sofc technology development, in connection to ffi project improved life time for sofc ... · 2015....
TRANSCRIPT
SOFC technology development, in
connection to FFI project Improved life
time for SOFC-APU
Jan-Erik Svensson, Hannes Falk
Windisch and Jan Froitzheim
Chalmers University of Technology
Improving Lifetime Performance of
SOFC for Truck APUs (Förbättringar av livslängden av fastoxidbränsleceller-APU
för tunga fordons applikationer)
Jan-Erik Svensson, Jan Froitzheim and Hannes Falk Windisch
Energy and Materials
Chemistry and Chemical Engineering
Chalmers University of Technology
Why trucks are idling?
• Electricity is needed during breaks for
– Cooling
– Heating
– Fridge
– Lighting
– Radio, PC, TV
– Etc.
Rolling homes that need electricity
Advantages with SOFC-APU
SOFC-APU can operate on diesel
• No extra tank required
• No new infrastruktur required
• An SOFC-APU is quiet…
• More effecitve than diesel engine (Efficiency 35%)
There are several types of fuel cells, the most common are:
•PEM (Polymer Electrolyte Membrane Fuel cells)
Operate at 80 C, high efficiency, fast start up, high sensitivity for fuel impurities
•SOFC (Solid oxide fuel cells)
Operate at 600-900 C, high efficiency, fuel flexibility, high-temperature corrosion
Projectpartners
Objectives
This project tries to mitigate three main causes of stack degradation in
relation to the interconnects,
– cathode side oxidation
– chromium evaporation and
– anode side oxidation, that diminishes power output and can lead to
stack failure
The idea behind the proposal is to resolve these issues in a cost-effective way,
using standard ferritic FeCr strip steel protected by multi-layered nano coatings
Improving Lifetime and Performance of SOFC for Truck APUs
- In a cost efficient way
Metallic Interconnect is the key! (Up to 40% of the cost of a stack!
Outline
Part I: Overview SOFC Technology
Part II: Recent results from the FFI project
Solid Oxide Fuel Cell (SOFC)
CathodeAnode Electrolyte
O2
O2-
The electrolyte is a oxygen ion conducting material (600-900 ºC)
H2 (fuel)
H2O (product)
Advantages
• High electrical efficiency
• O2- conductive electrolyte Fuel flexibility (H2, natural gas,
biogas.. diesel)
• High operating temperature No need for expensive catalysts
such as Pt
Solid Oxide Fuel Cell (SOFC)
Electrolyte supported Anode supported
>800C 650-800C
Metal supported
<700C
Solid Oxide Fuel Cell (SOFC)
Electrolyte supported
>800C
Mainly military applications (APU)
military ground vehicle APU
unmanned under water vehicle unmanned aerial systems
power systems for lunar
and Martian landers.
Hexis (Viessmann)
Elektrolyte supported design
1 kWel
1.8 kWheat
46.5% is achieved — with an overall energy
efficiency of 90.0%
Bloom Energy
• Bloom: ~100 MW installed
• Sunfire bought Staxera
• Located in Dresden/Germany
• Focus on both SOFC and SOEC
• rSOC Reversible SOC
SOEC Power to liquid process:
Process efficiency 70%
SOEC efficiency >90%
Cost (500t/day) ~1€/liter
Solid Oxide Fuel Cell (SOFC)
Anode supported
650-800C
Solid Power
(SOFCpower and Ceramic Fuel Cells)
60% electric =Record!
(74% DC single pass)
Courtesy of Elcogen
Courtesy of Elcogen
Versa Power/ Fuel Cell Energy
33 x 33cm cellsIncorporated the larger-scale SOFC
components into fuel cell stacks as large
as 60 kilowatts (kW).
Metal supported
<700C
Ceres Power
Source:http://www.cerespower.com/ProductOverview/ResidentialCHP/)
Ceres Power:
• Low temperature (<600C),
low cost approach
• 97% of the stack is steel –
3% ceramics
The steel cell
Metal supported FC
50% electrical efficiency (goal is 55%)
Natural Gas, steam reforming
< 600 ˚C => low cost materials
Start up time < 30 min
Outline
Part I: Overview SOFC Technology
Part II: Recent results from the FFI project
Cost analysis 1kW Stack
1kW Stack Manufacturing Cost (50 000Units)
Cells Interconnects
Sealing, End plate etc Assembly Hardware
Source: Battelle study prepared for US DOE (2014)
35%
• Similar thermal expansion as the ceramics used in SOFC
• Good electrical and thermal conductivity
• Form conductive oxide scales (Cr2O3)
• Formability
• Cheap to produce
Ferritic Cr2O3-forming steels as interconnect
material in SOFC
However
Steel (FeCr) Steel (FeCr)
Cr2O3
CrO2(OH)2(g)
oxidation
O2 + H2O
600-900 °C
Oxide scale growth → increased electrical resistance
→ Cathode poisoning
Cr vaporization: Cr2O3(s) + O2(g) + H2O(g) → CrO2(OH)2(g)
How to reduce Cr vaporization?
Steel
Co
Our approach apply metallic nano coatings:
Steel
(Co,Mn)3O4
Cr2O3
CrO2(OH)2(g)
oxidation
O2 + H2O
600-900 °C
0.E+00
1.E-04
2.E-04
3.E-04
4.E-04
5.E-04
6.E-04
7.E-04
8.E-04
9.E-04
1.E-03
0 100 200 300 400
Ac
cu
mu
late
dC
rva
po
riza
tio
n(k
g/m
2)
Exposure time (h)
x10 reduction
Cr vaporizationAir, 850 ºC
Co coated (600nm)
Uncoated Steel
Cr2O3
(Cr,Mn)3O4
Steel
(Co,Mn)3O4
Cr2O3
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
The pre-coated concept
InterconnectCell
The interconnect material has to be shaped in a way to allow for gas
distribution
Before exposure
Post-coated
Pre-coated
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
0.E+00
1.E-04
2.E-04
3.E-04
4.E-04
5.E-04
6.E-04
7.E-04
8.E-04
9.E-04
1.E-03
0 100 200 300 400
Ac
cu
mu
late
d C
r-va
po
riza
tio
n (
kg
/m2)
Exposure time (h)
Uncoated and undeformed
Undeformed (600nm Co)
x10 reduction
Cr vaporizationAir, 850 ºC
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
0.E+00
1.E-04
2.E-04
3.E-04
4.E-04
5.E-04
6.E-04
7.E-04
8.E-04
9.E-04
1.E-03
0 100 200 300 400
Ac
cu
mu
late
d C
r-va
po
riza
tio
n (
kg
/m2)
Exposure time (h)
Deformed + post-coated (600nm Co)
Uncoated and undeformed
Undeformed (600nm Co)
Cr vaporizationAir, 850 ºC
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
0.E+00
1.E-04
2.E-04
3.E-04
4.E-04
5.E-04
6.E-04
7.E-04
8.E-04
9.E-04
1.E-03
0 100 200 300 400
Ac
cu
mu
late
d C
r-va
po
riza
tio
n (
kg
/m2)
Exposure time (h)
Deformed + Post-coated (600nm Co)
Uncoated and undeformed
Undeformed (600nm Co)
Pre-coated + Deformed (600nm Co)
No signs of increased Cr-vaporization after mechanical deformation/stamping
Cr vaporizationAir, 850 ºC
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
60 µm
├───┤
60 µm
├───┤
60 µm
├───┤
60 µm
├───┤
Cr
Unexposed:
6 minutes:
8 hours:
24 hours:
Mn Co
Mn enrichment within the cracked area
More homogenues Cr, Mn and Co signal after 24 h
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
24 h (Air, 850 ºC):
Thin Co-rich layer within the cracked area
Growth of (Co,Mn)3O4 crystals within cracked area
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
Surface homogenously covered by an oxide rich in Co and Mn
336 h (Air, 850 ºC):
Reference: H. Falk-Windisch et al. / Journal of Power Sources 297 (2015) 217-223
Solid Oxide Fuel Cell (SOFC)
Electrolyte supported Anode supported
>800C 650-800C
Metal supported
<700C
Operating temperature for SOFC systems lies in between 600-900C
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0 100 200 300 400 500 600
Ne
t m
ass
ga
in(m
g c
m-2
)
Exposure time (h)
850 ºC
650 ºC
750 ºC
Negative mass gains after 500 h at lower temperatures
The effect of temperature on mass gain
Reference: H. Falk-Windisch et al. / Journal of Power Sources 287 (2015) 25-35
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0 100 200 300 400 500 600
Accu
mu
late
d C
r-va
po
riza
tio
n (
mg
cm
-2)
Expsure time (h)
850 ºC
650 ºC
750 ºC
Small effect of temperatur for Cr vaporization
The effect of temperature on Cr vaporization
=> Coatings are necessary also at lower temperatures (650 ºC)
Reference: H. Falk-Windisch et al. / Journal of Power Sources 287 (2015) 25-35
How is the metallic Co coating influenced by a lower temperatue?
Steel
Co
Steel
(Co,Mn)3O4
Cr2O3Diffusion of
Mn,Cr and Fe
650-750 °C
Steel
(Co,Cr,Mn,Fe)3O4
Cr2O3
?If not, what is formed instead?
And what is the effect on Cr vaporization
and oxide scale growth?
Do we need to design low-temperature
coatings?
Summary and future work
• Novel nano coatings for superior properties (Cr vaporization and oxidation
rate)
• Pre-coated concept to reduce costs
• Crack formation due to mechanical deformation (stamping)
• Self-healing of the (Co,Mn)3O4 toplayer
• Coatings necessary even at low temperatures
Cr vaporization is less influenced by temperature than oxide scale
growth
• A need for special designed low-temperature coatings?
Microstructure and chemical composition of the coating not the same
at lower temperatures
Stack tests (Elcogen) with novel nano coatings are scheduled to be carried
out beginning of 2016