Fuel Cell Activities in MME Waterloo Xianguo Li and Roydon Fraser Fuel Cells and Green Energy Research Group Department of Mechanical & Mechatronics Engineering University of Waterloo, Waterloo, Ontario, CANADA April 27, 2007
Our Slogan Fuel Cell R&D: Capacity for Today & Partnering for the Future
PEMFCs/DMFCs SOFCs Power Electronics Fuel Cell Research & Development Materials Design/Fabrication Experiments
Waterloo Fuel Cell Expertise Main focus on PEM fuel cells with smaller programs in DMFC, SOFC and bio-fuel cells PEM fuel cell research focuses: Development of key component materials Membrane electrolytes, gas diffusion layers, alternative and non-platinum based catalysts, bipolar plates Design and fabrication for single cells and stacks Bipolar plate and flow channel design; Scaling law development Dynamic response and cold-start System integration and optimization Sensing, control and power conditioning Thermal and water management Fuel cell based hybrid drive systems Modeling and simulation to improve fundamental understanding
Fuel Cell Infrastructure Research Hydrogen production Hydrocarbon fuel (ethanol) reforming From green power sources (wind and solar PV) Hydrogen storage Metal hydrides Hydrogen distribution Hydrogen re-fuelling station Hydrogen energy systems System design and modeling Life cycle analysis Environmental impact assessment
Fuel Cell Testing Facilities
Fuel Cell Structural Changes Electrode Before Use Electrode After Use After Use (magnified)
Fuel Cell Design and Fabrication End Plate Current Collector Anode Flow (Bipolar) Plate Insulator Sheet Electrolyte Membrane Porous Electrode End Plate Reactant Inlet/Outlet Holes Holes for Tie Bolts Flow Field Channels Cathode Flow (Bipolar) Plate Current Collector
Proton/Water Transport Through Membrane Micro/nano Structure at Molecular Level
Applying the Generalized Stefan-Maxwell Equations to Ion and Water Transport in the Polymer Electrolyte
Anode Catalyst Layer Reaction Model (η a ) Four phenomena contribute to η a : Reaction Kinetics: H 2 adsorption, desorption and electro-oxidation CO adsorption, desorption and electro-oxidation H 2 and CO heterogeneous oxidation In the case of O 2 (air) bleeding: O 2 adsorption, desorption and Heterogeneous oxidation of H 2 and CO Mass Transfer: From gas channels and through electrode backing to arrive at the catalyst layer Within the catalyst layer, where reaction occurs Electron Migration within Catalyst Layer Proton Migration within Catalyst Layer
Equilibrium CO Concentration Due to reverse water gas shift reaction for the initial anode composition of 75% H 2 and 25% CO 2 (dry basis)
H 2 Kinetics Tafel-Volmer reaction mechanism: Langmuir Kinetics for H 2 adsorption and desorption: Butler-Volmer model for electro-oxidation: Where θ i surface coverage
CO poisoning Mechanism: CO Kinetics CO blocks reaction sites for the chemisorption of H 2 Reaction pair mechanism: Temkin kinetics for CO adsorption and desorption: Butler-Volmer model for electro-oxidation:
O 2 Kinetics Langmuir-Hinshelwood mechanism: Langmuir kinetics for O 2 adsorption and desorption: Heterogeneous oxidation of H 2 and CO:
Anode Catalyst Layer Analysis/Modeling
Anode Catalyst Layer Analysis/Modeling At T = 358 K C CO = 20 ppm
Effect of O 2 and Air Bleeding Anode: H 2 Cathode: O 2 Anode: 75% H 2 25% CO 2 Cathode: Air
O 2 Kinetics in the Cathode Catalyst Layer Electro-reduction of O 2 : + O2 + 4H + 4e 2H 2O l ( ) Butler-Volmer equation for the rate of reaction: w& c O O O 2 2 i C o O2 = sinh 2 2F CO 2 ref γ η B, O c 2
Cathode Catalyst Layer Analysis/Modeling Effective Pt Use Pt Loading m Pt (mg/cm 2 ) Void Fraction
Cathode Catalyst Layer Analysis/Modeling Thickness δ (µm) Overpotential (V) Pt Loading (mg/cm 2 )
Physical Problem inlet L A A B L outlet
3-D D Surface Plot of Rate of Reaction (A/m 2 )
Cell Analysis/Modeling Reversible Cell Potential Cathode Oxygen Reduction Voltage (V) Actual Cell Potential Membrane Anode H Oxidation 2 Plate & Electrode Cell Current Density (A/cm 2)
Cell Analysis/Modeling Mathematical Cell Model Using a Single Domain Approach
A Typical Single Cell Layout
Gas Transport Water Transport
Effect of Channel Length
Fuel Cell Modeling and Simulation
Fuel Cell Modeling and Simulation
Fuel Cell Simulation
Flow Structure Changes
Current Density Transport of Electrons Flow Channels
Stack Analysis/Modeling/Optimization U Stack Design Z Stack Design
Effect of Stack Manifolding Design Voltage Spread: S E max min Ecell Ecell = 100 Ncell 1 E () i N cell i= 1 cell 50 cell stack operating at 0.6 A/cm 2
Effect of Manifold Cross Sectional Area Reformate-Air H 2 -Air H 2 -O 2 U Configuration Z Configuration
Different Stack Design Stack Configuration U-Configuration Z-Configuration S E [%] 4.6 1.2 1.1 0.4 0.5 2.3
System Analysis/Modeling/Optimization To environment Control volume 9 Hydrogen recirculation 18 Hydrogen storage 1 Pressure regulator 3 Humidifier 5 7 H 2 2 Air intake filter 4 Air compressor 6 Heat Exchanger 14 17 Humidifier 8 10 16 PEM Fuel cell stack 11 13 Electric work 20% of total heat 12 Water Air To environment 15 Coolant pump Car radiator Heat lost to the environment fan
Neutron Radiography: Perfect Probe for Water Distribution in PEM Fuel Cells A neutron image of rose placed inside a lead cask; this is an impossible task for x-rays
Neutron Radiography
Liquid water distribution vs. Performance-Case I Case I: Load change: 0 0.05 0.25 0.5 0.75 0.5 0.25 0.05 0 (A/cm 2 ) Each picture is one minute integration and data point is one minute average; T= 60 O C and Load changes every three minutes.
Liquid water distribution vs. Performance-Case II Case II: Load change: 0 0.05 0.25 0.5 0.75 1.0 0.75 0.5 0.25 0.05 0 (A/cm 2 ) Each picture is one minute integration and data point is one minute average; T= 60 O C and Load changes every three minutes.
Liquid Water Distribution in a PEM Fuel Cell
Comparison on liquid water distribution Contour plot for the velocity (y-component) in GDL
University of Waterloo Alternative UWAFT has installed 65 kwatt Hydrogenics fuel cell stack into Chevy Equinox drive train, and has the first fuel cell passenger vehicle in Ontario. Fuel Team (UWAFT) UWAFT is one of the 17 teams competing in ChallengeX. Waterloo Finished First in the first year (2005) of the 3 year competition. Eight Awards in 2006 UWAFT would like to thank GM and the US DOE for sponsoring this competition. (Controls, Freescale, Mathworks, Cross Model/Design, Outreach).