Panel Degradation

System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Does the wattage, amperage and voltage all degrade equally over time?
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #2
    Re: Panel Degradation
    NolaSolar wrote: »
    Does the wattage, amperage and voltage all degrade equally over time?
    Well, the power (wattage) is not independent of voltage and current (amperage), it's the product of the two, so it will decrease at the same rate as either the voltage or current if one or the other is the lone factor.

    From what I can remember from my semiconductor physics classes (way back in the dark ages when dinosaurs roamed the earth), I'm pretty sure that the current is the base property that degrades over time and power tracks with it.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #3
    Re: Panel Degradation

    Looking at the difference between the initial and stablised values of amorphous panels here 1 example:
    Initial:
    - 158.9W
    - Imp = 3.2
    - Vmp = 49.7

    Stabilised:
    - 135W
    - Imp = 2.88
    - Vmp = 47

    So about 5% change in V and 10% change in current. I don't know if crystaline panels will degrade along similar lines.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #4
    Re: Panel Degradation
    stephendv wrote: »
    Looking at the difference between the initial and stablised values of amorphous panels here 1 example:
    Initial:
    - 158.9W
    - Imp = 3.2
    - Vmp = 49.7

    Stabilised:
    - 135W
    - Imp = 2.88
    - Vmp = 47

    So about 5% change in V and 10% change in current. I don't know if crystaline panels will degrade along similar lines.
    I'm pretty sure that the long term degradation of crystalline PV modules is by a different mechanism.
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #5
    Re: Panel Degradation

    Over what time period did you collect those numbers?
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #6
    Re: Panel Degradation

    They're from the manufacturers datasheet for the Sharp NA micro amorphous modules. As ggunn was saying, could be that the mechanisms for thin film and poli degradation are different.
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #7
    Re: Panel Degradation

    That means that to compare them to silicon type you ignore the initial numbers and then hope for the best.

    CIGS have a significant drop the first period of time - some manufacturers have more of a problem than others.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #8
    Re: Panel Degradation

    Thin film panels degrade ~20% over the first few months. Their specifications are based on the "stabilized" panel specifications (i.e., panels will perform better than specifications for up to the first 6 months).

    After that, from what the specs. say, they will will degrade a maximum of 20% for the next 20 years or so.

    I believe one of the failure mechanisms for crystalline solar panels is the P/N doping slowly migrates across the diode junction (in 20-40 years).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • MisterB
    MisterB Solar Expert Posts: 156 ✭✭
    #9
    Re: Panel Degradation

    I've got an array of 5 35 watt Arco panels that are around 30 year old . I've had them for around 20 years. They are rated at 17 volts, 2.2 amps each. When I got them, they put out their full rated current--11 amps for the full array, now they put out 9.2 amps with actual output varying between the panels--the best one still does about 2 amps. There is a lot of yellowish discoloration that seems to have seeped from the backing material on the panels and I suspect that is the source of most of the degradation. I also have in my scrap heap a very nice looking 120 watt panel that puts out nothing--zero, not even a few MAs of current. At first I thought that a solder joint inside the panel failed but I stuck probes though the plastic backing material and have checked voltages on individual cells and the cells are dead. A real mystery. I've never seen a solar panel completely fail other than this one. What I have seen is moisture getting inside the panel due to glass cracking or poor quality and this corrodes the small flat wires that connect the cells inside the panel. The cells themselves usually are fine.
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