Energy Efficient Ceramic Electrolyte fuel cell system with enhanced

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

6-Mar-15 1 Rohit Gupta/IIT(BHU), Varanasi

INTRODUCTION AND WORKING

WHY SOFC ?


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

APPLICATIONS OF SOFC


Solid oxide Fuel Cell

WHY SOFC ? (Contd.)


CHALLENGES


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

SYNTHESIS PROCESS OF ELECTROLYTE


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

RESULTS AND DISCUSSION (Electrolyte) XRD Analysis


RESULTS AND DISCUSSION (Electrolyte) Density Measurement


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


RESULTS AND DISCUSSION (Electrolyte) SEM Micrographs

Sintered at 1350 C

Sintered at 1550 C

Sintered at 1400 C

Sintered at 1600 C


RESULTS AND DISCUSSION (Electrolyte) Impedance Analysis


RESULTS AND DISCUSSION (Electrolyte) Ionic Conductivity and Power Density


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


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


RESULTS AND DISCUSSION (Cathode) XRD Analysis


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


RESULTS AND DISCUSSION (Cathode) Surface Area

Sample name Surface area

(m2/g)

CF 1 14.579 CF 2 10.778 CF 3 2.434


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


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


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)


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

Questions?

Thank You.


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Energy Efficient Ceramic Electrolyte fuel cell system with enhanced