Mitigating capacity decay and improving charge-discharge performance of a vanadium redox flow battery with asymmetric operating conditions

2019 ◽  
Vol 309 ◽  
pp. 283-299 ◽  
Author(s):  
M.Y. Lu ◽  
W.W. Yang ◽  
Y.M. Deng ◽  
W.Z. Li ◽  
Q. Xu ◽  
...  
Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 3005 ◽  
Author(s):  
Meng ◽  
Xiong ◽  
Lim

The safe, efficient and durable utilization of a vanadium redox flow battery (VRB) requires accurate monitoring of its state of charge (SOC) and capacity decay. This paper focuses on the unbiased model parameter identification and model-based monitoring of both the SOC and capacity decay of a VRB. Specifically, a first-order resistor-capacitance (RC) model was used to simulate the dynamics of the VRB. A recursive total least squares (RTLS) method was exploited to attenuate the impact of external disturbances and accurately track the change of model parameters in realtime. The RTLS-based identification method was further integrated with an H-infinity filter (HIF)-based state estimator to monitor the SOC and capacity decay of the VRB in real-time. Experiments were carried out to validate the proposed method. The results suggested that the proposed method can achieve unbiased model parameter identification when unexpected noises corrupt the current and voltage measurements. SOC and capacity decay can also be estimated accurately in real-time without requiring additional open-circuit cells.


Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 867
Author(s):  
Ha-Neul Moon ◽  
Hyeon-Bee Song ◽  
Moon-Sung Kang

In this work, we developed pore-filled ion-exchange membranes (PFIEMs) fabricated for the application to an all-vanadium redox flow battery (VRFB) by filling a hydrocarbon-based ionomer containing a fluorine moiety into the pores of a porous polyethylene (PE) substrate having excellent physical and chemical stabilities. The prepared PFIEMs were shown to possess superior tensile strength (i.e., 136.6 MPa for anion-exchange membrane; 129.9 MPa for cation-exchange membrane) and lower electrical resistance compared with commercial membranes by employing a thin porous PE substrate as a reinforcing material. In addition, by introducing a fluorine moiety into the filling ionomer along with the use of the porous PE substrate, the oxidation stability of the PFIEMs could be greatly improved, and the permeability of vanadium ions could also be significantly reduced. As a result of the evaluation of the charge–discharge performance in the VRFB, it was revealed that the higher the fluorine content in the PFIEMs was, the higher the current efficiency was. Moreover, the voltage efficiency of the PFIEMs was shown to be higher than those of the commercial membranes due to the lower electrical resistance. Consequently, both of the pore-filled anion- and cation-exchange membranes showed superior charge–discharge performances in the VRFB compared with those of hydrocarbon-based commercial membranes.


2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Victor Yu ◽  
Dongmei Chen

The vanadium redox flow battery (VRFB) is an attractive grid scale energy storage option, but high operating cost prevents widespread commercialization. One way of mitigating cost is to optimize system performance, which requires an accurate model capable of predicting cell voltage under different operating conditions such as current, temperature, flow rate, and state of charge. This paper presents a lumped isothermal VRFB model based on principles of mass transfer and electrochemical kinetics that can predict transient performance with respect to the aforementioned operating conditions. The model captures two important physical phenomena: (1) mass transfer at the electrode surface and (2) vanadium crossover through the membrane. Mass transfer effects increase the overpotential and thus reduce the battery output voltage during discharge. Vanadium crossover causes a concentration imbalance between the two half-cells that negatively affects the voltage response particularly after long term cycling. Further analysis on the system linearity is conducted to assess the feasibility of using a linear control design methodology.


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