Although crystalline solar power panels are often sold with 25- to 30-year lifespan guarantees, those 30-year-old modules won’t be performing as well as they did on Day 1. Performance declines as solar cells experience degradation due to unavoidable circumstances like UV exposure and weather cycles. Manufacturers realize this, so solar panels come with a power output or performance warranty that usually guarantees 80% production at 25 years.
Panel companies are only comfortable offering this guarantee because of a 2012 NREL study (“Photovoltaic Degradation Rates—An Analytical Review”) that found solar panels degrade about 0.5% to 3% each year, barring any equipment issues.
So panels degrade automatically; that’s worked into their performance warranties. There are also outside forces that can contribute to a panel’s degradation and possible failure. We talked with Sarah Kurtz, research fellow at NREL and co-author of that oft-cited 2012 study, on how technology and manufacturing changes, along with installation practices, affect degradation rates.
A complex issue
According to NREL, modules can fail because of unavoidable elements like thermal cycling, damp heat, humidity freeze and UV exposure. Thermal cycling can cause solder bond failures and cracks in solar cells. Damp heat has been associated with delamination of encapsulants and corrosion of cells. Humidity freezing can cause junction box adhesion to fail. UV exposure contributes to discoloration and backsheet degradation. These things just happen, and it’s difficult to determine how bad the degradation will be.
“Solar panel degradation and failure is not a clear-cut situation,” Kurtz said. “There are lots of different reasons why they degrade and why they fail.”
Kurtz said module manufacturers are looking into every piece of the solar panel puzzle, all the way down to the encapsulants and adhesion materials, to try to slow degradation rates.
“Companies are figuring out how to change the formulation of the encapsulants so they don’t yellow,” she said. “In my opinion, they’ve made great progress in solving this problem.”
New inverters, higher voltages and PID
If it wasn’t bad enough that solar panels turn on themselves after years in the field, outside products can also contribute to degradation levels. The increased usage of transformerless inverters on U.S. solar projects has raised the threat level of potential induced degradation (PID) of solar panels. PID happens when different components in the same system are at different voltage potentials (such as the frame and the solar cell), which can allow electrical current to leak and modules to lose their peak performance. Often, simply negatively grounding a system removes the concern for PID, but transformerless inverters are ungrounded.
When that electrical current leaks, sodium ions in the glass move toward the solar cell or the frame, depending on how the system is grounded. There’s also an issue with the whole industry moving to higher voltages, because higher voltages make that current pull stronger, and sodium ions move more easily over top solar cells, reducing their output.
Frameless modules can help reduce the PID possibility (since there’s no metal frame to disrupt voltages). And many module manufacturers take extra steps to ensure modules are PID-free now. It’s important for installers to know what products they’re combining into a full system to know if something besides the panel may contribute to degradation.
Cheaper panels and less material
Back in 2015, NREL surveyed New York installers and found that many were having the same issues with new solar modules. As module companies were trying to lower their prices, they made their frames thinner to reduce the aluminum.
“[Installers were] finding that those frames will bend,” Kurtz said. “As snow melts and then refreezes on the edge of the module, that puts quite some strain on the frame. Those newer frames would bend.”
Bent frames can strain the whole panel, and it can be especially bad as panels get thinner and less mechanically robust.
“When people squeeze the cost down, they can find low-cost materials or they’ll try to reduce the total amount of material,” Kurtz said of today’s modules. “As you optimize the cost of the module, you’ll tend to see more mechanical failure mechanisms.”
More, thinner busbars
Solar panels sometimes fail because of busbar solder bond failures. With the trend of more busbars on solar cells, you would think there is a higher chance of solder bond failures. That’s not entirely true.
“Cells can easily break,” Kurtz said. “If you have a big ribbon with a big solder bond, it puts more local stress on the cell and causes them to be more likely to break. By reducing the size of those solder bonds, you can reduce the amount of stress at the point where that ribbon gets connected to the cells.”
With more busbars and more solder bonds, there is a higher probability of solder bond failure. But the importance of one solder bond failure goes down when there are more busbars to pick up the slack. Also, more busbars across a solar cell can decrease the chance of full cell breakage.
Flexible panels and installation
As module companies decrease their costs, they may turn to ultra-thin solar cells that use less silicon. Thinner solar panels are more flexible and not as rigid as older module models, which makes installation a delicate process.
Hand-to-hand transport can affect a module, especially if installers are carrying modules on top of their hardhats. That flexing and bouncing up and down can take a real toll and lead to microcracks in the cells. Same with dropping a module and the biggest no-no—standing or walking on top of solar modules.
“It doesn’t necessarily stop working right away, but it will degrade with some time,” Kurtz said.
What can we do?
Not all new technologies are bad, nor are all modules destined for failure. Kurtz mentioned that recent NREL research has found fewer PV module issues being reported. And although the types of problems may be changing, module warranties are increasing and system lifespans are getting longer.
Smart buying and installation of solar panels and other project components can mitigate potential degradation chances. Using trusted products and installing them with care will ensure a solar system will perform at its best—with no more than 3% power loss each year.
john haggar says
The glass on the panel’s. Is there a coating like ceramic wax for a car helpful because it allows dirt to wash of easily? Or can this potentially damage the panels? There’s also products for windshields that put a protective film on the glass. Is this harmful? I clean my panels at least once a month due to dirt building up on the panels.
Elwood P. Suggins says
Just fixed a failed panel. This is not a home sized system, but a 15 watt panel for a battery charger on my boat lift. Failure started out as reduced voltage in full sun. Controller would not even turn on. While testing the panel, it stopped working entirely. Then when I happened to kick it, the volt meter spiked. Had nothing to lose so tore it apart. It is not meant to be disassembled. With the frame off, the wire connections on each end that go to the terminal box were both broken where they connect to the panel. They were simple solder joints but infinitesimally small. Maybe the size of the head of a pin. Carefully cleaned them with a wire brush, fluxed them and then put a nice blob of solder on each. Cleaned and tinned the two wires and soldered them to the panel. Put it in the sun and got 23+ volts, which is what it should put out. Put it back together and caulked all the edges and corners, front and back with clear silicone. By the way, this is a Harbor Freight solar panel. They don’t make them like this anymore with the aluminum frame. Current offering is plastic junk.
Sanjay Saigal says
Kelly can the panel life be increased by keeping them cool threw PVT route
Kelly Pickerel says
William Blanning says
After 15 years my system of 18 Sharp 175 failed. All the panes turned a dirty brown. Are they junk now?
I bought 2 100 watts eclipse solar panel ( renogy)
One of them is dark blue while the other turned it’s color to light blue. Is it normal? This happened after 2 months of use.
Prashanth Suvarna says
I’ve been often reading that panels last for a very very long time like>20yrs with negligible drop in performance. Based On this notion I looked around for used panels as new panel costs are prohibitive& picked up what seemed2b a bargain,2’×3′ Al mounted @7.5Kg each having 36 cells ostensibly supposed to put out an average of 16v on peak pwr of70w/ panel had given me21v on a falling sun during an assement(terribly low opt compared to the stuff that we come across nowadays like350w in the same size). So I was horrified when I evaluated the purchase at my place when it was giving out voltage only & no Amps. More horrifying was the fact that my small panel used for powering my Emergency Led lamp was enthusiastically powering a medium 9v fan at a reasonable speed but the panel/s didn’t provoke the motor at all. Liking closely I discovered that the 36 cell array on the panel must have had a torrid life which was why it was disposed. That’s not all,I suppose regular heating & cooling along with ingress of coastal sea mist due to suspect rubber surround that
had turned brittle over time was the final nail in the coffin of these panels resulting in inconsistent results across the whole lot that depressed me deeply .I concluded that I could try to pop open the panels & remove the accumulated corrosion after re soldering umpteen obvious bad joints that had corroded. But this is a big waste of time as they were very reluctant to separate from the glass base. The whole thing sucks. I now surmise that had the manufacturer applied his mind in selecting the proper items b4 putting the whole thing2gether would have probably resulted in what should essentially have been a fine product. So Pz evaluate solar panels carefully b4 walking away with what you think is a real bargain as that’s a real sour lemon that I have on my hands, worse they cannot be coaxed into being anything else too either. So sorry4 the txt compression.
Al Christie says
I have 14 solarworld panels with enphase microinverters. The output is running only about 25% of what it generally was when new about 10 years ago. I’m in a pickle because I accidentally lost my envoy which communicated with the internet for analyses. So I don’t know how to tell which is failing, the panels or the microinverters.
Mike Hewit says
You can a new Envoy at the Enphase store. https://store.enphase.com/storefront/en-us/about-enphase-store
Patrick Flanagan says
Kelly I am thinking of putting LG panels on my house with enphase micro inverters. Are these good products?
Kelly Pickerel says
Marlene Clark says
our solar panels are discoloring after only 1 year. Some of them are more discolored than others. What could cause this? Does the discoloration cause lower energy? No other solar panels in our area look like ours.
Kelly Pickerel says
Discoloring how? Do you know the brand of panels?
If you have monitoring and have not noticed a difference in output, then I wouldn’t worry.
What do you mean by “negatively grounding” a system?
Curtis Craig says
Grounding the negative side of the circuit so that it is held at 0V. Them the positive side might be say 600V to ground. Conversely, you could ground the positive side, which would mean the negative would be at -600V to ground.
We have come across a concern/ fact regarding formation of a Magnetic Field/loop due to string connection method. As a result, this would attract the lightning Strikes. Majorly all of our earlier Ground Mounted Projects have this kind of String interconnection
Dennis Nord says
I am looking for help with delamination on the back of my Sharp EU170U1 solar panels. I tried one customer service email and I see it is out of service. If you have a contact for Sharp solar panel service help that would be a start! I am also wondering how bad delamination is for the system. I don’t know how long ago it started. I know my system has run as expected until I got a new SMA inverter this spring. When fog rolled in the SMA turned off the system and THEN I learned of the delamination. My solar guy thinks there is humidity that enters one or more of the solar panels thru the delamination. All my panels have multiple panels. The ones I inspected show now broken areas, but I may not have gotten close enough to all of them. If the back is delaminated & the panel is still working is there really a problem? Thanks for any light you can shed on this!
Kelly Pickerel says
Backsheet issues also contribute to degradation. I’m sorry, we don’t have a contact for Sharp. A warranty claim would be best here. https://www.solarpowerworldonline.com/2016/09/backsheets-ruining-solar-panels/
Hi Dennis, I am an engineer that is researching the same issue with some Sharp modules for a client. They have experienced some critical failures and I’d be interested in hearing how SHARP handled any warranty claims you’ve made.
I would like to know about irradiation loss.For example I m discussed about desert area solar plant, one inverter modules located at down side and another inverter modules located at high side (on sand mud).
In this case any irradiation variation possibility?
James Amos says
Interesting, as I am experiencing 30% degradation across my who array at about 4 years (LG 280’s and M series Enphase Converters). My company has cleaned my panels, replaced one inverter, and replaced one panel – the only thing that mad a (big) difference was the new panel (also a 280). BIG difference. Now the are talking with LG to try and get to the bottom of the solar panel degradation. Maybe all new (24) panels? We’ll see ..
Mike Hewitt says
Your installer should own quality test equipment that can pinpoint if a solr module is not able to perform as designed. Seward solar test equipment is one manufacturer. A failed test would allow a fairly easy warranty claim.
Thank you for discussing some of the negative aspects of PV systems!
I’m not in green energy, but I work as a mechanical engineer and have extensive experience with industrial electrical systems, so I know that every technology has its weaknesses.
I get so tired of every article pretending as if solar is some magical technology without any mechanical and electrical limitations degradation. You article does well to admit that they exist and to name what they are and what contributes to their occurrence. I also appreciate yhat you have given some indication of how manufacturers are working to mitigate some of these issues. Great article!
Jim Flessner says
Have there been any reports of fires caused by solar panels? We will have a cover on the ground to minimize vegetation growth.
The report mentioned here stated that median degradation rates were 0.5% year, much less than
the 3% you cheerfully ask people to expect!
Kelly Pickerel says
We state in the article that median degradation rates range from 0.5% to 3% each year. Thanks for reading!