Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/134650
Title: MATHEMATICAL MODELLING OF LIQUID FUEL CELLS WITH APPLICATIONS IN UNCERTAINTY ANALYSIS AND SYSTEM OPERATION
Authors: LING CHUN YU
Keywords: direct methanol fuel cell, vanadium flow battery, liquid electrochemical device, uncertainty analysis, mathematical modelling
Issue Date: 13-Oct-2016
Source: LING CHUN YU (2016-10-13). MATHEMATICAL MODELLING OF LIQUID FUEL CELLS WITH APPLICATIONS IN UNCERTAINTY ANALYSIS AND SYSTEM OPERATION. ScholarBank@NUS Repository.
Abstract: This thesis focuses on the study of two types of liquid fuel cells, namely the direct methanol fuel cell (DMFC) and vanadium redox flow battery (VRFB). This is carried out primarily through validated mathematical modelling, where the equations of change for mass, momentum, species and charge are considered along with the relevant boundary conditions, electrokinetics and constitutive relations. Scaling arguments and asymptotics are utilized for both DMFC and VRFB models to yield reduced models; two-dimensional leading-order analytical solutions and zero-dimensional quasi-steady state solutions are derived for the former and latter respectively. These simplifications are justified using scaling analysis. Adoption of reduced models allows for the decrease in associated computational costs to solve the models whilst preserving dominant leading order physics; we further demonstrate the good agreement between experimental results, full model simulations and the simplified solutions. The no longer prohibitive computational costs afforded by the reduced model solutions allow for a variety of wide-ranging applied studies. For the DMFC, we choose to study the impact of uncertainty on the performance of the single cell as well as to demonstrate the ease at which a non-uniform stack model can be constructed. In the former, we examine the various parameters - cell geometry, operating conditions and material properties - to elucidate which is the most important; in addition, we also demonstrate the increase in associated uncertainty at lower cell potentials. In the latter, we demonstrate the ability of proposed stack modeling by discussing both global (cell-to-cell potential) and local (methanol, current density and parasitic current density distributions). For the VRFB, we experimentally demonstrate the impact of pulsating electrolyte flow on the performance; the underlying analysis is rooted in the zero-dimensional model reduction performed. Nevertheless, we show that adopting a pulsating flow strategy is indeed able to reduce the pumping costs, as well as minimize the system complexity via a reduction of balance-of-plant. Lastly, we highlight the importance of electrode selection for a VRFB by discussing and analyzing the implications of electrode oxidation in the single cell.
URI: http://scholarbank.nus.edu.sg/handle/10635/134650
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