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6-Mar-15 Rohit Gupta/IIT(BHU), Varanasi 1
Energy Efficient Ceramic Electrolyte fuel cell system with enhanced Power Density for IT-SOFC application
Rohit Gupta Senior Undergraduate Student
Indian Institute of Technology(BHU), Varanasi
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INTRODUCTION AND WORKING
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WHY SOFC ?
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Various salient features Fuel cell stack(SOFC) Conventional Power Source Charge carrier Ions Electrons Power transfer Easy and economical as Fuel cell
can be carried along Neither easy nor economical
Eco-friendly Yes No Fuel Natural gas, Biogas, propane etc. Conventional sources
Harmful Emission No Yes Long-term stability Yes No
Fuel flexibility Yes No By products Heat and water No such useful by product Efficiency Max 70% Max 30%-40%
Power Transmission Loss Negligible Significant
Table 1 - Comparative study of fuel cell and conventional power source
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APPLICATIONS OF SOFC
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Solid oxide Fuel Cell
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WHY SOFC ? (Contd.)
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CHALLENGES
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Two class of challenges
Challenges associated with:
1. Electrolyte 2. Cathode Optimization of sintering temperature Density Porosity
Ionic Mobility Surface Area Working Temperature Current Density
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SYNTHESIS PROCESS OF ELECTROLYTE
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Powder (10 gm)
Binder Alumina
balls Solvent
Ball milling
Slurry Filtering Slurry
Kept at hot plate at 80 C for 1 day
Granulating
0.5 gm for each sample Compacted sample Final sintered sample
Compaction
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RESULTS AND DISCUSSION (Electrolyte) XRD Analysis
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RESULTS AND DISCUSSION (Electrolyte) Density Measurement
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Sintering Temperat
ure
Dry Weight (W1)
Weight in air
(W2)
Weight in
Water (W3)
Experimental Density
% Relative Density
1350oC 0.9754 0.9801g
0.8288g
6.44gm/cc
88.95
1400 oC 0.9163g
0.9695g
0.8230g
6.50gm/cc
89.77
1450 oC 0.8927g
0.9734g
0.8342g
6.32gm/cc
87.3
1550 oC 0.9529g
0.9598g
0.8018g
6.80gm/cc
93.93
1600 oC 0.4789g
0.5350g
0.4560g
6.31gm/cc
87.1 1350 1400 1450 1500 1550 1600 165087
88
89
90
91
92
93
94
95
96
97
Rel
ativ
e D
ensi
tySintering Temperature
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RESULTS AND DISCUSSION (Electrolyte) SEM Micrographs
Sintered at 1350 C
Sintered at 1550 C
Sintered at 1400 C
Sintered at 1600 C
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RESULTS AND DISCUSSION (Electrolyte) Impedance Analysis
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RESULTS AND DISCUSSION (Electrolyte) Ionic Conductivity and Power Density
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SYNTHESIS PROCESS OF CATHODE
Strontium (II) Nitrate
(aq.) Cobalt (II)
Nitrate Hexahydrate
(aq.)
Iron (III) Nitrate Nonahydrate
(aq.)
Lanthanum (III) Nitrate
Hexahydrate (aq.)
Stirred on a hot plate
L-alanine
After vigorous stirring
Viscous gel formed
On instantaneous burning
Produce Ash
Calcination at 800 C for 4 hours in air
Calcined powder
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SYNTHESIS PROCESS OF CATHODE (Contd.)
Calcined powder
Phase pure batch A
Ball milling
Composite Paste
Dried paste Binder Pressing Sample
Sintering (1050-
1150 C)
Final Samples
La0.54Sr0.4Co0.8Fe0.2O3
La0.54Sr0.4Co0.6Fe0.4O3
La0.54Sr0.4Co0.5Fe0.5O3
CF-1
CF-2
CF-3
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RESULTS AND DISCUSSION (Cathode) XRD Analysis
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RESULTS AND DISCUSSION (Cathode) Density Measurement
S. no.
Sample
1050 C
1100 C
1150 C
1. CF-3 5.5822 5.975 6.1766
2. CF-2 5.5272 5.858 6.1151
3. CF-1 5.4336 5.803 6.0401
Density (g/cm3) in the following sintering temperatures
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RESULTS AND DISCUSSION (Cathode) Surface Area
Sample name Surface area
(m2/g)
CF 1 14.579 CF 2 10.778 CF 3 2.434
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RESULTS AND DISCUSSION (Cathode) D.C. Conductivity
Sample Name
CF 1
CF 2
CF 3
Sintering Temperatu
re ( C)
400
500
600
700
800
1050 673 683 652 574 478 1100 536 550 535 489 413 1150 516 541 530 481 409 1050 535 543 526 477 398 1100 504 509 485 437 364 1050 330 330 321 295 251 1100 421 428 420 393 341 1150 507 526 518 484 411
Conductivity (S/cm) at temperature
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RESULTS AND DISCUSSION (Cathode) D.C. Conductivity
Activation energy = 0.1986 * slope
Sample Name Sintering Temperature
High Temperature Low Temperature Activation Energy (10-5
eV) Activation Energy (10-5
eV) CF-1A 1050C 8.3436 8.3301
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RESULTS AND DISCUSSION (Cathode) Current and Power Density
Electrochemical
property
800
750
700
Current density
(A/cm2)
2.11 1.33 0.729
Power
Density(W/cm2)
1.47 0.936 0.510
Temperature ( C)
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CONCLUSIONS
Challenges - Solutions -
i. Density of solid electrolyte. i. Relative Density as high as 93.93 % is
achieved. ii. Ionic mobility. ii. Increase in ionic conductivity signifies
increase in ionic mobility
iii. Surface area of cathode. iii. Surface area as high as 14.79 m2/g is
achieved. iv. Current and power density. iv. 2.11 A/cm2 and 1.47 W/cm2 v. Working temperature. v. Maximum ionic conductivity was
achieved at 500 C.
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REFERENCES
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Questions?
Thank You.
6-Mar-15 22 Rohit Gupta/IIT(BHU), Varanasi
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