Experimental Study of the Thermochemical Performance of Licl and Libr Embedded within 3a-Zeolite for Seasonal Thermal Storage

Abstract

The mismatch between the solar energy in the summer and the heating demand in the winter inspires the research and development of storing energy over seasons. Thermochemical energy storage using salt hydrate – porous matrix composite is one of the most promising solutions to this problem, as these composites are clean, easy to obtain, stable and with high heat storage densities. In this study, the solution impregnation method was employed to prepare various salt-zeolite composite adsorbents. The composite surface morphology after manufacturing was observed using SEM (Scanning Electron Microscopy), and the material porous properties were measured by BET (Brunauer, Emmett and Teller Specific Surface Area Analysis). The water adsorption capacity of the material was firstly measured using a climatic chamber. After full adsorption, DSC (Differential Scanning Calorimetry) tests were carried out for the heat storage density of the material. XRD (X-Ray Diffraction) was performed to analyse the hydration bound formed in different temperature and humidity conditions of various adsorbents. SEM-EDS results showed that with the increase of the salt mass ratio in the solution during composite manufacturing, the salt was distributed more on the sample surface. BET results showed that the specific surface area (SSA) and pore diameter decreased with the solution concentration increments. The climatic chamber adsorption showed that the composite adsorbs more water than pure zeolite does, and the higher salt ratio in the composite resulted in the higher water adsorption capacity. The highest water adsorption capacity was observed using the material of 5%LiCl-25%LiBr-zeolite (0.22 g/g). The DSC test results showed a maximum water adsorption capacity of 0.16 g/g (5% LiCl-zeolite) and the highest heat storage density of 592.8 J/g (5%LiCl-5%LiBr-zeolite). As a summary, the most promising composite material for seasonal energy storage is 5%LiCl-25%LiBr-zeolite.

Keywords: Thermochemical, 3A zeolite, LiCl, LiBr, seasonal solar thermal energy storage