Should New PV panels Face East, West Or Both?

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pabloesguapo
pabloesguapo Solar Expert Posts: 116 ✭✭
in General Solar Power Topics #1
I'm adding another array to my off grid system.  18 panels, 6 strings of 3, into a midnite classic 150
(my third in a string of charge controllers, in "follow me" mode) .  They will be mounted on a roof,
which faces east and west.  Should I mount them all on the east side, west side, or a combination
of both?

Should I be shooting for getting my batteries to full SOC ASAP, or try for a longer "sun day" in the afternoons?  Or both?

Thoughts? 
27 Kyocera panels, 6,500w
24 CG2 6v batteries, 48v, 630Ah
Midnite Classic 150 & Classic 150 Lite in "follow me" mode
(2) Outback fx3648 inverters
Generac ecogen 6kw backup generator
Mate3s
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  • softdown
    softdown Solar Expert Posts: 3,822 ✭✭✭✭
    #2
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    Find information here. I think the output tends to be a little bit higher from western panels? I'd vote that a 50/50 combo would be most effective - based on my previous understanding.

    As I recall this combo is quite a bit better during the summer than the winter. Fine for seasonal cabins that are not heavily used in the winter - for example.


    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • pabloesguapo
    pabloesguapo Solar Expert Posts: 116 ✭✭
    #3
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    Thanks for that resource. 

    I know that E/W facing is not as efficient as South facing. I will take that hit, because roof mount is the most logical and economical use of space on the property.  For starters, location of any new south facing array would be so far from the control center, the voltage drop would be insane.

    Which end of the day should I try to extend my charging time, morning or afternoon?  Is it a coin toss?  Can I put east and west facing panels on the same charge controller? 
    27 Kyocera panels, 6,500w
    24 CG2 6v batteries, 48v, 630Ah
    Midnite Classic 150 & Classic 150 Lite in "follow me" mode
    (2) Outback fx3648 inverters
    Generac ecogen 6kw backup generator
    Mate3s
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  • softdown
    softdown Solar Expert Posts: 3,822 ✭✭✭✭
    #4
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    Going from old memories here - thinking it is pretty much a coin toss on average.  East or west panels do pretty well - except during the winter. I like the fact that you have all day to harvest - it is literally better if you have enough panels I think. My panels are geared for winter time production - 45 degrees at 37N. So production is pretty weak both early and late during the summer time.


    Not sure enough about the CC to even hazard a guess. I'm one of the least "electrically talented" ones here. I love to experiment - which helps keeps me active. My experiments go sideways more often than not.

    The main 48 volt system though? I do not play around with that. I need reliable power for freezers and fridge. Being a prepper - have three freezers full of chicken. Just bought a new fridge yesterday - thinking of a new thread for that.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,822 ✭✭✭✭
    #5
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    Having considered it more - if I loaded one side more than the other? I'd do the east side more - bulking takes more power than power than floating.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #6
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    It depends on your usage.  We added a array to take up the morning load of the toaster.   You might use the microwave more in the afternoon..
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • mountainman
    mountainman Registered Users Posts: 439 ✭✭
    edited July 2020 #7
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    It also depends on location.
     Summer here we have frequent afternoon thunder storms and triple digit temps. So east produces more.


    2kw array 6 345 q cells  make sky blue 60 cc
     6 230ah GC @36 volts 
    18 amp accusense charger. 3650 champion 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,443 admin
    #8
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    You might also look at South East and South West orientations...

    Softdown's PVWatts link above--They have an option to download hour by hour 365 Days a year solar production (based on "a real day" that is representative of the "average" days over 20 something years). So, you can do some spreadsheet experiments and see how things work out by day/season/charging vs loads/etc.

    For PWM charge controllers--You can use two arrays with E/W facing without issue.

    For MPPT charge controllers--They set their Vmp-array operating point (for maximum harvest) based on the present Array Temperature (hot panels, lower Vmp-array). So, the optimum harvest would require separate MPPT controllers, one for each "differently facing" array.

    In practice--Not sure how much difference you would see... I am of the opinion a 10% difference is almost impossible to "measure" and "confirm" with home test gear/solar charger reports. You need lab gear, and a reference cell/panel to be better than 10% accuracy.

    Some charge controllers/solar GT inverters have been seen to be 2% accuracy... And other seem to have been 6% accuracy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    #9
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    I my case, I let my loads decide for me.  Since my primary arrays are on rotating mounts, I can run my heavy loads from about 8:00am till about 4:00pm.  So, getting to a full state of charge in the morning is easy.  But, my primary arrays start getting shading by about 4:00pm.  I've added an additional 1000W array facing due west so I can run loads till about 6:30pm without any battery depletion.  That's important if I want to be running the air-conditioner later in the afternoon.
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
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  • New_Mexico_Will
    New_Mexico_Will Registered Users Posts: 107 ✭✭
    #10
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    Loads being equal, I'd put more panels on the east side, just because panels are more efficient in colder weather.
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  • 706jim
    706jim Solar Expert Posts: 515 ✭✭✭✭
    #11
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    I have 3 panels facing southeast and three facing southwest. This has worked well for me.
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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