Solar Panel Output Degrades/Reduces over time - How Much?

joefizz

jimjames said:

The standard info provided with solar panels shows that they can lose output over time

Bigger danger is entropy (as with everything).
Panels in a lab will degrade roughly 0.5-1% but as others have said the weather variations more than make up for any losses in the real world. If you looked at my data over the last 6 years you would think they dropped off initially and then got better.
I have solar panels that are almost 20 years old (12v versions) and they still function but the problems are mostly bird crap damage, salt water/air exposure, delamination, rust, stress on the connecting wires etc. If you live in a coastal area they wont last as long as inland. If you live in a temperature extreme area they wont last as long. If you live in a windy/dusty area etc etc.
I get up and do a check on mine once a year and check for chafing power cables, bird crap etc etc. That stuff is the real killer.

Exiled_Tyke

Martyn1981 said:

Can I ask where you get the 0.5% figure from? I think what this thread is showing, is that little to no degradation is being seen so far, when 5% (after 10yrs) should now be starting to be obvious, and reflected in annual gen figures.

And of course the elephant in this room is that we don't have real data from 25 year old panels to know what will happen in reality. I'm guessing manufacturers have been prudent in their estimates to avoid the risk of unhappy customers down the line.  So I'd say that the manufacturers' standard data sheets are likely to be misleading. And so we've strayed from the OP's question which is there degradation and if so will we even know. 

ABrass

Exiled_Tyke said:

Martyn1981 said:

Can I ask where you get the 0.5% figure from? I think what this thread is showing, is that little to no degradation is being seen so far, when 5% (after 10yrs) should now be starting to be obvious, and reflected in annual gen figures.

And of course the elephant in this room is that we don't have real data from 25 year old panels to know what will happen in reality. I'm guessing manufacturers have been prudent in their estimates to avoid the risk of unhappy customers down the line.  So I'd say that the manufacturers' standard data sheets are likely to be misleading. And so we've strayed from the OP's question which is there degradation and if so will we even know. 

Well, we do because there are 25 year old arrays around.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.presse.uni-oldenburg.de/einblicke/54/files/assets/downloads/page0009.pdf&ved=2ahUKEwj_1OGFirrtAhXVilwKHYr4B7MQFjACegQIGBAB&usg=AOvVaw2y5ds4uukDWLf7W9eRChk2

The details of the cells have changed over the years, but there's loads of 25 year old panels around if you look.

Historically the manufacturers specs have been conservative and the useful life span has been increased to reflect this better than expected performance.

EricMears

ABrass said:
Well, we do because there are 25 year old arrays around.

But the 25 year old panels are not using any technological improvements that may have happened since and might be improving (or even worsening)  panel life.

Exiled_Tyke

ABrass said:

Exiled_Tyke said:

Martyn1981 said:

Can I ask where you get the 0.5% figure from? I think what this thread is showing, is that little to no degradation is being seen so far, when 5% (after 10yrs) should now be starting to be obvious, and reflected in annual gen figures.

And of course the elephant in this room is that we don't have real data from 25 year old panels to know what will happen in reality. I'm guessing manufacturers have been prudent in their estimates to avoid the risk of unhappy customers down the line.  So I'd say that the manufacturers' standard data sheets are likely to be misleading. And so we've strayed from the OP's question which is there degradation and if so will we even know. 

Well, we do because there are 25 year old arrays around.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.presse.uni-oldenburg.de/einblicke/54/files/assets/downloads/page0009.pdf&ved=2ahUKEwj_1OGFirrtAhXVilwKHYr4B7MQFjACegQIGBAB&usg=AOvVaw2y5ds4uukDWLf7W9eRChk2

The details of the cells have changed over the years, but there's loads of 25 year old panels around if you look.

Historically the manufacturers specs have been conservative and the useful life span has been increased to reflect this better than expected performance.

So after 35 years the PV cells are operating at 96% of original capacity.  So this suggests that indeed estimates are very conservative. But then is a 1976 panel indicative of a 2010 panel? And we are back to the same problem: we really really don't know. 

Martyn1981

Exiled_Tyke said:

ABrass said:

Exiled_Tyke said:

Martyn1981 said:

Can I ask where you get the 0.5% figure from? I think what this thread is showing, is that little to no degradation is being seen so far, when 5% (after 10yrs) should now be starting to be obvious, and reflected in annual gen figures.

And of course the elephant in this room is that we don't have real data from 25 year old panels to know what will happen in reality. I'm guessing manufacturers have been prudent in their estimates to avoid the risk of unhappy customers down the line.  So I'd say that the manufacturers' standard data sheets are likely to be misleading. And so we've strayed from the OP's question which is there degradation and if so will we even know. 

Well, we do because there are 25 year old arrays around.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.presse.uni-oldenburg.de/einblicke/54/files/assets/downloads/page0009.pdf&ved=2ahUKEwj_1OGFirrtAhXVilwKHYr4B7MQFjACegQIGBAB&usg=AOvVaw2y5ds4uukDWLf7W9eRChk2

The details of the cells have changed over the years, but there's loads of 25 year old panels around if you look.

Historically the manufacturers specs have been conservative and the useful life span has been increased to reflect this better than expected performance.

So after 35 years the PV cells are operating at 96% of original capacity.  So this suggests that indeed estimates are very conservative. But then is a 1976 panel indicative of a 2010 panel? And we are back to the same problem: we really really don't know. 

Yes, that's the issue, it takes a long time to show any variance that is noticeable outside of weather, and by then the technology has moved on again. The NREL 2012 report (page 18) suggested 0.47% degradation for pre 2000 silicon modules, and 0.36% for post 2000. But most of us will have panels produced after those in the studies, so the next decade 2011-2020, and we are already heading into another.

ABrass

EricMears said:

ABrass said:
Well, we do because there are 25 year old arrays around.

But the 25 year old panels are not using any technological improvements that may have happened since and might be improving (or even worsening)  panel life.

Yes, I said that. But it's also true of every technological improvement ever in the history of history. They're still being tested in accelerated wear lab tests, that history of accelerated wear results, combined with examples that have been in use the full 35 years or more, should provide even greater confidence that the projected lifespans will hold out. Are there any changes in particular you're concerned by?

If not then it feels like worrying for the sake of it.

mickyduck55

No obvious issues here, the grey line is expected generation... as with just about all of us May 2020 has delivered my best year ever.. a couple of weeks to go but not expecting this to move much before year end.

The_Green_Hornet

I think what you lose over time with panel degradation you will gain back with climate change.

This year is on schedule to be my best for generation due to the record breaking Spring sunshine.

joefizz

EricMears said:

ABrass said:
Well, we do because there are 25 year old arrays around.

But the 25 year old panels are not using any technological improvements that may have happened since and might be improving (or even worsening)  panel life.

And the old killer, cost reduction.
If you get the chance to look at any old arrays, they are very sturdy, thicker supports, thicker transit medium etc etc.
As things get cheaper then costs get cut which invariably means shorter end life (or more maintenance or both).