With the rapid development of new energy, the installation of photovoltaic (PV) systems has been setting new records year after year over the past three years, achieving remarkable results. As the core component of solar power systems, PV modules are used in vast quantities. However, in recent years, some PV power stations have experienced incidents of PV module cracking during operation, significantly impacting the safety and investment returns of the systems. According to field investigations by the Renewable Energy Test Center (RETC) in the United States, several large-scale utility PV projects with capacities ranging from 100MW to 300MW have reported spontaneous glass breakage rates of 2% to 5%. Taking a 1MW PV power station as an example, it requires approximately 1,724 modules of 580W each. Even at the minimum breakage rate of 2%, this translates to about 34 damaged modules. Such a high breakage rate was almost unheard of in the past. So, why has it increased instead of decreasing with the advancement of technology?
1.Material Defects or Aging
The main materials of PV modules include photovoltaic glass, EVA encapsulant, backsheets, and silicon wafers. If there are quality defects in these materials during production, such as insufficient glass strength or aging EVA encapsulant, it may lead to cracking or even bursting of the modules during operation. Additionally, PV modules are exposed to natural environments like sunlight, wind, and rain for long periods, leading to gradual material aging. Extreme weather conditions, such as prolonged high temperatures or cold, can accelerate this aging and performance degradation, causing cracks or bursts in the modules. Normally, modules should pass environmental endurance tests like damp heat testing, UV aging testing, thermal cycling testing, and humidity freeze testing. With the intense price competition in the PV module market, are the quality standards of modules being met? What is the pass rate?
2.Hot Spot Effect
The hot spot effect is a common cause of PV module cracking. When a certain area of the module surface is unable to generate electricity effectively due to shading, pollution, or dust accumulation, it becomes a power-consuming area, leading to a significant temperature rise in that localized region, forming a hot spot. Prolonged high temperatures can cause excessive stress in the materials, leading to uneven forces that may result in glass or silicon wafer cracking. Additionally, in double-glass modules, the lack of heat dissipation and the presence of bypass diodes can easily lead to glass self-explosion due to localized high temperatures.
3.Excessive Mechanical Stress
During the installation and use of PV modules, they may be subjected to external forces such as stepping, flying stones, sharp metal impacts, wind loads, and snow loads. (Normally, modules should theoretically pass mechanical load testing and hail impact testing.) If the module design or installation is improper, leading to localized stress concentration, the glass or internal structure may not withstand the pressure, potentially causing cracking. This is particularly evident in mountainous areas or regions prone to strong winds and heavy snow.
Moreover, the pursuit of higher power generation without proper walking and maintenance channels means that construction and management personnel often walk on the module surfaces or between module frames, transferring most of the foot pressure directly to the glass surface, causing a large number of micro-cracks. These micro-cracks can later develop into hot spots, PID effects, and eventually lead to glass self-explosion.
4.Current Overload or Overvoltage
If the PV system is not properly designed or managed in terms of current and voltage monitoring, the modules may be subjected to excessive current or voltage surges, damaging internal materials and ultimately leading to module cracking.
5.Production Process Issues
During production, if the equipment is not precise or the processes are not up to standard, there may be defects in the module encapsulation process. For example, insufficient lamination, poor material bonding, or damaged silicon wafers may not be apparent initially but can manifest over long-term operation, potentially leading to module cracking. Normally, modules should pass mechanical performance tests like lamination testing and terminal pull testing.
6.Installation and Transportation Issues
Modules may be damaged during transportation due to bumps, drops, or improper handling. Additionally, improper installation of brackets, clamps, or other components can lead to uneven stress distribution, causing micro-cracks that may eventually lead to cracking.
7.Industry Competition and Cost Reduction Leading to Quality Decline
The extreme price competition in the industry forces companies to find ways to reduce costs and increase efficiency, such as increasing module size and power. However, the increase in size brings potential risks, making double-glass modules more fragile and less resistant to stepping. Excessive stress can easily lead to cracking and shattering!