pv array alignment

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surveyor1
surveyor1 Registered Users Posts: 21
hi folks, i need your help on installing some pv units on a pitch roof. I have two gable roofs, one facing south east (az 135 degrees) and the other facing south west (az 220 degrees). Which of the two roofs should i place most of my panels on to get maximum solar harvesting?
any suggestion would be appreciated.
thanks

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,477 admin
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    Re: pv array alignment

    Use PV Watts to estimate your output from different orientations. Note there is a data output (hour by hour over 365 days) that you can load into a spread sheet and quantify your monthly/yearly output by time of day, etc.

    Also, it depends on when you need the power... For me, my time of use utility billing plan greatly favors summer afternoons (my payback is ~3x mornings and winter production. So, if I have a choice, then summer afternoon maximizing power is best for me (of course, my roof faces south east--favoring AM production).

    Of grid, perhaps you want better winter production. Or, if you need A/C, then again summer afternoons is more important.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • surveyor1
    surveyor1 Registered Users Posts: 21
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    Re: pv array alignment

    Bill,
    pv watts is not giving any significant difference between the two alignment. why?
    BB. wrote: »
    Use PV Watts to estimate your output from different orientations. Note there is a data output (hour by hour over 365 days) that you can load into a spread sheet and quantify your monthly/yearly output by time of day, etc.

    Also, it depends on when you need the power... For me, my time of use utility billing plan greatly favors summer afternoons (my payback is ~3x mornings and winter production. So, if I have a choice, then summer afternoon maximizing power is best for me (of course, my roof faces south east--favoring AM production).

    Of grid, perhaps you want better winter production. Or, if you need A/C, then again summer afternoons is more important.

    -Bill
  • BB.
    BB. Super Moderators, Administrators Posts: 33,477 admin
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    Re: pv array alignment

    What city are you using?

    Looking for grid tied or of grid power?

    Many times, it does matter. Better afternoon sun orientation is killed by afternoon clouds or storms.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset