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© Fraunhofer IKTS System Design and Process Layout for a SOFC µCHP-Unit with Reduced Operating Temperatures Thomas Pfeifer, Laura Nousch, Wieland Beckert.

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Presentation on theme: "© Fraunhofer IKTS System Design and Process Layout for a SOFC µCHP-Unit with Reduced Operating Temperatures Thomas Pfeifer, Laura Nousch, Wieland Beckert."— Presentation transcript:

1 © Fraunhofer IKTS System Design and Process Layout for a SOFC µCHP-Unit with Reduced Operating Temperatures Thomas Pfeifer, Laura Nousch, Wieland Beckert Fraunhofer IKTS, Dresden, Germany European Fuel Cell 2001 – Piero Lunghi Conference & Exhibition Rome, December 14-16, 2011

2 © Fraunhofer IKTS- 1 - The Fraunhofer-Gesellschaft in Germany 60 Institutes more than 18,000 employees Fraunhofer-Headquarters in Munich Fraunhofer-Locations in Germany

3 © Fraunhofer IKTS- 2 - Profile of the Fraunhofer IKTS Regular staff:400 + student workers Total budget (2010): 31,7 m (w/o invest) Industrial revenues: 38.9 % Public research revenues: 46.6 % Core financing: 14.5 % Research facilities:140 laboratories and pilot plants of approx m² DresdenHermsdorf (since 01/2010)

4 © Fraunhofer IKTS- 3 - Ceramic Multilayer Bundled Microtubes (ASC) Planar Mini-Stack (ESC) Integrated Stack-Module Integrated HotBox-Modules 1 W Fuel Cell System Development Projects at the Fraunhofer IKTS H 2 PEFC 10 kW1 kW100 W10 W Butane SOFC LPG SOFC Natural Gas SOFC Biogas SOFC

5 © Fraunhofer IKTS- 4 - Multi-Level Simulation Supported System Development Core Modules: sofc.dll prop.dll equi.dll Development Tools: MS Excel, VBA, C++, Matlab / Simulink, Modelica / SimulationX FEA: COMSOL Multiphysics, FlexPDE, ANSYS CFD: Fluent, Ansys CFX IKTS contributions to LOTUS

6 © Fraunhofer IKTS- 5 - Preliminary 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.

7 © Fraunhofer IKTS- 6 - Preliminary LOTUS Design Studies Stack Performance Estimation at 650 °C Available Cell Technology: ASC x 50 cm², CH 4 -SR Reformate 650 W 70% FU U Cell = 0.7 V Expected Development: ASC % 66 x 80 cm², CH 4 -SR Reformate 1550 W 70% FU U Cell = 0.7 V SOFCPower ASC % enables LOTUS-development SOFCPower ASC % enables LOTUS-development

8 © Fraunhofer IKTS- 7 - Preliminary LOTUS Design Studies Pre-Evaluation of Fuel Reforming Options Stack-Internal Reforming (IR) Pre-Reforming Fuel H2OH2O H2OH2O IR-SOFC Fuel Air POX SOFC Heat Fuel H2OH2O H2OH2O SR SOFC Heat Fuel H2OH2O H2OH2O ATR SOFC Air Steam Refor- ming (SR) Autothermal Reforming (ATR) Partial Oxi- dation (POX) 650 °C POX ATR SR 800 °C POX ATR SR

9 © Fraunhofer IKTS- 8 - Preliminary LOTUS Design Studies Comparison of Basic System Concepts η el η th No feasible technology for IR with anode off-gas recirculation is available. SR shows electr. efficiency according to LOTUS development goals. ATR shows higher total efficiency. RAPH is beneficial for electrical efficiency. POX is not an option at 650 °C due to the risk of reactor overheating at soot-preventing air ratios. loss Steam Reforming (SR) is the best option for LOTUS-development Steam Reforming (SR) is the best option for LOTUS-development

10 © Fraunhofer IKTS- 9 - Boundary Conditions for the LOTUS System Design Stack temperature predetermines reforming temperature 650 °C. Soot-free reformer operation requires S/C ~ In practical µCHP-operation a lower system S/C is essential. For start-up and shut-down of ASC a reducing atmosphere > 300 °C is required. Controlled stack-internal reforming ( IR ) is beneficial for system efficiency. 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. LOTUS system design is governed by the fuel reforming concept and its process integration.

11 © Fraunhofer IKTS LOTUS System Design Process Flow Diagram (PFD) Implementation of the LOTUS Fuel Reforming Concept Downscaled steam reformer (SR) SR directly heated by burner exhaust (AB or SB) Fuel bypass (FBP) for controlled stack- internal reforming Optional use of oxidative steam reforming

12 © Fraunhofer IKTS LOTUS System Design Balance Sheet & Process Layout Calculations Interactive Process Calculation Sheets in Microsoft Excel Added Functionality through Visual Basic UDFs and Macros Parameterized SOFC Stack Model: sofc.dll Thermophysical Properties: prop.dll Chemical Equilibrium Calculations: equi.dll

13 © Fraunhofer IKTS LOTUS System Design System Performance Estimation

14 © Fraunhofer IKTS LOTUS Parameter Studies Efficiencies at Varying Fuel Bypass Ratio Parameter variation: Bypass Ratio ( ) = System-S/C = Effect of : η Sys Effect of System-S/C : η Sys Independent: η el ~ constant

15 © Fraunhofer IKTS LOTUS Parameter Studies Reformate Quality at Varying Fuel Bypass Ratio FBP-Implications: Option for controlled stack- internal reforming: x CH4 = Vol.-% Anode inlet temp. decreases due to mixing and chemical equilibrium. Recommended Fuel Bypass Ratio: = 0.5 at S/C tot = 1.5 (S/C ref = 3)

16 © Fraunhofer IKTS LOTUS Parameter Studies Process Control Options SRATR Efficiency-Shift by oxidative steam reforming: Reduced reformer heat demand due to partial oxidation of fuel. Effect of λ REF : η th, η Sys, η el At λ REF > 0.325: ATR-point with steam supply, further increase of λ REF only with liquid H 2 O.

17 © Fraunhofer IKTS LOTUS Parameter Studies Process Control Options -Control by oxidative steam reforming: Effects of λ REF : CHP-heat production Reformer heat demand 0 σ -Shift: Cell voltage increases due to changed fuel composition. σ

18 © Fraunhofer IKTS Conclusions & Outlook Modelling and Simulation Tasks in the LOTUS-Project Deliv.DescriptionStatus D 3.1 System Requirements Document as developed during a joint SRD-Workshop, hosted by IKTS finished 06/2011 D 3.2 Prerequisites & Parameter Studies for principal System Design Decisions, presented and discussed at a joint Workshop (MS4) finished 09/2011 D 3.3 Steady State Process Layout with Mass Flow & Energy Balance Sheet (Excel) based on an agreed Process Flow Diagram (PFD) finished 09/2011 D 3.4 Dynamic Process Model in Modelica / SimulationX, first used for detailed recalculation of steady state operation at rated conditions starting 02/1012 D 3.5 Finite State Machine in Modelica StateChart Designer (MiL) for Control Logic Development and Virtual System Start-up t.b.d.

19 © Fraunhofer IKTS Thanks for your attention! Thomas Pfeifer Fraunhofer Institute for Ceramic Technologies and Systems IKTS Winterbergstraße 28, Dresden, Germany


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