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The Fraunhofer-Gesellschaft in Germany

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Presentation on theme: "The Fraunhofer-Gesellschaft in Germany"— Presentation transcript:

0 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

1 The Fraunhofer-Gesellschaft in Germany
München Holzkirchen Freiburg Efringen- Kirchen Freising Stuttgart Pfinztal Karlsruhe Saarbrücken St. Ingbert Kaiserslautern Darmstadt Würzburg Erlangen Nürnberg Ilmenau Schkopau Teltow Oberhausen Duisburg Euskirchen Aachen St. Augustin Schmallenberg Dortmund Potsdam Berlin Rostock Lübeck Itzehoe Braunschweig Hannover Bremen Bremerhaven Jena Leipzig Chemnitz Dresden Cottbus Magdeburg Halle Fürth Wachtberg Ettlingen Kandern Oldenburg Freiberg Paderborn Kassel Gießen Erfurt Augsburg Oberpfaffenhofen Garching Straubing Bayreuth Bronnbach Prien Hamburg Leuna 60 Institutes more than 18,000 employees Zentrale/P2/Januar 2011 dargestellt sind: Institute, Teilinstitute, Institutsteile, Einrichtungen, Arbeitsgruppen, Anwendungszentren  Fraunhofer-Headquarters in Munich Fraunhofer-Locations  in Germany

2 Profile of the Fraunhofer IKTS
Regular staff: student workers Total budget (2010): € 31,7 m (w/o invest) Industrial revenues: % Public research revenues: % Core financing: % Research facilities: 140 laboratories and pilot plants of approx m² Dresden Hermsdorf (since 01/2010)

3 Fuel Cell System Development Projects at the Fraunhofer IKTS
1 W 10 W 100 W 1 kW 10 kW H2 PEFC Butane SOFC LPG SOFC Natural Gas SOFC Biogas SOFC Ceramic Multilayer Bundled Microtubes (ASC) Planar Mini-Stack (ESC) Integrated Stack-Module Integrated HotBox-Modules

4 Multi-Level Simulation Supported System Development
IKTS contributions to LOTUS 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

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.

6 Preliminary LOTUS Design Studies Stack Performance Estimation at 650 °C
SOFCPower ASC700+20% enables LOTUS-development Available Cell Technology: ASC x 50 cm², CH4-SR Reformate Expected Development: ASC700+20% 66 x 80 cm², CH4-SR Reformate 650 70% FU UCell = 0.7 V % FU UCell = 0.7 V

7 Preliminary LOTUS Design Studies Pre-Evaluation of Fuel Reforming Options
Stack-Internal Reforming (IR) Pre-Reforming Fuel H2O IR-SOFC 650 °C POX ATR SR 800 °C POX ATR SR Steam Refor- ming (SR) Fuel H2O SR SOFC Heat Autothermal Reforming (ATR) Fuel H2O ATR SOFC Air Partial Oxi- dation (POX) Fuel Air POX SOFC Heat

8 Preliminary LOTUS Design Studies Comparison of Basic System Concepts
Steam Reforming (SR) is the best option for LOTUS-development 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 ηth ηel

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.

10 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 Air Fuel Exhaust SOFC Stack APH Air Pre-Heater AB After- burner SR Steam Reformer CHP-Hx Heat Exchanger Water EVP Evaporator Electricity = ~ SB Start-up - Burner FBP Fuel Bypass

11 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

12 LOTUS System Design System Performance Estimation

13 LOTUS Parameter Studies Efficiencies at Varying Fuel Bypass Ratio
Parameter variation: Bypass Ratio (t) = System-S/C = Effect of t : ηSys Effect of System-S/C : ηSys  Independent: ηel ~ constant

14 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: t = 0.5 at S/Ctot = 1.5 (S/Cref = 3)

15 LOTUS Parameter Studies Process Control Options
↓ SR ATR ↓ Efficiency-Shift by oxidative steam reforming: Reduced reformer heat demand due to partial oxidation of fuel. Effect of λREF : ηth , ηSys , ηel  At λREF > 0.325: ATR-point with steam supply, further increase of λREF only with liquid H2O. at the expenses of electrical efficiency

16 LOTUS Parameter Studies Process Control Options
s-Control by oxidative steam reforming: Effects of λREF : CHP-heat production  Reformer heat demand  0 σ-Shift: 2.2  1 Cell voltage increases due to changed fuel composition. σ

17 Conclusions & Outlook Modelling and Simulation Tasks in the LOTUS-Project
Deliv. Description Status 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.

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

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