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 STI ISE LENI LENI

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 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 Thermo-economic optimization Energy integration Configuration options Project goals Optimal design of FC systems where the configuration is unknown a priori FC-system model

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Chemical process modelling tool Thermodynamic calculations Block system equation solver Modular graphical interface VALI-BELSIM, Belgium Methodology Process flow model VALI

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 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 Energy integration EASY Methodology Process flow model VALI

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 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 Methodology Process flow model VALI Energy integration EASY Optimisation MOO

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Methodology Process flow model VALI Energy integration EASY Optimisation MOO PerformancesDecision variables State variables Heat exchange requirements State variables Equipment rating and costing

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Process flow model VALI

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 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 Energy flow model of subsystems Fuel processing Fuel Cell Post combustion Fuel processing Post processing Cleaning

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Subsystems superstructure Fuel processing Post processing Cleaning Process Alternatives (energy flow level (VALI))

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Energy flow model Utility

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Energy integration EASY

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Energy integration Pinch technology, composite curves H T H T C p =a C p =c C p =b T2T2 T1T1 T3T3 T4T4 T5T5 Cold streams (Tin < Tou) = heat required Hot streams (Tin > Tou) = heat available Minimum of Energy Required Minimum of Energy to Evacuate Hot Utility: supplies energy to the system Cold Utility: removes energy from the system Hot composite curve Cold composite curve Possible heat recovery by heat exchange

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 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 Hot Utility = Additional Firing Cold Utility = Air Excess

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Methodology Optimisation MOO

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 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 Objectives: thermo-economic Two objectives: Maximum Efficiency Minimum Specific Cost

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Methodology Equipment rating and costing

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Objectives computation Efficiency: Methane lower heating value [kJ/kmol] Methane entering the system [kmol/s] Fuel Cell power [kW] Resulting power from turbines and compressors [kW] Electrical power cost of the oxygen production [kW] Power balance on the system [kW]

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Objectives computation Specific Cost: Post combustion unit investment cost Fuel cell investment cost Fuel processing unit investment cost 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, State variables Units sizing Cost computation

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Decision variables Fixed methane flow rate Selection T FP Steam / carbon Air enrichment Fuel Utilization Post combustion pressure Oxygen to carbon

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Results: Pareto curve

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Pareto analysis ATR SMR

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Pareto analysis Steam to carbon ratio of the optimal points

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Pareto analysis Fuel processing temperature of the optimal points

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Pareto analysis Post combustion pressure of the optimal points

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Pareto analysis Fuel utilization of the optimal points

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Results: Cost analysis Specific cost by equipment [$/kW]

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Two level optimization: –Energy Integration –Thermo-economic Optimization 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 Summary Complete tool for help to system design

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 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 I´ll be glad to answer your Qestions !

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Pareto analysis

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Pareto analysis

F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March Power analysis Fraction of electrical power produced by each subsystem