Hydrogen Fuel Cell

Trends in the Use of Fuel

19 th century: steam engine 20 th century: internal combustion engine 21 st century: fuel cells

The History of Fuel Cells ElectrolyserGrove’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 cell Photo 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: H 2 2H + + 2e - (oxidation) Cathode: 1/2 O 2 + 2e - + 2H + H 2 O (l) (reduction) Overall Reaction: H 2 + 1/2 0 2 H 2 O (l) ΔH = kJ/mole

Hydrogen + Oxygen  Electricity + Water Water A Simple PEM Fuel Cell

Membrane Electrode Assembly (MEA) O 2 2H 2 O 4H + Nafion 4e - 2 K H 2 O 2 H 2 O 2H 2 4H + Nafion 4e - O 2 2H 2 O 4H + Nafion 4e - Nafion H + Catalysis Transport Resistance Anode Cathode Polymer electrolyte (i.e. Nafion) Carbon cloth Platinum- catalyst Platinum- catalyst Oxidation Reduction

Polymer Electrolyte Membrane (after Larminie and Dicks, 2000) Polytetrafluoroethylene (PTFE) chains Sulphonic Acid 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

Characteristic Curve I V Power Curve 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 hydrogenMgH 2 metal hydride

Hydrogen: Energy Forever Fuel tankReformer H2H2 Hydrogen bottles H2H2 H2H2 H2H2 Algae H2H2 Hydrogen bottles H2H2 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

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