Experimental thermal study of a new PCM-concrete thermal storage block (PCM-CTSB)

Phase change material concrete as a new building envelope has been widely used in passive building energy conservation, but less research has been done for it as a heat storage block in an active low-temperature thermal storage system. To enhance the heat storage capacity of PCM-concrete, overcome the PCM leakage problem and reduce the cost of heat storage, clastic light shale ceramsite (CLSC) was used to absorb paraffin to prepare PCM-CLSC aggregate and PCM-concrete thermal storage blocks with different PCM weight percentage (0, 2 wt%, 4 wt% and 6 wt%). The absorption, compatibility, thermal and mechanical properties of PCM-CLSC aggregate and PCM-concrete thermal storage blocks have been tested. To improve the charging and discharge rate, the active thermal storage and release system has been designed. Besides, the study presents the effects of PCM weight percentage and the characteristics of heat transfer fluid (HTF) on the performance of an active thermal storage system. The experimental results show that PCM-CLSC aggregate has good absorption and compatibility. The thermal conductivity and compressive strength of PCM-concrete thermal storage blocks decreased with the increase of PCM weight percentage, and the average specific heat capacity increased by 12.54% (2 wt% PCM), 31.60 (4 wt% PCM) and 41.23% (6 wt% PCM), respectively. Also, by increasing the PCM weight percentage, HTF flow rate and inlet temperature, it is possible to improve the heat storage and release capacity while effectively increasing the heat transfer rate and reducing the thermal resistance.