How to increase the PV system power generation To reduce the LCOE (cost of electricity), in general, I think there are three directions to work hard: high-efficiency components, high-reliability components, and intelligent components. My report will simply share with you from three aspects.
High-efficiency components, including the development and application of high-efficiency batteries, are at the heart of the technology. Here is a summary of the world's highest battery efficiency record for various solar cell technologies. These results are very clear to everyone. I will not elaborate on them anymore. These records reflect the potential of various battery technologies.
Currently, PERC batteries have begun to enter the stage of industrialization. Let's take a look at the research process of PERC battery technology. From 2010 to 2014, we included a number of research institutes and corporate R&D teams in Europe and Asia to do a series of laboratory research on PERC batteries. As early as 2012, many The agency has already experimented with lab efficiency where the efficiency of large-area PERC batteries reaches more than 20%. It laid the foundation for the industrialization transfer.
In 2014, Trina Solar's National Key Laboratory developed a single-crystal 156-performing PERC cell with a 21.4% efficiency. In 2015, SolarWorld announced that its PERC cell efficiency reached 21.7%. This is a new record.
The industrialization of PERC batteries has been scaled up by first-tier companies in Taiwan and China. The production level of PERC battery efficiency is around 20.4% on average. The efficiency of the battery continues to be optimized and the scale is increasing rapidly. In the updated version of the most authoritative world’s highest battery efficiency map released by NREL in May and June of this year, the first record of the world’s record of the multi-crystal PERC battery efficiency developed by Trina Solar in 2014 was 20.8%, which was updated in 2004. The Fraunhofer ISE developed a 20.4% record for a small area polycrystalline PERC battery.
In addition to PERC batteries, Trina Solar is also working on the development of more efficient solar cell technology processes, such as IBC, HJT batteries, and others. Raising the power generated by a component system can be considered in terms of the optical performance and electrical performance of the battery, components, and system. Here I have listed several directions. For example, on the assembly side, the optically optimized solution includes the development of a converging ribbon, and the electrical optimization includes the development of a low resistance welding technology process. The temperature coefficient and operating temperature of the system are all factors that affect the actual power generation. Below I will give examples of the impact of various major factors on high-efficiency power generation and solutions.
The low LCOE mainly depends on three factors: high efficiency, high power generation, and low cost. Here I give an example. For a 10MW project, the efficiency increase of 0.25%, equivalent to a power increase of about 5W, can reduce the cost of BOS by about 0.8%, which is about 2-3 cents. An important factor in the improvement of efficiency is the temperature coefficient, the high pressure of the battery, and the low temperature coefficient. This compares the effect of common pressure, PERC battery, and IBC battery on the temperature coefficient due to different pressure and the ultimate power generation. influences. Therefore, the development of high-efficiency battery, the increase of battery pressure, the benefit of lowering the temperature coefficient, and how to effectively reduce the operating temperature of the system are factors that need to be considered.
Here we did a simulation of the component's operating temperature distribution model. In addition, under low-irradiation conditions, we have calculated the actual conditions of the power generation of various batteries and found that IBC batteries have the highest power generation under low irradiation conditions of 200 W per square meter. Dr. Xu also introduced just now that high-quality single-crystal batteries have better low-irradiation performance. We can see that, taking the climatic conditions in Changzhou as an example, we have made comparisons between common polycrystalline components and high-efficiency components in terms of temperature coefficient, operating temperature, low-irradiation, LID, etc. About 2% advantage.
Photovoltaic module and system reliability issues
Many problems with the reliability of photovoltaic modules are critical material issues. For example, yellowing and delamination of EVA, cracking of the backplane, yellowing of the ribbon, etc., and aging of the material after long-term use of the module. With regard to the perennial attenuation of the power of components, the NREL of the United States has a statistic, which attenuates approximately 0.7% per year. This is already a consensus. Trina Solar also tested the power attenuation of its own components. From the component data of 2008, it was within the attenuation rate of 0.7%. The internal reason of power attenuation, short-term attenuation is mainly related to the battery, mainly PID, LID attenuation.
The long-term decay mainly comes from the packaging materials, causing black spots, black lines, backplane cracking and other reliability problems. After the material ages and causes EVA delamination, water penetration occurs due to cracking of the backsheet. The pattern of short-term and long-term failure is not the same. For example, PID attenuation can be more than 30%, and some even as high as 70% attenuation. Common component failure modes, we made a classification and incidence. Hot spots, cold freezing, and damp heat are the main causes of component failure. There is data analysis of this TUV China certified component, and NREL in the United States also has analysis data. Hot spot problem, here is a flowchart of the failure mechanism, blocking the local high temperature caused by the battery, reverse bias and leakage current caused by bypass diode heating, is the two key failure modes, the final component may be burned.
In terms of component system reliability research, the United States NREL, Japan AIST, Germany Fraunhofer and other agencies are actively conducting internationally. China is also actively participating in this research. For example, the study of the PID mechanism has been established as a national 863 project, and Yingli and Tianhe jointly undertake the research. For the high-humidity, high-reliability component products, we have proposed a solution for the double glass component. Because of the weather resistance of inorganic materials glass far better than polymer backplanes; glass impervious, better protection of the battery under high temperature and humidity; components are not grounded, the advantages of better resistance to PID performance. For thermal shock resistant components, we believe that using conductive film materials can improve performance. In the past, there was no promotion due to the high cost of conductive films. Just now we listened to expert reports in the morning, and the localization of conductive films is promising. If it can be widely adopted, it will be beneficial to the thermal shock resistance of the components.
Intelligent components
In the third aspect, I would like to briefly talk about intelligent components. We are concerned that the short-board effects of component mismatches actually occur only when the mismatch is severe. This figure shows that the greater the fill factor FF is, The effect of the short board failure is obvious. Intelligent components need to be optimized step by step, mainly including string or centralized optimization, component-level power optimization, and sub-string power optimization. In several stages, due to cost factors, they need to be developed and applied separately. Here an IV curve of the power of the optimizer and the normal component without optimizer is made in the case of 50% irradiation blockage, and the maximum output power difference is very large. The maximum can reach 20% difference.
There is also an easy-to-install component structure design that is one of the solutions to reduce the cost of electricity. We can see that this is our traditional component and we can see that we will face many problems. Then if we integrate the mounting bracket with the components, it is very convenient. It can be installed quickly, reducing installation costs and reducing the load on the roof. Does not damage the roof waterproofing. This is the design of easy-to-install components and is one of TRW's products.
Some experts have studied the optimal inclination of the components. Worthy of attention and need systemic calculations. The optimum inclination design of the components of the distributed system installation needs to consider the roof cost, such as the rent per unit area, area, and other parameters. Here is given a simulation and formula that can calculate the optimal inclination design for a specific situation, and even allow a bit of occlusion, find the maximum power generation, and find the lowest cost design.
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