Fuel cell with introduction, types with description, application and uses.

1. Fuel Cell Technology

2. Topics
1. A Very Brief History
2. Electrolysis
3. Fuel Cell Basics
- Electrolysis in
Reverse
- Thermodynamics
- Components
- Putting It
Together
4. Types of Fuel Cells
- Alkali
- Molten Carbonate
- Phosphoric Acid
- Proton Exchange
Membrane
- Solid Oxide
5. Benefits
6. Current Initiatives
- Automotive
Industry
- Stationary Power
Supply Units
- Residential Power
Units
7. Future

3. A Very Brief History
Considered a curiosity in the
1800’s. The first fuel cell was
built in 1839 by Sir William
Grove, a lawyer and gentleman
scientist. Serious interest in
the fuel cell as a practical
generator did not begin until
the 1960's, when the U.S. space
program chose fuel cells over
riskier nuclear power and more
expensive solar energy. Fuel
cells furnished power for the
Gemini and Apollo spacecraft,
and still provide electricity
and water for the space
shuttle.(1)

4. s this have to do with fuel cells?”
By providing
energy from a
battery, water
(H2O) can be
dissociated into
the diatomic
molecules of
hydrogen (H2)
and oxygen (O2).
Figure 1

5. Basics
lectrolysis in reverse.”
The familiar process of electrolysis
requires work to proceed, if the
process is put in reverse, it should
be able to do work for us
spontaneously.
The most basic “black box”
representation of a fuel cell in
action is shown work
below:
Figure 2
O2
fuel H2O
H2
cell
heat

6. uel Cell Basics
hermodynamics
H2(g) + ½O2(g) H2O(l)
Other gases in the fuel and air inputs
(such as N2 and CO2) may be present,
but as they are not involved in the
electrochemical reaction, they do not
need to be considered in the energy
1 Thermodynamic properties at 1Atm and 29
calculations.
H2 O2 H2O (l)
Enthalpy 0 0 -285.83
(H) kJ/mol
Entropy 130.68 205.14 69.91
(S) J/mol·K J/mol·K J/mol·K
Enthalpy is defined as the energy of a
system plus the work needed to make
room for it in an environment with
constant pressure.
Entropy can be considered as the
measure of disorganization of a

7. uel Cell Basics
hermodynamics
f the chemical reaction using Hess’ Law:
ΔHreaction = ΣHproducts – ΣHreactants
= (1mol)(-285.83 kJ/mol) – (0)
= -285.83 kJ
py of chemical reaction:
ΣSproducts – ΣSreactants
mol)(69.91 J/mol·K)] – [(1mol)(130.68 /mol·K) + (½mol)(2
J
63.34 /K
J
gained by the system:
= TΔS
= (298K)(-163.34 J/K)
= -48.7 kJ

8. uel Cell Basics
hermodynamics
free energy is then calculated by:
ΔH – TΔS
= (-285.83 kJ) – (-48.7 kJ)
= -237 kJ
done on the reaction, assuming reversibility a
W = ΔG
one on the reaction by the environment is:
W = ΔG = -237 kJ
sferred to the reaction by the environment
ΔQ = TΔS = -48.7 kJ
More simply stated:
The chemical reaction can do 237 kJ of
work and produces 48.7 kJ of heat to
the environment.

9. Fuel Cell Basics
Components
Anode: Where the fuel reacts or
"oxidizes", and releases electrons.
Cathode: Where oxygen (usually from
the air) "reduction" occurs.
Electrolyte: A chemical compound that
conducts ions from one electrode
to the other inside a fuel cell.
Catalyst: A substance that causes or
speeds a chemical reaction
without itself being affected.
Cogeneration: The use of waste heat to
generate electricity. Harnessing
otherwise wasted heat boosts the
efficiency of power-generating
systems.
Reformer: A device that extracts
pure hydrogen from

10. l Cell Basics
tting it together.
Figure 3

11. Types of Fuel Cells
The five most common types:
•Alkali
•Molten Carbonate
•Phosphoric Acid
•Proton Exchange Membrane
•Solid Oxide

12. Types of Fuel Cells
SOFC
Vorteil: Keine aufwendige Brenngas-Aufbereitung
Nachteil: Hohe Betriebstemperaturen = Hohe System-Kosten
 Starke Material-Beanspruchung

13. Alkali Fuel Cell
compressed
hydrogen and
oxygen fuel
potassium
hydroxide (KOH)
electrolyte
~70% efficiency
Figure 4 150˚C - 200˚C
operating temp.
300W to 5kW
requires pure hydrogen
output
fuel and platinum
catylist → ($$)
liquid filled container →
corrosive leaks

14. Molten Carbonate Fuel Cell (MCFC)
carbonate salt
electrolyte
60 – 80%
efficiency
~650˚C operating
temp.
cheap nickel
electrode
Figure 5 catylist
up to 2 MW
The operating temperature is up
constructed,
too hot for manyto 100 MW designs
applications.
exist
carbonate ions are consumed in
the reaction → inject CO2 to
compensate

15. hosphoric Acid Fuel Cell (PAFC)
phosphoric acid
electrolyte
40 – 80% efficiency
150˚C - 200˚C
operating temp
11 MW units have
been tested
Figure 6 sulphur free
gasoline can be
The electrolyte a fuel
used as
is very corrosive
Platinum
catalyst is very

16. Proton Exchange Membrane (PEM)
thin permeable
polymer sheet
electrolyte
40 – 50%
efficiency
50 – 250 kW
80˚C operating
Figure 7
temperature
electrolyte will not
leak or crack
temperature good for
home or vehicle use

17. Solid Oxide Fuel Cell (SOFC)
hard ceramic
oxide
electrolyte
~60% efficient
~1000˚C
operating
temperature
Figure 8
cells output
high temp / catalyst can 100 kW
up to extract
the hydrogen from the fuel at the
electrode
high temp allows for power
generation using the heat, but
limits use

18. Benefits
Efficient: in theory and in practice
Portable: modular units
Reliable: few moving parts to wear out
or break
Fuel Flexible: With a fuel reformer,
fuels such as natural gas, ethanol,
methanol, propane,
gasoline, diesel, landfill
gas,wastewater, treatment
digester gas, or even ammonia can be
used
Environmental: produces heat and
water (less than combustion in both

19. terial‘s challenges of the PEM Fuel Cel

20. Review of Membrane
(Nafion) Properties
• Chemical Structure
• Proton Conduction
Process
• Water Transport and
Interface Reactions
11/25/12 Fuel Cell Fundamentals 20

21. cal structures of some membrane mater
PSSA PESA
poly(sty (Polyepoxy-
rene-co- succinic Acid)
styrenes
ulfonic
acid)
(PSSA)
α,β,β-
Trifluorosty
Nafion,TM rene grafted
Membrane C onto
poly(tetrafl
uoro-
ethylene)
with post-
Poly –
sulfonation)
AMPS
Poly(2-acrylamido-
Dow
2-methylpropane
sulfonate)

22. Nafion Membrane
Chemical Structure

23. Nafion Membrane
on Conduction Process

24. The water transport
through Nafion
Membrane
Water flux due to electroosmotic drag (mol/cm2 s) is: Nw, drag = Iξ(λ)/F.
Where: I is the cell current, ξ(λ) is the electroosmotic drag coefficient at a
given state of membrane hydration λ(=N(H2O)/N(SO3H) and F is the Faraday
constant. This flux acts to dehyddrate the anode side of a cell and to
introduce additional water at the cathode side.
The buildup of water at the cathode (including the product water
from the cathode reaction) is reduced, in turn, by diffusion back down the
resulting water concentration gradient (and by hydraulic permeation of water
in differentially pressurized cells where the cathode is held at higher overall
pressure). The fluxes (mol/cm2 s) brought about by the latter two
mechanisms within the membrane are:
Nw,diff = -D(λ)∆c/ ∆z, Nw,hyd = -khyd(λ)∆P/ ∆z
where D is the diffusion coefficient in the ionomer at water content λ, ∆c/ ∆z
is a water concentration gradient along the z-direction of membrane
thickness, khyd is the hydraulic permeability of the membrane, and ∆P/ ∆z is a
pressure gradient along z.

25. The water transport
through Nafion
Membrane
Many techniques have been
introduced to prevent the
dehydration of the anode
(including the introduction of
liquid water into the anode
and/or cathode, etc. – which,
however, can lead to “flooding”
problems that inhibit mass
transfer).
However, the overall question of
“water management,” including the
issue of drag as a central
component, has been solved to a
very significant extent by the
application of sufficiently thin
PFSA membranes (<100 µm thick) in
PEFCs, combined with humidification
of the anode fuel gas stream.

26. Water Transport (& Interface
Reactions)
in Nafion Membrane of the PEM Fuel
Cell

27. Material‘s challenges of the SOFC

28. Solid Oxide Fuel Cell
SOFC
Air side = cathode: High oxygen partial pressure
O2
H2 + 1/2O2  H2O
1
conductance = σ µ
H2 d
H2O
Fuel side= anode: H2 + H2O= low oxygen partial pressure

29. Electromotive Force (EMF)
SOFC
Chemical Reactions in 2 separated compartements:
- Cathode (Oxidation): ½O2 + 2e-  O2-
- Anode (Reduction): H2 + O  H2O + 2e
2- -
∆G = Free Enthalpie
z = number of charge carriers
F = Faraday Constant
EMF of a galvanic Cell: ∆G0= Free Enthalpie in
(1) EMF = ∆Gr /-z F standart state
R = Gas Constant
a ( H 2O )
SOFC: ½O2 + H2  H2O (2) ∆G = ∆G0 + RT ln
a( H 2 )a (O2 ) 0.5
difference of ∆G between anode und cathode 
RT p ( O2 )
K
Nernst Equation:
EMK = ln
4 F p ( O2 )
A

30. Elektrochemische Potential
SOFC
Oxygen ions migrate due to an electrical
and chemical gradient
∆µ (O 2− ) = ∆µ (O 2− ) − 2 F ∆ϕ
%
Electrochemichal Chemical Electrical
Potential Potential Potential
Driving force for the O2- Diffusion through the electrolyte are the
different oxygen partial pressures at the anode and the cathode
side: ∆µ (O 2− )
%
σi
∆µ (O 2− )
ji = ionic current
ji = − % σi= ionic conductivity
2F

31. engl. Open Circuit Voltage (OCV)
SOFC
σi
∆µ (O ) = ∆µ (O ) − 2 F ∆ϕ
% 2− 2−
ji = − ∆µ (O 2− )
%
2F
What happems in case :
∆µ
% (O 2− ) = 0
ji = 0
No current
OCV Electrical potential difference = chemical potetial

32. Leistungs-Verluste
SOFC
Under load decrease of cell voltage
and internal losses
U(I) = OCV - I(RE+ RC+RA) - ηC - ηA
OCV
(RE+ RC+RA) Ohmic resistances
cell voltage U(I) [V]
ηC
Non ohmic resistances=
ηA over voltages
cell current I [mA/cm2]

33. Überspannungen
SOFC
Over voltages exist at interfaces of
• Elektrolyte - Cathode
• Elektrolyte - Anode
Reasons:
•Kinetic hindrance of the electrochemical reactions
•Bad adheasion of electrode and electrolyte
•Diffusion limitations at high current densities

34. Ohm‘s losses
SOFC
Past Future
800nm
Kathode Anode
Reduce electrolyte thickness

35. Leistungs-Verluste
SOFC
OCV 1
(RE+ RC+RA)
cell voltage U(I) [V]
ηC
ηA
2
cell current I [mA/cm2]
3
(1) Open circuit voltage (OCV), I = 0
(2) SOFC under Load  U-I curve
(3) Short circuit, Vcell = 0
(2) 0.5
1.0
Zellspannung [V] 0.4
0.8
Leistung [W/cm
0.3
0.6
0.2
0.4
2
]
0.1
0.2
(1) 0.0
900°C
in Luft/Wasserstoff (3) 0.0
0.0 0.5 1.0 1.5 2.0
2
Stromdichte [A/cm ]

36. How to determine the electrical conductance
SOFC
Iinput Umeasured
Electrical resistance:
U ∆L
R = f (T ) = =
I A *σ
Electrical conductivity: U : voltage [V]
I : current [A]
σ0 Ea R : resistivity [ohm]
σ= log( − ) ∆L : distance between both
T kT inner wires [cm]
A : sample surface [cm2]
1 σ : conductivity [S/m]
σ T vs. ⇒ Ea Ea : activation energy [eV]
T T : temperature [K]
K : Boltzmann constant

37. SOFC
SOFC-Designs

38. SOFC Design
SOFC
Tubular design
i.e. Siemens-Westinghouse design
Segment-type tubular design
Planar design
i.e. Sulzer Hexis, BMW design

39. Tubular Design – Siemens-Westinghouse
SOFC
Why was tubular design
developed in 1960s by
cathode Westinghouse?
interconnection • Planar cell: Thermal
expansion mismatch
cathode between ceramic and
(air) support structures leads to
problems with the gas
sealing  tubular design
air flow anode (fuel) was invented
Advantages of tubular
design:
• At cell plenum: depleted air
and fuel react  heat is
generated  incoming
oxidant can be pre-heated.
• No leak-free gas
manifolding needed in this

40. Tubular Design – Siemens-Westinghouse
SOFC
To overcome problems new
cathode Siemens-Westinghouse „HPD-
(air)
SOFC“ design:
New: Flat cathode tube with
ligaments
anode (fuel) electrolyte Advantages of HPD-SOFC:
• Ligaments within cathode  short
current pathways  decrease of
ohmic resistance
• High packaging density of cells
Siemens-Westinghouse shifted from
compared to tubular design
basic technology to cost reduction and
scale up.
Power output: Some 100 kW can be
produced.

41. Planar Design – Sulzer Hexis
SOFC
interconnect Advantages of planar
cathode (air)
design:
• Planer cell design of bipolar
electrolyte
plates  easy stacking  no
anode (fuel)
long current pathways
• Low-cost fabrication
methods, i.e. Screen printing
and tape casting can be
used.
Drawback of tubular
design:
• Life time of the cells 3000-
7000h  needs to be
improved by optimization of
mechanical and
electrochemical stability of
used materials.

42. Planar Design – BMW
SOFC
Air channel
bipolar plate
Cathode current collector
cathode
electrolyte
anode
porous metallic substrate
Fe-26Cr-(Mo, Ti, Mn, Y2O3) alloy
bipolar plate
Fuel channel Application
Batterie replacement in the
20-50 µm Plasma spray BMW cars of the 7-series.
5-20 µm Plasma spray
15-50 µm Plasma spray Power output: 135 kW is
aimed.

43. Current Initiatives
Automotive Industry
Most of the major auto manufacturers have
fuel cell vehicle (FCV) projects currently
under way, which involve all sorts of fuel
cells and hybrid combinations of
conventional combustion, fuel reformers and
battery power.
Considered to be the first gasoline powered
fuel cell vehicle is the H20 by GM:
GMC S-10 (2001)
fuel cell battery hybr
low sulfur gasoline fue
25 kW PEM
40 mpg
112 km/h top speed
Figure 9

44. Current Initiatives
Automotive Industry
Fords Adavanced
Focus FCV (2002)
fuel cell battery
hybrid
85 kW PEM
~50 mpg
(equivalent)
4 kg of
compressed H2 @
Figure 10
5000 psi
Approximately 40
fleet vehicles
are planned as a
market
introduction for
Germany, Figure 11
Vancouver and
California for

45. Current Initiatives
Automotive Industry
Chrysler NECAR 5 (introduced in 2000)
85 kW PEM
fuel cell
methanol fuel
reformer
required
150 km/h top
speed
Figure 12
this model completed a California to Washing
permit for Japanese roads

46. Current Initiatives
Automotive Industry
Mitsubishi Grandis FCV minivan
fuel cell /
battery
hybrid
68 kW PEM
compressed
hydrogen
fuel
140 km/h top
Figure 13
speed
Plans are to launch as a
production vehicle for Europe in
2004.

47. Current Initiatives
Stationary Power Supply Units
More than 2500 stationary fuel cell
systems have been installed all over
the world - in hospitals, nursing homes,
hotels, office buildings, schools,
utility power plants, and an airport
terminal, providing primary power or
backup. In large-scale building
systems, fuel cells can reduce
facility energy service costs by 20%
to 40% over conventional energy
service.
Figure 14
A fuel cell installed at McDonald’s
restaurant, Long Island Power
Authority to install 45 more fuel

48. Current Initiatives
Residential Power Units
There are few residential fuel cell
power units on the market but many
designs are undergoing testing and
should be available within the next
few years. The major technical
difficulty in producing residential fuel
cells is that they must be safe to
Residential
install in a home, and be easily
fuel cells
maintained by the average homeowner.
are typically
the size of a
large deep
freezer or
furnace, such
as the Plug
Power 7000
Figure 15 unit shown
If a power company was here, and cost
to install a
$5000 - $10
residential fuel cell power unit in a
000.
home, it would have to charge the
homeowner at least 40 ¢/kWh to be

49. Future
“...projections made by car companies
themselves and energy and automotive
experts concur that around 2010, and
perhaps earlier, car manufacturers
will have mass production capabilities
for fuel cell vehicles, signifying the
time they would be economically
available to the average consumer.”
Auto Companies on Fuel Cells, Brian Walsh and Peter
A commercially available fuel cell
Moores, posted on www.fuelcells.org
power plant would cost about
$3000/kW, but would have to drop
below $1500/kW to achieve widespread
market penetration.
http://www.fuelcells.org/fcfaqs.htm
Technical and engineering innovations
are continually lowering the capital
cost of a fuel cell unit as well as
the operating costs, but it is expected
that mass production will be of the
greatest impact to affordability.

50. Future
internal
combustion
obsolete?
solve pollution
problems?
common in homes?
better designs?
higher
efficiencies?
cheaper
electricity?
reduced
petroleum
dependency?

51. References
(1) FAQ section, fuelcells.org
(2) Long Island Power Authority press release: Plug Power
Fuel Cell Installed at McDonald’s Restaurant, LIPA to
Install 45 More Fuel Cells Across Long Island, Including Homes,
http://www.lipower.org/newscenter/pr/2003/feb26.fuelce
ll.html
(3) Proceedings of the 2000 DOE Hydrogen Program Review:
Analysis of Residential Fuel Cell Systems & PNGV
Fuel Cell Vehicles,
http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/2
8890mm.pdf
Figures
1, 3 http://hyperphysics.phy-
astr.gsu.edu/hbase/thermo/electrol.html
4 – 8 http://fuelcells.si.edu/basics.htm
10
http://www.moteurnature.com/zvisu/2003/focus_fcv/focus
_fcv.jpg
11
http://www.granitestatecleancities.org/images/Hydrogen_F
uel_Cell_Engine.jpg
12
http://www.in.gr/auto/parousiaseis/foto_big/Necar07_2883.
jpg
13
http://www3.caradisiac.com/media/images/le_mag/mag138/o
eil_mitsubishi_grandis_big.jpg
14
http://www.lipower.org/newscenter/pr/2003/feb26.fuelce