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The History of Fuel Cells
Electrolyser Grove’s Gas Battery(first fuel cell, 1839)(after Larminie and Dicks, 2000)
Distributed power stations
Photo courtesy of Ballard Power Systems
250 kW distributed cogeneration power plant
Applications for Fuel Cells
Home power
Photo courtesy of Plug Power
7 kW home cogeneration power plant
Applications for Fuel Cells
The Science of Fuel Cells
Phosphoric Acid
(PAFC)
Alkaline(AFC)
Polymer Electrolyte Membrane
(PEMFC)
Direct Methanol
(DMFC)
Solid Oxide
(SOFC)
Molten Carbonate(MCFC)
Types of Fuel Cells
Polymer Electrolyte Membrane(PEMFC)
Direct Methanol(DMFC)
Solid Oxide(SOFC)
PEM Fuel Cell Electrochemical Reactions
Anode:
H2 2H+ + 2e- (oxidation)
Cathode:
1/2 O2 + 2e- + 2H+ H2O (l) (reduction)
Overall Reaction:
H2 + 1/2 02 H2O (l)
ΔH = - 285.8 kJ/mole
Membrane Electrode Assembly (MEA)
O2
2H2O
4H+
Nafion
4e -
2
K
H2
O2
H2O
2H2 4H+
Nafion
4e -
O2
2H2O
4H+
Nafion
4e -
Nafion
H+
Catalysis
Transport
Resistance
Anode Cathode
Polymerelectrolyte
(i.e. Nafion)Carbon cloth Carbon cloth
Platinum-catalyst
Platinum-catalyst
Oxidation
Reduction
Polymer Electrolyte Membrane
(after Larminie and Dicks, 2000)
Polytetrafluoroethylene (PTFE) chains
Sulphonic Acid
50-175 microns(2-7 sheets of paper)
Water collects around the clusters of hydrophylic sulphonate side chains
Thermodynamics of PEM Fuel Cells
Change in enthalpy (ΔH) = - 285,800 J/mole
Gibb’s free energy (ΔG) = ΔH - TΔS
ΔG at 25° C: = - 285,800 J - (298K)(-163.2J/K)
= - 237,200 J
Ideal cell voltage (Δ E) = - ΔG/(nF)
ΔE at 25º C = - [-237,200 J/((2)(96,487 J/V))]
= 1.23 V
ΔG at operating temperature (80º C): = - 285,800 J - (353K)(163.2 J/K)
= - 228,200 J
ΔE at 80º C = - [-228,200 J/((2)(96,487 J/V))]
= 1.18 V
0dI
dP
Characteristic Curve
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4
I
V
Power Curve
0
0.5
1
1.5
2
2.5
0 1 2 3 4 5
I
P
MPP
x
Max Power Point (MPP):Factors Affecting Curve:
• activation losses
• fuel crossover and internal currents
• ohmic losses
• mass transport or concentration losses
ohmic losses
activation losses + internal currents
concentration losses
Hydrogen Storage
56 L
14 L
9.9 L
Liters to store 1 kg hydrogen
Compressed gas (200 bar)
Liquid hydrogen MgH2 metal hydride
Hydrogen: Energy Forever
Fuel tank Reformer
H2
Hydrogen bottles
H2
H2
Hydrogen bottles
H2
Algae
H2
Hydrogen bottles
H2
Solar panel Electrolyser
Renewable Energy Sources
As long as the sun shines, the wind blows, or the rivers flow, there can be clean, safe, and sustainable electrical power, where and
when required, with a solar hydrogen energy system
M icro hydro
Storage
H 2
Oxygen
Oxygen
WaterWater
FuelCellE lectro lyzer
Solar Cell
W ind
Heliocentris: Science education through fuel cells 22
Our Fragile Planet.
We have the responsibility to mind the planet so that the extraordinary natural beauty of the Earth
is preserved for generations to come.
Photo courtesy of NASA
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