Fuel cells for electric utility and transportation applications

J. Electroanal. Chem., 118 (1981) 51--69

51

Elsevier Sequoia S.A., Lausanne -- Printed in The Netherlands

FUEL CELLS FOR ELECTRIC UTILITY ~ D

TRANSPORTATION APPLICATIONS

S. SRINIVASAN Brookhaven National Laboratory,

Upton, New York 11973, U.S.A.

ABSTRACT This review article presents: (i) the current status and expected progress status of the fuel cell research and development programs in the U.S.A., (ii) electrochemical problem areas, (iii) techno-economic assessments of fuel cells for electric and/or gas utilities and for transportation, and (iv) other candidate fuel cells and their applications. For electric and/or gas utility applications, the most likely candidates are phosphoric, molten carbonate, and solid electrolyte fuel cells. The first will be coupled with a reformer (to convert natural gas, petroleum-derived, or biomass fuels to hydrogen), while the second and third will be linked with a coal gasifier. A fuel cell/battery hybrid power source is an attractive option for electric vehicles with projected performance characteristics approaching those for internal combustion or diesel engine powered vehicles. For this application, with coal-derived methanol as the fuel, a fuel cell with an acid electrolyte (phosphoric, solid polymer electrolyte or "super" acid) is essential; with pure hydrogen (obtained by splitting of water using nuclear, solar or hydroelectric energy), alkaline fuel cells show promise. A fuel cell researcher's dream is the development of a high performance direct methanol-air fuel cell as a power plant for electric vehicles. For long or intermittent duty cycle load leveling, regenerative hydrogen-halogen fuel cells exhibit desirable characteristics.

TIlE RENAISSANCE OF FUEL CELLS AFTER THE ENERGY CRISIS OF 1973 The cells

energy are

crisis

of

1973

stimulated

the only energy conversion

of fuels directly

to electricity,

without

the main objective of prolonging term and coal in the long term,

the

renaissance

devices,

of

which convert

the intermediary

fuel

Fuel energy

of heat.

the life of fossil fuels, it is necessary

cells.

the chemical

Thus, with

petroleum in the near

to develop

fuel cell systems

for

the generation of electricity and heat and as power sources for vehicular propulsion.

The primary aims of the national e n e r g y p l a n

of the U.S.A.

methods for the more efficient use of natural gas and petroleum,

are to develop to shift towards

the utilization of the more abundant coal reserves and eventually utilize the renewable resources (nuclear,

solar,

fusion).

TYPES OF FUEL CELLS, THEIR ADVANTAGES AND POTENTIAL TERRESTRIAL APPLICATIONS The

essential

(higher cells

than with

may

be

requirements

of

conventional

characterized

as

a

fuel

plants), modular,

cell

power

plant

are

low capital

cost

and

pollution

free,

and

high

long

efficiency

life.

highly

Fuel

efficient

52 devices

that offer applications

megawatts. in

fuel

Due to the difficulty cells

reactions.

it

is

reformed

electrolyte

it is essential

to

gases The

fuel

range of power levels

of the direct

necessary

is essential.

oxide

cells,

(I), Since

electrolyte solid

over a wide

contain

possible

cells

to utilize

utilization

produce

the

carbon

options

(2).

the

To minimize

electrocatalysis

former,

phosphoric

cations

such

as

spinning

the molten

advantages

for base

view of direct as

vehicles

and

higher temperatures

tageous

than

sources direct

are

play

for

fuel

power

vehicles

for

vehicles. cells

(3).

role

are

it will

intermittent

duty cycle energy storage

building

cell

of

represented

in

block - the

the

United

Figure

by a Teflon

The static electrolyte The reactions

Anode Cathode Cell

from

the

difficult

coal

distinct points

for

fuel

engine

of

As long cell

vehicles.

economy,

electrolyte, for

alkaline

generation

and

"super"

terrestrial

fuel

as

power

acid

and

applications.

may find application

for long or

(4).

binder,

The

cell - of

the most advanced

Corporation

Teflon-bonded

particles, and

(UTC)

porous

supported

backed

is contained

(5),

gas

phosphoric is

conductive

in an inert inorganic

schematically

diffusion

on a conductive

by a porous

acid

electrodes

carbon and held support

sheet.

or organic matrix.

in the cell are as follows:

2H 2 + 4H20 02 + 4H3 O+ + 4eo 2H 2 + 02

Electrode Kinetics and Electrocatalysis

single

Technologies

I.

consist of platinum catalyst together

have

ACID FUEL CELLS

Single Cells - Design, Reactions,

fuel

With

cells

or diesel

power

shots

fuel cells (e.g., hydrogen-halogen)

The

systems.

fuel

a hydrogen

polymer

Regenerative

PHOSPHORIC

best for appli-

hybrid vehicles will be more advan-

In

Solid

gasifier

of a steam re-

appears

be

or fuel

are favored.

generation

dispersed

long-range

of

the system efficiency.

combustion

fuel cell/battery

a distinct

electric

methanol

internal

rejecting

200°C are desirable.

energy

electrolyte

increasing

available,

with

methanol,

conventional

could

load

of CO and

fuels

integrated

solid

fuels

carbonate

efficiency

fuels, a system composed

or

and

intermediate

to compete

With coal-derived

cells

reserves

carbonate

utilization

petroleum-derived

powered

>

acid fuel cell, and power conditioner,

gasifiers,

CO 2

heat for the endothermic

Thus reactions of fuel cells at temperatures problems,

a

to

gasification

acid, molten

reactions.

With natural gas or petroleum-derived

by

dioxide,

To maximize

their waste

of the fossil

hydrogen

are

from watts

>

4H3 O+ + 4eo

>

6H20

(i) (2)

~

2H20

(3)

58 l i J

e---~

l

FIELD

Figure I.

Single Cell in UTC Phosphoric Acid Fuel Cell.

The typical cell performance Figure

2.

tials. is

This

figure also

It is obvious

the

dominant

(6) as a function of current density

illustrates

the anode, cathode

that the irreversibility

cause

for

the

loss

is shown in

and ohmic overpoten-

of the oxygen electrode

in electrochemical

reaction

cell efficiency

of about

45%. Platinum

is the best

electrode reactions. reduced

from about

electrodes, trodes.

maining

10 mg

mainly

At

electrode

due

a current

problem

at

successful

density

of 200 mA cm -2,

the

Secondly,

it

is

hydrogen

to

in activity

with

time

electrode sulfide

reduce

its

of both

the electrolyte.

to sintering

in finding solutions

tion of support material,

of carbon

is

and oxygen

cm -2 on both

supported

elec-

the overpotential at the hydrogen it is 400 mV.

the poisoning

due

overpotential

A re-

to impurities,

(with a synergistic effect

stable oxygen electrodes

of corrosion

due

the hydrogen

to about 0.75 mg

development

the open circuit potential are encountered.

sible approaches

both

the noble metal loading has been

at the oxygen electrode,

or hydrogen

essential

side effects

for

cm -2 at each electrode,

to the

Finding better and more

Firstly,

electrocatalyst

is only 20 mV, whereas

such as carbon monoxide H2S).

known

During the last i0 years,

of CO and

is a major problem area. by

at

least

i00

mV.

the carbon and platinum at close Thirdly,

to

there is a slight decrease

of the electrocatalyst

particles.

to these problems are by alloying,

Pos-

altera-

pretreatment of support or change in proton activity of

54

I.I

I.O - -

0

0.9

--

.E Z uJ

0 8 - -

I-0

0.7

--

1977 CELL

~

,IIR~ 1977 i~ ANODE[

06

--

o.5 25

Figure 2.

I

I

I

I

50

75

I00

125

I

I

]

I

I

I

150 175 2 0 0 225 2 5 0

2 7 5 3(30

C U R R E N T DENSITY, mA/cm2 Single Cell Performance in UTC Phosphoric Acid Fuel Cell (6).

Multi-cells - Design, Operation and Performance The fuel cell stack consists lyte matrix,

cathode,

of a series

and graphite

bipolar

of repeating units - anode, electroplate.

In the UTC

fuel

cells,

the

stacks are liquid cooled, while in the Energy Reserch Corporation (ERC) fuel cell (7), the stacks are air cooled. trochemical

combustion

and

for

In the ERC cells, cooling,

which

the same air is used for elec-

simplifies

heat

removal

from

the

stack and is reliable and inexpensive. An

important

recent

United Technologies

development

Corporation

(8).

is

the

ribbed

substrate

cell

stack

A comparison with a conventional

of

the

stack is

shown in Figure 3. CONVENTIONAL CELL CONFIGURATION

RIBBED SUBSTRATE CELL CONFIGURATION ANODE SUBSTRATE

CATHODE DENSE GRAPHITIZED / ~ - - ~ " . - . ~ : : ~ > ~ . _ ~ ~ ~ S U B S T R A T E " PLATES,CRO~FLOW " ~ . ~ _ _ : ~ _ _ , ~ > ~ ~ ~ RIBS ~ I ; E P A R A T O R f F~ ~ PLATE

VIEW A

.~'~>"~J~-~STORE ~ . ~ ~ ~ " ~ -

POROUSPLATES ACID. ONE RiBPATTERN

VIEW e

Figure 3. UTC Phosphoric Acid Fuel Cell-Improvements in Stack Configuration (8). This new configuration reduces stack cost and maintenance intervals, and improves electrochemical efficiencies.

GG One by

of the problems

evaporation,

components.

in the multi-cell

absorption

reduce

pressures

the

stack is the small loss of electrolyte

carbon

components,

or

corrosion

of

This loss may make it necessary for electrolyte replenishment

finding methods to minimize and

in

capital

costs

by

it.

cell or for

Efforts are underway to improve cell performance

operating

at higher

temperatures

(up to 225°C)

ar8

(about i0 atmos.).

Power Plants - Design, Development, Applications, Performances and Economics The most advanced fuel cell power plant is the one using phosphoric acid electrolyte.

EXHAUST

i

AIR

PROMCOOLINGTOWER II

WATERTREATMENT

SYSTE. TOWER

GLYCOL/WATER

TO COOLING

TURBO COMPRESSORS

eARUXE R ~'-- : ~ I[ START

EXHMOST

II

II

TMS SEPARATOR BURNER II R H~!~ [ F~<;~J I POWERSECTION (FUELCELLS}

FUEL: _~ ~ l FUL[~[~RECYCLE' BLOWER

:::~ <:COOLANTpuMP COOLANTWATERDc OUTPUT

/,I ~ ~L~_ HYDRODESULFURIZER

WATER -,~"TREATMENT SYSTEM

---

................. TOPOWER ............. CONDITIONER \ CONTROL '.',SIGNALS -- -~'==~ ..... FROMSiTE -1 I CONTROLLER OCMODULE SUPERVISORY CONTROL

Figure 4. Schematic of UTC Phosphoric Acid Fuel Cell Power Plant. The power plant (5) consists of three major sub systems: (i) fuel processor, which converts the hydrocarbon or alcohol fuel to hydrogen, (ii) fuel cell module, which produces dc power by the electrochemical combustion of hydrogen and oxygen, and (iii) power conditioner, which converts dc to ac° A program is underway at UTC to develop, install and test a 4.8 M W fuel cell power plant in New York City (9). The fuel processor, which incorporates a hydrodesulfurizer, reformer and shift converter, is designed to operate on naphtha, with natural gas as an alternate fuel. The fuel cell module consists of two truck transportable pallets, each containing ten 240 kW fuel cell stacks. The fuel cell stacks are arranged in a series-parallel arrangement to produce 3000 volts dc. The dc power is fed to the power conditioner, which converts the 4.8 MW to three-phase 60-cycle ac at 13.8 kilovolts and 4.5 MW. The 4.8 MW fuel cell power plant is designed to operate at 25 to 100% of rated power and with any change in power level to be effected in 15 sec. Such a power plant is being considered for a peaking device or a spinning reserve by an electric utility. The overall efficiency of this power plant (chemical@electrical energy) is projected to be about 40%, which is a considerable improvement over the values (25-35%) for gas turbines. The capital costs of the MW size fuel cell power plants are projected to be of the order of $350/kW. Though this is higher than that of gas turbines, the cost of electricity for fuel cell power plants and gas turbines should be of the same order, when one takes into account the fuel efficiency, lifetime, and environmental factors.

56

A novel application

of kW size phosphoric

"on site integrated

energy

heat by fuel cells,

particularly

little competition centers,

systems"

(10-12).

hospitals,

etc.

in industries,

source

strations,

Corporation,

testing,

MOLTEN CARBONATE

The electrolyte

device.

The ongoing

Industries,

Electrode Kinetics,

for utilization

programs

for operating

of a porous sta-

tile and porous nickel oxide cathode

(Figure

tile, 1-2 mm thick, consists of sub-micron particles

(30% by

at 650°C

is 40% LiAI02,

28% K2C03,

steel cell housings,

cavities.

steel

stainless

electrodes

and provides a wet-seal

a sintered

nickel

to~ prevent

structure,

slntering

of

housing

Anode or

occurring

(optimum compo-

and 32% Li2C03).

containing

the micron-size

ensures

low contact

small amounts nickel

to enhance

It is

which form the anode and cathode resistance

for the fuel and oxidant gases.

is doped with 2-3% lithium

reactions

at UTC,

and Materials

and a molten mixture of lithium and potassium carbonates

The

gas, dis-

to electric

will soon lead to demon-

fuel cell (13) consists

held between two stainless

cathode

its energy

FUEL CELL POWER PLANTS

bilized nickel anode, an electrolyte

sition

and convert

shopping

and market assessments.

The single cell in a molten carbonate

volume),

buildings,

to be close to 90%, which easily sur-

and Engelhard

Single Cells - Design, Reactions,

5).

apartment

The overall efficiency

is projected

passes that of any other energy conversion ERC-Westlnghouse

and

acid fuel cell. This system is made even more ef-

ficient by coupling it with a heat pump. energy

of electricity

The idea is to use natural gas, or synthetic

reform it to hydrogen

and heat energy in a phosphoric

of the primary

The generation

is for

in the power range 40-500 kW, is an option with

for applications

tributed by pipelines,

acid fuel cell power plants

of additives,

particles.

The

its electronic

of

such as Cr, nickel

oxide

conductivity.

2H 2 + CO 3 2CO + CO 3

~

CO 2 + H20 + 2eo

(4)

~

(5)

Cathode

CO 2 + 1/202 + 2Co

~

Overall

2H 2 + 02

•

2H20

(3)

2C0

~

2C02

(7)

+ 02

The optimum operating potential

temperature

vs. current density

power density at present 135 mW cm -2.

The

in the cell are:

2C02+ 2eo 2CO 3

or

the

The anode is

(6)

of the cell is about 650°C.

A typical cell

plot for a single cell is shown in Figure

6.

The

is about 125 mW cm -2 and is quite close to the goal of

At about 200 mA cm -2,

the activation

and mass

tials add up to about 250 mV, while the ohmic contribution

transfer

overpoten-

is about 75 mV.

From

5?

an

electrode

kinetic

carbon monoxide required.

As

point

of

view,

is not a poison

the

advantages

but a reactant,

and

of

this

(ii)

seen from equations 4 to 7, CO 2 is produced

reactant

at

the

effluent

to the

cathode. cathode

This oxidant

necessitates stream.

the

supply

The sulfur

cell

are

noble metals

that

(i)

are

not

at the anode but is a of

CO 2 from

and chlorine

the

anode

tolerances

the cell are only a few parts per million.

TILEI ETALBIPOLARCELLSEPARATOR AND GASMANIFOLD

WETSEAL-

~

HOLDINGFORCE CURRErITCOLLECTORAND ELECTRODESUPPORT

DIRECTION0 ~ X ~ ' F ' ~ ~ L

(porous Ni O ~ , ~ . _ . ~

Figure 5.

- ANODE (porousstobilizedNi)

[ / / ~ H O L D I N G FORCE

Single Cell in UTC-IGT Molten Carbonate Fuel Cell (13).

I.I

~-I.C <_ lz ~J

_~0,9 W

(376mV/IOOrnA/cm2)

O

0.8

40

Figure 6.

L

I

[

l

eo 120 160 200 240 CURRENT DENSITY,mA/cm e

Single Cell Performance in UTC-IGT Molten Carbonate Fuel Cell (13).

of

58

Multi-Cells - Design, Operation and Performance The multi-cell development until

on a molten

rather

limited

present

time.

cells,

(active area of

electrodes

about

tested

jointly

Institute

by

the

activity

the

A

of Gas

major

problem

areas

sulfur and chlorine impurities loss

due to vaporization

rservoir

for

hours),

corrosion

stack,

was

designed,

and

consisting

replenishment

to

fuel

cells:

and

Technologies

(i) tolerance

to

(ii) electrolyte

overcome by having an electrolyte

achieve

the

design

goal

seal area (this is minimized

alumina, but its lifetimes are uncertain),

of 20

developed,

the United

is only a few parts per million,

in the wet

been

The work to date has revealed the

carbonate

(it can be partially

sufficient

(iii)

(14).

in molten

fuel cell has

cell

Technology

Corporation for about a 1000-hour period following

fuel

900 cm2),

carbonate

of

40,000

by coating with

(iv) phase transformations

in tile due

to thermal cycling, and (v) mode of separating CO 2 from anode effluent and transfer to inlet cathode gas stream.

Power Plants - Design, Development, Applications, The molten

carbonate

load power generation, fuel

cell module,

fuel

cell

power

plant,

cycle,

and power a current

tential

efficiency

0.85 volts,

lifetime

of

chemical

cell stack.

plants

over

base

load

and

will include as its principal components,

bottoming

pected goals for this system are: of

Performance, and Economics for

an

40,000

overall

hours,

and

(coal

7).

to electricity)

cost

of $60/kW

of molten

of electricity

a coal gasifier,

(Figure

The

ex-

density of 150 mA cm 2 at a cell po-

a capital

A second application

is for cogeneration

conditioner

intermediate

and heat.

for

carbonate

of

45-50%,

the electro-

fuel

cell

power

The high grade waste heat

from molten carbonate fuel cells could be used for district heating or for industries

requiring

such high

the U.S.A. molten current

30-month

Electric

Power

carbonate program,

Research

ment, and testing.

quality fuel

heat.

supported

Institute,

satisfy 40,000

will the

hours

be essential following for

by

the

focuses

This will be followed

totype coal based molten carbonate programs

The

cell

requirements: and

U.S. on

industrial

are UTC,

GE,

and

(i)

with that of advanced gasification/combined

of

stack

and

IGT.

Energy

design,

and

in The the

develop-

by the design and construction of pro-

whether

(iii)

participants

ERC,

Department

cell

fuel cell power plants.

in deciding

stack),

active

cell program

such types

reliable cost

of

The results

of these

of power plants will

performance, electricity

(ii)

long

life

to be competitive

cycle gas turbine power plants.

59

CONDENSATE , ~ PUMP ~,,,,,.,,,~l _ /'-"p-, i - ,,,jBO'LER-SUPERHEATER ~'CCONOENSER STEAM TURBINE~ IRON OXIDE RI~H;~T Lf~ GENERATOR I OESULFURIZER ~ 1 [ REGENERATING ~ ( AIR---'--~ ~-I"-I'--'-I-I'-~-SULFIJR ] FEED H2O 'T ~ I RECOVERY PUMP

COAL H2O..."

~

^COAL^. ] ~'--~-'~ :~,U;AL, L PREPARATIONI 1

[ l { / /

IFEEBFRI L

' eTi~AM~ ~

I

ABSORBING z

~

MOLTEN''

t COAL I GASIFIER

k',.

~

I CARBONATE C

I

/

F/C

ECONOMIZER OF~E~TOR

FRE'C'YC'L['-

II

I

J PUMP I

~

t.

ASH

rY-"-n

~

/TURBO COMPRESSORS i

L__,~. _.J

Figure 7.

UTC Molten Carbonate FuelCell Power Plant Design (13).

SOLID ELECTROLYTE FUEL CELL POWER PLANTS

Single and Multi-Cells - Design, Reactions, Electrode Kinetics, and Materials With the aim of minimizing ohmic overpotentials, the Westinghouse Research and Development Center is concentrating on the design and fabrication of thin film solid electrolyte fuel cells, using electrochemical vapor deposition methods for the electrodes, electrolytes, and interconnections (Figure 8) (15).

4

Oz

i. Electrolyte 2. Fuel Electrode 3. Air Electrode 4. Interconnection

H20 -

~'

H:,

Figure 8. Bi-Cell in Westinghouse Solid Electrolyte Fuel Cell (16).The total thickness of a cell stack (i.e., electrodes, electrolytes, and interconnections), is about i00 ~. Since such a thin film fuel cell stack would be fragile, it is

60 deposited on a porous zirconia support tube. The order and mode of deposition of the respective layers are as follows: (i) a slurry of nickel oxide and yttriastabilized zirconia is sintered on the porous support tube. The nickel oxide is reduced with hydrogen, leaving a porous cermet, 20 ~ thick. This nickel is partially dissolved electrochemically to achieve a band and ring structure for multi-cell fabrication; (ii) electrochemical vapor deposition of magnesium and aluminum doped lanthanum chromite - a gas tight interconnection layer with a thickness of approximately 20 N . An alternate method which may be of value to attain the proper composition is RF sintering; (iii) electrochemical vapor deposition of yttria-stabilized zirconia (electrolyte layer) 20 ~ thick. During this deposition, interconnections are masked; (iv) chemical vapor deposition of tin doped indium oxide, the air electrode current collector (more recently, lanthanum manganite, was found to be more stable during fuel cell operation). The porous electrolyte layer under the air electrode is then impregnated with praseodymium nitrate solution, which is thermally decomposed to the oxide. Praseodymium oxide reduces the air electrode overpotential. The reactions occuring in the fuel cell may be represented as follows: Anode

2H 2 + 202-

~

H20 + 4eo

(8)

or

2C0 + 202-

>

2C02+ 4e~

(9)

02 + 4eo

)

202-

(i0)

>

2H20

(3)

)

2C02

(7)

Cathode Overall or

2H 2 + 02 2C0

+ 02

The conducting species in the electrolyte is the oxide ion. Cell stacks (consisting of 5, 7 and 18 cells) have been fabricated and tested. The projected performance of 400 mA cm -2 at 0.66 volts, necessary to meet power plant goals, was met (16). However, a performance degradation, due to flaking of the indium oxide in spots over the interconnection material, was observed. The substitution of lanthanum manganite for indium oxide appears to overcome this problem. Investigations of the electrode kinetics of the oxidation of the fuel and of reduction of oxygen, using direct current and alternating currents are in progress. Even at 1000°C (the cell operating temperature), catalytic effects of the oxygen electrode material are apparent. The slow step for oxygen reduction on some metals (eg., Pt) is the dissociative adsorption of oxygen (17). A photograph

of the fuel cell stack is shown in Figure 9.

~ection

Fue! El~trode Porous SupportTube

Figure 9.

Multi-Cell

in Westinghouse

Solid Electrolyte

Fuel Cell (16).

61 Power Plants - Design, Development, Applications, Performance, and Economics Coal will play a dominant the U.S.A.,

but

it will

role as the primary

still be necessary

aim of extending its lifetime. ten carbonate,

expected

source,

which

are currently

to have the highest overall efficiencies

tion in an electric utility).

from

the electrochemical

proposed product

that

A schematic

for the coal gasification subsystem.

the fuel cells

(about 50%) for the conversion

representation

is partially

For

efficient

of a coal gasification

is a reactant

fuel

cell

technologies, make

any

liquids

technology

described

has

involved

is at

assessments.

some

its

the

heat

transfer,

it has

been

Carbon monoxide,

and not a poison,

infancy

in the preceding

distinct

However,

advantages

in electrochemical

fabrication

techniques

and

at (18)

subsystem,

the

fuel cell.

in

as

a

in phosphoric

The solid electro-

comparison

sections.

water required, and minimal air pollution are

The high grade

Carbon dioxide is not a cathodic reactant in the solid electro-

economic

technology

i0.

supplied by the waste heat

the reactor.

lyte fuel cell but is so in the molten carbonate lyte

in the

energy (for base load power genera-

be located within

of coal gasification,

acid fuel cells.

(phosphoric, mol-

under development

- solid electrolyte fuel cell power plant is found in Figure required

in

fuel cells integrated with coal gasification plants are

of the chemical energy of coal to electrical

heat

particularly

to use it most economically with the

Of the three fuel cell systems

solid electrolyte),

U.S.A., solid electrolyte

energy

It

this

is

stage,

- use

of

invariant

levels.

with

the

rather it

low

other

premature

appears cost

that

materials,

electrolyte,

of small cells

to this no

no cooling

Some of the apparent

large number

two

problems

in megawatt

High Voltage, Direct Current Electrical Energy T l Fuel ~,. Nitrogen Cell | Bank / #2 ~--- Air

size plants.

Gas Cleaninq t - ~ H2, CO

Fuel H20 , CO2 [~

Cell

:

Banks

Electrical Energy

'~ Fuel~-Nitrogen ,

1'

Ce,

Bank

r-

l

[ #]

~---Air

H2, CO, H20, CO2 Figure i0.

Westinghouse Solid Electrolyte Fuel Cell Power Plant Schematic

(16).

62 FUEL CELLS FOR TRA~]SPORTATION APPLICATIONS Rationale for Fuel Cell Powered Vehicles As

long

as petroleum-derived

liquid

fuels

are available,

there will

be very

little competition for internal combustion engine or diesel powered vehicles. the "coal era" and the following

"nuclear,

In

solar and fusion era" with methanol or

hydrogen being the synthetic fuels, the high efficiency and low pollution characteristics

of a fuel cell makes

this energy converter an appealing alternative as

a power source for automotive propulsion. Several

conventional

vehicles.

The

Ragone

and advanced batteries

are being considered

plot

a

(Figure

11)

predicting performance characteristics I000

I

I

I

800

I

very

useful

for electric

illustration

for

of electric vehicles (19). I

I

I

CURRENT PROJECTED PAFC1985

6OO

is

i

I

I

I

~NTERLNA~ ~ _ ~ _ _ . . . . . . ~ COMBUSTION ENGINE-/

4OO

EXTERNALICOMBUSTIONENGIN'E

300

zOO

Zn/NiOOH \\

•x X

\ Na/S I

Pb/PbOz ~

\~(~

11

~

'

"

L~./Fesz

I00 o

80 ~-

~,///"

\ /,~

\ /


_\

/\~

,o

\

30

,~

\ , X--k. ~

/

/~/-ALKALINEFC 1985

lJ_i

, _ _ I _". . . .

C-.-Tj I" L

\" L . ~

/

zo

i ~,

ALKALINE FC1969

,

\

,,I

30 40

60 BO iO0

I0

I I

;0

ZO

z00

I

I

300 400

I

I

soo BOO lOOO

SPECIFIC ENERGY(Whig) Figure 11. Ragone Plots for Batteries, Fuel Cells, and Various Heat Engines. The specific power versus specific energy relations for internal and external combustion engines and for gas turbines are also shown in Figure 11. These plots are horizontal for the energy converters (including fuel cells) but vertical for the energy storers. The mechanical energy converters have the desirable characteristics of high power/weight (required for start-up, acceleration) and energy/weight (required for range) ratios, while the fuel cells have low power/weight ratios but can attain high energy/weight ratios (the latter, for the mechanical and electrochemical energy converters, are determined by the amount of fuel carried on board the vehicle). Batteries can attain high power/weight ratios but have relatively low energy/weight ratios.

63

The Fuel Cell/Battery

Hybrid Power Source

Figure II demonstrates the performance

that the only way in which electric vehicles

characteristics

cell/battery

hybrid

demonstrated

by

power

Kordesch

of engine-powered

source (20),

(Figure the

12).

fuel

cell

vehicles

is by use of a fuel

In this

type

provides

the

longer

life in the shallow depths

battery hybrid operation. tric

vehicle,

for

acceleration,

Deep discharges,

considerably

the fuel cell during efficiency

fuel

shorten

cruising.

in

power

during

hybrid for

required

for

such a fuel cell/ in a battery

The battery

requirements

first

Batteries will have

which will occur

life.

long range and fast refueling.

Furthermore,

battery

cycle

A fuel cell/battery

utilization,

not be altered with this concept cles).

of discharge

of vehicle, power

cruising and the battery that for start-up and acceleration. a much

can reach

elec-

will be charged vehicle

start-up,

The fuel distribution

offers

by

high

cruising

and

network will

(as will be the case with battery powered vehi-

a fuel cell/battery

technology--presently

hybrid vehicle

available

lead

acid

requires or

no breakthrough

nickel-zinc

batteries

will be more than adequate.

l

AIR

FUEL/FUEL PROCESSOR

FUEL CELL

CONTROLS

HOTOR

CRUISING)

BATTERY

(SIZED FOR START-UP AND ACCELERATION)

Fuel Cell/Battery

Figure 12.

Reformed Carbonaceous No single

factor has inhibited

Much of the complexity, fact

that natural

processing as a fuel,

bulk,

and weight

processor

derived

requires

as much as the

and heat exchangers

and plumbing processing

day fuel cells

fuels require For instance,

a hydrodesulfurizer,

a high temperature

fuels from coal or biomass,

of fuel cells

of present

gas and petroleum

(700°C) steam reformer, reactor,

the development

from petroleum cannot be used directly in a fuel cell.

prior to use in the fuel cell stack. the fuel

(23).

Fuels and Acid Fuel Cells

fact that the hydrocarbons

the

Hybrid Power Plant for Electric Vehicles

shift reactor,

simpler.

from of

if naphtha is used a high temperature

a low temperature

for the fuel processor.

becomes

accrues

a high degree

shift

With alcohol

A i:i by volume mixture

64

of methanol and water can easily be reformed at 190°C and the reformate + trace CO) fed directly shift converter and attractive

into a phosphoric

is necessary.

Such a fuel cell power plant is compact,

for transportation

The phosphoric

technologically

lysts.

However,

creased

to 0 . 7 5 mg cm -2 cell area.

in the

extension

of life to many thousand

ft 2 being

area of electrodes)

Undoubtedly,

the platinum

acid electrolytes tigated

(21).

that of phosphoric

these fuel

loading

complexes

and an increase

temperatures,

In the development

exhibit

< 100°C,

has

of 400 cells

(3.25

to 200 mW cm -2.

More recently,

other

acid (TFMSA) have been invesat 90°C

superior

Other sulfonic and phosphoric

of 1 g/kW

with

to dispense

these

to

acids

Reduction of the

appears

alternate

with platinum

phthalocyanins)

dewith

density

a performance

possible.

At

electrolytes

in

and use metal-organic

as electrocatalysts.

of phosphoric acid fuel cells for integrated

energy systems

the focus has been on improving efficiency.

There has been

to reduce volume and weight.

to optimize

to stacks

of power

in the vicinity

it may be possible

incentive

scale-up

loading

in conjunction

for potential use in fuel cells (22).

(e.g., porphyrins,

necessary

the catalyst

loading will be further reduced.

to an amount

and utility networks, little

hours,

acid fuel cells at 200Oc.

low operating cells,

section,

platinum electrocata-

This has been achieved

with 6 N TFMSA

are now being synthesized platinum

third

requires

such as trifluoromethanesulfonic

Cells

No

simple,

applications.

acid fuel cell, as stated

(H 2 + CO 2

acid fuel cell operating at 200°C.

power densities

For vehicular

and costs.

This would

plete redesign of cell stacks, heat removal equipment,

applications, necessitate

it is a com-

etc.

Hydrogen Fuel and Alkaline Fuel Cells If pure hydrogen alkaline

phosphoric start-up

is fast.

from renewable

suitable

aspect

if advanced

gas

(100°C).

of the alkaline

facilities

for

problems,

the

hydrogen

As a result, cell is that

and rugged

power

Pure hydrogen may syngas

streams

are

in conjunction with inter-

such as solar or wind energy.

of this system are the CO 2 removal

fuel

in the structure

can be constructed.

separation

resources),

it does not require platinum

Another source of hydrogen is electrolysis sources

energy

(which is about the same as the

at low temperatures

An important

for mobile applications,

primary energy

refueling.

because

its rated power

steel parts can be incorporated

also be available developed.

and it delivers

acid fuel cell at 200oc) time

nickel plated

mittent

(e.g.,

fuel cell will be quite attractive

electrocatalysts

plants,

were available

storage

The disadvantages in the vehicle and

65 APPLICATIONS

SCENARIO

An applications economic

STUDY OF FUEL CELL POWERED VEHICLES

scenario

evaluation

of

study

(23),

potential

was recently carried out at Los Alamos cle types were evaluated:

between

cell/battery fuel

cell

cell,

each

in making

of

the

four

prove because

in

motor,

the

for these vehicles

The

late

It should

first-order

These

studies

cell/battery

Technical

studied.

economic

However, economic

suggested

and

Four vehi-

viability

more design,

in

the

and

fuel

feasibility

of

that no fuel

improvements

viability

since conservative

the

be emphasized

feasibility

Economic

and compari-

or diesel)

suggest

were

pro-

was demonstrated

was

of data on uniform vehicular

hybrid vehicles.

feasibility~

(LASL).

engine

performance

cle, and costs, as well as the lack of experience

sis,

technical

in transportation,

were gathered

strongly

aerodynamic

these assessments. vehicles

combustion

results

1990's.

or vehicle

of the scarcity

cular environment.

a detailed

of fuel cells

Scientific Laboratory

(internal

vehicles.

vehicles

battery,

jected

conventional

hybrid

included

city bus, highway bus, delivery van, and consumer car.

Typical drive cycles and economics sons made

which

applications

more

for

difficult

performance,

to

duty cy-

with fuel cells in the vehicu-

estimates were used in the analy1990's

development,

Since maintenance

time

frame

and testing

was

predicted.

programs

for fuel

plays a strong role in assessing

experience

with fuel cells

PERFORMANCE

CHARACTERISTICS

in vehicular

environments

must

be obtained.

PRESENT AND PROJECTED In Table tics

I are shown

the demonstrated

of fuel cell powered

passenger

the General Motors Electrovan

OF FUEL CELL POWERED VEHICLES

and projected

vehicles.

performance

The first

characteris-

case cited

with a Union Carbide Hydrogen-Oxygen

is that of

Alkaline

Fuel

Cell as the only power plant (24).

The fuel cell reactants were carried on board

the vehicle

The main drawbacks

as cryogenic

liquids.

of this vehicle

excessive weight of the power train and the long time for acceleration

were

the

from 0-I00

km/h. The first fuel cell/battery by Kordesch,

of a hydrogen-air stored

hybrid vehicle was designed,

while at Union Carbide alkaline

as compressed

gas

Corporation

(20).

developed

fuel cell and a lead acid battery. in five

small

cylinders.

and tested

The power plant consisted

The vehicle

The hydrogen was was

cruising at 70 km/h and the range with 1.6 kg of hydrogen was 300 km. cle was tested for a period of one year and the distance

capable

of

The vehi-

covered was 24,000 km.

66

TABLE I Demonstrated and Projected Performance Powered Vehicles

Power Train

Assessments

France State

by

GM Electrovan

Kordesch Car

H2/O 2 Fuel Cell

Fuel Cell/ Battery Hybrid H2-Air

Fuel Cell/ Battery Hybrid Methanol H2-Air/ Lead Acid

(25). Mines

32 160 3550 1765 Ii0 ---

6 22 910 320 90 65

30 -------

have been made

the

Institute

is engaged (26).

of the

expected

of French

Petrole

in a multi-million The technoe~onomic

Because opment,

expected and

60 kW

(ERC)

(27).

racteristics similar

of fuel

performance (for

dollar

program

to develop

at ELENCO

in

fuel

cell

reveal that the

will be with buses.

systems

were

made

The present pro-

The results of this study were used

in size to the Volkswagen

It is estimated

vehicles Rabbit

Research

in projecting

(Table I). was

vehicle.

vehi-

Corporation

performance

cha-

For this case, a vehicle

considered.

The

expected

perfor-

hybrid vehicle will match that of a diesel powered

that

of fuel utilization

state of devel-

of 15 kW (for passenger at Energy

the electric

vehicle

will

cost

than the diesel one and also exceed in weight by about 200 kg. ficiency

powered

Company

Belgian Nuclear Center and Dutch

assessments

and cost assessments

buses)

of fuel cell powered

fuel cell/battery

cell

Automobile

acid fuel cell is in the most advanced

mance of the fuel cell/battery vehicle.

performance

develop and test i0 kW alkaline fuel cells.

the phosphoric

cles)

14 I0 ii km/% -I, methanol

and Renault

of Bekaert,

first impact of fuel cell powered vehicles gram is to design,

15 35 1360 365 120 90

----40 km/kg, H2

ELENCO, a conglomerate

powered vehicles

of Fuel Cell

LASL-BNL-ERC Projections for Subcompact Car

Rated power, kW Peak power, kW Curb weight, kg Power train weight, kg Top speed, kmh -± Cruising speed, kmh -I Acceleration 0-I00 kmh -I, see 0- 50 kmh -I, sec Start-up time, min Fuel consumption

vehicles

Characteristics

and

maintenance

costs

are more

about

$3000 more

However, favorable

the effor

the

6?

OTHER CANDIDATE FUEL CELLS AND THEIR POTENTIAL APPLICATIONS There is only a low level of effort for the development trolyte

fuel cells,

system offers

and

nearly

this

the

too

same

is mainly

characteristics

system but suffers from the additional electrolyte

fuel cell development

of the emphasis on utilization several

European

era, alkaline Siemen A.G.,

and

Canadian

in West Germany,

alkaline

Kordesch,

vehicles

scientists,

is developing

fuel

(29).

ELENCO

However,

cell

in the nuclear,

because

to the views

solar

and

fusion

cells

for

to optimize

fuel

Such a system also shows value for stand-by in the design,

transportation

alkaline

alkaline

fuel

development

applications

(26).

There

with the assistance

cells

as power

sources

and testis

a

of Professor for

electrice

(30).

fuel cell.

Unfortunately,

applications

is the direct methanol-air

the power density is too low, at least by a factor of

The second problem is the poisoning of the fuel electrode,

intermediate Shell

fuel

particularly

according

a 7 kW hydrogen-oxygen

is engaged

The ideal fuel cell for transportation

six.

acid

This

of a high cost solid polymer

in the USA,

small effort at Brookhaven National Laboratory, K.V.

the phosphoric

(28).

fuel cells will have a distinct role in a Hydrogen Energy Scenario.

say in hospitals.

ing of

of solid polymer elec-

applications

problem.

has declined

of fossil fuels.

cell for military applications power,

as

disadvantages

and a difficult water management

Alkaline

of

for space

formed during methanol oxidation.

Research

Laboratories

in England

presumable

by an

There is a low level of effort at

to investigate

direct

methanol-air

fuel

cells (31). Practically from air)

all

fuel

cells,

as the cathodic

low temperature gen electrode. performance.

reactant.

fuel cells,

have

Laboratory,

General

Associates

Electric

use

losses,

oxygen

of chlorine

for oxygen

greatly

(pure

particularly

or

in the

at the oxy-

enhances

fuel cell

for an energy storage system utilizing a regenerative

Company,

and Gould,

such a system shows promise

developed,

The efficiency

fuel cell were examined

Development

been

are mainly due to the high overpotential

Substitution The prospects

hydrogen-halogen

which

in detail jointly by Brookhaven National

Oronzio

Inc.

(4).

de Nora,

Clarkson

The general

for coupling with intermittent

College,

conclusions energy

Energy

were

sources

that

(e.g.,

solar wind) or with remote nuclear power plants.

ACKNOWLEDGMENTS This review article was prepared under the auspices of the U.S. Department of Energy. The author wishes to express his gratitude to the following who have contributed directly or indirectly during the preparation of this article: Dr. J. McBreen of Brookhaven National Laboratory; Dr. J.B. McCormick of Los Alamos Scientific Laboratory; Professor K.V. Kordesch of the Technische Universitaet Graz, Austria; Dr. J.R. Huff of the U.S. Army Mobility Equipment Research and Development Center; Drs. B.S. Baker, L. Christner and H. Maru of Energy Research

68 Corporation; Dr. H.R. Kunz of United Technologies Corporation; Dr. A.O. Isenberg of Westinghouse Research and Development Center; Dr. J. Ackerman of Argonne National Laboratory; Drso M. Warshay and M. Lauver of NASA-Lewis Research Center; and Mr. M. Zlotnick of the U.S. Department of Energy.

REFERENCES i. 2. 3. 4. 5.

6. 7. 8. 9. I0. 11. 12. 13.

14. 15. 16. 17,

18. 19.

20. 21. 22. 23.

24. 25.

26.

27.

J. O'M. Bockris and S. Srinivasan, Fuel Cells: Their Electrochemistry, McGraw-Hill Publishing Company, New York, 1969. R. Noyes (Ed.), Fuel Cells for Public Utility and Industrial Power, Noyes Data Corporation, Park Ridge, New Jersey, 1977. J.B. McCormick, R.E. Bobbett, D.K. Lynn, S. Nelson, S. Srinivasan, J. McBreen, and J.R. Huff, IECEC Record, 1979, 61B. D-T. Chin, R.S. Yeo, J. McBreen and S. Srinivasan, J. Electrochem. Sot., 1979, 126, p. 713. H.R. Kunz in Proceedings of the Symposium on Electrode Materials and Processes for Energy Conversion and Storage, J.D.E. Mclntyre, S. Srinivasan and F.G. Will, Editors, The Electrochemical Society, Princeton, New Jersey, 1977, 77-6, p. 607. A.P. Fickett, ibid., p. 546. H.C. Maru, L.G. Christner, S.G. Abens, and B.S. Baker, National Fuel Cell Seminar Abstracts, Bethesda, Maryland, June 26-28, 1979, p. 86. W. Johnson, ibid., p. 82. K.F. Glasser, 1980 National Fuel Cell Seminar Abstracts, Ban Diego, CA, July 14-16, 1980, p. 6. L.M. Handley, Ref. 7, p. 73. B.S. Baker et al., Development of Phosphoric Acid Fuel Cell Technology, Final Report, Contract #EC-77-C-03-1404, U.S. Department of Energy, 1978. A. Kaufman, Ref. 7, p. 91. T.G. Benjamin, E.H. Camara and L.G. Marianowski, Handbook of Fuel Cell Performance, prepared on Contract #EC-77-C-03-1545, for U.S. Department of Energy by Institute of Gas Technology, 1980. H.R. Kunz, National Fuel Cell Seminar Abstracts, July 11-13, 1978, San Francisco, California, p. 96. A.O. Isenberg, Ref. 5, p. 572. A.O. Isenberg and R.J. Ruka, Ref. 7, p. 65. L.J. Olmer and H.S. Isaacs, "Impedance Characterization of the Solid Oxide Electrolyte Interface," to be presented at Fall Electrochemical Society Meeting, Hollywood, Florida, October, 1980. S. Srinivasan and H.S. Isaaes, Ref. 3, p. 568. J. McBreen, Proceedings of the Fuel Cells in Transportation Workshop, J.B. McCormick, R.E. Bobbett, S. Srinivasan, and J. McBreen, Editors, Los Alamos, New Mexico, 1978, p. 38. K.V. Kordesch, J. Electrochem. So¢. 118, 1971, p. 812. M.A. George, Ref. 7, p. 51. D.R. Crouse, Eco Inc., work in progress. J.B. McCormick, J.R. Huff, S. Srinivasan and R.E. Bobbett, Applications Scenario for Fuel Cells in Transportation, Los Alamos Scientific Laboratory, Los Alamos, New Mexico (LA-7634-MS), 1979. C. Marks, E.A. Rishavy and F.A. Wyczulek, Society of Automotive Engineers, Paper #670176, 1967. Y. Breele, J. Cheron, P. Degobert, and A. Grehier, Fuel Cells: Research and Development - Current Programs and Outlook, Institute of Francais Du Petrole Report PV No. 26-761A, 1979. H. Van den Broeck, M. Alfenaar, A. Hovestreydt, A. Blanchart, G. Van Bogaert, M. Bombeke and L. Van Pouce, Proceedings of the Second World Hydrogen Energy Conference, Vol. 4, 1979, p. 1959. B.S. Baker, M. Hooper, H.C. Maru, and D. Patel, System Study of Phosphoric Acid Fuel Cells for Transportation Applications, Final Report on Contract #450177-S for Brookhaven National Laboratory, 1978.

69 28. 29. 30. 31.

J. McEiroy, Ref. 19, p. 53. H. Grune, J. Electrochem. Soc., in press. J. McBreen, G. Kissel, K.V. Kordesch, F. Kulesa, E.J. Taylor, E. Gannon, and S. Srinivasan, IECEC Record, 1980, in press. B.D. McNicol, Proceedings of the Workshop on Electrocatalysis of Fuel Cell Reactions, W.E. O'Grady, S. Srlnivasan and R.F. Dudley, Editors, The Electrochemical Society, Inc., Princeton, New Jersey, Vol. 79-2, 1979, p. 93.