Solar Modules: Most Common Defects

Hundreds of thousands of modules are manufactured daily, which means millions of solar modules per year. The manufacturing process is somewhat complex and although it is highly standardized, there are multiple variants and technologies. At the moment there is none of them that is free of failures and therefore even with a very low incidence we are talking about products that can reach the market with failures.

Once the product is on the market, you can also find incidents that in this case may have to do with transportation, handling, installation process and exposure to the elements. It is important to know and know how to identify the problem and its origin.

How can we identify the causes of module problems? Problems can be grouped according to two main causes:

A) Manufacturing, materials defects or quality control failure

B) External damages due to handling or harmful environments

How do defects of origin or cause A manifest? And what is the effect of each one? To simplify, we will explain them according to where they manifest starting with the most serious:

Loss of electrical performance at the cell level:

• PID. Power Induced Degradation. It causes a loss of electrical performance of the entire system since it usually affects the set of modules

• Excessive degradation. The degradation inherent in technology is increased with respect to its theoretical parameter. Causes loss of electrical performance of string modules

• LeTID. PERC technology degradation due to high temperature operation. It causes a loss of electrical performance of the entire system since it usually affects the set of modules

• LID: Initial degradation higher than that inherent in technology. Causes loss of electrical performance of string modules

Breakage or defect in cells:

• Short circuit or loss of resistance in parallel. The cell stops producing current. Causes loss of electrical performance of string modules

• Microcracks. Microcrack that can occur in the edge or center of the cell. Causes hot spots and loss of electrical performance of string modules

• Breakage. Inactive areas of cells. Causes loss of electrical performance of string modules

• Welding errors. Increases electrical resistance. Causes hot spots and a loss of string electrical performance

Backsheet defects:

• Permeability. It allows humidity to pass into the laminate. May cause snail trails, PID, and accelerated degradation

• Fissures. Brittleness of the backsheet. Can cause all permeability problems and increases electrical risk

• Bubbles and delamination. Gases inside the encapsulant. May cause performance loss and backsheet breakage

• Snail slime or aesthetic defect due to oxidation or corrosion of internal components. Sometimes it can cause performance losses or hot spots

Junction box problems:

• Permeability. Because of poor insulation. Causes component corrosion

• Diode failure. Defect or deterioration of the diode. Causes temperature rise and increases the risk of fire

• Failure in electrical connection. Due to bad welding or incorrect electrical contact. May cause arcing and increases the risk of fire

• Failure of adherence. Due to adhesive silicone problems. May cause permeability problems and increases electrical risk

Cables and connectors problems:

• Wrongly compressed or tight connectors. Assembly problem. Increases electrical risk and may cause loss of string electrical performance

• Bare wires or cables with an exposed electrical surface. Due to the loss of insulation. Electric risk increases

Frame problems:

• Insulation failure. For lack of silicone or taping. Can cause backsheet permeability problems

• Detached frames. For lack of silicone or taping

• Frames of incorrect dimensions or out of tolerance. Dimensional error that may cause a fixing or squaring problem in the installation

Glass defects:

• Scratches. For handling in manufacturing.

• Breakage due to incorrect tempering. Glass hardness failure. It can cause backsheet permeability problems

• Lack of transparency. For impurities. Causes loss of string electrical performance

Encapsulate defects:

• Yellowing. For transparency to UV radiation. Causes encapsulate or backsheet yellowing and in extreme cases can cause performance loss

• Loss of transparency. Due to impurities or deterioration. Causes a loss of string electrical performance

How do subsequent defects manifest or cause B? And what is the effect of each one? Again we will explain them according to where they manifest starting with the most serious:

Electrical performance loss:

• PID. Power induced degradation due to poor ground and negative configuration. Causes loss of electrical performance of entire system

• Mismatch. By connecting in series very different performance modules. Causes a loss of string electrical performance

Breakage in cells:

• Microcracks. Microcrack that can be produced at the edge or center of the cell by footfalls or torsion of the module. Causes hot spots and loss of electrical performance of string modules

• Breakage. Severe cell damage that can occur in large or small areas of the cell from footfalls or twisting of the module. Causes hot spots and loss of electrical performance of string modules

Tear of backsheet:

• Cracks or deterioration. Scratches or exposure to corrosive environments. Can cause all risks of backsheet permeability and breakage

Junction box problems:

• Permeability. Due to incorrect closing of the box or tampered with. Causes component corrosion

• Failure in electrical connection due to handling. May cause an electric arc and increase the risk of fire

• Failure to adhere to blows. May cause permeability problems and increases electrical risk

• Corrosion. Due to exposure to corrosive environments or installations in locations at risk of flooding. Causes temperature rise and loss of electrical performance of the installation

Cable and Connectors problems:

• Poorly pressed or tight connectors when handling to shorten or extend the cable. Increases electrical risk and may cause loss of string electrical performance

• Cables with excess tension or twist. By clamping or position of the module. Causes temperature rise and may deteriorate the electrical insulation of the cable

• Bare wires or cables with an exposed electrical surface. Due to cable handling or pinching. Electric risk increases

Frame problems:

• Detached frames. Due to knocks or incorrect fixings

• Corrosion. For installation without galvanic isolation or incorrect grounding

• Deformation. By incorrect fixing or outside the recommended area. Non-elastic deformation usually causes cell breakage in the laminate and therefore loss of performance

Glass defects:

• Scratches. Due to the use of cleaning tools or incorrect handling. It can cause loss of transparency and therefore loss of electrical performance of the system

• Lack of transparency. Due to corrosion or exposure to sand or abrasive elements. May cause loss of electrical performance of the entire system

• Torsional breakage. By incorrect fixing or outside the recommended area. Strong winds can cause point or permanent breakage of the module

What should you do if any of these problems occur?

Defects for cause A are covered by the manufacturer’s warranty, but defects for cause B are the installing company or the owner’s responsibility. Check with who corresponds in each case.