Download FUEL CELL

Fuel cell: from principle to
application to the electric
vehicle
Yann BULTEL, GINP
Marian Chatenet, GINP
Laurent Antoni, CEA
Jean-Paul Yonnet, CNRS
PLAN
1.
2.
3.
4.
5.
6.
7.
Fuel Cell Introduction
Fuel Cell – Principle of Operation
Fuel Cell Performances
Fuel Cell Power System
Power Fuel Cell Module Hybridizing
Safety issues
Fuel Cell Vehicle Example
1. Fuel Cell introduction
Yann Bultel
What’s a fuel cell ?

Fuel cells are electrochemical conversion systems,
which offer unique characteristics as electrical
power generation systems.
What’s a fuel cell ?
H2
Heat loss
H2Oout, O
ANODE
H2in
2
/ Air
CATHODE
O2in / Air
Electrical power
HISTRORICAL CONSIDERATION
1842: Sir William Robert Grove is known as “Father of the Fuel
Cell.”
reaction  triple contact electrolyte-reactants-catalyst
HISTRORICAL CONSIDERATION
1932: F. Bacon, Fuel Cell with an alkaline electrolyte
AFC
Years 50-60 : spatial programs (NASA)
First practical use
Gemini : 1 kW PEFC (General Electric)
Apollo : ~10 kW AFC (Pratt & Whitney)
Years 2000 : CEA
Fuel Cell Vehicle
FUEL CELL TYPES
Fuel Cell types:
 Low temperature Fuel Cells:


PEMFC: Proton Exchange Membrane Fuel Cell (ambient to 80°C);
PAFC: Phosphoric Acid Fuel Cell (PAFC) (200-250°C);

AFC: Alkaline Fuel Cell (ambient to 80°C).
 High temperature Fuel Cells:



MCFC: Molten Carbonate Fuel Cell (600 to 700°C);
SOFC: Solid Oxide Fuel Cell (800 to 1000°C).
Fuel Cell technology for HYCHAIN vehicles is based on the
PEMFC.
2. Fuel Cell – Principle of
Operation
Yann Bultel and Marian Chatenet
UNIT CELL BEHAVIOUR
Unit cells form the core of a fuel cell (case of PEMFC):

This device converts the chemical energy contained in a fuel
electrochemically into electrical energy:



Hydrogen oxidation at the anode
Oxygen reduction at the cathode
Unit Cell working behaviour
UNIT CELL BEHAVIOUR
Electrochemical Reactions (case of PEMFC):
 Hydrogen Oxidation:
2 H2 (Dihydrogen)→ 4 H+ (proton) + 4 e- (electron)
 Oxygen Reduction:
O2 (oxygen) + 4H+ (proton) + 4 e- (electron ) → 2 H2O (Water)
 Whole Reaction:
2 H2 (Dihydrogen) + O2 (oxygen) → 2 H2O (Water)
UNIT CELL COMPONENT
Unit cell is made of (case of PEMFC):


Electrolyte: polymer membrane (Nafion)
Gas Diffusion Electrode



Gas Diffusion Layer
•
Carbon cloth/paper
Active Layer
Carbon + Platinum
Unit cell components
UNIT CELL COMPONENT
Electrolyte
 Materials:


~ Polymer electrolyte;
Example: Nafion perfluorosulfonic acid PTFE
copolymer (DUPONT)
N-115/117 (130/180 µm)
 Properties:



Protons migrations from anode
to cathode;
Gas separator;
Electronic insulator.
UNIT CELL COMPONENT
Electrolyte
 Nafion
 Non F-ionomers
H
N
N
]n
[
N
H
N
UNIT CELL COMPONENT
Electrode
 Active(/Catalyst) Layer:


Materials: ~ Carbon grains supported
Platinum nanoparticles;
Electrochemical reactions (Hydrogen
oxidation and Oxygen reduction).
UNIT CELL COMPONENT
Electrode
 Active(/Catalyst) Layer:

Which electrocatalysts for the cathode ?
• Issues
O2 reduction slow and not reversible
• 4 e- reaction non quantitative (peroxides formation)
• high ORR overpotential
 high catalysts loadings required
 high cost
 catalyst utilization ?
Instability of the Pt/C particles
• Solutions
 Alloy or composites nanoparticles to improve the 4 e- pathway
 Pt-Co/C, Pt-Ni/C
 Non-platinum electrocatalysts?
UNIT CELL COMPONENT
Electrode
 Gas Diffusion Layer:



Materials: ~ Carbon cloth/paper and
Teflon;
Gas supply.
Water removal
UNIT CELL COMPONENT
MEA
AL
GDL
Electrocatalyst
Electrolyte
Carbon
Hydrophobicporosity-binding
agent (PTFE)
Substrate (C fabric)
Carbon (powder)
Hydrophobicporosity-binding
agent (PTFE)
Membrane
Ionic conducting polymer
Electronic insulator
Barrier to reagent
UNIT CELL COMPONENT
MEA
Gas Diffusion Layer (GDL)
Active Layer (AL)
Reagent feeding
Products draining
(water & reagent excess)
Current collecting
Thermal management
Mechanical support
Membrane
A & C reagent separation
Ionic transport
Electronic insulator
Mechanical support
Electrochemical reactions
+ function of the GDL
150 µm
UNIT CELL COMPONENT
External current collecting
End plate
Electrode Membrane
Assembly
Bipolar plate
UNIT CELL COMPONENT
Bipolar plate:
 Materials


Graphite
Metallic
 Properties



Electronic current collecting;
Gas distribution;
Heat management.
UNIT CELL COMPONENT
Serpentine flow field design:
Conventional (a)
and
interdigitated (b)
gas distributor of PEMFC bipolar plate
UNIT CELL COMPONENT
1. Serpentine flow field design:
l
w
d
Parameter
Values
channel width w
0.5-2.5 mm
channel depth d
0.2-2.5 mm
landing width l
0.2-2.5 mm
draft angle 
0-15°

UNIT CELL COMPONENT
Single Cell
Gas supply
Exhaust
Gas
FUEL CELL STACK
The stacking involves connecting multiple unit cells in
series via Bipolar plate to provide:


An electrical series connection between adjacent cells;
Gas barrier that separates the fuel and oxidant of adjacent
cells;


Fuel Cell Stack description
Fuel Cell Stack Principle
FUEL CELL STACK
Electric network: cells in series
n
k
U stack  U cell
k 1
e-
Ucell
Ucell
I
Ucell
n
k
Pstack  I U cell
k 1
FUEL CELL STACK
Gas supply: cells in parallel
ANODE
H2in
CATHODE
O2in / Air
3. Fuel Cell Performances
Yann Bultel
FUEL CELL PERFORMANCES
Actual Cell Potential:
 Activation-related losses (due to kinetics);
 Ohmic losses (due electrical resistance);
 Mass-transport-related losses (due to diffusion
losses);
FUEL CELL PERFORMANCES
The triple contact
Gas
diffusion
e- transfer
resistance
(activation)
H2
Ionic
resistance
H+
Polarisation curve
Er
Ei=0
ORR irreversibility
1
Cell voltage
U (V)
2
e-
3
Ohmic
resistance
1 - Activation overvoltage hact
Electrocatalysts, Sact
Current density
i (A/cm2)
2 – Ohmic drop hohm
Ions and e- resistance
(membrane, electrodes)
3 – Diffusion limitation hdif
Gas diffusion to the catalyst
FUEL CELL PERFORMANCES
Activation overpotential: Kinetic Tafel Law
Overpotential
hact
Current density
i

ln 
2.3  i0

b
Overvoltage at the
surface of an electrode




Experimental parameters
h (V)
b : Tafel constant
i0 : exchange current density
Log(i)
FUEL CELL PERFORMANCES
Activation overpotential: Kinetic Tafel Law
b : Tafel slope
Impedance study of the oxygen reduction reaction on platinum nanoparticles in
alkaline media, L. Genies, Y. Bultel, R. Faure, R. Durand, Electrochimica Acta (2003)
FUEL CELL PERFORMANCES
Internal Resistive losses
 Electronic and Ionic conductivity of materials
 Nafion: ionic = 5 S m-1 Bipolar plate: ionic = 5000 S.cm-1
Resistance of the
flow of ions
>>
Resistance of the
flow of electrons
H+
Lm
Vionic 
j  R electrolyte j
m
FUEL CELL PERFORMANCES
Mass Transport limitation:
 finite mass transport rates limit the supply of fresh
reactant;
O2
Faraday’s law:
CB
nFD
CB  CS 
i

Limiting current density jL
nFD
CB  0
iL 

Concentration overpotential: hconc
CS
AL
H2O
GDL
RT 
i


ln1 
nF  iL



FUEL CELL PERFORMANCES
Power density versus current density:
1,2
1
0,8
Y/-
U/V
0,6
0,4
P/ W cm-2
We   I U cell
0,2
0
0
0,2
0,4
0,6
0,8
-2
i / A cm
1
1,2
1,4
FUEL CELL PERFORMANCES
Heat production:
Electrical
power
  I U
W
2

Q

R
I
ohmic

Q
act  conc  h I
T S

Q reversibility 
.I
nF
Heating rate
 H r


Q

I

U

heat
cell 
 2F

e
H2 1 O2H2O
2
Hr
Maximum efficiency possible
cell
FUEL CELL PERFORMANCES
Gas feeding:
Mass transport into a cell
Gas Utilization:
 Gas consumption (H2, O2)
and water production is linked
to current the current (/density)
 Faraday’s law
Fi,react
I

nF
[mol.s-1]
Ni,react
i

nF
[mol.s-1.m-2]
FUEL CELL PERFORMANCES
Mass and Heat Balances:
 PEMFC Stack
 Mass Balance:
Fi,in  Fi,out  Ncell
I
nF
 Heat Balance:
 i c pi Tout  Tin 
Qcool  m
FUEL CELL PERFORMANCES
One species mass balance O2 or H2:
Fi,in  Fi,out  Fi,react I  Fi,out
I

nF
 Gas Utilization Rate:
Fi,react
Fi,in  Fi,out
Ui 

Fi,in
Fi,in
 Stoichiometric ratio
Fa,in
anode
Fi,in
1
St i 

Fi,react Ui
Fc,in
Sti=1 : Stoichiometric conditions
cathode
Fa,out
Fc,out
FUEL CELL PERFORMANCES
Water management:
Rate of evap/cond  Psat  PH2O 
H2O, O2, N2
Gas channel
NHelectro

2O
2 drag
2F
Cathode
H2O
i
Electro-osmotic flow
Anode
H2O, H2
Gas channel
diffusion
H2 O
N
 D H2 O
c Ha 2O  c Hc 2O
Lm
H2O Water diffusion
electro
H2 O
r
i

2F
4. Fuel Cell Power System
Laurent Antoni
FUNCTIONAL DECOMPOSITION
OF THE FUEL CELL POWER
MODULE
System analysis:

- Numerous possible technical solutions
Depends on the application




Depends on the environment




On board
Stationary
Portable
Temperature
Pressure
Pollutants…
Depends on the user need


General objective (power, durability)
Duty cycle
 Analysis / Functional Decomposition
FUNCTIONAL DECOMPOSITION
OF THE FUEL CELL POWER
MODULE
FUNCTIONAL DECOMPOSITION
OF THE FUEL CELL POWER
MODULE
AUXILIAIRIES
BATTERIES
BUS
FUEL
TANK
CODITIONNING
INLET/OUTLET
CATHODE
FUEL
CELL
CODITIONNING
INLET/OUTLET
ANODE
COOLING : WATER MANAGEMENT
SUPERVISOR
EXTERNAL
ENVIRONNMENT
VEHICLE
COOLING
EXTERNAL
ENVIRONNMENT
ELECTRICAL CONVERTORS
Example of cathode
inlet/outlet subsystem
COOLING /
WATER MANAGEMENT
EXTERNAL
ENVIRONMENT
EXPANSION
TURBINE
SEPARATOR /
CONDENSER
CATHODE
FILTER
COMPRESSOR
HUMDIFIER
SUPERVISOR

Highest complexity



Recovery of mechanical energy from compression
Management of the liquid water from humidification
« High pressure » operation
Anode inlet/outlet
Influence of the fuel choice
On the FC system architecture

On-board molecular hydrogen
 « dead-end » architecture
 Recirculation circuit

Hydrocarbon reforming
 Steam Reforming or SR, which is endothermic and leads to the
best efficiencies but consumes water)
 Partial Oxidation or POX, which is exothermic and is appropriate for
heavy hydrocarbons,
 AutoThermal Reforming or ATR, a combination of both, facilitating
the thermal management of the steam-reforming unit
Impact on the power module
architecture
Recirculation architecture
SUPERVISOR
EXTERNAL
ENVIRONNMENT
PURGE
Draining
RECIRCULATOR
CONDENSEUR
CONDENSER
ANODE
A)
HYDROGEN
TANK
DETENDEUR
EXPANSION
HUMIDIFICATOR
HUMIDIFIER
COOLING/HUMIDIFICATION
Impact on the power module
architecture
Dead-end architecture
EXTERNAL
PURGE
DRAINING
ENVIRONNMENT
ANODE
HYDROGEN
DETENTE
EXPANSION
TANK
B)
SUPERVISOR
Impact on the power module
architecture
Steam-reforming of methanol/methane architecture
EXTERNAL
ENVIRONNMENT
C)
BURNER
ANODE
METHANOL
TANK
VAPORISOR
STEAMREFORMER
SELECTIVE
OXIDATION
WATER
TANK
SUPERVISOR
The complexity of the system is strongly increased in the
case of the reforming
Impact on the power module
architecture
Fuel architecture: Fuel Storage
The volume and weight of
each of these systems is
compared to gasoline,
methanol and battery storage
systems (each con-taining
(1 044500 kJ) of stored energy
Impact on the power module
architecture
Fuel architecture: CO2 emission
Performance and efficiency
Efficiency of the energy conversion
 Efficiency is defined as the relationship between the
“product” of the action to evaluate and a reference
which should be defined.
 For the fuel cell, as a converter of chemical energy in
electrical energy, the product is in general the provided
electric power
Power provided (systemoutlet)
Efficiency 
Power injected (systemeinlet)
Performance and efficiency
Expression of the energetic efficiency
•
The efficiency of the energy conversion in the stack compared to the
HHV of fuel is written:
Ustack Istack
henergy 
Ncomb ,e HHHV
•
If Stcomb is the ratio between the entering fuel flow and that consumed for
the production of the usable current I
St comb 
h energy
Ncomb ,e 2F
n cell Ipile
Upile
1
1
1 Ucell


n cell St comb  HHHV  St comb UHHV


2
F


H
•
where UHHHV is a symbolic “voltage” corresponding to the total energy
conversion of combustion into electrical energy what cannot be done.
This symbolic voltage is usually called thermo neutral voltage
Performance and efficiency
Expression of the energetic efficiency
 The power delivered by the system never equals that of the
stack as many components consume part of the energy
produced by the stack






Air compressor
Pumps (cooling, recirculation H2)
Actuators (valves, pressure regulators)
Sensors (pressure, temperature, flow)
Supervisor
Power electronics
 Practical efficiency of a system is :
h energy 

hconvert . Ustack Istack   Uaux Iaux
Ncomb ,e HHHV

Performance and efficiency
Expression of the energetic efficiency
The practical system efficiency expression is:
70
Pile à combustible seule
Rendement (%)
60
50
Groupe électrogène
40
30
20
h energy 

hconvert . Ustack Istack   Uaux Iaux

Ncomb ,e HHHV
10
0
0
10
20
30
Puissance nette (kW)
40
50
5. Power Fuel Cell module
Hybridizing
Jean-Paul Yonnet
VEHICLE POWER
 Different order of power of vehicles:





Tarins: 4 to 6 MW (Megawatts), fast train like TGV: 6 to 8 MW,
Trucks and Buses : 200 to 600 kW (kilowatts),
On-road cars: 50 to 100 kW,
City cars: 20 to 30 kW,
Small vehicles: go-kart, scooters, etc: 0.5 to 5 kW.
 Energy Flux:

Hybrid vehicle have two types of energy source:
• A temporary electrical energy storage (Batteries or
Supercapacitors),
• A second energy source: Internal Combustion Engine (ICE)
or Fuel Cell (FC).
Power FC module hybridizing
 Several objectives




To reduce the Fuel Cell (FC) stack power,
To manage the high power peak transients,
To recover the braking energy,
To increase the efficiency at low power.
 Different hybridizing levels depending on the transient
electric storage capacity



Some % of the FC system power,
• Use of batteries for e.g. starting.
Up to 50% of the FC system power,
• The batteries manages the power peak demands.
Higher then 50% of the FC system power,
• The FC is mainly used to supply the average energy consumption.
 The FC system definition will strongly depends on the global
architecture
HYBRID VEHICLE
 Hybrid operation:


One solution is to make a mechanical coupling of the axis of an
ICE (Internal Combustion Engine) and an Electric Motor. It is
called the Parallel Hybrid, or Mechanical Transmission Hybrid.
Parallel Hybrid Vehicle

Advantages and disadvantages of Parallel Hybrids:
• Electric machine and the associated converter are
dimensioned only for the electric power,
• The rotation speed is given by the wheel speed,
• Lower cost of the electric parts.
HYBRID VEHICLE
 Hybrid operation:

When the additional power source is a Fuel Cell, it cannot
create mechanical power. It can supply only electric power.
It is why only Series Hybrids are possible with Fuel Cell.
 Series Hybrid Vehicle
 Advantages and disadvantages of Series Hybrid:
• More simple mechanical structure,
• The additional power source can be used at its optimal
operation point,
• But the converter must be
designed for the maximum
power.
FUEL CELL VEHICLE

In the power part of a Fuel Cell vehicle, you have :







An Electrical Network at medium or high voltage (80V to
500V),
One or several Electrical Machines for the wheel propulsion,
Power Electronics to make all the energy conversions,
Batteries (or other type of electric energy storage),
the Fuel Cell,
the Hydrogen storage.
Operation of a FC Vehicle
6. Safety issues
Yann Bultel
HYDROGEN SAFETY
1.
2.
3.
4.
5.
6.
Hydrogen is odourless, colourless, tasteless and nontoxic.
Hydrogen has a very wide range of flammability.
Hydrogen is very buoyant and diffuses rapidly in air.
Hydrogen has very low ignition energy.
Hydrogen burns with a pale blue, nearly invisible, flame.
Hydrogen is non-toxic and non-poisonous.
Hydrogen
Methane
Propane
Gasoline
Lower flammability limits in air (%)
4
4.4
1.7
1.1
Upper flammability limits in air (%)
75
17
10.9
6.7
0.017
0.290
0.240
0.240
Minimum ignition energy (mJ)
HYDROGEN SAFETY

Hydrogen flame:
7. Fuel Cell Vehicle Example
Yann Bultel
HYDROGEN INFRASTRUCUTURE
Industrial hydrogen
Hydrogen, vector of energy
HYDROGEN INFRASTRUCUTURE
Goal :
An appropriate Hydrogen infrastructure
HYCHAIN VEHICLES
Hydrogen
storage
PAC
HYCHAIN VEHICLES
HYCHAIN VEHICLES
Application to vehicle
Application to wheelchair
Hychain Mini-trans
Emscher -Lippe
GERMANY
Rhône-Alpes
FRANCE
Castilla León
SPAIN
Emilia Romagna
ITALY