Two factors in photoinduced attenuation of photovoltaic modules

With the development of the solar photovoltaic industry, there have been some problems in the optical industry. Among them, the power attenuation of solar photovoltaic modules is large, and the impact on galvanized c channel power station operators and component manufacturers is relatively large. Component power attenuation refers to the phenomenon that the output power of the component gradually decreases as the photovoltaic component grows with the illumination time. Photo-induced attenuation and aging attenuation are an important factor in component power attenuation. Photo-induced attenuation refers to the phenomenon that the power of the solar cell is reduced due to the irradiation of sunlight. There are two factors in photoinduced attenuation of photovoltaic modules: initial photoinduced attenuation and aging attenuation.

1. Initial photoinduced attenuation. That is, the output power of the photovoltaic module is greatly reduced in the first few days of the initial use, but then tends to be stable. The main cause of this phenomenon is the boron-oxygen complex in the P-type (boron-doped) crystalline silicon wafer, which reduces the minority carrier lifetime. By changing the P-type dopant, replacing the boron with the crop can effectively reduce the photo-induced attenuation; or pre-illuminating the battery sheet, the initial photo-induced attenuation of the battery occurs before the manufacture of the photovoltaic module, and is related to the cell manufacturer. Therefore, when choosing a solar panel manufacturer, we must choose a strong manufacturer to supply.

2. Aging decay. In the long-term use, the extremely slow power drop occurs, which is mainly related to the slow decay of the battery and also to the degradation of the performance of the packaging material. Among them, the main reason for the degradation of the main material properties of the components is the irradiation of ultraviolet light. Long-term exposure to ultraviolet light causes aging and yellowing of EVA and backsheet (TPE structure), resulting in a decrease in light transmittance of the module, which in turn causes a decrease in power. Therefore, when selecting EVA and backplane, it is necessary to strictly control the materials, and it is necessary to select materials with good aging resistance to reduce the aging of the auxiliary materials and cause the power attenuation of the photovoltaic modules.

Photovoltaic modules are the most important equipment in photovoltaic power generation. If special circumstances occur during daily installation and operation and maintenance, it will cause hot spot effect of photovoltaic modules and potential induced attenuation effect (PID), causing losses for the majority of owners. Care should be taken to control the PV plant to avoid these two effects when installing and routinely maintaining the plant.

1, PID effect

The potential-induced attenuation effect is that the battery assembly has a long-term under high voltage, causing leakage current between the glass and the packaging material, and a large amount of electric charge is struck on the surface of the battery sheet, so that the passivation effect on the surface of the battery is deteriorated, resulting in lower than the design standard of the component. When the PID phenomenon is serious, it will cause the PV module power to attenuate by more than 50%, thus affecting the power output of the entire string. High temperature, high humidity, high salinity and coastal areas are most prone to PID phenomenon.

2, hot spot effect

The solar cell module that is shielded in a series branch will be used as a load to consume the energy generated by other illuminated solar cell components. The shaded solar cell component will heat up at this time, which is the hot spot effect. This effect can seriously damage the solar cell. Part of the energy generated by a solar cell with light may be consumed by the obscured battery. The hot spot effect may be just a piece of bird droppings. In order to prevent the solar cell from being damaged by the hot spot effect, it is preferable to connect a bypass diode between the positive and negative terminals of the solar cell module to prevent the energy generated by the photovoltaic module from being consumed by the shielded component. When the hot spot effect is severe, the bypass diode may be broken down and the assembly burned out.