System Concept and Process Layout for a MircoCHP Unit based on Low Temperature SOFC
Thomas Pfeifer1, Laura Nousch1, Wieland Beckert1, Dick Lieftink2, Stefano Modena3
(1) Fraunhofer IKTS, (2) Hygear Fuel Cell Systems, (3) SOFCPower
10th European SOFC Forum 2012
Lucerne, June 26 - 29, 2012
© Fraunhofer IKTS
What is LOTUS?
Low Temperature SOFC µ-CHP System
 Project of FCH JU (Fuel Cells and Hydrogen Joint Undertaking)
 3 year project: January 2011- December 2013
 Objectives:
 CHP system at reduced stack-temperature of 650°C based on ASC technology
 low cost, mass-produced and proven components
 high electrical efficiency (min. 45%) and high total system efficiency
 appropriate solutions for real-world operation
© Fraunhofer IKTS
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LOTUS Consortium
European Research, SME and Industry
© Fraunhofer IKTS
HyGear Fuel Cell Systems
(NL)
Coordinator, component
design and prototyping
SOFCPower (IT)
SOFC stack development
Fraunhofer IKTS (GER)
System modeling (steady
state, dynamic) and controls
Domel (SLO)
Gas-air system development
University of Perugia (IT)
User profile input, SOFC
single cell testing
EC Joint Research Center
(NL)
SOFC stack testing, testplan
harmonization
Associated partner:
Vaillant (GER)
System requirements
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LOTUS Design Studies
0-D Stack-Model Parameterization (sofc.dll)

U/I-Measurements at varying temperature and fuel-input provided by SOFCPower.

Model parameters identified by least squares fit of area specific cell resistance.
SOFCPow er S-Design Short-Stack Performance
SOFCPow er S-Design Short-Stack Performance
6,0
2,5
No. of cells: 5 á 50 cm²
Fuel: 100 % H2 (sat. @ 25 °C)
Fuel input: 1.5 slm ≈ 270 J/s
Air stoich. ratio: 4.2
650°C (Model)
5,0
700°C (Test)
700°C (Model)
4,5
750°C (Test)
4,0
750°C (Model)
800 °C (Test)
3,5
Cell Area Resistance RAcell / W cm2
Stack Voltage U / V
5,5
No. of cells: 5 á 50 cm²
Fuel: 100 % H2 (sat. @ 25 °C)
Fuel input: 1.5 slm ≈ 270 J/s
Air stoich. ratio: 4.2
650°C (Test)
2,0
65
65
70
1,5
70
75
1,0
75
80
0,5
80
800°C (Model)
0,0
3,0
0
100
200
300
400
500
600
0
700
200
300
400
500
Current Density jel / mA cm-2
Current Density jel / mA cm-2
© Fraunhofer IKTS
100
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600
700
LOTUS Design Studies
Stack Performance Estimation at 650 °C
SOFCPower ASC700+20%
enables LOTUS-development
 Available Cell Technology: ASC700
66 x 50 cm², CH4-SR Reformate
0.35
0.45 0.40
39.6 (0.60)
0.9
0.8
0.25
0.30
0.5
0.6
0.7
 Expected Development: ASC700+20%
66 x 80 cm², CH4-SR Reformate
25 A
el = 0.50
ASC700 +20% , S-Design (80 cm²), 66 Cells
Aact = 66 x 80 cm² / T Cell = 650°C
T
= 650°C / T = 550°C
0.4
Fuel
300 Nl/min
42.9 (0.65)
42.9 (0.65)
200 Nl/min
800 W
0.15
15 A
49.5 (0.75)
PDC = 400 W
56.1 (0.85)
I= 5 A
59.4 (0.90)
500
1000
© Fraunhofer IKTS
1500
600 W
VAir,ad =
FU = 0.2 100 Nl/min
ASC700, S-Design (50 cm²), 66 Cells
Aact = 66 x 50 cm² / T Cell = 650°C
TFuel = 650°C / T Air = 550°C
Stack Voltage | Average Cell Voltage [V]
Stack Voltage | Average Cell Voltage [V]
0.3
52.8 (0.80)
3000
2500
Fuel Input [J/s]
3500
4000
45 A
4500
0.7
0.6
500 Nl/min
46.2 (0.70)
35 A
0.55
30 A
1600 W
0.5 400 Nl/min
0.30
1400 W
300 Nl/min
49.5 (0.75)
0.60
1550 WDC @ 70% FU
UCell = 0.7 V
52.8 (0.80)
0.4 0.25
25 A
1200 W
200 Nl/min
20 A
0.3 0.20
1000 W
0.65
VAir,ad =
15 A
FU = 0.2
59.4 (0.90)
500
5000
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700 Nl/min
600 Nl/min
1800 W
0.35
40 A
56.1 (0.85)
Fuel: CH4-SR @ 650 °C, S/C = 1.5,  = 0
7.2% CH 4 / 60.6% H 2 / 14% H 2O
12.4% CO / 5.9% CO 2 / 0% N 2
0.40
50 A 0.8 800 Nl/min
2000 W
2
LHV = 238.98 kJ/mol
2000
el = 0.50
LHV = 238.98 kJ/mol
0.55
650 WDC @ 70% FU
UCell = 0.7
V
10 A
Air
Fuel: CH -SR @ 650 °C, S/C = 1.5,  = 0
4
7.2% CH 4 / 60.6% H 2 / 14% H 2O
12.4% CO / 5.9% CO / 0% N
2
20 A
46.2 (0.70)
0.45
0.9
39.6 (0.60)
0.20
1000 W
I = 10 A
400 W
1000
1500
2000
2500
3000
Fuel Input [J/s]
100 Nl/min
PDC =
800 W
600 W
3500
4000
4500
5000
LOTUS Stack Development
Recent Test-Results by SOFC Power
 short-stack performance improvement is
demonstrated under H2/N2 mixture
700°C
© Fraunhofer IKTS
650°C
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LOTUS Design Studies
Evaluation of Fuel Reforming Options
 Stack-Internal Reforming (IR)
Fuel
IR-SOFC
H2O
 Pre-Reforming
Steam Reforming (SR)
Fuel
H2O
SR
SOFC
POX
Heat
Autothermal
Reforming (ATR)
Fuel
H2O
800 °C
650 °C
ATR
ATR
ATR
SOFC
POX
SOFC
POX
Air
Partial Oxidation (POX)
Fuel
Air
SR
Heat
© Fraunhofer IKTS
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SR
LOTUS Design Studies
Boundary Conditions for the LOTUS System Design
 stack temperature predetermines reforming temperature  650 °C
 soot-free reformer operation requires S/C ~ 2 .. 3
 in practical µCHP-operation a lower system S/C is essential
 controlled stack-internal reforming (IR) is beneficial for system efficiency
 for start-up and shut-down of ASC a reducing atmosphere > 300 °C is required
 part load operation and independent control of power to heat ratio is beneficial
for system economics
LOTUS system design is governed
by the fuel reforming concept
and its process integration
© Fraunhofer IKTS
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LOTUS System Design
Process Flow Diagram (PFD)
Implementation of
the LOTUS Fuel
Reforming Concept
~
=
SB
Start-up
Burner
 fuel bypass (FBP)
for controlled stackinternal reforming
 downscaled steam
reformer (SR)
 SR directly heated
by burner exhaust
(AB or SB)
 optional use of
oxidative steam
reforming
© Fraunhofer IKTS
Electricity
FBP Fuel Bypass
SR
Steam
Reformer
Fuel
SOFC
Stack
AB
Afterburner
APH
Air Pre-Heater
Air
EVP
Evaporator
Water
CHP-Hx
Heat
Exchanger
Heat
Exhaust
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LOTUS Process Layout
System Performance Estimation
© Fraunhofer IKTS
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LOTUS Component Development
Steam Reformer Pre-Test
supports coated with reformer catalyst
© Fraunhofer IKTS
reformer test rig …
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LOTUS Component Development
Burner Pre-Test
control panel for testing of the dualuse burner prototype
© Fraunhofer IKTS
test-rig and model of
dual-use burner
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LOTUS Component Development
Blower Development
two stage high pressure blower
with EC motor- prototype
© Fraunhofer IKTS
CFD simulation of the two stage
high pressure blower
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Outlook
Next Steps in the LOTUS-Project
Description
Timeline
System component development: system BOM, component design
and specification (HyGear)
09/2012
Stack development: design freeze, pre-testing and delivery of full-scale
ASC stack (SOFCPower)
12/2012
Dynamic process model implemented in Modelica + software state
machine for control logic development (IKTS)
12/2012
Prototype setup and commissioning (HyGear)
06/1013
System testing (HyGear & IKTS)
12/2013
© Fraunhofer IKTS
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Thanks for your attention!
www.lotus-project.eu
© Fraunhofer IKTS
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