Does the wattage, amperage and voltage all degrade equally over time?

• Solar Expert Posts: 1,973 ✭✭✭
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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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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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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Over what time period did you collect those numbers?
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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.
• Solar Expert Posts: 593 ✭✭

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.

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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