Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016

Distribution Statement A - Approved for public release; distribution is unlimited
Fuel Cells as Power Sources
for UUVs
Dr. John R. Izzo
Naval Undersea Warfare Center
Energy and Propulsion Branch
Joint Safety and Environmental Professional Development Symposium, March 16, 2016

Outline
 Introduction to Batteries and Fuel Cells
 Proton Exchange Membrane and Solid Oxide Fuel Cells
 Fuel and Oxidizer Options
 Fuel Cell Fundamentals
 ONR Fuel Cell Systems for UUVs
2

Introduction
 There is a naval need for an air-independent advanced electric power source
with high energy storage for unmanned undersea vehicles (UUV).
 Current battery systems can not meet mission requirements.
 Proton exchange membrane fuel cells (PEMFC) and solid oxide fuel cells
(SOFC) are being investigated due to higher efficiencies and energy densities.
 System safety must meet requirements for approval.
3

Distribution Statement A - Approved for public release; distribution is unlimited 4
Unmmaned Undersea Vehicles (UUVs)
4Distribution Statement A - Approved for public release; distribution is unlimited

General Power/ Energy Devices
Combustion Engine:
 Energy Conversion device, will continue to run as long as fuel and oxidant
are supplied, however
 Overall efficiency limited by Carnot Cycle
  max= 1- T Cold/ T Hot
Fuel Cell:
 Energy Conversion devices- can continue to run as long as fuel and oxidant
are supplied
 Do not operate on a thermal cycle (Not limited by Carnot Cycle efficiency)
Battery:
 Energy Storage device, limited by reactants present at beginning of
discharge,
 non- rechargeable (Primary) or rechargeable (secondary)
5

Energy Conversion Comparisons
ChemicalFuel Cell: Electrical
ChemicalBattery: Electrical
ChemicalThermal Engine: Heat Mechanical Electrical
Chemical Electrical
ChemicalBattery: Electrical
ChemicalThermal Engine: Heat Mechanical
Mechanical
Mechanical
Electrical
Mechanical
Fuel Cell:

0.1
1
10
100
1000
10000
100000
10 100 1000
SpecificPower(W/kg)
Specific Energy (Wh/kg)
SOFC Upper Bound
SOFC Lower Bound
0.1 h
1 h
10 h
100 h
TNT
Ragone Chart
Ni-
MH
Li-
SOCL2
Pb-
Acid
Zn-
AgO
Li-
SFC
7

Battery
• Electrochemical storage device
• Reactants stored internally
• Fixed amount of reactants
• Rechargeable (if secondary)
• Scale up requires design change
Fuel Cell
• Electrochemical conversion device
• Reactants stored externally
• Re-fuelable “gas and go”
• Easily scaled up (individual cells)
• Batteries and fuel both directly produce electricity efficiently
• Fuel cells have higher volumetric and gravimetric energy metrics
Battery vs. Fuel Cell

Type of System
Specific
Energy
(Wh/kg)
Energy
Density
(Wh/L)
Max Mission
at 2.5 kW*
(hr)
Number of
cycles
NiCd 30 75 3 1500
Lead Acid 30 65-95 3 > 300
NiMH 95 330 8 500
AgO-Zn 110 240 9 15
Sec. Li Ion 130 325 11 ~ 2000
Alkaline 140 360 12 1
Li Polymer 210 330 18 > 600
Li-SOCl2 ~ 450 900-1000 35-38 1
* based on energy section having a volume of 189 L and mass of 209 kg
Batteries

Fuel Cell Type Electrolyte Temperature (C)
Alkaline potassium hydroxide 50-90
Proton exchange membrane
(PEM)
polymer 50-125
Direct methanol methanol 50-120
Phosphoric acid ortho-phosphoric acid 190-210
Molten carbonate lithium/potassium carbonate
mixture
600-650
Solid oxide fuel cell
(SOFC)
stabilized zirconia 800-1000
System Specific Energy
(Wh/kg)
Energy Density
(Wh/L)
Max Mission at 2.5 kW
(hr)
Number of
cycles
SOFC (C12H26+LOX) > 300 > 300 30-40 ~ 30
PEM (NaBH4+LOX) > 300 > 300 21 ~ 150
Fuel Cells

Types of Fuel Cells
Hydrogen-Oxygen FC Reaction:
2 H2 + O2  2 H2O
11
11

Fuel Cell Reactions
12

PEM Fuel Cell
 The PEM fuel cell consists of a
membrane electrode assembly
(MEA), which is placed between two
flow-field plates.
 The MEA consists of:
 Anode and the cathode, each coated
with a thin catalyst layer and
separated by polymer membrane
electrolyte (Nafion).
13

Solid Oxide Fuel Cell (SOFC)
Type Material Charge Carrier
electronic metal electrons
ionic insulator ions
electronic semiconductor electrons / holes
anode (500μ)
cathode(50μ)
electrolyte (10μ)
Electrolyte properties
• High electrical resistance (poor electronic
conductivity; electrically insulating)
• Functions as:
- impermeable diffusion barrier between the
fuel and oxidizer; it prevents mixing that
would otherwise result in combustion
- ionic conductor for the transport of oxide ions
(O-2) from the cathode to the anode.
• Must operate at sufficiently high temperature to
facilitate oxide ion mobility (YSZ operates in the
range of 750º- 1000ºC)
Reduction
½ O2 + 2e- O=H2 2H+ + 2e-
Oxidation
oxygen
water
anode cathodeelectrolyte
load
hydrogen
e-
e-
e-
e-
=
=
=
=
=
=
=
=
=
oxide ions

PEM - SOFC Comparison
 PEM (80 °C)
 Fast start-up
 Load following
 Low fuel impurity tolerance
 SOFC (600-1000 °C)
 Tolerance to typical catalyst poisons (CO).
 Fuel flexibility: hydrocarbon and liquid logistics fuels.
 Ceramic materials (fragile), sealing
 Challenges: Cost, Performance and Durability.

Fuel Cell Stack
16
 Multiple cells are connected in series to obtain a higher system voltage.
 Stack power is determined by the number and size of cells in the stack.
 Complexity of fuel cell stacks increases since reactant delivery, cooling,
and sealing must be managed for multiple cells.

Fuel / Oxidizers
Fuel
 Hydrogen
 Compressed gas
 Cryogenic liquid
 Metal Hydrides
 Hydrocarbons
 Light (C1 - C4)
 Methanol
 Liquid (JP-8, diesel, Fischer-
Tropsh)
 High energy density
 Hydrogen-containing compounds
 Chemical hydrides
 LiAlH4
 NaBH4
Oxidizer
 Air (terrestrial applications)
 Oxygen
 compressed gas
 cryogenic liquid
 Oxygen-containing compounds
 KClO4 (perchlorate candle)
 MnO2
 KO2
 Hydrogen peroxide (H2O2)

High Pressure Gaseous Reactant Storage
Higher Pressure:
• Compression Diminishing
Returns
• “Real Gas Effects”
• Composite Pressure Vessels
• Fracture Mechanics
• Design, Certification,
Testing
10,000 psi
5000 psi
ASME Pressure Vessels

Cryogenic Liquid Reactant Storage
 Higher storage density vs. compressed gas
 Double walled vessels
 Inner vessel contains cryogenic liquid reactant
 Outer vessel provides vacuum insulation
19
Potenial Issues:
• Temperature
• Cost
• Complexity
• Safety
• Training
• Certification
• Deployment
• Shock
• Vibration
• Implodable Volumes

OCV (open circuit voltage) - cell or stack voltage with no external load connected (no current
draw)
Nernst Equation - allows calculation of the reversible cell voltage of an electrochemical system
that would exist at a given temperature and pressure
E = reversible cell voltage T = absolute temperature
E0 = standard cell voltage n = number of electrons transferred
R = gas constant F = Faraday’s constant 96,500 C/mol
p = partial gas pressure
Fuel Utilization (Uf) - mass of fuel reacted in cell / mass of fuel input to cell
Efficiency () - output energy / total input energy
TBP (triple phase boundary) - region where reactant (fuel or air), electrolyte and electrode
meet (SOFC example shown).
Fuel Cell Terminology

Single Cell Theoretical Voltage
Fuel Cell Handbook, 7th Ed., DOE
E = -ΔG / nF
21

Fuel Cell Handbook, 7th Ed., DOE
Plot of voltage against current density (or current)
Nernst Potential
Operating
Range
Ohmic Polarization
(Resistance Loss)
Concentration Polarization
(Mass Transport Loss)
Theoretical Voltage
Activation Polarization
(Reaction Rate Loss)
Polarization Curve
 Activation Polarization - loss associated with the activation barrier that a reactant
species must overcome
 Ohmic polarization - loss attributed to electrical resistance of components and ionic
conductivity of the electrolyte
 Concentration polarization - loss due to mass transport limitation of reactant gases
through porous electrodes.
22

Activation Polarization - loss associated with the activation barrier that a reactant
species must overcome
- optimize microstructure
- increase length of TBP (electrochemically active length in the cell)
Ohmic polarization - loss attributed to electrical resistance of components and ionic
conductivity of the electrolyte
- operate at higher temperature
- doping (control defect concentration)
- decrease thickness of electrolyte layer
Concentration polarization - loss due to mass transport limitation of reactant gases
through porous electrodes
- reduce reactant utilization
- increase porosity of electrode
Reducing Voltage Losses
23

ONR BAA 11-016
Long Endurance Undersea Vehicle Propulsion FNC
Threshold and Objective Metrics: Phase I
• THRESHOLD : Phase I Base at a MINIMUM TRL-4 in bench-top
demo
• Subscale of OBJECTIVE profile at lower power/energy with relevant
transients
• OBJECTIVE : Phase II at TRL-6 in a land-based UUV energy
section demo
• Hardware and associated SOPs, drawings, etc will transition
Threshold Objective
Nominal Power Density (W/l) 10 20
Energy Section Diameter
21” OD
(18.5” ID)
21” OD
(18.5” ID)
Energy Section Length 76.2 cm (30’’) 76.2 cm (30’’)
Energy Volume (liter) 132 132
Energy Mass (kg) w/o hull & bulk 132 (neutrally buoyant) 132 (neutrally buoyant)
Energy (kWh) 42 68
Duration (hrs) >30 >30
24

21-Inch LEUVP Propulsion FNC
ONR BAA 11-016
Ongoing P-II Objectives
 TRL-4 Test Program of a Compressed Hydrogen Storage System
 Preliminary, Critical Design Reviews of a TRL-6 Energy Storage System
 Safety Analyses Including:
 Subsystem Hazard Analysis (SHA) & Operating and Support Hazard Analysis (O&SHA)
 Health Hazard Assessment Report (HHAR)
 Operating Procedures for Hazardous Materials (MSDS)
 Test and Delivery of a Full-Scale TRL-6 Energy System Integrated into a GFE-furnished
Energy Section Hull
25

Threshold Metrics Objective Metrics
Nominal Power Density
(Watts/Liter)
0.4 0.6
Energy Section Diameter
44” OD (42” ID) square
w/rounded corners
44” OD (42” ID) square
w/rounded corners
Energy Section Length 304.8 cm (120”) 304.8 cm (120”)
Energy System Volume (L) 3454 (neutrally buoyant) 3454 (neutrally buoyant)
Energy System Mass (kg)
3540 3540
Energy System Buoyancy (kg) 0 0
Energy (kWh)* 817 1800
Duration (hrs) 46 Days (1104 Hrs) 70 Days (1680 Hrs)
ONR BAA 11-028
Large Displacement UUV INP Energy Technology
Threshold and Objective Metrics
• OBJECTIVE : Phase II at TRL-6 in a land-based UUV energy
section demo
• Hardware and associated SOPs, drawings, etc will transition
• THRESHOLD : Phase I Base at a MINIMUM TRL-4 in bench-top
demo
• Subscale of OBJECTIVE profile at lower power/energy with relevant
transients
* 10% reserve has
been added to total
Energy values
26

Aluminum Power System (ALPS)
Al-H2O
Reactor
Water
Pump
Water
Bladder
Fuel
Cell
Gaseous or Liquid
Oxygen
Hydrogen
Oxygen
Water
• Aluminum fuel
– Safe, clean, non-toxic
– Easily transportable
– Stable – long shelf life
– Proven manufacturing
approach
• Refueling is simple process
– Process byproduct
(boehmite) is benign
• Hydrogen does not need to be generated
until the AUV is in operation
• Hydrogen is clean, free of contaminants
• Hydrogen is recycled via fuel cell
• Minimal external energy required
– Water pump, solenoid valves
• Simple control scheme
• Expanded CONOPS capabilities
ONR BAA 11-028
27

Summary
 PEMFC and SOFC have been identified to meet UUV requirements due to
their high efficiency and improved energy density over current battery
systems.
 Many options for reactant storage, critical for system energy.
 System safety is critical for approval.
 ONR BAA objectives to deliver TRL-6 fuel cell system for UUVs.
 For additional information please contact: Dr. John Izzo, Naval Undersea
Warfare Center Division Newport.
28

Thank you
Power & Energy Team:
 Dr. Alan Burke
 Dr. Louis Carreiro
 Dr. Joseph Fontaine
 Mr. Mark Fuller
 Dr. John Izzo
 Dr. Charles Patrissi
 Mr. Christian Schumacher
 Dr. Craig Urian

Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016

Similar to Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016 (20)

More from chrisrobschu

More from chrisrobschu (20)

Recently uploaded

Recently uploaded (20)

Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016