An Introduction to Solid Oxide Fuel Cell Research at CUED by pptfiles

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									An Introduction to Solid Oxide Fuel Cell Research at CUED
By Ben Haberman

1

Introduction
• • • • • The fuel cell The Rolls-Royce design Results Conclusions Any Questions?

2

The Fuel Cell
1 H 2  O 2  H 2O  2
Fuel flow Porous Electr- Porous Anode olyte Cathode
Air flow

H2O H2 2H+
2e-

O2-

O

2-

O
2e-

O2

Load

3

Reversible Operation
In open circuit conditions:
H2
o Wm ax   H T  Qrev

T , p 
H2

 



T , p 
O2

O2

T , p 

T , p 
H 2O

H2O

 p p 0 .5  H 2 O2  o   GT  RT ln   p p o 0.5   H 2O 



Q rev

Wm ax

0.5 o GT RT  X H 2 X O2  1 RT  p   E  EN   ln  ln    X H O  2 2 F  po  2F 2F    2 

4

Realistic Operation
When drawing a fixed current, i (Am-2):
E  E N  Losses
• Activation Loss

• Concentration Loss • Ohmic Loss
o  H T  P  Ei, Q    2 F  E i   

c

 P  Area 
o  mGT

cells

5

The Rolls Royce Design
Fuel cells
Air flow Ceramic module

Fuel flow

6

The Fuel Cell Components
100% H2O
Exhaust Recycled fuel Methane

5 Fuel cell bundles Air flow
810°C 700 Nl/min

1 Reformer bundle

950°C

CH4  H2O  3H2  CO 

G  0

Fuel flow 865°C 7Nl/min 2, 100% H2 50 Nl/min of 45% Hof 21%H2O, 10%CO2, 24% CO

CO  H2O  H2  CO2 G  0 
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A Hybrid System – Replacing Combustion Chamber
Load
Fuel inlet Fuel cells

Combustor Remaining fuel and air
Exhaust

Pressure vessel
Air inlet

Generator

Compressor

Turbine

8

What Do We Want to Know?
• Electrical power and heat generation
– Gas conditions at surfaces of electrolyte

• Fuel utilisation

3D simulations:
• Low Mach number gas channel flows • Porous flows • Physical phenomena – Transport of multi-component gas mixture – Convection, conduction & radiation – Chemical reaction • Electrochemistry
9

Code Development
• Original code
– 3D Compressible flow solver by Prof. Denton – Explicit time-marching method for Transonic flows

• New gas channel code
– Include all relevant physical phenomena – Very stiff equations - simplified preconditioning method

• Porous code
– Time marching as before – New model: Cylindrical Pore Interpolation Model (CPIM)
10

Results – Model Description
• Cannot model complete bundle

• Can look at infinite array • Only need 2 modules
• Appropriate periodic bc’s

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Boundary Conditions
• Air Inlet
– – – – Temperature = 865°C Pressure = 7 bar Composition = 21%O2, 79%N2 Flow rate = 70 Nl/min per air channel

• Fuel Inlet
– Variable Temperature 865-900°C – Composition = 45%H2, 21%H2O, 10%CO2, 24%CO – Flow rate = 1 Nl/min per fuel channel

• Fuel cells
– Fixed current density = 3000Am-2
12

Model Control Volume
Fuel cells Fuel outlet

Fuel inlet Surrounding repeating unit

•Over 3 million grid cells •Simulation required 3 months computer time
13

Hydrogen
z / mm

XH2
Fuel outlet

20

16

12 Fuel cells 8

4

0 0 20 40 60 80 100 120 140

Fuel inlet x / mm

14

Carbon Monoxide
z / mm

XCO

20

16

12

8

4

0 0 20 40 60 80 100 120 140

x / mm

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Temperature
z / mm 20 Temperature (°C) 893 891

889 16
887

885
883 881

12

879
877 8 875

4

0 0 20 40 60 16 80 100 120 140
x / mm

Summary of Results
• Fuel consumption
– 12% of H2 and 7% of CO used – Without shift reaction: 14.5% of H2 used – Shift reaction produces:
• 12% of H2 near fuel inlet • 20% of H2 near fuel outlet

• Net temperature rise
– 40°C along air channels – ~0°C along fuel channels

17

Operating Voltage
y / mm
6 Voltage (V)

4

2

0 x / mm

0

30

60

90

120

150

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Conclusions
• Each module produces 12.5 W of power • Component efficiency = 59% • Rolls-Royce design is very good
– High gas flow rates – Bundle geometry

• Further simulations required
– Whole bundle – Experimental validation
19

Thank You for Listening

Any Questions ?

20


								
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