Some Basic Concepts Related to Fuel Cells with an Emphasis
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Transcript Some Basic Concepts Related to Fuel Cells with an Emphasis
Some Basic Concepts
Related to Fuel Cells
with a Focus
on Microbial and Enzymatic
Fuel Cells
Nevin Longenecker
John Adams High School
The PURPOSES of this
investigation were to
examine and evaluate variables associated with
increasing the efficiency of a microbial fuel cell .
propose and construct a prototype enzymatic fuel
cell based on the previous findings.
describe in an educational science journal an
inexpensive fuel cell which could be easily
constructed and used in a classroom. The
operation of such a cell would have diverse
applications in many sciences and would
integrate mathematical principles from calculus,
statistics, algebra and geometry.
Advantages of Fuel Cells
vs.
Internal Combustion Engines
Unlimited
supply of fuel
No reliance on foreign oil
Little or no pollutants
Much higher energy conversion %
No moving parts
No noise
Often Platinum Catalyst
V V
<-
Anode Chamber -->
Cathode Chamber
– Exposed to air
– Stores fuel
Membrane -^Allows for H+ passage
Microbial Fuel Cells
Procedures
A prototype microbial fuel cell was
designed and built. (next slide)
Factors affecting microbial fuel cell
efficiency were measured and evaluated.
– Surface area of electrodes
– Bacterial conc. on anode/in solution
– Aerobic vs anaerobic conditions
– Supplemental O2 sources
Single and mixtures of enzymes were tested in
the prototype cell to compare power output.
Significant Factors Affecting
Microbial Fuel Cell Operation
Type of electrodes
Surface area of electrodes
Use of catalysts on electrodes and PEM
Conc. of hydrocarbon in anode chamber
Agitation of hydrocarbon molecules
Rate of replacement of hydrocarbons
Types of microbes/enzymes
Conc. of microbes/enzymes
Examples of microbial-based fuel cells
Microbe
Substrate
Mediator
Anode
Voltage
E coli
Glucose
Methylene
Blue
Pt- C-cloth
625mV
Bacillus
subtilis
Glucose
Thionine
Vitreous
Carbon
640mV
E coli
Acetate
Neutral red Graphite
felt
250mV
550mV
Pseudomona Methane
s
methanica
1-Naphthol-2Sulfonate indo2,6
dichlorophenol
Pt-black
Proteus
vulgaris
Thionine
Carbon rod 350mV
Sucrose
Significant Factors Affecting
Microbial Fuel Cell Operation
Types
of mediators
Conc. of mediators
Distance between electrode and PEM
Type of proton exchange
membrane(PEM)
Surface area of PEM
Source of oxygen
Temperature effects
Pseudomonas sp.
Mediator Shuttling Electrons
Types of Electrodes
Power Output C rod vs
C cloth -aerobic E coli
1.6
Cloth Elec
1.4
C Rod Elec
mWatts/cm2
1.2
1
0.8
0.6
0.4
0.2
0
0
5
10
15
Time Hrs
20
25
Carbon Rod and Carbon Fiber
Electrodes
Power Output of C rod Biofilm vs
C rod Solution –anaerobic Ecoli
180
160
C rod biofilm
Solution Bacti
mWatts/cm2
140
120
100
80
60
40
20
0
0
5
10
15
Time(hrs)
20
25
Proposed Advantages of Enzyme Use
1. Immediate contact with substrate
2. Elimination of metabolism of
substrate by bacteria
3. Elimination of possible mixing of
hazardous bacterial types
4. If immobilized on electrodes, no
mediators are required.
Immobilized Enzyme /Cathode
Interaction
Glucose Dehydrogenase
Partial Composition of PEB
Enzyme Solution
Lipase
Protease
Amylase
Hydrolase
Likely-dehydrogenases,
lactase,
decarboxylase, invertase
Supplied by Enzyme Solutions, Inc
PEB EnzymeTrial –anaerobic-C rod
3
2.5
watts/m2
2
1.5
1
0.5
0
0
10
20
30
40
Time(hrs)
50
60
70
PEB Trial C rod Cathode vs Pt Cathode
3
2.5
Trial #1 C Rod
Trial #2 Pt
Watts/m2
2
1.5
1
0.5
0
0
10
20
30
40
50
Time Hrs
60
70
80
90
100
Total Power Output in 22 hrs
Watts ( meter2)
2500
2000
1500
1000
500
0
0.56
1.11
2.22
4.44
PEB conc. pph anode solution
8.89
Long Term PEB Enzyme Action
4
3.5
3
Watts/m2
2.5
Watts/m2
2
1.5
1
0.5
0
0
20
40
60
Time -Hrs
80
100
120
PEB Investigation Trends and
Conclusions
1. Optimum power output developed in 2hrs
Whole Ecoli cells
PEB solution
0.2 watts/m2
2.1 watts/m2
2. Prolonged power output at 24 hrs
0.14 watts/m2 2.05 watts/m2
3. Prolonged optimum power output continued for 5
days.
4. Pt. coating on the anode did not improve the
efficiency of the enzymatic cell.
Uses for
Implantable Enzymatic Fuel Cells
(To utilize arterial glucose and oxygen with
immobilized enzymes on electrodes in a
noncompartmentalized cell)
Micropumps-insulin, pain meds, arthritis
Current for-nerve stimulation, hearing aids
Heart pacemaker (cells in series)
Immobilized Enzymes on
Electrodes
Implantable Arterial Fuel Cell
Additional Uses of
Enzymatic Fuel Cells
Space-regeneration
of human waste
Treatment of human waste in
developing countries
Treatment of household wastes in
place of landfills
Industry-detoxify chemical wastes
Portable units- power generation
Acknowledgments
University
of Notre Dame
RET Program
Dr. Alex Hahn
Dr. Robert Nerenberg
Dr. Valli Sarveswaran