Date post: | 20-Jan-2015 |
Category: |
Technology |
Upload: | 4th-international-conference-on-advances-in-energy-research-icaer-2013 |
View: | 78 times |
Download: | 5 times |
Copy
right
201
3-20
14
1
Barium Doped Bismuth Vanadate Structural and Thermal Properties for SOFC
Application
Sakshi Gupta and K. Singh*
School of Physics & Materials Science, Thapar University, Patiala
*E-mail: [email protected]
Paper Code: 099
IV th International Conference on Advances in Energy Research
Indian Institute of Technology Bombay, Mumbai
Copy
right
201
3-20
14
2
Introduction
Deficiency of conventional energy sources.
Release of green house gases with combustion of conventional energy sources.
Need to develop an energy efficient non conventional eco- friendly source.
Copy
right
201
3-20
14
3
Fuel Cell
Fuel cell is an electrochemical energy conversion device.
It produces electricity from external supplies of fuel (anode
side) and oxidant (cathode side).
In fuel cell and battery, electrochemical reactions are used to
create electric current.
Fuel cells are different from batteries as they consume reactant,
which can be replenished, while batteries store electrical energy
chemically in a closed system.
Copy
right
201
3-20
14
Types of Fuel Cells
4
Copy
right
201
3-20
14
Alkali Fuel Cell (AFC)
Compressed hydrogen and oxygen fuel
potassium hydroxide (KOH) electrolyte
~70% efficiency
150˚C - 200˚C operating temp.
300W to 5kW output
Requires pure hydrogen fuel and platinum catalyst Liquid filled container → corrosive leaks
5
Copy
right
201
3-20
14
Molten Carbonate Fuel Cell (MCFC)
Carbonate salt electrolyte
60 – 80% efficiency
~650˚C operating temp.
cheap nickel electrode catalyst
up to 2 MW constructed, up to 100 MW designs exist
Corrosive electrolyte
6
Copy
right
201
3-20
14
Phosphoric Acid Fuel Cell(PAFC)
Phosphoric acid electrolyte
37-42% efficiency
150˚C - 200˚C operating temp
11 MW units have been tested
The electrolyte is very corrosive
Platinum catalyst is very expensive
7
Copy
right
201
3-20
14
Polymer electrolyte Membrane(PEM)
Thin permeable polymer sheet electrolyte
40 – 50% efficiency
50 – 250 kW
80˚C operating temperature
Electrolyte will not leak or crack
Temperature good for home or vehicle use
Platinum catalyst on both sides of membrane
8
Copy
right
201
3-20
14
Solid Oxide Fuel Cell (SOFC)
Hard ceramic oxide electrolyte
~80% efficient
~1000˚C operating temperature
cells output up to 100 kW
High temp / catalyst can extract the hydrogen from the fuel at the electrode
High temp allows for power generation using the heat, but limits use
SOFC units are very large
Solid electrolyte have no leakage problem
9
Copy
right
201
3-20
14
10
Continued.....
Out of the fuel cells discussed above Solid Oxide
Fuel Cells (SOFCs) can be considered as a possible
solution. SOFCs provide high total efficiency in
addition to clean energy production. As well as water
is the only emission along with energy along with
energy when hydrogen is used as fuel in SOFCs
Copy
right
201
3-20
14
11
The benefits of SOFCs Include:
Energy security: reduce oil consumption, cut oil imports, and increase the amount of the country’s available electricity supply.
Reliability: achieve operating times in excess of 90% and power available 99.99% of the time.
Low operating and maintenance cost: the efficiency of the SOFC system will drastically reduce the energy bill (mass production) and have lower maintenance costs than their alternatives.
Constant power production: generate power continuously.
Choice of fuel: allow fuel selection: hydrogen may be extracted from natural gas, propane, butane, methanol or diesel fuel.
Copy
right
201
3-20
14
12
desirable characteristics of SOFC components:
Good stability. High conductivity. Chemical compatibility with other components of the cell. Similar thermal expansion coefficient to avoid cracking during the cell operation. Dense electrolyte to prevent gas mixing. Porous anode and cathode to allow gas transport to the reaction sites. High strength and toughness Compatibility at higher temperatures. Low cost.
Copy
right
201
3-20
14
13
Characteristics of Solid Electrolyte
Availability of large number of free ions
Large number of vacancies for hopping
Free of porosity
Thermal expansion match
Chemically stable (at high temperatures as well as in
reducing and oxidizing environments)
The ionic conductivity of the electrolyte should be high
Copy
right
201
3-20
14
14
METHODOLOGY
Bi2O3 + V2O5 + BaO
Grinding of required composition in agate mortar pestle
Splat quenching of the melted sample
Melting at 1250 �C
Characterizations
XRD Dilatometery SEM
Copy
right
201
3-20
14
15
X-RAY DIFFRACTION ANALYSIS
Reitveld refined XRD patterns of Bi4V2-xBaxO11-δ (a) as quenched x = 0.0, (b) as quenched x = 0.05, (c) sintered x= 0 and (d) sintered x = 0.05.
20 30 40 50 60 70 80
(b)
degrees (2)
Inte
nsity
(arb
. uni
ts)
(a)
20 30 40 50 60 70 80
(d)
Inte
nsity
(arb
. uni
ts)
degrees (2)
(c)
Copy
right
201
3-20
14
16
Reitveld refined lattice parameters of Bi4V2-xBaxO11-δ
(x = 0.0 and 0.05)
Composition
As quenched samples Sintered samples
a (Å) b (Å) c (Å) β (degrees) a (Å) b (Å) c (Å) β (degrees)
Bi4V2O11-δ
5.58
15.35 16.59 89.98 5.59 15.33 16.59 89.97
Bi4V1.95Ba0.05O11-δ
5.57 15.39 16.65 90.08 5.59 15.35 16.61 89.95
Copy
right
201
3-20
14
17
MICROSTRUCTURE ANALYSIS
0.0 0.055
10
15
20
25
30
35
Range (m
)
x
Grain size range of sintered samples with x = 0.0 and 0.05.
Copy
right
201
3-20
14
18
SEM Micrographs
(a) (b)
(c) (d)
Scanning electron micrographs of Bi4V2-xBaxO11-δ (a) as quenched x = 0.0, (b) as quenched x = 0.05, (c) sintered x= 0.0 and (d) sintered x = 0.05.
20 μm 20 μm
10 μm10 μm
Copy
right
201
3-20
14
19
DILATOMETRIC ANALYSIS
Thermal expansion curves Bi4V2-xBaxO11-δ (a) as quenched x = 0.0, (b) as
quenched x = 0.05, (c) sintered x= 0.0 and (d) sintered x = 0.05.
0 100 200 300 400 500 600 700
0.0
1.0x10-3
2.0x10-3
3.0x10-3
4.0x10-3
5.0x10-3
6.0x10-3
Temperature(C)
L/Lo
-2.0x10-6
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
1.0x10-5
(C
TE /C
)
(b)
0 100 200 300 400 500 600 700 800-1.0x10-3
0.0
1.0x10-3
2.0x10-3
3.0x10-3
4.0x10-3
5.0x10-3
6.0x10-3
7.0x10-3
Temperature (C)
L/Lo
(a)
-4.0x10-6
-2.0x10-6
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
1.0x10-5
(CTE / C
)
0 100 200 300 400 500 600 700 800
0.0
1.0x10-3
2.0x10-3
3.0x10-3
4.0x10-3
5.0x10-3
6.0x10-3
Temperature (C)
L/Lo
-2.0x10-6
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
1.0x10-5
(C
TE /C
)
(c)
0 100 200 300 400 500 600 700 800
0.0
1.0x10-3
2.0x10-3
3.0x10-3
4.0x10-3
5.0x10-3
6.0x10-3
(d)
Temperature (C)
L/Lo
-2.0x10-6
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
1.0x10-5
Copy
right
201
3-20
14
20
Thermal expansion coefficients and different transitiontemperatures of Bi4V2-xBaxO11-δ (x = 0.0 and 0.05)
Composition
As quenched samplesTEC (10-6 /⁰C)
Sintered samplesTEC (10-6
/⁰C)
Remarks
As quenched samples Sintered samples
Bi4V2O11-δ 8.83 8.98 α→β and β→γtransitions take place at 405 ⁰C and within the range 447-595 ⁰C respectively.
β→γ transition take place at533 ⁰C
Bi4V1.95Ba0.05O11-δ 9.21 8.62 α→β and β→γtransitions take place within the range at 301-398 ⁰C and 414- 509 ⁰C resp.
α→β and β→γ transitions takeplace within the range at330-392 ⁰C and 477- 595 ⁰C resp.
Copy
right
201
3-20
14
21
Conclusions
• All the samples synthesized are found to be single phase.
• All the samples are found to be stabilized in α phase with
C2/m space group which is confirmed with Reitveld
refinement.
• The grain size of the samples is decreasing with doping.
• The thermal expansion coefficient found to be in the range of
the components which are used in SOFC.
Copy
right
201
3-20
14
22
Acknowledgement
• I would like thank Department of Science and Technology
(DST) for the financial support.
• I would like to thank my Supervisor Dr. Kulvir Singh
(Professor and Head) School of Physics and Materials Science,
Thapar University, Patiala for his Guidance.
• I would like to thank Dr. P.C. Ghosh (Organizer ICAER 2013)
for providing me an opportunity to present my work here.
Copy
right
201
3-20
14