Applications for Fuel Cells

Applications For Fuel Cells
The third article in our series looks at the advantages and applications of fuel cells.
By Gerry Nolan
If hydrogen becomes the fuel of choice, what are the costs of manufacturing it and installing a
completely new fuel distribution system?
Experience has shown that we should ask these questions early in the deelopment of any new
technology, no matter how great it looks at first glance! "ooking at comparisons with existing
fuel systems, the hydrogen fuel cell certainly comes out ahead enironmentally!
#ig!$% comparision of carbon dioxode, nitrous oxides, sulphur dioxide and noise emissions
between the four main engine types! &s you can see, fuel cells win on eery measure!
#ig!$ shows clearly that hydrogen fuel cell technology is below diesel, gas turbine and petrol
engines with regard to '(
)
, N(
*
, +(
*
and noise emissions!
#ig!) shows a comparison between the oerall enironmental costs for existing internal
combustion engine technology ,I'E-, electric ehicle technology ,E.- and hydrogen fuel cell
technology ,/
)
#'-!
0hen all costs are considered% new technology costs, on1going upstream costs ,eg, fuel
production and distribution- and emission costs, particularly for ehicular applications, fuel cell
technology is ahead but it is not a clear1cut conclusion!
In his article on solar power in the 2arch )33) issue of +I"I'(N '/I4, 5oss 6ester concluded
that most people would not use solar cell technology, no matter how enironmentally desirable,
unless it meant lower monetary costs for them! 6here is little doubt that the same conclusion will
apply to the use of fuel cells!
Now let7s look at some of the applications of fuel cell technology!
8eelopments hae gone well beyond the prototype stage for seeral applications, particularly in
space! 0hen aircraft manufacturer 4ratt 9 0hitney won the contract to supply fuel cells for the
&pollo program in the early $:;3s, their fuel cell design was based on modifications to the
Bacon patents for alkaline fuel cells, which are the most efficient at low temperature!
#ig!)% the enironmental costs of new technology ersus old for internal combustion engines,
electric ehicles and hydrogen fuel cells! +mall wonder that fuel cells are regarded as the <green<
alternatie=
6hree units capable of producing $!>k0, or up to )!)k0 for short periods, were operated in
parallel! 0eighing around $$?kg per unit and fuelled with cryogenic hydrogen and oxygen, these
units ran for $3,333 hours during $@ missions without an in1flight incident!
&nd they produced all the fresh water for the space missions as well=
'ontinuing deelopment by International #uel 'ells ,which is a diision of A6', the company
that 490 became- has meant that the fuel cell stacks used on each shuttle can now proide
around ten times the power of similar1siBe units used in the &pollo craft!
#uelled by cryogenic hydrogen and oxygen the cells are C3D efficient and hae now completed
oer @3,333 operating hours in more than $33 missions! &nd there are no backup batteries!
#ollowing the space program success, fuel cells hae been used in%
&n installation of fie 4' )>62 fuel cells at &nchorage in &laska! 'ourtesy of International
#uel 'ells ""'
• +tationary power installations for utilities, factories, emergency power for hospitals,
communications facilities, credit card centres, police stations, banks and computer
installations
• 8ierse military applications
• 8omestic power supplies for indiidual residences
• 2obile phones, laptop computers and other personal electronic deices
• 6ransportation 1 particularly cars and buses but also in boats, trains, planes, scooters and
bicycles, as well as highway road signs
• 4ortable power for building sites, camping and ending machines!
• "andfills and waste water treatment plants ,which are using fuel cells to conert the
methane gas they produce into electricity-!
Energy supply systems based on fuel cells
5egardless of the type of fuel cell used, they all require a ariety of peripheral units to store or
conert fuel and conert the 8' power generated for &' applications! In addition, they need
pumps for fuel and air and entilation fans to remoe heat and water apour!
Now we7ll take a closer look at the way fuel cells fit into each of these arious energy system
applications!
#ig!E represents a generic system based on fuel cells which could be a large utility energy
system, a portable power supply or the power pack for a mobile phone 1 which may not need &'
but will still need power conditioning!
0hen we think <fuel cells<, until now we7e automatically tended to think <big<% space shuttles,
buses, cars and stationary power generation! But as these pictures show, fuel cells can be
downright miniscule= 6he two pictures at left show Fust how small fuel cells can be made ,yes,
that is a pencil=-! 6he third photo, courtesy 5oam4ower, shows a fuel cell1powered emergency
torch, while the fuel cell1powered notebook computer at right ,courtesy Ballard 4ower +ystems-
is a portent of commercial products planned for release as early as next year and the year after!
Stationary systems
#ig!E% for those who might hae missed our in1depth explanation earlier in this series, this
graphic shows the operation of a typical fuel cell system! (xygen ,from the air- and hydrogen
,from a hydrocarbon fuel- enter at left! 4ure hydrogen is extracted by the processor! Both
combine in the fuel cell,s- to form water, with a <byproduct< being a flow of electrons 1 or a 8'
current! 6his is then used, stored ,eg! by charging a battery-, or inerted to &'!
6hese fall roughly into the three categories% grid1connectedG back1up power supplies and
domestic installations!
&t the time of writing, more than )33 fuel cell systems hae been installed all oer the world in
hospitals, nursing homes, hotels, office buildings, schools and airport terminals! 6hey are either
being used to proide primary power or as a backup supply!
6he following examples are typical of stationary installations that hae been announced in the
last year%
In +eptember )33$, the town of 0oking, ?3km southwest of "ondon, became the first
community to sign up for a commercial fuel cell installation in the Anited Hingdom!
6hey contracted with A6' #uel 'ells for a )33k0 4')>62 system to proide electricity and
heat for the pool in 0oking 4ark recreational centre, as well as electricity to light the park!
In 8ecember )33$, A6' #uel 'ells announced that a 4')>62 fuel cell power plant had been
installed at #ord 2otor 'ompany7s North &merican 4remier &utomotie Group headquarters in
'alifornia! 6he )33k0 plant proides )>D of the building7s power as well as hot water for the
facility!
+iemens 4ower Generation Group will build a solid oxide fuel cell ,+(#'- power plant with a
maximum electrical capacity of )>3k0 in /anoer, Germany, to be completed by )33E!
#uel cells on ,small- wheels% the <2(II6( #'< fuel cell powered scooter showing the fuel cell
stack in the pannier! 6he hydrogen supply is under the pillion seat!
6he world7s first fuel cellJgas turbine hybrid power plant is now operating at the National #uel
'ell 5esearch 'enter in Irine, 'alifornia! 6he system features a +iemens 0esting1house solid
oxide fuel cell combined with an Ingersol 5and microturbine to produce approximately $:3k0
of electricity! Early test data show electrical efficiencies of approximately >ED, belieed to be a
world record for the operation of any fuel cell system on natural gas!
Improements in the technology could ultimately raise efficiencies to ;3D for smaller systems
and C3D or higher for larger systems!
Residential installations
&lthough mass production will be crucial to bring prices down to make domestic installations
practical, with large companies such as International #uel 'ells, Ballard 4ower and &ista "abs
becoming inoled, this will eentually happen!
From fuel processor...
2ost domestic systems hae a fuel processor as part of the fuel cell installation! 6his includes a
fuel reformer, which processes a hydrocarbon fuel such as natural gas, into a hydrogen1rich gas
known as reformate! & carbon monoxide ,'(- cleanup unit is necessary to reduce the high
concentrations of carbon monoxide produced in the process to acceptable leels ,under >3ppm-!
&t the heart of the fuel cell system is the 4E2 fuel cell stack, which is made up of a membrane
electrode assembly sandwiched between two gas diffusion layers with bipolar plates on each
side!
6he reformate ,hydrogen- from the '( cleanup system feeds the fuel side of the fuel cell and the
4E2 cell generates a 8' potential as described last month!
&t right is the fuel cell pack in a .olkswagen car!
6his is fed to the power conditioner which conerts the low1oltage 8' to high1oltage &'!
Batteries are usually used to ensure that the system copes with power surges from motor start1
ups or when peak demand exceeds the system output!
#uel cell systems, generally with ery quick start1up featured, seem to be ideal for primary
household supply and as back1up for peak or emergency use or for remote areas!
& ery attractie feature is that 7waste7 heat can be used to proide hot water or space heating in a
home! +ince fuel cells operate silently, they are highly preferable to the typical diesel generator
on rural properties!
2any of the prototypes being tried in residences use hydrogen extracted from propane or natural
gas!
Transportation
&s noted in the first article in this series, much of the deelopment work being carried out with
fuel cells is in the transportation industry! 2ore than $33,333 fuel cell powered ehicles are
expected on the world7s roads by )33?!
&s with the stationary fuel cell installations, peripherals are again required!
#ig!E is a schematic of the main components! 0ith wheel1mounted electric motors, fuel cell
technology allows great flexibility in the placement of the arious components!
&ll of the maFor automotie manufacturers now hae at least one fuel cell ehicle under
deelopment, including /onda, 6oyota, 8aimler1'hrysler, G2, #ord, /yundai, Nissan,
.olkswagen and B20!
5esearch has shown that the amount of carbon dioxide produced from a small car can be reduced
by as much as C)D when powered by a fuel cell running on hydrogen reformed from natural gas
instead of a conentional internal combustion engine!
/oweer, it is not enough for the technology to meet tighter legislation on ehicle emissions! It
must also proide transport that offers equialent conenience and flexibility!
#ig!?% schematic diagram of the main components of a fuel cell system in a car with electric
motors driing the front wheels, or the rear wheels, independently!
Being able to reach operating temperature rapidly, proide competitie fuel economy and gie a
responsie performance are all considerations that make the proton exchange membrane ,4E2-
fuel cells the faourite!
6hey reach operating temperature ,around @33K'- quickly and respond rapidly to arying loads,
as well as offering efficiency of up to ;3D, compared to the )>D ,at best- achieed by internal
combustion engines!
4E2 fuel cells also hae the highest power density, which is crucial in modern ehicle design,
and the solid polymer electrolyte helps to minimise potential corrosion and safety management
problems!
/oweer, to aoid catalyst poisoning at this low operating temperature ,4E2 fuel cells do need
an uncontaminated hydrogen fuel!
+till, most maFor ehicle manufacturers regard the 4E2 fuel cell as the eentual successor to the
internal combustion engine!
Scooters & bicycles
2anhattan +cientifics and &prilia uneiled a fuel cell powered concept scooter at the
International 4aris #air in &pril this year! 'alled <2(II6( #',< the scooter is powered by
2anhattan +cientifics7 hydrogen fuelled Ek0 fuel cell!
It is expected that production models will hae a range of nearly )33km and a top speed of at
least ;3km an hour!
6he fuel cell system, including all electronics, ales and fans, weighs slightly less than ;kg,
with the fuel essel weighing only ?!Ekg!
2anhattan +cientifics beliees fuel cell scooters with optimised drie systems will achiee a
higher top speed and quicker acceleration than current ehicles with >3cc and @3cc internal
combustion engines!
2anhattan +cientifics and &prilia preiously deeloped the &prilia ENI(L #', a concept fuel
cell powered bicycle which receied one of 6ime 2agaBine7s )33$ <Inentions of the Lear<
awards!
ortable fuel cell po!er
& 4lug 4ower Ck0 residential 4E2 domestic fuel cell installation! 4lug 4ower has been testing
the aboe unit in a home since $::@! 8etroit Edison co1founded the company and General
Electric agreed in $::: to distribute and serice 4lug 4ower cells! +uch support has boosted
expectations of a commercial introduction of the domestic fuel cell this year!
In the not1too1distant1future, miniature fuel cells will enable people to talk for up to a month on a
mobile phone without recharging the battery! 2iniature fuel cells will also power laptops and
4alm 4ilots for many hours longer than batteries can!
8irect methanol fuel cells powering mobile phones hae already been tested and the 'asio
'omputer 'ompany intends to begin selling methanol fuel cells from )33?!
6hese cells will be able to continuously power a laptop computer for as long as )3 hours,
compared with about E1> hours from batteries!
6he methanol fuel for its fuel cells is expected to cost about E3 cents per litre, which sounds
incredibly cheap when you consider the siBe of the unit that will be using it!
"andfill treatment
Fuell cel; application
6here are many uses for fuel cells M right now, all of the maFor automakers are working to
commercialiBe a fuel cell car! #uel cells are powering buses, boats, trains, planes, scooters,
forklifts, een bicycles! 6here are fuel cell1powered ending machines, acuum cleaners and
highway road signs! 2iniature fuel cells for cellular phones, laptop computers and portable
electronics are on their way to market! /ospitals, credit card centers, police stations, and banks
are all using fuel cells to proide power to their facilities! 0astewater treatment plants and
landfills are using fuel cells to conert the methane gas they produce into electricity!
6elecommunications companies are installing fuel cells at cell phone, radio and :$$ towers! 6he
possibilities are endless!
#or monthly updates on the latest fuel cell deelopments in all applications, sign1up ,use the box
to the far right of this page- to receie #uel 'ells )3337s monthly technology updates ia email!
+tationary
2ore than )>33 fuel cell systems hae been installed all oer the world M in hospitals, nursing
homes, hotels, office buildings, schools, utility power plants 1 either connected to the electric
grid to proide supplemental power and backup assurance for critical areas, or installed as a grid1
independent generator for on1site serice in areas that are inaccessible by power lines!
#uel cell power generation systems in operation today achiee #$ percent
fuel1to1electricity efficiency utiliBing hydrocarbon fuels! +ince fuel cells
operate silently, they reduce noise pollution as well as air pollution and
when the fuel cell is sited near the point of use, its waste heat can be
captured for beneficial purposes ,cogeneration-! In large1scale building
systems, these fuel cell cogeneration systems can reduce facility energy
serice costs by )3D to ?3D oer conentional energy serice and increase efficiency to @>
percent! 'heck out our database of worldwide stationary fuel cell installations!


6elecommunications 1 0ith the use of computers, the Internet, and
communication networks steadily increasing, there comes a need for more
reliable power than is aailable on the current electrical grid, and fuel cells hae
proen to be up to ::!:::D ,fie nines- reliable! #uel cells can replace batteries
to proide power for $k0 to >k0 telecom sites without noise or emissions, and
are durable, proiding power in sites that are either hard to access or are subFect
to inclement weather! +uch systems would be used to proide primary or
backup power for telecom switch nodes, cell towers, and other electronic
systems that would benefit from on1site, direct 8' power supply!




"andfillsJ0astewater 6reatment 4lantsJBreweriesJ%ineries1 #uel cells
currently operate at landfills and wastewater treatment plants across the
country, proing themseles as a alid technology for reducing emissions
and generating power from the methane gas they produce! 6hey are also
installed at seeral breweries and a winery1 +ierra Neada, Hirin, &sahi and
+apporo and Napa 0ine 'ompany! Antreated brewery effluent can undergo
anaerobic digestion, which breaks down organic compounds to generate methane, a hydrogen
rich fuel!

6ransportation
'ars 1 &ll the maFor automotie manufacturers hae a fuel cell ehicle either in
deelopment or in testing right now, and seeral hae begun leasing and testing
in larger quantities! 'ommercialiBation is a little further down the line ,some
automakers say )3$), others later-, but eery demonstration helps bring that date
closer! 'heck out our page on &enefits for Transportation and for a comprehensie chart
showcasing all the fuel cell ehicles eer demonstrated, isit our Charts page!

Buses 1 (er the last four years, more than >3 fuel cell buses hae been
demonstrated in North and +outh &merica, Europe, &sia and &ustralia! #uel
cells are highly efficient, so een if the hydrogen is produced from fossil fuels,
fuel cell buses can reduce transit agenciesN '() emissions! &nd emissions are
truly Bero if the hydrogen is produced from renewable electricity, which greatly
improes local air quality! Because the fuel cell system is so much quieter than a
diesel engine, fuel cell buses significantly reduce noise pollution as well! #or a comprehensie
chart on fuel cell buses, click here!


+cooters 1 In spite of their small siBe, many scooters are pollution powerhouses!
Gas1powered scooters, especially those with two1stroke engines, produce
tailpipe emissions at a rate disproportionate to their small siBe! 6hese two1stroke
scooters produce almost as much particulate matter and significantly more
hydrocarbons and carbon monoxide as a heay diesel truck! #uel cell scooters
running on hydrogen will eliminate emissions 1 in India and &sia where many of
the population use them 1 this is a great application for fuel cells!


#orkliftsJ2aterials /andling 1 Besides reducing emissions, fuel cell forklifts
hae potential to effectiely lower total logistics cost since they require minimal
refilling and significantly less maintenance than electric forklifts, whose batteries
must be periodically charged, refilled with water, and replaced! 8ue to the
frequent starting and stopping during use, electric forklifts also experience
numerous interruptions in current input and output 1 fuel cells ensure constant power deliery
and performance, eliminating the reduction in oltage output that occurs as batteries discharge!

&uxiliary 4ower Anits ,&4As- 1 6odayNs heay1duty trucks are equipped with
a large number of electrical appliancesOfrom heaters and air conditioners to
computers, teleisions, stereos, een refrigerators and microwaes! 6o power
these deices while the truck is parked, driers often must idle the engine! 6he
8epartment of Energy ,8(E- has estimated the annual fuel and maintenance
costs of idling a heay1duty truck at oer P$,@33 and that using fuel cell &4As
in 'lass @ trucks would sae ;C3 million gallons of diesel fuel per year and
?!;? million tons of '() per year!




6rains 1 #uel cells are being deeloped for mining locomoties since they
produce no emissions! &n international consortium is deeloping the worldNs
largest fuel cell ehicle, a $3: metric1ton, $ 20 locomotie for military and
commercial railway applications!



4lanes 1 #uel cells are an attractie option for aiation since they produce Bero
or low emissions and make barely any noise! 6he military is especially
interested in this application because of the low noise, low thermal signature and ability to attain
high altitude! 'ompanies like Boeing are heaily inoled in deeloping a fuel cell plane!



Boats 1 #or each liter of fuel consumed, the aerage outboard motor produces
$?3 times the hydrocarbonss produced by the aerage modern car! #uel cell
engines hae higher energy efficiencies than combustion engines, and
therefore offer better range and significantly reduced emissions! Iceland has
committed to conerting its ast fishing fleet to use fuel cells to proide
auxiliary power by )3$> and, eentually, to proide primary power in its
boats!



#or more information on the latest demonstrations and to see which companies are working on
fuel cells for specialty ehicles, check out our chart!
4ortable 4ower
#uel cells can proide power where no electric grid is aailable, plus they are
quiet, so using one instead of a loud, polluting generator at a campsite would
not only sae emissions, but it won7t disturb nature, or your camping
neighbors! 4ortable fuel cells are also being used in emergency backup
power situations and military applications! 6hey are much lighter than
batteries and last a lot longer, especially imporant to soldiers carrying heay
equipment in the field!


2icro 4ower
'onsumer Electronics1 #uel cells will change the telecommuting world,
powering cellular phones, laptops and palm pilots hours longer than batteries!
'ompanies hae already demonstrated fuel cells that can power cell phones
for E3 days with out recharging and laptops for )3 hours! (ther applications
for micro fuel cells include pagers, ideo recorders, portable power tools, and low power remote
deices such as hearing aids, smoke detectors, burglar alarms, hotel locks and meter readers!
6hese miniature fuel cells generally run on methanol, an inexpensie wood alcohol also used in
windshield wiper fluid!
11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
1
Fuel Cell Basics
Through this website we are seeking historical materials relating to fuel cells. We have
constructed the site to gather information from people already familiar with the
technology–people such as inventors, researchers, manufacturers, electricians, and
marketers. This Basics section presents a general overview of fuel cells for casual
visitors.
What is a fuel cell? How do fuel cells work?
Why can’t I go out and buy a fuel cell?
Different types of fuel cells.

What is a fuel cell?
A fuel cell is a device that generates electricity by a chemical reaction. very fuel cell
has two electrodes, one positive and one negative, called, respectively, the anode and
cathode. The reactions that produce electricity take place at the electrodes.
very fuel cell also has an electrolyte, which carries electrically charged particles from
one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.
!ydrogen is the basic fuel, but fuel cells also re"uire o#ygen. $ne great appeal of fuel
cells is that they generate electricity with very little pollution%much of the hydrogen and
o#ygen used in generating electricity ultimately combine to form a harmless byproduct,
namely water.
$ne detail of terminology& a single fuel cell generates a tiny amount of direct current
'()* electricity. +n practice, many fuel cells are usually assembled into a stack. )ell or
stack, the principles are the same.
Top
!ow do fuel cells work?
The purpose of a fuel cell is to produce an electrical current that can be directed outside
the cell to do work, such as powering an electric motor or illuminating a light bulb or a
city. Because of the way electricity behaves, this current returns to the fuel cell,
completing an electrical circuit. 'To learn more about electricity and electric power, visit
,Throw The -witch. on the -mithsonian website /owering a 0eneration of )hange.*
The chemical reactions that produce this current are the key to how a fuel cell works.
There are several kinds of fuel cells, and each operates a bit differently. But in general
terms, hydrogen atoms enter a fuel cell at the anode where a chemical reaction strips
them of their electrons. The hydrogen atoms are now ,ioni1ed,. and carry a positive
electrical charge. The negatively charged electrons provide the current through wires to
do work. +f alternating current 'A)* is needed, the () output of the fuel cell must be
routed through a conversion device called an inverter.
0raphic by 2arc 2arshall, -chat1 nergy 3esearch )enter
$#ygen enters the fuel cell at the cathode and, in some cell types 'like the one
illustrated above*, it there combines with electrons returning from the electrical circuit
and hydrogen ions that have traveled through the electrolyte from the anode. +n other
cell types the o#ygen picks up electrons and then travels through the electrolyte to the
anode, where it combines with hydrogen ions.
The electrolyte plays a key role. +t must permit only the appropriate ions to pass
between the anode and cathode. +f free electrons or other substances could travel
through the electrolyte, they would disrupt the chemical reaction.
Whether they combine at anode or cathode, together hydrogen and o#ygen form water,
which drains from the cell. As long as a fuel cell is supplied with hydrogen and o#ygen,
it will generate electricity.
ven better, since fuel cells create electricity chemically, rather than by combustion,
they are not sub4ect to the thermodynamic laws that limit a conventional power plant
'see ,)arnot 5imit. in the glossary*. Therefore, fuel cells are more efficient in e#tracting
energy from a fuel. Waste heat from some cells can also be harnessed, boosting
system efficiency still further.
Top
-o why can6t + go out and buy a fuel cell?
The basic workings of a fuel cell may not be difficult to illustrate. But building
ine#pensive, efficient, reliable fuel cells is a far more complicated business.
-cientists and inventors have designed many different types and si1es of fuel cells in
the search for greater efficiency, and the technical details of each kind vary. 2any of the
choices facing fuel cell developers are constrained by the choice of electrolyte. The
design of electrodes, for e#ample, and the materials used to make them depend on the
electrolyte. Today, the main electrolyte types are alkali, molten carbonate, phosphoric
acid, proton e#change membrane '/2* and solid o#ide. The first three are li"uid
electrolytes7 the last two are solids.
The type of fuel also depends on the electrolyte. -ome cells need pure hydrogen, and
therefore demand e#tra e"uipment such as a ,reformer. to purify the fuel. $ther cells
can tolerate some impurities, but might need higher temperatures to run efficiently.
5i"uid electrolytes circulate in some cells, which re"uires pumps. The type of electrolyte
also dictates a cell6s operating temperature–,molten. carbonate cells run hot, 4ust as the
name implies.
ach type of fuel cell has advantages and drawbacks compared to the others, and none
is yet cheap and efficient enough to widely replace traditional ways of generating power,
such coal8fired, hydroelectric, or even nuclear power plants.
The following list describes the five main types of fuel cells. 2ore detailed information
can be found in those specific areas of this site.
Top
(ifferent types of fuel cells.
lkali fuel cells operate on compressed
hydrogen and o#ygen. They generally use
a solution of potassium hydro#ide
'chemically, 9$!* in water as their
electrolyte. fficiency is about :; percent,
and operating temperature is <=; to >;;
degrees ), 'about ?;; to @;; degrees A*.
)ell output ranges from ?;; watts 'W* to =
kilowatts 'kW*. Alkali cells were used in
Apollo spacecraft to provide both electricity
and drinking water. They re"uire pure
hydrogen fuel, however, and their platinum
electrode catalysts are e#pensive. And like any container filled with li"uid, they can leak.
!olten Carbonate fuel cells '2)A)* use
high8temperature compounds of salt 'like
sodium or magnesium* carbonates
'chemically, )$?* as the electrolyte.
fficiency ranges from B; to C; percent,
and operating temperature is about B=;
degrees ) '<,>;; degrees A*. Dnits with
output up to > megawatts '2W* have been
constructed, and designs e#ist for units up
to <;; 2W. The high temperature limits
damage from carbon mono#ide EpoisoningE
of the cell and waste heat can be recycled
to make additional electricity. Their nickel
electrode8catalysts are ine#pensive
compared to the platinum used in other
cells. But the high temperature also limits
the materials and safe uses of 2)A)s%they would probably be too hot for home use.
Also, carbonate ions from the electrolyte are used up in the reactions, making it
necessary to in4ect carbon dio#ide to compensate.
"hosphoric cid fuel cells '/AA)* use phosphoric acid as the electrolyte. fficiency
ranges from @; to C; percent, and operating temperature is between <=; to >;;
degrees ) 'about ?;; to @;; degrees A*. #isting phosphoric acid cells have outputs up
to >;; kW, and << 2W units have been tested. /AA)s tolerate a carbon mono#ide
concentration of about <.= percent, which broadens the choice of fuels they can use. +f
gasoline is used, the sulfur must be removed. /latinum electrode8catalysts are needed,
and internal parts must be able to withstand the corrosive acid.
(rawing of an alkali cell.
(rawing of a molten carbonate cell
(rawing of how both phosphoric acid and /2 fuel
cells operate.
"roton #$change !e%brane '/2* fuel cells work with a polymer electrolyte in the
form of a thin, permeable sheet. fficiency is about @; to =; percent, and operating
temperature is about C; degrees ) 'about <:= degrees A*. )ell outputs generally range
from =; to >=; kW. The solid, fle#ible electrolyte will not leak or crack, and these cells
operate at a low enough temperature to make them suitable for homes and cars. But
their fuels must be purified, and a platinum catalyst is used on both sides of the
membrane, raising costs.
&olid '$ide fuel cells '-$A)* use a hard,
ceramic compound of metal 'like calcium or
1irconium* o#ides 'chemically, $>* as
electrolyte. fficiency is about B; percent,
and operating temperatures are about
<,;;; degrees ) 'about <,C;; degrees A*.
)ells output is up to <;; kW. At such high
temperatures a reformer is not re"uired to
e#tract hydrogen from the fuel, and waste
heat can be recycled to make additional
electricity. !owever, the high temperature
limits applications of -$A) units and they
tend to be rather large. While solid
electrolytes cannot leak, they can crack.
2ore detailed information about each fuel cell type, including histories and current
applications, can be found on their specific parts of this site. We have also provided a
glossary of technical terms–a link is provided at the top of each technology page.
Top
(rawing of a solid o#ide cell
F>;;C -mithsonian +nstitution
')opyright -tatemen

Lou can read more about each of these applications by going to our Fuel Cell "ibrary or
browse through our gallery of fuel cell images!
-------------------------------------------------------------------------------------------------------------------------------
-----------