Storage system design based on equivalent-circuit-model simulations: Comparison of eight different electrochemical capacitor storage systems

Abstract

Energy storage systems were designed to satisfy application specifications using electrical performance simulations. Starting with published two-time-constant equivalent circuit models for eight commercial electrochemical capacitors, cell models were first scaled to meet application voltage requirements. Then SPICE (Simulation Program with Integrated Circuit Emphasis) was iteratively performed to further scale the stored energy in each model until it precisely met application specifications. Thus created were equivalent circuit models for full-size energy storage systems. Four applications were used to demonstrate this system-design approach. Three involved constant-power discharge (durations of 0.2 s, 1.3 s, and 30 s) and one involved non-constant-power charge (7-s regenerative braking energy storage). Although each storage system design exactly met application specifications, major differences were evident. For example, the 0.2-s-discharge application showed that one storage system had less than one-half the cost of all others. Also, the 30-s-discharge application showed that one storage system had less than one-half the volume of all others. Details of the system design approach are described and then mass, volume, cost, and efficiency of the storage systems are compared for each demonstration application.