 1/4in as it was set into brick joints and that would not have left much, if any, room for the mortar to hold it in place with. you don't have brick so you will need to anchor to the wall differently than i did, which is not a big problem if you anchor into the 2xs behind the outer wall.
  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Roof mounted panels with out the holes.

    I used to do industrial rubber roofs on occasion. Its quite amazing what can happen when a high wind blowing horizontally hits the side of the building. The wind has to go somewhere so it goes up the wall and over the roof. Wind doesnt turn right angles so it creates a low pressure zone on the edge of the roof (usually 10 feet is an arbitrary distance). In the area of the roof I had to install twice as many fasteners on the roofing to keep it from being pulled upwards. People assume its the wind getting under the edge of the roofing that causes the failure, it may eventually make things worse but the usual failure mode is that the roof lifts upwards and breaks its hold down fasteners and eventually tears out the fasteners on the edges of the roofing, then the air gets underneath and finishes it off. The same thing can occur with flat solar panels and with a smaller structure, the zone of uplift may be the entire roof. Whatever you do, make sure you fasten down the panels. some Stainless steel lag bolts into the rafters and some WR Grace EPDM (Weather shield) on the deck with a few more pieces weaved into the shingles where the bolts stick out does wonders and if you ever need to remove them, lift up the shingle tab and cut them flush with a zip wheel.
  • mike95490mike95490 Solar Expert Posts: 9,362 ✭✭✭✭✭
    Re: Roof mounted panels with out the holes.

    Some property (many?) transfers will force an inspection, and a "shared array" on the property line may raise eyeborws. Or if it's not inspected/permitted by county code enforcement. Also, your state may or may not, have a solar exemption, or they may add the value of the system to your property tax.
    You may want to explore a "Living Trust" to acomplish the property transfer from your folks to you, unless they need the $ now. Or you could take over payments on the existing mortage...
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Roof mounted panels with out the holes.

    mike,
    he's in bc canada for the record. don't know all parameters they must meet.
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