Flat panels at 45 deg. lat?

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cptdondo
cptdondo Solar Expert Posts: 103 ✭✭✭
in Solar Beginners Corner #1
I'm trying to get a guess at how much I lose with panels laid flat at 45 deg. latitude. I know they should be tilted at 45 degrees; if laid flat in theory I should have about 70% efficiency...

How does that relate to reality?

I am using Kyocera 135 (12v nominall) panels with a Morningstar duo PWM controller to charge 12V batteries.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Flat panels at 45 deg. lat?

    Actually 45 degrees isn't the right angle for 45 Lat. Take a gander at the Mac's Lab calculator here:
    http://www.macslab.com/optsolar.html

    For Summer flat panels won't be as bad as in Winter.

    Run the numbers against PV Watts http://www.nrel.gov/rredc/pvwatts/ and see what you get.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #3
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    Re: Flat panels at 45 deg. lat?

    Go to this link for PV Watts:

    http://www.nrel.gov/rredc/pvwatts/site_specific.html

    This is for USA IIRC.

    For other parts of the globe, use this string in your search engine:
    pv watts

    In the results, there is/are a site/sties for locations outside the US.

    Very interesting data. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • cptdondo
    cptdondo Solar Expert Posts: 103 ✭✭✭
    #4
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    Re: Flat panels at 45 deg. lat?

    Interesting, Seems that in the summer, flat panels actually make more power than static tilted....

    Which is fine; my highest demand is in the summer, on cloudless sunny days. So on the days I use the most power, the panels make the most. On days when I don't need it (as in winter, when it's cloudy and rainy here) the panels don't make as much. I'm OK with that.

    Since this is on an RV, tilting the panels is not practical (I know RV tilting mechanisms can be had, but they're not practical for what we do.)

    Thanks guys. The panels are going on the roof this weekend. :D
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #5
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    Re: Flat panels at 45 deg. lat?

    Dead flat panels do not clean themselves well, so an occasional cleaning is a good idea.

    For an RV, you would prob want to clean the panels fairly frequently anyway as roads and freeways are amazinlgly dirty places.

    OK Good luck with your projectl Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • cptdondo
    cptdondo Solar Expert Posts: 103 ✭✭✭
    #6
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    Re: Flat panels at 45 deg. lat?

    good point about the cleaning. I've been thinking about this. The single biggest user energy is the fridge. My fridge takes outside air in and exhausts it into the living space (it's a compressor fridge).

    So the best orientation is with the fridge intake to the north to minimize heating of the air intake and that sets me up for hinging the panels on the south side so I can elevate them. Not sure I will ever do that but I can certainly make provisions in the wiring and the mounts for a future hinge.

    Thanks! I'll post pics when it's all done this weekend.
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