Vanadium flow battery (VFB) is one of the most optimal technologies for large scale energy storage applications. To keep a safe and effective operation, it is critical to monitor and control the temperature range and heat generation inside a VFB, which is based on the understanding of the heat generation mechanism and the temperature spatial distribution characteristic inside a VFB. In this regard, a three-dimensional model for thermal analysis has been developed to gain a better understanding of thermal behavior in a 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.

According to the quasi-static model, the dynamic behavior of temperature was characterized, showing that the temperature increases more and more rapidly with the elevated applied current density and accordingly the battery will be up to a poor thermal environment without heat exchanger after numerous charge / discharge cycles. Based on the spatial distribution of temperature, the localized extreme temperature can be found in the electrode corner, especially in the negative region during the discharging process. Therefore, it is significant to perform heat exchange timely and heat treatment locally for a safe operation of VFB. On the other hand, the effect of applied current density, flow rate and porosity on the temperature and heat generation source (the electrochemical reaction heat, ohmic heat and activation heat) was investigated via the model. The simulations indicate that the heat generation exhibits a strong dependence on the applied current density. As the current density increases, the electrochemical reaction heat rises proportionally and, the activation heat and ohmic heat rise at a parabolic rate. Note that ohmic heat makes more contribution to heat generation than the activation heat. Hence, the determining heat source would vary from the electrochemical reaction heat to the ohmic heat if the applied current density is large enough. A lower porosity or a faster flow shows a better uniformity of temperature distribution.

Qiong Zheng