Direct Optical Charging Speeds Up Solar-Thermal Energy Storage

Energy storage is a significant branch of energy science,which has been developed in recent years to fulfill the mismatch between energy transformation and energy utilization both in time and space.Among energy storage areas,thermal energy storage has received widespread attention on account of its potential application in the industrial and civil systems.Besides,solar-thermal energy storage has been playing a more and more important role in the thermal energy storage areas for the high efficiency of solar-thermal conversion and wide availability of solar energy.Nevertheless,the present investigations on solar-thermal energy storage focus on the enhancing of the thermal conductivity of thermal storage materials for the thermal conductivity of the thermal energy storage materials is relevantly low,which leads to a quite slow charging and discharging speed and further limits its industrial application.To deal with this problem,people chose to dope the matrix with the nanoparticles which have a high thermal conductivity to enhance the intergral thermal conductivity.However,the overloading of the nanoparticles results in some new problems.On the one hand,the enthalpy of the phase change materials begins to decrease.On the other hand,the agglomeration of the nanoparticles appears in terms of the bad dispersibility of the nanoparticles.In this work,we got rid of the thermal conductivity enhancing method and proposed a novel optical charging method that utilizes the rapid photon transmission to realize fast and uniform charging of thermal energy storage materials.Photons from the illumination with certain wavelength would excite the resonance of surface electrons of gold nanoparticles and thus produce much heat through electron-electron and electron-phonon relaxtion.We also confirmed that direct optical charging could speed up solar-thermal energy storage in phase change materials and further built up a “step by step” model to explain the phenomenon.Based on the theoretical analysis,we further proposed a magnetic manipulation method to speed up solar-thermal energy storage in phase change materials and verified its feasibility of enhancing solar energy capture.