FULL-MOON wattage???

cupcake
cupcake Solar Expert Posts: 254 ✭✭✭
in Off Grid Solar & Battery Systems #1
Hi Pals,

I've noticed during a full-moon the controller shows a few watts coming in...

Has anyone experienced this?

Thankxxxx

--cup 'o cake
~1.5Kw PV in parallel
Morningstar MPPT-60 controllers (2) in parallel
3 Trojan tr-1275's in parallel 450ah total
Samlex 2,000 watt 12-volt inverter hardwired


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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: FULL-MOON wattage???

    Here is an old post of mine I will hack a bit:

    Solar panels do not develop enough voltage under starlight to even begin supplying any real power (self discharge or what--don't know the physics).

    And for Moon Light--Lets see.

    Anyway, assuming that they "worked" under moonlight--some numbers:
    • sunlight on an average day ranges from 32 000 to 100 000 lux
    • TV studios are lit at about 1 000 lux [i.e. 1000 lumens
    per square metre]
    • a bright office has about 400 lux of illumination
    • At sunset and sunrise, ambient outdoor light is also about 400 lux (if the sky is clear).
    • moonlight represents about 1 lux
    • starlight measures a mere 0.00005 lux

    Since solar panel power output is proportional to the energy hitting the surface... Then for a 1 kWatt array in sunlight vs moon light:

    1,000 watt array * 1 Lux moon light * 1/80,000 Lux near full sun = 0.0125 Watts of "moon light" power

    So--I would not really expect to see "watts" worth of power from a moon lit solar 1kWatt solar array.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: FULL-MOON wattage???

    To add--It is conceiveable that the charge controller sees enough voltage from the moon that it "turns on"--And the few watts you are seeing is actually load from the controller rather than generated power (just a wild guess).

    Also, most charge controllers are accurate to around 2-5% at best--It is possible that "at zero" current you are simply seeing calibration/measurement error too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    #4
    Re: FULL-MOON wattage???
    BB. wrote: »
    To add--It is conceiveable that the charge controller sees enough voltage from the moon that it "turns on"--And the few watts you are seeing is actually load from the controller rather than generated power (just a wild guess).

    Also, most charge controllers are accurate to around 2-5% at best--It is possible that "at zero" current you are simply seeing calibration/measurement error too.

    -Bill


    Would it be conceivable that the desert environment however makes the moon more condusive to reflecting sunlight on the panels..??

    There is literally no atmosphere here, the UV is at max constantly from the sun, the humidity tops out at 6% and is usually at 1% or 2%....

    When the full-moon shines here, its like somebody in the sky with a LED flashlight... so pure... so unfiltered....

    You will laugh at me but you can almost 'feel' the moon light on your skin if you turn away from it and then face it again... so for poops and giggles I went inside one night to check the controller... 3 watts...

    on non-full moons its always at zero watts at night....

    I am still trying to figure out this anomaly...

    --cake
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: FULL-MOON wattage???

    Nope; no laughing here. We have the same sort of moonlight. 3200 feet of elevation, lots of UV exposure (in Winter you can get frostbite and sunburn at the same time). A full moon will 'wake up' the controller under the right conditions (usually if you have a high Voc array) but it will not produce any actual power. Your 3 Watts from a 560 Watt array is about 1/2 of 1 percent: well within the realm of reading error Bill mentioned. You see nothing on moonless nights because there's no significant Voc to wake the controller.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
    Re: FULL-MOON wattage???
    cupcake wrote: »
    There is literally no atmosphere here

    That should take your breath away... figuratively, of course.

    I also get a bit of moonlight power in the winter when the snow is on the ground... the snow reflects moonlight up onto the panels.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #7
    Re: FULL-MOON wattage???

    "Literally"...I do not think that word means what you think it means. Diego Mantoya, The Princess Bride.

    Perhaps Figuratively is more appropriate.

    Ralph
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  • Les Nagy
    Les Nagy Solar Expert Posts: 121 ✭✭
    #8
    Re: FULL-MOON wattage???

    The sun is approximately 400,000 time brighter than the full moon. So based on this, my peak 3000W solar production would translate to a peak 0.0075 watts with the full moon. Anything you see on a charge controller with the moon is just noise and errors.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: FULL-MOON wattage???

    i don't know about you guys, but i'm against mooning pvs, especially in the winter.:roll::D
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #10
    Re: FULL-MOON wattage???
    niel wrote: »
    i don't know about you guys, but i'm against mooning pvs, especially in the winter.:roll::D

    Likewise! Beyond that, there is no noticeable voltage generated by my 1900 watts of PV during moonlit nights. Most certainly nowhere near enough to wake up either controllerl
    I remember some years ago there being a big discussion re moonlight charging and at that time it turned out to be "normal" DC leakage through the controller, from battery to PV, thus putting a DC voltage on the input of the controller and fooling both the controller and a lot of folks,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
    OOPS, guess I'd better shut this thing down for the night - - just fell asleep at the keyboard.
    Night all.
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #11
    Re: FULL-MOON wattage???

    quote_icon.png Originally Posted by cupcake viewpost-right.png
    There is literally no atmosphere here

    vtmaps wrote: »
    That should take your breath away... figuratively, of course.

    I also get a bit of moonlight power in the winter when the snow is on the ground... the snow reflects moonlight up onto the panels.

    --vtMaps


    If I've told you once, I've told you a million times ! Don't Exaggerate !
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #12
    Re: FULL-MOON wattage???

    On a cold mid-winter day, temps at -20*C or lower, when the Full moon rises before the sun goes down, you may observe an interesting phenomenon.
    Amps or Watts will drop to ~ zero on your CC (MX60 in this case) and the volts drop to ~ Vmp and hold there for several hours before dropping to zero...

    Repeated the observation for 3 days.

    But no watts!
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    #13
    Re: FULL-MOON wattage???

    I can put 5k of panels on a Classic and see VOC of about 1/2 of normal but 3 watts or less. Much less than the standby consumption of the controller. It is interesting and fun to watch, but not useful power. That said, the Classics are awesome controllers. More money, but you only cry once and you can do so much with them. If you can find the extra cash, you will love them!
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #14
    Re: FULL-MOON wattage???
    boB wrote: »
    quote_icon.png Originally Posted by cupcake viewpost-right.png
    There is literally no atmosphere here





    If I've told you once, I've told you a million times ! Don't Exaggerate !

    i don't know bob as maybe he really doesn't need any air to breath.:roll:
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