CACHE Modules on Energy in the Chemical
Engineering Curriculum: Fuel Cells
Jason Keith1, Don Chmielewski2,
H. Scott Fogler3, Valarie Thomas3
1
Department of Chemical Engineering
Michigan Technological University
2 Department of Chemical and Biological Engineering
Illinois Institute of Technology
3 Department of Chemical Engineering
University of Michigan
Outline
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Introduction and Motivation
What is in each module?
Where are the modules?
What are the modules?
Module walk-through
Conclusions / Acknowledgments
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 ChE’s 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
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
Where are the modules?
• Current beta test website:
http://www.chem.mtu.edu/~jmkeith/fuel_cell_curriculum
• Currently available for use by anyone!
• Ultimately linked through CACHE website
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
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
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
Module walk-through
• How long can you power a laptop computer with
a type K hydrogen cylinder (49.9 L)?
Computer
(Electric Load)
H2 feed line
Air in
Anode
Gas
Chamber
Cathode
Gas
Chamber
H2 and H2O out
H2 tank
Fuel Cell
Air out
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
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
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
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?
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
• 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
• Rest of step-by-step solution available at end of
talk
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
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
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
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
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.