Hydrogen Fuel Cell

Trends in the Use of Fuel

Wood Coal O il NaturalGas

Hydrogen

Percentage of hydrogen content in fuel

19th century: steam engine

20th century: internal combustion engine

21st century: fuel cells

The History of Fuel Cells

Electrolyser Grove’s Gas Battery(first fuel cell, 1839)(after Larminie and Dicks, 2000)

Bacon’s laboratory in 1955

Photo courtesy of University of Cambridge

NASA Space Shuttle fuel cellPhoto courtesy of NASA

Applications for Fuel Cells

Transportation vehicles

Photo courtesy of DaimlerChrysler

NECAR 5

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

Portable power

50 W portable fuel cell with metal hydride storage

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

Hydrogen + Oxygen Electricity + Water

Water

A Simple PEM Fuel Cell

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

Benefits of Fuel Cells

Modular

Clean

Quiet

Sustainable

Efficient

Safe

The Benefits of Fuel Cells

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

Presentation courtesy of Heliocentris