The Design and Test for Degradation of Energy Density of a Silica Gel-Based Energy Storage System Using Low Grade Heat for Desorption Phase

This paper presents the design and a short cycle repeatability test of a silica gel-based thermal energy storage system using low grade heat for the desorption phase. The system was designed to test the degradation in the energy storage density of the adsorbent material for a 2 h working period in a short number of cycles (5 cycles). Low grade heat of 70 °C is used for regeneration during the desorption phase in each cycle. It was found that a reduction of 1.6 W/kg per each cycle of energy storage was observed, up to 5 cycles. The maximal heat storage density was 292 kJ/kg at the first cycle and reduced to 225 kJ/kg at the fifth cycle. Furthermore, the total amount of water vapor adsorbed in the silica gel was observed as well. The test of energy storage was performed under a short time period (maximal approx. 165 min).