(189c) Computer Aided Analysis about the Flow Channel Structure Effect on the Vanadium Redox Battery

Modern civilization demands more energy ever than the past. However, the traditional energy source like fossil fuel cause pollution and global climate change. The renewable energies -for example, solar cell and wind turbine and biomass fuel- are suggested as alternative energy source. Electric power scale of renewable energy is usually smaller than ordinary energy source. Furthermore, Lots of renewable energy is influenced by circumstance and time. To achieve stable electric power supply, it is inevitable to develop high capacity energy storage system. Also, Smart grid is one of the technology to provide stable power supply. Redox flow battery (RFB) is an electrical battery which uses redox reaction of electrolyte ions to generate power. It is a prospective energy storage system (ESS) because of its flexible installation. Due to separation of generation and storage of VRB, it is easy to control capacity and power level of VRB by adjusting storage tank and cell size respectively. Those advantages allows VRB to be appeared at the various field. For example, VRB is widely used in applications including, but not limited to, remote area (e.g. island, Mountains) power supply, back-up power and power level and distribution optimization. The power scale of VRB is also wide. However, there are a lot of alternative device for ESS. VRB must be improved of its efficiency to be competitive

VRB, a kind of RFB, takes vanadium ions for its redox couple. Using vanadium redox couple had certain advantages compared to using other materials. Because cross-over loss was less than other redox flow batteries. Also, VRB side reaction is smaller than other redox flow batteries. Several researches has been carried out to improve VRB performance. Generally, porous carbon is used as VRB electrode. Proper heat and chemical treatment on porous carbon could assist electrochemical reaction of cell. Polysulfonic membrane had been used in early developed RFB until nafion was invented. Nowadays, almost all RFB uses nafion membrane for its high hydrogen ion delivery.

 Researches has been progressed on VRB not only on the materials side, but also other aspects as well. Previous researches regarding ordinary electrochemical cell such as fuel cell show that well designed cell structure can improve cell performance. Cell structure can reduce activation loss by enhancing mass transportation. Similar research was conducted on VRB. The research revealed that the cell characteristics changed significantly following the type of channel structure. Pressure drop and limit current dramatically changed by cell type because of mass transportation.

 Analytic modeling is widely used to analyze RFB’s dynamic performance. Because analytic modeling require severe differential calculation, computer simulation is widely used for VRB research. Furthermore it is hard to measure inner side of cell experimentally. Therefore, Computer simulation can be a complementary tools to analyze and design RFB It should also be noted that parameters are easily changed in computer simulations. Recent computing power growth enable much more intensive simulation than before. Therefore, it is more convenient to analyze electric cell with computer simulation. Computer simulation is preferable way to analyze and designs cell structure. Recent studies shows that channel type influence cell performance characteristics such as current-potential curve. In this study, inner cell features such as concentration distribution, flow distributions, electrical potential and transfer current distribution were analyzed by channel type to investigate relationship between channel structure and performance. . Then, new VRB design which combined various advantages of each cell structure type are proposed. Modified cell performance was analyzed with computer simulation. Research was carried with COMSOL Multiphysics