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Physics 470
Lecture
Hydrogen Fuel Cells
May 9, 2012
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The hydrogen fuel cell
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The PEM fuel cell
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Features of a fuel cell




Sir William Grove invented the fuel cell in
1839
Hydrogen gas is fed to the negative terminal
(the anode)
A catalyst helps the hydrogen to split,
sending its electrons through an external
circuit and the protons through an electrolyte

2H 2  4H  4e

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Features of a fuel cell



Oxygen combines with the electrons at
the positive terminal (the cathode) and
protons to form water


O2  4e  4H  2H 2O
The overall reaction combines hydrogen
and oxygen to produce electricity and
water.
2H 2  O2  2H 2O
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The proton exchange membrane
fuel cell




Has a high power density and low operating
temperature
The electrolyte is a specially treated polymer
(chemically related to Teflon) that conducts
only positive ions
The membrane must be hydrated (7 water
molecules for every proton conducted!)
The membrane is “poisoned” by carbon
monoxide
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The proton exchange membrane
fuel cell

The anode-membrane-cathode
assemblies are stacked for higher
voltage
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The PEM fuel cell
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PEM Fuel Cell Stack
10 kW Fuel Cell Power Supply
GENEPAC by PSA Puegot Citroën, France
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Other types of fuel cells




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Phosphoric Acid
Molten Carbonate
Solid Oxide
Alkali
See comparison chart from the
Department of Energy
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Compare Fuel Cell Types
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Fuel cell problems


PEM cells: Hydration of the membrane
requires careful water control and/or
pressurization (adds weight, complexity).
New membranes such as PBI may
require less water.
For all fuel cells, drawing large currents
reduces performance
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Fuel cell losses
V  E0  I R
Ohm’s Law Applet
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Which of the following
statements is FALSE?
A.
B.
C.
D.
Catalysts help fuel cells increase the gas
transport rate to the electrodes.
Fuel cells operate on the chemical reaction
that combines hydrogen and oxygen.
Fuel cells are like a battery with a
continuous supply of chemical reactants.
The only outputs of a fuel cell are water and
electrical energy.
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Which of the following
statements is FALSE?
A.
B.
C.
D.
Catalysts help fuel cells increase the gas
transport rate to the electrodes.
Fuel cells operate on the chemical reaction
that combines hydrogen and oxygen.
Fuel cells are like a battery with a continuous
supply of chemical reactants.
The only outputs of a fuel cell are water and
electrical energy.
Suppose a fuel cell has an internal resistance of 0.025 . What is the output voltage
when the ideal voltage is 12.0 V and the
current is 30 A ?
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A. 0.30 V
B. 0.75 V
C. 9.00 V
D. 11.25 V
Suppose a fuel cell has an internal resistance of 0.025 . What is the output voltage
when the ideal voltage is 12.0 V and the
current is 30 A ?
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A. 0.30 V
B. 0.75 V
C. 9.00 V
D. 11.25 V
V    IR
 12V   30A  0.025  
 12V  0.75V
V  11.25 V
Suppose a fuel cell has an internal resistance of 0.025 . What fraction of the power
is lost when the ideal voltage is 12.0 V and
the current is 30 A ?
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A. 2.5%
B. 3.6%
C. 6.25%
D. 12.0%
Suppose a fuel cell has an internal resistance of 0.025 . What fraction of the power
is lost when the ideal voltage is 12.0 V and
the current is 30 A ?
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Ploss  I R
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A. 2.5%
B. 3.6%
C. 6.25%
D. 12.0%
  30 A   0.025  
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Ploss  22.5 W
22.5 W
% loss 
12 V  30 A 
22.5 W

 100  6.25%
360 W
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Stationary Power Fuel Cells
Biogas-powered
fuel cell power
plant, Sierra
Nevada Brewing
Co, Chico, CA
Fuel Cell
power plant,
Santa Rita
Jail, Dublin,
CA
200 kW fuel
cell, Central
Park, NY
police station
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Fuel Cell-Powered Zero Emission
Vehicles
Ford Focus FC5
Fuel Cell Car
Hyundai FC Tucson
Thor UTC Bus
Honda FCX Clarity
Several other fuel cell cars in this 2008 article. More links at fueleconomy.gov.
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Fuel cell airplane
DLR Antares, the world’s first fuel-cell-only aircraft,
takes off July 7, 2009 in Hamburg, Germany.
Boeing fuel cell aircraft first flight: April 3, 2008.
It used a battery to assist the takeoff.