Solar panels: Do they degrade with age?

[MtB]

As title, do solar panels degrade with age?

 

This bright but overcast morning, my pair of 80W panels (in series) were only delivering 0.1 amps into a battery bank down to 24.6v. There are plenty of people on here who claim their panels still work perfectly well in dull conditions, even moonlight. So what's wrong with mine?

 

I was chatting about this with someone who worked a while back with a Chinese scientist in their solar export industry. He says solar panels degrade with age but in the UK we don't seem to appreciate this fact or care. Consequently China with its massive surplus stocks from state subsidised over-production exports their oldest stock specifically to the UK. He reckons my panels are probably simply too old and need replacing with genuinely new.

 

Is there any truth in this or was something being lost in translation?

 

 

Edit to add - Straw Poll:

 

Who here has solar? What is the charge current showing on your solar controller this morning?

Edited October 22, 2015 by Mike the Boilerman

[Alan de Enfield]

Yes they do degrade but over 20 years its something like 25% degradation of the output.

 

I'll try and find the figures.

 

Edit - found some stuff :

 

............The warranty conditions for PV panels typically guarantee that panels can still produce at least 80% of their initial rated peak output after 20 (or sometimes 25) years. So manufactures expect that their panels last at least 20 years, and that the efficiency decreases by no more than 1% per year.

What makes talking about lifetimes for PV panels difficult is the fact that very few panels have been installed for long enough. In the UK, more panels have been installed between 2006 and 2008 than in all previous years together. Globally, only a small proportion of all PV panels installed is older than 10 years.

What we found at CAT
Here at the Centre for Alternative Technology we installed our first integrated PV roof of 180 panels, rated at 75W peak output, in 1997. In spring 2010 we did some refurbishment on that roof and used the opportunity to inspect and test each of the panels. We performed a so-called “flash test” for each individual panel to establish how much of the original rated peak output of 75W the panel can still achieve. The result averaged to around 68.5W – only around 9% decrease over 13 years (0.7% per year). There were some differences between individual panels, but even the lowest performing panels still produced around 60W (20% decrease).
We did find some damage to some of the panels - there was laminate peeling off at the back and some colour changes (yellowing) at the front – but none of the 180 panels was in a condition that required replacement.

While 13 years is old for a PV roof in the UK, it is not a lot in terms of PV panel lifespan. Fortunately, there are some examples of very early PV roof installations which tell us more about the long-term durability and performance of solar electric panels.

Edited October 22, 2015 by Alan de Enfield

[MtB]

Thanks for that Alan. The point is, many of the solar panels being sent now to the UK are already a decade old before they even get here, apparently. But from your article, it doesn't really matter. It certainly wouldn't be causing my microscopic charge current in dull conditions.

[kris88]

Some types of panels are better in overcast but bright conditions than others. At the risk of stating the obvious have you cleaned them recently?

 

Regards kris

 

For clarity panels by unisolar( the stick ons.) develop more power from ordinary daylight, but you get less power under full sunlight. They are some kind of film rather than cells.

Edited October 22, 2015 by kris88

[MtB]

Some types of panels are better in overcast but bright conditions than others. At the risk of stating the obvious have you cleaned them recently?

 

Regards kris

 

 

Yes I have. I clean therm constantly!

 

Washing a week of dust off and clearing away the odd leaf usually raises the output from 0.1 amp to 0.2 amps. 100% improvement...

 

Which type of panel is good in overcast conditions specifically please? I'll buy some.

[nicknorman]

Do you have panels in series or parallel? PWM or MPPT?

[kris88]

I edited my post, but see you have replied first. Unisolar panels, the film types rather than cells.

Although there have been hybrid panels mixture of cells and film. (Panasonic ht) these seem to get the best of both but are exspensive.

 

Regards kris

[Alan de Enfield]

There is a 'new generation' of solar panels which I am told :

 

"are designed for low light angles found in the higher latitudes (such as the UK)"

 

They give an all round average increase of 10% output which is around the 'same' as traditional panels in the Summer, but much higher (around 100% increase) output in the Winter when the Sun is lower in the sky.

 

Supplier Bimble Solar.

http://www.bimblesolar.com/offgrid/12v/12v-170w-cis-mounting

 

An MPPT controller will give around 30% more output than an MWP.

 

Add together and get 40% more from the same sized panels.

 

I am just in the process of installing one of these 170w panels (MPPT controller) and on a test-connection (prior to making the brackets) I was getting 4.8 amps on an 8/8th cloud cover day.

Edited October 22, 2015 by Alan de Enfield

[Tom and Bex]

We seem to hardly get anything from our solar on cloudy days, particularly at this time of year. We have 1kw of panels on our roof at the moment (mounted flat) connected in series to an mppt controller. This morning we were getting about 4-6A into our batteries (40% SOC).

 

Tom

[kris88]

It seems Panasonic(Sanyo) have stopped making there hybrid modules. Which is a shame. I have no experience of the new modules available. But have used unisolar panels for over 10years. You definately get more energy out in low light conditions. But less in full sun, for equivalent wattage.

 

Regards kris

Edited October 22, 2015 by kris88

[MtB]

Do you have panels in series or parallel? PWM or MPPT?

 

In series, with a Tracer MPPT controller.

 

Gotta go and mendy some boilers now, back later to read all the replies. Many thanks all!

[NilesMI]

As I understand it, some of the flexible, stick down panels are not particularly good when stuck to a metal roof. As the temperature of the roof goes up, on a sunny day, the efficiency of the panel goes down, so that paradoxically they can give a lower output on the sunniest days.

 

I am going to be experimenting with sticking a couple of the (uni-solar??) panels to my roof. They don't claim a high output per surface area, but do claim to continue to work in duller conditions and that they don't degrade in efficiency as much as their temperature rises. I will see how that works out in practice.

 

MtB is not the first person I have heard report that on a moderately overcast day, they get virtually no output at all from their PV panels.

[canals are us?]

I have 280 watts of solar mounted flat on the roof and a 30amp PWM topray solar controller all wired individually back to the controller and I have just checked and I'm getting 3.6-4 amps in cloudy conditions The most I have had so far is 13 amps. The panels are 2x 80watt and then 1x 120 watt from bimble, also used and manufactured in 2001.

 

I'm sure something must be wrong? Could the controller be faulty? Loose connection.

 

James

Edited October 22, 2015 by canals are us?

[NilesMI]

James, what is the battery SOC when you are reading your panel current?

[KJT]

Yes I have. I clean therm constantly!

 

Washing a week of dust off and clearing away the odd leaf usually raises the output from 0.1 amp to 0.2 amps. 100% improvement...

 

Which type of panel is good in overcast conditions specifically please? I'll buy some.

 

This might help. http://www.energymatters.com.au/panels-modules/thin-film-monocrystalline/

 

 

 

As a matter of interest I have four standard type 100 watt Chinese panels which I bought new four years now. I have no idea actually how old they are,

On a good day with the older PWM controller I had fitted they produced a combined output of about 22 amps max. But generally around the 8 to 12 amps figure. Since I had a Tracer MPPT controller fitted I don't recall ever seening that figure, usually around the 19 to 20 amps figure max, which surprised me. The panels are wired in parallel. Perhaps they would be better wired in series. But the general average seems to be higher, around 10 to 14 amps. So possibly the MPPT controller comes into its own on duller days.

Last year I had a 165 watt thin film panel installed and in bright, but not sunny conditions, consistently out performs the older four, on a watt for watt basis, giving normally around 7 to 10 amps and occassionally around 12 amps. It is wired to its own Tracer MPPT controller. So it seems the newer one is certainly more efficient than the older ones.

 

Ken

[Albion]

As title, do solar panels degrade with age?

 

This bright but overcast morning, my pair of 80W panels (in series) were only delivering 0.1 amps into a battery bank down to 24.6v. There are plenty of people on here who claim their panels still work perfectly well in dull conditions, even moonlight. So what's wrong with mine?

 

I was chatting about this with someone who worked a while back with a Chinese scientist in their solar export industry. He says solar panels degrade with age but in the UK we don't seem to appreciate this fact or care. Consequently China with its massive surplus stocks from state subsidised over-production exports their oldest stock specifically to the UK. He reckons my panels are probably simply too old and need replacing with genuinely new.

 

Is there any truth in this or was something being lost in translation?

 

 

Edit to add - Straw Poll:

 

Who here has solar? What is the charge current showing on your solar controller this morning?

Just a couple of additional thoughts:-

My solar panel supplier told me that if the panels are wired completely in series that they are more vulnerable to partial shading. Is one of your panels shaded?

What about corrosion of the termination where your panels join each other to form your series chain? I had a corrosion problem at one time where mine were joined (They are four 90W panels with two paralleled pairs linked in series. The connections have now been reworked and improved in waterproof junction boxes) and the reduction in output was significant.

Roger

Edited October 22, 2015 by Albion

[Phil Ambrose]

Only guessing but the age of a "new" panel is irrelevant provided the panel has been stored correctly, ie in the dark which would mean it has not been subject to degredation ny solar activity

Phil

[chubby]

I ve no idea about technical stuff and how to interpret readings but mine at 11.30 show

 

0.9 - 1.1 amp / amphour ....no idea which

14.5 v on smartgauge

100 soc on smartgauge .

 

400w , mounted flat , 40 A mppt tracer box , wired in series .

My panels were from a firm called Triple Solar in Harlow & i bought them cos they were marketed as being good in low light . They were £100 each , reduced to £90 when buying 4 or more on ebay , Free delivery .

Fitted in March 2014 . My engine has not been run for recharging since that date . I am , however , very cautious with power usage , rarely watch TV (12v ) , i run the usual pumps , have LED lighting throughout & also run a twin tub washing machine ( a big one , not a portable one ) & a Dyson hoover . I do not run the engine when using these 2 240v items .

cheers

ps my boat is on south GU canal .

ETA : my SOC is rarely below 85 , but like i say i rarely watch TV & own no gadgets , laptops , playstations etc , just an ifone to charge daily

Edited October 22, 2015 by chubby

[canals are us?]

James, what is the battery SOC when you are reading your panel current?

 

No Idea on the SOC but my voltage at the far end of the boat was reading 13.5 volts on a cheap cig lighter voltmeter and 13.7 volts at the solar controller. I have 2x Trojan T105'S about 242Ah. I may add another 80 watt panel.

 

James

[Neil Smith]

I ve no idea about technical stuff and how to interpret readings but mine at 11.30 show

 

0.9 - 1.1 amp / amphour ....no idea which

14.5 v on smartgauge

100 soc on smartgauge .

 

400w , mounted flat , 40 A mppt tracer box , wired in series .

My panels were from a firm called Triple Solar in Harlow & i bought them cos they were marketed as being good in low light . They were £100 each , reduced to £90 when buying 4 or more on ebay , Free delivery .

Fitted in March 2014 . My engine has not been run for recharging since that date . I am , however , very cautious with power usage , rarely watch TV (12v ) , i run the usual pumps , have LED lighting throughout & also run a twin tub washing machine ( a big one , n

 

 

 

 

 

ot a portable one ) & a Dyson hoover . I do not run the engine when using these 2 240v items .

cheers

ps my boat is on south GU canal .

ETA : my SOC is rarely below 85 , but like i say i rarely watch TV & own no gadgets , laptops , playstations etc , just an ifone to charge daily

You must read lots of books or sleep a lot.LOL.

 

Neil

[Bettie Boo]

Hey Mike

 

We have 1K of solar on the roof, 4 x 250w panels layed flat, MPPT controller. We were reading 6 amps this morning, but we are moored beside some pretty high trees and it was pretty overcast here this morning.

 

Hope that helps somewhat.

 

B~

 

 

ETA - once a weak sun was on the panels this afternoon the reading went up to 20 amps that was around 4:00 pm, had the sun been out at lunch time I would have expected around 35 to 40 amps

Edited October 22, 2015 by Bettie Boo

[Boredrider]

We have 6 X 100W semi flexible panels wired in series pairs and then paralled into an Outback 60 MPPT. In spring and summer we were seeing 30 amps regularly and persistently and getting over 1 Kwh per day. Since the beginning of October, maybe a little earlier, we have only been seeing a max of 6 amps and less than .3Kwh per day.

 

I am fairly convinced that the reduction in output is down to the sun never getting high enough in the sky at this time of year.

 

We used the generator on the towpath for the first time this year on Tuesday, and immediately had a moan from the boat moored behind about the noise!!

[matty40s]

I ran my engine for the first time since February 16th this week for electric, after 8 dismal grey sun free days had reduced bank to 63%.

I only ran it once for 2 hours, since then the bank has started creeping back up. A single sunny day will get it back to 100%.

[ditchcrawler]

Same thing being discuses on the DBA list

[MtB]

I ran my engine for the first time since February 16th this week for electric, after 8 dismal grey sun free days had reduced bank to 63%.

I only ran it once for 2 hours, since then the bank has started creeping back up. A single sunny day will get it back to 100%.

 

What make and model of panels do you have, and how many? And which controller?

 

And how many batts?

And what device is telling you "63"?

 

Many thanks