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Advanced science: high efficiency solar selective absorption of black graphene

wallpapers News 2020-11-14

sun as the energy source of all living things on earth transmits about 1.72e17w of energy to the earth in the form of solar radiation which is nearly 9000 times of the current energy consumption of human civilization. Around the effective use of solar energy human beings have been carrying out a lot of explorations giving birth to many research fields such as solar thermal photovoltaic photochemistry. Solar photothermal conversion is a widely used energy conversion process. Almost all materials have a certain ability to absorb sunlight. After absorbing the light the materials convert the light energy into heat energy of internal lattice vibration electron collision. However the heat energy in the material is not easy to preserve the high-temperature material always dissipates the heat energy to the lower temperature environment through its own thermal radiation. By adjusting the surface spectral absorption properties of materials we can not only effectively absorb solar energy but also suppress the thermal radiation energy loss so as to maximize the use of solar photothermal conversion. This kind of surface optical energy material is called selective absorber (SSA). Since it was proposed by Israeli scientists in the middle of the 20th century SSA has been widely used in solar thermal utilization thermal photovoltaic thermoelectric other fields.

carbon based light absorbing materials (such as carbon black carbon nanotubes etc.) generally have high solar absorptivity (α solar > 0.90) which plays a key role in many fields of solar energy conversion utilization. However due to the high thermal emissivity (> 95%) these carbon based materials often cause huge energy loss which hinders the solar thermal conversion efficiency.

Dr. Cheng Huhu Professor Qu liangti of Tsinghua University first proposed a selective absorption membrane based on reduced graphene oxide (g-ssa). By simply adjusting the reduction degree of two-dimensional graphene nanosheets the coating thickness of reduced graphene oxide (RGO) the high solar absorptivity (α solar ≈ 0.92) the lowest thermal emissivity (≈ 4%) were obtained. Compared with the traditional carbon based materials the thermal emissivity of g-ssa is reduced by about 95.8% the optical cutoff wavelength of g-ssa is adjustable in the range of 1.1-3.2 μ M. More importantly the G-SSA prepared by the simple sol-gel method has a heat resistance of 96 hours at 800 degrees which is not easy to achieve by other ceramic or photonic crystal based selective absorbing films. Based on the g-ssa they found that the generation of high temperature under the sunlight makes the water have an ultra fast vapor escape velocity (0.94 MGCM − 2 s − 1).

this work will provide a new strategy for the development of high temperature resistant selective absorption films has great significance in the fields of solar thermal surface light absorption control.

the first author of this paper is Liao Qihua a doctoral student of Tsinghua University. His research work is supported by the national key research development program the National Natural Science Foundation of China the independent research project of Tsinghua University the project of Tsinghua Foshan Research Institute.


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