Fuel Battery (2)

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Fuel cell

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For other uses, seeFuel cell (disambiguation).

Direct-methanol fuel cell. The actual fuel cell stack is the layered cube shape in the center ofthe image

A fuel cell is an electrochemical conversion device. It produces electricity fromfuel (on the

anode side) and an oxidant (on the cathode side), which react in the presence of anelectrolyte. The reactants flow into the cell, and the reaction products flow out of it, while theelectrolyte remains within it. Fuel cells can operate virtually continuously as long as thenecessary flows are maintained.

Fuel cells are different from electrochemical cellbatteries in that they consume reactant froman external source, which must be replenished[1] a thermodynamically open system. By

contrast, batteries store electrical energy chemically and hence represent athermodynamically closed system.

Many combinations of fuels and oxidants are possible. A hydrogen fuel cell uses hydrogen asits fuel and oxygen (usually from air) as its oxidant. Other fuels include hydrocarbons andalcohols. Other oxidants include chlorine and chlorine dioxide.[2]

The principle of the fuel cell had been demonstrated bySir William Grove in 1839, and otherinvestigators had experimented with various forms of fuel cell. The first practical fuel cellwas developed by Francis Thomas Bacon in 1959[citation needed].


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Contents

[hi

y 1 Fuel cell desi o

1.1 Proton exchange fuel cellso 1.2 Oxygen ion exchange fuel cellso 1.3 Proton exchange membrane fuel cell design issues

y 2 Historyy 3 Types of fuel cellsy 4 Efficiency

o 4.1 Fuel cell efficiencyo 4.2 In practice

y 5 Fuel cellapplicationso 5.1 Suggested applicationso 5.2 Hydrogen transportation and refuelingo 5.3 Market structure

y 6 Hydrogen economyy 7 Researchand developmenty 8 See alsoy 9 Referencesy 10 Externallinksy 11 Further reading

[edit] Fuel cell design

A fuel cell works by catalysis, separating the componentelectronsandprotons ofthe reactant

fuel, and forcing the electrons to travelthroughacircuit, hence converting them to electricalpower. The catalysttypically comprises aplatinum group metal oralloy. Another catalyticprocess puts the electrons backin, combining them withthe protons and oxidantto form

waste products (typically simple compounds like waterand carbon dioxide).

A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load. Voltagedecreases as currentincreases, due to several factors:

y Activation lossy Ohmic loss (voltage drop due to resistance ofthe cell components and interconnects)y Mass transportloss (depletion of reactants at catalyst sites underhighloads, causing

rapid loss of voltage)[3]

To deliverthe desired amount of energy, the fuel cells can be combined in series and parallelcircuits, where series yields highervoltage, and parallelallows a strongercurrentto bedrawn. Sucha design is called afuel ell t k. Further, the cell surface area can be increased,to allow strongercurrent from each cell.

[edit] Proton exchange uel cells


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In the archetypal hydrogenoxygenproton exchange membrane fuel cell (PEMFC) design, aproton-conducting polymer membrane, (theelectrolyte), separates the anode and cathodesides. This was called a "solid polymer electrolyte fuel cell" (SPEFC) in the early 1970s,

before the proton exchange mechanism was well-understood. (Notice that "polymer

electrolyte membrane" and "proton exchange mechanism" result in the sameacronym.)

On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates intoprotons and electrons. These protons often react with oxidants causing them to become whatis commonly referred to as multi-facilitated proton membranes (MFPM). The protons areconducted through the membrane to the cathode, but the electrons are forced to travel in anexternal circuit (supplying power) because the membrane is electrically insulating. On thecathode catalyst, oxygen molecules react with the electrons (which have traveled through theexternal circuit) and protons to form water in this example, the only waste product, eitherliquid orvapor.

In addition to this pure hydrogen type, there arehydrocarbon fuels for fuel cells, includingdiesel, methanol (see:direct-methanol fuel cells and indirect methanol fuel cells) andchemical hydrides. The waste products with these types of fuel arecarbon dioxide and water.

Construction of a high temperaturePEMFC: Bipolar plate as electrode with in-milled gaschannel structure, fabricated from conductiveplastics (enhanced with carbon nanotubes formore conductivity); Porous carbon papers; reactive layer, usually on thepolymermembraneapplied; polymer membrane.


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Condensation of water produced by a PEMFC on the air channel wall. The gold wire aroundthe cell ensures the collection of electric current.[4]

The materials used in fuel cells differ by type. In a typical membrane electrode assembly(MEA), the electrodebipolarplates are usually made ofmetal, nickel orcarbon nanotubes,

and are coated with a catalyst (likeplatinum, nano iron powders orpalladium) for higherefficiency. Carbon paperseparates them from the electrolyte. The electrolyte could beceramic or a membrane.

[edi Oxygen i n exchange fuel cells

In a solid oxide fuel cell (SOFC) design, the anode and cathode are separated by anelectrolyte that is conductive to oxygen ions but non-conductive to electrons. The electrolyteis typically made from zirconia doped with yttria.

On the cathode side, oxygen catalytically reacts with a supply of electrons to become oxygenions, which diffuse through the electrolyte to the anode side. On the anode side, the oxygenions react with hydrogen to form water and free electrons. A load connected externally

between the anode and cathode completes the electrical circuit.

Molten carbonate fuel cells (MCFCs) operate in a similar manner, except the electrolyteconsists of liquid (molten) carbonate, which is a negative ion and an oxidizing agent. Becausethe electrolyte loses carbonate in the oxidation reaction, the carbonate must be replenishedthrough some means. This is often performed by recirculating the carbon dioxide from theoxidation products into the cathode where it reacts with the incoming air and reformscarbonate.

Unlike proton exchange fuel cells, the catalysts in SOFCs and MCFCs are not poisoned by

carbon monoxide, due to much higher operating temperatures. Because the oxidation reactionoccurs in the anode, direct utilization of the carbon monoxide is possible. Also, steamproduced by the oxidation reaction canshift carbon monoxide and steam reform hydrocarbonfuels inside the anode. These reactions can use the same catalysts used for theelectrochemical reaction, eliminating the need for an external fuel reformer.

[edi Proton exchange membrane fuel cell design issues

y Costs. In 2002, typical fuel cell systems cost US$1000 per kilowatt of electric poweroutput. In 2008, the Department of Energy reported that fuel cell system costs involume production are $73 per kilowatt.[citation needed] The goal is $35 per kilowatt. In2008 UTC Power has 400 kW stationary fuel cells for $1,000,000 per 400 kW

installed costs. The goal is to reduce the cost in order to compete with current markettechnologies including gasoline internal combustion engines.Many companies areworking on techniques to reduce cost in a variety of ways including reducing theamount of platinum needed in each individual cell. Ballard Power Systems haveexperiments with a catalyst enhanced with carbon silkwhich allows a 30% reduction(1 mg/cm to 0.7 mg/cm ) in platinum usage without reduction in performance.

[5].

Monash University, Melbourne uses PEDOT instead of platinum.[6]


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y The production costs of the PEM (proton exchange membrane). TheNafionmembrane currently costs $565.92/m . In 2005 Ballard Power Systems announcedthat its fuel cells will use Solupor, a porouspolyethylene film patented by DSM.[7][8]

y Water and air management[9] (in PEMFCs). In this type of fuel cell, the membranemust be hydrated, requiring water to be evaporated at precisely the same rate that it is

produced. If water is evaporated too quickly, the membrane dries, resistance across it

increases, and eventually it will crack, creating a gas "short circuit" where hydrogenand oxygen combine directly, generating heat that will damage the fuel cell. If the

water is evaporated too slowly, the electrodes will flood, preventing the reactantsfrom reaching the catalyst and stopping the reaction. Methods to manage water in

cells are being developed like electroosmotic pumps focusing on flow control. Just asin a combustion engine, a steady ratio between the reactant and oxygen is necessary tokeep the fuel cell operating efficiently.

y Temperature management. The same temperature must be maintained throughout thecell in order to prevent destruction of the cell throughthermal loading. This is

particularly challenging as the 2H2 + O2 -> 2H2O reaction is highly exothermic, so alarge quantity of heat is generated within the fuel cell.

y Durability, service life, and special requirements for some type of cells.Stationaryfuel cell applications typically require more than 40,000 hours of reliable operation ata temperature of -35 C to 40 C (-31 F to 104 F), while automotive fuel cellsrequire a 5,000 hour lifespan (the equivalent of 150,000 miles) under extremetemperatures. Current service life is 7,300 hours under cycling conditions

[10].

Automotive engines must also be able to start reliably at -30 C (-22 F) and have ahigh power to volume ratio (typically 2.5 kW per liter).

y Limited carbon monoxide tolerance of the cathode.

[edit] History

Main article: Timeline ofhydrogen technologies

Sketch of William Grove's 1839 fuel cell

The principle of the fuel cell was discovered by German scientist Christian FriedrichSchnbein in 1838 and published in one of the scientific magazines of the time.[11] Based onthis work, the first fuel cell was demonstrated by Welsh scientist and barrister SirWilliamRobert Grove in the February 1839 edition of thePhilosophicalMagazine and Journal ofScience

[12]and later sketched, in 1842, in the same journal.

[13]The fuel cell he made used

similar materials to today'sphosphoric-acid fuel cell.


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fuel cell (ionomer) 100 kW (PBI)125200

System:2540%

rch

Direct-

ethanol

fuel cell

Polymermembrane(ionomer)

up to140 mW/c

m

above 25

? 90120Research

Proton

exchange

membrane

fuel cell

Polymermembrane

(ionomer) (e.g.,Nafion or

Polybenzimidazole fiber)

100 W to500 kW

(Nafion)50120

(PBI)125220

Cell:5070%

System:3050%

Commercial/Research

$3035

perwatt

RFC -

Redox

Liquidelectrolytes withredox shuttle &

polymermembrane(Ionomer)

1 kW to 10MW

Research

Phosphoric

acid fuel

cell

Moltenphosphoric acid

(H3PO4)

up to 10MW

150-200

Cell:55%

System:40%

Co-Gen:90%

Commercial/Research

$4$4.50 per

watt

Molten

carbonate

fuel cell

Molten alkalinecarbonate (e.g.,

sodiumbicarbonateNaHCO3)

100 MW 600-650

Cell:55%

System:47%

Commercial/Research

Tubularsolid oxide

fuel cell

(TSOFC)

O2-

-conductingceramic oxide

(e.g., zirconiumdioxide, ZrO2)

up to 100MW

850-1100Cell:60

65%System:5560%

Commercial/Research

Protonic

ceramic

H+-conductingceramic oxide

700 Research


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fuel cell

Direct

carbon fuel

cell

Several different 700-850

Cell:80%

System:70%

Commercial/Research

Planar

Solid oxide

fuel cell

O2-

-conductingceramic oxide

(e.g., zirconiumdioxide, ZrO2Lanthanum

Nickel OxideLa2XO4,X=

Ni,Co, Cu.)

up to 100MW

850-1100

Cell:6065%

System:5560%

Commercial/Research

Enzymatic

Biofuel

Cells

Any that willnot denature theenzyme (usuallyaqueousbuffer).

under40 Research

[edit] Efficiency

[edit] Fuel cell efficiency

The efficiency ofa fuel cellis dependent on the amount of power drawn from it. Drawingmore power means drawing more current, whichincreases the losses in the fuel cell. As ageneral rule, the more power (current) drawn, the lowerthe efficiency. Mostlosses manifestthemselves as a voltage drop in the cell, so the efficiency ofa cellis almost proportionalto itsvoltage. Forthis reason, itis common to show graphs of voltage versus current (so-called

polarization curves) for fuel cells. A typical cell running at 0.7 V has an efficiency ofabout50%, meaning that50% ofthe energy content ofthe hydrogen is converted into electricalenergy;the remaining 50% will be converted into heat. (Depending on the fuel cell systemdesign, some fuel mightleave the system unreacted, constituting an additionalloss.)

Forahydrogen cell operating at standard conditions with no reactantleaks, the efficiency is

equalto the cell voltage divided by 1.48 V, based on the enthalpy, orheating value, ofthereaction. Forthe same cell, the second law efficiencyis equalto cell voltage divided by 1.23V. (This voltage varies with fuel used, and quality and temperature ofthe cell.) Thedifference between these numbers represents the difference between the reaction's enthalpyand Gibbs free energy. This difference always appears as heat, along withany losses inelectrical conversion efficiency.

Fuel cells do not operate on athermal cycle. As such, they are not constrained, as combustionengines are, in the same way by thermodynamic limits, suchas Carnot cycle efficiency. At


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times this is misrepresented by saying that fuel cells are exempt from the laws ofthermodynamics, because most people think ofthermodynamics in terms of combustion

processes (enthalpy of formation). The laws ofthermodynamics also hold for chemicalprocesses (Gibbs free energy) like fuel cells, butthe maximum theoretical efficiency is higher

(83% efficientat 298K[16]

) than the Otto cyclethermal efficiency (60% for compression ratioof 10 and specific heat ratio of 1.4). Comparing limits imposed by thermodynamics is nota

good predictor of practically achievable efficiencies. Also, if propulsion is the goal, electricaloutput ofthe fuel cellhas to still be converted into mechanical power withthe correspondinginefficiency. In reference to the exemption claim, the correct claim is thatthe "limitationsimposed by the second law ofthermodynamics on the operation of fuel cells are muchlesssevere than the limitations imposed on conventional energy conversion systems".[17]Consequently, they can have very high efficiencies in converting chemical energytoelectrical energy, especially when they are operated atlow power density, and using purehydrogen and oxygen as reactants.

[edit] In practice

Fora fuel cell operating on air (ratherthan bottled oxygen), losses due to the air supplysystem mustalso be taken into account. This refers to the pressurization ofthe airanddehumidifying it. This reduces the efficiency significantly and brings it nearto that ofacompression ignition engine. Furthermore fuel cell efficiency decreases as load increases.

The tank-to-wheel efficiency ofafuel cell vehicleis about45% atlow loads and showsaverage values ofabout 36% when a driving cycle like the NEDC (New European DrivingCycle) is used as test procedure.[18] The comparable NEDC value fora Diesel vehicle is 22%.In 2008 Honda released a car (the Honda FCX Clarity) with fuel stack claiming a60% tank-to-wheel efficiency [19].

Itis also importantto take losses due to fuel production, transportation, and storage into

account. Fuel cell vehicles running on compressed hydrogen may have a power-plant-to-wheel efficiency of 22% ifthe hydrogen is stored as high-pressure gas, and 17% ifitis storedas liquid hydrogen.[20] In addition to the production losses, over70% of US' electricity usedforhydrogen production comes from thermal power, which only has an efficiency of 33% to48%, resulting in a netincrease in carbon dioxide production by using hydrogen invehicles

[cit ti eeded].

Fuel cells cannot store energy like a battery, butin some applications, suchas stand-alonepower plants based on discontinuous sources suchas solarorwind power, they are combinedwithelectrolyzersand storage systems to form an energy storage system. The overallefficiency (electricity to hydrogen and backto electricity) of such plants (known as round-tri efficiency) is between 30 and 50%, depending on conditions.[21] While a much cheaper

lead-acid battery might return about90%, the electrolyzer/fuel cell system can storeindefinite quantities ofhydrogen, and is therefore better suited forlong-term storage.

Solid-oxide fuel cells produce exothermic heat from the recombination ofthe oxygen andhydrogen. The ceramic can run as hotas 800 degrees Celsius. This heat can be captured andused to heat waterin amicro combined heatand power(m-CHP) application. When the heatis captured, total efficiency can reach80-90% atthe unit, but does not consider productionand distribution losses. CHP units are being developed today forthe European home market.


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[edit] Fuel cell applications

Further information:Fuel cell vehicle, Stationaryfuel cell applications, andPortablefuelcell applications

Type 212 submarine with fuel cell propulsion of the German Navy in dry dock

The world's first certified Fuel Cell Boat (HYDRA), in Leipzig/Germany

Fuel cells are very useful as power sources in remote locations, such as spacecraft, remoteweather stations, large parks, rural locations, and in certain military applications. A fuel cellsystem running on hydrogen can be compact and lightweight, and have no major moving

parts. Because fuel cells have no moving parts and do not involve combustion, in idealconditions they can achieve up to 99.9999% reliability.

[22]This equates to around one minute

of down time in a two year period.

Micro combined heat and powersystems such as home fuel cells and cogeneration for officebuildings and factories are in mass production phase. Thestationary fuel cell applicationgenerates constant electric power (selling excess power back to the grid when it is not

consumed), and at the same time produces hot air and water from the waste heat. A lowerfuel-to-electricity conversion efficiency is tolerated (typically 15-20%), because most of theenergy not converted into electricity is utilized as heat. Some heat is lost with the exhaust gas

just as in a normal furnace, so the combined heat and power efficiency is still lower than100%, typically around 80%. In terms ofexergy however, the process is inefficient, and onecould do better by maximizing the electricity generated and then using the electricity to drivea heat pump. Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existingCHP products worldwide and can provide combined efficiencies close to 90%

[23](35-50%

electric + remainder as thermal) Molten-carbonate fuel cells have also been installed in these

applications, and solid-oxide fuel cell prototypes exist.

Since electrolyzer systems do not store fuel in themselves, but rather rely on external storageunits, they can be successfully applied in large-scale energy storage, rural areas being oneexample. In this application, batteries would have to be largely oversized to meet the storagedemand, but fuel cells only need a larger storage unit (typically cheaper than anelectrochemical device).


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One such pilot program is operating on Stuart Island in Washington State. There the StuartIsland Energy Initiative

[24]has built a complete, closed-loop system: Solar panels power an

electrolyzer which makes hydrogen. The hydrogen is stored in a 500 gallon tank at 200 PSI,and runs a ReliOn fuel cell to provide full electric back-up to the off-the-grid residence. The

SIEI website gives extensive technical details.

The world's first Fuel Cell Boat HYDRA used an AFC system with 6.5 kW net output.

In 2003, the world's first propeller driven airplane to be powered entirely by a fuel cell wasflown (the first fuel cell powered aircraft was the Space Shuttle). The fuel cell was a uniqueFlatStack

TMstack design which allowed the fuel cell to be integrated with the aerodynamic

surfaces of the plane.[25]

[edit] Suggested applications

y Backup Powery Base load power plantsy Electric and hybrid vehicles.y Auxiliary powery Off-grid power supplyy Notebook computers for applications where AC charging may not be available for

weeks at a time.y Portable charging docks for small electronics (e.g. a belt clip that charges yourcell

phone orPDA).y Smartphones with high power consumption due to large displays and additional

features like GPS might be equipped with micro fuel cells.

[edit] Hydrogen transportation and refueling

Main articles:Hydrogen vehicle,Hydrogen station, andHydrogen highway

Toyota FCHVPEM FC fuel cell vehicle.


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Mercedes-Benz (Daimler AG) Citaro fuel cell bus on Aldwych, London.

Element One fuel cell vehicle.

Hydrogen fueling station.

Toyota's FCHV-BUS at the Expo 2005.

The GM 1966 Electrovan was the automotive industry's first attempt at an automobilepowered by a hydrogen fuel cell. The Electrovan, which weighed more than twice as much asa normal van, could travel up to 70mph for 30 seconds.[18][26]


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The 2001 Chrysler Natrium used its own on-board hydrogen processor. It produces hydrogenforthe fuel cell by reacting sodium borohydride fuel withBorax, both of whichChrysler

claimed were naturally occurring in great quantity in the United States.[27]

The hydrogenproduces electric powerin the fuel cell for near-silent operation and a range of 300 miles

withoutimpinging on passenger space. Chrysleralso developed vehicles which separatedhydrogen from gasoline in the vehicle, the purpose being to reduce emissions without relying

on a nonexistenthydrogen infrastructure and to avoid large storage tanks.[28

]

The first public hydrogen refueling station was opened in Reykjavk, Icelandin April 2003.This station serves three buses built by DaimlerChryslerthatare in service in thepublictransport net of Reykjavk. The station produces the hydrogen it needs by itself, withanelectrolyzing unit (produced byNorsk Hydro), and does not need refilling:allthat enters iselectricity and water. Royal Dutch Shellis also a partnerin the project. The station has noroof, in orderto allow any leaked hydrogen to escape to the atmosphere.

In 2003 President George Bush proposed the Hydrogen Fuel Initiative (HFI), which was laterimplemented by legislation throughthe 2005 Energy Policy Actand the 2006 AdvancedEnergy Initiative. These aimed at further developing hydrogen fuel cells and its infrastructure

technologies withthe ultimate goalto produce commercial fuel cell vehicles by 2020. By2008, the U.S. had contributed 1 billion dollars to this project.[29]

In May 2009, however, the Obama Administrationannounced thatit will"cut off funds" forthe development of fuel cellhydrogen vehicles, since other vehicle technologies willlead toquicker reduction in emissions in a shortertime. The US Secretary of Energy explained thathydrogen vehicles "willnot

e practicalovert

e next10 to 20years", and also mentioned thechallenges involved in the development ofthe required infrastructure to distribute hydrogenfuel. Nevertheless, the U.S. government will continue to fund research related to stationaryfuel cells.[30] TheNational Hydrogen Associationand the U.S. FuelCellCouncil criticizedthis decision arguing that"...t

e cuts proposedin t

e DOE hydrogen and fuelcellprogram

threaten to disruptcommerciali ation of a family oftechnologies thatare showingexceptionalpromise and beginningto gain markettraction."[31]

In 2005the British firm Intelligent Energy produced the first ever working hydrogen runmotorcycle called the ENV (Emission Neutral Vehicle). The motorcycle holds enough fueltorun for fourhours, and to travel 100 miles in an urban area, atatop speed of50 miles perhour.

[32] In 2004Honda developed afuel-cell motorcycle which utilized the Honda FCStack.[33][34]

Type 212 submarines use fuel cells to remain submerged for weeks withoutthe need tosurface. Boeing researchers and industry partners throughout Europe conducted experimentalflighttests in February 2008 ofa manned airplane powered only by a fuel celland

lightweightbatteries. The FuelCell Demonstrator Airplane, as it was called, used a ProtonExchange Membrane (PEM) fuel cell/lithium-ion batteryhybrid system to poweran electricmotor, which was coupled to a conventional propeller.[35]

In 2007, the Revolve Eco-Rally (launched by HRH Prince of Wales) demonstrated severalfuel cell vehicles on British roads forthe firsttime, driven by celebrities and dignitaries fromBrighton to London's Trafalgar Square.[citation needed] Fuel cell powered race vehicles, designedand built by university students from around the world, competed in the world's firsthydrogen race series called the 2008 Formula Zero Championship, which began on August


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22, 2008in Rotterdam, the Netherlands. More races are planned for 2009and 2010. Afterthisfirst race, Greenchoice Forze from the university of Delft (The Netherlands) became leaderin

the competition. Other competing teams are Element One (Detroit), HerUCLAs (LA),EUPLAtecH2 (Spain), Imperial Racing Green (London) and Zero Emission Racing Team

(Leuven).

The California Hydrogen Highwayis an initiative by the California Governorto implementaseries ofhydrogen refueling stationsalong that state. These stations are used to refuelhydrogen vehicles suchas fuel cell vehicles and hydrogen combustion vehicles. As of July2007Californiahad 179 fuel cell vehicles and twenty five stations were in operation,

[36]and

ten more stations have been planned forassembly in California. However, there have alreadybeen three hydrogen fueling stations decommissioned.

[37]

Japanalso has ahydrogen highway, as part ofthe Japan hydrogen fuel cell project. Twelvehydrogen fueling stationshave been builtin 11 cities in Japan. Canada, SwedenandNorwayalso have hydrogen highwaysimplemented.

There are numerous prototype or production cars and buses based on fuel celltechnology

being researched or manufactured by motor car manufacturers. In 2008, Honda released ahydrogen vehicle, the FCX Clarity. Meanwhile there existalso other examples of bikes

[38]

and bicycles[39] withahydrogen fuel cell engine.

A few companies are conducting hydrogen fuel cell researchand practicalfuel cell bustrials.Daimler AG, withthirty-six experimental units powered by Ballard Power Systems fuel cellscompleting a successfulthree-yeartrial, in eleven cities, in January 2007.

[40][41]There are

also fuel cell powered buses currently active orin production, suchas a fleet of Thor buseswithUTC Powerfuel cells in California, operated by SunLine Transit Agency.

[42]The Fuel

CellBus Clubis a global cooperative effortin trial fuel cell buses.

The firstBrazilanhydrogen fuel cell bus prototype will begin operation in So Paulo duringthe first semester of 2009. The hydrogen bus was manufactured in Caxias do Suland thehydrogen fuel will be produced in So Bernardo do Campo from waterthroughelectrolysis.The program, called "nibus Brasileiro a Hidrognio" (Brazilian Hydrogen Autobus),includes three additional buses.

[43][44]

[edit] Market structure

Notall geographic markets are ready for SOFC powered m-CHP appliances. Currently, the

regions thatlead the race in Distributed Generation and deployment of fuel cell m-CHP unitsare the EU and Japan.[45]

[edit] Hydrogen economy

Main article:Hydrogen economy

Electrochemical extraction of energy from hydrogen via fuel cells is an especially cleanmethod of meeting power requirements, but notan efficient one, due to the necessity ofadding large amounts of energy to either water orhydrocarbon fuels in orderto produce the


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hydrogen. Additionally, during the extraction ofhydrogen from hydrocarbons, carbonmonoxide is released. Althoughthis gas is artificially converted into carbon dioxide, sucha

method of extracting hydrogen remains environmentally injurious.

Also, it must be noted that regarding the concept ofthe hydrogen vehicle,burning/combustion ofhydrogen in an internal combustion engine (IC/ICE) is often confused

withthe electrochemical process of generating electricity via fuel cells (FC) in whichthere isno combustion (thoughthere is a small byproduct ofheatin the reaction). Both processesrequire the establishment ofahydrogen economy before they may be consideredcommercially viable, and even then, the aforementioned energy costs make ahydrogeneconomy of questionable environmental value. Hydrogen combustion is similarto petroleumcombustion, and like petroleum combustion, still results in nitrogen oxides as a by-product ofthe combustion, whichlead to smog. Hydrogen combustion, like that of petroleum, is limited

by the Carnot efficiency, and is completely different from the hydrogen fuel cell's chemicalconversion process ofhydrogen to electricity and water without combustion. Hydrogen fuelcells emit only water during use, while producing carbon dioxide emissions during themajority ofhydrogen production, which comes from natural gas. Directmethane ornaturalgas conversion (whether IC or FC) also generate carbon dioxide emissions, but direct

hydrocarbon conversion in high-temperature fuel cells produces lower carbon dioxideemissions than either combustion ofthe same fuel (due to the higher efficiency ofthe fuelcell process compared to combustion), and also lower carbon dioxide emissions thanhydrogen fuel cells, which use methane less efficiently than high-temperature fuel cells byfirst converting itto high purity hydrogen by steam reforming. Althoughhydrogen can also

be produced by electrolysis of water using renewable energy, at presentless than 3% ofhydrogen is produced in this way.

Hydrogen is an energy carrier, and notan energy source, because it must be produced byadding energy from other energy sources, suchas fossil fuels, wind power, nuclear power, orsolar photovoltaic cells. Hydrogen may be produced from subsurface reservoirs of methaneand natural gas by a combination ofsteam reforming withthe water gas shift reaction, fromcoal by coal gasification, or from oil shale by oil shale gasification.[citation needed]low pressureelectrolysis of waterorhigh pressure electrolysis, which requires electricity, and high-temperature electrolysis/thermochemical production, which requires hightemperatures (idealforthe expected Generation IV reactors), are two primary methods forthe extraction ofhydrogen from water.

As of 2006, 49.0% ofthe electricity produced in the United States comes from coal, 19.4%

comes from nuclear, 20.0% comes from natural gas, 7.0% from hydroelectricity, 1.6% frompetroleumand the remaining 3.1% mostly coming from geothermal, solarandbiomass.

[46]

When hydrogen is produced through electrolysis, the energy comes from these sources.Thoughthe fuel cellitself will only emitheatand wateras waste, pollution is often caused

when generating the electricity required to produce the hydrogen thatthe fuel cell uses as itspower source (for example, when fossil fuel-generated electricity is used). This will be thecase unless the hydrogen is produced using electricity generated by hydroelectric,geothermal, solar, wind or other clean power sources (which may or may notinclude nuclear

power, depending on one's attitude to the nuclear waste byproducts);hydrogen is only asclean as the energy sources used to produce it. A holistic approachhas to take intoconsideration the impacts ofan extended hydrogen scenario, including the production, the useand the disposal ofinfrastructure and energy converters.


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Nowadays low temperature fuel cell stacksproton exchange membrane fuel cell (PEMFC),direct methanol fuel cell (DMFC) andphosphoric acid fuel cell (PAFC) make extensive use

ofplatinumcatalysts. Impurities create catalyst poisoning (reducing activity and efficiency)in these low-temperature fuel cells, thus highhydrogen purity orhigher catalyst densities are

required.[47]

Although platinum is seen by some as one ofthe major"showstoppers"to massmarket fuel cell commercialization companies, most predictions of platinum running out

and/or platinum prices soaring do nottake into account effects ofthrifting (reduction incatalystloading) and recycling. Recent researchatBrookhaven National Laboratory couldlead to the replacement of platinum by agold-palladium coating which may be lesssusceptible to poisoning and thereby improve fuel celllifetime considerably.

[48]Currenttargets foratransport PEM fuel cells are 0.2 g/kW Pt whichis a factor of5 decrease overcurrentloadings and recent comments from majororiginal equipment manufacturers(OEMs) indicate thatthis is possible. Also itis fully anticipated thatrecycling of fuel cellscomponents, including platinum, will kickin. High-temperature fuel cells, including moltencarbonate fuel cells (MCFC's) and solid oxide fuel cells (SOFC's), do not use platinum ascatalysts, butinstead use cheaper materials suchas nickeland nickel oxide, whichare

considerably more abundant (for example, nickelis used in fairly large quantities in commonstainless steel). They also do not experience catalyst poisoning by carbon monoxide, and so

they do not require high-purity hydrogen to operate. They can use fuels withan existing andextensive infrastructure, suchas natural gas, directly, withouthaving to first reform it

externally to hydrogen and CO followed by CO removal. Instead, they can more efficientlyuse the same fuels thatare used to make hydrogen forlow-temperature fuel cells. This fuel

flexibility, combined with new developments to make SOFCs on cheaperand more durablemetal supports, makes SOFCs increasingly importantas candidates fortransportation, as well

as for stationary power. SOFCs have the highest efficiency ofall fuel celltypes, and theirability to use common fuels, including liquid fuels, may make them more suitable forlong-distance vehiculartransportation, as wellas for stationary power.

[edit] Research and development

y August 2005:Georgia Institute of Technology researchers use triazoleto raise theoperating temperature of PEM fuel cells from below 100 Cto over 125C, claimingthis will require less carbon-monoxide purification ofthe hydrogen fuel.

[49]

y 2006:Staxonintroduced an inexpensive OEM fuel cell module for system integration.In 2006Angstrom Power, aBritishColumbia based company, began commercialsales of portable devices using proprietary hydrogen fuel celltechnology,trademarked as "micro hydrogen."

[50][51]

[edit]

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