pv array alignment

surveyor1

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

BB.

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

surveyor1

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.

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