Most Common Solar Panel Defects and How to Avoid Them

19 September, 2024.

Solar panels are designed to generate electricity for 20 years or more – helping households and businesses reduce or even eliminate their energy bills, but the ongoing price war has led to some manufacturers cutting corners in order to remain competitive. As a result, some solar panels can start to fail before they reach their expected lifespan.

If you are wondering if your panels are fine or if they need replacing or repairing, then you’ve come to the right place. Here are 10 of the most common solar panel defects and how you can avoid them.

1. Hot spots

Hotspots occur when specific cells within a solar panel become overheated due to localized shading, dirt, or manufacturing defects. These hotspots can lead to irreversible damage to the affected cells and reduce the overall output of the panel.

To identify hotspots, use thermal imaging during the day when the panels are under full sunlight. Hotspots will appear as areas with significantly higher temperatures than the rest of the panel.

Ensure that the panels are not shaded by nearby objects or covered with dirt or debris. Therefore, it can be helpful to clean solar panels regularly in certain climates or locations impacted by debris. If a malfunctioning cell is causing the hotspot, consider replacing the affected panel.

Solar cells are designed to generate electricity from exposure to sunlight. However, as electric current flows through the solar cell strings, there may be some resistance due to hot spots. Very hot days can reduce the efficiency of a solar cell.

Any imperfections such as cracks, mismatches, or poorly soldered joints can also become hot spots in the long run and lead to higher resistance. There are two long-term consequences:

• Hot spots cause burnt marks that speed up the degradation of solar cells
• Portions of backsheet could show through and start a fire if left unchecked

To eliminate hot spots, reliable, skilled solar panel fitting companies like Sunselect check for imperfections on each solar cell before installing them. Broken cells and poorly soldered ribbons get automatically discarded.

2. Microcrack

Microcracks, also known as microfractures, are tiny cracks in photovoltaic cells. This type of solar degradation is often caused by mechanical stress during installation, transportation, or environmental factors like temperature fluctuations. These microcracks can cause reduced panel performance.

To spot microcracks, visually inspect the panel's surface under proper lighting – cracks may appear as faint lines on the cells or the surrounding material. Also, you can use electroluminescence crack detection (ELCD) testing, a method that identifies microcracks that may not be detected from a visual inspection.

If the microfractures are minor and do not significantly affect the panel's performance, they can be left as is. However, it's best to contact the module manufacturer for possible warranty claims if they are severe and impact output. Otherwise, consider replacing the affected panel to maintain the system's overall efficiency.

Technological advancements in the semiconductor industry have led to wafer-thin solar cells measuring around 170 mm thick – roughly twice the diameter of human hair. Due to their super thin construction, modern cells have become more brittle and prone to microcracks which can result in hot spots and poor energy generation. Here at Sunselect, we take exceptional care in handling and transporting solar panels to prevent microcracks during solar installation.

3. Broken glass

The front glass panel of a solar module is its first line of defence against rain, hailstone, dust, tree branches, and the occasional stray ball. Therefore, it should be strong enough to withstand stress while allowing maximum absorption of sunlight.

Broken glass can make solar cells vulnerable to weather damage, and when water and dust are able to seep in under the glass, it can severely diminish the amount of light absorbed by the solar module.

Whether damaged solar panels work or not depends on the type of damage. Sometimes, broken solar panels might still work; however, they won’t work as effectively, causing your energy bills to increase.

A few small cracks or micro scratches shouldn’t hinder your solar panel’s overall performance, and you shouldn’t notice the system output decrease immediately. As a solar panel incurs more damage, you may see less efficiency over time.

Damage that requires immediate attention includes shattered glass, worn seals, severe cracks, and multiple micro scratches. These problems dramatically reduce your panel’s performance. Additionally, they can degrade the whole system over time.

4. Delamination

Delamination in PV panels is a serious issue that occurs when the layers of materials within the PV module separate or become detached. It can happen due to moisture entering the backsheet via cracks and can lead to a reduction in the panel's efficiency and busbar corrosion.

To identify solar panel delamination, conduct a thorough visual inspection of the solar panels. Look for any signs of bubbles, blisters, or separations between the layers of the panel, or discoloration or dark spots on the panel's surface. Also, electroluminescence (EL) testing can reveal delamination, by capturing images of the panel in the dark.

To address delamination when the solar panels are still under warranty, contact the manufacturer to report the issue. Solar panel delamination is often covered under standard warranties, and the manufacturer may provide replacement solar modules. If the delamination is severe and negatively affects the panel's performance, it's best to replace the affected panels with new ones to ensure optimal energy production. However, beware that lamination can increase the likelihood of electrical shock, potentially creating a safety issue. If the solar system is reaching the end of its lifespan, it might be better to decommission it instead of replacing faulty panels.

5. Cracked cells

Various cell crack modes (with or without electrically inactive cell areas) can be induced in crystalline silicon photovoltaic (PV) cells within a PV module through natural thermomechanical stressors such as strong winds, heavy snow, and large hailstones. Although degradation in the performance of PV modules by cell cracks has been reported occasionally, the mode-dependent evolutions in the electrical signatures of cracks have not yet been elucidated.

The absence of robust quality control may lead to the accidental lamination of cracked solar cells into solar panels. When this happens, a mismatch is introduced to the cells, which can impact power generation. Automated production lines can screen out imperfect cells before ribbon soldering to minimize electric current resistance.

6. Poor string connection

Do not allow the strings you are connecting to the inverter to exceed the inverter’s maximum input voltage or maximum current, or to fall below its minimum/start voltage.

Ensure that the maximum voltage complies with code requirements in the area where you are designing.

Once you’ve determined that your strings are acceptable lengths for the inverter specifications, another key consideration is that the strings have the same conditions (e.g. same azimuth/orientation, same tilt, same irradiance) if they are connected to the same inverter MPPT.

Mismatches in the conditions on the strings will reduce the efficiency and power output of your solar design.

After solar cells are put together into strings, they are soldered into connected wires to complete the array inside a solar panel. When these interconnections are poorly soldered, the circuit remains open, reducing energy production by a whopping 30 per cent or more. An IR camera, which can show temperature differences among solar cell strings, can detect open circuits.

7. Defective junction box

Another cause for an open circuit is a defective junction box. The junction box at the back of a solar panel is key to conducting electricity from the solar system to your home. However, if dust or moisture seeps into the junction box, it can lead to a short circuit of the diodes inside.

When the bypass diodes are burnt, they can leave the panel in an open circuit and stop transferring electricity altogether.

Solar junction boxes act as connectors to bridge solar modules to control devices such as inverters. Inside solar junction box, the current generated by the solar modules is drawn out and directed into the electrical equipment through terminal blocks and connectors.

The junction box should be tested before use, and the main items are appearance, sealing, fire rating, whether the diode is qualified, etc.

Common faults of photovoltaic module junction boxes include aging and deformation of the box, virtual welding in solar junction box, bypass diode breakdown failure, junction box burning, junction box detachment from silica gel, etc.

8. Snail trails

Snail trails are a type of defect that appears as dark or discolored patterns on the surface of solar panels and can be seen with the naked eye. They are caused by a chemical reaction within the panel's encapsulation material caused by moisture and oxygen. Over time, this reaction can lead to the formation of conductive pathways, reducing the panel's overall efficiency.

To spot snail trails, inspect the surface of the panels regularly for any visible dark streaks or solar panel discoloration. Snail trails are more noticeable under certain lighting conditions, such as direct sunlight.

There is no practical way to repair snail trails, but they do not necessarily always impact solar panel performance. If the panels are under warranty, you may contact the manufacturer for a potential replacement or determine if the snail trails impact solar electricity output.

Even when the solar cells are broken, they can continue to generate electricity along the cracks. This, however, will cause localized heat to break down the cell surface which makes a pattern known as “Snail trails”. There may also be discolored “snail trails” along microcracks if moisture is present. Unfortunately, apart from reducing power production, snail trails also give your panels a bad look. The best way to minimize this problem is to choose top-quality encapsulation materials that prevent water from entering the laminate.

9. Potential Induced Degradation (PID)

Potential Induced Degradation (PID) is a phenomenon that affects the performance of solar panels due to a high voltage potential difference between the solar cells and the frame, glass, or mount. This potential difference can lead to a degradation of the solar cells, resulting in reduced energy output.

To spot PID, monitor the solar panel's performance regularly and look for signs of decreased efficiency. Some symptoms of PID include a rapid decline in energy production or a significant drop in performance during high humidity and high-temperature conditions.

To address PID in solar panels, consider using PID reversal equipment. Properly grounding the system and using string inverters or module-level power electronics can also help mitigate PID effects.

Voltage, heat and humidity can cause PID on poor-quality solar modules, which can lead to reduced energy yield and cell damage. Solar panels are often connected in long series to produce enough voltage to drive solar inverters. However, when there is too much voltage difference between the grounded frames and solar cells, they may begin to deteriorate.

To prevent PID, solar panels go through enhanced PID tests to ensure the components do not break down under high voltage.

10. Cracked backsheets

Solar Panel backsheets will improve the efficiency, life duration, and overall performance of the module. However, some defects are causing dangerous consequences for solar panels. It is important to identify such problems and find instant solutions.

A backsheet plays a vital role in shaping the final form of the module. These polymeric materials protect from UV light and moisture and work as electrical insulation. Below, you will find some signs for backsheet failure:

• Delamination
• Bubbling
• Cracking
• Yellowing

Sometimes, property owners or operations and maintenance professionals are too late at spotting defects, which leads to severe problems. This makes it essential to identify problems before it is too late. The delayed intervention will disrupt energy production and pose a risk for total failure. Furthermore, there are also risks of shock due to leaking electricity. The reason for material degradation is often a defective backsheet.

Solar modules are exposed to temperature fluctuations every day and, when there are cracks on the backsheets, water can seep into the module laminate and damage solar cells.