CACHE Modules on Energy in the Chemical Engineering Curriculum: Fuel Cells Jason Keith1, Don Chmiele

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CACHE Modules on Energy in the Chemical
Engineering Curriculum Fuel CellsJason Keith1,
Don Chmielewski2, H. Scott Fogler3, Valarie
Thomas31 Department of Chemical
EngineeringMichigan Technological University2
Department of Chemical and Biological
EngineeringIllinois Institute of Technology3
Department of Chemical EngineeringUniversity of
Michigan
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Outline

• Introduction and Motivation
• What is in each module?
• Where are the modules?
• What are the modules?
• Module walk-through
• Conclusions / Acknowledgments

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Introduction and Motivation

• Alternative energy component missing from most
  departments
• Fuel Cells have been discussed in the political
  arena as an alternative energy solution
• Need to educate ChEs in this area
• Growth in number of fuel cell textbooks
• Most do not have homework problems
• Modules can rapidly infuse new technologies into
  the Chemical Engineering Curriculum

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What is in each module?

• Problem motivation
• Reference to related sections and pages in
  popular ChE texts
• Example problem statement
• Example problem solution
• Home problem statement
• Home problem solution
• Link to web resources
• Non-ChE textbook resources
• Notes to instructor

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Where are the modules?

• Current beta test website
• http//www.chem.mtu.edu/jmkeith/fuel_cell_curric
  ulum
• Currently available for use by anyone!
• Ultimately linked through CACHE website

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What are the modules?

• Mass and Energy Balances
• Application of Heat of Reaction Hydrogen vs.
  Gasoline
• Material Balances on a Fuel Cell
• Energy Balances on a Fuel Cell
• Generation of Electricity Using Recovered Hydrogen

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What are the modules?

• Thermodynamics
• Equation of State for Fuel Cell Gases
• Thermodynamics and Fuel Cell Efficiency
• Vapor Pressure / Humidity for Fuel Cell Gases
• Fluid Mechanics
• Friction Factor in Bipolar Plate Channel

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What are the modules?

• Heat and Mass Transport
• Conduction and Convection Heat Transfer in Fuel
  Cells
• Microscopic Balances Applied to Fuel Cells
• Diffusion Coefficients for Fuel Cell Gases
• Kinetics and Reaction Engineering
• Nernst Equation and Fuel Cell Kinetics
• Using Plug Flow Reactor Equations for Fuel Cell
  Voltages

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Module walk-through

• How long can you power a laptop computer with a
  type K hydrogen cylinder (49.9 L)?

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Module walk-through

• Course Material and Energy Balances
  (Stoichiometery)
• Title Application of Heat of Reaction Hydrogen
  versus gasoline
• Motivation Use the heat of reaction to determine
  the energy contained in a hydrogen cylinder, and
  determine the equivalent number of gallons of
  gasoline.
• Reference Felder and Rousseau, Section 4.6(3rd
  ed.)

Each module has reference to popular text(s)
for the course
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Module Example Problem
Each example has an easy to follow step-by-step
approach

• Example Problem Determine energy generated for
  the combustion of a gallon of gasoline
• Step 1) Determine DHr for gasoline components
• DHr,C7H16 7 DHCO2 8 DHH2O - DHC7H16 11
  DHO2
• DHr,C7H16 -4816 kJ/mol
• Step 2) Similarly DHr,C8H18 -5461 kJ/mol

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Module Example Solution

• Step 3) Weighted average (87 n-heptane and 13
  isooctane) DHr,gas -5370 kJ/mol
• Step 4) Determine mass in grams of components in
  1 mol of gasoline 13.0 g n-heptane and 99.2 g
  isooctane
• Step 5) Determine volume of these components
• The total volume is 162 cm3 or 0.043 gal
• Step 6) Determine energy per gallon
• -5370 kJ/mol /(1 mol/0.043 gal) -125,000 kJ/gal

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Module Hwk Problem

• How many kJ are there in a K cylinder of H2?
• How many gallons of gas is this equivalent to?
• How many gallons of water do you make from the
  hydrogen in the gas cylinder?
• What is the maximum time you could power a 100 W
  laptop with this H2 cylinder?

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Module Hwk Solution

• Currently open to everyone final version will
• be password protected
• Recommend printing example and statement
• and giving to students as a handout
• Rest of step-by-step solution available at end
  of
• talk

• How many kJ are there in a K cylinder of H2?
• Assume liquid water product, DHr,H2O -286
  kJ/mol
• From ideal gas law, cylinder contains n 278
  mol
• Energy content -n DHr,H2O 79000 kJ

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Conclusions / Acknowledgments

• Fuel Cell Modules are for your use!
• Contact one of the authors to participate
• Acknowledgments of Partial Support
• CACHE Corporation
• JMK DOE(DE-FG02-04ER63821), NSF(DMI-0456537),
  and the Michigan Space Grant Consortium
• DJC Argonne National Laboratory
• HSF / VT Vennema Professorship and
  Thurnau Professorship

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Module Hwk Solution

• How many kJ are there in a K cylinder of H2?
• Assume liquid water product, DHr,H2O -286
  kJ/mol
• From ideal gas law, cylinder contains n 278
  mol
• Energy content -n DHr,H2O 79000 kJ

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Module Hwk Solution

• How many gallons of gas is this equivalent to?
  Assume 112 g/mol and density 0.69 g/cm3
• Recall gasoline heat of reaction -5370 kJ/mol
• Thus, hydrogen cylinder is equivalent to 14.7
  mol gasoline
• Converting to mass we have 1646 g and then
  converting to volume gives 0.63 gal

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Module Hwk Solution

• How many gallons of water do you make in a fuel
  cell?
• Stoichiometry tells us 278 mol of H2 react to
  form 278 mol H2O
• This is equivalent to 5000 g or 1.32 gal

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Module Hwk Solution

• What is the maximum time you could power a 100 W
  laptop with this H2 cylinder?
• To determine the upper bound on time we assume
  all hydrogen is converted into electricity (100
  efficiency).
• At a power of 100 W, 79000 kJ of energy would be
  consumed in 219 hours. In reality, you could
  expect the fuel cell to operate for 100 hours.