Science and Technology Daily News (reporter Wu Changfeng) Reporter learned from the University of Science and Technology of China, the school of engineering professor Pei Gang and the National Synchrotron Radiation Laboratory researcher Zou Chongwen team, proposed a new method of energy utilization, the method to the sun and space as heat source and cold source, The spectral adaptive intelligent coating is cleverly used to solve the spectral conflict between the photothermal conversion process and the radiation refrigeration process, and to realize the capture and utilization of cold and hot energy 24 hours a day. The relevant research results were recently published in the international journal "Proceedings of the National Academy of Sciences".

From a thermodynamic point of view, the sun and space are the ultimate heat source and the ultimate cold source of the Earth's energy cycle. Photothermal conversion obtains high temperature heat energy through direct utilization of solar radiation. The sky radiation refrigeration can directly emit the surface energy in the form of infrared radiation through the atmospheric window to the low temperature space, obtain the low temperature cooling capacity, and realize the ultra-long distance direct utilization of deep space low temperature. However, the current photothermal conversion and sky radiation refrigeration rely on static spectral selective coating, but the two processes have infrared spectrum conflict, and the current technology is the use of a single target, a single function.

Based on this, the research team innovatively proposed to use the spectral adaptive regulation mechanism to decouple the time of solar heat source and space cold source, breaking through the current single utilization of solar heat source and space cold source. A multilayer photoselective adaptive coating based on vanadium dioxide phase change material was developed. The coating was in a metallic state under solar irradiation during the day. The overall solar absorption rate of the coating was 0.89, and the infrared emissivity was only 0.25, showing the characteristics of photothermal absorption. In the insulating state at night without irradiation, the coating has a high emissivity in the atmospheric window band and a low emissivity in the rest of the mid-infrared band, showing the characteristics of radiation refrigeration. The measured results show that the surface temperature of the device can be 170℃ higher than the ambient temperature during the day, and 20℃ lower than the ambient temperature at night. It has the adaptive functions of daytime photothermal conversion and night radiation refrigeration. The device can operate 24 hours a day, greatly improving the overall efficiency of hot and cold energy capture.

The research results provide a new approach for energy capture and efficiency utilization based on solar heat sources and space cold sources, which can be widely used in building energy conservation, photovoltaic cooling, thermoelectric conversion, and deep space exploration.

Source: Science and Technology Daily (05 Apr 27, 2022)

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