Efficient energy storage method by multistage pump of the energy storage system using CFD

This research work focuses on a novel energy storage system that uses the concept of combined pumped hydro storage and compressed air energy storage technologies. The proposed system is an energy storage type that mainly consists of an open tank and a closed tank. Using the surplus energy from grid, water and compressed air are stored in the closed tank to pressure of up to 10 bar. A multistage pump with a maximum attainable head of 120 m, flow rate in the range of 1.2 to 5.5 m3/h, and rated speed of 3400 rev/min is used for pumping process. To study the charging process of the system, an analysis using CFD is carried out in two stages. Firstly, the numerical model of the pump is operated from 2800 to 4000 rev/min at different values of head and discharge. This is performed to determine the maximum values of efficiency and power consumption of the pump for the range. Secondly, a comparative analysis of performance of pump at constant and variable rotational speeds is accomplished. The comparative analysis shows that the operation of pump at constant speed attains the targeted pressure inside the closed tank in 100 s earlier than at variable speed. But the flow rate, efficiency, and power consumption of the pump during the analysis are found to be better at variable speed operation. Copyright © 2015 John Wiley & Sons, Ltd.