Panel Long Term Efficiency

[Mangas]

Had an interesting discussion the other day trading opinions about the long term efficiency of solar panels most specifically, whether they degrade over time and to what extent.

Is there linear curve where they reach a certain efficiency point and don't degrade further or, don't degrade at all. I realize it depends on the manufacturer but are there any published minimum industry standards along these lines?

We talked about whether panels manufactured say 6 years ago compared to the engineering and manufacturing processes of today give better durability/efficiency. In my case, our panels seem to be delivering the same DC output as when new but the question of what their useful life is nags at me.

Realize its all a little subjective but was curious what the engineering guys think.

[Cariboocoot]

From my admittedly limited experience the prediction of a 1% loss per year is not at all accurate. I've still got an old, cheap (by the standards of the time) panel that is as close to 100% output as ever. It's only 15 Watts, but it's also 15 years old.

From what I've seen on the forum they either fail entirely or last the full 20 years expected with no noticeable degradation in output.

I'm interested in others' experience with this as well. It's similar to the topic Rolland brought up about lifespan of GTI's. Same situation too; the whole industry is so new compared to other technologies that there really isn't much data to form a conclusion from.

[Mangas]

Interesting Coot.

Also, where the panels are set up may contribute too. I'd like to claim the the desert southwest is tough on the engineering but I know the colder climates whack em' pretty good too over time.

[Cariboocoot]

Interesting Coot.

Also, where the panels are set up may contribute too. I'd like to claim the the desert southwest is tough on the engineering but I know the colder climates whack em' pretty good too over time.

Well we kind of get the worst of both here as there can be 100C temp difference between Winter and Summer. Roofing that faces due South, btw, gets murdered here: always has to be replaced before any facing North. Since panels tend to have the same orientation they are subjected to pretty harsh conditions. So far my Sharp 175's are perfect, but they've only been up since 2008. Certainly no noticeable power loss, much less the 4% predicted.

[BB.]

I believe that one of the long term failure modes is the P/N doping of the diode junctions. The "junction" doping "migrates" over time (30-40 years?). And, I would guess, the hot sun running the cells at high temperatures during the day will help speed the migrations.

I did some quick searches and could not find anything on-line about the issue.

However, most likely, it will be simple material failures from thermal cycling and UV degradation of materials that most panels will die from.

I believe glass panels with crystalline cells will last the longest. With flexible panels + thin film failing around 2-10 years (guesstimate).

-Bill

[Mangas]

I guess if the efficiency hangs in there say 80% + at the end of 15 years it feels about right to replace them at 20 years unless a generational technology improvement enters the market. Course hail and lightening damage is always a deal breaker.

I'm one of those guys that prefers not to run out the string before upgrading. Out here it can cause more trouble than its worth. I think you guys got it it right. Interesting to see which manufacturer gets to bragging rights after awhile.

So far the Sharps have been a reliable product for us.

[BB.]

My installer really loved the Sanyo HIT Modules--Zero return after many years of installations.

Not sure they are available (as Panasonic?) at this time.

-Bill

[Mangas]

"Zero return after many years of installations"

Agree Bill, that's the standard!

[PNjunction]

With flexible panels + thin film failing around 2-10 years (guesstimate).

My original thin films for occasional camping are still holding up to original specs after 3 years, but when not in use I don't leave them exposed to the sun to stop the clock - I hope. No long-term experience here, but I'm keeping an eye on them.

[BB.]

I believe UV and Thermal Cycling are two major "panel killers". Storing between uses should stop the clock on those effects (in my humble opinion).

Other, especially thin film, panel killers are oxygen and water--As long as the "seals" are good--then all should be well.

-Bill