Precautions from large bases to distributed photovoltaic power plants

The photovoltaic industry is ushering in a new round of development cycle that is changing with each passing day. Under the big wave of carbon neutrality goals, new energy represented by photovoltaics and wind power is becoming the main trend in the low-carbon era, and 2021 will set a new annual installed capacity. Records, new energy has entered a promising period of strategic opportunities.

On the one hand, in the face of a new era of development, from the complementary multi-energy forms in the wind and Everbright base projects to the promotion of distributed photovoltaics throughout the county, photovoltaic power plants are developing more diverse application scenarios. But at the same time, the rise in the price of photovoltaic supply chain in the past two years is also affecting the investment rate of return of the industry. How to continue to reduce costs and build safe and reliable photovoltaic power plants is becoming a new challenge for the development of the industry.

Multi-scenario application: the challenge of cost reduction and security

As the installation environment of photovoltaic power plants becomes more and more diverse, whether it is the climate characteristics of high temperature and high ultraviolet radiation in arid areas, or the high humidity and high heat scene on water surface and humid areas, the new development trend puts forward the reliability and safety of photovoltaic product technology. higher standards and requirements. It is especially worth noting that, compared with ground-based power plants, rooftop distributed photovoltaic power plants take on more serious risks. Due to the high operating temperature and high reflectivity of roof components, it is easy to cause hot spots, and there are many cases of fires in rooftop photovoltaic power plants at home and abroad.

As a distributed photovoltaic power station involving thousands of households and all walks of life, the importance of safety is self-evident. "From an investment point of view, the safe operation of photovoltaic power plants is the top priority. Once an accident occurs, it is not only a matter of property loss, but also life-threatening, especially for rooftop photovoltaic power plants. Safety is the bottom line." A veteran in the field of power station investment said.

Another person who has been engaged in the operation and service of photovoltaic power plants for many years added, "The safety of power plants is definitely a problem that cannot be ignored. Paying attention to the reliability and safety of products is also a problem that the industry must face when it moves towards high-quality development."

In fact, safety and reliability are also an important means of reducing the cost of photovoltaic power plants. In the 25-year operation cycle of photovoltaic power plants, under the premise of ensuring safe operation, reducing the risk of power generation reduction due to product or system problems is the main way to reduce costs throughout the life cycle.

Power station risks cannot be ignored

Among the factors affecting power generation loss, snail patterns and backplane defects are the top five in maintenance costs. As the "copper wall and iron wall" of photovoltaic modules, although the backplane exists as an auxiliary material in the photovoltaic industry chain, its role cannot be underestimated. Once the backplane has cracks, yellowing and other problems, it will not only directly affect the power generation of the battery module, but also cause serious problems such as fire.

In fact, the risk problems brought by the backplane have also repeatedly appeared in large-scale power station applications, including the once-popular 3A backplane, etc., which have been eliminated from the market under the risk of outdoor applications. In recent years, driven by cost reduction, the photovoltaic industry is continuing to explore new backplane technologies, and PET backplane is one of the routes.

In fact, many component manufacturers including Japan and China have successively abandoned this technical route after trying to use modified PET polyester backsheets. According to relevant professionals, the outdoor aging mechanism of PET is mainly photo-oxidation. Under the combined action of ultraviolet light and temperature and humidity, PET absorbs ultraviolet light and undergoes Norrish degradation, and the molecular chain is broken near the ester group, which leads to the decline of mechanical properties and yellowing.

Figure 1

The aging mechanism of PET determines its actual performance in household applications. Figure 1 shows a photovoltaic power station located in Inner Mongolia. The power station uses PET backsheets. After 4 years of operation, nearly 40% of the module backsheets are seriously yellowed. , more than 10% of the modules’ backplanes are foamed and delaminated, and 1-5% of the modules have hot spot problems; the monocrystalline modules in Figure 2 are distributed photovoltaic power stations installed on the metal corrugated roofs of commercial buildings. The material is PET, and the yellowing of the backplane is visible to the naked eye. The most serious area is the edge of the module array. The b* value is as high as 27. Ultraviolet rays accelerate the edge aging of the backplane, which further causes the outer layer of the backplane to crack and become brittle.

Figure 2

It was learned from the technical person in charge of a head component company that pure PET backsheets have not yet been used in the components shipped by the company. It is suitable for high-temperature, high-humidity and high-ultraviolet environments, and the reliability of pure PET backsheets has not passed the relevant requirements.”

The photovoltaic industry is facing the transition from extensive development to high-quality development. Whether it is the development needs of the industry itself, or the increased risk boundary caused by photovoltaic cross-border, the use of efficient and reliable materials has become the "bottom line" of the industry. It is an important means to realize the safe operation of photovoltaic power plants and further reduce costs