1, the concept of attenuation of photovoltaic components
The attenuation rate of PV modules refers to:
After a certain period of operation of a PV module, the ratio of output power to nominal power under standard test conditions (AM1.5, module temperature 25 ° C, irradiance 1000W / m2).
According to national regulations:
Monocrystalline components decay of not more than 3% in the first year, polysilicon components decay of not more than 2.5% in the first year, not more than 0.7% per year thereafter.
2, the type of attenuation
Attenuation is generally divided into the initial photo-induced attenuation and aging attenuation.In addition, PID potential can induce attenuation in recent years have also been recognized.
1) Light Induced Degradation (LID)
The essential reason for the LID generation is that the solar cell produces a recombination center within the material after it receives light and it is generally acknowledged that the boron-oxygen complex generated after illumination reduces the lifetime of the minority. The deep-level defect caused by the gap oxygen excited under illumination causes the carrier recombination and the degradation of the battery performance, causing the output power of the photovoltaic module to decline sharply a few days after the initial application. However, for a period of time Month) output power will gradually stabilize.
2) Aging decay
PV modules appear in the long-term application, slow attenuation, can be divided into two categories:
1) The decay caused by the aging of the battery itself is mainly affected by the battery type (single crystal, polycrystalline) and the battery production process;
2) The decay and decay rate caused by the aging of the packaging material is positively related to the production process of the PV module and the environment of the encapsulation material and the component application, among which common cracking, yellowing of the appearance, sand abrasion, hot spots and component aging can accelerate the power attenuation .
3) PID potential can induce attenuation
This loss of high voltage present between the internal circuit of the module and its grounded metal frame can cause component power degradation and is also related to glass, backplane, EVA, temperature, humidity and voltage.
Conventional components of the attenuation shown in the following figure.
In the figure, the blue line is the attenuation curve of the monocrystalline silicon module, and the red line is the decay curve of the polycrystalline silicon module, in which:
Monocrystalline silicon components due to LID effect is obvious, within 2 months, the rapid decline in power photovoltaic components, the late recovery will be slow.
Polysilicon components also have a LID effect, but cause significantly less attenuation than single crystals.
Over 1 year, mainly due to the "aging decay" caused by the power reduction.
The picture below shows the PID effect of the infrared photos, PID effect of serious cell black.
The PID effect can cause a significant drop in component power.
