Study on the Thermal Energy Storage Performance of PCM/epoxy/SiC-composite Fine Aggregates

Abstract

The new thermal energy storage aggregate (TESA) was developed with zeolite, paraffin wax, epoxy, and silicon carbide. Zeolite was immersed in melted paraffin wax, then covered with epoxy to prevent the paraffin wax from leaking when it melted. Before silicon carbide was covered with epoxy, it was mixed with epoxy to improve the thermal conductivity of TESA. Various experiment methods were used to investigate TESA and its energy storage efficiency. To compare TESA with cement paste, a compressive strength test and a flexural strength test were performed to determine their mechanical properties. Both strengths decreased when the TESA content of mortar was increased (from 0% to 30%, 50%, 70%, and 100%). After 28 days, the compressive strength of the mortar in which sand was fully replaced with TESA was over 10 MPa, which made it useful for wall plastering and certain masonry mortars. As for the thermal properties, the TGA, DSC, and thermal conductivity were determined. Finally, the thermal energy storage performance was evaluated by measuring the thermal behaviour before and after the thermal shock cycling and mock-up test. The results of the internal temperature measurement showed that TESA can be helpful in reducing temperature fluctuation inside mortar. The control mortar had a temperature fluctuation of 41.6℃, and TESA100, 30.8℃, or 10.8℃ lower. After the thermal shock cycling, the internal temperature was affected by the leakage of the paraffin wax. The difference in the fluctuation of the mortar that was not coated with epoxy, named “OP100,” was 6.3℃, and of TESA100, 2.8℃. This means there was less leakage of paraffin wax in TESA100 than in OP100. In the mock-up test, the center temperature of the mock-up specimen reduced the maximum temperature in the heating period, then raised the minimum temperature in the cooling period, so the difference between the maximum and minimum temperatures was 19.1℃, and in the control mock-up specimen, 29.5℃. The TESA100 mock-up specimen significantly maintained its indoor temperature and reduced its temperature fluctuation. According to various experiments, TESA has the potential to be used as a thermal energy storage material for buildings.