Experimental optimization of operating conditions for an open bulk-scale silica gel/water vapour adsorption energy storage system

Thermal energy storage (TES) is an effective way to reduce the energy supply and demand mismatch and facilitate the more widespread use of renewable energy sources like wind and solar power. However, there is a scarcity of data regarding the effects of operating conditions for TES systems, making it difficult to accurately model and design these systems. The objective of this study was to optimize the performance of an open bulk-scale silica gel/water vapour adsorption-based energy storage system by systematically varying the key oper-ating parameters (relative humidity, particle size, desorption temperature, and flow rate) and observing the effects of these variables on breakthrough experiments, energy storage density, maximum temperature lift and thermal power. It was found that the optimal conditions for the 50 g system used were a desorption temperature of 120 ?, a flow rate of 24 SLPM, an adsorption inlet relative humidity of 90%, and a 12-20 mesh particle size. Under these conditions, an energy storage density of 200.7 kWh/m(3) (252.1 Wh/kg) was achieved, with a maximum temperature lift of 28.5 ?. The maximum and average thermal power of the system under these optimal conditions were 15.4 W and 5.9 W or 245.2 W/L (308 W/kg) and 93.9 W/L (118 W/kg), respectively. The breakthrough time was 11 min, and it took 126 min for the column outlet humidity to reach 95% of its maximum value. This study has summarized the effects of various operating conditions and will help to provide a basis for future simulation work, prototype design, and techno-economic assessments of the TES system.