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Transcript of microbialfuelcells-120227204600-phpapp01
Microbial Fuel CellsPaul BentzKevin Cao
ConceptBacteria convert substrate into electrons.The electrons run through the circuit and to
power the load.The byproducts include carbon dioxide,
water, and energy.
ComponentsAnodeCathodeExchange membraneElectrical circuit
AnodeThe bacteria live in the anode
and convert substrate to carbon dioxide, water, and energy.
Various things like glucose and acetate can be used.
The bacteria are kept in an oxygen-less environment to promote the flow of electrons through the anode.
Electrical CircuitAfter leaving the anode, the electrons travel
through the circuit.These electrons power the load.The voltage multiplied by the current shows
the power.
Exchange MembraneThe protons that the bacteria
separated from the electrons flows through the exchange membrane.
They recombine on the other side.Can be a proton or cation exchange
membrane.
CathodeThe electrons and protons
recombine at the cathode.Oxygen is reduced to water.A platinum catalyst is used so
the oxygen is sufficiently reduced.
Video
ReactionsBEAMRHydrogen evolution reaction
BEAMRUtilizes electrohydrogenesis, which uses an
anaerobic environment to produce pure hydrogen.
It uses about one ninth of the energy required by normal electrolysis.
It has many different names:Bioelectrochemically assisted microbial reactorBiocatalyzed electrolysis cellsMicrobial electrolysis cells
Hydrogen Evolution ReactionThe bacteria in the anode separate the
protons and electrons.This reaction occurs at the cathode, where
they recombine to form hydrogen gas.
HistoryM.C. Potter first performed work on the
concept in 1911 with E. coli at the University of Durham
In 1976 the current design was came into existence by the work of Suzuki
Operating ConditionsFunction well in mild conditionsOperate at 70-100°F
UsesBeer breweries produce biodegradable
wastewater, which MFCs clean.Desalinating waterCreating fertilizer
Environmental ImpactIf the variety of substrates is increased,
waste can be used to create more energy.Instead of big factory manufacturing,
fertilizer for farmers can be created with MFCs and common materials.
MFCs can be used to desalinate seawater without burning fossil fuels, although not very efficiently yet.
EfficiencyThe efficiency varies based on the substrate
used, but it can reach very high efficiencies.91% efficiency has been reached.
CostPower density = 150 mW/m2
Volume (MFC): 28 x 10^-6 m3
A/V-ratio: 25 m2/m3 Anode surface area (single chamber) = 7 x 10^-4 m2 Power = 0.165 mW
Cost of single-chamber fuel cell: (lab-scale) Toray paper (10x10 cm): $ 11 XC-72 (10x10 cm): $65 Others (perspex, glue, wire): $ 25 Total = $ 100
Cost per Watt = $ 600/mW
FutureMore types of substrateAmmonia-treated anodes
SubstrateCurrently there is a limit to what can be used
as a substrate for the bacteria.Scientists hope to increase these fuel types to
include things like sewage and manure.
Ammonia-Treated AnodesAnodes of MFCs are naturally
negative in charge.The anodes can be changed to
a positive charge by being treated with ammonia.
This will make the anode more receptive to the electron transfer from the bacteria.
The energy trade-off to produce this might not be worth the increase in production.
Bibliographyhttp://www.microbialfuelcell.org/http://www.engr.psu.eduhttp://microbialfuelcell.wordpress.com/http://www.sciencedaily.com/releases/
2008/01/080103101137.htmhttp://peswiki.com/index.php/
Directory:Penn_State_Microbial_Fuel_Cells_Produce_Hydrogen_from_Waste_Water
www.popsci.com/scitech/article/2009-08/microbial-fuel-cell-cleans-wastewater-desalinates-seawater-and-generates-power
http://www.fuelcells.org/info/summer2007.pdf