High-efficiency products and distributed PV systems are the two major focuses in the PV industry. As distributed system becomes a mainstream, high-efficiency products with lower generation costs and higher power outputs will be in the spotlight as well. Currently, PERC technology is one of the high-efficiency cell technologies that has been widely accepted and commercialized. Thus, N-type and perovskite cells will become the next popular items. Photonics Industry and Technology Development Association (PIDA) especially organized a PV seminar, discussing the global PV market trend, high-efficiency products, and residential system equipments.
The PV seminar, organized by Gintech’s chief technology officer Walt K.W. Huang, is divided into four parts. The PIDA analyst, Jianhan Lin, first talked about the current global PV market status, pointing out that China, Japan, and US are still the main markets and Europe’s installation may continue to drop. What’s worth paying attention to is that the increased demand for distributed PV systems in China and US will stimulate the market development, boosting the demand for micro inverters and energy storage systems further. Therefore, PV manufacturers can put more effort on high-efficiency cells/modules that used in distributed systems in the future.
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Potential options for high-efficiency cells
During the seminar, Inventec R&D manager Jung Wu Chien, briefly explained the meaning, characteristic, and limitation of Passivated Emitter and Rear Cell (PERC). The core of PERC is through passivated emitter and rear cell technology, it can improve the structure of the rear side of the cell and hence increase power efficiency. Inventec’s PERC cell efficiency is expected to increase to 20.4% this year. Since it’s easier to implement PERC than N-type technology, PERC has become a mainstream for Taiwan cell manufacturers.
Although PERC has its advantages, it has some issues such as Light Induced Degradation (LID). The P-type PERC cell efficiency after sunlight exposure will have such problem, and the higher the rated efficiency, the greater the LID. The new furnaces released by equipment manufacturers may be one of the solutions for LID, but the actual result is yet to be verified by cell manufacturers. Aside from PERC, N-type cells, mono-si wafer size enlargement, and the increased number of bus bar are the other options to raise cell’s final output wattage. On the other hand, the dual N-type cell that’s being researched by Inventec has reached an efficiency of 21.6% and may increase further in 2015. Meanwhile, Sharp and other manufacturers have begun to invest in HIT+IBC back electrode technology to raise their conversion efficiency to above 25% despite the high R&D cost.
Furthermore, the professor from the department of photonics of National Cheng-Kung University, Tzung-Fang Guo, announced another high-efficiency cell option – perovskite cell. Perovskite is referring to a special chemical structure with semiconductor property and that organic and non-organic compounds overlap. This type of material has high light absorbability and good transportability. In fact, it has become a hot topic in the academic field since 2009. The highest conversion efficiency has almost reached 20% and is still increasing.
However, precise temperature control is essential for perovskite cell to be packaged into a flat and light module film. Also, how perovskite cell contains lead and its weaker structure stability in comparison with silicon cells are the problems that are yet to be solved. Professor Guo indicated that P-type perovskite cell efficiency is about 7%-9%, which already has the potential to be commercialized. If its organic structure can be replaced by non-organic compounds and let go of the lead issues, it may be more stable and able to go commercialization.
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Residential PV
The purpose of high-efficiency products is to reduce cost per watt for better profits. If generation costs can be at the same level as market prices, solar PV will be a truly competitive energy option with much potential to grow.
After many years of development, PV market has been through a revolution from utility-scale power plants to distributed systems for commercial and residential uses. Consequently, suitable inverters have been developed as well. Zuxiang-Ti Zhang, the project manager of I-ENERGY, shared its residential micro inverters. These inverters are different from string inverters and can be installed on individual module. It’s suitable for residential users because of the following reasons – low construction difficulty, less impact from shading, cheaper installation cost per watt, and shorter payback period. The company offers a full package with monitoring systems to form a smart residential energy solution.
According to SEIA’s research, the amount of US residential system installation has officially exceeded US commercial system installation in 2014. In the meantime, China has significantly raised its installation target for distributed systems since 2014 and came up with many beneficial policies. All of these prove that global PV market is entering the new era for distributed systems, and thus high-efficiency products will be the key in this new era.
Photo Source: PIDA