Portable EL Detector for PV Modules

When selecting components for a Portable EL (Electroluminescence) Detector, key factors such as detection accuracy, portability, imaging quality, and applicable scenarios should be prioritized. Fengtu’s Portable EL Detector performs exceptionally well. Taking the FT-EL3 model as an example, it is based on advanced electroluminescence principles, equipped with a high-resolution imaging system and professional optical lenses, achieving a detection accuracy of the micrometer level. The 24.76-megapixel high-definition infrared camera ensures extremely clear EL image quality. The detector is fitted with a full-time auto-focus module, further enhancing imaging precision. The entire device supports wireless remote operation; when paired with a program-controlled constant current power supply, it can conduct non-stop testing for 24 hours. It also comes with an energy storage power supply for easy use, making it suitable for quality inspection scenarios in various photovoltaic (PV) power plants and PV modules.

In the field of photovoltaic power generation, PV modules are the only components that generate electricity without the need for rotation. However, to cut costs, PV module manufacturers continue to reduce the thickness of PV modules, which directly weakens the mechanical damage resistance of solar cells. This leads to frequent occurrence of microcracks in modules during transportation and installation. Another issue is that PV power plants using flexible brackets face the risk of large-area microcracks in modules when encountering extreme weather such as typhoons. Therefore, microcrack detection has become a key link in the operation, maintenance, and acquisition of existing power plants. The electroluminescence detection method is a simple and effective way for microcrack detection, and the Portable EL Detector for modules is developed based on this principle.

The semiconductor PN junction is the core of a solar cell. Without external stimuli such as light, voltage, or temperature, the internal PN junction maintains a dynamic equilibrium, with a relatively stable number of electrons and holes. When a voltage is applied, the internal electric field of the semiconductor weakens. Electrons in the N-region move toward the P-region and recombine with holes in the P-region (alternatively, this can be understood as holes in the P-region moving toward the N-region and recombining with electrons in the N-region). During this recombination process, energy is released in the form of light—this phenomenon is known as electroluminescence.

When a forward bias voltage is applied to a crystalline silicon solar cell, it emits infrared light with a wavelength of approximately 1100 nm, which is invisible to the naked eye. The Portable EL Detector for modules is equipped with a CCD camera that can accurately capture these photons. After transmitting the signals to a computer for processing, the detection results are presented in the form of images. During detection, after a voltage is applied to the crystalline silicon module, the more electrons and holes recombine, the denser the photons, and the brighter the EL image. If a certain area is dim, it indicates fewer recombinations and defects in that area. If an area is completely dark, it means either no recombination has occurred or the light is blocked, preventing signal capture.

For operational PV power plants, random sampling detection is usually adopted: first, a drone conducts a comprehensive inspection to identify abnormal strings and areas, and then the Portable EL Detector for modules is used for detection at night. Currently, such detectors are mainly available in handheld and drone-mounted types, which can be selected according to actual needs. However, in "flexible bracket + crystalline silicon cell" power plants, PV module microcracks are relatively common. Conventional drone-mounted visible light and thermal imaging equipment cannot detect microcracks, so the Portable EL Detector for modules has become the core device for microcrack detection in such power plants.