flush mount pv

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ws9876
ws9876 Solar Expert Posts: 440 ✭✭✭
in General Solar Power Topics #1
My roof is at 22 degrees exactly south. I am right on the 45 parallel in the west US.
I really dont like the look of tilt racks and would not use them for other reasons too.
How much will I lose on PV production if I go with the 22 deg. angle????
and what fasteners are best for metal roofs with the standard profile for metal..
ie not the flat panel metal stuff with the vertical tabs...
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: flush mount pv

    My favourite angle calculator: http://www.macslab.com/optsolar.html

    Could you stand some slightly uneven legs to give it another 20 degrees tilt? You're going to have a fair drop off in Winter at 22.5, but maybe that's not an issue for you.

    Sorry I can't advise on metal roofs; never used any.
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  • mr.radon
    mr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    #3
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    Re: flush mount pv

    Just used PV Watts, they will calculate it for you. they even take into consideration the local weather effects. For example in Seattle the optimal angle is less then Latitude. This is due to the cloudy weather.
    Check out PV watts...
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  • Jburgess
    Jburgess Solar Expert Posts: 130 ✭✭✭
    #4
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    Re: flush mount pv
    ws9876 wrote: »
    what fasteners are best for metal roofs with the standard profile for metal..
    ie not the flat panel metal stuff with the vertical tabs...

    This kind of metal? If so here's how mine is mounted.

    Roofmounting.jpg
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  • phred01
    phred01 Solar Expert Posts: 35 ✭
    #5
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    Re: flush mount pv
    ws9876 wrote: »
    My roof is at 22 degrees exactly south.
    How much will I lose on PV production if I go with the 22 deg. angle????
    .
    Optimium angle for yr production is latitude -10deg. To improve winter production latitude +10deg. The loss is cosine the angle wrt the sun's elevation. There are factors that impact solar conversion efficiency. In a hot climate lack cell cooling will have a major bearing on the electricity production. Cell temp 85 degC panel output rating are quoted @ 25 degC. So loss is
    (85-25 )* -0.5%= -30%. Now mounting on a metal roof is a problem. The tin gets very hot in the sun too so the air warms up above ambient thus reducing any natural convection cooling action. Some solar enthusiasts have painted the roof area below the panels white to reduce the metal roof temperature in the sun.
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  • SolarLurker
    SolarLurker Solar Expert Posts: 122 ✭✭
    #6
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    Re: flush mount pv

    The other thing to consider is if you electric loads are summer or winter dominated.

    Will this be a grid tied system?

    If grid tied depending on your electric companies net metering rules you may want to adjust the system to meet peak loads.

    There certainly is a lot of factors to consider.
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