Everything Solar Forum

Check out PV magazine's article "Researchers assess degradation in PV systems older than 15 years"

"Scientists at the Polish Academy of Sciences have studied PV installations older than 15 years and observed a decrease in energy productivity ranging from 1.9% to 2.9% over a 16-year period. They conducted their tests on two rooftop PV systems in Sinsheim, a town in southwestern Germany."

Click here to read the full article!

That is pretty surprising, considering we tend to use much typical higher degradation rates when predicting production over the long term. It would be interesting to see if there are other studies that support similar numbers, Maybe we need to revise our models! Go Solar!

It sort of reminds me of the expected battery degradation for EV batteries (Exception early Leaf) VS what they are finding to be be the real case, much less than expected. This of course is good news. Better to undershoot expectations, especially in a hostile market with the FFI, etc..

It would be interesting to compare these numbers to a desert like environment for ambient temp variances, keeping apples to apples AMAP.

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william fitch
Owner
www.WeAreSolar.com
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It is certainly a good result if this is the general trend. the study seems to be limited in the sample size, the location and the type of PV panels. also maintenance, and cleaning play an important role in PV energy yield. A wider study will be helpful in unveiling the general trend of PV system yield degradation.

We should temper our use of these numbers for PV module degradation, both in general and even for this particular system.

Their method of using HOMER to quantify the annual output degradation will mask true module degradation. HOMER wasn't actually design to do that (note that as the former Alaska wind and solar energy program manager for AK Energy Authority, I have worked closely with Peter L & Co on the earlier versions of HOMER and even funded one of their software revisions). All we can really say from their study methods is that the entire system output has 0.11% degradation per year. 

The SolarMax 6000S inverter can take up to 6kW of DC input power but have a peak power output of 5.06kW and continuous output of 4.6kW. Thus, the inverter is clipping some of the DC power during higher irradiance periods of the day. The only way to quantify the PV module degradation is by measuring the Pmp using a meter or I-V curve tracer while correcting for irradiance and cell temperature at the instant of measurement.

Two years ago I measured some donated Suntech 175 modules that were originally made in 2008. The output averaged 92.8% of original datasheet or average annual loss of 0.55% assuming that the modules performed exactly at datasheet at the time of manufacture. This meets their datasheet of 20% over 25 years or 0.8% loss per year.