Honeycomb filters made from mesoporous composite material for an open sorption thermal energy storage system to store low-temperature industrial waste heat

Today, a significant amount of low-temperature (< 100 °C) industrial waste heat is directly discharged to the atmosphere. In this study, a new mesoporous composite material was developed as a sorption thermal energy storage material by utilizing its sorption and desorption properties. The composite material was formed by adding calcium chloride (CaCl2) to a mesoporous ceramic honeycomb filter. The main component of this ceramic is Wakkanai siliceous shale (WSS), which is found in northern Japan. The material test results demonstrated the following: (1) the composite material can sorb more water than the original ceramic material without dropping the CaCl2 solution; (2) it can be regenerated at around 100 °C; and (3) after 25 repetitive regeneration/sorption cycles, no decomposition or cracks were observed. The sorption isotherm was also undamaged. An open sorption thermal energy storage system was proposed, and the experimental setup was constructed. A low regeneration temperature (80–100 °C) of the storage medium was achieved with this open system. In the case of the 22.4 wt% CaCl2 supported with the honeycomb filter (926.2 g; 2 L), air was heated to a temperature greater than 40 °C for a duration of 432 min by supplying air at 25 °C at a flow rate of 3.0 m3/h when the regeneration temperature was 80 °C. The volumetric heat storage density obtained was 272 MJ/m3, and the coefficient of the heat extraction performance during the heat release process was 65%.