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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. Electrolyser. Grove’s Gas Battery. (first fuel cell, 1839). (after Larminie and Dicks, 2000).
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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)
Photo courtesy of University of Cambridge Bacon’s laboratory in 1955
Photo courtesy of NASA NASA Space Shuttle fuel cell
Applications for Fuel Cells Transportation vehicles Photo courtesy of DaimlerChrysler NECAR 5
Applications for Fuel Cells 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
The Science of Fuel Cells Alkaline(AFC) Polymer Electrolyte Membrane (PEMFC) Phosphoric Acid(PAFC) Polymer Electrolyte Membrane(PEMFC) Types of Fuel Cells Molten Carbonate(MCFC) Direct Methanol (DMFC) Direct Methanol(DMFC) Solid Oxide(SOFC) 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
A Simple PEM Fuel Cell Hydrogen + Oxygen Electricity + Water Water
Membrane Electrode Assembly (MEA) C a t a l y s i s Oxidation - 4 e Platinum- catalyst T r a n s p o r t H 2 2 H + 2 4 H R e s i s t a n c e N a f i o n O 2 H O 2 Reduction Platinum- catalyst + H Anode K Cathode - - 4 4 e e O O Polymer electrolyte (i.e. Nafion) 2 2 N a f i o n + + Carbon cloth Carbon cloth 4 4 H H 2 2 H H O O 2 2 N N a a f f i i o o n n 2
Polymer Electrolyte Membrane Polytetrafluoroethylene (PTFE) chains Water collects around the clusters of hydrophylic sulphonate side chains Sulphonic Acid 50-175 microns (2-7 sheets of paper) (after Larminie and Dicks, 2000)
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 Power Curve activation losses + internal currents 1.2 MPP 2.5 ohmic losses 1 x concentration losses 2 0.8 1.5 P V 0.6 1 0.4 0.5 0.2 0 0 0 1 2 3 4 0 1 2 3 4 5 I I • Factors Affecting Curve: • activation losses • fuel crossover and internal currents • ohmic losses • mass transport or concentration losses Max Power Point (MPP):
Hydrogen Storage 56 L 14 L 9.9 L Compressed gas (200 bar) Liquid hydrogen MgH2metal hydride Liters to store 1 kg hydrogen
H2 H2 H2 H2 H2 H2 Fuel tank Reformer Hydrogen bottles Hydrogen bottles Hydrogen bottles Electrolyser Solar panel Algae Hydrogen: Energy Forever
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
The Benefits of Fuel Cells Clean Modular Quiet Benefits of Fuel Cells Safe Sustainable Efficient
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. Heliocentris: Science education through fuel cells 22 Photo courtesy of NASA