Actual Output of an Array

ColoradoSolarColoradoSolar Registered Users Posts: 63 ✭✭
in Off Grid Solar & Battery Systems #1
If I have an array of 12.15kW I know that I can't get all 12.15kW out of the array. If I want to determine the nominal watts I would have available what kind of factor would I need to use. Currently in my calculations I am using 80% so my 12.15kW array will give me a nominal output of 9.72kW. Is that a good factor to use for calculations?

Thanks,
Eric
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  • PhotowhitPhotowhit Solar Expert Posts: 5,996 ✭✭✭✭✭
    #2
    Eric, You should be able to look up your Normal Operating Cell Temperature Values (NOCT) These usually run about 75% of the panels rating, I guess you understand that their are other system losses.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • ColoradoSolarColoradoSolar Registered Users Posts: 63 ✭✭
    #3
    Photowhit said:
    Eric, You should be able to look up your Normal Operating Cell Temperature Values (NOCT) These usually run about 75% of the panels rating, I guess you understand that their are other system losses.
    I will look for the NOCT in the specs.

    Yes I understand there are many other losses in the system and I think I am taking care of them in my calculations.
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  • BB.BB. Super Moderators, Administrators Posts: 33,281 admin
    #4
    I use ~77% for Solar Panels through GT AC inverter (vs predicted hours of sun)--That will get you within 10% of your average output energy over time (a bit on the conservative side for colder climates--Hot panels produce less Vmp-array, and less power).

    For wiring and such... I always suggest a minimum of 1.25x your expected rated current to keep the wiring cooler and not have false trips on fuses and circuit breakers.... I.e., 15 amps continuous current in cable * 1.25 = 18.75 ~ 20 amp branch wiring+breaker ratings).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #5
    In Colorado, altitude may also be a factor. High altitude means less atmosphere for sun to get through and cooler temps means higher production.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • ColoradoSolarColoradoSolar Registered Users Posts: 63 ✭✭
    #6
    I am in a high valley at 7800ft. The sun is crazy strong up here and the temps rarely get above 80 in the heat of the summer.
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  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #7
    On a nice spring day with a breeze from the north keeping the back of the panels cool, you should see some pretty good output!
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • ColoradoSolarColoradoSolar Registered Users Posts: 63 ✭✭
    #8
    The only problem with the nice spring breezes here is that we almost always have wind and usually strong. Today it is showing 35mph gusting to 51mph, so I have to make sure my mounts are ready for the wind.
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