pannel pointing SW

jkhawaii
jkhawaii Solar Expert Posts: 30 ✭
in Solar Beginners Corner #1
I am mounting a single panel on a slightly N/NE slanting roof, now, if I tilt the panel the south ward direction it will be pointing more to the SW, how much will be lost pointing sw instead of S? it will take a bit more effort to get the panel pointed directly south. my latitude here in Hawaii is about 21 deg, I was planning on fixing the angle to 18 deg (some web site gave recommended angles like latitude x .8 something)
the other thing is Its a standing seam metal roof and was planning on using a few S-5 standing seam clamps to mount the panels to the roof along with some unistrut/super strut
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #2
    Re: pannel pointing SW

    PV Watts has several stations in Hawaii. Just plug in your numbers and see what works best for you. Use defaults for everything except the vertical tilt and rotational position (SW, S, SE in degrees).

    The closer you get to the equator, the less SW/S matters. Just a quick look at PV Watts shows that you might see a ~2-3% loss or so by not pointing south over a year (+/- 45 degrees from south).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jkhawaii
    jkhawaii Solar Expert Posts: 30 ✭
    #3
    Re: pannel pointing SW

    Interesting. 18-19 deg seems to be optimal and, loose about 2-3% facing more west
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #4
    Re: pannel pointing SW

    Yes, for people with significant weather issues (morning fog, afternoon clouds/rain), adjusting the panels to point in the "optimum" position may not be due south.

    We have one poster here that found pointing (roughly) south east in Florida got him more power. Cooler morning air (cool panels produce more power) and afternoon clouds affected his harvest.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #5
    Re: pannel pointing SW

    If you are on a time-of-use rate with your utility (that has higher rates in the afternoon), then a southwest orientation is actually better.
    On the other hand, if your skies are cloudier (on the average) in the afternoon hours, then that would be a disadvantage.
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