Sunpower X22-360 Performance Degradation

[mshasib]

Hi All,
I have 25 Sunpower X22-360 panels installed last year.

I was trying to see the degradation in one year my comparing total energy production on the same sunny day (with no clouds) one year apart.
On Mar 15, 2018, my system output was: 48 kWh total with a peak of around 7.4 kWh around solar noon.
This year on Mar 15, 2018, my system output was: 39.6 kWh total with a peak of around 5.69 kWh around solar noon.

Is a degradation of ((48 - 39.6) / 48) * 100 = 17.5 % normal?

I have attached the graphs from the two dates and would like some feedback. Thanks!

[Kingram]

How sure are you that it was sunny all day this March 15th , what state are you in and how many khw did your system produce today ? It has been very cloudy this month here in Arizona.

[J.P.M.]

That first date was 03/15/2017 right ?

You have too many unmeasured variables to determine degradation. For starters, all sunny days are not created equal. Without a pyranometer you'll never know. and Also the wind and ambient temps. will play a hand as will array fouling. When was the last time you cleaned the array ? Long story.

Still, if in doubt, call the installer. Something could be amiss. That's part of why you paid an outrageous premium for Sunpower stuff. After all, you got a super duper buimper to bumber warranty, Right ?

OK, kidding aside, the installer ought to be notified if only to let them know something may have gone wrong. Not fair to badmouth the equipment and jeopardize the installer's reputation if the installer doesn't know about a potential problem or get a chance to service the system if necessary. F

WIW, I estimate my S.P. stuff lost ~ 3-4 % over the first year due to burn in, which is less than the 5% spec sheet published value. After that, the annual degradation seems to be around or perhaps slightly less than the published value of 0.4%/yr. +/- some after ~ 4 1/2 years of operation.

[mshasib]

Kingram, I'm sure it was a sunny day because I was in my house the whole day. There was not a single cloud in the sky the whole day. I live in Charlotte, NC.

[ButchDeal]

Kingram, I'm sure it was a sunny day because I was in my house the whole day. There was not a single cloud in the sky the whole day. I live in Charlotte, NC.

thats funny.

a sunny day does not equal a constant of any type.

On top of that you don't have wind, or temperature information for the two days

Were the PV modules cleaned to the same degree?
Are all of the modules producing?

[mshasib]

I did not know wind is a variable in solar production. Unfortunately, I am not able to view module specific data from the Sunpower monitoring website. Is there a way to get that?

[ButchDeal]

I did not know wind is a variable in solar production.

The biggest variable is the amount of light hitting the module, then you have angle of incidence. But a very important and still big variable is the temperature of the PV module, for that you need temperature of the air and wind. More wind helps cool the PV module = cooler module produces more, ....no wind = higher temp PV module = lower production.

Unfortunately, I am not able to view module specific data from the Sunpower monitoring website. Is there a way to get that?

probably not.

[J.P.M.]

I did not know wind is a variable in solar production. Unfortunately, I am not able to view module specific data from the Sunpower monitoring website. Is there a way to get that?

You are a victim of your ignorance.

Wind is an indirect variable. Module or array temp. is influenced by the wind vector an array is exposed to. The array temp. affects system efficiency which affects output. More wind --->>> lower array temp. ---
>>> more efficiency --->>> more output per input.

-Solar irradiance varies from instant to instant. What can look like identical irradiance conditions can vary by a lot more than the eye would lead you to think. Probably not by that 17% or so you report, but more than you might think. You'll need a pyranometer to convince you otherwise.
- PV system output is f(irradiance, module temps., fouling, shading, wiring losses, mod. mismatch, shading, other stuff).
- Module temps are mostly but not entirely f(irradiance, shading, ambient air temp., local wind vector).
- Local wind vector is mostly f(array location including orientation, free space around the array including roof standoff, other obstructions.

The list goes on.

Most all of the variables are interdependent. That is, for example only, increased irradiance will increase array/module output, but will also increase module temp. which will decrease module efficiency and so lower output by a bit. Fouling (dirt) will lower irradiance input when it blocks some of the irradiance. That will tend to lower system output, but the lower irradiance will also tend to lower the operating temps. and so increase efficiency a bit which will increase output and tend to offset some of the lower irradiance.

Basically, more things affect array input and array output in many more ways than you are aware. That's certainly not a sin, and as much difference as you note is worth checking out, but that's part of the installer's responsibility. Read up on how PV operates and what variables affect output and you'll be better able to identify what may be going on and so have a better description for the installer.

Good luck.

[mshasib]

Thanks for the detailed explanation.

I was also able to connect to the monitoring system locally and was able to pull data for individual modules. The data seems to point to an issue with one module. Attached are the graphs I obtained.

Am I correct in identifying the failing module based on the graphs?
Solar Panel 3.jpgSolar Panel 1.jpg

[ButchDeal]

Am I correct in identifying the failing module based on the graphs?
Solar Panel 3.jpgSolar Panel 1.jpg

Nope. you need to do a bit more investigation. Is that module currently shadowed? is it's production constantly lower?
There should be more historic information on it, though a physical examination to see if any module has shadows would be a good start. Even a little bit of shadow or bird droppings could be a cause.

[J.P.M.]

OP: What's your zip and array orientation ? and what date and time for that data ?

Looks like when those readings were recorded, your array had a POA irradiance level of something like ~~ 500 W/m^2 if everything is running right, including reporting.

[mshasib]

There were no shadows on any of the panels and they were clean.

Zip: 28269
Date/Time: 03/25/2018 @ 3 p.m.

[J.P.M.]

There were no shadows on any of the panels and they were clean.

Zip: 28269
Date/Time: 03/25/2018 @ 3 p.m.

Array orientation, tilt & azimuth ? Can't get anything meaningful without those.

When was the last time they were cleaned ?

[ButchDeal]

There were no shadows on any of the panels and they were clean.

Zip: 28269
Date/Time: 03/25/2018 @ 3 p.m.

If that pv module is in the same plane as most of their rest and no shadows on it even from stand pipe then there is a problem with it.

[Kingram]

My system which was turned on Feb 27th 2018 and is very similar to yours I have 26 360 wt SP panels and two central inverters, So a few questions How were you able to get the data for each panel do have micro inverters ? What is the most kwh your system has produced in one day ? what was your 1 year total production and which way are your panels facing . Sorry for all the questions but I'm just trying to learn. Thanks