Parametric study and flow rate optimization of all-vanadium redox flow batteries

Abstract The parametric study for an all-vanadium redox flow battery system was examined to determine the optimal operating strategy. As dimensionless parameters, the stoichiometric number and state of charge were used to apply the strategy to all scales of the flow battery system. In this study, we developed a transient model for this system, which is supported by experimental data, to analyze effect of parameters on the ion concentration and determine its optimal operating conditions. First, the performance of the flow battery system was analyzed in steady-state conditions to examine the changes of the ion concentration depending on different flow rates, current densities, and sizes of active area. As flow rate increases, the energy efficiency slightly increases, because faster flow rates can deliver more vanadium ions from the reservoir. The energy efficiency decreases according to current density, because large current results in large amount of ohmic loss of membrane. When the size of active area increases, the energy efficiencies remain constant, however, the cycle time decreases. Next, the transient response for the system was analyzed by changing the stoichiometric number and current density during the charge and discharge processes. Variation of the system’s energy efficiency was studied with changes in the stoichiometric number and state of charge as the current density was varied from 20 to 100 mA/cm2. Increasing the flow rate at the beginning of the charge–discharge process is more efficient in the low current density region. At a current density of 100 mA/cm2, however, it is better to increase the flow rate after the state of charge reaches 50%. Lastly, an operating strategy is suggested that involves controlling the mass flow rate of the electrolyte during the charge–discharge process. The operating strategy is presented as an empirical equation defined by the stoichiometric number and state of charge. Notably, this equation can contribute to improving the performance of all scales of the flow battery system by simply changing the electrolyte flow rate at right time.

[1]  Emin Caglan Kumbur,et al.  Open circuit voltage of vanadium redox flow batteries: Discrepancy between models and experiments , 2011 .

[2]  S. Jayanti,et al.  Ex-situ experimental studies on serpentine flow field design for redox flow battery systems , 2014 .

[3]  Ruiyong Chen,et al.  Ionic liquid-mediated aqueous redox flow batteries for high voltage applications , 2016 .

[4]  Qian Xu,et al.  Numerical investigations of flow field designs for vanadium redox flow batteries , 2013 .

[5]  M. Skyllas-Kazacos,et al.  Vanadium redox cell electrolyte optimization studies , 1990 .

[6]  C. R. Dennison,et al.  Reducing capacity fade in vanadium redox flow batteries by altering charging and discharging currents , 2014 .

[7]  S. Yoon,et al.  Highly proton conductive, dense polybenzimidazole membranes with low permeability to vanadium and enhanced H2SO4 absorption capability for use in vanadium redox flow batteries , 2016 .

[8]  Jun Liu,et al.  Towards understanding the poor thermal stability of V5+ electrolyte solution in Vanadium Redox Flow Batteries , 2011 .

[9]  Maria Skyllas-Kazacos,et al.  Online state of charge and model parameter co-estimation based on a novel multi-timescale estimator for vanadium redox flow battery , 2016 .

[10]  Yasushi Katayama,et al.  Investigations on V(IV)/V(V) and V(II)/V(III) redox reactions by various electrochemical methods , 2005 .

[11]  Jie Bao,et al.  Thermal modelling of battery configuration and self-discharge reactions in vanadium redox flow battery , 2012 .

[12]  Faizur Rahman,et al.  Vanadium redox battery: Positive half-cell electrolyte studies , 2009 .

[13]  Maria Skyllas-Kazacos,et al.  Adaptive estimation of state of charge and capacity with online identified battery model for vanadium redox flow battery , 2016 .

[14]  Dirk Uwe Sauer,et al.  Multi-physics Model for a Vanadium Redox Flow Battery , 2014 .

[15]  T. Zhao,et al.  A highly permeable and enhanced surface area carbon-cloth electrode for vanadium redox flow batteries , 2016 .

[16]  M. Mench,et al.  Redox flow batteries: a review , 2011 .

[17]  Tien-Chan Chang,et al.  Electrical, mechanical and morphological properties of compressed carbon felt electrodes in vanadium redox flow battery , 2014 .

[18]  Chenxi Sun,et al.  Investigations on transfer of water and vanadium ions across Nafion membrane in an operating vanadium redox flow battery , 2010 .

[19]  T. Zhao,et al.  A vanadium redox flow battery model incorporating the effect of ion concentrations on ion mobility , 2015 .

[20]  Xuelong Zhou,et al.  A high-performance dual-scale porous electrode for vanadium redox flow batteries , 2016 .

[21]  G. Graff,et al.  A Stable Vanadium Redox‐Flow Battery with High Energy Density for Large‐Scale Energy Storage , 2011 .

[22]  J. Bao,et al.  Studies on pressure losses and flow rate optimization in vanadium redox flow battery , 2014 .

[23]  Hansung Kim,et al.  Analysis of Concentration Polarization Using UV-Visible Spectrophotometry in a Vanadium Redox Flow Battery , 2014 .

[24]  Qinghua Liu,et al.  Dramatic performance gains in vanadium redox flow batteries through modified cell architecture , 2012 .

[25]  Akeel A. Shah,et al.  A Dynamic Unit Cell Model for the All-Vanadium Flow Battery , 2011 .

[26]  Min-Soo Kim,et al.  Experimental and computational study on the dynamic interaction between load variation and back pressure control in a polymer electrolyte membrane fuel cell for automotive application , 2015 .

[27]  Huamin Zhang,et al.  An optimal strategy of electrolyte flow rate for vanadium redox flow battery , 2012 .