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© National Fuel Cell Research Center, 2011 1/66
Fuel Cell & Hybrid Fuel Cell Gas Turbine
System Design, Dynamics & Control
Jack Brouwer, Ph.D.
Associate Director
April 18, 2011
© National Fuel Cell Research Center, 2011 2/66
Outline
• Introduction
• System Design and Steady State Performance
• Dynamic Performance & Understanding
• Control Systems Development
• Summary
© National Fuel Cell Research Center, 2011 3/66
Introduction
• Energy Systems are critical to:
• Economies – all sectors
• Quality of Life
• Freedom of Mobility
• A few important aspects of Energy Systems
• Thermodynamics
• Heat Transfer
• Fluid Dynamics
• Chemistry
• Dynamics
• Controls
• Systems Integration
• Environmental Impacts
• Consider All
• Make simplifying assumptions
• Rigorously analyze the
important physics/chemistry/etc.
in an integrated fashion
© National Fuel Cell Research Center, 2011 4/66
Fuel
Introduction: Fuel Cell System
Fuel Cell Power Plant or Engine
• Fuel cell stack
• Fuel processing – Reformer and gas clean-up
• Electric power conversion – inverter and power conditioner
• Balance of plant – heat exchangers, controls, valves, fans, …
Fuel
Processor
H2-rich
gasFC Stack
and Power
Block
DC
PowerPower
Control &
Conversion
AC
Power
Useful Heat
Water
Clean
Exhaust
© National Fuel Cell Research Center, 2011 5/66
Introduction: Fuel Cell System
Major System Components
Fuel processing• Source for the hydrogen
– Water - need energy for hydrolysis
– Hydrocarbons - consume some of the fuel energy
• Technology for conversion– Emissions?
– Reliability
– Efficiency
– Cost
Power conversion and electronics• Direct current (DC) to alternating current (AC)
– Needed for today’s end-use technologies
• Technology– Efficiency
– Reliability
– Cost
© National Fuel Cell Research Center, 2011 6/66
Introduction: Fuel Cell System
Major System Components (cont’d)
Controls
• Reliability
• Safety
– Hydrogen
• Integration
Balance of plant
• Valves
• Regulators
• Seals
• Plumbing
• Sensors/displays
• Heat exchangers
• Humidifiers / Condensers
AC
DC
Air In
Air Filter
GT
Compressor
GT Turbine
Start
Combustor
Exhaust
Recuperator
By-Pass
Valve
Blow-Off
Valve
Start Air
Heater
Solid Oxide
Fuel Cell
(SOFC)
Fuel Inlet (Natural Gas)Fuel
Heater
Fuel
Desulfurizer
Fuel Reforming
Reactor
Fuel By-Pass
Valve
Inert Gas
Generator
Anode Exhaust
Gas Flow
Fuel
Flow
Air
Cooler
Direct-Drive
Generator
Rectifier
DC Current
Out
Reformed
Fuel Flow
Air In
Not Mundane:
Understanding
Design &
Performance
are Essential
© National Fuel Cell Research Center, 2011 7/66
Introduction: Fuel Cell System
Fuel Processor - System design variations
Low temperature fuel cell system
• Temperature of FC heat
not compatible with
fuel processor
• Susceptible to
poisoning
High Temperature fuel cell system
• Temperature of FC heat
is compatible with
fuel processor
• More inherent
fuel flexibility
© National Fuel Cell Research Center, 2011 8/66
Fuel Cell Gas Turbine Hybrid System
Hybrid Fuel Cell/Gas Turbine Systems
C
C
CAir
Fuel
C TT Generator
C = Compressor; T = Turbine
Combustion 60%
70%
70+%
HYBRID FC/GT
Introduction: Hybrid System Concept
1 MW
2011
Gas Turbine System
© National Fuel Cell Research Center, 2011 9/66
Introduction
Needs for Fuel Cell Systems Advancement
• Understanding and use of thermodynamics & heat
transfer for the design & analysis of integrated systems
• Understanding of integrated fuel cell and hybrid fuel cell gas turbine system dynamics• Fuel cell systems
• Gas turbine systems
• Solar and wind power systems
• Batteries, ultracapacitors, inverters, other energy storage or
conversion devices as integrated into systems
• Dynamic models of fuel cell physics, chemistry,
electrochemistry
• Development and evaluation of control systems and
strategies for fuel cells
• Macro energy systems integration (e.g., utility grid)
© National Fuel Cell Research Center, 2011 10/66
Outline
• Introduction
• System Design and Steady State Performance
• Dynamic Performance & Understanding
• Control Systems Development
• Summary
© National Fuel Cell Research Center, 2011 11/66
Air
Motor
SOFC
Blower
Oxid-
izer
Oxid-
izer
Refor-
mer
Heat
Exch.
Fuel
+ H2O
Exit
Heat
Exch.Steam
Prep.
System Design
Integrated Stand-Alone systems
• SOFC minimum component realization
• Motor-blower, steam preparation, reformer reactor, oxidizer and
heat exchangers
Mueller, F., Jabbari, F., Brouwer, J., Journal of
Power Sources, Vol. 187, Iss. 2, pp. 452-460, 2009
© National Fuel Cell Research Center, 2011 12/66
System Design
Integrated Stand-Alone systems
• PEMFC minimum system realization
• Pump, water recovery
(enthalpy wheel), stack,
ATO, humidifier
stack cooling,
DI water circuit
• Desulfurizer,
humidifier,
CPO, several
HTS reactors,
LTS, PROX,
several heat
exchangers
Min, K.D., Kang, S., Mueller, F.,
Auckland, J. and Brouwer, J. J. Fuel Cell
Sci. Technol., Vol. 6, 041015, 2009
Fuel
DI Water
Air (O2/C)=0.6
DI Water
Air InAnode Inlet
Condensed Water
© National Fuel Cell Research Center, 2011 13/66
Hybrid System Configurations
AirGenerator/
Motor
Compressor
Turbine
Heat
Exch SOFCOxid-
izer
Oxid-
izer
Fuel
Blower
Comb
Fuel
Fuel Cell Module
Bleed
Exhaust
SOFC
Air
Fuel
+ H2O
Generator/
Motor
Compressor
Turbine
Heat
Exch.Exit
Oxid-
izer
Oxid-
izer
Refor
mer
Refor
mer
Fuel
Air
Fuel
+ H2O
Gen
Comp
ressor
Turbine
Fuel
Heat
Fuel
Heat
Oxid
izer
Heat
Exch
Heat
Exch
FC
Ref
Heat
Exch
Heat
Exch
Gen
NG
SOFC
Turbine Turbine
NG
Compressor
C1 C2
HX
Comb
Ref
Exhaust
© National Fuel Cell Research Center, 2011 14/66
Integrated Gasification Fuel Cell Plant
IGFC Concept Introduction
Coal
Prep.
Coal
Gasification
Syngas
Clean-upSOFC
Gas
TurbineSteam
Turbine
CO2 Separation
& Recycle
A catalytic hydro-gasifier IGFC system that takes advantage of the
potential benefits of CH4-rich syngas fuel can achieve more than 60%
efficiency while enabling carbon dioxide separation for sequestration
Li, et al., Journal of Power Sources,
Vol. 195, Iss. 17, pp. 5707-5718, 2010.
© National Fuel Cell Research Center, 2011 15/66
Model Development
• Most system development and analyses are based upon
bulk (0-dimensional) models
• Several important operating constraints cannot be
assessed without some geometric resolution of the SOFC
• Peak temperature, temperature gradients
• Fuel & oxidant utilization
• We desire to resolve some features of modern SOFC
operation
• need computational simplicity/efficiency sufficient to incorporate
the model into detailed integrated gasification systems analysis
• Explicitly evaluate activation, ohmic, and diffusion losses as well
as kinetics of hydrocarbon reactions
• Predict performance features such as the internal temperature,
current/power density and flow composition profiles, fuel and
oxidant utilization, for evaluation of fuel cell operating constraints
© National Fuel Cell Research Center, 2011 16/66
Planar SOFC Model Geometry
Quasi-2D co/counter flow planar SOFC model
Li, M., Powers, J.D., and Brouwer, J., Journal of Fuel Cell
Science and Technology, Vol. 7, pp. 041017-1-12, 2010
© National Fuel Cell Research Center, 2011 17/66
Key Simplifications & Assumptions
• Steady state model
• Resolve gradients in primary flow direction
• 4 separate temperatures resolved in each node
• Positive electrode-electrolyte-negative electrode (PEN) structure
• interconnect
• fuel flow
• air flow
• H2 electrochemical oxidation only (CO oxidized through
water-gas shift reaction)
• Water-gas shift reaction is always in equilibrium
• Methane reformation is controlled by local chemical kinetics
• External heat loss is by radiation heat transfer to vessel only
• Large Peclet number, effect of axial heat conduction in gas
phases is negligible Li, M., Powers, J.D., and Brouwer, J., Journal of Fuel Cell
Science and Technology, Vol. 7, pp. 041017-1-12, 2010
© National Fuel Cell Research Center, 2011 18/66
Numerical Scheme
Li, M., Powers, J.D., and Brouwer, J., Journal of Fuel Cell
Science and Technology, Vol. 7, pp. 041017-1-12, 2010
PEN
PSR PSR PSR
PSR PSR PSR
© National Fuel Cell Research Center, 2011 19/66
1-D Model Integration into Systems Analysis
Catalytic hydro-gasifier IGFC system
HP SOFC & Heat
Exchange System
(1-D, 0.8V, 73% f)
Li, et al., Journal of Power Sources,
Vol. 195, Iss. 17, pp. 5707-5718, 2010.
© National Fuel Cell Research Center, 2011 20/66
1-D counter-flow SOFC model in integrated IGFC analysis
• Peak temperatures move to SOFC interior
• Inlet & outlet temperatures no longer represent peak T
• Outlet fuel/air temperatures are decreased – disabling
downstream heat use
• Air flow required for ∆Tmax=200°C is 4X that of 0-D
model
Challenges Identified: 0-D vs. 1-D
fuel out
(650 + 200) °Cair out
(650 + 200) °C
fuel in
650 °C
air in
650 °C
fuel out
(650 + 40) °Cair out
(650 + 70) °C
fuel in
650 °Cair in
650 °C
© National Fuel Cell Research Center, 2011 21/66
IGFC Performance Comparison
Item 0-D Model 1-D Single Stage
Counter-flow SOFC
Coal energy input 1,397 GJ/h (HHV) 1,397 GJ/h (HHV)
SOFC operation pressure 10 atm 10 atm
Gross power output
SOFC electrical power 247.8 MW 247.3 MW
Cathode exhaust expander 63.4 MW 178.6 MW ↑
Steam turbine 2.6 MW 1.9 MW
Syngas reactor/expander topping cycle 9.3 MW 7.6 MW
Total gross power generated 323.3 MW 435.6 MW ↑
Auxiliary power consumption (incomplete list)
ASU 2,186 kW 2,186 kW
SOFC air compressor/blower 66,906 kW 242,499 kW ↑↑↑
Recycled H2 compressor 8,235 kW 8,283 kW
Total internal power consumption
and losses84.7 MW 260.5 MW ↑↑↑
Net electric power 238.6 MW 175.1 MW ↓↓↓
Overall thermal efficiency 61.5% (HHV) 45.1% (HHV) ↓↓↓
Li, M., Rao, A.D., Brouwer, J., and Samuelsen, Journal of
Power Sources, Vol.195, Iss. 17, pp. 5707-5718, 2010.
© National Fuel Cell Research Center, 2011 22/66
Strategy for Mitigating High T Challenge
Cascade SOFC stacks
Overall
Uf = 0.727
Ua = 0.455
Air in
650°C
Fuel in
650°C
Fuel out
671°C
Uf = 0.70
Ua = 0.15
Air addition
330°C
Air
713°C
Fuel in
650°C
Fuel out
689°C
Uf = 0.73
Ua = 0.16
Air addition
330°C
Air
732°C
Fuel in
650°C
Fuel out
704°C
Uf = 0.73
Ua=0.17
Air addition
330°C
Air
742°C
Fuel in
650°C
Fuel out
719°C
Uf = 0.74
Ua = 0.17
Air out
753°C
Li, M., Rao, A.D., Brouwer, J., and Samuelsen, Journal of
Power Sources, Vol.195, Iss. 17, pp. 5707-5718, 2010.
© National Fuel Cell Research Center, 2011 23/66
IGFC Performance Comparison
Item 0-D Model 1-D Cascading
Counter-flow SOFCs
Coal energy input 1,397 GJ/h (HHV) 1,397 GJ/h (HHV)
SOFC operation pressure 10 atm 10 atm
Gross power output
SOFC electrical power 247.8 MW 247.8 MW
Cathode exhaust expander 63.4 MW 72.1 MW ↑
Steam turbine 2.6 MW 2.7 MW
Syngas reactor/expander topping cycle 9.3 MW 7.6 MW
Total gross power generated 323.3 MW 330.4 MW ↑
Auxiliary power consumption (incomplete list)
ASU 2,186 kW 2,186 kW
SOFC air compressor/blower 66,906 kW 84,748 kW ↑
Recycled H2 compressor 8,235 kW 9,792 kW ↑
Total internal power consumption
and losses
84.7 MW 104.3 MW ↑
Net electric power 238.6 MW 226.1 MW ↓
Overall thermal efficiency 61.5% (HHV) 58.2% (HHV) ↓
Li, M., Rao, A.D., Brouwer, J., and Samuelsen, Journal of
Power Sources, Vol.195, Iss. 17, pp. 5707-5718, 2010.
© National Fuel Cell Research Center, 2011 24/66
Extend to Quasi-3D Cross-flow Planar SOFC
Quasi-3D cross-flow planar SOFC model – sample results
plots of cross flow planar SOFC PEN temperature and current density distributions
operated on syngas containing ~17 vol.% CH4 Uf = 85%, Ua = 14.7%
© National Fuel Cell Research Center, 2011 25/66
Outline
• Introduction
• System Design and Steady State Performance
• Dynamic Performance & Understanding
• Control Systems Development
• Summary
© National Fuel Cell Research Center, 2011 26/66
Dynamic Simulation Approach
Dynamic Energy Systems Simulation Framework
• MATLAB/Simulink® environment selected• User friendly, widely available/used, ideal for controls
development and testing
• Main assumptions:• quasi-steady state chemistry and electrochemistry (e.g.,
characterized by Nernst potential and losses)
• Simplified geometry (but including some geometric resolution)
• Focus on dynamic solution of the essential FC and other component features such as:• Nernst potential
• Electrochemical losses
• Species concentrations and Mass conservation
• Energy conservation
• Momentum conservation
• Heat Transfer
• Chemical ReactionGemmen, R, Liese, E., Rivera, J., Jabbari, F, and
Brouwer, J., ASME Paper Number 2000-GT-554, 2000.
© National Fuel Cell Research Center, 2011 27/66
Dynamic Simulation Approach
out
NinNin
outN
out
OHOHinOHin
outOH
out
COCOinCOin
outCO
out
HHinHin
outH
outRinout
out
outout
N
dt
VCdXN
X
N
dt
VCdRXN
X
N
dt
VCdRXN
X
N
dt
VCdRXN
X
dt
VCdNNN
RT
PC
)()(
)(
)()(
)(
)()(
)(
)()(
)(
)(
22
2
222
2
222
2
222
2
R+N-N=dt
dCV iii
i
outletinlet
)ii/-(1nF
TR-=L L
uC ln
F-AP-AP=dt
vdV soutletoutletinletinlet
)(
]][[
][]][[ln
,22
2/1
,2
2/1
22
aCOOH
cCOOHu
yy
Pyyy
nF
TRE=E
)i(i/Fn
TR=L o
uA ln
PP=P ac,
ACR LLLE=Vcell
Species Conservation Sample Mass Conservation Equations
Momentum Conservation
Nernst Equation
Electrochemical Losses
Cell Voltage
iR=L cellR
Roberts, R., Mason, J., Jabbari, F., Brouwer, J., Samuelsen, S., Liese,
E. and Gemmen, R., ASME Paper Number 2003-GT-38774, 2003.
© National Fuel Cell Research Center, 2011 28/66
Example Dynamic Simulation Modules
• Cell Solid
• Interconnect Plates
Planar and Tubular SOFC Discretization – 10 Nodes
• Anode Gas
• Cathode Gas
10 NODES
REFORMED
FUEL
CATHODE GAS
CELL SOLID INTERCONNECT
ANODE GAS
CELL TUBE
AIR SUPPLY PIPE
CATHODE GAS
CROSS SECTION
REFORMED
FUEL
PRE-
HEATED
AIR
© National Fuel Cell Research Center, 2011 29/66
Example Dynamic Simulation Modules
• PLANAR NODAL SOFC HEAT TRANSFER
RESISTANCES
BI-POLAR PLATE
NODE n NODE n+1
x
RRAD
RCONV
RCONV
RCONV
RCOND
RCONDRCOND RCOND
RCOND
RRAD
RCOND
RCONV
RCONV
RCONV
ANODE
IN
ANODE
OUT
CATHODE
OUT
CATHODE
IN
RCONVRCONV
RRAD RRAD
CELL
BI-POLAR PLATE
RCONDRCOND RCOND
© National Fuel Cell Research Center, 2011 30/66
Example Dynamic Simulation Modules
• REFORMER – Siemens Power Type
• 5 node model
• Concentric cans
• Heat from exhaust gas heat exchange
NODES
NATURAL
GAS
EXHAUST
STEAM /
DEPLETED FUEL
REFORMATE
FC EXHAUST
Adiabatic Mixing Volume
Catalyst Bed
© National Fuel Cell Research Center, 2011 31/66
Example Dynamic Simulation Modules
GAS TURBINE
• Based on generic compressor/expander performance maps
• Dynamic mass conservation through the plenum volume
• Shaft speed and angular momentum are solved by sum of the
torques method on the turbine shaft
Air In
Compressed Air OutCompressed Air OutPlenum
Volume
Power = Torque*RPM
Hot Compressed Air In
Alternator
lossloadCT PPPPJ
1
t
)( outin mmV
RT
dt
dP
© National Fuel Cell Research Center, 2011 32/66
Sample Module Evaluation and Verification
• Model Integration and Verification: Single MCFC Test
Stand
© National Fuel Cell Research Center, 2011 33/66
Sample Module Evaluation and Verification
• MCFC Comparisons of Agglomerate, Simplified
Models & Data
© National Fuel Cell Research Center, 2011 34/66
Sample Module Evaluation and Verification
• MCFC Comparisons of Agglomerate, Simplified
Models & Data
© National Fuel Cell Research Center, 2011 35/66
Quasi 3-D Dynamic FC Model Verification
35/
Fuel Inlet
Air Inlet
Active Cell (550cm^2)
5x5 Grid
Cross-flow Configuration
0
0.05
0.1
0.15
0.2
0.25
0 0.05 0.1 0.15 0.2 0.25
Fuel Flow Direction
Air F
low
Dire
ctio
n
980
990
1000
1010
1020
1030
© National Fuel Cell Research Center, 2011 36/66
Sample System Simulation Evaluation
220 kW HYBRID SYSTEM:
• SCE, Siemens Power Corp. - SOFC with IRES micro-turbine
• Over 2950 hours of operation; 53% net AC electrical efficiency
© National Fuel Cell Research Center, 2011 37/66
Sample System Simulation Evaluation
• Siemens Power Corporation (with SCE)Air
Natural
Gas
Generator/
Motor
CompressorTurbine 1
SOFC
Exit
Anode
Cathode
Heat
Exch.
Turbine 2
Comb Natural
Gas
Comb Natural
Gas
Air
Natural
Gas
Generator/
Motor
CompressorTurbine 1
SOFC
Exit
Anode
Cathode
Heat
Exch.
Heat
Exch.
Heat
Exch.
Turbine 2
CombCombCombComb Natural
Gas
CombCombCombComb Natural
Gas
© National Fuel Cell Research Center, 2011 38/66
Sample System Simulation Evaluation
• Model Integration and Verification: Sample ResultsSOFC Power Experimental and Model Comparison
for the 220 kW SOFC/GT Hybrid
140
145
150
155
160
165
170
175
180
0 20000 40000 60000 80000 100000 120000 140000 160000
Time (sec)
SO
FC
Po
we
r (k
W)
an
d F
ue
l F
low
SL
PM
*(0
.30
)
0
5
10
15
20
25
30
35
Va
lve P
erc
en
t O
pe
n
Model SOFC Power
Experimenta SOFC Power
SOFC Fuel Flow
Recuperator Bypass Valve
SOFC Bypass Valve
Experimental SOFC Power
© National Fuel Cell Research Center, 2011 39/66
Sample System Simulation Evaluation
• Model Integration and Verification: Sample ResultsGas Turbine Power Experimental and Model Comparison
for the 220 kW SOFC/GT Hybrid
15
17
19
21
23
25
27
29
31
0 20000 40000 60000 80000 100000 120000 140000 160000
Time (sec)
GT
Po
we
r (k
W)
0
5
10
15
20
25
30
35
Pe
rce
nt
Op
en
Model GT Power
Experimental GT Power
Recuperator Bypass Valve
SOFC Bypass Valve
© National Fuel Cell Research Center, 2011 40/66
Sample System Simulation Evaluation
• 220 kW Hybrid – Diurnal Variation – Power (solid = data)
120
135
150
165
180
160
170
180
190
200
210
220
230
240
Time (hours)
SO
FC
Po
wer
(kW
)
15
20
25
30
35
Valv
e P
erc
en
t O
pen
;
Gas T
urb
ine P
ow
er
(kW
)
SOFC Power SOFC Power Model
Gas Turbine Power Gas Turbine Power Model
© National Fuel Cell Research Center, 2011 41/66
Sample System Simulation Evaluation
• 220 kW Hybrid – Diurnal Variations – VI (solid = data)
1600
1700
1800
1900
2000
160
170
180
190
200
210
220
230
240
Time (hours)
Avera
ge C
urr
en
t D
en
sit
y (
A/m
2)
0.65
0.675
0.7
0.725
0.75
Avera
ge C
ell V
olt
ag
e (
V)
Current Density Current Density Model
Voltage Voltage Model
© National Fuel Cell Research Center, 2011 42/66
Sample System Simulation Evaluation
• 220 kW Hybrid – Start-up – Power (solid = data)
120
135
150
165
180
120
130
140
150
160
Time (hours)
SO
FC
Po
wer
(kW
)
15
20
25
30
35
Valv
e P
erc
en
t O
pen
;
Gas T
urb
ine P
ow
er
(kW
)
SOFC Power SOFC Power Model
Gas Turbine Power Gas Turbine Power Model
© National Fuel Cell Research Center, 2011 43/66
Sample System Simulation Evaluation
• 220 kW Hybrid – Start-up – VI (solid = data)
1600
1700
1800
1900
2000
120
130
140
150
160
Time (hours)
Ave
rag
e C
urr
en
t D
en
sit
y (
A/m
2)
0.65
0.675
0.7
0.725
0.75
Ave
rag
e C
ell
Vo
lta
ge
(V
)
Current Density Current Density Model
Voltage Voltage Model
© National Fuel Cell Research Center, 2011 44/66
Outline
• Introduction
• System Design and Steady State Performance
• Dynamic Performance & Understanding
• Control Systems Development
• Summary
© National Fuel Cell Research Center, 2011 45/66
Control Approach Overview
Dynamic
ModelPower
&
DisturbanceTransient
Response
Operating
Requirements
Control
Concept
Input
Understand control challenges physically
Control & system solutions
Evaluate trade-offs and performance
Goals: Understand dynamic performance characteristics, develop and test control
concepts, and enhance the transient load following and disturbance rejection
capability of SOFC systems
Identify/capture control challenges
Tune designExtensively using models
to develop/evaluate controls
© National Fuel Cell Research Center, 2011 46/66
System Transients and Control Concepts
Air
Motor
SOFC
Blower
Oxid-
izer
Oxid-
izer
Refor-
mer
Heat
Exch.
Fuel
+ H2O
Exit
Heat
Exch.Steam
Prep.
Manipulated Variables
Goals
Control Challenges
• Current
• Fuel flow
• Air flow
• Bypass valve
• Load following
• Handle disturbances
& ambient variations
• Fuel depletion
• Fuel cell thermal management
• System power control
• Combustor temperature control
System Design
• Air preheating
• Reformer temperature
• Fuel steam to carbon
SOFC Example
© National Fuel Cell Research Center, 2011 47/66
Example: Fuel Flow and Current
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80Current (A)
Ce
ll V
olt
ag
e (
V)
0
5
10
15
20
25
30
35
40
45
Ce
ll P
ow
er
(W)
V(U=85%) V(U=80%) V(U=75%) V(U=70%)P(U=85%) P(U=80%) P(U=75%) P(U=70%)
(K-I)P
rPfc
yPgt
ui+
Sat.Sat.
rP
yPfc
+ePfc
FFi
rP
bifi
+
+
fNfc
(K-I)tc
etc bNfcrtc
ytc
rP
uNfc
+
+
+
FFNfc
Sat.Sat.
1195
1205
1215
1225
1235
1245
0.001 0.01 0.1 1 10 100
Time (s)
Co
mb
us
tor
Te
mp
era
ture
(K
)
N=0.2s-P=inst.
N=2s-P=inst.N=10s-P=inst.
N=10s-P=30s
Fuel
Depletion
© National Fuel Cell Research Center, 2011 48/66
Example: FC Thermal Management
in,AnodeTXN
mol
kJ8.241HOHO
2
1H 298222
out,AnodeTXN
HEATHEAT
in,CathodeTXNout,CathodeTXN
MEA
ANODE
CATHODE
mol
kJ0.165HCOH4OH2CH 2982224
mol
kJ15.41HCOHOHCO 298222
Chemical
Reactions
Electro-Chemical
Reaction
ELECTRIC ELECTRIC
WORKWORK
x
Thermal
EMF
Current
Vo
ltag
e
Nernst
Voltage
Operating
Voltage
GH
ST
Operating Point
Power Generated
Heat Generated
fBY
(K-I)T
eT bBYrT
yT
rP
uBY
+
+
+
FFby
Sat.Sat.
genoutoutoutinininV Q)T(hN)T(hNdt
dTC
Gen
NG
SOFC
Turbine Turbine
NG
Compressor
C1 C2
HX
Comb
Ref
Exhaust
© National Fuel Cell Research Center, 2011 49/66
Example: System Integration
uNtc
yTIN
uBY1
yP
rP ui
uBY2
uNfc
F(s)
N(s)
yTstack
F(s)~ Power Controller
N(s)~ Fuel Cell Fuel Flow Controller
B(s)~ Fuel Cell Temperature Controller
C(s)~ Cathode Inlet Temperature Controller
T(s)~ Turbine Inlet Temperature Controller
B(s)
C(s)
yTstack
ytit
T(s)
ytc
SO
FC
Syste
m
Centralized control approaches (e.g., H-Infinity) work well
Decentralized control loops are possible due to variety of system response times
Feed forward to get actuators close to desired operating point
Feedback to reject undesired transients and external disturbances
Gen
NG
SOFC
Turbine Turbine
NG
Compressor
C1 C2
HX
Comb
Ref
Exhaust
© National Fuel Cell Research Center, 2011 50/66
Application to Fuel Cell System Controls
• MCFC Hybrid (after FuelCell Energy DFC/T® design)Air
Fuel
+ H2O
Generator/
Motor
Compressor
Turbine
MCFC Oxid-
izer
Fuel
Heater
Heat
Exch.
Heat
Exch.Exit
Anode
Cathode
Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., Journal of Engr.
for Gas Turbines and Power, Vol.128, Iss. 2, pp. 294-301, 2006.
© National Fuel Cell Research Center, 2011 51/66
Application to Fuel Cell System Controls
• Open Loop MCFC Temperature Transient - Cathode
Inlet Temperature Rises (848 871 K) during load shed
© National Fuel Cell Research Center, 2011 52/66
Air
Fuel
+ H2O
Generator/
Motor
Compressor
Turbine
MCFC Oxid-
izer
Fuel
Heater
Heat
Exch.
Heat
Exch.Exit
Anode
Cathode
Application to Fuel Cell System Controls
• MCFC Hybrid (after FuelCell Energy DFC/T® design)
Maintain a safe
operating temperature
for the catalytic
oxidizer
• Control Goals
• Maintain proper
temperatures
throughout the hybrid
system
• Maintain operation of
the gas turbine
• Operate the MCFC
efficiently and safely
Control compressor
mass flow by
manipulating generator
power with MCFC
temperature feedback
Fuel flow rate into the
MCFC is controlled to
maintain a safe
oxidizer temperature &
MCFC voltage
Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., Journal of Engr.
for Gas Turbines and Power, Vol.128, Iss. 2, pp. 294-301, 2006.
© National Fuel Cell Research Center, 2011 53/66
Application to Fuel Cell System Controls
System Power: Control Approaches #1 & #2, Load Shed
700
750
800
850
900
950
1000
1050
0 10 20 30 40 50 60 70 80 90 100Time (s)
Fu
el C
ell P
ow
er
(kW
) ;
To
tal
Po
wer
(kW
)
100
105
110
115
120
125
130
135
140
145
150
Ga
s T
urb
ine
Po
we
r (k
W)
NFCRC Total NETL Total NCFRC FC
NETL FC NFCRC GT NETL GT
App. #1 – TOTAL
App. #2 – FC
App. #2 – TOTAL
App. #1 – GT
App. #1 – FC
App. #2 – GT
Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., J. Engr.
for Gas Turbines and Power, Vol.128, Iss. 2, pp. 294-301, 2006.
© National Fuel Cell Research Center, 2011 54/66
Application to Fuel Cell System Controls
1090
1100
1110
1120
1130
1140
1150
0 10 20 30 40 50Time (s)
Cata
lyti
c O
xid
izer
Tem
pe
ratu
re (
K)
835
837
839
841
843
845
847
849
Cath
od
e In
let
Te
mp
(K
)
NFCRC Catalytic Ox. Temp NETL Catalytic Ox. Temp
NFCRC Cathode Inlet Temp NETL Cathode Inlet Temp
Temperatures: Control Approaches #1 and #2, Load Shed
App. #1 – Catalytic Ox Temp
App. #1 – Cathode Inlet Temp App. #2 – Catalytic Ox Temp
App. #2 – Cathode Inlet Temp
Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., J. Engr.
for Gas Turbines and Power, Vol.128, Iss. 2, pp. 294-301, 2006.
© National Fuel Cell Research Center, 2011 55/66
Application to Fuel Cell System Controls
• Closed Loop MCFC Temperature Transient - Cathode
Inlet Temperature Drops during load shed
© National Fuel Cell Research Center, 2011 56/66
Example: Sudden Decrease of Power
Hybrid SOFC/GT System
• Manipulate:
• Recirc. blower power
• Fuel flow
• Air preheat bypass valve
• SOFC air bypass valve
• Control:
• System power
• Peak SOFC temperature
• SOFC temperature gradient
• Oxidizer temperature
• Perturbation:
• Sudden decrease from 100%
to 50% full powerMcLarty, D.F., Samuelsen, S., and Brouwer, J.
ASME Paper FC2010-33328, June, 2010
© National Fuel Cell Research Center, 2011 57/66
Example: Sudden Decrease of Power
Hybrid SOFC/GT System
• Met sudden decrease
in power demand
• Kept SOFC peak
temperature < 1073 K
during transient
• Kept SOFC temperature
gradient < 150 K
during transient
McLarty, D.F., Samuelsen, S., and Brouwer, J.
ASME Paper FC2010-33328, June, 2010
© National Fuel Cell Research Center, 2011 58/66
Air
Motor
SOFC
Blower
Oxid-
izer
Oxid-
izer
Refor-
mer
Heat
Exch.
Fuel
+ H2O
Exit
Heat
Exch.Steam
Prep.
Example: Sudden Increase in Power
Integrated Stand-Alone SOFC system
• Manipulate:
• Fuel flow
• Blower power
• Bypass valve
• Control:
• System power
• Peak SOFC temperature
• SOFC temperature profile
• Perturbation:
• 25 to 70 amp current increase with PEN temperature feedback
Mueller, F., Jabbari, F., Brouwer, J., Journal of
Power Sources, Vol. 187, Iss. 2, pp. 452-460, 2009
© National Fuel Cell Research Center, 2011 59/66
PE
N T
em
p (
K)
Refo
rme
r
Tem
p (
K)
Time (s)
Time (s)
Example: Sudden Increase in Power
Integrated
SOFC
system
25 to 70 amp
current
increase
perturbation
Control actions:
© National Fuel Cell Research Center, 2011
Mueller, F., Jabbari, F., Brouwer,
J., Journal of Power Sources, Vol.
187, Iss. 2, pp. 452-460, 2009
© National Fuel Cell Research Center, 2011 60/66
Initial 0-s Peak 874s Final 50ksTransition 1050s
PE
N T
em
p (
K)
Curr
ent (A
)
Example: Sudden Increase in Power
Integrated SOFC system - 25 to 70 amp current increase
with PEN temperature feedback
Mueller, F., Jabbari, F., Brouwer, J., Journal of
Power Sources, Vol. 187, Iss. 2, pp. 452-460, 2009
© National Fuel Cell Research Center, 2011 61/66
Outline
• Introduction
• System Design and Steady State Performance
• Dynamic Performance & Understanding
• Control Systems Development
• Summary
© National Fuel Cell Research Center, 2011 62/66
Summary
• Introduced importance of FC systems integration
• Developed a novel, simple but resolved, simulation
approach for steady-state & dynamic system modeling
• Demonstrated the importance of spatial and temporal
resolution of relevant physics, chemistry,
electrochemistry
• Provided examples of application, insights
• Applied tools to develop and test control systems and
strategies for integrated FC systems
• Inter-disciplinary innovations and integrated systems
study, development and demonstration are essential to
fuel cell advancement
© National Fuel Cell Research Center, 2011 63/66
Acknowledgements
• Funding Agencies:
• U.S. Department of Energy
• California Energy Commission
• U.S. Environmental Protection Agency
• Collaborating Faculty:
• Faryar Jabbari Joongmyeon Bae
• Keyue Smedley Scott Samuelsen
• Research Colleagues & Students:
• Randy Gemmen Ashok Rao
• Fabian Mueller Ghazal Razeghi
• Rory Roberts Travis Shultz
• Dustin McLarty Marc Carreras
• Tomohiko Kaneko Andrew Martinez
• Mu Li Hossein Ghezel-Ayagh
© National Fuel Cell Research Center, 2011 64/66
Acknowledgements
Participating Organizations:
• Siemens Power Corporation
• FuelCell Energy, Corp.
• National Energy Technology Laboratory
• Southern California Edison
• U.S. Department of Defense Fuel Cell Program
© National Fuel Cell Research Center, 2011 65/66
Renewable Systems Challenges
Wind Power – Example of Non-Coincidence with Peak
Demand
CAISO, 2007
Need some energy storage and/or dispatchable power
to shift the resource to match demand
© National Fuel Cell Research Center, 2011 66/66
Renewable Systems Challenges
Energy Deployment Model Results - 33% Wind Penetration
With “Deep Grid Situational Awareness” we can
automatically and instantaneously dispatch local
generation, energy storage, demand response, …
© National Fuel Cell Research Center, 2011 67/66
STORAGE
TANK
ADG
HOT
WATER
HEAT
EXCHANGER ANAEROBIC
DIGESTION
GAS HOLDER
SLUDGE
DIGESTER
National Fuel Cell Research Center
University of California, Irvine
BOILER
HYDROGENHYDROGEN
STORAGE
HYDROGEN
DISPENSER
FUEL
TREATMENT
AC
POWER
PROJECT
HIGH-T
FUEL CELL
PROJECT:
• Orange County Sanitation District
• Euclid Exit, I405, Fountain Valley
• Support: DOE, ARB, AQMD, CEC
• Initial Operation Underway
Renewable Energy Station
© National Fuel Cell Research Center, 2011 68/66
Energy Station Concept 1, 2, 3
Locally
available
feedstock:
Natural Gas,
ADG,
Landfill Gas, ….
Electricity
Heat
Hydrogen
Energy Station ConceptIntroduction and Background
1 Brouwer et al., 2001; 2 CHHN Blueprint Plan, 2005; 3 Leal and Brouwer, 2006
© National Fuel Cell Research Center, 2011 69/66
100 MJ
of CH4
143 MJ
of CH4
HTFC
47 MJ
electricity
η=47%
43 MJ
H2
η=100%
53 MJ high
quality heat
53%
with
TRI-
GENERATIO
N
Synergies: • Higher electrochemical efficiency (fuel utilization)
• Less electrochemical heat generation
• More internal reformation/cooling
• Less blower power
Renewable Energy Station
Synergies Produce Remarkable Performance
© National Fuel Cell Research Center, 2011 70/66
Status
• Wastewater Treatment 9.40
• Directed BioGas 8.90
• Hotels 2.75
• Government 2.25
• Universities 3.00
• Breweries 1.00
• Industrial 3.20
• Manufacturing 1.50
• Commercial 2.50
• Utilities 0.25
TOTAL = 34.75 MW
Sierra Nevada Brewery
Chico
SOURCE: CASFCC.ORG
Waste Water Treatment Plant
Tulare
California State University
Northridge
Sheraton Hotel
San Diego
Wastewater Treatment Plant
Santa Barbara
© National Fuel Cell Research Center, 2011 71/66
Status
• Wastewater Treatment 9.40
• Directed BioGas 8.90
• Hotels 2.75
• Government
2.25
• Universities
3.00
• Breweries 1.00
• Industrial 3.20
• Manufacturing 1.50
• Commercial
2.50
• Utilities 0.25
TOTAL = 34.75 MW
SOURCE: CASFCC.ORG
Stockton College
Stockton
Whole Foods
San Jose
Cox
Communications
San Diego, Rancho
Santa Margarita
St. Helena Hospital
St. Helena
Albertsons
San Diego
© National Fuel Cell Research Center, 2011 72/66
500 kW, June 2009
500 kW, Feb 2010
400 kW, Jan 2010
Status
400 kW, July 2008
Status
© National Fuel Cell Research Center, 2011 73/66
Backup Slides
© National Fuel Cell Research Center, 2011 74/66
Introduction and Background
Poly-generation of Power, Heat and H2
• Advantages: 4, 5, 6
• H2 production is at the point of use averting emissions and
energy impacts of hydrogen and electricity transport
• Fuel cell produces sufficient heat and steam as the primary
inputs for the endothermic reforming process
• Synergistic impacts of lower fuel utilization increases overall
efficiency (i.e., higher Nernst Voltage, lower polarization
losses, lower cooling requirement and associated air blower
parasitic load)
• Potential Disadvantage:
• May not be compatible with carbon sequestration4 Leal and Brouwer, 2006; 5 O’Hayre, R., 2009; 6 Margalef et. al, 2008
© National Fuel Cell Research Center, 2011 75/66
• EXAMPLE: Efficiency of a Poly-Generating Hydrogen
Energy Station (H2ES) without valuing heat
Poly-Generation Analyses
Electricity
production with
state-of-the-art
natural gas
combined cycle
Centralized SMR
Plant
(H2 production)
(Case: H2ES)
Poly-generating
HTFC
Fuel
Fuel
Fuel
Electricity
Hydrogen
η el,1 = 61.2%η el,2 = 51.7%η el,3 = 58.4%
η H2,1 = 80.9%η H2,2 = 54.9%η H2,3 = 83.5%
η el,pp = 60%
η H2,SMR = 79%
ηtot = 69.5%
© National Fuel Cell Research Center, 2011 76/66
• Electrochemistry & Reformation Synergy – Air Flow
30
40
50
60
70
80
90
100
0.4 0.5 0.6 0.7 0.8
Air
flo
w in
[km
ol/
hr]
Fuel Utilization Factor
Factor #1electrochem
. heat
Poly-Generation Analyses
Factor#2reformation
cooling
© National Fuel Cell Research Center, 2011 77/66
Poly-Generation Renewable Energy System
Orange County Sanitation District (OCSD) Project
Sponsors & Participants
© National Fuel Cell Research Center, 2011 78/66
OCSD Project Status
• Factory Test in Danbury, CT completed
© National Fuel Cell Research Center, 2011 79/66
OCSD Project Status
• Installation Complete (except ADG skid), Shakedown,
Initial Operation Underway Orange County
Sanitation
District
(OCSD)
Renewable H2
Filling Station
ADG fueled
DFC-H2®
Production Unit
© National Fuel Cell Research Center, 2011 80/66
1
1.5
2
2.5
3
3.5
4
4.5
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
Normalized Flow
Pre
ss
ure
Ra
tio 0.60
0.70
0.80
0.90
1.00
System
Normalized
RPMSurg
e Lin
e
1
1.5
2
2.5
3
3.5
4
4.5
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
Normalized Flow
Pre
ss
ure
Ra
tio 0.60
0.70
0.80
0.90
1.00
System
Normalized
RPM
1
1.5
2
2.5
3
3.5
4
4.5
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
Normalized Flow
Pre
ss
ure
Ra
tio 0.60
0.70
0.80
0.90
1.00
System
Normalized
RPMSurg
e Lin
e
Complementary Dispatch
0 50000 100000 150000 200000160
162
164
166
168
170
FC
Pow
er
[kW
]Time [sec]
Experiment
Model
FC Power
Jan 2001
0
20
40
60
80
100
120
140
160
180
200
Jan-7 Jan-9 Jan-11 Jan-13 Jan-15 Jan-17 Jan-19 Jan-21
Day
Po
wer
[kW
]
0
5
10
15
20
25
30
35
40
45
50
Co
mp
. in
let
Tem
p.
[C]
Experiments &
Models suggest good
dynamic response is
possible
© National Fuel Cell Research Center, 2011 81/66
SCE 220 kWe PSOFC/GT Performance - SAT1
0
20
40
60
80
100
120
140
160
180
0 50 100 150 200 250
Time, hours
[Since June 3, 2000]
Po
wer
, kW
e an
d
Eff
icie
ncy
, %
0
200
400
600
800
1000
1200
Tem
per
atu
re,
C
SOFC DC kWe MTG AC kWe AC Efficiency % SOFC Temperature Ambient Temp. * 10
STOP
STOP- Low Terminal Voltage
(Power lead failure)
EXAMPLE RESULTS
SOFC DC kW MTG AC Kw AC EFFICIENCY % SOFC TEMP AMBIENT TEMPx10
• UNATTENDED OPERATION
• SUNDAY
• SHUT DOWN CONTROL “EXERCISED”
• SUCCESSFUL
4
3
2
5
1
(1) STOP: HIGH POWER LEAD RESISTANCE6
© National Fuel Cell Research
© National Fuel Cell Research Center, 2011 82/66
AIR
EXHAUST
OXIDIZER
RECUPERATOR
COMPRESSOR TURBINE
SOFC
FUEL
MTG-SOFC PRESSURIZED HYBRIDMTG-SOFC PRESSURIZED HYBRID
© National Fuel Cell Research
© National Fuel Cell Research Center, 2011 83/66
MCFC
EXHAUST
AIR
COMPRESSORTURBINE
FUEL
OXIDIZER
WATER
HEAT
RECOVERY
UNIT
MOLTEN CARBONATE FUEL CELL (MCFC)MCFC-MTG ONE ATMOSPHERE HYBRID
© National Fuel Cell Research
© National Fuel Cell Research Center, 2011 84/66© National Fuel Cell Research MO2512
73000
250KW DFC® STACK INTEGRATED WITH A CAPSTONE 330 MICROTURBINE
• 2,900 HOURS
• 209kW (NET AC)
– FC: 206.0 kW
– MTG: 9.5 kW
– PP: 6.5 kW
• NET EFFICIENCY: 51.7%
FUEL CELL ENERGY
U.S. DEPARTMENT OF ENERGY
VISION 21
MCFC-MTG ONE ATMOSPHERE HYBRID
© National Fuel Cell Research Center, 2011 85/66
Dynamic Modeling Results
0 50000 100000 150000 2000000.6
0.61
0.62
0.63
0.64
0.65
FC
Voltage [
V]
Time [sec]
Experiment
Model
Siemens Integrated
SOFC SystemSingle Cell
MCFC Test
Stand
0 1 2 3 4 5 618.5
19
19.5
20
20.5
Time (Hr)
Mo
du
le P
ow
er
(kW
)
Siemens/SCE 220
kW
SOFC/GT Hybrid
© National Fuel Cell Research Center, 2011 86/66
Example: Load Increase
10-2
10-1
100
101
102
103
104
100
150
200
250
300
Time (s)
Power Demand (kW) Power Out (kW) Voltage (V) Current/4 (A)
10-2
10-1
100
101
102
103
104
0
0.2
0.4
0.6
0.8
1
Time (s)
RPM/80 (kRPM) FC Fuel Flow (mol/s) FC Bypass
10-2
10-1
100
101
102
103
104
-5
0
5
Time (s)
Err
or
Power (kW)*100
Electrolyte Temp (K)Combustor Temp/2 (K)
10 kW per second: 150 to 200 kW load increase
© National Fuel Cell Research Center, 2011 87/66
Example: Load Following and
Disturbance Rejection
System response to a dynamic load, temperature variation, and large fuel disturbance
0 500 1000 1500 2000 2500 3000 3500 4000150
160
170
180
190
200P
ow
er
Dem
an
d (
kW
)
Time (s)
0 500 1000 1500 2000 2500 3000 3500 40000
0.5
1
Fu
el
Mo
le F
racti
on
Time (s)
XCH4
XN2
0 500 1000 1500 2000 2500 3000 3500 4000
280
290
300
310
Am
b T
em
p (
K)
Time (s)
0 500 1000 1500 2000 2500 3000 3500 4000-5
0
5
Time (s)
Err
or
Power (kW)*100 Electrolyte Temp (K) Combustor Temp/4 (K)
3 sec
Sampling
© National Fuel Cell Research Center, 2011 88/66
Additional Information
Publications
• Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., Dynamic Simulation of Carbonate Fuel Cell-Gas Turbine Hybrid Systems, ASME Journal of Engineering for Gas Turbines and Power, Volume 128, Issue 2, pp. 294-301, April, 2006.
• Roberts, R.A., and Brouwer, J., Dynamic Simulation of a 220kW Solid Oxide Fuel Cell Gas Turbine Hybrid System with Comparison to Data, ASME Journal of Fuel Cell Science and Technology, Volume 3, Issue 1, pp. 18-25, February, 2006.
• Mueller, F., Brouwer, J., Jabbari, F., and Samuelsen, G.S., Dynamic Simulation of an Integrated Solid Oxide Fuel Cell System Including Current-Based Fuel Flow Control, ASME Journal of Fuel Cell Science and Technology, Volume 3, Issue 2, pp. 144-154, May, 2006.
• Brouwer, J., Jabbari, F., Leal, E.M. and Orr, T., Analysis of a Molten Carbonate Fuel Cell: Numerical Modeling and Experimental Validation, Journal of Power Sources, Volume 158, Issue 1, pp. 213-224, July, 2006.
• Maclay, J.D., Brouwer, J., and Samuelsen, G.S., Dynamic Analyses of Regenerative Fuel Cell Power for Potential use in Renewable Residential Applications, International Journal of Hydrogen Energy, Volume 31, pp. 994-1009, 2006.
• Roberts, R.A., Brouwer, J., Jabbari, F., Junker, T., and Ghezel-Ayagh, H., Control Design of an Atmospheric Solid Oxide Fuel Cell/Gas Turbine Hybrid System: Variable versus Fixed Speed Gas Turbine Operation, Journal of Power Sources, Volume 161, pp. 484-491, 2006.
• Kaneko, T., Brouwer, J., and G.S. Samuelsen, Power and Temperature Control of Fluctuating Biomass Gas Fueled Solid Oxide Fuel Cell and Micro Gas Turbine Hybrid System, Journal of Power Sources, Volume 160, Issue 1, pp. 316-325, 2006.
• Traverso, A., Massardo, A., Roberts, R.A., Brouwer, J., and Samuelsen, G.S., Gas Turbine Assessment for Air Management of Pressurized SOFC/GT Hybrid Systems, ASME Journal of Fuel Cell Science and Technology, Volume 4, pp. 373-383, November, 2007.
• Mueller, F., Brouwer, J., Kang, S.G., Kim, H.-S., and Min, K.D., Quasi-Three Dimensional Dynamic Model of a Proton Exchange Membrane Fuel Cell for System and Controls Development, Journal of Power Sources, Volume 163, Issue 2, pp. 814-829, 2007.
• Mueller, F., Jabbari, F., Gaynor, R.M., and Brouwer, J., Novel solid oxide fuel cell system controller for rapid load following, Journal of Power Sources, Volume 172, pp. 308–323, 2007.
• Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., Dynamic Simulation of Carbonate Fuel Cell-Gas Turbine Hybrid Systems, ASME Journal of Engineering for Gas Turbines and Power, Volume 128, Issue 2, pp. 294-301, April, 2006.
© National Fuel Cell Research Center, 2011 89/66
Additional Information
Publications (cont’d)
• Mueller, F., Brouwer, J., Jabbari, F., and Samuelsen, G.S., Dynamic Simulation of an Integrated Solid Oxide Fuel Cell System Including Current-Based Fuel Flow Control, ASME Journal of Fuel Cell Science and Technology, Volume 3, Issue 2, pp. 144-154, May, 2006.
• Roberts, R.A., and Brouwer, J., Dynamic Simulation of a 220kW Solid Oxide Fuel Cell Gas Turbine Hybrid System with Comparison to Data, ASME Journal of Fuel Cell Science and Technology, Volume 3, Number 1, pp. 18-25, February, 2006.
• Meacham, J.R., Jabbari, F., Brouwer, J., Samuelsen, G.S., and Mauzey, J.L., Analysis of Stationary Fuel Cell Dynamic Ramping Capabilities and Ultra Capacitor Energy Storage using High Resolution Demand Data, Journal of Power Sources, Volume 156, Issue 2, pp. 472-479, July, 2006.
• Brouwer, J., Jabbari, F., Leal, E.M. and Orr, T., Analysis of a Molten Carbonate Fuel Cell: Numerical Modeling and Experimental Validation, Journal of Power Sources, Volume 158, Issue 1, pp. 213-224, July, 2006.
• Freeh, J.E., Pratt, J.W., and Brouwer, J., “Development of a Solid-Oxide Fuel Cell / Gas Turbine Hybrid System Model For Aerospace Applications,” ASME Paper Number GT2004-53616, June, 2004.
• Roberts, R., Mason, J., Jabbari, F., Brouwer, J., Samuelsen, S., Liese, E. and Gemmen, R., Inter-Laboratory Dynamic Modeling of a Molten Carbonate Fuel Cell, ASME Paper Number 2003-GT-38774, June, 2003.
• Gemmen, R, Liese, E., Rivera, J., Jabbari, F, and Brouwer, J., Development of Dynamic Modeling Tools for Solid Oxide and Molten Carbonate Hybrid Fuel Cell Gas Turbine Systems, ASME Paper Number 2000-GT-554, May, 2000.
• Liese, E. A., Gemmen, R. S., Jabbari, F., and Brouwer, J., Technical Development Issues and Dynamic Modeling of Gas-Turbine and Fuel Cell Hybrid Systems, ASME Paper Number 99-GT-360, January, 1999. Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., “Dynamic Simulation of Carbonate Fuel Cell-Gas Turbine Hybrid Systems,” ASME Paper Number GT2004-53653, June, 2004.
• Yuan, L., Brouwer, J., and Samuelsen, G.S., “Dynamic Simulation of an Autothermal Methane Reformer,” 2nd International Conference on Fuel Cell Science, Engineering and Technology, ASME Paper Number FuelCell2004-2518, June, 2004.
• Leal, E.M, Jabbari, F., and Brouwer, J., "Dynamic Numerical Modeling and Experimental Validation of a Molten Carbonate Fuel Cell," Proceedings of the 3rd International Conference on Fuel Cell Science, Engineering and Technology, ASME Paper Number FC2005-74104, May, 2005.
• Roberts, R.A., Brouwer, J., Liese, E., Gemmen, R.S., “Development of Controls for Dynamic Operation of Carbonate Fuel Cell Gas Turbine Hybrid Systems,” ASME Paper Number GT2005-68774, June, 2005.