Focus of the PV industry is shifting from scale, speed and price to quality, technology and returns.
In the current trend, centered on technology, it has become imperative for the companies to invest into technological R&D and innovation fields among others. As one of the leading photovoltaic companies, Trina Solar sticks to its traditional principles of taking the lead in technological layout in terms of mainstream technologies like MBB and high-efficiency IBC solar cell technologies among others.
Multi-busbar (MBB) technology: half-step ahead from others” and is not as easy as one thinks
High-efficient technologies, vigorously promoted by Chinese Top Runner Program, are ushering in the era of ultra-rapid development. Among various module technologies, MBB technology not only reduces the consumption of silver paste, which ultimately brings down the cost, but also increases light illumination area of cells to boost performance. Moreover, cells with denser bar lines have stronger subfissure resistance. All these advantages make MBB technology to stay at the forefront in the photovoltaic industry.
Though MBB technology is considered to the mainstream highly efficient technology in the industry, problems like equipment quality and yield rate, hinder the pace of shifting it from R&D to mass production. Even today, there is much room for improvement in equipment quality and yield rate. Consequently, the actual output of MBB cells had been relatively low before 2019. With the upgradation in technologies, an increasing number of companies started to combine half-cut technology with MBB since the beginning of 2019. This kind of combination improves short-circuit currents of modules and fill factors, further increasing the power of modules by 10W. It is expected that capacity will further witness remarkable increase this year.
This trend epitomizes the exhibits of module factories during PV EXPO held in Japan in February 2019. Following Trina Solar, many mainstream photovoltaic companies are adopting the model of integrating half-cut and MBB technologies.
As power supply is halved in half-cut cells, the design of bus bar and welding strip needs further optimization. Most half-cut MBB solar cells are 9BB cells. According to Zhang Shu, Senior R&D Manager and in charge of Trina Solar high-efficiency modules, "The number of bar lines in MBB depends on the balance between electrics and optics. More bar lines reduce series resistance and also lead to an increase in area of the shade. After integrating MBB and half-cut technologies, the number of bar lines is reduced to half-cut cell, which reduces the series resistance. According to simulation and experiment research, we found that the capacity of 9BB half-cut modules has increased to the highest extent compared with others."
As the pioneer of MBB technology, Trina Solar has always been taking the lead in R&D and mass production of MBB in the industry. As early as 2015, Trina Solar started its research on MBB as a reserve technology. It joined hands with other players to develop the first-generation round welding strip and first-generation MBB cell series welding equipment in China. Moreover, Trina Solar was also among the first to solve technical difficulties in round welding strip welding, including deviation prevention technology for round welding strip, 144-point independent elastic compaction technology, integrated welding technology combining series welding and convergence.
In addition to equipment, technological difficulty in processing was also blocking MBB from mass production. According to Feng Zhiqiang, Vice-President and Technical Director, Trina Solar, and Director of State Key Laboratory of PV Science and Technology of Trina Solar, “The major difficulties in MBB technology are I-V sorting of cells and series welding of module, including welding strip aligning, the quality of welding, welding temperature field control and welding tension control, among others. Besides, there is a need to strike a balance between electrical resistivity and the area of shade.
After two and a half years of devotion, Trina Solar began the trial production of MBB full cell in August 2017 and finally put it into mass production in November in the same year.
On March 21, 2019, Trina Solar launched four new product series, and achieved mass production of high-power modules by combining MBB with half-cut technology, as well as integrating PERC, dual-side among other mainstream technologies in the industry. As on date, the market share of Trina Solar MBB products is very impressive.
A total of 19 world records: Technological “accumulation” is needed for future development of the industry
“Trina Solar always sticks to the principle of ‘half-step ahead from others. Meanwhile, it also closely tracks the demand of the market”, said Mr. Yin Rongfang, Executive Vice-President, Trina Solar, said, when he was interviewed by media. “One can infer from the four newly launched product series that Trina Solar attaches greater importance to integrating mature mainstream technologies already existing in the market.”
In terms of R&D, Trina Solar works with an objective of trying to be completely different from those for mass production. The State Key Laboratory of PV Science and Technology set in Trina Solar is among the first batch of state key laboratories accredited by Ministry of Science and Technology of the People’s Republic of China (MOST). It focuses on developing leading technologies including highly-efficient N-type and IBC technology.
In May 2019, Trina Solar set a new world record of 24.58% for a high-efficiency n-type mono-crystalline silicon (c-Si) i-TOPCon solar cell. The result has been independently confirmed by the ISFH CalTeC in Germany.
This is the 19th world record created by Trina Solar in the field of cell efficiency and module output power. This is also a testament to Trina Solar’s investment and achievement in technological R&D. Moreover, five of Trina Solar’s projects are on the project list of National Key Research and Development Project of China released by High Tech Research and Development Center, MOST in March 2019, including “Key Technology Research and Production Line Demonstration of Industrialization of High-efficiency N-type Bifacial Solar Cells of Homogeneous Monocrystalline Silicon”, “Key Technology for Industrialization of Decay-controllable N-type Solar Cells of Monocrystalline Silicon”, “Research on Design, Preparation and Mechanism of Perovskite/Crystalline Silicon Stacked Bifacial Solar Cells”, “Key Technology for Industrialization of P-type Solar Cells of Polysilicon Silicon ” and “Key Technologies and Demonstration of Multi-source Complementary Coupling Energy Supply System with Thermal and Electrical Energy Storage of Fully Renewable Energies for Featured Towns”.
“Trina Solar Laboratory’s R&D on cutting-edge technologies aims to explore technologies of next five to ten years. Our researchers started tapping into half-cut, MBB and big wafer among other existing technologies for several years before these technologies entered the market. In future, the competition in the photovoltaic industry will focus more on technological accumulation.” Mr. Yin Rongfang said.
Written by Lixia Rao from PV Men
Translated by Trina Solar
Smart Energy Solutions
delivered straight to your inbox