SunPower Solar Cell Discoloration

[newnmex999]

FWIW, my panels are the same as yours, went in last Oct. and has no discoloration or measureable performance degradation at this time. I monitor input w/ a Davis Pro 2 Plus weather station, including solar rad. measurement at 1 min. intervals. I monitor, record and analyze input and output on a daily basis. I'll keep an eye out. (BTW, I lived in zip 87114 for several years. Some of the best solar climate on earth)[/QUOTE]


How many panels do you have and can you post some numbers for output for oct-jan?, thx

[newnmex999]

I am in NM as well. Zip is 87144. My 21 SunPower E20-327 6.72 kWh system was turned on in October. My panels are on my South roof. Outputs on mine so far are Oct 1133, Nov 749, Dec 803, and Jan 729. I don't have any spots on my panels, but maybe this information can help you.

The spots/cells are very difficult to see unless you look when the sun is directly overhead and you have to look from the higher end of the panel towards the lower end. Take a look at those pictures I posted. If I went around to the front of the panels and looked directly at them you would not notice those cells at all!

[J.P.M.]

FWIW, my panels are the same as yours, went in last Oct. and has no discoloration or measureable performance degradation at this time. I monitor input w/ a Davis Pro 2 Plus weather station, including solar rad. measurement at 1 min. intervals. I monitor, record and analyze input and output on a daily basis. I'll keep an eye out. (BTW, I lived in zip 87114 for several years. Some of the best solar climate on earth)

How many panels do you have and can you post some numbers for output for oct-jan?, thx[/QUOTE]

16 X 327 Sunpower. I can post a lot of stuff, but I'm not sure what you want with it. I'm living in Zip 92026. Moved from Coors/Congress area to here several years ago.

[newnmex999]

How many panels do you have and can you post some numbers for output for oct-jan?, thx

16 X 327 Sunpower. I can post a lot of stuff, but I'm not sure what you want with it. I'm living in Zip 92026. Moved from Coors/Congress area to here several years ago.[/QUOTE]

Just interested in what your output was for those months? Thanks

[J.P.M.]

16 X 327 Sunpower. I can post a lot of stuff, but I'm not sure what you want with it. I'm living in Zip 92026. Moved from Coors/Congress area to here several years ago.

Just interested in what your output was for those months? Thanks[/QUOTE]

You asked for it, you got it.

10/19-10/31 - 309.2 kWhrs.
11/01- 11/30 - 579.9 kWhrs.
12/01- 12/31 - 590.5 kWhrs.
01/01-01/31 - 629.6 kWhrs.
02/01-02/16 - 347.5 kWhrs.

All dates inclusive.

Zip 92026. See handle for lat./long. el ~ 1480 ft.

These #'s have no bearing to any other systems' performance - Not even those on either side of me a couple hundred feet away which are also Sunpower systems. BTW, and FWIW, one of those is about 5 yrs. old w/ no significant measured/est. performance deterioration that I can measure and no discoloration that I can see from my office window as I write this.

Az. ~ 195 deg., el. ~ 18.5 deg.

[Ninefingers]

I had a discoleration on a BP3215 panel

I first discovered this 'rusty' discoloration on one of my 48 BP3215 panels in June 2012. I informed BP-Solar and Home Depot(Contract supplier and debt collector and do nothing provider) and installer Solular, LLC (useless) .
Nothing was done until I contacted the AG of Pennsylvania in October 2013.

see photos how the discolored panel cracked into a thousand 'breaks', but still worked.DSCN0593-S/N_BP-Panel.jpgDSCN0593-S:N_BP-Panel.jpgDSCN0703_cracked_Panel.jpgDSCN0593-S:N_BP-Panel.jpg

[newnmex999]

Just interested in what your output was for those months? Thanks

You asked for it, you got it.

10/19-10/31 - 309.2 kWhrs.
11/01- 11/30 - 579.9 kWhrs.
12/01- 12/31 - 590.5 kWhrs.
01/01-01/31 - 629.6 kWhrs.
02/01-02/16 - 347.5 kWhrs.

All dates inclusive.

Zip 92026. See handle for lat./long. el ~ 1480 ft.

These #'s have no bearing to any other systems' performance - Not even those on either side of me a couple hundred feet away which are also Sunpower systems. BTW, and FWIW, one of those is about 5 yrs. old w/ no significant measured/est. performance deterioration that I can measure and no discoloration that I can see from my office window as I write this.

Az. ~ 195 deg., el. ~ 18.5 deg.[/QUOTE]

So the question is, how do I tell if my system is outputting what it should? It's only been installed 6 months, so I have no data over time that I can compare it to. I forwarded pictures to the installation company and waiting to hear back from them. From the little I am able to find, it seems that the word "cosmetic" is being used to describe any discoloration of the cells. Cosmetics are not covered in the SunPower warranty, or most PV warranties, but SunPower does warrant the output of their panels and my contract has them guaranteeing a minimum amount of output each year for 25 years.

[Volusiano]

So the question is, how do I tell if my system is outputting what it should? It's only been installed 6 months, so I have no data over time that I can compare it to.

Get PVWatts numbers for the last 6 months and compare those with your production numbers. Then average out the % difference and use this to see how your current output compares.

For example, if your last 6 months averages out to produce about 10% higher than the PVWatts estimate, then see what your PVWatts estimate for the current month is, and see if your actual production is about 10% more than this or not. If yes, then you're not losing much output. If less than 10% higher then you're probably losing some output.

[newnmex999]

Get PVWatts numbers for the last 6 months and compare those with your production numbers. Then average out the % difference and use this to see how your current output compares.

For example, if your last 6 months averages out to produce about 10% higher than the PVWatts estimate, then see what your PVWatts estimate for the current month is, and see if your actual production is about 10% more than this or not. If yes, then you're not losing much output. If less than 10% higher then you're probably losing some output.

Oct, Nov, Dec, & Jan PVWatts estimate 2300kWh, my output 2661kWh. Output is about 16% higher then PVWatts estimate. Of course, monthly output will vary based on cloud cover, so it will probably have to be calculated every 3 months or so.

[newnmex999]

Solar Output?

Wondering if someone can explain to me what kind of output I should see on a perfect solar day at high noon from an 18 panel 5.88 E20 327 Sunpower system? Currently my hourly output at this time of year is in the mid 4kWh. I am getting this info from SunPower monitoring website. As we get closer to the summer months what output should I expect to see from my system based on the 5.88kWh capacity. Should I expect to see hourly output in the mid 5's? Or am I looking at this entirely incorrect?

[J.P.M.]

Get PVWatts numbers for the last 6 months and compare those with your production numbers. Then average out the % difference and use this to see how your current output compares.

For example, if your last 6 months averages out to produce about 10% higher than the PVWatts estimate, then see what your PVWatts estimate for the current month is, and see if your actual production is about 10% more than this or not. If yes, then you're not losing much output. If less than 10% higher then you're probably losing some output.

I wouldn't put a whole lot of faith in such a method.

- It is very likely, more like almost a certainty - that the prior 4 or 5 months are more sunny or less sunny, and other weather inputs like temps., wind speeds, etc. are different than the TMY data for corresponding months, with the result that the actual system output for those months will most certainly be different than PV Watts will calculate. This is because all those inputs have a very pronounced influence on system performance and output.
- If the current month (or so) is an anomalous weather period and/or much sunnier or cloudier, colder, or windier, etc. than immediate prior months, output will be different than prior months relative to the PV Watts output. How will system problems, if they exist, be segregated ? Put another way, if it's 10% more (less) sunny in any month, you'll never know it by eyeball. Trust me on that. If it is 10% less sunny, and you don't know it because its not being measured, you will not know if a decrease in system performance is caused by panel problems or weather, something else, or a combination of things.
- According to the NREL Solar Radiation Manual, Albuquerque solar irradiance on a south facing, lat. -15 deg. surface has monthly variations of +/- 11% for Aug., that variation generally increasing to about 20% in Dec/Jan., w/ standard dev. probably something like about 5-10% respectively. That says nothing about other weather variables that also affect system output.
- What if you have sunnier than TMY weather for a month or two as can happen ? Will the increased output mask any problems ? What if prior months were sunnier than the TMY data and current month is close ? Without current input data , that scenario will (erroneously) make current the current month's output seem deficient and lead to suspicion of a problem where one might not exist..

- To measure a change of performance in a system, measured, ACTUAL and current input to the system is needed, that is, weather data including, and primarily, solar irradiance data and other weather parameters for the time period under consideration, not the weather for the TMY month used, which BTW is from a different year for each TMY month and therefore inappropriate for this application. It is measured but historical, not measured and current.

- Sizing tools for solar electric systems rely on weather data that is better described as climate data. Climate is what you expect. Weather is what you get. The two are not the same and will lead to different output, for different purposes.
- If there is a problem with the panels and the deterioration is of the same order of magnitude as the weather variation, such deterioration will be masked to a large degree by the noise of the weather data variation. If there is a panel problem and it is progressive, it may be still harder to find.
- According to the NREL website, PV Watts estimates of actual system production can be different by as much as 40% for individual results and up to 20% for any complete year. That alone, and as the NREL website suggests, makes prediction of performance over shorter periods much less reliable, if at all.
- To have faith in the accuracy of any estimate of performance and changes in that performance, reliable measurement of the pertinent and controlling input and output variables for the time period under consideration is a requirement. TMY information is not that type of data. It is historical.

FWIW, to help solve this problem will take some measurement of current weather data including solar irradiance. Also, converting the irradiance from a horizontal surface to the array position can be something of an art in itself and also open to some interpretation.

Don't shoot me, I'm only the piano player. Not everyone who tells you unpleasant stuff is your enemy. Not everyone who tells you what you want to hear is your friend.

[silversaver]

Wondering if someone can explain to me what kind of output I should see on a perfect solar day at high noon from an 18 panel 5.88 E20 327 Sunpower system? Currently my hourly output at this time of year is in the mid 4kWh. I am getting this info from SunPower monitoring website. As we get closer to the summer months what output should I expect to see from my system based on the 5.88kWh capacity. Should I expect to see hourly output in the mid 5's? Or am I looking at this entirely incorrect?

Depends on your roof orientation and pitch. My guess is 5.2kW.

[J.P.M.]

Wondering if someone can explain to me what kind of output I should see on a perfect solar day at high noon from an 18 panel 5.88 E20 327 Sunpower system? Currently my hourly output at this time of year is in the mid 4kWh. I am getting this info from SunPower monitoring website. As we get closer to the summer months what output should I expect to see from my system based on the 5.88kWh capacity. Should I expect to see hourly output in the mid 5's? Or am I looking at this entirely incorrect?

See above. Start w/ PV Watts and figure +/- 30/40% for individual months and +/- 20% for annual sums. You may get closer but no promises by anyone. Like climate vs. weather, one you expect, the other you get..

[Ian S]

Well, well, well...

I've got discoloration too:

SP 230 panel discoloration.jpg

After a thorough cleaning - they were quite dirty - I see that I too have discoloration on my Sunpower 230 watt panels (6.9 kW installation in May 2012.) So far though, I have been unable to establish that there has been an effect on output. For now, I'll just have to monitor the panels closely. I think I will also return to the roof and photographically document the current discoloration status of every panel to see if there is any further progression down the road. I am absolutely certain that the discoloration was not present immediately after installation. Hopefully, this will turn out to only be cosmetic and not affect the output. Still, I'm not reassured as to the ultimate longevity of this system.

[Volusiano]

I wouldn't put a whole lot of faith in such a method.

- It is very likely, more like almost a certainty - that the prior 4 or 5 months are more sunny or less sunny, and other weather inputs like temps., wind speeds, etc. are different than the TMY data for corresponding months, with the result that the actual system output for those months will most certainly be different than PV Watts will calculate. This is because all those inputs have a very pronounced influence on system performance and output.
- If the current month (or so) is an anomalous weather period and/or much sunnier or cloudier, colder, or windier, etc. than immediate prior months, output will be different than prior months relative to the PV Watts output. How will system problems, if they exist, be segregated ? Put another way, if it's 10% more (less) sunny in any month, you'll never know it by eyeball. Trust me on that. If it is 10% less sunny, and you don't know it because its not being measured, you will not know if a decrease in system performance is caused by panel problems or weather, something else, or a combination of things.
- According to the NREL Solar Radiation Manual, Albuquerque solar irradiance on a south facing, lat. -15 deg. surface has monthly variations of +/- 11% for Aug., that variation generally increasing to about 20% in Dec/Jan., w/ standard dev. probably something like about 5-10% respectively. That says nothing about other weather variables that also affect system output.
- What if you have sunnier than TMY weather for a month or two as can happen ? Will the increased output mask any problems ? What if prior months were sunnier than the TMY data and current month is close ? Without current input data , that scenario will (erroneously) make current the current month's output seem deficient and lead to suspicion of a problem where one might not exist..

Of course abnormal weather pattern is going to skew this result. Nobody is dumb enough not to realize this. No need to give a long-winded lecture about this and end up not giving the OP any better suggestion since he doesn't have any before data to compare as a reference anyway.

- To measure a change of performance in a system, measured, ACTUAL and current input to the system is needed, that is, weather data including, and primarily, solar irradiance data and other weather parameters for the time period under consideration, not the weather for the TMY month used, which BTW is from a different year for each TMY month and therefore inappropriate for this application. It is measured but historical, not measured and current.

- Sizing tools for solar electric systems rely on weather data that is better described as climate data. Climate is what you expect. Weather is what you get. The two are not the same and will lead to different output, for different purposes.
- If there is a problem with the panels and the deterioration is of the same order of magnitude as the weather variation, such deterioration will be masked to a large degree by the noise of the weather data variation. If there is a panel problem and it is progressive, it may be still harder to find.
- According to the NREL website, PV Watts estimates of actual system production can be different by as much as 40% for individual results and up to 20% for any complete year. That alone, and as the NREL website suggests, makes prediction of performance over shorter periods much less reliable, if at all.
- To have faith in the accuracy of any estimate of performance and changes in that performance, reliable measurement of the pertinent and controlling input and output variables for the time period under consideration is a requirement. TMY information is not that type of data. It is historical.

FWIW, to help solve this problem will take some measurement of current weather data including solar irradiance. Also, converting the irradiance from a horizontal surface to the array position can be something of an art in itself and also open to some interpretation.

Don't shoot me, I'm only the piano player. Not everyone who tells you unpleasant stuff is your enemy. Not everyone who tells you what you want to hear is your friend.

What I proposed is a quick and dirty way to do a sanity check if you don't have any of the actual current month's data from the previous year as a reference like the poster said, but you do have historical production data from previous months before you notice the discoloration. Nothing exact or scientific. More like statistical comparison, that's all. Take it or leave it for what it's worth. No need to over analyze it. Obviously it's better than nothing.

The whole point, maybe you don't get it, is about relative comparison. If your "before discoloration" production is on the average about 10% higher than PVWatts's estimate, and you have a small enough standard deviation of this grouping, then statistically speaking, you should be around 10% compared to PVWatts result this month, too, if discoloration does not affect production. If you're well below the normal 10% deviation from PVWatts results as a reference, then maybe you should look into it more. But if you're on the mark at around the same deviation as other months, then maybe you're OK. It's not exact comparison. It's all about relative comparison against something else as a reference.

Of course nobody is dumb enough to not realize that previous months' weather is different than current month. No need to give a long winded lecture about it and still end up not suggesting anything better to the OP.