STI
ISE
LENI
Thermo-economic modelling and
optimization of fuel cell systems
Francesca Palazzi, Julien Godat,
Dr François Marechal
Laboratory for Industrial Energy Systems
LENI ISE-STI-EPFL
Swiss Federal Institute of Technology - Lausanne
mailto:[email protected]
Presentation Plan
Thermo-ecomomic modelling and
optimization of fuel cell systems
•
•
•
•
Methodology
Modelling: integrated PEM system
Results
Discussion
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Project goals
• Optimal design of FC systems where the configuration
is unknown a priori
Thermo-economic optimization
Energy integration
Configuration options
FC-system model
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Methodology
Process flow model
VALI
•Chemical process modelling tool
•Thermodynamic calculations
•Block system equation solver
•Modular graphical interface
VALI-BELSIM, Belgium
www.belsim.com
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Methodology
Energy integration
EASY
•Process integration techniques
•Optimal heat exchange system model
•Additional hot and cold energy resources optimization
•Integrated system energy balance
Under development at LENI
leniwww.epfl.ch
Process flow model
VALI
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Methodology
Optimisation
MOO
•Multi-Objective Optimizer (Mixed Integer Non-Linear Programming)
•Based on advanced evolutionary algorithms
•Applicable to complex problems with discontinuities
•Robust and allow global optimization (multi-modal problems)
Developed at LENI
leniwww.epfl.ch
Process flow model
VALI
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
Energy integration
EASY
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Methodology
Optimisation
MOO
Decision variables
Performances
Equipment rating
and costing
State variables
Process flow model
VALI
State variables
Heat exchange
requirements
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
State variables
Energy integration
EASY
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Process flow model
VALI
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Energy flow model
• PEM system modelling (VALI):
define the process steps
Fuel
processing
Fuel Cell
Post
combustion
Heat exchange requirements
To energy integration (EASY)
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Energy flow model of subsystems
Fuel
processing
Fuel
processing
Fuel Cell
Post
processing
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
Post
combustion
Cleaning
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Subsystems superstructure
Fuel
processing
Post
processing
Process Alternatives
Cleaning
(energy flow level (VALI))
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Energy flow model
Utility
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Energy integration
EASY
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Energy integration
• Pinch technology, composite curves
TT5
T4
T3
T
Cp=b
Cp=a
Minimum of Energy Required
Hot composite curve
Cold composite curve
Cp=c
T2
T1
Minimum of Energy to Evacuate
H
Possible heat recovery
by heat exchange
H
Hot Utility:
streamssupplies
(Tin > Tou)
energy
= heat
to the
available
system
streamsremoves
(Tin < Tou)
= heat
required
Cold Utility:
energy
from
the system
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Utility system optimization
• Selection of the best utility system
• Combined heat and power
•Resolution by optimization inside EASY
•Additional methane flow rate
•Air excess flow rate
Cold Utility
=
Air Excess
Hot Utility
=
Additional Firing
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Methodology
Optimisation
MOO
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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MOO: multi-objective optimizer
•
•
•
•
Evolutionnary algorithm
Multi-objective optimization
Mixed Integer Non-Linear Programming
Clustering techniques
Identify global and local optima
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Objectives: thermo-economic
• Two objectives:
Maximum Efficiency
Minimum Specific Cost
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Methodology
Equipment rating
and costing
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Objectives computation
Efficiency:
Wbalance
en 
LHVCH 4  nCH 4 ,in
Wbalance
Power balance on
the system [kW]
nCH 4 ,in
Methane entering
the system [kmol/s]
LHVCH 4
Methane lower
heating value [kJ/kmol]
Wbalance  Wél , FC  Wmec ,result  WO2 , prod
Wél , FC
Fuel Cell power [kW]
Wmec ,result Resulting power from turbines and compressors [kW]
WO2 , prod
Electrical power cost of the oxygen production [kW]
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Objectives computation
Specific Cost:
CTot
CFP  CPEM  CPC

Wbalance
State
variables
Units
sizing
CFP
Fuel processing unit
investment cost
CPEM
Fuel cell investment cost
CPC
Post combustion unit
investment cost
Cost
computation
Methodology based on scaling from a reference case:
R. Turton, Analysis, Synthesis and Design of chemical processes,
Prentice Hall, NJ, 1998
Empirical formulas and reference cases:
C.E. Thomas, Cost Analysis of Stationary Fuel Cell Systems including
Hydrogen Co-generation, Directed Technologies, 1999
www.directedtechnologies.com.
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Decision variables
Fixed methane
flow rate
Selection
TFP
Steam / carbon
Oxygen to carbon
Fuel Utilization
Air enrichment
Post combustion
pressure
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Results: Pareto curve
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Pareto analysis
SMR
ATR
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Pareto analysis
Steam to carbon
ratio of the
optimal points
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Pareto analysis
Fuel processing
temperature of the
optimal points
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Pareto analysis
Post combustion
pressure of the
optimal points
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Pareto analysis
Fuel utilization of
the optimal points
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Results: Cost analysis
Specific cost by equipment [$/kW]
10
1200
1200
9
2
4
3
1000
800
800
Specific cost [$US/kW]
1
5
6 7
8
600
400
400
200
0
1 2 3 4 5 6 7 8 9 10
1
2
3
4
5
6
7
8
9
10
Point
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Summary
• Two level optimization:
– Energy Integration
– Thermo-economic Optimization Complete tool for
help to system design
• Complete tool for help to system design
• Process alternatives can be easily
implemented in the existing
superstructure (Fuel processing, SOFC, …)
• Interesting regions of the model are
identified for further investigation
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Aknowledgment
• The authors thank the Swiss Federal Office
of Enegy for the financial support of the
present project
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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I´ll be glad to answer your
Qestions !
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Pareto analysis
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Pareto analysis
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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Power analysis
Fraction of electrical power produced by each subsystem
PEM
Po wer rep art it io n
Turbine system
Power fraction produced by the
subsystem
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
5
6
7
8
9
10
Point
F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004
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