基于可逆热致变色的动态体吸收太阳能光热存储相变材料

Dynamic absorption of bulk phase-change materials for photothermal solar energy storage based on reversible thermochromic

相变材料(phase change material,PCM)有望解决热能储存和热管理等方面的问题.然而,随着瞬态熔体前沿远离热源,其能量密度和功率密度逐渐降低.在太阳能直接热利用过程中,传统充热的完成完全依赖于PCM本身的热扩散过程,低热导限制了PCM的充热速率.本文提出了基于可逆热致变色特性的动态相变材料(dynamic phase change material,Dyn PCM),可以自动控制光热界面位移紧跟熔体前沿,使相变材料在光热转换中的充热速率不受材料自身热导率限制.Dyn PCM由热致变色剂和主体PCM两部分组成,热致变色剂以2-苯氨基-3-甲基6-二丁氨基荧烷作为供电子体,2,2-双(4-羟苯基)丙烷作为受电子体及4-苄氧基苯基乙基葵酸酯作为溶剂成功实现无色-黑色的变换.主体PCM以石蜡为例,其中含83.3 wt.%石蜡含量的Dyn PCM_(5)潜热为154.38 kJ/kg,仅比石蜡降低6.6%,其透明态表现出与石蜡接近的透射率为91.2%.对比表明,Dyn PCM_(5)的充热速率比石蜡提升了260%.经80次循环后,Dyn PCM的基团未发生改变,充放热性能及透射率稳定性优异,仍具有良好的可逆的变色及充热能力.因此,本研究提出的热致变色复合Dyn PCM_(5)是一种有前景的太阳能储热材料,可进一步运用在太阳能直接吸热过程中.

Phase change materials(PCMs)are expected to solve the problems in thermal energy storage and thermal management.However,the energy density and power density of the transient melting front decrease as it moves away from the heat source.In the process of direct solar thermal utilization,the completion of the traditional heating totally depends on the thermal diffusion process of the PCM,and the low thermal conductivity limits the heating rate of the PCM.In this study,a dynamic phase-change material(Dyn PCM)based on reversible thermochromic properties is proposed that can automatically control the displacement of the light-thermal interface to follow the melting frontier.The thermal conductivity of the material would not limit the heating rate of the phase transition material during photothermal conversion.Dyn PCM is composed of two parts:a thermochromic agent and the main PCM.The thermochromic agent uses 2-phenylamino-3-methyl-6-dibutylaminofluoran as the electron donor,2,2-bis(4-hydroxyphenyl)propane as the electron acceptor,and 4-benzyloxy Phenyl Ethyl Decanoate as a solvent to successfully achieve the transformation from transparent to black.The main PCM takes paraffin as an example.The latent heat of Dyn PCM_(5),which contains 83.3 wt.%paraffin,is 154.38 kJ/kg,which is only 6.6%lower than that of paraffin,and its transparent state shows transmittance of 91.2%,which is close to paraffin.The comparison shows that the charging rate of the Dyn PCM_(5)is 260%faster than that of paraffin.The Dyn PCM groups remained unchanged after 80 cycles.The Dyn PCM did not change.Dyn PCM still has good reversible discoloration ability,maintains excellent thermal charge and discharge performance,and has stable light transmittance.As a result,the thermochromic composite Dyn PCM_(5)developed in this study is a potential solar heat storage material that may also be used for direct solar energy absorption.