DESIGN, CONSTRUCTION, AND STUDY OF PERFORMANCE IMPROVEMENT IN A VANADIUM REDOX FLOW BATTERY

Open Access
Author:
Tseng, Ya-Ching
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 07, 2011
Committee Members:
  • Clinton Matthew Mench, Thesis Advisor
  • Matthew M Mench, Thesis Advisor
Keywords:
  • VANADIUM REDOX FLOW BATTERY
Abstract:
ABSTRACT A reliable Vanadium Redox Flow Battery (VRB) system was designed, built, and tested in a laboratory environment. Properties of components assembled inside a cell determined the polarization losses and consequently the performance of the VRB. As part of the research, the impact of the graphite felt electrode and a turbulent promoter placed between the electrode and the membrane were investigated. For the graphite felt electrode, a thermal pretreatment significantly enhance the performance of a VRB. The turbulent promoter was designed to promote the diffusion rates of active species from the reaction surface in the electrode to the membrane. The water transport through the polymer membrane, which changes the concentration of electrolytes and has a deterministic role in performance, was also measured in the study. The open circuit voltage of self-discharge was recorded for monitoring crossover through the polymer membrane. The energy efficiency of the VRB was 77% by using the thermal pretreatment graphite felt at 400oC for 30 hours, which is 29% higher than the VRB using the non-treatment graphite felt under the same test conditions. The usage of the turbulent mesh slightly enhanced the Coulombic efficiency, however the energy efficiency slightly decreased. Approximately 15% amount of water transported through the membrane from the negative to the positive half cell after 14 hours charge-discharge operation. During the self-discharge process, the Nafion 117 took 90 hours for OCV to reduce to 0.2 V after charged state at 90% state of charge SOC. The results in this study can help 1-D and 2-D modeling of the fluid mechanism inside a VRB cell design enhanced internal architectures to minimize ohmic losses.