How to inspect visually a solar PV panel?

Man angry at defectuous Solar PV Module Label

– Part 2: Which Label Defect can make you MAD?


**Ko, vemakore!

*** Makadini zvenyu?


As always it is a pleasure to come back to you. We are surely having fun establishing new partnerships and carrying on the message out there but we do not forget we are giving ourselves the precious task of helping you raise your technical awareness of clean energy. Today we are doing it from the country of Sir Seretse Khama, first president of Botswana!!!

In a previous post, we have promised to come back into more details into the kinds of defects that could be encountered on a module and we are starting with a review of failures associated to the label.  Before jumping into that, let’s have a look at the terminology.


Clarification of terminology 

Unless you are still living in the middle ages, it is probably safe to assume that everybody has seen a solar panel by  now, but I suspect what would be uncommon is actually finding people that could visually recognize and identify correctly the different sections of a silicon solar PV module.  Am I right? Don’t be ashamed, I was in the same situation few years ago and I had to learn. I promise you it is not rocket science…only “Solar” Science :-).

  • Front side of silicon module

The picture below depicts the front side of the module. The panel is made up of multiple individual cells that are connected through the Cell interconnect or tabbing ribbon. This wire carries the current generated in the solar cells.


Front side of silicon module 2 - How to inspect visually  a solar PV panel?
Figure 1 – Front side of silicon solar PV module


The clear laminate material between layers is the encapsulation and as shown from the DuPont backsheet structure picture (Figure 2), it separates the front glass from the cells.

Solar Module Backsheet structure - How to inspect visually  a solar PV panel?
Figure 2 – Solar Module Backsheet structure (Picture from DuPont)


  • Rear side of silicon module

On the rear side, the PV junction box is an important part of the solar panels.  It is the enclosure on where the PV strings or wires are electrically connected. This junction is the output interface of the solar panel and it will not come as a surprise to you to know that the majority of these parts are manufactured from the World factory, China. My little finger is actually telling me that in the near future, a young and bright African entrepreneur would kick off the local manufacturing and make lots of money from it (Maybe me too if he remembers me:-). For the time being, we have to deal with the Far East.

The label contains essential information and the frame protects the panel.

Rear side of silicon module - How to inspect visually  a solar PV panel?
Figure 3 – Rear side of silicon solar PV module


  • Individual silicon solar cell

At the level of the individual cell, the grid fingers conduct the electricity and the bushbar plays the same role than the interconnect.

Individual Silicon solar Cell - How to inspect visually  a solar PV panel?
Figure 4 – Individual Silicon solar Cell


Clarification of Severity Rating

For purposes of clarity and to better assess the level of severity of defects, let’s define three rates of failures for this label review and the other reviews that will be covered in future blogposts.

  • R1: Poor quality with no impact on performances –> Cheap but you get what you pay for.
  • R2: Small impact on performance and/or reliability  –>Not great but you can live with that
  • R3: Big impact on performance and/or reliability –>Not worth your money and time.

An additional symbol will be added when there is potential safety risk:    “S”  –>BEWARE


Review of Label Defects

Markets conditions and environments are certainly different but whether you are in Banjul, Bujumbura or Harare, you would usually come across four types of defects as far as  labels are concerned:

  • Label not present (R1, S)

This might sound like a rather trivial thing to say but a label MUST be present on the solar panel. As shown on figure 5 , this should be on the backsheet of the module. The only case where this would be unlikely is if the panel is small, generating a power of less than 5 Watts. To give you a an idea of comparison, a typical solar panel produces about 200 Watts. So a 5 Watts module is rather small, although it would be enough to power a 5W Apple USB power adapter.

Why is it important? An absence of label implies a sub-standard manufacture and does not provide great confidence on the quality of the product. In addition, label information is needed to properly install and use the panel and Lack of this information is a potential safety issue.

Solar Module with no Label - How to inspect visually  a solar PV panel?
Figure 5 – Solar Module with no Label


  • Label not well-attached (R1, S)

Solar PV installations are built outside and should cope with the elements of the nature. Labels should then be made of materials that are water-resistant or not damaged by light. They should not be peeling or bubbling. This kind of defect could for instance be encountered in tropical regions where rain is abundant. It is not the case in Gaborone, Botswana where I am at the moment but in the meantime you get lot of light.

Why is it important? Adding to the reasons mentioned above, the label provides critical panel information for the duration of the panel lifetime and the lack of it is detrimental to  safety.

Solar Module Label not well attached - How to inspect visually  a solar PV panel?
Figure 6 – Solar Module Label not well attached (Label of left gives no Current data. Label on right give no Manufacturer data. Neither one gives Model or Serial number.)


  • Label with incorrect information (R1, S)

Having information on the solar panel is useful…surely…as long as it is accurate and correct. I guess you’ll probably appreciate the joke, but please do verify somebody has not stuck the lyrics of your favourite song in the backsheet in lieu and place of  a proper label. Those of us from the continent would certainly recognize this kind of trick we’ve all been victims of.

The Label is expected give the following information:

  1. Maximum Power
  2. Current and Voltage at Maximum Power
  3. Short-Circuit Current
  4. Open-Circuit Voltage,
  5. Maximum system voltage
  6. Fuse rating
  7. Manufacturer name
  8. Model and Serial number or barcode
  9. markings of certification (e.g: UL, IEC or TUV symbols)

Why is it important? Again technical and manufacturer data is needed to properly install and maintain equipment. The absence of it is a potential safety issue.

Solar Module Label with incorrect information 578x381 - How to inspect visually  a solar PV panel?
Figure 7 – Solar Module Label with incorrect information


  • Label with typos ( R1 )

My college grammar teacher,  Mr Ondoua, a very pedantic and sophisticated man would probably say that this is the WORST failure, that could only have been made by somebody that has either skipped grammar lessons or hired incompetent and linguistically limited people. Not only these mistakes will give you goosebumps and nightmares, they will also create doubt in your mind. So do yourself a favour, buy from a manufacturer who knows how to write properly, even if the label is in Shona or any other local language.

Why is it important?  Well by now, the clever people that you are have understood that this failure does not affect performance or safety (sorry Mr Ondoua), but is rather an indicator of the professionalism of the manufacturer and his or her language skills. So watch out!


Solar Module Label with typos - How to inspect visually  a solar PV panel?
Figure 8 – Solar Module Label with typos


We are only talking about the label and I could almost guarantee some of you would be surprised to see that out of the four defects that we covered, three of them are classified as safety issues. Would it slightly be exaggerated for a piece of paper? Well…it depends how much you care about your Life or that of your loved ones. Remember that we are dealing here with POWER and this little piece of paper contains the vital information that is telling us how to use the component correctly and we should take it seriously as none of us would not appreciate ending up as the “perfect conductor”, hairs standing , carrying electrons better than wire!


With 9 days delay, happy Earth day and avoid TAIPOS :-).




* Mhoroi: “Hello” (Plural)

**Ko, vemakore: “Long time no see”

***Makadini zvenyu : “How are you “ (Plural)

Shona is the most widely spoken Bantu language in Zimbabwe, by roughly 80% of the population (standing at 16 million in 2017). There are also speakers in Zambia, Mozambique and Botswana, albeit in smaller numbers.



Notions to remember

Clarification of terminology

  • Front side of silicon module
  • Rear side of silicon module
  • Individual silicon solar cell

Clarification of Severity Rating

Review of Label Defects

  • Label not present (R1, S )
  • Label not well-attached (R1, S  )
  • Label with incorrect information (R1, S )
  • Label with typos (R1)



  1. Review of Failures of Photovoltaic Modules – Report IEA-PVPS T13-01:2014 – IEA
  2. Silicon Solar Module Visual Inspection Guide – Version 1.2, 2016-06-04 – K. Sinclair, M. Sinclair
  3. – Degradation and Failure Modes
  4. Catalogue of common failures and improper practices on PV installations and maintenance – Intelligent Energy Europe – 2011
  5. IEC 61215: What it is and isn’t – 2012 PV Module Reliability Workshop – John Wohlgemuth
  6. – Potentials, Opportunities and Barriers for the Deployment and Usage of Solar Energy Technologies and Services in West Africa – David Ato Quansah, Emmanuel W Ramde, the ECREEE-Secretariat.
  7. Risk Mitigation Strategies for Solar Array in Demanding Climates – DuPont Photovoltaic Solutions.
  8. Long-Term Reliability and Durability of Solar Systems in Harsh Climatic Conditions – DuPont Photovoltaic Solutions.


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