Everything Solar Forum

It is normal to see solar PV output degrade with age, but this is usually around 0.5 percent each year. However your decrease of 10 percent seems high.

Solar panels definitely produce less when covered with dust. You can just eyeball if the panels are covered with dirt or not. I think cleaning them with water just to get some of the dust out will help.

If you panels are in the roof then please be careful while attempting to clean. 


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Achyut Shrestha
achyut.achyut@gmail.com
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Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Most of the literature I have read states that rain will normally clean the panels.  However I had installed an array in 2014 and ended up moving it in 2018.  We took off the panels and cleaned them with a mild dish detergent.  It was absolutely amazing how dirty these clean looking panels turned out to be (kept turning the water black - even though we live in a moist climate and in the country, where you would not think there would be much air pollution).  So I suspect that a good washing periodically could only be of help.  As long as you don't use an abrasive scrubbing tool and a harsh detergent - I suspect it would do no harm.

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Jay Warmke
Owner
Blue Rock Station LLC
jay@bluerockstation.com
------------------------------

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com
------------------------------

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Great video.  Quite a difference.  As you note, you must have a significant amount of pollen in the area.  It makes sense that cleaning affected the amps primarily, as they are mostly a factor of irradiance while voltage is more dramatically affected by temperature.

------------------------------
Jay Warmke
Owner
Blue Rock Station LLC
jay@bluerockstation.com
------------------------------

Original Message:
Sent: Mar 04, 2021 09:09 AM
From: John Eftimiades
Subject: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Hi John,

Module soiling generally accounts for about 1 to 5% drop in performance depending on rainfall frequency. Soiling averages about 2% per month without rainfall.

In some places with lots of aerosols (e.g., Abu Dhabi) soiling can be compounded as the aerosols cling to dust particles and then glue down dust to the module glass and make it much harder to clean. I have seen some systems in this situation with accumulated dust with a ~50% drop in performance, but again this is not common.

There may be some other issue with your system.  Most likely this 4x power output was due to increase of irradiance across all 3 of your sub-arrays which are oriented to different cardinal points. Depending on the type of inverter you have, your lowest sub-array output can bring down the output across the entire system. As the sun gets higher in the sky your overall system output could dramatically increase.

You should measure module back temperature and POA irradiance and then normalize power production taking these changing factors into account.

Best regards



------------------------------
Robert Foster
Assistant Professor
New Mexico State University, College of Engineering
Las Cruces NM
rfoster@ases.org
------------------------------

Original Message:
Sent: Mar 04, 2021 09:09 AM
From: John Eftimiades
Subject: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Robert,

Thank you for taking the time to write and for the input. As things get sunnier (in what use to be sunny FL) I will certainly incorporate your suggestions. Up on the roof, I used an pyrometer and inclinometer every 15 minutes to record an average irradiance. The recordings were made before and after cleaning.  Minimal and Max readings were 640 and 680w/m2 respectively. I only measured from the vantage point of the 11 modules facing south. Big mistake! I should have taken the time to measure the irradiance of the modules facing East and West pre and post cleaning. Even though I cleaned all the modules in the array, without a measurement of irradiance for the East and West modules I can't justify any changes in their power.   Still with no significant change in irradiance, south facing panels ( the ones that were measured), showed the greatest gain in current, 1.4A to 7.89A. At least for these panels, is it not safe to conclude that their increase in power particularly current is a function of the cleaning? 

Thanks

John

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com
------------------------------

Original Message:
Sent: Mar 04, 2021 10:18 AM
From: Robert Foster
Subject: Dust, dirt and solar panels

Hi John,

Module soiling generally accounts for about 1 to 5% drop in performance depending on rainfall frequency. Soiling averages about 2% per month without rainfall.

In some places with lots of aerosols (e.g., Abu Dhabi) soiling can be compounded as the aerosols cling to dust particles and then glue down dust to the module glass and make it much harder to clean. I have seen some systems in this situation with accumulated dust with a ~50% drop in performance, but again this is not common.

There may be some other issue with your system.  Most likely this 4x power output was due to increase of irradiance across all 3 of your sub-arrays which are oriented to different cardinal points. Depending on the type of inverter you have, your lowest sub-array output can bring down the output across the entire system. As the sun gets higher in the sky your overall system output could dramatically increase.

You should measure module back temperature and POA irradiance and then normalize power production taking these changing factors into account.

Best regards



------------------------------
Robert Foster
Assistant Professor
New Mexico State University, College of Engineering
Las Cruces NM
rfoster@ases.org

Original Message:
Sent: Mar 04, 2021 09:09 AM
From: John Eftimiades
Subject: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Original Message:
Sent: 3/4/2021 11:09:00 AM
From: John Eftimiades
Subject: RE: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com
------------------------------

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Hi Harlan,

If you are going to use water, be sure to only do so when the modules are cool and not in the middle of a sunny day when they are hot, as you risk cracking the glass.

Some of the big utility arrays use an air blower that goes down the rack, blowing off dust. A leaf blower works fine.

Or do like most and just wait for Mother Nature to take care of cleaning with the next rain.

Good luck

------------------------------
Robert Foster
Assistant Professor
New Mexico State University, College of Engineering
Las Cruces NM
rfoster@ases.org
------------------------------

Original Message:
Sent: Mar 04, 2021 04:32 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

Very interesting, just mild detergent and water cleaning?

Harlan Sager

Original Message:
Sent: 3/4/2021 11:09:00 AM
From: John Eftimiades
Subject: RE: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Hi John, I'm just curious, do you have a string inverter? And what manufacturer and model? Also, what model solar modules do you have?

------------------------------
Ken Nadsady
AviSun Renewable Energy
Hudson OH
Knadsady@avisun.net
------------------------------

Original Message:
Sent: Mar 04, 2021 09:09 AM
From: John Eftimiades
Subject: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

Yes it's SMA Sunny Boy SB7.0. The modules are Canadian Solar CS6K-280

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com
------------------------------

Original Message:
Sent: Mar 05, 2021 04:39 PM
From: Ken Nadsady
Subject: Dust, dirt and solar panels

Hi John, I'm just curious, do you have a string inverter? And what manufacturer and model? Also, what model solar modules do you have?

------------------------------
Ken Nadsady
AviSun Renewable Energy
Hudson OH
Knadsady@avisun.net

Original Message:
Sent: Mar 04, 2021 09:09 AM
From: John Eftimiades
Subject: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan

John, I agree with the others and am scratching my head about this.  Not sure if that much change could be caused by some areas of a few panels where the dirt was so bad that the current was being pushed through some of the bypass diodes. I would not expect the pollen to cause the current to be reduced by more than 75%.  I still suspect something else is coming into play.  One observation is that it looks like strings B and C only have 6 of the Canadian modules in them. The 170v operating voltage is pretty low, and I would have tried to add at least one or two more panels in each string to get the voltage up higher into the more efficient MPPT operating range, which is 245 to 480V for the SB7. With your design, strings B and C will never operate in the rated MPPT range.  Also, your array is undersized for the SB7.0, it would probably have been better to go with the SB6.0 or even 5.0.  I am wondering if there is something going on with the inverter operation when the array is dusty like that. In general, I would expect the string voltage to go down when the inverter is pulling more current from the array, not up.  But, I suppose if you just hosed down the panels and they were much cooler dueing the second reading, that could account for the voltage rise.

------------------------------
Ken Nadsady
AviSun Renewable Energy
Hudson OH
Knadsady@avisun.net
------------------------------

Original Message:
Sent: Mar 05, 2021 06:19 PM
From: John Eftimiades
Subject: Dust, dirt and solar panels

Yes it's SMA Sunny Boy SB7.0. The modules are Canadian Solar CS6K-280

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Mar 05, 2021 04:39 PM
From: Ken Nadsady
Subject: Dust, dirt and solar panels

Hi John, I'm just curious, do you have a string inverter? And what manufacturer and model? Also, what model solar modules do you have?

------------------------------
Ken Nadsady
AviSun Renewable Energy
Hudson OH
Knadsady@avisun.net

Original Message:
Sent: Mar 04, 2021 09:09 AM
From: John Eftimiades
Subject: Dust, dirt and solar panels

Most definitely. I did a simple experiment measuring irradiance and output both before and after cleaning. The entire test was done in about 40 minutes with the irradiance essentially unchanged. I saw a 4 fold increase in power, mostly through current but slight improvement in voltage. If your curious: 

https://youtu.be/BgrZycaUZKA

------------------------------
John Eftimiades
Videographer/Thermographer
Skyview Thermography and Media Services
jefti@yahoo.com

Original Message:
Sent: Feb 19, 2021 02:55 PM
From: Harlan Sager
Subject: Dust, dirt and solar panels

I live in hot and dry and dusty southern Nevada. Have not had any significant rainfall in almost a year.

Do I need to wash my panels and if so what should I use to clean them?  Have had my system since 2012 and am seeing about 10% drop in annual KWHRs.

Appreciate feedback.

Thanks

Harlan