To Build Tomorrow’s Fuel
Cell Start with Tomorrow’s
Fuel Cell Engineer - Part II
Eric M. Stuve,
Per G. Reinhall,
Joyce S. Cooper,
Daniel T. Schwartz
Departments of Chemical and Mechanical Engineering
University of Washington
http://faculty.washington.edu/stuve/
Fuel Cell Design Experience
• Fuel Cell Ugrad. Research (1991-1996)
– Single cell MEA-PEM development
10
• Fuel Cell Design Project (1996-pres.)
Part I
– ChemE capstone design special project
– ME capstone design & ugrad. research
– EE & MSE students
50
114
9
• Fuel Cell Engineering (1998-pres.)
Part II
– Lecture / HW / project course
– Technical support for F/C project
– UW students
83
– Distance learning (EDGE) students
67
(Ballard, UTC-Fuel Cells, Honeywell, Ford, etc.)
Technical Goals
• H2/air fuel cell system, fully contained
– 10 kW (100 Amps @ 100 Volts)
– Proton exchange membrane (PEM) system (80 °C)
– Safe for student operation in public arena
• Application: Prime mover for a locomotive
– 18 in. gauge (approx. 1/3 scale)
– Pull two passenger coaches
– Use for Open House demonstrations
• Other applications
– SAE car, radio, H0 scale train, etc.
MEA Preparation
H O
2 2
NaCl
Soak
Clean
Na+ form
Glycerol
TBOH
MeOH
Nafion
soln.
Sonicate
Binder
N
2
Dry
DI H2 O
soak.
H2SO4
100 C
H+ form
Hot Press
130 C
Single Cell Data
1.0
A: MEA w/ ID-FFP
B: MEA w/ serp-FFP
0.26 A/cm2 at 0.6 V
0.8
E/ V
0.6
0.4
B
A
0.2
0
0
0.2
0.4
0.6
j / A cm–2
0.8
1
Carl Ljungholm
Matt Thompson
Elisa Baris
Chris Green
Christy Silverman
Greg Martin
Jon Bumgardner
Small Test Stand
Large Test Stand
Fuel Cell
Engineering
Course
• UW & Distance Learning
Students Worldwide
• Course Outline:
– Principles of
electrochemical energy
conversion
– Single cells
– Stack engineering
– Systems engineering
– Safety concerns
Distance Learning
• Students sign up through UW-EDGE or NTU
– EDGE for non-matriculated students (cheaper: $1,467 per course)
– NTU for M.S. students ($1,950 per course)
• Lectures
– Streaming video (firewalls pose difficulties)
– VHS or CD-ROM (delivery delay)
•
•
•
•
Electronic course notes (pdf format; password protected)
Homework submitted by e-mail or fax
Exams proctored on-site and submitted by fax
Instructor contact by e-mail or phone
Two Principles of the Course
1. Chemoelectricity*
Chemistry must occur before energy flows
F/C system like an entire chemical plant
2. Match Energy Source to Application
Different cells for different applications
Stationary / Vehicular / Portable
Sometimes F/Cs won’t work (airplanes)
*No, it’s not a cancer treatment!
Road Map for Quarter
Exhaust
Purge
Single Cell
Recycle
Compressor
F
Stack
Humidifiers
System
H2
Air
Compressor
Radiator
80 °C
T
Model of Springer, et al.
N H 2 ,out
N wA ,out
Anode
GDL
T=800 C
N H 2 ,1
PEM
PA
TA,in
xwA ,in
Cathode
GDL
H+
H2
H 2 N H ,in
2
H 2O
N wA,in
3
Make H2O
N wC ,out
H 2O
H 2O diff
2
N N 2 ,out
O2
H 2O drag
H 2O
1
N O2 ,out
4
PC
N air,in O2 N 2 TC ,in
N wC ,in
H 2O
xwC ,in
43
Cell Diagnostics
1.0
a
(E – jR m) / V
b
d
c
0
1.
2.
3.
4.
0
1
j / A cm –2
H2/Air
H2/5.2% O2, N2
H2/O2
H2/13.5% O2, N2
3/5 atm
3/5 atm
3/5 atm
3/2 atm
2
103
Stack Manifolding
O2
Manifold
Stack
H2
H2
Corner
gasket
O2
H2O
121
Serpentine Flow Fields
• One or more channels make multiple passes
over MEA in serpentine configuration
• Must specify number of parallel channels, nch =
1, 2, 3, etc.
L
W
nch = 1
nch = 2
142
Heat Transfer in the FFP
• Examine case for simple parallel FFP
• Do 1-D energy balance:
z
y
Ambient fluid
Tb
x
Solid Phase
Ts(x)
x
Ta(x) or Tc(x) – gas temp.
• Assumptions
- T constant along y direction
- Ts = temp. of solid phase = Ts (x)
146
Energy Balance for Solid Phase
 U b Ts ( x)  Tb Wx
Ambient fluid
dTs
 ks
As
dx x
Tb


Uk Ts (x)  Tk (x)
dTs
 ks
dx
As
x  x
1
2
QhWx
2(h  w)nch x
generation
As = area of solid phase
149
Chilton-Coburn Analogy
Mass Transfer
jD 
Sh
Re Sc 2 / 3
Sh  Sherwood Number
k RTD
 x
PT DAB
Sc  Schmidt Number


DAB
Heat Transfer
jH 
Nu
Re Pr 2 / 3
Nu  Nusselt Number
hD

k
Pr  Prandtl Number
Cp 

k
k x  dilute mass trans. coef.
moles
[]
area time mole  fraction
Variations Along the MEA
H
(–)
x
2
MEA
dry
hydrated
E
O
2
Suppose membrane hydration increases…
l
sm
Em
h
=>
=>
=>
=>
sm
Em
h
j
(+)
(at const. j)
(at const. Eoc,E)
(redist. of j, Em, h)
Em
h
o
E
E
Results of Yi and Nguyen
Cathode
3
0.9
liq
M w,c /
Pw / atm
0
0
3
j / A cm
vap
M w,c
–2
<j> = 1.1
0
0.9
Pw / atm
Anode
Base case:
0
0
x / cm
10
E = 0.53 V; gas enters cathode dry
<j> = 1.1 (specified)
Flow & Control Systems
Air
H 2O Recov.
Purge
M
Turbocharger
Flow meter
Stack
Motor
F
H
Memb
H
F
Flow Resistor
Heat
Exch.
Humid.
(2x)
Humid
Ejector
H
2
Level
L
Radiator
T
Flow control
H O
2
Anode Water Removal
Air
Turbocharger
M
Hum.
F/C
De-ionizing
Filter (2x)
H
2
Cooling Water
H O
2
Recycle Compressor
Ballard Anode Water Removal System
U.S. Pat. 5,366,818
Purge
Hydrogen Safety
• Flame velocity very fast: 265-325 cm/s
- Compare with methane: 37-45 cm/s
- Large problem of backflashes
H2
flame
Air
- Backflash: motion of flame front backwards
through system … this pulls outside air in and
can cause internal explosions
- To prevent backflash, gas must be supplied at a
velocity greater than flame velocity
• Small minimum flame diameter: 0.6 mm
- Min. diam. through which flame can pass
- Compare with methane: 2 mm
HW: Nexa™ vs. Honda
Determine:
Rated elec. Power
output / W
Size / in3
Weight* / lb
Fuel
Fuel capacit y*
Fuel tank vol.* / cu. ft.
Gene rating time on
one tank a t full l oad
Balla rd Nexa
1200
Honda EU1000 iA2
1000
22 x 10 x 13
27 + 20
Hyd rogen
30 scf
0.26
17.7 x 9.4 x 15.0
29
Gasoli ne
0.6 gal.
Included in size above
3.8 hours
• Energy density of each generator
• Power density of each generator
• Thermodynamic efficiency of Honda
generator (assumer Nexa is 41.5%)
• Discuss relative merits of each generator
– Technical advantages and disadvantages
– Marketing advantages and disadvantages
– Neglect price for the moment
HW: Graphite vs. SS FFP
3.0 mm
MEA
Junction of two
graphite plates,
each 1.5 mm
thick
Cathode/anode
gas channels,
4 mm x 4 mm
Cooling
channel,
1 mm x 8 mm
Graphite FFP
MEA
Operating conditions:
• 0.65 V; 0.6 A/cm2; 80 °C
• Cooling air enters at 40 °C
• Max. P of cooling air: 0.3 atm
SS allows 0.5 mm wall thickness;
cooling channels change, fuel/air
channels remain the same
For each FFP determine:
• Cooling air flow rates
• Cooling air h.t.c.
• Overall h.t.c.
• Exhaust temp. of cooling air
• Parasitic load of cooling (assume
20% blower efficiency)
• Compare performance; is one
material superior to the other?
F/C Project: Seaglider
Lead-In Courses &
Institutional Support
CHEM E / ENVIR / M E / PHYS
341, 342
Energy and Environment I, II
Interdisciplinary Fuel Cell
Design Experience
Outcomes
CHEM E 445 (1998-)
Fuel Cell Engineering
83 UW students
67 Distance Learning students
M E 430
Advanced Energy Conversion
Capstone Design Project
CHEM E 461
Electrochemical Engineering
CHEM E 485
Process Design I
M E 395
Introduction to Mechanical
Design
M E 415
Sustainability and Design for the
Environment
Institutional Support:
CHEM E, ME, CoE
NSF-ECSEL
CHEM E 497 (1996-)
Special Projects in Chemical
Engineering Design
50 students
M E Design & Research (1996-)
Mechanical Engineering Design
114 students
Other Engineering Design
EE – 6 students
MSE – 3 students
Graduate Program
(Participating faculty: Adler,
Bordia, Cooper, Jenkins,
Kramlich, Malte, Overney,
Reinhall, Schwartz, Stuve)
Lifelong Learning
Training to F/C industry
Jobs in F/C Industry
16% of students in F/C industry
UTC Fuel Cells
Plug Power
Idatek
Honeywell
CHEM E Core Curriculum
F/C system for undergraduate lab;
all students to study fuel cells
External Support
Dreyfus
UTRC
Ford
UTC Fuel Cells
Honeywell
What’s in the Future?
• ChemE Curriculum Development
–
–
–
–
F/C is excellent example of integrating teaching & research
Project work & course development spawn research ideas
Specific F/C applications are examples of product design
Improve project management and work skills of students
• UW F/C Research Development
– 10 faculty (ChemE, ME, & MSE) working on PEM, SOFC,
LCA, fundamentals
– Pacific Northwest Energy Institute (Engineering, Business,
Economics, Environmental Policy)
• F/C Curriculum Development
– Certificate program in F/C Engineering
Intro, F/C Engr., SOFC, Power Engr., Adv. F/C Engr.
– Available worldwide through EDGE
Acknowledgements
•
•
•
•
•
•
•
•
All the students!!!!
Russ Noe and the ME student shop
Bruce Finlayson (ChemE)
Reiner Decher (A&A), Rich Christie (EE), Brian Flinn
(MSE), Sossina Haile (MSE; now at Cal Tech)
NSF-ECSEL for major funding
ChemE, ME Depts; College of Engineering
Dreyfus Foundation
Industrial Support
–
–
–
–
–
UTRC
Ford
UTC Fuel Cells
Siemens
Honeywell