The PID effect (Potential-Induced Degradation) in photovoltaic modules is a common performance degradation phenomenon that will lead to a decrease in the power generation efficiency of the photovoltaic system. PID means that when photovoltaic modules are affected by external voltage for a long time, problems such as power attenuation, reduced efficiency, and shortened life will occur. By conducting PID testing on photovoltaic modules, problems can be discovered in time and corresponding measures can be taken to optimize the performance of the photovoltaic system and extend its life. Millennial Solar PID Tester is used to evaluate possible performance degradation of photovoltaic modules during actual operation. This article will introduce the main factors that produce the PID effect of photovoltaic modules to help better understand and prevent this problem.

Hot spot effect

The hot spot effect in the module means that under certain conditions, a certain series branch in the module is blocked. Not only can it not generate electricity, but it will also be used as a load to consume the energy generated by other illuminated modules; it will not only reduce the power of the module The total power generation will also cause the shaded parts to heat up, thus affecting the module efficiency. The hot spot effect can be caused by a variety of factors, including bright light, high electrical current, and poor ventilation. The hot spot effect can cause reduced power output, shortened service life and permanent damage to components, and may even lead to fire. The hot spot effect in a battery can cause PID when the temperature of the hot spot is high enough to cause a voltage difference between the battery and the module frame. The figure below illustrates the impact of hot spots on components: when the temperature of the hot spot reaches 66.2°C, compared with the adjacent area without hot spots (30.9°C), the hot spot effect will lead to further degradation.As a result, the output power of the component decreases, cause permanent damage.

Figure 1. Photovoltaic module with hot spot effect

Several approaches can be taken to mitigate the hot spot effect in PV modules:

1. Design with proper ventilation: Ensure there is enough airflow around the photovoltaic modules to help dissipate heat.

2. Use materials with high thermal conductivity: such as aluminum to dissipate heat more effectively.

3. Use solar cells with low thermal resistance: hot spots are less likely to occur.

4. Install sunshade devices: such as blinds or reflectors to reduce the amount of direct sunlight reaching the module.

5. Active cooling system: such as fan or water cooling.

Shadow occlusion

Shadow occlusion is also a common problem in photovoltaic systems and has a significant impact on module performance. The blocked area cannot effectively generate electricity, resulting in a voltage difference, which leads to the generation of PID. Research has found that occlusion will significantly increase the possibility of PID occurrence, especially when the occlusion is severe or occurs for a long time. Another study found that shading can lead to hot spot PID and light-induced degradation (LID), with LID being more likely to occur in cells that have been shaded for extended periods of time.

When the photovoltaic module is permanently shaded, it may cause the bypass diode to be inactive, resulting in a short circuit of the module and a reduction in output power generation, as shown in Figure 2. During the EL test, the inactive bypass diode caused the module to lose three One-third of the power.

Figure 2. PV module with inactive bypass diode due to permanent shadowing

Crack

Cracks refer to cracks or breaks in solar cells, as shown in Figure 3. Cracks can be caused by a variety of factors, including mechanical stress, thermal expansion and contraction, and environmental factors such as extreme temperature fluctuations or humidity. Cracks can cause problems such as reduced power output, reduced efficiency, shortened lifespan, or even complete failure.

Figure 3. EL image of solar cell affected by cracks

To prevent cracks and mitigate potential damage, consider the following:

1. Design photovoltaic systems with crack resistance in mind, using materials and designs that are not prone to cracking, such as flexible cells or reinforced materials to increase the strength of the battery.

2. Properly sealed and protected from damage caused by environmental factors such as extreme temperatures, humidity, and ultraviolet radiation.

3. Perform regular inspections and maintenance to find and solve potential problems before they become serious.

Figure 4. Relationship between solar cell temperature and crack size (%)

Red indicates that the crack size has a significant impact on the temperature of the solar cell (>30°C), blue indicates that the crack has no significant impact.

PID Tester

E-mail: market@millennialsolar.com

Introduce:

Long-term leakage current will cause changes in the state of the cell carriers and depletion layer, corrosion of the contact resistance in the circuit, and electrochemical corrosion of the packaging materials, resulting in cell power attenuation, increased series resistance, and reduced light transmittance. , delamination and other phenomena that affect the long-term power generation.

Fulfill the standard:

IEC61215-MQT21; IEC62804

Features:

•The frame end of the module is grounded, which not only simulates the actual situation, but also prevents potential dangers caused by high voltage on the frame;

•Each channel is independent of each other, and the voltage size, polarity and time of multiple channels can be set independently;

•Multiple voltages, leakage current, and insulation resistance are displayed simultaneously;

•Real-time monitoring of voltage, leakage current, and insulation resistance curves;

As an important tool for evaluating module performance, PID Tester plays an important role in the design, production, operation and maintenance of photovoltaic systems. By predicting the long-term stability of photovoltaic modules under different conditions, we conduct comprehensive, in-depth and scientific testing of the modules as a basis for quality assurance and selection of photovoltaic modules. By better utilizing this equipment, we can optimize the performance of the photovoltaic system and improve system reliability and efficiency promote the development of clean energy.