Fuel Cells: Part 1 1 Overview
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Classifica1on and applica1ons Performance figures of merit Stacks Types of fuel cells 2 Fuel cell types
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Fuel cells can be classified according to their fuel, the opera1ng temperature and the electrolyte Each type of fuel cell uses a par1cular fuel and materials, and has its own opera1onal characteris1cs This results in certain fuel cells offering advantages in par1cular applica1ons Central design consists of two electrodes, a cathode and an anode (in half cells) These two electrodes are separated by a solid or liquid electrolyte that allows electrically charged par1cles to travel between them. To accelerate the reac1ons at the electrodes a catalyst, such as pla1num, is generally present 3 Fuel%Cell%Types%
Fuel cell types
4 Applications
•  The overriding factors slowing the entry of fuel cell power plants and power sources into the terrestrial energy sector are the short life1mes of the cell stacks, capital cost and complexi1es of fuel-­‐processing •  We are beginning to see fuel cell power plants/power sources entering the energy sector for commercial applica1ons •  In 2007 fuel cells were for the first 1me sold to end-­‐users with wriRen warran1es and service capability that met required codes and standards •  PEMFCs and DMFC auxiliary power units (APU) were sold in their thousands for boats and caravans as well as many other leisure applica1ons •  Micro fuel cells started to be sold, in similar numbers, in the portable sector in toys and educa1onal kits •  DMFC and PEMFC portable power units started replacing heavy baRery packs in the military. They are used for surveillance equipment and communica1ons •  2010 saw total shipments of fuel cells grow by 40%, reaching a new high of almost 230,000 units 5 Applications:
Transport
PEM%Fuel%Cell%Example%
UTC Power bus (Polymer Electrolyte Membrane fuel cell – hydrogen/
oxygen) 6 Applications:Transport
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Propulsive power or range extension to a vehicle A 20% rise in 2010 saw a new high total of 2,400 units shipped 1 kW to 100 kW is the typical power range for fuel cells in this sector and the fuel cells that are by far the most prominent are PEMFCs and DMFCs One area where fuel cells have already been commercially available for many years is buses Fuel cell electric vehicles (FCEV) are available for rent in several countries by many major manufacturers. Major car manufacturers are using it to gain experience ahead of the planned commercial launches of FCEVs from 2015 e.g. Hyundai (‘blue square’ has a power output of 90 kW and can reach up to 100 mpg. 7 Applications: Portable
Portable power unit (Horizon Fuel Cell Technologies) for camping Intelligent Energy ‘Upp’: a portable charger for USB-­‐
compa1ble devices (uses a hydrogen fuel cell) 8 Applications: Portable
•  Fuel cells have great poten1al in this market due to the simple fact that they poten1ally offer five to ten 1mes greater energy densi1es than rechargeable baReries •  Covers a wide range of applica1ons from APUs, military applica1ons (portable soldier power), torches, educa1onal devices, large personal electronics (laptops, radios etc) and small personal electronics (cameras, mp3 players etc) •  Power ranges from approx 5 W to 500 kW. •  In terms of shipment, the portable sector is by far the largest with at least 75% of the total shipments every year since 2007 •  The sector has mainly been dominated by educa1onal devices and toys over the past five years because new entrants to the fuel cell market are using toys as an entry point with a view to improving their technology and help fund development for larger products that will ul1mately drive sales •  Also targe1ng a young audience (toys/educa1on) as a long-­‐term strategy 9 Applications: Portable
•  Portable fuel cells have not been as successful as was first predicted, mainly due to issues with miniaturisa1on and system integra1on •  Tablet computers are a possible launch pad for consumer electronics because miniaturisa1on is not as vital here as it is in mobile phones •  Even if fuel cells could get a small frac1on of this market, which saw sales of 18.7 million units in Q3 of 2011, this could be used to accelerate the wider adop1on of fuel cells in consumer electronics •  The fuel cells used for portable applica1ons are PEMFCs and DMFCs •  PEMFCs (mainly) and DMFC auxiliary power units have reached tens of thousands of cumula1ve sales during the last five years, par1cularly in the camping and leisure sector as an alterna1ve to internal combus1on engine (ICE) generators 10 Molten%Carbonate%Fuel%Cell%Example%
Applications:Stationary
SOFC%Example%
Molten carbonate fuel cell system (FuelCell Energy Inc.) backup system at Yale University 100 kW cogenera1on system (combined heat and power) developed by Siemens based on solid oxide fuel cells (SOFC) 11 Applications: Stationary
•  Sta1onary power is one of the most mature applica1ons for fuel cells •  SOFC, MCFC and PAFC technology are used, along with PEMFCs, and can supply anything from 0.5 kW to 400 kW of power •  Sta1onary fuel cell units can being used for backup power, power for remote loca1ons, stand-­‐alone power plants for towns and ci1es, distributed genera1on for buildings and co-­‐genera1on •  There is significant commercial interest in sta1onary fuel cells for uninterrup1ble power supply (UPS) applica1ons (backup or standby power to telecoms sites and other cri1cal infrastructure) •  As in the transport sector the North American market dominates due to US government incen1ves for companies using fuel cell installa1ons •  Sta1onary fuel cells units also have the poten1al to power homes and this is beginning to be adopted in Japanese homes with par1cular success •  Tens of thousands of small CHP fuel cell units have been sold since 2007, all providing residen1al heat and power 12 Figures of merit
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The power and energy is the same as that for any electrical system. Power = Ecell I Energy = Power × t = Ecell It •
The theore1cal voltage under standard condi1ons is: E0cell = E0cathode − E0anode
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This is called the (reversible) open circuit voltage (OCV) For other condi1ons we can use Nernst equa1on to get the ROCV In reality, the voltage is never the theore1cal value because there are irreversible losses 13 Brief view of losses
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Briefly, the losses comprise resistances to charge and mass transport as well as an energy barrier to forcing the charge reac1ons in each half cell away from equilibrium The real cell voltage is measured for different current and produces a polariza1on curve !
14 Figures of merit
•  Recall rela1onships between (max.) electrical work, Gibb’s free energy and (ideal) cell voltage Max. work = nFE0 = –ΔG0 (standard condi1ons) •  E.g., the H2/O2 fuel cell reac1on is H2 + (1/2)O2àH2O which has associated ΔG0 = –237 kJ mol–1 (G0products – G0reactants) •  From this we can predict E0 in a different way •  The energy density of a fuel cell is the energy available per unit mass (gravimetric) or volume (volumetric) •  The power density is the power per unit mass or volume 15 Then Faraday’s law states that if x moles of reagent Ox are reduced, the
Current, c
harge a
nd c
onversion r
ate [54]
total amount of charge (Q) spent is given by :
•  Faraday’s law states that if x moles of fuel is oxidised the total amount of charge (Q) generated is given by: (Eq. 2-2)
•  n is the number of moles of electrons transferred per mole of fuel, and Q is the charge in coulombs (C) •  If Fthe rate is constant
m
! x moles per second, C/mol),
then Faraday’s us the of
where,
isconversion the Faraday
(96485
n is law thegives number
!x
current I = nFm
electrons needed per mole of Ox,− and Q is the said charge, given in
•  Generally, consider a reac1on (n e transfer) ∑ r ν r r ⇔ ∑ p ν p p
coulombs
(C).r is a reactant with stoichiometric coefficient νr and p is a product with •  where stoichiometric coefficient νp. The number of moles of electrons transferred per second is I ÷ F. The ra1o of (moles of r consumed):(moles of electrons transferred) is νr ÷ n. of
Thus rate of conversion of rof
is amorphous FePO4 is
An example
calculation
thethe theoretical
capacity
ν
I
shown below:
m r = r × [mol s −1 ]
n
F
I
⎛
⎞
or
simply
is
frequency
of
reaction
⎜⎝
⎟⎠
nF
)
(Eq. 2-3)
16 Fuel cell stacks
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A single fuel cell is only capable of producing a theore1cal maximum of around 1 V This voltage is not large enough for most applica1ons Therefore, to produce higher voltages individual cells are linked together to form a fuel cell stack A fuel cell stack can be configured by connec1ng cells in series or parallel for increased voltage or current For series connec1on Estack = nEcell (Istack = Icell) For parallel connec1on Istack = nIcell (Estack = Ecell) A fuel cell stack has current collectors and separator plates The current collectors conduct the electrons from the anode to the separator plate. 17 Fuel Cell Stacks
•  The separator plates provide the electrical connec1on between cells and physically separates the oxidant flow of one cell from the fuel flow of the adjacent cell •  Usually the two current collectors and the separator plate are combined into a single unit called a bipolar plate •  The channels in the current collector serve as the distribu1on pathways for the fuel and oxidant. = (Videal – Vcell) x Icell
= (1.16 V – 0.7 V) x 60 A
= 0.46 V x 60 coulombs / sec. x 60 seconds / min.
= 1650 J / min
This cell is generating about 1.7 kJ of excess heat every minute
it operates, while generating about 2.5 kJ of electric energy
per minute.
e-
eHydrogen
flow fields
End-plate
Air
flow fields
Bipolar plates
End-plate
configura1on n cells): A Series 3 cell fuel cell
stack with two bipolar(plates
and two end plates.
Estack = nEcell 18 As m
this,
typic
is ob
form
next
colle
volu
colle
into
“bip
this
side
plate
the t
of fu
direc
elect
rout
work
cond
on o
the p
of th
the c
circu
In th
varie
The
cent
Proton Exchange Membrane Fuel Cell
•  The most important part of the cell is the membrane electrode assembly (MEA): a polymer electrolyte in contact with an anode and cathode on either side •  The membrane separates the gases on either side and allows protons pass from anode to cathode •  The electrochemical reac1ons at the electrodes are: •  Anode: H2 à 2H+ + 2e− (E0 = 0.0V) •  Cathode (1/2)O2 + 2H+ + 2e− à H2O (E0 = 1.26V) •  Overall: H2 + (1/2)O2àH2O (E0cell = 1.26V) 19 Proton Exchange Membrane Fuel Cell
20 Consider a 12 cell stack in series with a cell area of 100 cm2. If the stack operates at a current of 80 A, use the polariza1on curve below to determine the stack power in W and hydrogen consump1on rate in g of H2 / s. Cell Voltage (V) !
PEMFC Example
Current density (mA cm-­‐2) 21 PEMFC Example
Step 1) Determine the current density (same in each cell): 80 A
−2
−2
i=
=
0.8
A
cm
=
800
mA
cm
100cm 2
Step 2) From the polariza1on curve, the cell voltage Ecell = 0.62 V. Step 3) Therefore the stack voltage: VEstack = 12×Ecell = 7.44 V Step 4) The stack power is Pstack = Estack× I = 7.44 V x 80 A = 595 W 22 PEMFC Example
Step 5) Hydrogen consump1on rate ⎛ ν H2 I ⎞
!
mH2 = 12 cells × ⎜
⎝ n F ⎟⎠
⎛ 1 80A ⎞
−1
= 12 cells × ⎜
=
0.005
mol
H
s
2
⎝ 2 F ⎟⎠
= 0.005 mol H 2 s −1 ×
2g H 2
= 0.01 g H 2 s −1
mol H 2
23 Direct Methanol Fuel Cell
•  DMFCs were invented and developed at several ins1tu1ons in the United States, including NASA, in the 1990s •  Rela1vely recent addi1on to fuel cell technology •  DMFC is basically a PEMFC with methanol used directly instead of hydrogen. This is how DMFCs got their name •  The electrolyte is a polymer membrane and a pla1num-­‐
ruthenium catalyst on the anode is used to draw the hydrogen from the liquid methanol, meaning a fuel reformer is not required. •  Note that ‘PEM fuel cell’ includes DMFCs (they contain a PEM) but usually we mean direct hydrogen PEM fuel cell •  Electrode reac1ons •
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Anode: CH3OH + H2O à 6H+ + 6e− + CO2 (E0 = 0.02V) Cathode (3/2)O2 + 6H+ + 6e− à 3H2O (E0 = 1.23V) Overall: CH3OH + (3/2)O2à 2H2O + CO2 (E0cell = 1.21V) 24 Development in Direct Methanol – Oxygen Fuel Cell (DMFC)
Direct Methanol
Fuel Cell
Figure I: Direct Methanol – Oxygen Fuel Cell (DMFC).
eactions
node reaction -: CH3OH + 7H20
→
CO2 + 6H3O+ + 6e- E0 =0.02V
athode reaction -: 3/2O2 + 6H3O+ + 6e- →
9H2O
E0 =1.23V
_____________________________________________________________________
25 Direct Methanol Fuel Cell
•  The ideal cell voltage is 1.2 V which is very similar to a H2 PEMFC •  The methanol reac1on is slow compared to the hydrogen reac1on in PEMFCs, and the power densi1es are at the moment ten 1mes lower •  Such low power densi1es make them unsuitable for automobile applica1ons at the moment •  They are being inves1gated due to the possible weight and space savings they could provide if they are improved •  Similarity of methanol to conven1onal fuels in terms of ease of transport and containment means that the current fuel infrastructure for fossil fuels could be largely retained 26 Direct Methanol Fuel Cell
•  Power density can be improved if a beRer catalyst that pla1num is found •  Pla1num absorbs carbon monoxide (CO) molecules, which leads to poor performance •  Other possible catalyst candidates include Ru-­‐Pt alloy and Pt-­‐
Sn alloy (but unstable) (Pt=pla1num, Ru=ruthenium, Sn=1n) •  The open circuit voltage of a DMFC is significantly lower than the thermodynamic or reversible poten1al (see next slide) for the overall process because methanol crossover causes a mixed poten1al at the cathode (methanol is oxidized at the cathodic catalyst sites, thus reducing cell voltage) CH3OH + (3/2) CO2 à 2H2O 27 Direct Methanol Fuel Cell
0.8
0.10
0.09
0.7
0.08
Voltage (V)
0.5
0.06
0.4
0.05
0.04
0.3
2
0.07
Power (Watts/cm )
0.6
0.03
0.2
60 C
0.02
70 C
0.1
0.01
80 C
0.0
0.00
0.0
0.1
0.2
0.3
0.4
0.5
0.6
2
Current density (A/cm )
FIGURE 9 Several DMFC polarization curves taken at the Penn State Electrochemical Engine
Center, showing typical performance. Active area: 50 cm2, fuel solution molarity: 1.0 M,28 Direct Methanol Fuel Cell
•  DMFCs tend to operate between 60ºC to 130ºC and are used in applica1ons with low power requirements •  These include mobile electronic devices or chargers and portable power packs •  The convenience in carrying less fuel and having fewer components is more significant than efficiency in these small appliances •  In the small-­‐appliance market their main compe1tor is the lithium ion baRery, which can reach an energy density of <1500 Wh per l of the materials •  In comparison a 0.5 V DMFC is theore1cally capable of around 5000 Wh per l of methanol •  However, in prac1ce smaller DMFCs have not achieved even close to this value. 29 Direct Methanol Fuel Cell
•  DMFC power units have seen commercial trac1on in various countries •  E.g., forklit trucks tradi1onally been powered by baRery packs. Warehouse need to have baRery charging infrastructure. Can save space and charging 1me by switching to fuel cells. The infrastructure can be removed to save space and trucks can be refuelled in minutes compared to hours •  Also a big drive for developing portable applica1ons •  Military applica1ons (replacements for baReries being explored in the US) 30 Solid Oxide Fuel Cell
Yang et al., 2011 (Ref. 32)
(BaO/Ni-YSZ)/YSZ/(SDC buffer layer/LSCF)
750
750
850
Dry C3 H8
CO+3% H2 O
96% CO+1% H2
+H2 O, CO2 , and CH4 c
•  The high-­‐temperature fuel cell that aRracts the most aRen1on the solid assembly
electrolyte cell follows as “a” for anode/“el” for electrolyte/“c” for cathode. All cells are anode supported
a
Theis membrane-electrode
(MEA) composition
otherwise noted.
SOFCs use zirconia compounds as the electrolyte layer/
b •  The
cathode material is Sm0.5 Sr0.5 CoO3 (SSC).
c
This
fuel mixture was produced
an integratedo
fluidized-bed
operating
with solid a
carbon
and CO
H2 O.
membrane to using
conduct xygen gasifier
ions formed t the p2+3%
osi1ve electrode where |nO2 | is the absolute value of the stoichiometric coefwritten as
•
The e
lectrochemical r
eac1ons a
t t
he electrodes are ficient for oxygen, and pO2 ,c and pO2 ,a are the partial presAnode half-cell oxidation reactions:
of oxygen (in atmospheres) at the cathode and anode
sures
H2 (g) + O2 (el) *
) H2 O(g) + 2e (a)
2-­‐
− (subscripts
c
and
a),
respectively.
The
anodic
partial
pressure
•  Anode: 2H2 + 2O à 2H2O + 4e pO2 ,a is determined by equilibrium chemistry in the anode fuel
CO(g) + O2 (el) *
) CO2 (g) + 2e (a)
−
2-­‐
•
Cathode O
+
4
e
à
2
O
channel. Note that regardless of2 which oxidation reaction is
CH4 (g) + 4O2 (el) *
) CO2 (g) + 2H2 O(g) + 8e (
taking place,
the
number
of
electrons
per
mole
of
oxygen
is
•  Overall: 2H2 + O2à 2H2O C(s) + 2O2 (el) *
) CO2 (g) + 4e (a)
constant (i.e., ne /|nO2 | = 4). This is because the stoichiometry
is set by the cathodic reduction reaction, and is independent of
Cathode half-cell reduction reaction:
fuel
(and therefore,
the anodic thalf-cell
•  typeThese reac1ons ake preaction).
lace aThe
t tinhe surfaces of anode and O2 (g) + 4e (a) *
) 2O2 (el)
fluence of the anodic chemistry and electrochemistry appears
oC. cathode a
t a
t
emperatures o
f 6
00-­‐1000
indirectly through the anode oxygen partial pressure pO2 ,a .
Note that this nomenclature uses generic names in pl
The overall half-cell reduction-oxidation (redox) reactions
specific material names (i.e., “el” for electrolyte inst
for four typical fuels (anode) and oxygen (cathode) can be
“YSZ”); both will be used in this paper. To make the
31 1
Solid Oxide Fuel Cell
•  Based on an electrolyte of zirconia stabilised with the addi1on of a small percentage of yRria (Y203). Above temperature of 800 C zirconia becomes a conductor of oxygen ions (O= or O2-­‐) and typically the state of the art zirconia based SOFC operates between 800 and 1100 C (this presents opportuni1es for CHP •  The anode is usually a zirconia cement (an in1mate mixture of ceramic and metal). The metallic component is usually Ni (nickel chosen amongst other things because of its high electronic conduc1vity and stability •  Cathodes are usually made from electronically conduc1ng oxides or mixed electronically conduc1ng and ion-­‐conduc1ng ceramics. The most common cathode material of the laRer type is stron1um-­‐doped-­‐
lanthanum manganite (SLM). 32 Solid Oxide Fuel Cell
•  The advantage of having a fuel cell at such high opera1ng temperatures is that the reac1on kine1cs are improved so that a metal catalyst is not required •  Fuels can also be reformed within the system -­‐ this means an external reformer is not required and allows the unit to be used with a range of hydrocarbons •  Coal gas can be used as a fuel within SOFCs because they are rela1vely resistant to sulphur in small quan11es •  However there are disadvantages: the cell must be made from robust, heat resistant materials that have to be shielded to prevent heat loss •  They also take longer than other fuel cells to start-­‐up and reach the opera1ng temperature. 33 ecently other materials have been produced with enhanced oxide-ion
ctivity at temperatures lower than that required by zirconia. For example,
aMgO (LSGM) proved to be a superior oxide-ion electrolyte that provides
mance at 800ºC comparable to YSZ at 1000ºC.
•  The overall efficiency of SOFCs depends on materials, fuels and opera1ng temperature as well as the total device capability of supplying and recycling heat required for maintaining the opera1ng temperature, beyond what can be generated as waste heat of the fuel cell reac1ons themselves •  If the SOFC does harness this waste heat then efficiencies of y versus
reciprocal
Typical single cell performance of LSGM
60-­‐80% can temperature
be achieved Solid Oxide Fuel Cell
ide electrolytes
electrolyte (500 m thick)
34 Solid Oxide Fuel Cell
•  The target design life1me is currently about forty thousand hours for sta1onary installa1ons •  Degrada1on for current cell prototypes is roughly 1.7% per 1000 h or opera1on. This is ten 1mes an ideal value. •  Tubular SOFCs are used extensively in sta1onary power genera1on of all sizes and the micro-­‐tubular SOFCs are being developed for use in small portable chargers •  Planar types of several kilowaR output are being tested for co-­‐
genera1on applica1ons such as domes1c combined heat and power (CHP). •  Bloom energy, a Californian based energy company founded in 2001, builds 100 kW off-­‐grid power generators made from planar SOFCs. These are being used by companies such as Ebay, Google and Wal-­‐Mart as well as working alongside NASA in its Mars program. 35 Phosphoric Acid Fuel Cell
•  Phosphoric Acid Fuel Cells (like PEMFC) use a proton-­‐
conduc1ng electrolyte and the catalyst material is generally pla1num on porous carbon electrodes •  As usual the name of the cell comes from its electrolyte, phosphoric acid •  Electrode reac1ons: •  Anode: 2H2 à 4H+ + 4e− (E0 = 0.0V) •  Cathode O2 + 4H+ + 4e− à 2H2O (E0 = 1.26V) •  Overall: 2H2 + O2à 2H2O (E0cell = 1.26V) •  Opera1ng temperature in the range of 175-­‐200oC •  Phosphoric acid is the only inorganic acid that exhibits the required thermal stability, chemical and electrochemical stability and low enough vola1lity to be effec1vely used. 36 Phosphoric Acid Fuel Cell
37 Phosphoric Acid Fuel Cell
•  The anode and cathode reac1ons are the same as those in the PEM fuel cell with the cathode reac1on occurring at a faster rate due to the higher opera1ng temperature •  The increased temperature also means a higher tolerance to impuri1es (especially CO) •  The only technology which showed rela1ve tolerance for reformed hydrocarbon fuels and thus could have widespread applicability in the near term •  Simple construc1on, stability and low electrolyte vola1lity mean that they are durable •  The most mature fuel cell technology in terms of system development and commercializa1on ac1vi1es. •  Disadvantages: Large size and weight and low power and current 38 Phosphoric Acid Fuel Cell
•  Phosphoric acid has a rela1vely high freezing point of 42oC compared to other electrolyte materials used in other fuel cells •  This means that the cell must be kept above this temperature at all 1mes so that the acid does not freeze (and so expand), causing internal stresses in the containment system •  During opera1on small amounts of acid electrolyte is lost, therefore the acid must be replenishable or excess acid placed into the fuel cell ini1ally •  If the process heat is harnessed for co-­‐genera1on, efficiencies of 80% can be achieved 39 Phosphoric Acid Fuel Cell
•  Used in hospitals, nursing homes and for all commercial purposes •  Due to the long start-­‐up 1me, as is always the case with high-­‐
temperature fuel cells, automobile companies do not see it as a viable op1on for their applica1ons •  Although with output in the 100 kW to 400 kW range, they are a finding applica1on in applica1ons such as large vehicles i.e. buses •  The most likely future for PAFCs is sta1onary power generators; currently the largest power output for a PAFC power plant is 11 MW of grid quality AC power. However anything up to 65 MW is seen as achievable in the near future •  The major impediment is cost, £1900/kW currently, much higher than other fuel cells. 40 Molten Carbonate Fuel Cell
•  MCFCs work quite differently to other fuel cells. They use a molten carbonate salt mixture (commonly lithium carbonate with sodium or potassium carbonate) as the electrolyte, which for stability and strength is supported within a porous aluminate matrix (e.g. LiAlO2) •  To achieve high ion mobility through the electrolyte these salts are melted at a very high temperature (about 660oC or higher) meaning that MCFCs are in the class of high-­‐temperature fuel cells •  Electrode reac1ons •
•
•
•
•
Anode: H2+CO32−+H2O à 2e−+H2O+CO2 Cathode (1/2)O2+CO2+ 2e− à CO32− Overall: H2+(1/2)O2à 2H2O The carbon dioxide from the oxida1on reac1on is in most designs recycled as input to the cathode Cell voltages typically range from 0.6V to 1.1V 41 Molten Carbonate Fuel Cell
!
42 Molten Carbonate Fuel Cell
•  CO2 may also be produced by combus1ng the anode exhaust gas which is mixed directly with the the anode inlet gas •  The high opera1ng temperature improves chemical reac1on kine1cs and so there is no need for noble metal catalysts •  High temperature opera1on makes the MCFC resistant to carbon monoxide contamina1on and as a result, may use alternate fuels such as natural gas or methane. •  High efficiency, up to 60% electrical efficiency or when used as combined heat and power (CHP) up to 80% •  High temperature opera1on limits applica1ons to sta1onary power plants (slow startup 1me) •  Short life span due to electrode and electrolyte degrada1on •  Inject CO2 at cathode as carbonite ions consumed by anode reac1on 43 Molten Carbonate Fuel Cell
•  Primary applica1on is sta1onary power plants (Electrical U1li1es , Industrial and distributed power genera1on, Military and Government (US)) •  Large systems : typically 250kW to 3MW •  Future applica1on may include ship power plants (Navy and civilian shipping) •  Example sta1onary power plant installa1on is Miramar Marine Corps Air Sta1on (San Diego, 1997) -­‐ 250 kW MCFC prototype •  Key challenges a. Increase the opera1ng temperature b. Increase ionic conduc1vity of the electrolyte c. Decrease the polariza1on losses of the electrodes 44