Policy favorable thin film photovoltaic technology advantages

Recently, the reporter learned from a number of photovoltaic industry sources that this year's domestic photovoltaic industry will gradually return to strength, the second half of this year, the latest next year, the photovoltaic industry will improve. According to reports, in fact, many factories have already restarted.

Benefits of thin-film batteries At the end of last year, the Ministry of Finance and the Ministry of Housing and Urban-Rural Development issued the "Notice of the 2012 Solar Photovoltaic Building Demonstration Project" (hereinafter referred to as the "Notice"), and proposed an optoelectronic integration project that closely integrates building materials and building heights. The subsidy standard for this year is tentatively set at 9 yuan per watt, which is an increase of 3 yuan over the previous year. For the combined form of general use with buildings, the subsidy standard is tentatively set at 7.5 yuan per watt.

"Thin-film photovoltaic cells are very useful in the BIPV (bio-integrated photovoltaic) field. From the aspect of characteristics, thin-film photovoltaic cells are more convenient to install in buildings," Xu Zheng, director of the Institute of Photonics Technology at Beijing Jiaotong University, told the reporter.

Xu Zheng believes that crystalline silicon cells have high conversion efficiency and are suitable for large-scale photovoltaic power plants. However, the technical characteristics of thin-film batteries are more suitable for building applications. Therefore, there is more space in BIPV. "Do not oppose the film and crystal silicon. In the future, they will be a coexistence rather than a substitute situation." Xu Zheng said.

According to the brief introduction of the vice president of the China New Energy Chamber of Commerce and the marketing director of Hongwei Technology Co., Ltd., currently, crystalline silicon technology is the mainstream in the photovoltaic industry, which accounts for a very high proportion. The development of the film has a wave-like process. At the time when silicon was relatively expensive, many people put thin-film batteries. With the recent decline in silicon, everyone has a different view of thin-film batteries. The cost of crystalline silicon cells is now very close to that of thin-film batteries, which has dropped to 6 yuan/watt, but the conversion efficiency is much higher than that of thin-film batteries.

Future Development Advantages Zhao Lei, associate researcher at the Institute of Electrical Engineering and Technology of the Chinese Academy of Sciences, believes that crystalline silicon cells will continue to dominate for a short period of time. However, in the long run, the development prospect of thin films will be much higher than that of crystalline silicon.

“At present, the efficiency of crystalline silicon can reach 17%-18%, the ultimate efficiency of a single cell is 29%, and the current laboratory can achieve 25%, so the efficiency of crystal silicon has limited room for improvement. In theory, the limit of the thin film The efficiency is also the same as crystalline silicon, which can reach 29%, and the current efficiency is only about 10%, which means that the conversion efficiency of the film still has a lot of room for improvement.” Zhao Lei told reporters.

Concisely believes that the conversion efficiency is not equivalent to the amount of electricity generated. "The photovoltaic cell conversion efficiency we are referring to generally refers to the efficiency under standard conditions. Under the standard conditions, the conversion efficiency of the thin film is lower than that of crystalline silicon. However, many industry reports It is shown that the actual capacity of thin-film batteries with the same capacity in one year is higher than that of crystalline silicon. In our experiment in Dongguan, we found that the same wattage of thin-film batteries generates 8%-10% higher power than crystalline silicon.

However, in addition to conversion efficiency, thin-film technology is still being questioned by some people in the industry. Some industry players believe that thin-film batteries have large attenuation, occupy a large area, and have high technology costs. In this regard, it is pointed out concisely that the product characteristics of the film are greatly attenuated at the beginning, but after 600 hours, the attenuation is relatively stable, similar to that of a crystalline silicon battery. “General thin-film battery manufacturers take attenuation into account before they leave the factory, for example, a battery of 130 watts, and manufacturers generally sell at 100 watts, deducting the amount of attenuation in advance.”

The conciseness of the high cost of thin film technology is attributed to the fact that thin film battery equipment mainly relies on imports. Concisely believe that after the equipment is domesticated, “the thin-film battery industry chain is very short and one workshop can be completed. In the future, to achieve parity Internet access, the advantages of the film will be obvious. In the future, the thin film power generation cost can reach 0.3 US dollars per watt. Less than 3 dollars."

However, large floor space is a hurdle for thin-film batteries. For large-scale photovoltaic power plants, the biggest disadvantage of thin-film batteries is their large footprint. Relevant data show that the efficiency of 14% of the photovoltaic modules in the standard sunshine output per square meter rated 140 watts, in order to calculate, to achieve the same capacity, the area of ​​the thin film battery is inversely proportional to its conversion efficiency.

“From a technical point of view, if we want to increase the efficiency of thin-film battery conversion to 12%, and even further increase it to 15% and 16%, then the cost will drop very much. However, this difficulty is very large.” Zhao Lei said that despite this, With the development of technology, crystalline silicon will surely be replaced by thin films in the long term. Due to the low pollution of the thin film technology, low energy consumption and higher power generation, the crystalline silicon can dry in the future, but the thin crystalline silicon can be dry. No."

BIPV applications should be suitable for building materials demand At present, it is not realistic for thin-film batteries to replace crystalline silicon batteries, but as experts say, the advantages of thin-film batteries in BIPV are even more obvious. Concisely believe that even if it is a rooftop solar photovoltaic system, the choice of crystalline silicon or thin-film solar cells depends on policy changes. “The general view is that crystalline silicon is mainly used for roofs. However, due to policy changes in some countries, there are many films on the roof. Germany adopts a policy of encouraging more electricity, and users use electricity to generate electricity to make money, so they prefer to use crystalline silicon, but Australia encourages self-use, and the government subsidizes each household within 1,500 watts. Users tend to use low-cost thin-film batteries."

For "photovoltaic integration projects in which building materials and other structures are highly integrated with building height," because thin-film batteries are less sensitive to installation angles, they are more adaptable to architectural design requirements and are therefore more advantageous. Xu Zheng pointed out that the need for thin-film batteries to be truly suitable for building materials must meet the requirements for the installation and design of building materials, such as safety and fire resistance, before they can be installed on buildings. At present, some building photovoltaic specifications have been drafted.

“There are many architects and designers who did not recognize the use of thin-film batteries in buildings. How to integrate thin-film batteries into design and architecture is not only for batteries but also for architecture. It is a process of learning from each other to combine films with construction materials and design, "said Xu Zheng.