Fuel Cells and Fuel Cell Systems ME 1065 L. Schaefer
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Fuel Cells and Fuel Cell Systems
ME 1065L. Schaefer
Proton Exchange Membrane
Cathode: ½O2 + 2 e- + 2 H+ => H2O
Anode: H2 => 2 H+ + 2 e-
Overall: H2 + 1/2 O2 => H2O
Problems with PEMs/PEFCs
Hydrogen Tank Rupture
Direct Methanol
Cathode: 3/2 O2 + 6e- + 6H+ => 3 H2O
Anode: CH3OH + H2O => 6H+ + CO2 + 6e-
Overall: CH3OH + 3/2 O2 => 2 H2O
DMFCs, cont.
Alkaline
Cathode: 1/2 O2 + H2O + 2e- => 2 OH-
Anode: H2 + 2(OH)- => 2H2O + 2 e-
Overall: H2 + 1/2 O2 => H2O
AFCs, cont.
Phosphoric Acid
Cathode: ½ O2 + 2 H+ + 2 e- => H2O
Anode: H2 => 2H+ + 2e-
Overall: H2 + 1/2 O2 => H2O
Molten Carbonate
Cathode: 1/2 O2 + CO2 + 2 e- => (CO3)=
Anode: H2 + (CO3)= => H2O + CO2 + 2 e-
Overall: H2 + 1/2 O2 + CO2 => H2O + CO2
MCFCs, cont.
Solid Oxide
Cathode: 1/2 O2 + 2 e- => O=
Anode: H2 + O= => H2O + 2 e-
Overall: H2 + 1/2 O2 => H2O
SOFCs, cont.
Basic Summary of Four Types
Fuel Cell Summary
Fuel Cell Governing Equations Heat/Mass Transfer Electrochemical Electrical Network
Governing Equations Heat and Mass Transfer Model
Continuity, Momentum, Energy, Concentration
0)()()(
zw
yv
xu
zu
xw
zxv
yu
yzw
yv
xu
xxp
zwu
yvu
xuu
32
34)()()(
qz
Tk
zy
Tk
yx
Tk
xz
wCpT
y
vCpT
x
uCpT
)()()(
)()()(
)()()()()()(
,,, z
YD
zy
YD
yx
YD
xz
wY
y
vY
x
uY jmj
jmj
jmj
jjj
Governing Equations Heat and Mass Transfer Model, cont.
Continuity, Momentum, Energy, Concentration
0r
)vr(
r
1
x
)u(
)(1
)()(1
)()(1)(
x
vr
rrx
u
xr
ur
rrx
u
xx
p
r
vur
rx
uu
qr
Tr
rrx
T
xr
CpvTr
rx
CpuT
)(1
)()(1)(
)r
YDr(
rr
1)
x
YD(
xr
)vYr(
r
1
x
)uY( jm,j
jm,j
jj
Hydrogen Fuel Cell ValuesForm of Water Product
Temp (°C) Gibbs Free Energy of Formation (kJ/mol)
Max EMF (V)
Efficiency Limit (%)
Liquid 25 -237.2 1.23 0.83
Liquid 80 -228.2 1.18 0.80
Gas 100 -225.3 1.17 0.79
Gas 200 -220.4 1.14 0.77
Gas 400 -210.3 1.09 0.74
Gas 600 -199.6 1.04 0.70
Gas 800 -188.6 0.98 0.66
Gas 1000 -177.4 0.92 0.62
Performance Curves
Fuel Cell Buses
SOFC Fuel
Turbine Unit
Recuperator
DC
AC
Power Conditioning
AC
Air
Combustor
Air
Exhaust
Exhaust
SOFC SOFC Fuel
Recuperator
DC
AC
Power Conditioning
AC
Air
Combustor
Air
Exhaust
Hybrid Power
Cogeneration and Cascading Energy Systems
PV
SOFC
Turbine
Chiller
Boiler
Electricity
ChilledWater
Hot Water
Unexpected Places!
Figure for Example Problem
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