The Advantages of Non-Flow-Through Fuel Cell Power Systems ...€¦ · 21 psia +/- 2 100 - 275 psia...
Transcript of The Advantages of Non-Flow-Through Fuel Cell Power Systems ...€¦ · 21 psia +/- 2 100 - 275 psia...
The Advantages of Non-Flow-Through Fuel Cell Power Systems for Aerospace Applications
NASA has been developing proton-exchange-membrane (PEM) fuel cell power systems for the past decade, as an upgraded technology to the alkaline fuel cells which presently provide power for the Shuttle Orbiter. All fuel cell power systems consist of one or more fuel cell stacks in combination with appropriate balance-of-plant hardware. Traditional PEM fuel cells are characterized as flow-through, in which recirculating reactant streams remove product water from the fuel cell stack. NASA recently embarked on the development of non-flow-through fuel cell systems, in which reactants are dead-ended into the fuel cell stack and product water is removed by internal wicks. This simplifies the fuel cell power system by eliminating the need for pumps to provide reactant circulation, and mechanical water separators to remove the product water from the recirculating reactant streams. By eliminating these mechanical components, the resulting fuel cell power system has lower mass, volume, and parasitic power requirements, along with higher reliability and longer life. These improved non-flow-through fuel cell power systems therefore offer significant advantages for many aerospace applications.
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The Advantages of Non-Flow-Through Fuel Cell Power Systems for Aerospace Applications
Mark Hoberecht & Kenneth Burke
National Aeronautics and Space AdministrationGlenn Research Center
Ian Jakupca
QinetiQ North America
March 1, 2011Next Generation Suborbital Researchers ConferenceOrlando, FL
NASA PEMFC Development History
• NASA initiated PEMFC studies during Shuttle upgrade program in late 1990’s at JSC• High DDT&E costs prevented switch from alkaline to PEM, in spite of several technical advantages
• RLV program funded initial development of PEMFC technology (2001)• A single vendor selected
• RLV transitioned into NGLT, SLI, and eventually ETDP programs (2001-2007)• Two vendors selected for Breadboard development• One vendor down-selected for Engineering Model development• Disadvantages of flow-through PEMFC systems became evident during testing of Engineering Model; balance-of-plant experienced multiple failures (rotating mechanical components)
• Began investigation of “passive” balance-of-plant concepts for flow-through technology (2005)
• Reactant pumps replaced with injectors/ejectors• Mechanical water separators replaced with membrane water separators
• In parallel, began investigation of non-flow-through technology through SBIR program (2005)
• Single vendor awarded contract
• Down-selected to non-flow-through technology over flow-through technology; initiated in-house development of balance-of-plant (2008)
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Fuel Cell Technology Development Mission Requirements Assessment
Lunar Architecture Studies identified regenerative fuel cells and rechargeable batteries as enabling technology, where enabling technologies are defined as having:
“overwhelming agreement that the program cannot proceed without them.”
Surface Systems
Surface Maintenance-free operation of regenerative fuel cells for >10,000 hours usingPower: ~2000 psi electrolyzers. Power level TBD (2 kW modules for current architecture)
Reliable, long-duration maintenance-free operation; human-safe operation; architecture compatibility; high specific-energy, high system efficiency.
Mobility Reliable, safe, secondary batteries and regenerative fuel cells in small mass andSystems: volume.
Human-safe operation; reliable, maintenance-free operation; architecture compatibility; high specific-energy.
Lander
Descent Functional primary fuel cell with 5.5 kW peak power.Stage: Human-safe reliable operation; high energy-density; architecture compatibility
(operate on residual propellants).
Shuttle “Active BOP”
Alkaline“Active BOP”
PEM
GlennResearch Center
JohnsonSpace Center
17 - 20 psia
PTTP
PTPT5
PT6
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TP6TP PT
PT3TP3TP PT
M1RV1
COOLANT
OXYGEN PURGE 3/4" **AS4395-12 Male flarefitting
OXYGEN* Supply to 3/8" **AS4395-06 Male flare fitting
PR1
PR2
FC1
WT1
PTPT1
PT2
PRODUCT WATER 1/4"AS4395-04 Male flare fitting
19 psia +/- 3CATHODE
HYDROGEN* Supply to 1/4" **AS4395-04 Male flare fitting
TPTP1
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ANODE
FACILITYPOWERPLANTT1
Accumulatorwith bellows
MV1
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HYDROGEN PURGE 1/2" **AS4395-08 Male flare fitting
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TP PT
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100 - 275 psiaTemp > 10 C
21 psia +/- 2
19 psia +/- 3
19 psia +/- 3
21 psia +/- 3
17 psia
21 psia +/- 2 100 - 275 psiaTemp > 10 C
17 - 20 psia50 - 56 deg C
17 -20 psia44 - 50 deg C
3/4" Primary Coolant Loop
30 psia +/- 2
32 psia +/- 2
45 psia +/- 2
PT
PTPT7
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Secondary Coolant LoopHX1
PRIMARY COOLANT INLET 3/4"AS4395-12 Male flare fitting
PRIMARY COOLANT OUTLET 3/4"AS4395-12 Male flare fitting
25 +/- 10 deg C
50 - 56 deg C
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17 - 20 psiaPRODUCT WATER 1/4"AS4395-04 Male flare fitting
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Hydrogen pressure manifold
Oxygen pressure manifold
Flow-Through Flow-Through
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“Passive BOP”PEM
Flow-Through
“Passive BOP”PEM
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injector/ejector
passive water separator
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Non-Flow-Through
Active Mechanical Component(pump, active water separator)= Passive Mechanical Component
(injector/ejector, passive water separator)=
Fuel Cell Technology Progression to Simpler Balance-of-Plant
Active coolant pump (coolant loop not shown)
Active coolant pump
(coolant loop not shown)
Flow-Through
Fuel Cell Technical Approach: “Non-Flow-Through” Water Management
Non-Flow-Through PEMFC technology characterized by dead-ended reactants and internal product water removal• Tank pressure drives reactant feed; no recirculation • Water separation occurs through internal cell wicking
Develop “non-flow-through” proton exchange membrane fuel cell technology to improve system-level mass, volume, reliability, and parasitic power
Flow-Through components eliminated in Non-Flow-Through system include:• Pumps or injectors/ejectors for recirculation • Motorized or passive external water separators
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gas recirculation pump
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System-Level Comparison of Flow-Through vs. Non-Flow-Through PEMFC Technology
Design Parameter Flow-Through Non-Flow-Through
Efficiency − −Mass
Volume
Parasitic Power
Reliability
Reactant Utilization
EquivalentReactant Storage
“Depth-of-Discharge”
Life
Cost
TRL
1-kW Flow-Through PEMFC System
3-kW Non-Flow-Through PEMFC System
(mock-up)
Non-flow-through PEMFC system has a substantially simplerbalance-of-plant than conventional flow-through PEMFC system.
This offers significant advantages.
Non-Flow-Through PEMFC Technology Vendor Comparison
• Infinity selected as “baseline” non-flow-through PEMFC vendor very early in program
• Awarded very first non-flow-through Phase I SBIR (2005)• Demonstrated development success led to Phase II and Phase III contract awards• Very advanced and robust cell technology• Excellent cell performance• Superior water removal• Knowledgeable team with extensive flight hardware development experience (Shuttle, Apollo, Gemini)
• Other subsequent SBIR and IPP vendors competed for “alternate” role
• ElectroChem, Proton, and Teledyne stacks all experienced water management issues• ElectroChem & Teledyne most promising “alternate” technologies
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Non-Flow-Through PEMFC System
External System
Reactant Supply
Mechanicals
Fuel Cell Stack
ElectronicsModule
PowerConditioningand Battery
Hydrogen GasOxygen Gas
Balance of Plant (BoP)
Communication BusSensor/ActuatorPower
HeatWater/Coolant
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FuelCell Stack
H2 Vent
S
S
S
P
T
PP
T
PP
S
P
P
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S
H2O Fill
O2 Vent
O2 Supply
H2O Drain
H2 Supply
Non-Flow-Through PEMFC System Schematic
P
P
P
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Small Fuel Cell System Balance-of-PlantComponents for Fuel Cells
• Integrated balance-of-plant demonstrated in conjunction with the laboratory scale fuel cell stacks
• During this testing, the balance-of-plant ran on a battery source consuming only 10 watts of parasitic power to operate the fuel cell system
• A full-scale (3-kw fuel cell system) balance-of-plant will likely operate on only 50 watts or less of parasitic power (same number of components, but some components larger)
Solenoid Valves Pressure
Transducers
PressureRegulator
Pressure Transducers
PressureRegulator
Pressure Accumulator
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FUEL CELL STACK
Actuators• Solenoids
• Pump(s) (TBD)
Sensors• Pressure
• Temperature
• Voltage
• Current
Control, Monitor & Communications
• Micro Processor
• Data Acquisition and Control Signals
• Multiplexers
• Amplification
• A/D D/A Conversion
• Communication Port(s)
ExternalComputer
Power Management (includes battery for startup)
• DC / DC Converters (3V,5V, 6V,12V)
• Power MOSFETs for switching of internal loads
• Battery Power at start-up
• Transition of power from battery to fuel cell for internal loads
• Battery Recharging
• Constant current source for optional electrolytic startup of fuel cell
• Circuit Over-Current Protection
External Power Interface
Unregulated Power
Regulated Power
Digital CommunicationSensor Outputs
Ext. Spacecraft Subsystems
Balance - of – Plant Electronics
Non-Flow-Through PEMFC Electronic Interface
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Future Activities – Flight Hardware
• Passive Water Control• Advanced Thermal Control Systems• Non-Flow-Through Reactants• Integrated Fluidics
– Endplate manifold houses all process fluid plumbing and fluidic measurement and control components
• Thermally compensated bolts eliminating Belleville washer stack-up
• Power – Nominal output power: 3 kWe
– Peak output power: 6 kWe
– Parasitic Power: 15 W to 35 W• Envelope
– Length: 60 cm (24 inches)– Width: 39.4 cm (15.5 inches)– Height: 25 cm (9.8 inches)– Weight: TBD (estimated 75 kg)