Analysis and Optimization of Thermally-Regenerative Ammonia-Based Flow Battery Based on a 3-D Model

Thermally-regenerative ammonia-based flow battery (TR-AFB) is considered to be an efficient way to harvest low-grade waste heat, but its performace such as power density and voltage are still need to improve. In this paper, an isothermal three-dimension (3-D) numerical model for TR-AFB has been proposed in order to optimize its performance. Firstly, the concentration distribution of species in the flow channel of TR-AFB and effects of different flow forms on power production are described. The results indicate that dead zones are found in the initial experimental flow channel, which greatly affect the performance of the battery. Therefore, in order to improve the performance, flow channels of TR-AFB have been optimized using silicon rubber sheet channel and copper electrode flow channel. According to the optimization results, it is found that the maximum power density of the battery can be increased by about 33% (12.1Wm(-2)), while the pump power consumption only increase by 2.13 x 10(-2) Wm(-2). By comparing the performance of batteries with different flow channels, the general laws of designing flow channel are summarized. That is to minimize the flow dead zones, increase the reaction areas and reduce the distance between electrodes within the allowable range. (c) 2019 The Electrochemical Society.