Solid Oxide Fuel Cell Technology Development in BARC B. P. Sharma - - PowerPoint PPT Presentation

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Solid Oxide Fuel Cell Technology Development in BARC B. P. Sharma - - PowerPoint PPT Presentation

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Solid Oxide Fuel Cell Technology Development in BARC B. P. Sharma Associate Director Materials Group (S) BARC Challanges in Fuel Cell Technology - 01-12-2006 India's Prosepectives 1 Solid Oxide Fuel Cell Technology Development in BARC

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 1

Solid Oxide Fuel Cell Technology Development in BARC

  • B. P. Sharma

Associate Director Materials Group (S) BARC

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 2

NASA Photograph

Solid Oxide Fuel Cell Technology Development in BARC

  • B. P. Sharma, A. K. Suri, S. K. Mitra, P. Ragunathan,
  • P. K. Sinha, John T. John, and A. Ghosh
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Future energy systems

Solar Hydrogen-based Nuclear etc.

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Outline of the Presentation

  • Hydrogen as future energy carrier
  • Production of hydrogen
  • Hydrogen storage
  • Direct conversion of hydrogen energy through

solid oxide fuel cell

  • Materials
  • Cell Design
  • Fabrication Techniques
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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 5

Complete Hydrogen Cycle

Hydrogen Storage and transportation for other utilities Energy

Solar

Nuclear

SOFC

Electrical Energy

Dissociation

  • f water

H2 H2O O2 O2

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 6

Hydrogen Fuel: Technological Challenges

  • Production and delivering hydrogen at low cost

Pyrolysis, Electrolysis, Photolysis

  • Storage system (Compact, light wt., safe, efficient, low cost)

Pressurized Gas, liquid, Solid Absorbents

  • Efficient conversion

Fuel Cells (Direct Conversion of Chemical Energy to electrical energy) Materials Design Safety

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Production of Hydrogen

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Hydrogen from Water

Prospective water based hydrogen production techniques are: 1) Electrochemical production (Water electrolysis) 2) Electrothermal water decomposition (Steam electrolysis) 3) Thermochemical water splitting (Thermo chemical cycles)

Hydrogen produced from water alone can serve the purposes of an ideal, sustainable and environment friendly clean energy economy

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 9

Hydrogen Production by Water Electrolysis

  • Alkaline Water Electrolyser: 10 Nm3/h capacity is developed by BARC: Technology is

available for production

  • Alkaline Water Electrolyser of 30 Nm3/h is being developed (Time frame: 2005-08)
  • BARC is also developing Solid Polymer Electrolyte (SPE) Water Electrolyser (Time

frame: (2005- 08)

  • BARC is also working on High Temperature Steam Electrolyser:

Experimental studies with single tube cell are planned during 2005 - 08 and with multi- tube cell are planned in 2008 –12

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 10

Compact electrolyser of filter press type A 40-cell electrolysis module (weighing 900 kg) incorporating Porous Nickel Electrode operates at a high current density of 4500 Am-2 which is much higher than conventional cells in the market (1500 Am-2 or below)

  • The electrolyser operates at 550 C and 0.16 MPa to

produce 10 Nm3/h of hydrogen HIGH CURRENT DENSITY COMPACT ELECTROLYSER

(10 m3 /h hydrogen capacity)

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 11

I-S Process Ca-Br Process Cu-Cl Process Efficiency (%) 57 40 41 Operating temperature 950° C 760° C 550° C Process Streams Liquid & gas Solid & gas Solid, liquid & gas Development stage Fully flow sheeted Fully flow sheeted R&D stage Demonstration Pre pilot plant Pilot plant Not demonstrated Capital Cost Low High NA Corrosion High High low

HYDROGEN FROM WATER Comparison Of Thermo Chemical Processes

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Hydrogen from Water: Thermochemical Process Iodine-Sulfur (IS) Process – Reaction Scheme

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Hydrogen Storage

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  • High-pressure storage:

heavy and bulky vessels

  • Liquefied hydrogen:

attractive weight and volume requires energy to liquefy the storage system has potential risks

  • Solid Absorbents

Hydrogen storage Absorption under ambient conditions

  • f Temp and Pressure

Desorption occurs at elevated Temp Metal hydrides Complex Hydrides Microporous materials

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Hydrogen is distributed compactly throughout the metal lattice. Metal hydrides, therefore, represent an exciting method of storing hydrogen. They are inherently safer then compressed gas or liquid hydrogen They have higher hydrogen storage capacity. In fact, certain hydrides can store more than twice the amount of hydrogen that can be stored in the same volume of liquid hydrogen. The key to practical use of metal hydrides is their ability to both absorb and release same quantity of hydrogen many times without deterioration.

Metal Hydrides

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Hydrogen Storage Capacity

Storage media Gaseous H2 Liquid H2 MgH2 Mg2NiH4 VH2 FeTiH2 LaNi5H6 Hydrogen storage By weight (%) 100 100 7.6 3.3 3.8 1.9 1.4 Energy density By weight (cal/g) 33,900 33,900 2373 1071 701 593 464 Energy Density By volume (cal/ml) 271 2373 3423 2745 3227 3254 3017 The standard set by US Department of Energy (DOE) requires A system-weight efficiency (the ratio of stored hydrogen weight to system weight) of 6.5-wt % of hydrogen and a volumetric density of 62 kg H2/m3

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Ti sponge absorbs hydrogen at room temperature below one atmospheric pressure forming TiH2 Ti-hydride desorbs hydrogen at around 534° C These properties of titanium sponge are ideally suitable for a getter material for handling and storage of hydrogen and its isotopes

200 400 600 800 1000 0.0 0.4 0.8 1.2

(a) (b)

572 572 551

Signal (Arb. Unit) Temperature (

0C)

Temperature programmed desorption (TPD) plots of (a) TiHx and (b) TiDx

Hydrogen Storage in TiH2

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Complex Aluminum Hydrides

Examples Capacity* (Wt%) Na(AlH4) 5.6 Li(AlH4) 7.9 Zr(AlH4)2 3.9 Mg(AlH4)2 7.0

* Reversible Theoretical Capacity

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Hydrogen Storage in Carbon Nano Structures Hydrogen storage in carbon nanostructures is a very attractive topic owing to the low density of carbon and its high potential storage capacities. Challenges:

  • 1. The mass production of carbon nanotubes at a reasonable

cost.

  • 2. Purification and surface functionalisation
  • f carbon

nanotubes.

  • 3. Understanding the adsorption/desorption mechanisms and

the volumetric capacity of carbon nanostructures.

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Direct Conversion of Hydrogen Energy Solid Oxide Fuel cell

Direct Conversion of Chemical Energy to Electrical Energy …Carnot Cycle is not the limitation

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Comparison of different Fuel Cells

PAFC MCFC SOFC PEMFC Electrolyte

Phosphoric Acid Molten Carbonate Salt Ceramic Polymer

Operating temperature

190°C 650°C 800-1000°C 80°C

Charge Carrier

H+ CO3

  • 2

O-2 H+

Fuels

Hydrogen (H2) Reformate H2/CO/ Reformate H2/CO2/CH4 Reformate H2 Reformate

Reforming

External External/ Internal External/ Internal External

Prime Cell component

Graphite-based Stainless steel Ceramic Carbon based

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Solid Oxide Fuel Cell (SOFC)

Fuel cell utilizes hydrocarbon/hydrogen as fuel which reacts electrochemically with oxygen

Load

O-2

e-

Cathode Anode Electrolyte

Power

Principle of SOFC Cathodic Reaction : ½ O2 + 2e- O2- Anodic Reaction : H2 +O2- H2O + 2e-

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 23

  • Highly efficient electric power generation system (can be

as high as 70-80%)

  • Effective utilization high temperature waste heat
  • Direct reforming of gaseous fuel in 1000° C operating

SOFC

  • Environmental friendly power generation
  • All ceramic component---- A Challenge in Materials and Manufacturing

Technology

Target: Low cost of SOFC system by achieving

  • High power density (0.5 W/cm2)
  • Improved durability
  • Low material and manufacturing cost

Salient Features of SOFC

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 24 Mixed conductor Porous ( 30 -40 %) Stability No chemical interaction Matching TCE Ionic Conductor Fully Dense Electronic Conductor 30-40% Porous Stability, Matching TCE No chemical interaction

Microstructural Requirements

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Ionic Conductivity of different Electrolyte

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Zirconia based Ceria based Lanthanum

  • xide based

Bismuth oxide based

Excellent Stability in

  • xidizing and

reducing environment Excellent Mechanical stability (3YSZ) Well studied material Good compatibility with cathode Materials Good compatibility with cathode Materials High Conductivity High Conductivity Lower Ionic Conductivity Electronic conduction at low pO2 Poor mechanical strength Ga evaporation at low pO2 Formation of stable secondary phases Incompatible with NiO Poor mechanical strength Thermodynamic instability in reducing atmosphere Volatilization of Bi2O3 High corrosion activity Poor mechanical strength

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 27 4 6 8 1 0 1 2 1 0

  • 4

1 0

  • 3

1 0

  • 2

1 0

  • 1

1 0

6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0

C o n d u c t i v i t y ( S . c m

  • 1 )

M o l % y t t r i a

In YSZ the maximum conductivity is for 8 mol% Yttria doping

Total conductivity of YSZ at different temperatures as a function of yttria content

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Fuel Cell Development at BARC

The Fuel Cell Development Program at BARC aims at

Technology Development and Demonstration for 5 kW tubular SOFC and 1 kW Planar Multi-cell PEMFC systems complete with fuel generator and power conditioner Setting up of facilities and infrastructure for fabrication/ integration of fuel cell components and other subsystems, specially thin ceramic films for SOFC and Membranes and MEA (Membrane Electrode Assembly) for PEMFC Modular Cell design for standardization and Scale up

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State-of-the-art SOFC Bench mark properties for component materials

1.

Cathode Composition : LSM (La0.9Sr0.1MnO3) Porosity : 40% (pore size 20-50 μm) Conductivity : 100 S/cm at 1000O C TEC : 10 – 12 ppm/O C Dimensions : ID-14mm, Wall -2mm, L-160mm

2.

Electrolyte Composition : YSZ [(ZrO2)0.92(Y2O3)0.08] Porosity : Nil, permeability should be zero Conductivity : Ionic ~ 0.1S/cm TEC : 10.5 ppm/O C Dimensions : Film thickness ~ 50 μm, L~125mm

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State-of-the-art SOFC Bench mark properties for compositions

3.

Anode Composition : Ni-YSZ cermet (Ni- 60% by wt) Porosity : 40% (pore size 20-50 μm) Conductivity : 1000-1500 S/cm TEC : 10 – 12 ppm/OC Dimensions : OD- 18.1 mm, t~ 100 μm, L~125 mm

4.

Interconnect Composition : LCM [La0.95Mg0.05(CrO3)] Porosity : Nil, permeability should be zero Conductivity : 5-10 S/cm at 1000O C TEC : 10-12 ppm/O C Dimensions : W- 5mm, L- 125mm, t~100 μm

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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 31

SOFC: Designs

  • 1. Tubular Design
  • Pioneered by Siemens- Westinghouse
  • 2. Planar Design
  • Conventional ‘electrolyte supported’ concept
  • Cathode supported design
  • Newer – Anode supported concept
  • 3. Monolithic design
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01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 32

SOFC Development

Components of Single SOFC Tube and its manufacturing techniques

Anode Screen printing/Dip Coating Electrolyte EVD / Spray coating / Gel Coating/ Dip Coating Cathode Tube Extrusion / CIP Interconnect Plasma Spray

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Cell Dimension and Design of Tubular SOFC at BARC

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Powder Preparation Solution synthesis route a promising approach

Citrate gel Oxalate precipitation Hydrothermal Synthesis Combustion Synthesis Spray drying

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Synthesis of 8YSZ by Hydrothermal Technique

ZrOCl2 Y(NO3)2 Mixed at stoichiometric ratio (0.1M) Coprecipitated in excess Ammonia Precipitate is made Chloride free Hydrothermal treatment at 150°C and ~100 PSI in 0.5 wt% Ammo. Polyacrylate for 24h Dried at 80°C then crushed Ball milled for < 1hr Added PEG

50 nm

Crystallite Size = 4 to 6 nm Surface Area = 166 m2/gm (BET Technique)

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20 30 40 50 60 70 80 300 600 900 1200 1500 1800 2100 Intensity in Arbitary Unit 2θ in Degree

8YSZ coppt dried at 80

0C

8YSZ as synthesized by combustion 8YSZ hydrothermal as synthesized dried at 80

0C

200 400 600 800 1000 1200 1400 1600

  • 21
  • 18
  • 15
  • 12
  • 9
  • 6
  • 3

3

Linear Shrinkage Rate of Shrinkage in YSZ Hydrothermal

Temperature in

0C

Percentage of Linear Change

  • 1.8x10
  • 3
  • 1.6x10
  • 3
  • 1.4x10
  • 3
  • 1.2x10
  • 3
  • 1.0x10
  • 3
  • 8.0x10
  • 4
  • 6.0x10
  • 4
  • 4.0x10
  • 4
  • 2.0x10
  • 4

0.0 2.0x10

  • 4

Properties of Hydrothermally produced 8YSZ

Crystallite size = 7.7 nm Crystallite size = 9.3 nm

~96%ρTh

Sintered at 1300°C

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Low temperature sintering of nano-crystalline La(Ca)CrO3 (LCR) interconnect prepared through controlled gel combustion processes EDTA-nitrate combustion synthesis of La0.70Ca0.30CrO3

100 nm 2 μm 0.75 1.00 1.25 1.50 1 2 3 4 ln σ (S cm

  • 1)

1000/T (K

  • 1)

Powder Sintered at 1250 °C Conductivity at 1000 °C: 51 Scm-1

TEC: 10.3×10-6 °C-1

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Glycine-nitrate combustion synthesis of LCR interconnect

1 10 20 40 60 80 100 Using CrO3 2 min ultrasonic 6 min ultrasonic Under Size (%) Particle Size (μm)

Sintered at 1200 °C (Fractured surface) Lowest sintering temperature ever reported Conductivity at 1000 °C: 58 Scm-1

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Chemical compatibility of LSM with YSZ

2 0 3 0 4 0 5 0 6 0 7 0

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0

  • 2 θ

1 4 0 0

  • C / 6 h r s

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0

  • Intensity (a.u.)

1 4 0 0

  • C / 3 h r s
  • A s m ix e d

L S M Y S Z

No reaction products even at 1400o C

  • Powder mixture compact
  • Phase analysis
  • X-ray maps

Temperature range 1000 – 1400o C

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Microstructural study of YSZ-LSM: Chemical Compatibility

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Sharp interface between YSZ and LSM Electron Microprobe Micro analysis of YSZ-LSM

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Shape Forming

Fabrication of support tube (tubular SOFC) Extrusion Cold Isostatic Press Fabrication of thin/thick films Tape casting Vacuum slip casting

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La2O3 La0.7Sr0.2MnO3 Slurry mixing Compaction Die filling and CIP at 145 MPa Green tube Sintering Graphite (19.5 μm) Finished tube

Green Tube Sintered Tube

LSM Cathode fabricated at ECMS through CIP

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Microstructure of Sintered Porous LSM tube

Graphite was added as the pore former Pore size 5-15 µm

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Sintered LSM tube (35% porous) Cathode for SOFC

Shape Fabrication Extrusion Technique

Porosity ~35 %

200 400 600 800 1000 40 50 60 70 80

σ (S/Cm)

Temperature (

  • C)

200 400 600 800 1000 0.0 0.2 0.4 0.6 0.8 1.0 2 4 6 8 10 12 14

% THERMAL EXPANSION TE M P E R A TU R E (

OC

)

10.87ppm /

OC

α (cm.cm-1.OC-1)

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Schematic diagram of the CVD system For coating of LSM tube by YSZ

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Gas stream I ZrCl4 + H2O → ZrO2 + 2HCl 2YCl3 +3H2O → Y2O3 + 6HCl at 1000- 13000C Gas stream II CO2 + H2 → H2O + CO

Electrochemical Reaction 2YCl3 + 3 O2- +3H2 → Y2O3 +6HCl +6 e- ZrCl4 +2O2- +2H2 → ZrO2 + 4HCl +4e- Fraction of Y2O3 in ZrO2 is decided by the composition of the vapor.

  • 1. Independent control on the temperature of ZrCl4 and YCl3 baths.

ZrCl4 between 150 - 1850C YCl3 between 550 - 6500C

  • 2. Independent gas steams

Optimization of pressure to get coating at the outer surface.

CVD process

R

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EVD Setup for depositing YSZ electrolyte film on porous LSM cathode tube

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Sintered ceramic tapes

3YSZ flexible ceramic tapes (Corning corporation, USA)

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Cross sectional view of NiO-YSZ coating on YSZ tube

NiO-YSZ Coating

YSZ

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Morphology of Ni Morphology of Ni – – YSZ coating YSZ coating

50 µm

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LCR Coating (Plasma Spray) on Porous LSM

LCR LSM LCR LSM

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Target : March 2007

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SOFC Single cell Self supporting YSZ electrolyte 20mm dia 700 µm thick cathode and anode are applied by brush coating Pt grid was used on the electrode contacts Open Circuit Voltage 0.8 V was obtained at 1000 °C.

Electrical Characterization Facility for Electrical Characterization Facility for SOFC SOFC

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Summary BARC Activity on Fuel Cell Programme

BARC has taken up development of “Compact High Temperature Reactor” The heat generated in the reactor may be tapped and converted to electricity and hydrogen Solid Oxide Fuel Cell will play a pivotal role in conversion of this hydrogen energy to electrical energy

Thank You

bpsharma@barc.gov.in

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Hydrogen : The Future Fuel

  • Clean energy

No air-pollution Minimum green house gas emission

  • High energy density
  • Compatible with efficient fuel cells
  • Long term energy security/ diverse resources
  • Can serve all sectors of economy

….the first car driven by a child born today could be powered by hydrogen and pollution free. US President, Jan. 28, 2003

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Overall cell reaction is simply the oxidation of fuel. Open circuit voltage “E” is expressed as:

⎪ ⎭ ⎪ ⎬ ⎫ ⎪ ⎩ ⎪ ⎨ ⎧ = (fuel) P (oxidant) P ln 4F RT E

2 2

O O

When a current is drawn from the cell, cell voltage V is:

F A

IR E V η η − − − =

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  • Electrolyte
  • Cathode
  • Anode
  • Interconnect (for a stack)
  • Seals

Fuel Cell components

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  • Ionically conductive - oxygen ion transport no. ~ 1
  • Chemically stable (at high temperatures as well as in

reducing and oxidizing environments

  • Gas tight/free of porosity
  • Uniformly thin layer (to minimize ohmic losses)
  • Thermal expansion that match

Requirements for the electrolyte

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Zirconia electrolytes (8YSZ,3YSZ,ScSZ,CaSZ etc.) Ceria electrolytes (GDC, SDC, YDC, CDC etc.) Lanthanum based electrolytes LSGM LaxSr(1−x)GayMg(1−y)O3 LaAlO3-based La1−xCaxAlO3, La1−xBaxAlO3 Bismuth oxide-based Bi2V0.9Cu0.1O5.5-δ, (Bi2O3)x(Nb2O5)1−x Pyrochlorores-based YZr2O7, Gd2Ti2O7 Barium brownmillerites BaZrO3, Ba2In2O5, Ba3InxAOy (A = Ti, Zr, Ce, Hf), Ba3Sc2ZrO8

Different Electrolytes

Composite Electrolyte: Doped ceria + Molten Salt ???

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  • High electronic conductivity
  • Chemically compatible with neighboring cell component

(usually the electrolyte)

  • Should be porous
  • Stable in an oxidizing environment
  • Large triple phase boundary
  • Catalyze the dissociation of oxygen
  • Adhesion to electrolyte surface
  • Thermal expansion coefficient similar to other SOFC materials

Requirements for the cathode

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Lanthanum cathodes LSM LaxSr(1−x)MnO3 LSF LaxSr(1−x)FeO3 Gadolinium cathodes GSC GdxSr(1−x)CoO3 Yittria cathodes YSCF Y(1−x)SrxCoyFe(1−y)O3 Strontium cathodes SSC SmxSr(1−x)CoO3

Different Cathode Materials

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  • Electrically conductive
  • High electro-catalytic activity
  • Large triple phase boundary
  • Stable in a reducing environment
  • Can be made thin enough to avoid mass transfer losses, but thick

enough to provide area and distribute current

  • Thermal expansion coefficient similar neighboring cell component
  • Chemically compatible with neighboring cell component
  • Fine particle size
  • Able to provide direct internal reforming (if applicable)
  • Tolerant to sulfur in fuels (if applicable)

Requirements for the anode

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  • Stable under high temperature oxidizing and reducing environments
  • Very high electrical conductivity
  • High density with “no open porosity”
  • Strong and high creep resistances for planar configurations
  • Good thermal conductivity
  • Phase stability under temperature range
  • Resistant to sulfur poisoning, oxidation and carburization
  • Low materials and fabrication cost
  • Matching thermal expansion to other cell components

Requirements for the interconnect

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Interconnect

Ceramic Interconnect for High temperature SOFC (High material cost, sintering difficulties) e.g Doped Lanthanum Chormites and doped Yttrium chromites Metallic Interconnects (easy fabrication, high electrical and thermal conductivity) High chrome alloys (Cr5Fe1Y2O3) Ferritic stainless steel for low temperature SOFC Iron super alloys Nickel super alloys Critical Issues Chromium evaporation (in Cr based interconnects)

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Requirements for the sealing materials

  • Electrically insulating
  • Thermal expansion compatibility with other cell components
  • Chemically and physically stable at high temperatures
  • Gastight
  • Chemically compatible with other components
  • Provide high mechanical bonding strength
  • Low cost

Materials Glass ceramic materials – SrO-La2O3-Al2O3-SiO2 Mostly are under Intellectual Property Rights

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Cell Design

Different Concepts Driven by Cell efficiency Fabrication Technology of the component Cost of the Material Sealing Material Technology

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Materials Processing :

Powder Preparation Stable Slurry Shape Forming Thin coating Sintering

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Tape Casting

Tape casting is a method for producing thin, ceramic tapes by doctor-blade process For tape-casting, first ‘Slip’

  • f ceramic powders is
  • prepared. The slip is generally a fluid based on organic

solvents A typical slip composition contains:

Powder Dispersant (Acetic acid, Oleic acid etc.) Solvent (Ethanol, MEK, TCE etc.) Plastisizer (PEG, phthalates etc.) Binder (PVB, PVA etc.)

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Tape-casting Facility at ECMS, Vashi Complex, BARC Green Ceramic tapes

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SLIDE 71

01-12-2006 Challanges in Fuel Cell Technology - India's Prosepectives 71

Thin/thick Coating

Slurry Coating Dip coating Electrophoretic deposition Screen printing Spray Coating Vapour deposition Chemical vapour Deposition Electrochemical vapor Deposition Reactive Magnetron Sputtering RF sputtering Plasma Spraying