Presentation on theme: "The Fraunhofer-Gesellschaft in Germany"— Presentation transcript:
0System Design and Process Layout for a SOFC µCHP-Unit with Reduced Operating Temperatures Thomas Pfeifer, Laura Nousch, Wieland BeckertFraunhofer IKTS, Dresden, GermanyEuropean Fuel Cell 2001 – Piero Lunghi Conference & ExhibitionRome, December 14-16, 2011
2Profile of the Fraunhofer IKTS Regular staff: student workersTotal budget (2010): € 31,7 m (w/o invest)Industrial revenues: %Public research revenues: %Core financing: %Research facilities: 140 laboratories and pilot plants of approx m²DresdenHermsdorf (since 01/2010)
3Fuel Cell System Development Projects at the Fraunhofer IKTS 1 W10 W100 W1 kW10 kWH2PEFCButaneSOFCLPGSOFCNatural GasSOFCBiogasSOFCCeramicMultilayerBundledMicrotubes (ASC)PlanarMini-Stack (ESC)IntegratedStack-ModuleIntegratedHotBox-Modules
4Multi-Level Simulation Supported System Development IKTS contributions to LOTUSCore Modules: sofc.dll prop.dll equi.dllDevelopment Tools: MS Excel, VBA, C++, Matlab / Simulink, Modelica / SimulationXFEA: COMSOL Multiphysics, FlexPDE, ANSYSCFD: Fluent, Ansys CFX
5Preliminary 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.
6Preliminary LOTUS Design Studies Stack Performance Estimation at 650 °C SOFCPower ASC700+20%enables LOTUS-developmentAvailable Cell Technology: ASC x 50 cm², CH4-SR ReformateExpected Development: ASC700+20% 66 x 80 cm², CH4-SR Reformate650 70% FUUCell = 0.7 V% FUUCell = 0.7 V
8Preliminary LOTUS Design Studies Comparison of Basic System Concepts Steam Reforming (SR) is the bestoption for LOTUS-developmentNo 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.lossηthηel
9Boundary 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 governedby the fuel reforming concept and its process integration.
10LOTUS System Design Process Flow Diagram (PFD) Implementation of the LOTUS Fuel Reforming ConceptDownscaled steam reformer (SR)SR directly heated by burner exhaust (AB or SB)Fuel bypass (FBP) for controlled stack-internal reformingOptional use of oxidative steam reformingAirFuelExhaustSOFCStackAPHAir Pre-HeaterABAfter-burnerSRSteamReformerCHP-HxHeatExchangerWaterEVPEvaporatorElectricity=~SBStart-up-BurnerFBPFuel Bypass
11LOTUS System Design Balance Sheet & Process Layout Calculations Interactive Process Calculation Sheets in Microsoft ExcelAdded Functionality through Visual Basic UDFs and MacrosParameterized SOFC Stack Model: sofc.dllThermophysical Properties: prop.dllChemical Equilibrium Calculations: equi.dll
12LOTUS System Design System Performance Estimation
13LOTUS Parameter Studies Efficiencies at Varying Fuel Bypass Ratio Parameter variation:Bypass Ratio (t) =System-S/C =Effect of t : ηSysEffect of System-S/C : ηSys Independent: ηel ~ constant
14LOTUS 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)
15LOTUS Parameter Studies Process Control Options ↓ SRATR ↓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
16LOTUS Parameter Studies Process Control Options s-Control by oxidative steam reforming:Effects of λREF :CHP-heat production Reformer heat demand 0σ-Shift: 2.2 1Cell voltage increases due to changed fuel composition.σ
17Conclusions & Outlook Modelling and Simulation Tasks in the LOTUS-Project Deliv.DescriptionStatusD 3.1System Requirements Document as developed during a joint SRD-Workshop, hosted by IKTSfinished 06/2011D 3.2Prerequisites & Parameter Studies for principal System Design Decisions, presented and discussed at a joint Workshop (MS4)finished 09/2011D 3.3Steady State Process Layout with Mass Flow & Energy Balance Sheet (Excel) based on an agreed Process Flow Diagram (PFD)finished 09/2011D 3.4Dynamic Process Model in Modelica / SimulationX, first used for detailed recalculation of steady state operation at rated conditionsstarting 02/1012D 3.5Finite State Machine in Modelica StateChart Designer (MiL) for Control Logic Development and Virtual System Start-upt.b.d.
18Thanks for your attention! Thomas PfeiferFraunhofer Institute for Ceramic Technologies and Systems IKTS Winterbergstraße 28, Dresden, Germany