Abstract The latest development of the vacuum tube solar collectors was reviewed.The discussions centered on three aspects:the advanced materials,structures,and thermal stabilities of the selective absorption coatings in vacuum.The stainless steel,Ti,Al and Ni are good materials for applications at lowand mediumtemperatures;whereasMo and W do well at high temperatures.The absorption coatings are mainly divided into two types:the absorber layer/ant-i reflection dielectric layer,based on light interference;the metal infrared reflection layer/metal dielectric absorber layer/ant-i reflection dielectric layer,named as the cermet absorber coating.Three main factors influencing the thermal stability include cracks,oxidation,and atomic inter-diffusion at high temperatures.Besides,the thermal stability also depends on its thickness and microstructures.The scenarios possibly focus on,i).growth of multilayer and gradient structured layers by elec-trochemical route and/or by magnetron sputtering,and hopefully with some nano-materials or nano-structures;ii).development of the Mo-based cermet coatings with high efficiency at high temperatures;iii). realization of the devices with high intelligence,automation,and integration in buildings.
Keywords Solar energy,Vacuum tube collector,Selective absorption coating,Thermal stability
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