Dalian RONGKEPOWER Co.

Dalian, China

Dalian RONGKEPOWER Co.

Dalian, China
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You D.,CAS Dalian Institute of Chemical Physics | Zhang H.,CAS Dalian Institute of Chemical Physics | Sun C.,Dalian RONGKEPOWER Co. | Ma X.,CAS Dalian Institute of Chemical Physics
Journal of Power Sources | Year: 2011

A simple mathematical model is established to predict the self-discharge process in a kilowatt-class vanadium redox flow battery stack. The model uses basic mass transport theory to simulate the transfer of vanadium ions in the battery. The simulation results agree reasonably with the experimental values, confirming the validity of the model. It is found that the diffusion rate of vanadium ions depends on the diffusion coefficient, the partition coefficient and the concentration gradient of the vanadium ions between the two half cells. For the self-discharge process at the initial SOC of 0, the net transfer direction of vanadium ions is towards the negative electrolyte until the diffusion flux of V3+ becomes larger than that of VO2+. For the self-discharge process at the initial SOC of 65%, the net transfer direction of vanadium ions is towards the positive electrolyte at the initial 20 h and then turns to the negative electrolyte. There are two obvious changes in the diffusion flux of vanadium ions at about 33 h and 43 h, corresponding to the vanishing time of VO2+ and V2+ respectively. © 2010 Elsevier B.V. All rights reserved.


Ma X.,CAS Dalian Institute of Chemical Physics | Zhang H.,CAS Dalian Institute of Chemical Physics | Sun C.,Dalian RONGKEPOWER Co. | Zou Y.,Dalian RONGKEPOWER Co. | Zhang T.,Dalian RONGKEPOWER Co.
Journal of Power Sources | Year: 2012

Electrolyte flow rate is a key factor that affects the performance of vanadium redox flow battery (VRFB). A kilo-watt class VRFB system is fabricated to investigate the effects of electrolyte flow rate on the performance of VRFB. The experiments show that the capacity increases, but the system efficiency decreases with the increase of electrolyte flow rate. An optimal strategy of electrolyte flow rate is proposed to improve the system efficiency and keep the high capacity simultaneously, which is corresponding to optimize the electrolyte flow rate at different stages of charge and discharge processes. The results show that the system efficiency can be improved as high as 8% when keeping high capacity simultaneously. © 2011 Elsevier B.V. All rights reserved.


Zheng Q.,CAS Dalian Institute of Chemical Physics | Zheng Q.,Dalian University of Technology | Zheng Q.,University of Chinese Academy of Sciences | Zhang H.,CAS Dalian Institute of Chemical Physics | And 4 more authors.
Applied Energy | Year: 2014

A three-dimensional model for thermal analysis has been developed to gain a better understanding of thermal behavior in a vanadium flow battery (VFB). The model is based on a comprehensive description of mass, momentum, charge and energy transport and conservation, combining with a global kinetic model for reactions involving all vanadium species. The emphasis in this paper is placed on the heat losses inside a cell. A quasi-static behavior of temperature and the temperature spatial distribution were characterized via the thermal model. The simulations also indicate that the heat generation exhibits a strong dependence on the applied current density. The reaction rate and the over potential rise with an increased applied current density, resulting in the electrochemical reaction heat rises proportionally and the activation heat rises at a parabolic rate. Based on the Ohm's law, the ohmic heat rises at a parabolic rate when the applied current density increases. As a result, the determining heat source varies when the applied current density changes. While the relative contribution of the three types of heat is dependent on the cell materials and cell geometry, the regularities of heat losses can also be attained via the model. In addition, the electrochemical reaction heat and activation heat have a lack of sensitivity to the porosity and flow rate, whereas an obvious increase of ohmic heat has been observed with the rise of the porosity. A lower porosity or a faster flow shows a better uniformity of temperature distribution in a VFB. Thus, the model proposed in this paper shows good prospect in heat and temperature management for a VFB aiming at eliminating any crisis of internal heat accumulation. © 2013 Elsevier Ltd.

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