Novel In Situ Experimental Technique to Understand Inner Workings of a Polymer Electrolyte Membrane Fuel Cell
Amit M. Manthanwar*†, Thiago Lopes‡, Stephen C. Atkins‡, Anthony R. Kucernak‡ and Efstratios N. Pistikopoulos§
†Department of Chemical Engineering, Imperial College London
‡Department of Chemistry, Imperial College London
§Department of Chemical Engineering, Texas A&M University
Abstract: 01 - ENGINEERING SCIENCES AND FUNDAMENTALS
Targeted Session: 01E04 Electrochemical Systems for Energy Conversion and Storage
Experiments carried out by load variations with realistic operational conditions give vital information for designing and operating fuel cells that achieve higher performance and longer life. Fuel cell phenomena involves complex interplay of mass transport, energy transfer and electrochemical processes. The convolution of these processes leads to spatial heterogeneity and ultimately affects the performance of a fuel cell, . Only spatially resolved in plane and through plane direction measurements can accurately provide insight into all parts of a cell and help optimise its performance as against the bulk measurements. The direct measurement of spatiotemporally distributed transport phenomena within fuel cell is a challenging task.
Several measurable and unmeasurable parameters are critical to the performance of a proton exchange membrane fuel cell. These factors include, but are not limited to, (a) chemical factors: temperature, pressure, humidity, velocity and reactant composition; (b) electrical factors: current density, potential and contact resistance; (c) material properties: catalyst loading, decay, and membrane conductivity; (d) design: channel geometry and cell assembly. Kandlikar and Lu, , reviewed the water and thermal management issues while Wu et al., , reviewed the available diagnostic tools and techniques. Amongst all the measurement techniques, local temperature measurements with thermocouples are easier to set up. They can provide high resolution in situ spatial and temporal insights in an unobtrusive way with minimal impact on the fuel cell. Pioneering work in this area was carried out by Mench et al., , by placing an array of 8 micro-thermocouples embedded at different positions directly between two 25 cm2 thick Nation electrolyte but only 3 gave reliable output. Recently Lin et al., , placed an array of 25 thermocouples at the back sides of 50 cm2 six serpentine channels cathode and anode flow field plates. Due to sensor location, large number of channels and high operating current densities a true reaction temperature at MEA was not observed.
We present a novel experimental method for understanding the temperature distribution across (through plane) membrane electrode assembly and along (in plane) flow field of a 50 cm2 single serpentine channel fuel cell. This method is an effective tool to test existing theory and critically examine the inner workings of a fuel cell accurately thereby help deduce a new mathematical model. We placed 64 thermocouples on both anode and cathode side in exact opposite directions of the membrane electrode assembly touching the gas diffusion layers. A set of controlled experiments were performed in ideal conditions by varying humidity, fuel stoichiometry and power output. These spatially and temporally resolved measurements provide an insight into operational cause-and-effect behaviour of fuel cells by observing the outcome when a particular variable or combination of variables are manipulated. The repeatable outcome and logical analysis of results help advance the understanding of fuel cell phenomenon.
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*The financial support from EPSRC grants (EP/I014640/1 and EP/K503381/1) and sponsorships from ARM Incorporation is gratefully acknowledged. Corresponding author: email@example.com
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