Fuel Cells Evolution 2009

Fuel Cells

P Kurzweil, University of Applied Sciences, Amberg, Germany

& 2009 Elsevier B.V. All rights reserved.

Early Insights into Energy Conversion

Together with the electric motor, the dynamo, the gasturbine, the internal combustion engine, and the fusedsalt electrolysis of aluminum, the industrial revolution ofthe nineteenth century brought about the fuel cell – thesilent or cold combustion of fossil fuels by the electro-chemical oxidation with atmospheric oxygen to water andcarbon dioxide. Fuel cells convert the chemical energystored in the fuel directly into electricity, without anydetour using heat.

Wilhelm Ostwald, in 1894, emphasized the high effi-ciency and the nonpolluting properties of the directconversion of chemical energy into electricity – in con-trast to the then combination of steam engine and dy-namo, which reached only about 10% efficiency at thattime. Direct coal fuel cells designed for the propulsion ofships, however, have not become a reality so far. Insteadof fuel cells and batteries, internal combustion enginesdetermined the twentieth century. Against the back-ground of the oil crisis and the long-term scarcity ofnatural gas, crude oil, and coal, new hopes have focusedon fuel cell technology, which saw the first splendidapplications during the space programs of the 1960s, insubmarines since the 1980s, and in experimental zero-emission vehicles (ZEVs) since the 1990s.

Schonbein’s Pioneering Work

At the time when there was no general understanding ofelectricity, when the physical meaning of voltage, cur-rent, and power was not yet clear, when electricity’sstrength was measured by the sensation of electric shocks,the length of an arc, or the amount of gas liberated byelectrolysis, in 1839, Christian Friedrich Schonbein (1799–1868), professor at the University of Basel, discovered thefuel cell effect during his studies on the electrolysis ofdiluted sulfuric acid and other matters. Schonbein pre-sented his discovery at the 1839 meeting of the BritishAssociation for the Advancement of Science at Bir-mingham, from which he received a grant of 40 PoundsSterling ‘‘for defraying the expenses of certain Experi-ments on the connexion between Chemical and Elec-trical Phenomena.’’ His article appeared in the January1839 edition of ‘The London, Edinburgh, and DublinPhilosophical Magazine’, in short, ‘PhilosophicalMagazine’.

During his electrochemical studies, Schonbein noticeda strange ‘electric smell’ that followed the passage of the

generated electricity in electric arcs. With the aid of aplatinum zinc battery, which Schonbein had purchasedfrom his friend Grove during his visit to England, he wasable to generate enough substance to announce the dis-covery of ozone in October 1839. Moreover, Schonbeinapplied for an English patent protection of his gun cotton(nitrocellulose); his patent attorney was Sir WilliamGrove. The news of a horrible explosion at the factory ofhis English license holder in 1847 is said to have inspiredAlfred Nobel’s own developments of nitroglycerin and,subsequently, of dynamite. Schonbein was born in theGerman town of Metzingen and spent his youth com-pulsorily under Napoleon’s occupation. He, who was onfriendly terms with Michael Faraday, could not helpnoting in a postscript to Grove on 12 February 1858: ‘‘Iwas rather vexed to see the other day a misprint in myletter to Faraday published in the last number of thePhilosophical Magazine. Instead of Academy of Munichthey put Academy of Paris and you know perhaps that onpurpose I abstain from communicating even the slightestnote to the French Institutions. I won’t have any thing todo with the ‘savants’ there.’’ Schonbein and Grove used tohave a lively correspondence and familial visits for almost30 years.

Grove’s First Practical Fuel Cell

Welsh lawyer and physics professor William R. Grove

(1811–1896), in a one-page postscript to an unrelatedpaper that appeared in February 1839, described that anelectrolytic cell, consisting of two platinum strips sur-rounded by closed tubes containing hydrogen and oxygenin sulfuric acid, provided electricity for a short time afterthe electrolytic current was switched off (Figure 1).Meanwhile, German chemist Robert Wilhelm Bunsen, in1841, created the nonpolarizing carbon–zinc cell, re-placing the expensive platinum used in Grove’s cell bythe cheaper carbon. This battery found large-scale usefor powering arc lights, and in electroplating. Between1842 and 1845, Grove demonstrated his ‘gas battery’, ahydrogen–oxygen secondary battery, which deliveredelectricity during the consumption of gases producedbefore by electrolysis or steam pyrolysis of water. Grovewas ever the practical thinker and built fuel cells workingon hydrogen and chlorine, camphor, vegetable oils, ether,and alcohol.

Grove became a high court judge in 1880. He is alsofamous for his galvanic cell using zinc and sulfuric acidfor the anodic reaction, and platinum in nitric acid for

579

Grove 1839

Figure 1 Grove’s discovery of the hydrogen–oxygen fuel cell

was based on insights into electrolysis. Detail from Philosophical

Magazine (1839). Sources: www.wbzu.de/infopool/images/grove.

jpg; http://www.diebrennstoffzelle.de/zelltypen/geschichte/

grove.gif.

580 History | Fuel Cells

the cathode. The device provided nearly double thevoltage of the first Daniell cell. Early American telegraphoffice systems were reported to be filled with poisonousnitrous fumes from rows of Grove batteries, before ad-vanced Daniell batteries emerged victoriously by thetime of the American Civil War. Grove narrated in aletter to Schonbein dated 20 August 1842: ‘‘A friend ofmine in the neighbourhood has with me been getting upa boat which goes at about 3 miles an hour by ElectroMagnetism with only 8 pairs of 6 inch plates of mybattery & carries several hundred weights.’’ In the 1840s,Prussian engineer Moritz H. von Jacobi, financed by CzarNicholas, powered the first electric boat using 128 Grovecells. Jacobi’s theorem about load matching is known toevery electrochemist.

The Phantom of Direct Conversion of Coal

The direct conversion of coal, the most important primaryresource of the nineteenth century, has not been successfulup to the present. In 1855, A. C. Becquerel and A. E. Becquerel

experimented with a carbon rod in molten sodium nitrate,and a vessel of platinum or iron as the counter electrode.In 1860, M. Vergnes (US 28317) realized a sulfuric acid cellusing platinized coke electrodes. C. Westphal (Germany,1880) explored as well the direct conversion of fossil fuels.

L. Mond and C. Langer (England, 1889) discovered theoverpotential at the oxygen electrode and recognizedcarbon monoxide as an electrode poison during theirexperiments with hydrogen–oxygen fuel cells, havingplatinized platinum electrodes in sulfuric acid and dia-phragms of gypsum, clay, cardboard, or asbestos. TheirSwiss patent of 1889 (CH 492) is entitled ‘gas battery’.

In 1896, American engineer William W. Jacques suc-ceeded in producing electricity directly from coal. Jac-ques’ passion was the propulsion of ships. He placed ahundred cells with carbon electrodes in molten alkalihydroxide on top of a coal-fired furnace and injected airinto the heated electrolyte (400–500 1C). Actually, he wasable to measure an electric current of 16 A at 90 V. Jac-ques initially claimed 82% efficiency for the carbon‘battery’, but he forgot to account for the addition of heatand the energy demand of the air pump. The real effi-ciency was a meager 8%. Further research revealed thatthe current originated partly from thermoelectric action.

In 1897, C. Liebenow and L. Strasser (Accumulator-enfabrik AG, later Varta in Germany) studied the poten-tials at carbon and iron electrodes in molten potassiumhydroxide, but could not realize a practical battery.

In 1904–06, Fritz Haber and coworkers (Germany)investigated in more detail the temperature and pressuredependence of the cell voltage of the direct carbonconversion reaction. They used a glass frit coated withplatinum or gold on both sides. Finally, the direct coalfuel cell turned out to be a hydrogen–oxygen fuel cell,because carbon is not simply oxidized to carbonate infused alkali hydroxide, but hydrogen is generated in apreceding chemical reaction in the molten electrolyte.

Anodic reaction :

Cathodic reaction :

Overall reaction :

Cþ 2OH� þH2O-CO32� þ 2H2

2H2 þ 4OH�-4H2Oþ 4e�

O2 þ 2H2Oþ 4e�-4OH�

Cþ O2 þ 2OH�-CO32� þH2O

A similar so-called CE reaction mechanism explainedthe direct conversion of CO and generator gas. Carbondissolves slowly in molten alkali salts. Carbonate and theash content of the coal form a steadily increasing amountof undesired impurities in the electrolyte.

Between 1918 and 1920, K. A. Hofmann (Germany)investigated the direct conversion of carbon monoxide atcopper plates in molten alkali at platinum–air electrodes.However, the time was ripe for genuine hydrogen–oxy-gen fuel cells (Figure 2).

Since the beginning of the twenty-first century, re-search groups have once again been concentrating ondirect fuel cells. The Lawrence Livermore NationalLaboratory (USA), in 2005, reported 0.8 V cell voltage at1–2 kA m�2 in a self-feeding carbon/air fuel cell, basedon molten alkali carbonate electrolyte and the internalpyrolysis of cleaned coal. Since 2005, further activitieshave been reported by university and industry researchgroups in the USA, Europe, and China.

Sparsely Prosperous Indirect Fuel Cells

In 1912, Walter Nernst (DE 264026) oxidized and reducedmultivalent ions such as iron, titanium, thallium, and

Schönbein1839

Schottky1935

Baur1937

Accumulato-renfabrik

1897

Bacon1937

Justi/Winsel1948/53

Kordesch/Union Carbide

1963−69

Elenco1976

Vergnes1860

Mond/Langer1889

Reid1902

Jacques1896

Becquerel1855

Westphal1880

Japan1981

Sulzer1990

Beutner1911Haber

1904

Baur1910−44

MTU

UTC/IFC1967−86

GeneralElectric

1962−66

Shell,Exxon

1960−70Broers

1958−69 Davtyan1946−71

VARTA1959

Siemens1961/85

Müller1922

Bosch1963

Hitachi1983

Siemens1994Ballard/

DaimlerChrysler1994

Vaillant1998

ONSI/IFC1992

Dornier1987

FCE/ERCSiemens

Westinghouse

Grove1839/42

Westinghouse1967

AFC

Spaceprograms(USA, SU)

Coal conversion

PAFC PEFC DMFC MCFC SOFC

Figure 2 Historical development of fuel cell technology. Reproduced from Kurzweil P (2003) Brennstoffzellentechnik (Fuel Cell

Technology). Wiesbaden: Vieweg. AFC, alkaline fuel cell; PAFC, phosphoric acid fuel cell; PEFC, polymer electrolyte fuel cell; DMFC,

direct methanol fuel cell; MCFC, molten carbonate fuel cell; SOFC, solid oxide fuel cell.

History | Fuel Cells 581

cerium in acid solution with oxygen and hydrogen, re-spectively. His redox fuel cell formed a two-electrodeflow battery, which generated electricity by redox re-actions taking place at ‘unassailable’ electrodes such asgraphite electrodes. Nernst mentioned earlier attempts ofFrench researchers (FR 345118).

In 1955–58, E. K. Rideal and coworkers (Great Britain),despite intensive research, did not find any rapid redoxsystem appropriate for a fuel cell. Owing to the poorpower density, such indirect fuel cells had no market andare currently not under investigation.

Historical Roots of Alkaline Fuel Cells

The Discovery of Gas Diffusion Electrodes

J. H. Reid (US 736016), in 1902, and P. G. L. Noel (FR350111), in 1904, experimented with alkaline fuel cells(AFCs) in KOH solution. The three-phase boundarybetween electrodes, electrolyte, and gas space was al-ready mentioned by Grove at platinum electrodes, theperformance of which declined considerably when wet. Itwas found later that porous electrode structures could beprevented from flooding by applying hydrophobic coat-ings such as polytetrafluoroethylene (PTFE).

In 1919, E. W. Jungner (Sweden, e.g., GB 145018) de-veloped electrodes that were rendered hydrophobic by a

treatment with paraffin. His recipe for preparing graphiteelectrodes sounds quite modern: ‘‘A meal-fine amorphouscarbon powder is kneaded together with a liquid bindingagent, as for instance tar or molasses for obtaining a greatporosity, suitably mixed with a volatile liquid as for in-stance water, to a plastic paste, which firstly is burned inusual manner and then is heated in an electric furnace tosuch a temperature (3000 1C or more) that the carbon isgraphitized.’’

A. Schmid (Germany), in 1923, described the funda-mentals of the gas diffusion electrode (Figure 3). At thattime, M. Raney (US 1563587 of 1925) developed highlydispersed nickel for chemical hydrogenations – later usedas electrode material. Heise and Schumacher (Germany1932) were the first among those who used hydrophobicdiffusion electrodes for high-pressure cells.

In the late 1930s, first practical AFCs with porousnickel electrodes were demonstrated by English mechan-ical engineer Francis Thomas Bacon – a direct descendantof philosopher Sir Francis Bacon. In 1937, Bacon andE. K. Rideal designed a system of electrolyzer, hydrogentank, and fuel cell. In 1939, an AFC delivered 0.89 V at13 mA cm�2 in 27% potassium hydroxide at 100 1C and apressure of 220 bar. Cylindrical sintered nickel electrodesand oxygen electrodes of lithiated nickel oxide followedin 1946. In 1952, a 5 kW system provided 0.78 V at 0.8 Acm�2 in 30% potassium hydroxide (200 1C, 45 bar).

Large pores Fine pores

Gas Electrode Electrolyte

Figure 3 Principle of the gas diffusion electrode as described by

Schmid (1923). Reproduced from Kurzweil P (2003)

Brennstoffzellentechnik (Fuel Cell Technology). Wiesbaden: Vieweg.


A 150 W stack of six cells in ‘filter press design’ workingat 200 1C and 41 bar reached a power density of 355W L�1 in 1954. Between 1956 and 1959, Bacon con-structed 6 kW stacks of 40 cells for forklifts and weldingequipment.

With the manned missions to the moon, AFCs foundtheir first specific application in space. Conventionalbatteries would have been too heavy; cost and life pro-jections were not imperative at that time. In the Baconcells, sintered nickel electrodes operated in 30% potas-sium hydroxide at 200 1C and pressures up to 50 bar. Thepores at the gas side were 10–30 mm in diameter and were1.5–16 mm at the electrolyte side. The pores at the gasside were rendered hydrophobic with paraffin or poly-siloxanes. The electrolyte was fixed by capillary forces inthe small pores, whereas the wider pores were blown freeby the operating pressure. A thin electrolyte filmcreeping on the walls of the wider pores at the gas sideallowed high current densities at the three-phaseboundary between electrode, alkaline electrolyte, and gasspace. The oxygen electrode was coated with lithiumnickel oxide; intercalated lithium improved the con-ductivity of the p-type semiconducting nickel oxide.Reaction water was condensed at cooling fins outside thecell. Since the end of the Apollo flights, high-pressurecells have no longer been used. Gas diffusion electrodesbased on active platinum on porous carbon materialsallowed henceforth the operation of low-pressure AFCsat 50–80 1C.

Low-Pressure AFCs Conquer Spacecrafts andSubmarines

The 1960s

In 1959, Allis Chalmers in Milwaukee, Wisconsin, powereda tractor with the help of a 750 V/15 kW hydrogen–oxygen fuel cell based on bipolar porous metal electrodescoated with platinum, and potassium hydroxide soaked inan asbestos separator. Between 1962 and 1967, in co-operation with NASA, a bipolar fuel cell with nickelelectrodes and platinum–palladium catalysts was de-veloped. The bipolar plates were of nickel-plated mag-nesium. Product water was removed from the hydrogengas stream by static water-vapor control, that is, throughthe diffusion of water through a supported membrane.The ‘immobile’ electrolyte solution, fixed by capillaryforces in a microporous medium, quickened later de-velopments of fixed AFCs and electrolyzers.

The manned ‘Apollo’ missions to the moon between1961 and 1970 were equipped with Pratt & Whitney

hydrogen–oxygen fuel cells (Figure 4). Platinum-activateddouble-layer electrodes of sintered nickel, 20 cm indiameter and about 2 mm in thickness, were integrated ina nickel housing, together with sealing and insulating rigsof fluoropolymers, at a system pressure of 3.3 bar. Theoperating temperature of 200–230 1C was maintained byJoule heat in the molten electrolyte of 85% potassiumhydroxide. Hydrogen and oxygen were supplied by cryostores; water was separated from the residual hydrogenstream by condensation. The temperature of the cell stackwas controlled by electric heating in a jacket of nitrogen,and a radiator outside the spacecraft. A module of 31single cells weighing 109 kg delivered a rated power of1120 W at 28 V. The total 810 kg system consisting of threecell stacks and a tank generated 500 kWh during the 10-day mission, corresponding to an energy density of 620Wh kg�1. Conventional lead–acid batteries would haverequired a mass of 10–12 tonnes, and silver–zinc accu-mulators of 4 tonnes. A total of 54 such stacks accom-panied nine flights to the moon, three Skylabs, and theApollo-Sojus mission, and operated altogether for 10 750 h.The life of the stack, about 400 h, was determined bycorrosion of the nickel oxide electrode, impurities in thefuel gases, and drying up at the hydrogen side.

Around 1965: AFCs were developed among others bySiemens (since 1961), who powered its electric boat‘Eta’ with AFCs in 1965. E. W. Justi, between 1948 and1965, and A. Winsel (since 1961 by Varta) developed thedouble-skeleton electrode using Raney nickel. K. Kordesch

(Union Carbide, 1963–69) favored activated carbon onsintered nickel supports, and powered his ‘Austin A40’ bya 90 V/6 kW fuel cell between 1970 and 1973. Union

Carbide’s thin carbon/fixed zone electrode (1965) con-sisted of a wettable carbon layer at the electrolyte sidethat was impregnated with the electrocatalyst; thereupon

Figure 4 Alkaline fuel cell system for the Apollo space program

(Pratt & Whitney, 1.12 kW module of 31 single cells). Reproduced

from Sandstede G, Cairns EJ, Bagotzky VS, and Wiesener K

(2003) History of low temperature fuel cells. In: Vielstich W,

Lamm A, and Gasteiger HA (eds.) Handbook of Fuel Cells –

Fundamentals, Technology, and Applications, vol. 1, ch. 12,

p. 145. Chichester: John Wiley & Sons Ltd.


followed several hydrophobic layers and finally a sinterednickel layer. General Motors’ ‘Electrovan’ (1967) waspowered by a Union Carbide 400 V/160 kW AFC withmobile electrolyte and fueled by liquid hydrogen (LH2);the early lifetime was a meager 1000 h (Figure 5).

The 1970s

In Japan, Fuji Electric demonstrated a 10 kW AFC (1972).Around 1976, Elenco, a Belgian–Dutch consortium, builtfuel cell stacks of 24 monopolar alkaline cells (for cellcharacteristics, see Figure 6). The hydrogen and oxygenelectrodes were based on nickel mesh. At the electrolyteside, a layer of activated carbon–PTFE–platinum wasrolled on, and at the gas side, a layer of porous PTFE.Heat treatment or sinter processes were not required.

The electrodes were mounted in injection-moldedacrylonitrile butadiene styrene plastic (ABS) frames. Theelectrolyte of potassium hydroxide was ‘mobile’, that is, itwas circulated in the gaps between the electrodes. In thelater EUREKA project (1989–94), together with AirProducts, Ansaldo, and Saft, an 80 kW fuel cell systemfueled by LH2 was combined with a nickel–cadmiumbattery in a 180 kW/800 V propulsion system for citybuses.

The 1980s

Varta in Germany developed the EloFlux cell based onPTFE-bonded gas diffusion electrodes (DE 2941774). By‘reactive mixing’ in a mill, the catalyst powder was sur-rounded by PTFE fibers and then the mass was rolled ina calender onto a wire gauze to yield a continuous bandelectrode. The hydrogen electrode was made of PTFE-bonded Raney nickel on a nickel-plated copper supportas the current collector. The oxygen electrode used aPTFE-bonded silver catalyst on a silver-plated coppermesh. The EloFlux stack consisted of alternatinghydrogen electrodes and oxygen electrodes that wereseparated by a sheet of asbestos or polyolefin. Mobile andimmobile cells were developed. Water and heat wereremoved at the electrode rear side.

United Technologies Corporation (UTC), in cooperationwith NASA, further developed the Apollo fuel cell in1974. In April 1982, the space shuttle was launched withthree 12 kW stacks (32 bipolar cells, 465 cm2, 91 kg,27.5 V at 436 A). In 7 days, electricity and water for theastronauts were produced from 750 kg hydrogen andoxygen. The advanced fuel cell technology comprised thefollowing: oxygen flow plates of nickel-plated plastic; anoxygen electrode of 90% gold (as catalyst) and 10%platinum (as a sintering inhibitor) on a gilt nickel mesh;the electrolyte of 25–45% potassium hydroxide in amatrix of butyl-bonded potassium titanate; a hydrogenelectrode of PTFE-bonded carbon, pressed into a silver-plated nickel mesh, and activated by 10 mg cm�2 plat-inum–palladium (80:20); a hydrogen flow field plate ofmetallized plastic; and cell frames of polyphenylenesulfide.

The 1990s

The fuel cell system ‘Foton’, produced by Ural Electro-

chemical Integrated Plant (also KVANT) after the collapseof the former Soviet Union, has been used in the Ener-gia-Buran space programs since 1960. The 40 kW AFCsystem consisted of four modules.

Between 1984 and 1993, the European Space Agency

projected a regenerative fuel cell system (RFCS) for thespace glider ‘Hermes’, which was not realized, however.One and the same aggregate should alternately work bothas an electrolyzer driven by solar energy and as a fuel cellin the dark phase of the orbit. The fixed alkaline water

0 25 50 75 100 125 150

0.2

0.4

0.6

0.8

1.0

1.2

C

B

A 1

2

3

Current density (mA cm−2)

Cel

l vol

tage

(V

)

Figure 6 Current–voltage characteristics after the data of

Elenco alkaline fuel cells (6.6 mol L�1 KOH, 70 1C): 1 ¼ H2/O2

(platinum), 2 ¼ H2/air (platinum), 3 ¼ H2/air (without catalyst).

A ¼ activation polarization, B ¼ ohmic drop in the electrolyte,

C ¼ mass transport controlled region at high current densities.

Reproduced from Kurzweil P (2003) Brennstoffzellentechnik

(Fuel Cell Technology). Wiesbaden: Vieweg.

Liquid hydrogen tank

Liquid oxygen tankMotorcontrols

Watercondenser

Electrolyteradiator

AC induction motor

Gearbox

Electrolyte reservoir

32 Fuel cell modules

Figure 5 General Motors Electrovan powered by a 150 kW alkaline fuel cell (AFC) (Union Carbide, 1967). Source: Kordesch K (2006)

Fuel Cells and Their Applications. Weinheim, Germany: VCH Publishers.


electrolysis at nickel/IrO2 electrodes was further de-veloped for the oxygen production in space by EuropeanAeronautic Defence and Space Company (EADS) inGermany.

Alkaline fuel cells for submarines have been de-veloped by Siemens since the 1970s. The advanced 6 kWstacks of 1990 combined 60 monopolar cells (340 cm2)electrically connected in series. With the ‘mobile’ tech-nology, potassium hydroxide solution was circulatedthrough the electrolyte gaps filled with asbestos andconnected in parallel. Reaction water was evaporatedfrom the electrolyte by heating. The hydrogen electrodeconsisted of Raney nickel including a certain amount of

titanium. The oxygen electrode contained silver withadditions of nickel, titanium, and bismuth. Eight modules,a heat exchanger, and a gas supply unit formed a 48 kWfuel cell system (192 V, 250 A).

By mid-1990s, the AFC was silently replaced by asystem that promised better power densities and the useof ambient air instead of pure oxygen. Traces of carbondioxide in the oxidants have always been a major problemof the AFC, leading to the formation of potassium car-bonate (K2CO3) in the electrolyte.

The twenty-first century

In Germany, GASKATEL, since 1998, has been furtherdeveloping the ‘Eloflux’ AFC based on carbon and nickel.

Until 2002, ZEVCO Ltd. and ZETEC continued theELENCO Electronics Inc. technology in boats, in apickup truck (63 kW AFC), and in a ‘Millennium Taxi’(5 kW AFC plus battery).

Independent Power Technology (IPT), a Russiancompany established in 2002, is further developing the6 kW ‘KVANT’ AFC system used in the Soviet spaceprograms for auxiliary power units (APUs) in buildingsand ships. ‘Cascade-6’ employs a regenerative carbondioxide purification system.

ASTRIS, a young Canadian company, which un-fortunately had to close for financial reasons in 2007,demonstrated in 2004 its portable 2.5 kW AFC generator‘E8’ having a system efficiency of about 55% at a cellvoltage of 0.7 V.

The US company Apollo Energy Systems in Floridawith pioneer K. Kordesch is developing advanced ‘mo-bile’ AFC systems (2004). Hydrogen is generated by thecracking of ammonia, NH3-3H2þN2.

H2

SPE

Grubb 1955(a) (b) Niedrach 1959

Cat

hode

OxygenFuel gas

Valveoutlet

V V

Ano

de

O2

5

2 3

Figure 7 Historical embodiments of solid polymer fuel cells as disclosed in patents (US 2913511, US 3134697). SPE, solid polymer

electrolyte.

CM SCALE1 2 3 4 5 6 7 8 9

Figure 8 The Grubb cell. Source: Smithsonian Institution,

http://scienceservice.si.edu/pages/copyright.htm


Polymer Electrolyte Fuel Cells

Revolutionary Polymer Technology

Recent developments favor the proton-exchange mem-brane fuel cell (PEMFC) system, which exhibits a com-pact cell design and a high power density, although thetechnology faces strict cost requirements. Environmentalconcerns and forced legislation in California in the 1990sinitiated a unique wave of worldwide research on fuelcells and ZEVs.

The first solid polymer fuel cells were developed byGeneral Electric (USA). Willard Thomas Grubb, a chemistworking for General Electric, explained in US patent2913511 filed in 1955: ‘‘A cell employing a gaseous fuel hastwo electrodes separated by and in contact with a hydratedion exchange synthetic resin membrane which constitutesthe electrolyte. [y] The electrodes may consist of plat-inum, palladium, platinum or palladium black deposited ona base metal such as steel or nickel, or of iridium, rhodium,copper, nickel, metal oxides, or activated carbon, and maybe in the form of sheets, screens or porous bodies.’’

In 1958, Leonard Niedrach (US 3134697) devised a wayof depositing platinum onto ion-exchange membranes.The ‘Grubb–Niedrach fuel cell’, between 1962 and 1966,equipped the Gemini space project – NASA’s first mannedspace vehicles (Figures 7–9). The early membranes wereof sulfonated polystyrene, which, however, dried outquickly. Product water at the cathode was removed withthe help of a wick in every cell. Three stacks of 32 cellsdelivered a power of 1 kW (0.038 W cm�2 at 0.83 V percell). The total system, including pressure reservoirs fordeep-cold hydrogen and oxygen sufficient for 160 kWhelectrical energy, weighed about 250 kg – not more thanone-sixth the mass of a then commercial battery. Fuel andoxygen were preheated in a heat exchanger by use of thecooling water of the fuel cell and an additional electricheater. Critical points were the low power density, and thedesiccation and stability of the polystyrene membrane, sothat AFCs instead of PEFCs were launched in the laterApollo program and the Space Shuttle.

Nafion, a trademark of Du Pont, was introduced in1968 and promptly employed in the 350 W proton ex-change membrane (PEM) fuel cell in the ‘Biosatellite’.

In the early 1980s, UTC, Hamilton Standard Division,and UTC’s subsidiary International Fuel Cells Corp. (IFC)continued the General Electric technology. A number oftechnical improvements – carbon-supported platinumcatalysts, humidification of the gases, elevated differentialpressure at the oxygen side, and higher operating tem-perature – quickened the PEMFC technology. Finally,cell voltages of 0.825 V at 300 mA cm�2 and 0.5 V at 1 Acm�2 were reached (at 105 1C, 10 bar O2, 2 bar H2). Theoperation with air, despite high pressures, however,allowed not more than 300 mA cm�2. The US Navy andSiemens in Germany, based on a UTC license of 1983,developed fuel cells for submarines.

Between 1985 and 1988, Energetic Power Systems (EPSI),a subsidiary of Ergenics, presented 2 kW proton-ex-change membrane (PEM) fuel cells for space applications(Engelhard technology). Water was removed by wicks,and a current density of 1.5 A cm�2 was obtained at a cellvoltage of 0.6 V.

17 bar 58 bar

Cooling waterO2H2

Heat exchanger

3 Stacks (each 32 cells)

WatertankWaste heat

Radiator

Coolingwater

Absorbent

Water

Separator

H2 H2 O2O2O2

H2O

H2O

Ele

ctro

lyte

+ − + +−

Figure 9 Solid polymer fuel cell system in the Gemini spacecraft (1965). Reproduced from Kurzweil P (2003) Brennstoffzellentechnik

(Fuel Cell Technology). Wiesbaden: Vieweg.


Fuel Cells Power Electric Vehicles andSubmarines

Since 1983, Ballard in Canada has been developing fuelcells operated by ambient air. The heavy niobium platesused earlier by NASA were replaced by graphite. Proton-exchange membrane fuel cell systems in combination withgas generators based on steam reforming and CO oxidationwere demonstrated in 1985. In 1987, ‘Mark IV’ delivered4.3 A cm�2 at 0.53 V using a Dow membrane and H2/O2 ata pressure of 7 bar. A submarine was equipped in 1989(Perry Energy). Between 1990 and 1994, city buses werepowered by 24 water-cooled 5 kW stacks fueled by a 210bar Hydrogen tank. A stationary 250 kW power systemfollowed in 1999. ‘Mk500’ stacks (5 kW, 150 W L�1) pow-ered DaimlerBenz’ experimental vehicle ‘Necar 1’ in 1994.

Around 1988, researchers with Los Alamos NationalLaboratory (LANL) succeeded in reducing the platinumload on the electrodes below 1 mg cm�2. Wilson andGottesfeld (1992) pressed films of 20% platinum/carbonpowders bonded by 5% Nafion suspension at elevatedtemperatures on PEM.

In 1987–90, the US Department of Energy (DOE)promoted projects on fuel cell vehicles. Early develop-ments took place at General Motors, Giner, AnalyticPower, and DeNora (Italy). Energy Partners Inc. pre-sented its ‘Green Car’ powered by a 15 kW/125 V PEMfuel cell in 1993 (Figure 10).

In 1994, supported by public funding in Germany, anumber of companies (BASF, Heraeus, Axiva, Hoechst,

Bosch, SGL, Sachsenring, and Siemens) and researchinstitutes (DLR, FhG, FZ Julich, and MPI) turned theirattention to PEM fuel cells. Advanced ion exchangemembranes and solid polymer electrolytes (SPEs) weredeveloped at that time by DuPont, Ballard, Gore,Hoechst, Dow, and Asahi. Dow’s PEM (1988) was a co-polymer of tetrafluoroethene and a vinylether monomer,but with a shorter side chain than that in Nafion.

DaimlerBenz (Germany) started its fuel cell vehicleprogram in 1994. ‘Necar 4’ of 1999 was powered by twoBallard stacks (together 70 kW, 330 V, 200 W kg�1). TheCalifornia Fuel Cell Partnership – a consortium ofDaimlerChrysler (since 1998), Ford, Shell, Texaco,ARCO, Honda, Volkswagen (1999), Nissan, US Depart-ment of Energy (2000), General Motors, Hyundai,Toyota, BP, Exxon, IFC, and others – has been testing afleet of fuel cell vehicles in daily practice and publictransit since. Table 1 gives an overview of early R&Dactivities on fuel cell vehicles.

In 2000, MAN, Siemens, and Linde (Germany) op-erated a public transit bus for nearly 1 year in the city ofNurnberg. The 120 kW PEM fuel cell consisted of 640single cells. A total of 1548 l of hydrogen was stored at250 bar in nine compressed gas cylinders made of alu-minum and a carbon fiber jacket.

In 2002, Howaldswerke Deutsche Werft (Germany)launched its submarine ‘U212’, which was equipped witha Siemens PEM fuel cell system (50 kW). Hydrogen wassupplied by metal hydride stores that were loaded with

Figure 10 Proton-exchange membrane fuel cell (PEMFC) systems in electric vehicles and submarines. Source: Daimler AG,

Howaldtswerke Deutsche Werft GmbH, Toyota, TUV Sud Industrie Service GmbH. Reproduced from Kurzweil P (2003)



low-temperature, high-pressure hydrogen. Later, ‘U214’had 120 kW stacks.

Around 2007, fleets of up to a hundred electric vehicleswere tested all over the world. Fuel cells are employed byDaimler, Audi, Ford, Daihatsu, GM, General Motors,Honda, Mazda, Lada, Nissan, PSA, Suzuki, Toyota, VW,Volkswagen, and other companies. The European projectsCUTE (Clean Urban Transport for Europe, 2001–06) andHyFleet:CUTE supported field tests of fuel cell buses inAmsterdam, Barcelona, Hamburg, Stockholm, Reykjavik,Madrid, Stuttgart, Luxemburg, Porto, and London. By July2005, 30 CITARO buses of DaimlerChrysler, powered byBallard 250 kW PEM fuel cells, covered a total distance of850 000 km within 62 000 h. Hydrogen has been generatedfrom various natural and regenerative sources.

Table 1 compiles historical highlights of PEMFCsystems in electric vehicles.

Direct Methanol Fuel Cell

For nearly six decades, researchers have been trying toimprove the direct conversion of methanol into elec-tricity – a fascinating idea, which, however, has to meetthe high activation overpotential of the oxidation step tocarbon dioxide in which six electrons are involved.

Similar direct fuel cells were proposed based on glucoseto supply electrical power for artificial hearts and vitalparts in the human body.

In 1910, Taitelbaum (Germany) investigated the anodicoxidation of solved fuels. R. Muller, in 1922, reported onthe electrochemical oxidation of methanol. K. Kordesch

and A. Marko, in 1951, proposed the direct methanol fuelcell (DMFC) in alkaline electrolyte, although seriousinvestigations did not commence immediately.

In the 1960s, Esso Research and Engineering developed a100 W system for use in communication systems of the USArmy. The initial unit gave 55 mA cm�2 at 0.4 V, usingnoble metal electrocatalysts, but durability was limited. K.

R. Williams and D. P. Gregory, working with Shell, obtained apower of 300 W from a series connection of 40 DMFCs in1963. In the same year, engineers at Bosch (Germany) in-vestigated ‘methanol–oxygen batteries’, especially asmethanol has attracted most interest as an inexpensive,and widely available fuel. Both Shell and Esso terminatedtheir research on DMFC catalysts in the late 1970s. Theplatinum/ruthenium system was among the most active ofthe ones tested, but it did not meet the activity targets forautomotive applications.

Around 1972, ruthenium was discovered as the elec-trocatalyst for the oxidation of methanol. Other DMFC

Table 1 Early milestones of fuel cell vehicles

1990 Energy Partners (USA): ‘Green Car’

1993 Ballard (Canada): PEM fuel cell bus ‘P1’ (120 kW)

1995 Ballard (Canada): ‘Mark 900’ delivers 250 V/75 kW from 440 single cells

1997–2000 Ballard: Six fuel cell buses in Chicago and Vancouver carry 200 000 passengers along 118 000 km

1997 dbb Fuel Cell Engines (later Xcellsis), a consortium of DaimlerBenz, Ford, and Ballard (Germany): methanol fuel cell

car ‘NECAR 3’. Ansaldo: bus (45 kW PEMFC and lead–acid battery). Daimler-Benz: ‘Nebus’ (250 kW PEMFC)

1998 Toyota ‘RAV4’ with methanol reformer

1999 Ford ‘P2000’ with CGH2. First hydrogen gas station in the USA; DaimlerChrysler: NECAR 4; Xcellsis: 200 kW fuel cell

engine ‘P4’ for buses

2000 DaimlerChrysler: NECAR 5 and hybrid vehicle ‘Jeep Commander 2’; Ford ‘Focus FCV’ (355 bar CGH2); General

Motors’ ‘Opel Zafira HydroGen1’ with LH2 PEMFC establishes a record in speed and range; Munich airport

(Germany) opens a hydrogen gas station. MAN: fuel cell bus (120 kW PEMFC)

2001 Mercedes ‘Sprinter’ vans (75 kW H2 PEMFC) for Hermes-Versand; first zero-emission bus of SunLine Transit

Agency, Palm Springs, achieves 24 000 km; Chrysler ‘Natrium’ van with NaBH4 store; Fiat ‘Seicento Elettra H2 fuel

cell’; Honda ‘FCX V3’ and ‘FCX V4’ including Ballard fuel cell, hydrogen store, double-layer capacitor; Mazda

‘Premacy’ with methanol reformer; Toyota ‘FCHV-3’ with titanium hydride store, ‘FCH-4’ with 350 bar CGH2,

‘FCH-5’ with methanol reforming

2002 DaimlerChrysler ‘Mercedes F-Cell’ and Ford ‘Focus FCV Hybrid’ (65 kW, NiMH battery, Ballard ‘Mark 902’ fuel cell,

350 bar CGH2). ‘Necar 5’ runs 5250 km from San Francisco to Washington; Evobus ‘CITARO’ fuel cell bus; General

Motors’ Chevrolet-Pickup ‘S10’ with gasoline reformer; Volkswagen and Volvo: ‘Golf Variant’ with methanol

reformer, ‘Bora Hy.Motion’ with LH2. A ‘Bora Hy.Power’ with 320 bar CGH2 and 350 V/60 kW double-layer capacitor

crosses the Swiss-Italian Simplon pass; Audi ‘A2’ with 58 kW PEMFC and 6.5 Ah NiMH battery

2003 US Government: 1.2 billion US$ for hydrogen technology; Nissan: ‘X-Trail FCV’; Clean Energy Partnership; General

Motors: Opel ‘Zafira’ with PEMFC and 4.6 kg LH2; Reykjavik (Iceland): public hydrogen gas station

2005 DaimlerChrysler: ‘F600 Hygenius’ (85 kW) powered by a 60 kW PEMFC and a Li-ion battery; 4 kg hydrogen (700 bar);

Toyota: ‘Fine-X’, 80 kW PEMFC plus battery, CGH2 (700 bar)

CGH2, compressed gaseous hydrogen. PEM, proton-exchange membrane; PEMFC, proton-exchange membrane fuel cell.


systems have been investigated by Brown Boveri (around1964), Cathro and Weeks (1971), the US Army formilitary communication systems, and the Royal Instituteof Technology, Stockholm, for electric wheelchairs(1977–80).

Hitachi (Japan, 1983) applied acid electrolytes inDMFCs. Applications were foreseen in the leisure anddomestic markets. A hybrid system with lead–acid bat-teries was demonstrated in a golf cart. Platinum was usedas the cathode catalyst and a combination of platinumand ruthenium in the anode.

In 1993, Siemens reported cell voltages of 0.5 V at400 mA cm�2 (O2, 4 bar, 130 1C). UTC’s membrane cellsof 1994 delivered 0.7 V. The Jet Propulsion Laboratory re-duced the platinum load to 0.5 mg cm�2 and achieved acell voltage of 0.4 V at 0.1 A cm�2 and 60 1C. In the sameyear, Ballard (Canada) started R&D on DMFC systems.Johnson-Matthey (Great Britain, 1995) developed carbon-supported PtRu electrodes bonded with a Nafion film.

In 2001, DaimlerChrysler (Germany) powered a go-cart by a 3 kW pure oxygen DMFC (Figure 11). Ballard

demonstrated portable DMFC having a power density of500 W L�1. In 2002, Smart Fuel Cell (Germany) presentedthe ‘Remote Power System SFC 25’ for outdoor powersupply and camping.

Toshiba’s 100 mW DMFC of 2004, weighing 8.5 g, wassmall enough to power mobile phones and MP3 playersfor about 20 h by 2 cm3 of methanol (0.1 W from22� 56� 4.5 mm).

Small companies such as Smart Fuel Cell (SFC),PlugPower, Hydrogenics, FC Energy, Voller, MIT Micro,and Medis have been improving DMFC technology forportable applications, for example, in mobile telephones,PDAs, and MP3 players. SFC’s ‘EFOY’ generators of2006–07 delivered 25, 50, and 65 W of power, and ca-pacities in the range of kilowatt hours.

Mobile applications suffer from the low power densityof the DMFC. However, Veloform commercialized thebicycle-like ‘CityCruiser’ and ‘DeliveryCruiser’ poweredby a DMFC (SFC).

Stationary Power Systems

In the 1990s, stationary PEM fuel cells were investigatedwith respect to supply of electric power and heat forprivate households. Hydrogen is generated by steam re-forming of natural gas, followed by partial oxidation ofresidual CO to CO2 – or the combination of both pro-cesses, the so-called autothermal reforming.

Fraunhofer Institute (ISE, Germany) and Energy Partners

(USA) built a 7.5 kW system in 1996. Vaillant and Plug

Power, since 1998, have equipped heating systems in theUSA and Germany. In 2002, a combined heat and powerunit based on natural gas and a PEM fuel cell was dem-onstrated. European Fuel Cell (EFC) and Dais Analytic Power

(USA), since 2000, furthermore Viessmann, and sincearound 2003, RWE Plus (Germany) and Nuvera Fuel Cells

(USA), as well as Buderus and UTC (USA) have established

Figure 11 Go-cart, ‘CityCruiser’ and ‘DeliveryCruiser’ powered by direct methanol fuel cells (DMFCs). Source: Daimler AG, kfpn

GmbH (Germany). Reproduced from Kurzweil P (2003) Brennstoffzellentechnik (Fuel Cell Technology). Wiesbaden: Vieweg.


PEMFC systems in the range of 1.5–5 kW in houses. In theUSA, Plug Power/GE, UTC, and Ida Tech have beenactive in the field of 10 kW electric power generation. In2005, Ballard in Canada sold 315 ‘Mark 1030’ stacks(1.3 kW) for different clients, among others, in Japan.

In Japan, since 2005, a large field test program of severalhundred 1 kW PEM fuel cell systems for household energyand heat supply is under way, borne by Ebara-Ballard,Sanyo, Panasonic, Toshiba, and Toyota. Town gas, kerosene,and liquefied petroleum gas (LPG) have been used as pri-mary fuels.

Fuel cells in uninterruptible power supply (UPS)systems have been employed by P21, a company estab-lished in Brunnthal in 2001, in its ‘Premion T’ (3 kW,48 V, including a supercapacitor) and by PlugPower in its‘GenCore’ (5 kW, 48/230 V, including a battery).

Portable Proton-Exchange Membrane Fuel CellSystems

Portable fuel cells as nearly unlimited power sources forhandheld devices have been developed since the 1990s.Portable ‘power packs’ attracted attention for military usebefore.

Mini fuel cells (500 W–2 kW) for portable powergenerators have been presented by Ballard for use in UPSemergency generators, forklifts, baggage tractors, floorscrubbers, and small electric vehicles. Ballard’s ‘Nexa’1.2 kW PEMFC module of 2001 and the ‘AirGen FuelCell Generator’ of Coleman Powermate were designed foremergency power supply. In 2002, Smart Fuel Cell (Ger-many) presented its portable DMFC.

Midi fuel cells (50–500 W) have been investigated fornovel applications in communication systems andphotovoltaic plants. Masterflex supplied its light tractionapplications, ‘Veloform’ and ‘Cargo-Bike’, with 250 W

PEM fuel cells, which were tested in the EuropeanHychain Minitrans project (2006–07).

Micro fuel cells (o50 W) have been integrated incamcorders, notebooks, and torches, for example, byNEC, ISE Freiburg, and ZSW in Ulm. The Fraunhofer

Institute, in 2003, presented hydrogen PEMFCs forpowering mobile computers and cameras, which werefueled from metal hydride stores.

Phosphoric Acid Fuel Cell

Acid Fuel Cells – Forerunner of the PEMFCSystem

Grove’s sulfuric acid fuel cell of 1839 was the basis for theexperiments of Mond and Langer in 1889, which, however,did not result in a commercial gas battery. In 1983, Exxonand Occidental Chemical completed the rediscoveredsulfuric acid fuel cell with bipolar plates of soot-filledpolypropylene.

Fruitless attempts to convert gasoline in a sulfuric acidfuel cell into electricity ultimately led to the invention ofphosphoric acid fuel cell (PAFC). Hydrocarbons reactwith sulfuric acid at 80–100 1C, whereas there is no re-action with phosphoric acid up to 200 1C. Moreover, thehigher temperature simplifies the removal of productwater, and the PAFC tolerates 1–3% carbon monoxideand hydrogen sulfide (H2 S), so that hydrogen-rich gasesfrom fossil fuels can be used without elaboratepurification.

In 1967, UTC in the USA built the first water-cooledPAFC, based on a PTFE-bonded platinum black catalystin a tantalum mesh, and 85% phospheric acid (H3PO4)absorbed in a glass fiber separator. The ‘fuel cell gener-ator’ of 1971 comprised PTFE-bonded platinum–carbonelectrodes on carbon paper, and 95% phospheric acid

Figure 12 Impression of the 12 MW phosphoric acid fuel cell

(PAFC) of Tokyo Electric Power Station Company (TEPCO), based

on 18 IFC 670kW stacks and a Toshiba infrastructure, generated

77.8 GWh of electric energy in 23140 operating hours between 1991

and 1997.


(H3PO4) absorbed in a silicon carbide (SiC) separator.The first 1 MW plant was demonstrated in SouthWindsor, Connecticut (1977); 4.5 MW plants followed inManhattan (1978–83) and Tokyo (1980–85). A currentdensity of 270 mA cm�2 was achieved at a cell voltage of0.65 V (pressure 3.4 bar) and a system efficiency of40–45%. In 1979–80, a ribbed cell design was introduced.In 1985, IFC was established as a consortium of UTC andToshiba, and renamed as ONSI in 1990. A field test of 42‘PC18’ systems between 1982 and 1986 proved a useablelifetime of 9–15 months. An 11 MW PAFC plant wasestablished in Tokyo thereafter (1989–94).

Westinghouse (USA) has been developing air-cooledPAFCs since 1967, based on the technology of EnergyResearch Corporation (ERC). The design of 1987–90comprised four cell stacks arranged crosswise verticallyaround the integrated feed of fuel, air, and cooling air.

Between 1971 and 1973, Pratt & Witney Aircraft Co.(USA) built 65 experimental 12.5 kW natural gas PAFCin the USA, Canada, and Japan. A 10-year study of Gas

Research Institute (GRI) and DOE stated a mean lifetimeof 6500 h (1976–86).

In the 1980s, the US Navy tested PAFCs for use insubmarines. Japan launched the pathbreaking ‘moonshineprogram’ (1981) for the development of energy-savingtechnologies. A number of companies built PAFC powerplants: Westinghouse (1980), Engelhard (1986), Toshiba(1982), Mitsubishi (1984), Fuji (1990), Sanyo (1986), andHitachi (1990).

Engelhard (1980–83) powered forklifts and buses byliquid-cooled PAFCs that were fed by the hydrogen froma methanol reformer. The liquid coolant was moreeffective than air.

ERC and LANL, between 1987 and 1991, powered acity bus by a 36 kW PAFC, fueled by reformer methanol;it was a hybrid system of fuel cell and Ni–Cd accumu-lator. Kinetics Technology (KTI) built the first EuropeanPAFC plant (25 kW) in 1989.

Since 1990, ONSI, the sales company of UTC,Toshiba, and Ansaldo (Italy), has delivered 200 kW‘PC25’ units. By 1998, 160 plants were establishedworldwide, with 19 in Europe. The lifetime was estimatedbeyond 6800 h. The advanced types, PC25B and PC25C,were introduced in 1993 and 1997, respectively. Sta-tionary PAFC plants have since delivered both electricalenergy and useful heat, for example, in hospitals and forindoor swimming pools.

In 1994, H-Power and Fuji powered a city bus by a50 kW methanol PAFC and an additional lead–acidbattery. Applications in vehicles were undertaken byMitsubishi and by Nissan (2003).

No other technology but the PAFC has influencedthe development of solid polymer fuel cells so strongly,especially with respect to carbon materials andcatalysts.

Phosphoric Acid Fuel Cell Plants in Japan

Japan is the worldwide leader of commercial PAFC util-ization, although the PEM fuel cell has been favored since1995. Megawatt plants, 2 MW and more, have not beenrealized with any other fuel cell technology but the PAFC.

In 1970, Tokyo Gas and Osaka Gas established 12.5 and40 kW PAFCs, imported from the USA. Fuji Electric Co.

started to develop PAFC in 1973. Between 1989 and1999, Fuji installed 25 PAFC plants rated at 50, 100, and500 kW at Tokyo Gas, Osaka Gas, and Toho Gas, re-spectively. The latter three companies operated an addi-tional 20 ‘PC25A’ of Toshiba/IFC.

By the end of the 1980s, the time was ripe for amegawatt plant. Toshiba/IFC set up an 11 MW PAFC forTokyo Electric Power Co. (1989–97; Figure 12). Theworld’s largest PAFC plant consisted of eighteen 650 kWstacks and reached, after a year of construction and ashort period of testing, its rated power in April 1991. In 7years, the plant operated for 23 140 h and generated77 842 MWh of energy. Net AC electric efficiencyreached an impressing 41.8% (at 11 MW), and 83% ofthe feedstock (methane) was converted into electricity;waste heat utilization was 32.2%. The degradation of thecell stacks was >10% in 40 000 h. Critical points werethe corrosion of stack housing and air electrodes, and thereliability of the gas generation system.

In 1994, Fuji had gathered testing experience onvarious plants from 50 to 500 kW and up to 15 000 op-erating hours. In addition, a hybrid city bus powered by aPAFC was available.

In 1996–97, Kansai Electric Power Co. reported a lifeof 6410 h for a 5 MW PAFC.


In 1999, 70 of 162 PAFC plants ever installed in Japanwere still running: 500 kW (2), 200 kW (46), and 50–100 kW (22).

In 2001, Mitsubishi and Fuji offered commercial PAFCplants.

Gasoline Fuel Cells

Usually, natural gas is employed as the fuel, althoughhydrogen has been successfully used.

Naphtha, kerosene, butane, and biogas were tested inPAFC by Fuji and Toshiba in the mid-1990 s. Unfortu-nately, the conversion of light petroleum fractions andliquid gas requires complicated desulfurization and steamreforming processes.

Mobile Applications

A research group at Georgetown University realizedzwei buses powered by PAFC stacks. The first generation(1994) combined a 50 kW PAFC of Fuji with a 40 kWhNi–Cd battery. The second generation (1998) used a100 kW PAFC of UTC and a 50 kWh lead–acid battery.Hydrogen was provided by methanol reforming. Thelater development focused on PEM fuel cells.

High-Temperature Fuel Cells

Molten Carbonate Fuel Cell

The generation of electricity in molten electrolytes datesback to the early twentieth century. In 1911, R. Beutner, ascholar of F. Haber, investigated palladium foil as a hydrogendiffusion electrode in fused KF/NaCl at 600–800 1C.

Until 1939, E. Baur (Germany) and coworkers de-veloped fuel cells using fused salts and air electrodes. Thebasic cell of 1910 comprised an iron vessel containingmolten sodium hydroxide (380 1C) and a magnesiumoxide (MgO) diaphragm and was fueled by sugar, carbonmonoxide, lignite, town gas, saw dust, and heavy oil.

Molten silver to improve oxygen reduction was addedin 1912. The anode was of coal or platinum. The elec-trolyte was chosen from soda, potash, borax, or kryolith.The fuel gas was hydrogen or carbon monoxide. In 1921,an iron rod anode and iron oxide or magnetite as cathodewere used in molten alkali carbonate, which was absorbedin a porous magnesium oxide ceramics (at 800 1C).

Platinized graphite as hydrogen electrode was ren-dered hydrophobic by paraffin (1933). In 1935, the dis-covery followed that carbon dioxide in the airstreamimproves the concentration polarization at the cathode inmolten carbonate – an important result for later moltencarbonate fuel cells (MCFCs).

Between 1958 and 1969, G.H.J. Broers and Ketelaar

(Amsterdam) developed a fuel cell with molten alkalicarbonate covered on a magnesia plate or adsorbed in amagnesium oxide pellet at 650 1C. The catalyst was silver

on the cathode side and nickel powder on the anode side,each plated on a perforated steel plate to allow the accessof humidified natural gas. A cell voltage of 0.7–0.8 V wasachieved at current densities of 50–100 mA cm�2.

Early work on the MCFC was done by S. Baker, In-stitute of Gas Technology, Chicago (1960), and promotedby the DOE and Electric Power Research Institute(EPRI, 1975–85).

In 1981, Mitsubishi, Fuji, Hitachi, and Toshiba re-ported cell voltages of 0.74–0.69 V at current densities of150 mA cm�2 in a 10 000 h test.

Around 1990, screen-printed lithium aluminate(LiAlO2) layers were introduced. Prior to this, hot-pressed electrolyte tiles and pastes had been used. De-velopments were under way with MTU, RWE, andRuhrgas in Germany. On the contrary, Siemens-KWUstopped its MCFC program at that time.

Between 1991 and 1996, M-C Power built a 250 kWmodule with ‘internally manifolded heat exchanger’. In1992, ECN (Netherlands) and Chicago Institute of GasTechnology achieved 5000 h life with a 2 kW MCFC stack.

Energy Research Corporation (ERC, later Fuel CellEnergy (FCE)) operated a 70 kW MCFC for 2000 h(1992). A 120 kW system with internal reforming ofnatural gas was tested for 250 h (1993). A 2 MW plant wasinstalled in Santa Clara in 1995.

Around 2000, MCFC was investigated in Europe byMTU Friedrichshafen (Germany), ECN (Netherlands),and Ansaldo (Italy); in the USA, by ERC/FCE and IFC/UTC and others; in Japan, by Hitachi, IHI, Mitsubishi,and Toshiba.

In 2004, MTU and FCE manufactured 250 kW com-bined heat and power plants. The MCFC can di-rectly be fueled by natural gas, thanks to an internal re-forming process at a catalyst in the anode chamber(CH4þ 2H2O-CO2þ 4H2 at 650 1C). Electric effi-ciencies of 47% were reported; total system efficiencies ofup to 90% are possible, when the exhaust gas temperatureof 400 1C is used in a gas turbine. About 35 000 operatinghours were reached. Critical points are the sulfur contentof the fuel, the circulation of carbon dioxide, corrosion andphase changes, short circuits by dissolution of the nickeloxide cathode, and deposition of nickel at the anode.

In Japan, IHI is developing a 300 kW system withexternal gas refinement. Marubeni Corporation is oper-ating 250 kW modules with internal reforming at at-mospheric pressure. There is a close cooperationbetween Marubeni and FCE. The latest FCE powerstations provide several megawatts of electrical energyand can be combined with a gas turbine (Figure 13).

Ansaldo (Italy) is developing 100 kW modulesfor electric power plants in the range of 500 kW–5 MW.The MCFC must reach a cost limit of about 1.500h kW�1 to compete with conventional block heat andpower plants.

Figure 13 Molten carbonate fuel cell (MCFC), manufacturer’s

label ‘DFC’, direct fuel cell of Fuel Cell Energy (FCE) combined

with a gas turbine. Rated electric power was from 300 kW to

2.4 MW, and electric efficiency 65%. Fuel was natural gas.

1

O2O2

3

2

4

5

−

+

Figure 14 Carbon–oxygen cell of Baur and Preis (1937): 1,

carbon rod; 2, carbon powder; 3, solid electrolyte tube; 4,

magnetite; 5, cathode vessel. Reproduced from Kurzweil P

(2003) Brennstoffzellentechnik (Fuel Cell Technology).

Wiesbaden: Vieweg.


Solid Oxide Fuel Cell

Technology and power plants

Modern solid oxide fuel cells (SOFCs) have beenmanufactured in three designs: tubular, flat, and mono-lithic. The solid electrolyte dates back to 1897, when W.

Nernst invented the ‘Nernst pin’ (ZrO2/15% Y2O3 ¼yttrium-stabilized zirconium dioxide (YSZ)) as a sourceof light. In 1935, W. Schottky, a student of Nernst, who wasworking by Siemens, suggested the SOFC using Nernst’sceramic mass.

E. Baur (Germany) recognized in 1939 the SOFC as acurrent source ‘without polarization’. However, con-ductivity and stability of solid electrolytes were poor atthat time. Between 1937 and 1939, E. Baur and H. Preisinvestigated clay, kaoline, and ‘Nernst mass’ in cells withcathodes of coke or iron, through which air was blown,and anodes of magnetite. The fuel gas was hydrogen,carbon monoxide, or town gas. They observed open-circuit potentials of 0.7–0.83 V.

In their carbon–oxygen element of 1937, a carbon rodanode was surrounded by carbon powder in a tube ofsolid electrolyte (Al2O3þWO3þCeO2), and dipped in avessel filled with magnetite, in which air was blown(cathode), as shown in Figure 14.

O. K. Davtyan (Russia, 1938–71) improved the Baurcell. In 1946, he was able to measure 0.79 V at 20 mAcm�2 (at 700 1C, town gas). In 1951, the addition of 15%calcium oxide (CaO) was found to improve the con-ductivity of the Nernst mass decisively.

In 1958, Westinghouse Electric Corp. (USA) introducedthe tubular design, which allowed 0.7 V at 1 A cm�2.Later, ‘Air Electrode Supported Design’ completed po-rous cathode tubes. In 1986, a 400 W stack of 24 cells wassuccessfully operated for 1760 h with H2/CO. A yearlater, 3 kW stacks were delivered to Tokyo Gas andOsaka Gas, which survived the operation under naturalgas for 5000–15 000 h; degradation was 2% per 1000 h.

The 25 kW plant for Osaka Gas and Tokyo Gas endured7064 h (1992–94) (Figure 15).

In 1980, thermal spraying (chemical vapor deposition(CVD)) allowed the fabrication of laminated layers.

In 1983, Argonne National Lab. (USA) introduced themonolithic design, which did not require any supportingstructure. Cathode, solid electrolyte, and anode formed awavelike composite, which was terminated by an upperand a lower current collector (interconnect). Fuel and airwere flown in the space between the current collectorand the pressed honeycomb laminate. Allied Signal Corp.,after further development, reported 1.0 V at 0.1 A cm�2

and 1050 1C with this design in 1992.In Japan, Fuji Electric Corp. demonstrated 0.22 W cm�2

and 1.07 V in 1990. Developments in Germany wereunder way at Siemens-Westinghouse, Dornier, MBB, andresearch institutes (DLR, FhG, and FZ Julich).

Siemens flat cell design – a variant was also developedby Dornier (1988–97) – employed a bipolar stack of singlecells. The bipolar plate (interconnector) was of high-temperature superalloy (such as CrLa2O31); the anodeconsisted of nickel ceramic metal, the cathode for ex-ample of LaSrMnO3, screen-printed on the solid elec-trolyte of ZrO2/Y2O3/CaO. Siemens obtained 0.6 V at100 mA cm�2 (20% H2 in N2 at 950 1C) in 1988, andimproved the design to 0.8 V at 500 mA cm�2 in 1993.

A Westinghouse 110 kW SOFC plant, which was in-stalled in the Netherlands in the late 1990s and run laterin Essen (Germany) and Turin (Italy), has been operatedfor more than 35 000 h. In 1999, a 220 kW hybrid plant ofSOFC and gas turbine was realized in California, whichwas fueled by natural gas or town gas and delivered anelectric efficiency of 53% – a world record. Later, 250 kWplants followed in Toronto and 300 kW in Pittsburg.

Nickel felt (+)

Interconnector

Anode

Cathode

Solidelectrolyte

Cathode collector

Anode collector

/1 2+2e

−2e H2O

O2H2

O2−

Figure 15 Tubular solid oxide fuel cell (SOFC) design of Siemens-Westinghouse. Reproduced from Kurzweil P (2003)



In 2002, H-Power and Siemens-Westinghouse presented a5 kW propane-fueled SOFC for use in Alpine huts andnational parks. Hybrid power plants of a 1152-cell SOFCand a gas turbine endured over 3700 h (in 2001). Later,1 MW plants followed for EnBW and Electricite deFrance. In 2003, 250 kW plants (called ‘e|cell CHP 250’)were field-tested at E.ON and municipal utilities.

In 2005, Siemens-Westinghouse installed in Hannovera 125 kW system, which was the basis for the later ‘SFC-200’, providing 125 kW of electrical energy and 100 kWofthermal energy at an electric efficiency of 44% and atotal efficiency of 80%.

In Japan, Mitsubishi Heavy Industries (MHI) and Chubu

Electric Power Co. are active in the field of 200–300 kWSOFC plants. Smaller systems are in development byHitachi, TOTO, Acumentrics Japan, Sumitomo, Sanyo,New Nippon Steel, and Mitsubishi Materials.

Rolls-Royce is developing a 1 MW SOFC gas turbinehybrid. ZTEK (USA) is arranging 25 kW stacks to200 kW SOFC hybrid plants. In the USA, the SOFC isattracting increasing attention for a future utilization ofcoal with CO2 sequestration (Figure 16).

Solid oxide fuel cell heating systems

In 2000, Sulzer-Hexis (Switzerland) employed SOFC forenergy and heat supply in private households. Flat cir-cular cells (12 cm in diameter, B0.15 mm in thickness)having an inner hole of 2 cm diameter were stacked to the‘heat exchanger integrated stack’. The self-supportingYSZ electrolyte was coated with an anode layer and acathode layer. The metallic interconnector (a chromiumalloy) between the single cells and including flow chan-nels served simultaneously both as a heat exchanger anda current collector. The 70-cell stack was operated withnatural gas (inside) and air (outside) and delivered a ratedpower of 1053 W (27 A, at 950 1C). The life was reportedto be lower than 6 months around 2003. More than ahundred such systems have been tested. In 2006, thedevelopment was transferred to the Swiss ‘Hexis’ foun-dation, because the market launch was not foreseeable.

The ‘Galileo 1000 N’ system provides 1 kW of electricalenergy and 2.5 kW of heat energy; with the use of anadditional burner, a heat output of 20 kW is possible.

In Germany, Vaillant, in cooperation with Webasto aswell as EBZ, is developing SOFC heating systems forhouses. In Japan, from 2005 to 2008, Kyocera, Mitsubishi-Kansai El., NGK, TOHO Gas, and Sumitomo developed10 kW SOFC systems. In Australia, Ceramic Fuel Cells

Limited (CFCL) has been developing 1 kW stacks (Gen-nex) in planar technology for domestic use.

Versa Power Systems (US/Canada), since 2000, has beendeveloping a stationary 3–10 kW SOFC system usingnatural gas. FC Technologies (Canada), supported by Sie-mens-Westinghouse, is developing a 5 kW system. Pro-pane, natural gas, and town gas are considered as themost important fuels at present. Smaller SOFC systemsare investigated by Wartsila (Finland), in cooperationwith Haldor Topsoe (Denmark), as well as byFUCELLCO AG (Switzerland), HTceramix (CH), andCERES Power (UK).

Auxiliary power units

The US Solid State Energy Conversion Alliance (SECA),a public–private partnership since 1999, pursues thecommercialization of SOFC systems for stationary, mo-bile, and military applications; members in this programinclude Siemens-Westinghouse, Delphi, GE, CumminsPower Generation, Acumentis, and FCE.

In 2001–02, BMW, Delphi Automotive Systems, andDLR developed an onboard APU for cars including anSOFC. Ce0.9Gd0.1O2 was introduced as electrode ma-terial. Auxiliary power units are designed as stationaryand mobile power supplies, for example, for enginestarting and high-efficiency automotive onboard elec-trical systems in automobiles, ships, and aircrafts. InGermany, besides BMW, Staxera Dresden is active;ALPPS is active in Austria.

Delphi’s ‘Gen 2 A’ of 2003 delivered 220 W of elec-trical energy, followed by ‘Gen 2B/2 C’ in 2004 (423 W,3.3% efficiency), ‘SPU 1 A’ in 2005 (1180 W, 17%

Figure 16 Left: Siemens-Westinghouse 110 kW solid oxide fuel cell (SOFC) plant. Right: CEFL (Australia): 1, stack; 2, pre-reformer,

steam generator, burner, heat exchanger; 3, air supply and filter; 4, water supply; 5, high-temperature insulation. Reproduced from

Kurzweil P (2003) Brennstoffzellentechnik (Fuel Cell Technology). Wiesbaden: Vieweg.


efficiency), and ‘SPU 18’ in 2006 (2160 W, 38% effi-ciency). A useable life of 5000 h has been reported. Thestart-up from room temperature to 750 1C lasts 3 h.

Portable SOFC units

The SOFC technology opens up the utilization of ‘lo-gistic fuels’ such as propane, butane, kerosene, and diesel,and the SOFC is attractive owing to the higher powerdensities and efficiencies in comparison with the DMFC.Portable systems are developed in the USA by ITNEnergy Systems, Microcell, Nanodynamics, MesoscopicDevices, Adaptive Materials, in Europe by Allps (Aus-tria), Adelan (GB), Swiss institutions (OneBath/ETH,Dantherm, EPF Lausanne, and HTceramix), and in Japanby TOTO/Hitachi and AIST.

For example, NanoDynamics’ ‘Revolution 50’ provides50 W/12 V and can be operated for a period of 36 h by a410 ml tank of propane. Mesoscopics Devices (ProtonexTechnology Corporation) has developed 75 and 250 W‘MesoGen’ units for military applications, which arefueled by 770 and 2110 ml of kerosene per day,respectively.

Nomenclature

Abbreviations and Acronyms

ABS
acrylonitrile butadiene styrene plastic
AFC
alkaline fuel cell
APU
auxiliary power unit
CFCL
Ceramic Fuel Cells Limited
CGH2
compressed gaseous hydrogen
CH
Swiss patent
CUTE
Clean Urban Transport for Europe
CVD
chemical vapor deposition
DE
German patent
DFC
direct fuel cell
DMFC
direct methanol fuel cell
DOE
Department of Energy
EADS
European Aeronautic Defence and
Space Company

EFC
European Fuel Cell
EPRI
Electric Power Research Institute
EPSI
Energetic Power Systems
ERC
Energy Research Corporation
FCE
Fuel Cell Energy
FR
French patent
GB
British patent
GRI
Gas Research Institute
IFC
International Fuel Cells Corp.
IPT
Independent Power Technology
KTI
Kinetics Technology
LANL
Los Alamos National Laboratory
LPG
liquefied petroleum gas
MCFC
molten carbonate fuel cell
MHI
Mitsubishi Heavy Industries
PAFC
phosphoric acid fuel cell
PEM
proton-exchange membrane
PEMFC
proton-exchange membrane fuel cell
PTFE
polytetrafluoroethylene
RFCS
regenerative fuel cell system
SECA
Solid State Energy Conversion Alliance


SFC
Smart Fuel Cell
SOFC
solid oxide fuel cell
SPE
solid polymer electrolyte
UPS
uninterruptible power supply
US
US-American patent
UTC
United Technologies Corp.
ZEV
zero-emission vehicle
Further Reading

Bacon FT (1952) GB Patent 667298; (1955) GB Patent 725661.Baur E and Preis H (1937) Zeitschrift fur Elektrochemie 43: 727--732.

(1938) 44: 695–698; (1939) Bull. Schweiz. Elektrochem. Verein 30:478–481

Baur E, et al. (1910) Zeitschrift fur Elektrochemie 16: 286--302; (1912)18: 1002–1011; (1921) 27: 199–208; (1933) 39: 148–167, 168–180;(1934) 40: 249–252; (1935) 41: 794–796; (1937) 43: 725–726 (onMCFC).

Blomen LJ and Mugerwa MN (eds.) (1993) Fuel Cell Systems. NewYork: Plenum Press.

Bossel U (2000) The Birth of the Fuel Cell, 1835–1845 including the firstpublication of the complete correspondence from 1839 to 1868between Christian Friedrich Schonbein (discoverer of the fuel celleffect) and William Robert Grove (inventor of the fuel cell).Oberrohrdorf, Switzerland: European Fuel Cell Forum.

Davtyan OK, et al. (1946) Bull. Acad. Sci. USSR, Dept. Sci. Technol 1:107--114. (1946) 2: 215–218; (1970) Soviet Electrochemistry 6:773–776.

Euler K-J (1974) Entwicklung der elektrochemischen Brennstoffzellen.Munich: Thieme.

Grove WR (1839) Philosophical Magazine III 14: 127--130. (1842) 21: 417–420; (1854) 8: 405; (1833) Proceedings of the Royal Society of London4: 463–465; (1845) 5: 557–559.

Haber F, Brunner L, and Moser A (1904) Zeitschrift fur Elektrochemie10: 697--713. (1904) 11: 593–609; (1906) 12: 78–79; (1906)Zeitschrift fur Anorganische und Allgemeine Chemie 51: 245–288,289–314, 356–368; (1907) Austrian patent 27,743.

Jacques WW (1896) Harpers Magazine 26: 144--150.Justi EW (1963) Seventy years fuel cell research. British Journal of

Applied Physics 14: 840--853.Kordesch K, Gsellmann J, Cifraina M, et al. (1999) Intermittent use of a

low-cost alkaline fuel cell-hybrid system for electric vehicles. Journalof Power Sources 80(1–2): 190--197.

Kordesch K and Simader G (1996) Fuel Cells and Their Applications.Weinheim: Wiley VCH.

Kurzweil P (2003) Brennstoffzellentechnik (Fuel Cell Technology).Wiesbaden: Vieweg.

McNicol BD, Rand DAJ, and Williams KR (1999) Direct methanol–airfuel cells for road transportation. Journal of Power Sources 83(1–2):15--31.

Muller E (1922) Zeitschrift fur Elektrochemie 28: 101.Posner AM (1955) Fuel 34: 330--338.Rideal EK (1958) Zeitschrift fur Elektrochemie 62: 325--327.Sandstede G, Cairns EJ, Bagotzky VS, and Wiesener K (2003) History

of low temperature fuel cells. In: Vielstich W, Lamm A, and GasteigerHA (eds.) Handbook of Fuel Cells – Fundamentals, Technology, andApplications, vol. 1, ch. 12, p. 145. Chichester: John Wiley & SonsLtd.

Schmid A (1923) Die Diffusionsgaselektrode. (1924) Helvetica ChimicaActa 7: 370–373. Stuttgart: Enke.

Spengler H (1956) Brennstoffelemente. Angewandte Chemie 68: 689.Strasser K (1990) The design of alkaline fuel cells. Journal of Power

Sources 29: 149--166.Yokokawa H and Sakai N (2003) History of high temperature fuel cells.

In: Vielstich W, Lamm A, and Gasteiger HA (eds.) Handbook of FuelCells – Fundamentals, Technology, and Applications, vol. 1, ch. 13,p. 219. Chichester: John Wiley & Sons Ltd.

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Fuel Cells Evolution 2009