Abstract
This study investigates a battery system with a zinc-nickel single flow battery (ZNB) stack by a series-parallel-connected system based on a two-order Thévenin equivalent circuit model for single-cell stack and parameter identification of the experimental model. Two single-cell stacks are simulated with three kinds of series-parallel battery pack equivalent circuit models, and compared with the experimental data. The results show that the simplified equivalent circuit model can accurately characterize the voltage of discharge for the series-parallel battery pack. The relative errors of the series/parallel battery pack are 0.8% and 0.71%. Furthermore, the simulation and experimental test data of the large-scale series-parallel system are compared, thereby indicating that the simplified equivalent circuit model of the series/parallel battery based on the two-order Thévenin model can provide a high-precision prediction for the external characteristics of a large-scale ZNB energy storage system.
Highlights
IL Qi Qmax R0 R1 SOCThe polarization capacitances (F) Electric current (A) The rated capacity of the i single cell (cm sÀ1) The maximum available capacity (cm sÀ1) Ohmic resistance (X) The polarization resistances (X) State of charge SOC of the initial value SOC of the i single cell SOC of the parallel battery pack SOC of the series battery pack A single cell reaching its cut-off voltage time (S) Time constant of the RC circuit (S) The stack voltage (V) The open circuit voltage of the battery (V)
Distinguished from traditional energy storage batteries is that the active substance exists in the electrolyte; its output power and capacity are independent of each other, and the system design is flexible.1–3 Presently, the vanadium redox flow battery (VRB) is relatively mature and extensively used, but using an ion-exchange membrane increases the manufacturing cost of the VRB.4,5 The zinc–nickel single flow battery (ZNB) proposed in recent years is a cost-effective flow battery, which uses a single electrolyte and no ion exchange membrane, and exhibits the advantages of a simple structure, extended life cycle, high reliability and nonpollution; ZNB has a favorable application prospect in large-scale renewable energy generation storage systems
This study investigates a battery system with a zinc-nickel single flow battery (ZNB) stack by a series-parallel-connected system based on a two-order Thevenin equivalent circuit model for single-cell stack and parameter identification of the experimental model
Summary
The polarization capacitances (F) Electric current (A) The rated capacity of the i single cell (cm sÀ1) The maximum available capacity (cm sÀ1) Ohmic resistance (X) The polarization resistances (X) State of charge SOC of the initial value SOC of the i single cell SOC of the parallel battery pack SOC of the series battery pack A single cell reaching its cut-off voltage time (S) Time constant of the RC circuit (S) The stack voltage (V) The open circuit voltage of the battery (V)
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