Coupled optimization of optical and thermal properties for NaCl-Al2O3 towards efficient thermal energy storage

Abstract

In this paper, a coupled optimization method of optical and thermal performance was explored by us. The microscopic structure of NaCl-Al2O3 based composite phase change material (CPCM) was established, the thermal properties were obtained by means of molecular dynamics (MD) simulations combined with experiments. The first principle calculations were also carried out to investigate the optical performance of the CPCM. The results indicated that the addition of nano Al2O3 can effectively improve the thermal performance and thermal stability of CPCM, when the mass fraction of Al2O3 nanoparticles in CPCM are 2.2 wt% and 7.2 wt%, the mass loss of CPCM samples were 0.14 % and 0.016 % after 100 times cycle, and the thermal conductivity and specific heat capacity can be increased by 15.45 % and 7.63 % at most. In addition, it was found that the optical performance of the CPCM can be also significantly improved. The microscopic coupled optimization mechanism was successfully revealed by the calculation of phonon density of state and band structures, which is desired to be a candidate approach to improve the photo-thermal conversion efficiency of the heat absorber contained in CSP (concentrating solar power) system.