Do panels degrade over time?

[DanS26]

Is this 0.71% degradation factor based on the STC or the NOCT ?

I believe it was based on NOCT. I got the factor from a Kyocera engineer directly. I have a snail trail issue that I took up with Kyocera about four years ago...so that was my impetus to set up all these calculations.

The snail trail issue is a non-issue to date, but I'm keeping my eye on it.

[J.P.M.]

The two arrays are a matched set...the only difference is the panel rating. Both oriented due south and at the exact tilt. The blue array was installed exactly two years after the black array. After adjusting for the difference in power output (ie 235 vs 245 watts per panel) I can now calculate the degradation between the two arrays due to the 24 month difference in the age of the panels. I can do this because each array is connect to matching Fronius string inverters.

Using a TED Pro to monitor the output of each array I can make a comparison and calculate the degradation based on age of the panels.

Based on my experience the first year I did see a greater than .71% factor, but in subsequent years the difference has hovered right around the expected .71% difference. I can measure this difference real time based on power output (ie kW) and also by time...day, month, year & installation to date (ie kWh).

The difference to date is within .05% of the expected .71% factor

Good & detailed info. I believe I understand. FWIW, makes sense to me.

Thank you.

[littleharbor]

I believe it was based on NOCT. I got the factor from a Kyocera engineer directly. I have a snail trail issue that I took up with Kyocera about four years ago...so that was my impetus to set up all these calculations.

The snail trail issue is a non-issue to date, but I'm keeping my eye on it.

I have seen a lot of Kyocera panels over the years and can't remember ever seeing snail trails on their cells. It is an odd phenomenon.

[DanS26]

I have seen a lot of Kyocera panels over the years and can't remember ever seeing snail trails on their cells. It is an odd phenomenon.

Here's a pic of the one panel most affected. As I mentioned earlier, it has not affected production so basically it is a cosmetic issue that is only really noticeable since it is a ground mount.

Snail Trails.JPG

[littleharbor]

Odd phenomenon, for sure. That one cell is the most extensive I've seen. Amazing that wouldn't have any effect on output. Having looked at various examples, some almost look like the traces are sinking into the silicon, others look to be cracks. Good thing it's not more common.

[DanS26]

Odd phenomenon, for sure. That one cell is the most extensive I've seen. Amazing that wouldn't have any effect on output. Having looked at various examples, some almost look like the traces are sinking into the silicon, others look to be cracks. Good thing it's not more common.

I measure the the output of the affected string against its two sister strings in that array about five or six times a year. No noticible or measurable affect so far. Also my TED system will indicate immediately if there is a production falloff between inverters......then it is a simple electrical investigation to find the cause.

If the panel ever does degrade I will replace with a matching panel from my parts inventory.

[littleharbor]

Funny, I just bought some used panels today There were some Solar Tech 125 watt modules in the lot. All of them had snail trails. One had worse trails on many of its cells than your Kyoceras. I should have gotten a picture, but forgot.

[littleharbor]

DSCN4331.JPG Well here's a couple pics of the mega snail trails I was referring to.

[littleharbor]

image_10713.jpg Another

[littleharbor]

One more.
DSCN4327.JPG