Thermo-economic modelling and optimization of fuel cell systems

1. 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:francois.marechal@epfl.ch

2. 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

3. 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

4. Chemical process modelling tool • Thermodynamic calculations • Block system equation solver • Modular graphical interface • VALI-BELSIM, Belgium • www.belsim.com Methodology Process flow model VALI F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

5. 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 Methodology Energy integration EASY Process flow model VALI F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

6. 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 Optimisation MOO Process flow model VALI Energy integration EASY F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

7. Methodology Optimisation MOO Decision variables Performances Equipment rating and costing State variables State variables Process flow model VALI Energy integration EASY State variables Heat exchange requirements F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

8. Process flow model VALI F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

9. Fuel processing Post combustion Fuel Cell Energy flow model • PEM system modelling (VALI): define the process steps Heat exchange requirements To energy integration (EASY) F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

10. Fuel processing Fuel processing Cleaning Energy flow model of subsystems Post combustion Fuel Cell Post processing F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

11. Fuel processing Cleaning Subsystems superstructure Post processing Process Alternatives (energy flow level (VALI)) F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

12. Energy flow model Utility F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

13. Energy integration EASY F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

14. T H Energy integration • Pinch technology, composite curves Minimum of Energy Required T T5 Cp=b T4 T3 Hot composite curve Cp=a Cp=c Cold composite curve T2 T1 Minimum of Energy to Evacuate H Possible heat recovery by heat exchange Hot Utility: supplies energy to the system Hot streams (Tin > Tou) = heat available Cold streams (Tin < Tou) = heat required Cold Utility: removes energy from the system F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

15. 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

16. Methodology Optimisation MOO F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

17. 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

18. Objectives: thermo-economic • Two objectives: Maximum Efficiency Minimum Specific Cost F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

19. Methodology Equipment rating and costing F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

20. Fuel Cell power [kW] Resulting power from turbines and compressors [kW] Electrical power cost of the oxygen production [kW] Objectives computation Efficiency: Power balance on the system [kW] Methane entering the system [kmol/s] Methane lower heating value [kJ/kmol] F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

21. Objectives computation Fuel processing unit investment cost Specific Cost: Fuel cell investment cost Post combustion unit investment cost Cost computation State variables Units sizing 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

22. Decision variables Selection Fixed methane flow rate TFP Steam / carbon Oxygen to carbon Air enrichment Post combustion pressure Fuel Utilization F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

23. Results: Pareto curve F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

24. Pareto analysis SMR ATR F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

25. Pareto analysis Steam to carbon ratio of the optimal points F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

26. Pareto analysis Fuel processing temperature of the optimal points F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

27. Pareto analysis Post combustion pressure of the optimal points F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

28. Pareto analysis Fuel utilization of the optimal points F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

29. Results: Cost analysis Specific cost by equipment [$/kW] 1200 10 9 8 6 7 5 2 1 800 4 3 400 1 2 3 4 5 6 7 8 9 10 F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

30. 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

31. Aknowledgment • The authors thank the Swiss Federal Office of Enegy forthe financial support of the present project F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

32. I´ll be glad to answer your Qestions ! F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

33. Pareto analysis F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

34. Pareto analysis F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004

35. Power analysis Fraction of electrical power produced by each subsystem F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004