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1. Fuel Cells: Basics and Applications
&
How do fuel cell cars work?
Ajay K. Prasad
Professor, Department of Mechanical Engineering
Director, Center for Fuel Cell Research
University of Delaware
prasad@udel.edu

2. What is a Fuel Cell?
• A fuel cell combines fuel and oxidant electrochemically to produce
electricity
• Two to three times more efficient that an internal combustion engine
• Fuel cell stack is quiet, has no moving parts, produces zero
emissions
Fuel Cell
Hydrogen Oxygen
Water
Electric power
Heat
Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware

3. Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware
Voltage = 0.6 V
PEM fuel cell
Cathode Reaction
O2 + 4H+ + 4e-  2H2O
Air
Anode
Cathode
e-
Membrane
Electrode
Assembly
Gas Diffusion
Layer
Gas Diffusion
Layer
H2
Bipolar
plate
Bipolar
plate
Load
H+
Anode Reaction
2H2  4H+ + 4e-
NIST
Platinum
Catalyst
Carbon
black

4. 3kW, 48V
fuelcellstore.com
PEM fuel cell “stack”
A small stack of about 10 cells
NMSEA
NREL
Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware

5. GM’s skateboard
chassis idea.
Honda FCX Clarity
Automotive fuel cells (PEM)
Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware

6. Mercedes-Benz: Citaro fuel cell bus on the
streets of London. Engine supplied by
Ballard.
European Fuel Cell Bus Project, which saw
30 fuel cell buses operating on the roads of
Europe over the past two years.
Toyota: The FCHV-BUS2
is a large, low-floor, fuel-
cell hybrid bus.
Since its exhaust is free
of NOx (nitrogen oxides)
and PM (particulate
matter), it can help
improve air quality in
urban areas.
Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware

7. Casio: World's smallest fuel cell for
use in laptop PC. The polymer
electrolyte fuel can power a typical
laptop computer for eight to 16 hours.
Samsung Electronics: 100Wh laptop PC fuel cell using 100cc of methanol
solution, enabling continuous usage for more than 10 hours without recharging.
Fuel cells for portable power (DMFC)
Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware

8. Fuel cells for stationary power (SOFC)
UTC Fuel Cells: 5kW
fuel cell power plants
for backup power for
telecommunications
towers, power for
small businesses,
and residential use.
Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware
UTC Fuel Cells: (PureCell™ 200) 200kW of electricity
and 900,000 BTUs of usable heat. This system
provides clean, reliable power at locations including a
New York City police station, a major postal facility in
Alaska, a credit-card processing system facility in
Nebraska, and a science center in Japan.

9. Pros and Cons of Fuel Cells
Advantages
of Fuel Cells
1. Higher efficiency compared to IC engines
2. Zero emissions at the point-of-use
3. No moving parts in the stack, so quieter
Challenges
Facing Fuel
Cells
1. Cost (materials, labor, economy of scale)
2. Durability (membrane, catalyst)
3. Lack of H2 Infrastructure: H2 is difficult to
produce, transport, and store
Fuel Cell Technology: Basics and Applications © Prof. Ajay K. Prasad University of Delaware

10. UD Fuel Cell Hybrid Bus Program
UD Fuel Cell Bus Program: 2005-2011
•Phase 1: 22-ft bus, 20 kW stack, Ni-Cad
batteries (in operation, 100 students/day)
•Phase 2: 22-ft bus, 40 kW stack, Ni-Cad
batteries (Spring ’09)
•Phase 3: 30-ft bus, 40 kW stack, Li-Ti batteries
(2010)
•Phase 4: 30-ft bus, 40 kW stack, Li-Ti batteries
(2011)
H2 Refueling
station at
Air Liquide
• H2 refueling station in Newark since 2007
• Two more H2 stations in Wilmington and Dover

11. How do fuel cell cars work?
Components of a
fuel cell car
•Fuel cell stack
•Balance of plant:
Air compressor,
hydrogen
recirculating pump,
air and hydrogen
humidifiers, coolant
pump and radiator
•Hydrogen storage
tank
•Battery for hybrid
operation
•Boost converter
and inverter
•Traction motor and
transmission
•Computer for
control and
management

12. Schematic of direct-hydrogen pressurized FCS
R.K. Ahluwalia et al. / Journal of Power Sources 152 (2005) 233–244

13. Schematic of electric drive train for FCHEV
R.K. Ahluwalia et al. / Journal of Power Sources 152 (2005) 233–244

14. Energy Flow within components for FCHEV
Energy flow within the components of FCHEV for FUDS: FCHEV with 65kWe FCS
and 55kWe ESS. R.K. Ahluwalia et al. / Journal of Power Sources 152 (2005)
233–244

15. Requirements for FCHEV
To be competitive with the conventional ICE propulsion system
in terms of drivability and performance, the FCS must satisfy
the following requirements:
• FCS alone must meet vehicle power demands under all
driving conditions: Top sustained speed of 100 mph, and 55
mph at 6.5% grade for 20 min.
• With the assistance of ESS, the FCS must allow 0 to 60
mph in 10 s.
• 1 s transient response time for 10–90% power.
• FCS must reach maximum power in 15 s for cold start from
20 ◦C ambient temperature, and in 30 s from −20 ◦C
ambient temperature.

16. Series and Parallel Hybrid Fuel Cell Vehicles
Series Hybrid:
•Small fuel cell, large battery
bank
Battery drives motor at all times
•Fuel cell operates continuously
and keeps battery charged
•Fuel cell is not “load-following”
Parallel Hybrid:
•Large fuel cell, small battery
bank
•Fuel cell drives motor at all
times, it is “load-following”
•Battery provides boost power
as and when required

17. The Honda FCX Clarity
Engine: 100 kW, 57 liters, 148 lb
Fuel economy: 74 mpgge
Range: 280 miles
H2 Storage: 4.1 kg at 5000 psi