Fuel cell: from principle to

application to the electric

vehicle

Yann BULTEL, GINP

Marian Chatenet, GINP

Laurent Antoni, CEA

Jean-Paul Yonnet, CNRS

1. Fuel Cell Introduction

2. Fuel Cell – Principle of Operation

3. Fuel Cell Performances

4. Fuel Cell Power System

5. Power Fuel Cell Module Hybridizing

6. Safety issues

7. Fuel Cell Vehicle Example

PLAN

1. Fuel Cell introduction

Yann Bultel

Fuel cells are electrochemical conversion systems,

which offer unique characteristics as electrical

power generation systems.

What’s a fuel cell ?

Heat loss

Electrical power

H2

H2in O2

in / Air

H2Oout

, O2 / Air

ANODECATHODE

What’s a fuel cell ?

HISTRORICAL CONSIDERATION

1842: Sir William Robert Grove is known as “Father of the Fuel Cell.”

reaction triple contact electrolyte-reactants-catalyst

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 : CEAFuel Cell Vehicle

HISTRORICAL CONSIDERATION

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

N

NN

N

H

H

[ ]n

Electrode

Active(/Catalyst) Layer:

Materials: ~ Carbon grains supported

Platinum nanoparticles;

Electrochemical reactions (Hydrogen

oxidation and Oxygen reduction).

UNIT CELL COMPONENT

• 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?

Electrode

Active(/Catalyst) Layer:

Which electrocatalysts for the cathode ?

UNIT CELL COMPONENT

Electrode

Gas Diffusion Layer:

Materials: ~ Carbon cloth/paper and

Teflon;

Gas supply.

Water removal

UNIT CELL COMPONENT

GDLSubstrate (C fabric)

Carbon (powder)

Hydrophobic-

porosity-binding

agent (PTFE)

ALElectrocatalyst

Electrolyte

Carbon

Hydrophobic-

porosity-binding

agent (PTFE)

MembraneIonic conducting polymer

Electronic insulator

Barrier to reagent

MEA

UNIT CELL COMPONENT

Gas Diffusion Layer (GDL)

Reagent feeding

Products draining

(water & reagent excess)

Current collecting

Thermal management

Mechanical support

Active Layer (AL)

Electrochemical reactions

+ function of the GDL

MembraneA & C reagent separation

Ionic transport

Electronic insulator

Mechanical support

MEA

UNIT CELL COMPONENT

150 µm

Bipolar plate

Electrode Membrane

Assembly

End plate

UNIT CELL COMPONENT

External current collecting

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

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

Ucell

Electric network: cells in series

Ucell Ucell

n

k

k

cellstack UU1

I

e-

n

k

k

cellstack UIP1

FUEL CELL STACK

ANODE

CATHODE

O2in / Air

H2in

Gas supply: cells in parallel

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);

Polarisation curve

Ei=0

ORR irreversibility

1

2

3

Cell voltage

U (V)

Current density

i (A/cm2)

Er

1 - Activation overvoltage hact 2 – Ohmic drop hohm 3 – Diffusion limitation hdif

Electrocatalysts, Sact Ions and e- resistance Gas diffusion to the catalyst

(membrane, electrodes)

Gas

diffusionH2

H+

e-

Ionic

resistance

Ohmic

resistance

e- transfer

resistance

(activation)

The triple contact

FUEL CELL PERFORMANCES

Activation overpotential: Kinetic Tafel Law

h

0

acti

iln

3.2

b

Overpotential Current density

Log(i)

Overvoltage at the

surface of an electrode

h (V)

b : Tafel constant

i0 : exchange current density

Experimental parameters

FUEL CELL PERFORMANCES

Activation overpotential: Kinetic Tafel Law

FUEL CELL PERFORMANCES

Impedance study of the oxygen reduction reaction on platinum nanoparticles in

alkaline media, L. Genies, Y. Bultel, R. Faure, R. Durand, Electrochimica Acta (2003)

b : Tafel slope

Internal Resistive losses

Electronic and Ionic conductivity of materials

Nafion: ionic = 5 S m-1 Bipolar plate: ionic = 5000 S.cm-1

jRj L

V eelectrolytm

mionic

H+

Resistance of the

flow of ions

Resistance of the

flow of electrons

> >

FUEL CELL PERFORMANCES

Mass Transport limitation:

finite mass transport rates limit the supply of fresh

reactant;

Faraday’s law:

Limiting current density jL

Concentration overpotential:

H2O

GDLAL

O2

SB CCD F n

i

CB

CS

0CD F n

i BL

FUEL CELL PERFORMANCES

h

L

conci

i1ln

nF

RT

Power density versus current density:

0

0,2

0,4

0,6

0,8

1

1,2

0 0,2 0,4 0,6 0,8 1 1,2 1,4

i / A cm-2

Y /

-

P / W cm-2

U / V

FUEL CELL PERFORMANCES

celle U IW

Heat production:

OHO2

1H 222

Hr

Electrical

power

Heating rate Maximum efficiency possible

cell

rheat U

F2

HIQ

celle U IW

FUEL CELL PERFORMANCES

2

ohmic I RQ

I Q concact h

I.nF

STQ ityreversibil

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

FUEL CELL PERFORMANCES

nF

IF react,i [mol.s-1]

nF

iN react,i [mol.s-1.m-2]

Mass and Heat Balances:

PEMFC Stack

Mass Balance:

Heat Balance:

nF

INFF cellout,iin,i

FUEL CELL PERFORMANCES

inoutpiicool TTcmQ

One species mass balance O2 or H2:

Gas Utilization Rate:

Stoichiometric ratio

nF

IFIFFF out,ireacti,out,iin,i

in,i

out,iin,i

in,i

react,i

iF

FF

F

FU

anode

cathode

Fa,in Fa,out

Fc,inFc,out

Sti=1 : Stoichiometric conditions

FUEL CELL PERFORMANCES

ireact,i

in,i

iU

1

F

FSt

Water management:

FUEL CELL PERFORMANCES

Gas channel

H2O Water diffusion

Cathode

Electro-osmotic flow

Gas channel

Anode

H2O, O2, N2

H2O, H2

H2O

F2

ir electro

O2H

iF2

2N

dragelectro

O2H

m

c

O2H

a

O2H

O2H

diffusion

O2HL

ccDN

O2Hsat PPevap/cond of Rate

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

On board

Stationary

Portable

Depends on the environment

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

FUEL

CELL

CODITIONNING

INLET/OUTLET

ANODE

ELECTRICAL CONVERTORS

EX

TE

RN

AL

EN

VIR

ON

NM

EN

T

EX

TE

RN

AL

EN

VIR

ON

NM

EN

T

FU

EL

TA

NK

COOLING : WATER MANAGEMENT

BUSBATTERIESAUXILIAIRIES

VE

HIC

LE

CO

OL

ING

SUPERVISOR

CODITIONNING

INLET/OUTLET

CATHODE

FUEL

CELL

CODITIONNING

INLET/OUTLET

ANODE

ELECTRICAL CONVERTORS

EX

TE

RN

AL

EN

VIR

ON

NM

EN

T

EX

TE

RN

AL

EN

VIR

ON

NM

EN

T

FU

EL

TA

NK

COOLING : WATER MANAGEMENT

BUSBATTERIESAUXILIAIRIES

VE

HIC

LE

CO

OL

ING

SUPERVISOR

CODITIONNING

INLET/OUTLET

CATHODE

Highest complexity

Recovery of mechanical energy from compression

Management of the liquid water from humidification

« High pressure » operation

Example of cathode

inlet/outlet subsystem

FILTER COMPRESSOR HUMDIFIER

CATHODE

EXTERNAL

ENVIRON-

MENT

SUPERVISOR

EXPANSION

TURBINE

SEPARATOR /

CONDENSER

COOLING /

WATER MANAGEMENT

Anode inlet/outletInfluence 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

A)HUMIDIFICATOR

ANODE

CONDENSEURRECIRCULATOR

DETENDEUR

PURGE

COOLING/HUMIDIFICATION

SUPERVISOR

HYDROGEN

TANK

EXTERNAL

ENVIRONNMENT

HUMIDIFIER

ANODE

CONDENSERRECIRCULATOR

EXPANSION

Draining

COOLING/HUMIDIFICATION

SUPERVISOR

HYDROGEN

TANK

EXTERNAL

ENVIRONNMENT

Recirculation architecture

Impact on the power module

architecture

B)

DETENTEHYDROGEN

TANK

PURGE

ANODE

EXTERNAL

ENVIRONNMENT

SUPERVISOR

EXPANSIONHYDROGEN

TANK

DRAINING

ANODE

EXTERNAL

ENVIRONNMENT

SUPERVISOR

Dead-end architecture

Impact on the power module

architecture

The complexity of the system is strongly increased in the

case of the reforming

C)

VAPORISOR

METHANOL

TANK

WATER

TANK

BURNER

STEAM-

REFORMER

SELECTIVE

OXIDATION

ANODE

EXTERNAL

ENVIRONNMENT

SUPERVISOR

VAPORISOR

METHANOL

TANK

WATER

TANK

BURNER

STEAM-

REFORMER

SELECTIVE

OXIDATION

ANODE

EXTERNAL

ENVIRONNMENT

SUPERVISOR

Steam-reforming of methanol/methane architecture

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

inlet) (systeme injectedPower

outlet) (system providedPower E fficiency

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:

• If Stcomb is the ratio between the entering fuel flow and that consumed for the production of the usable current I

• 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

HHVe,comb

stackstack

energyHN

IU

h

pilecell

e,comb

combI

F2

n

NSt

HHV

cell

combHHV

pile

combcell

energy

HU

U

St

1

F2

H

U

St

1

n

1

h

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 :

HHVe,comb

auxauxstackstack.convert

energyHN

IUIU

hh

0

10

20

30

40

50

60

70

0 10 20 30 40 50

Puissance nette (kW)

Re

nd

em

en

t (%

)

Pile à combustible seule

Groupe électrogène

Performance and efficiency Expression of the energetic efficiency

The practical system efficiency expression is:

HHVe,comb

auxauxstackstack.convert

energyHN

IUIU

hh

5. Power Fuel Cell module

Hybridizing

Jean-Paul Yonnet

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).

VEHICLE POWER

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.

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

FUEL CELL VEHICLE

6. Safety issues

Yann Bultel

HYDROGEN SAFETY

1. Hydrogen is odourless, colourless, tasteless and non-

toxic.

2. Hydrogen has a very wide range of flammability.

3. Hydrogen is very buoyant and diffuses rapidly in air.

4. Hydrogen has very low ignition energy.

5. Hydrogen burns with a pale blue, nearly invisible, flame.

6. 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

Minimum ignition energy (mJ) 0.017 0.290 0.240 0.240

HYDROGEN SAFETY

Hydrogen flame:

7. Fuel Cell Vehicle Example

Yann Bultel

Industrial hydrogen Hydrogen, vector of energy

HYDROGEN INFRASTRUCUTURE

Goal :

An appropriate Hydrogen infrastructure

HYDROGEN INFRASTRUCUTURE

HYCHAIN VEHICLES

PAC

Hydrogen

storage

HYCHAIN VEHICLES

Application to wheelchair

Application to vehicle

HYCHAIN VEHICLES

Hychain Mini-trans

Castilla León

SPAIN

Emilia Romagna

ITALY

Emscher -Lippe

GERMANY

Rhône-Alpes

FRANCE