EML4450L15

EML4450L15 - S ustainable E nergy S cience and E ngineering...

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Unformatted text preview: S ustainable E nergy S cience and E ngineering C enter Direct Energy Conversion: Fuel Cells References: Direct Energy Conversion by Stanley W. Angrist, Allyn and Beacon, 1982. Fuel Cell Systems, Explained by James Larminie and Andrew Dicks, Wiley, 2003. Fuel Cell Technology Hand Book, Edited by Gregor Hoogers, CRC Press, 2002 S ustainable E nergy S cience and E ngineering C enter Introduction: Fuel Cells 3 5 6 Hydrocarbon Fuels Energy stored in chemical bonds Combustion Useful power Bypass the conversion-to-heat and mechanical-to-electrical processes A fuel cell is an electrochemical device in which the chemical energy of a conventional fuel is converted directly and efficiently into low voltage, direct current electrical energy. Since the conversion can be carried out isothermally (at least in theory), the Carnot limitation on efficiency does not apply. S ustainable E nergy S cience and E ngineering C enter 10 1 Fuel Cell Efficiency S ustainable E nergy S cience and E ngineering C enter Fuel Cells 10 1 William Grove 1839 Grove noted with interest that this device, which used platinum electrodes in contact with dilute sulfuric acid would cause permanent deflection of a galvanometer connected to the cell. He also noted the difficulty of producing high current densities in a fuel cell that uses gases. S ustainable E nergy S cience and E ngineering C enter Fuel Cells 10 1 Mond & Langer (1889) - Gas battery S ustainable E nergy S cience and E ngineering C enter Daniell Cell 1 2 3 4 5 6 7 9 10 1 11 We will use the term anode to mean the electrode at which oxidation takes place - losing of electrons Cathode is the electrode at which reduction takes place - electrons are gained from the external circuit S ustainable E nergy S cience and E ngineering C enter Fuel Cell 10 1 The common types of fuel cells are phosphoric acid (PAFC), molten carbonate (MCFC), proton exchange membrane (PEMFC), and solid oxide (SOFC), all named after their electrolytes. Because of their different materials and operating temperatures, they have varying benefits, applications and challenges, but all share the potential for high electrical efficiency and low emissions. Because they operate at sufficiently low temperatures they produce essentially no NOx, and because they cannot tolerate sulfur and use desulfurized fuel they produce no SOx. The Fuel Cell is a device which converts hydrogen or other fuel and oxygen into electricity. It achieves this using a process which is the reverse of electrolysis of water first identified by William Grove in 1863. S ustainable E nergy S cience and E ngineering C enter Historical Development 10 1 S ustainable E nergy S cience and E ngineering C enter Fuel Cell Types 1 2 3 4 5 6 7 9 10 1 11 S ustainable E nergy S cience and E ngineering C enter Hydrogen - Oxygen Fuel Cell 1 2 3 4 5 6 7 9 10 1 11 2 H 2 4 H 4 e At the anode the hydrogen gas ionizes releasing electrons and creating H + ions (or protons). This reaction releases energy....
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This note was uploaded on 10/22/2011 for the course EML 4450 taught by Professor Greska during the Fall '06 term at FSU.

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EML4450L15 - S ustainable E nergy S cience and E ngineering...

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