Fuel Cells
description
Transcript of Fuel Cells
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Fuel Cells
Presented By:
-Taylor Morton
-Chris Irvine
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Overview
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
• Not self contained
• Reactants enter cell
• Products leave cell
• Use combustion to produce electricity
• E- transferred
through external
circuit
Source: http://www.aerospaceweb.org/question/propulsion/jet/combustion.gif
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PEM(Proton Exchange Membrane)
• A.K.A. Hydrogen Fuel Cell• Operating temp. = 80ºC• Requires electrocatalyst• Electrodes
– Platinum based– Graphite– Sulfonated perfluroethylene
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QuickTime™ and aTIFF (Uncompressed) decompressor
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PEM continued• Anode: 2H2(g) ---> 4H+(aq) + 4e-
• Cathode: O2(g) + 4H+(aq) + 4e- ----> 2H2O(g)
• Overall: 2H2(g) + O2(g) ----> 2H2O(g)
• Process– 2 H2 absorbed
– 2 e- from each H2 travel externally
– 2H+ hydrate and migrate
– O2 absorbs e-
– O2- receives H+
– H20 formed
Source: http://physics.nist.gov/MajResFac/NIF/Images/FuelCellBasic.gif
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Efficiency
• No Pollutants• Other environmental impact
– How is H2 obtained?
• Viability– PEM = 75%– Coal-fired = 40%– Petroleum in ICE = 25%
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Microbial Fuel Cells
Using microorganisms to generate energy
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What it is!
• Converts chemical energy to electrical energy by the catalytic reaction of microorganisms
• Exact same principle as a voltaic cell, only using the respiration of bacteria to generate electricity
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Mediated
• Methylene Blue, thionine, or humic acid– Mediator acts as electrolyte– Facilitates e- transfer from microbial cells to the
electrode– Mediator is necessary because most microbes
are electrochemically inactive
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It’s just science
• mediator crosses the outer membrane
• Accepts e- that would normally be taken up by O2
• e- laden mediator exits cell and transports e- to anode
• after e- deposition, mediator returns to original oxidized state
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Mediator-less: S. putrefaciens
• Electrochemically active bacteria usually have cytochromes (or other redox enzyme) in their outer membranes that can transfer e-
• e- are carried directly to the anode
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C12H22O11 + 13H2O ---> 12CO2 + 48H+ + 48e-
• The biofilm is attached to the anode
• Anaerobic conditions force bacteria to respire anaerobically (duh)
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Now what?
• Waste Water Plants
• Power stations based on plants/algae