Progress in research on resource recycling of waste photovoltaic modules in the urban environment
In response to the fossil energy crisis and climate change, the new energy industry represented by solar energy has risen rapidly. As of 2020, the global cumulative installed capacity of photovoltaics has reached 715GW, of which China’s installed capacity is 259GW, ranking first in the world for 7 consecutive years. However, the service life of photovoltaic modules is usually 25-30 years, so the huge installed capacity will inevitably lead to the generation of a huge amount of new photovoltaic waste, which contains heavy metals such as Pb and Cd that easily threaten the ecological environment and human health. At the same time, waste photovoltaic modules contain a large number of valuable resources, and the establishment of its recycling technology can not only realize the safe disposal of waste, but also realize the regeneration of secondary resources.
Based on the above background, the Clean Energy Technology and Carbon Materials Research Group of the Institute of Urban Environment, Chinese Academy of Sciences took crystalline silicon photovoltaic modules as the research object, and proposed a solvothermal swelling combined heat treatment method for module disassembly and recycling. The results show that the generation and accumulation of EVA decomposition gas during the heat treatment process is the main reason for the damage of the crystalline silicon wafer in the recycling process; the recycling system adopts the solvent thermal swelling method to pre-treat the photovoltaic module, which can realize the swelling and partial removal of EVA, thereby Establish a gas release channel; the combined heat treatment method completely decomposes and removes EVA, and the EVA decomposition gas escapes from the gas release channel. Compared with the existing recycling technology, the complete recovery rate of crystalline silicon wafers can be increased by nearly 10 times; when a specific solvent is used for solvothermal swelling treatment, it can also achieve rapid degradation of the fluorine-containing backsheet in the component, avoiding the traditional direct heat treatment process. The release of fluorine gas reduces secondary pollution. After testing, multiple performance indicators of recycled silicon wafers, including interstitial oxygen content, substituting carbon content, electrical resistivity, and minority lifetime, are similar to those of commercial silicon wafers.
Related research results were published in Chemical Engineering Journal with the topic of Nondestructive silicon wafer recovery by a novel method of solvothermal swelling coupled with thermal decomposition. The research was funded by the Chinese Academy of Sciences' Strategic Leading Science and Technology Project (Class A), the two fusion funds, the Fujian Industrial Guidance Project, and the Xiamen Science and Technology Plan Project.
Schematic diagram of crystalline silicon photovoltaic module structure and resource recovery process flow
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