fuel cell systems analysis · • compressed hydrogen fuel • cem performance data from doe...

Fuel Cell Systems Analysis

R. Kumar, R. Ahluwalia, E. Doss, and M. KrumpeltArgonne National Laboratory

2002 Annual National Laboratory R&D MeetingDOE Fuel Cells for Transportation Program

Golden, COMay 9-10, 2002

Argonne Electrochemical Technology Program

Objectives and Approach• Objectives

Identify key design parameters and operating efficiencies

Assess design, part-load, and dynamic performance

Support DOE/FreedomCAR development efforts

• ApproachDevelop, document, and make available an efficient,versatile system design and analysis code

Develop models of different fidelity

Apply models to issues of current interest


Reviewers’ CommentsDeveloped several new component models

Fast start fuel processor initiative

Load following fuel processor

Pressurized direct H2 system on FUDS and FHDS

High temperaturemembrane systems

No cost to DOEcontractors

• Emphasize code development rather than code utilization

• Analyze cold start-up of fuel processors

• Focus on transient modeling

• Investigate effects of driving protocols on system performance

• Conduct sensitivity and trade-off analyses

• Make model available at minimum cost


Component Model Development in FY2002

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• New application package for analysis of data on catalytic reactions• Generic model for metal hydrides: kinetics with heat transfer• Desulfurization with ZnO sorbent• Auto-thermal reforming of iso-octane with ANL catalyst

Heat transfer coefficients for desuperheating & condensing sections


GCtool Simulations for Rapid-Start Fuel Processors

• Our simulations showed that for rapid startup, the catalyticreactors must be heated in parallel rather than sequentially

• Analyzed effect of start-up energy on cycle efficiency


PSAT-GCtool Integration forFuel Cell Vehicle Analysis

• PSAT and PSAT-Pro: Hybrid vehicle simulationcodes (FreedomCAR and Vehicle Systems)

“Forward” model: driver to wheelConsistent rapid control prototyping, hardware-in-the-loop and vehicle control system integration

• GCtool_ENG: Engineering models of FC systemsbased on GCtool architecture

Speed and accuracy appropriate for fast transientsComponent maps from models in GCtool or test dataTranslator to port GCtool_ENG models to MATLAB

• ApplicationsMulti-platform studyFuel Cell–Battery/Supercap hybridization


80-kW Direct Hydrogen System(for SUV Application)

• Compressed hydrogen fuel

• CEM performance data from DOE contract• Pressurized stack at 3 atm, 80oC, 0.7 cell potential

at design pointStack polarization curve from LANL and GCtool

• Anode and cathode feeds heated/cooled to 70oC, humidified to 90% RH at stack temperature

Stack coolant used for controlling anode and cathodefeed temperatures

• Fuel cell – battery hybrid on SUV platform


Water Management in Pressurized Fuel Cell Systems

• Reformed gasoline systems:Condenser needed to recover process water at all conditionsDew point is a function of ambient pressure and O2 stoichiometry

• Direct hydrogen systems:Condenser needed only at part loadWater also recovered at stack and condenser exits

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Ambient Pressure 1 atm 1 atm 0.75 atm 1 atmRelative Humidity 25% 25% 25% 100%O2 Utilization 50% 75% 50% 50%

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Condenser and Air Heater Duties in Pressurized Direct Hydrogen Systems

• For design pressure ratio of 3, condenser cooling load is highest at20% of rated flow

• Condenser duty is a strong function of cathode stoichiometry• Cathode air heater/humidifier duty is also highest at part load

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Performance of Pressurized Direct Hydrogen System

• DOE Phase I data for CEM: design pressure ratio of 3• Stack at 80oC and 0.7 V cell potential at design point• 70% efficiency for condenser and radiator fans

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System Efficiency

Solid Lines: 27oC AmbientSymbols: 47oC Ambient


Parasitic Losses in 80-kW Pressurized Direct Hydrogen System

• CEM and radiator fan account for much of the parasitic power• Auxiliary power is affected by the ambient temperature

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With Symbols: 47oCW/O Symbols: 27oC


Efficiencies With and Without Expander for 80-kW Direct Hydrogen System

• Efficiencies and power at high ambient temperature (320 K)

With GT W/O GT With GT W/O GT With GT W/O GT

Power to CEM 7.5 kW 21.2 kW 9.3 kW 28.3 kW 12.3 kW 42.4 kW

Efficiency at Rated Flows 45.6% 39.4% 44.8% 36.9% 43.5% 32.8%

Efficiency at 50% Flows 59.6% 56.3% 59.3% 54.4% 58.5% 51.7%

Stack Size 100 kg 116 kg 102 kg 123 kg 105 kg 139 kg

Condenser Heat Duty 9 kW 13 kW 21 kW

50% O2 Utilization 40% O2 Utilization 30% O2 Utilization


Dynamic Response of the Pressurized Direct Hydrogen System

• In current simulations, dynamic response is determinedby the CEM and the integral controller

• Extended period of stack operation at very low currentdensities over FUDS cycle


Temperature Response Over theFUDS Cycle

• Cold start at 300 KCondenser and radiator fans remain off over one FUDS cycle

• Warm start at 300 KRadiator fan remains off at low powerCondenser fan cycles off and on


Dynamic Efficiency on FUDS Cycle• Beside ambient temperature, pressure, and load, dynamic

efficiency depends on the control algorithm and the state of the FC system


Current and Future Work• Model validation with data from Nuvera system• Ambient pressure direct hydrogen systems• Direct hydrogen systems with physical / chemical

hydride hydrogen storage• Reformed liquid fuel systems on drive cycles• Fast-start and load-following fuel processors• High temperature membrane systems• Alternative system configurations• Detailed component models

• Interactions with A.D. Little, Nuvera, others

fuel cell systems analysis · • compressed hydrogen fuel • cem performance data from doe...

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