winhec fuel cell whitepaper 2003

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Fuel Cells for Portable Devices

AbstractThis paper provides information about fuel cell power sources for portable and/or wireless devices designed for the Microsoft Windows family of operatingsystems. It provides guidelines for industry designers to evaluate fuel celltechnology for inclusion in future portable and/or wireless devices.

ContentsIntroduction .................. .................. .................. .................. .................. .................. ................... ......... ...... .... 3

Basic Fuel Cell Operation .................. .................. ................... .................. .................. .................. ........ ... 3Fundamental Issues in Fuel Cell Device Operation ................. ................... .................. ....................... ... 5

Useful Power Levels ................. ................... .................. .................. .................. .................. ............... 5Efficient Power Generation ................ .................. .................. .................. .................. .......... ...... ...... .. 6Effective Power Systems ................. .................. .................. .................. .................. ................... ........ 7

Fuel Cell Technologies Applicable for Portable Devices .................. .................. .................. ........ ...... ..... 8Proton Exchange Membrane (PEM) FC ................. .................. .................. .................. ............ ...... ... 8Direct Methanol Fuel Cell (DMFC) .................. .................. .................. ................... .................. ....... ... 8Solid Oxide Fuel Cell (SOFC) .................. .................. .................. .................. ................... ........ ...... ... 9

Direct Methanol Fuel Cells ................. .................. .................. .................. ................... .................. ............. 10Detailed Discussion ................ .................. ................... .................. .................. .................. ........... ....... .. 10Design Issues ................. ................... .................. .................. .................. .................. ................. ....... .... 10

Volume ................ .................. .................. .................. .................. ................... .................. ................. 10Heat & Temperature .................. ................... .................. .................. .................. ...................... ....... . 10Humidity & Pressure .................. .................. ................... .................. .................. .................. ............ 11System Exhaust .................. .................. ................... .................. .................. .................. ................... 11Fuel Feed & Control ......................................................................................................................... 11

Integration & Other Design Factors .................. .................. .................. .................. ........................... .... 11Solid Oxide Fuel Cells .................. .................. .................. .................. .................. ....................... ...... ....... . 12

Detailed Discussion ................ .................. ................... .................. .................. .................. ........... ....... .. 12Design Issues ................. ................... .................. .................. .................. .................. ................. ....... .... 12

Volume ................ .................. .................. .................. .................. ................... .................. ................. 12Heat & Temperature .................. ................... .................. .................. .................. ...................... ....... . 12Humidity & Pressure .................. .................. ................... .................. .................. ............. ...... ....... ... 13System Exhaust .................. .................. ................... .................. .................. ....................... ...... ....... 13Fuel Feed & Control ................ .................. ................... .................. .................. .................. ....... ....... 13

Integration & Other Design Factors .................. .................. .................. .................. .................. ........... .. 13Commercialization Requirements .................. .................. ................... .................. .................. ................... 15

Fuel Selection & Infrastructure ................. ................... .................. .................. .................. ........... ....... .. 15Industry Standards & Regulatory Approvals .................. .................. .................. .................. .................. 15

Call to Action and Resources ................ .................. .................. ................... .................. ........... ....... ...... ... 16


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Fuel Cells for Portable Devices - 2

Windows Hardware Engineering Conference

Author's Disclaimer and Copyright:Copyright 2003, Dean C. Richardson, Alberta Research Council Inc.

WinHEC Sponsors Disclaimer: The contents of this document have not been authored or confirmed byMicrosoft or the WinHEC conference co-sponsors (hereinafter WinHEC Sponsors). Accordingly, theinformation contained in this document does not necessarily represent the views of the WinHECSponsors and the WinHEC Sponsors cannot make any representation concerning its accuracy. THEWinHEC SPONSORS MAKE NO WARRANTIES, EXPRESS OR IMPLIED, WITH RESPECT TO THISINFORMATION.

Microsoft, Windows, and Windows NT are trademarks or registered trademarks of Microsoft Corporationin the United States and/or other countries. Other product and company names mentioned herein maybe the trademarks of their respective owners.

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IntroductionThis paper provides information about the application of fuel cell technology toportable and/or wireless consumer electronics or computing devices.

Simply characterized, a fuel cell is a battery (an electrochemical device) in whichthe fuel for the electrochemical reaction is provided externally.

Basic Fuel Cell OperationFirst demonstrated by English barrister Sir William Grove in 1839, fuel cells operateusing the same electrochemical principles as batteries, with the notable exceptionthat the fuel and the oxidant are supplied externally. As long as both thesefeedstocks are supplied, in theory the fuel cell can operate indefinitely, in markedcontrast to batteries, which need replacement or re-charging when their energypotential is exhausted.

One useful estimate of potential can be estimated by comparing the energy densityof typical battery materials with the energy density of potential liquid fuels such asMethanol. Note that a typical Li-ion battery may yield 200 Watt-hours/liter (Wh/L)whereas Methanol yields 4700 Wh/L. Care must be exercised in gross comparisonsof this like, though, as Methanol needs to be combined in aqueous solutions to actas fuel, reducing its fuel density, and since efficiency calculations also need to betreated carefully. Still, there are substantial potential benefits in applying fuel cells inthis area

Figure 1, below, illustrates the basic concept for a generic low-temperature fuel cell:

Anode CathodeElectrolyte

Loade - e -

Fuel Air, Or Other Oxidant

OxidationH2 -> 2H

+ + 2e -Reduction

4e - + O 2 -> O2-

Products Products

H+ Proton Flow

Overall Reaction2H2 +O 2 -> 2H 2O + 4e

-

Figure 1 - Basic Fuel Cell

Figure 1 illustrates an acid-electrolyte single-cell fuel cell. A fuel feed, rich inhydrogen, is supplied to the anode, where it is ionized, freeing electrons to flowthrough the external circuit while Hydrogen ions (H +), also called protons, flowthrough the acidic electrolyte. The anode reaction generates energy, and satisfiesmass balance requirements by exhausting products that may include un-ionizedhydrogen and other trace compounds from the fuel feed.

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The electrolyte provides proton conductivity to support charge flow through to thecathode, but it also provides a barrier to electron flow, ensuring electron flow passesthrough the external circuit and load.

At the cathode, the oxygen provided by the air or oxidant feed reacts with electronsin-bound from the external circuit and H+ protons coming through the electrolyte toform water. The water is expelled, along with any other compounds in the oxidantfeed stream out through the cathode exhaust.

An alternative form of fuel cell device is the ceramic fuel cell. These devices operatein a similar fashion to that previously described, in that the process is anelectrochemical combination of fuel and oxidant across an electrolyte, but all thematerials are solid-state and operate at a much higher temperature. Often, anoxygen ion conductor replaces the proton conductor across the electrolyte as well.

Note several fundamental considerations about fuel cells of either type: First, thereis an activation energy threshold that must be crossed in order for theelectrochemical reaction to commence and continue. Crossing this threshold can beaided with the use of catalysts and also by increasing system temperature. Catalystutilization, in turn, can be aided by high surface area on electrodes.

Second, note that a plot of current through the load vs. voltage across the loadyields a slightly non-linear relationship between these variables, and power maximathat also vary with cell output. This is illustrated with the following data, taken froman ARC SOFC cell test.

Figure 2 Actual SOFC Cell Test Data (Courtesy of ARC)

This behavior (irreversible voltage drops) can stem from several causes, includingactivation losses (described earlier), fuel crossover (passing through electrolyte),ohmic or resistive losses, and concentration losses (due to local concentration

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gradients at the surface of the electrodes). Handling these parasitic losses, andother factors related to system performance, are described in the next section.

Fundamental Issues in Fuel Cell Device OperationBasic fuel cell theory, as discussed above, is well known. However, translating thetheory to practical devices raises a host of engineering issues.

Useful Power LevelsIn order to achieve useful power levels, individual cells must be designed, thencombined into stacks. Individual cells can be designed in planar or tubular layouts,with planar designs being the most popular. Planar configurations, as illustrated inFigure 3 (an example from a ceramic fuel cell), are applicable in both ceramic andnon-ceramic fuel cell systems. They are often referred to as bipolar configurations,since bipolar plates (along with Membrane Electrode Assemblies-- MEAs) are keyelements in such devices.

Figure 3 Planar Device Configuration

A representation of the Ballard system, for low temperature devices, follows below:

Figure 4 Bipolar Flow Plates (After Ballard Power Systems)

Tubular configurations have their genesis in ceramic fuel cells used in very largestationary power systems, originally pioneered by Westinghouse (Now Siemens-

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Westinghouse). Figure 5 below illustrates the Westinghouse configuration.Currently, only ceramic fuel cell systems utilize this configuration. SiemensWestinghouse continues to produce large stationary power systems using thisarchitecture, and ARC has extended the configuration into small-form-factor devicespotentially suitable for portable electronic devices. Most other system developershave opted for planar configurations.

Figure 5 Tubular Device Configuration (After Siemens Westinghouse)

Fuel cell stacks combine individual cells in series or parallel configurations toachieve useful levels of current and voltage. This is carried out using importantcomponents called interconnects. Note that examples are illustrated in bothFigures 3 and 4. Interconnects, in turn, route current that has been collected usingcurrent collectors, another important engineering challenge for practical devices.

This challenge exists because fuel cell current is generated over the entire surfaceof electrodes, and low-resistance methods of acquiring this current are required.

Efficient Power GenerationFuel cells have demonstrated potential for high efficiency. Realizing this potentialrequires scientific and engineering work to minimize the sources of loss outlinedearlier: Activation losses, fuel crossover, ohmic losses, and concentration losses.

Activation LossesMinimizing activation losses is usually done by using catalysts to lower theactivation energy required for the reaction to proceed. However, low-temperaturefuel cell catalysts are often expensive Platinum Group Metals (PGM) such asPlatinum and Ruthenium, so merely adding more PGM materials is not the solution.Research is focused on finding new materials that will catalyze these reactions.Much engineering work goes into minimizing catalyst utilization without reducingactivity by decreasing catalyst and catalyst-support particle size, thereby increasingsurface area for a given nominal electrode size.

Fuel Crossover Minimizing parasitic loss due to fuel crossover takes different directions dependingon whether one considers low-temperature fuel cells or ceramic fuel cells. Inceramic fuel cells, fuel crossover is minimized using dense electrolytes. Many low-

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temperature fuel cells incorporate membranes into their designs to reduce fuelcrossover. Fuel crossover improvements in these systems stem from developingmore selective membranes while minimizing increases in electrical resistance.Finally, another approach to minimizing fuel crossover is to use a flowing liquidelectrolyte which captures the fuel before it can reach the air electrode, though thiscomes at the cost of reducing fuel available for use in the reaction, unless it can bereturned to the fuel stream entering the anode.

Ohmic LossesOhmic losses stem from resistance stack up in the device as elements are added.This resistance comes from the electrolyte, both electrodes, and all currentcollectors. For example, adding an additional membrane into a low-temperaturesystem also introduces a small system resistance. Ohmic losses can best beaddressed through innovation in material selection, current collection, interconnects,and in system design.

Concentration LossesConcentration losses, also referred to as mass transport losses, arise due to aconcentration gradient in reactants adjacent to the electrode face. Good designpractice here moves fuel and oxidants through flowfield patterns (e.g.: serpentinelayout) that maximize reactant contact with the electrode face.

In the realm of low-temperature fuel cells, much of the effort required to minimizelosses and maximize efficiency can be consolidated in the design of MembraneElectrode Assemblies (MEAs). MEA design is an area of significant innovation, bothin terms of efforts to improve performance and also to reduce cost.

Effective Power SystemsIf one assumes that useful and efficient power levels can be achieved with fuelcells, the next step is to consider truly effective power systems incorporating thesedevices. This requires several other considerations.

Other Systems: The Balance of Plant (BOP)Fuel cells operate on hydrogen, but hydrogen presents problems in terms of availability, transportation and storage. Other fuel feed stocks are used totransport hydrogen, but then the fuel needs to be extracted, using a fuel reformerto extract hydrogen. Hence, a reformer constitutes a significant portion of the BOPfor a fuel cell device, often constituting 30% or more of system cost and mass, andrequiring significant energy from the device, lowering total system efficiency.

In addition, as mentioned earlier, fuel cell voltages and currents are variable, andneed conditioning to support operation. For portable devices, this will typically meanDC-DC conversion to levels appropriate for the device. Power conditioningconstitutes another important element in fuel cell BOP.

Finally, other elements are also required, including fuel and oxidant storage anddistribution components, pumps, sensors, and a control system to tie all the piecestogether. This constitutes the last block of components necessary for a completedevice BOP.

Dynamic OperationEffective power systems need to be designed and matched against their load.Starting up and shutting down fuel cells raise particular issues, particularly for ceramic systems. For all devices, operating temperatures need to be achieved, fueland oxidant flows need to be started appropriately, and steady state operation

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achieved. As loads vary dynamically, a fuel cell system needs to respond with sometarget latency. Achieving startup and the target latency may require additionalcomponents in the BOP. For example, a small auxiliary battery may be used to aidstartup or to supplement fuel cell power for short-duration spikes in the load.

Finally, there are several aggregate measures of system performance that can beuseful in evaluating fuel cell systems:

Name Definition Notes

System Efficiency (%) (Fuel Energy in/ ElectricalEnergy out) X 100%Overall system metric,including BOP

Fuel Utilization (%)Percentage fuel consumed infuel cell based on fuelsupplied

Volumetric Power Density -VPD (Watts/Litre)

Total system power/ Totalsystem volume

Specific energy density(Watt-hr/kg) Total energy capability/ Mass

Table 1 System Measures

Fuel Cell Technologies Applicable for Portable DevicesThere are many different fuel cell technologies, but most are only applicable to largestationary applications, often exceeding 250kW of generating capacity, andproviding high quality heat as well. Examples include Phosphoric Acid Fuel Cells,Molten Carbonate Fuel Cells, or Alkaline Fuel Cells. However, most observerswould select only one or two candidate technologies applicable for portableapplications: Proton Exchange Membrane (PEM) systems and Direct Methanol FuelCells (DMFC), which some consider a subset of PEM devices. This author arguesthat small ceramic fuel cells can also fit portable applications, based on Solid OxideFuel Cell (SOFC) technology. Each are introduced below.

Proton Exchange Membrane (PEM) FCThe PEMFC, also known as the solid polymer fuel cell, is the technology selectedby the majority of low-temperature fuel cell developers, including the largest fuel cellcompany in the world, Ballard Power Systems of Vancouver, BC. It features a solidpolymer electrolyte membrane that is acidic, furnishes excess protons to supportcharge transfer, while providing a physical barrier to fuel crossover and an electricalbarrier to electron flow (short circuits) through the membrane. The anode andcathode feature PGM catalysts and are usually configured in bipolar plateconfigurations. Hydrogen fuel is provided either by a separate fuel reformer or inhigh-pressure tanks that store gaseous hydrogen. These devices operate at lowtemperatures (typically 60-80 C) and 1 3 atmospheres pressure. Their lowtemperature tends to support rapid on/off operation, and they can work in anyorientation. However, the membrane only electrically conducts when it is wet, sowater management of PEM systems is extremely important.

Direct Methanol Fuel Cell (DMFC)The DMFC is often considered a subset of PEMFC system, since most DMFCdevices also use proton exchange membranes. Hence, many DMFC systemconsiderations (temperature, pressure, requirement for water management) areidentical to those required for PEMFC. However, on DMFC anodes the PGMcatalysts are supplemented with another PGM, Ruthenium, so methanol can beoxidized directly at the anode. This eliminates the need for a separate fuel reformer,or managing hydrogen fuel, and greatly simplifies DMFC systems. In addition,

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methanol is already available in industrial quantities and has a high fraction of hydrogen relative to the total molecular weight, so it is a good candidate for practicalsystem fuels. Unfortunately, given the small size of the methanol molecule(CH 3OH), fuel crossover is a significant challenge for these systems. In addition, thekinetics of the oxidation reaction are relatively slow, so DMFC performance can beadversely affected and can degrade over time.

This author disagrees with the assertion that DMFC devices are subsets of PEMFC,as there are some commercial entities pursuing DMFC devices that do not require asolid polymer electrolyte membrane. Instead, they use a flowing liquid electrolyte(acidic) that transports protons for the reaction, minimizes electron passage, butalso reduces losses due to fuel crossover. Finally, eliminating the membrane canreduce system resistance and potentially reduce cost as well. The potentialimprovements in performance, which can be significant, must be carefully balancedagainst the additional complexity of managing a liquid electrolyte, however.

Solid Oxide Fuel Cell (SOFC)The SOFC device is a class of ceramic fuel cell. It is a high-temperature solid statedevice. The majority of applications are in stationary or larger-format systems(vehicle auxiliary power units APUs, for example) where the high temperature canprovide high-quality heat to drive a bottoming cycle, for example. However, recentwork at the ARC has opened the door to applying SOFC devices into portabledevice applications as well. This allows other benefits of SOFC devices to bebrought to bear on the portable market. SOFC devices tend to be much moreefficient then other fuel cell technologies (rapid reaction kinetics related to higher temperature). SOFC devices can internally reform some fuels to deliver hydrogenfuel, and they can be fabricated in a variety of shapes and form factors. They alsodo not require expensive PGM catalysts to operate. Water management is simplifiedin SOFC devices, but the tradeoff comes in terms of a much more complex thermalmanagement problem for small portable devices.

DMFC and SOFC technologies will be discussed in more detail below, where for thepurposes of this discussion, DMFC will be discussed as the appropriate portable-

device realization for PEM systems.

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Direct Methanol Fuel Cells

Detailed DiscussionIn DMFC devices methanol or methanol-water solutions are fed to the anode as

fuel. Air is typically fed to the cathode as the oxidant. DMFCs offer the advantageof directly converting methanol to electric power without a reformer or fuel processor that is typical of other low temperature fuel cell systems. They also offer thepotential of the high energy density of liquid methanol fuel relative to hydrogen-based systems. The chemical reactions occurring in the DMFC are as follows:

Anode Reaction: CH 3OH + H 2O => CO 2 + 6H + + 6e -

Cathode Reaction: 3/2O 2 + 6H + + 6e - => 3H 2O

Overall Reaction: CH 3OH + H 2O + 3/2O 2 => CO 2 + 3H 2O

Most DMFC systems being developed are based on the proton exchangemembrane fuel cell (PEMFC) technology originally developed for hydrogen fuel. Inorder to use methanol as the fuel (rather than hydrogen) Pt-Ru catalysts are usedon the anode. A few technologies are being developed that are attempting toreplace the polymer membrane electrolyte with liquid electrolytes.

Design IssuesThere are several challenges to be overcome in DMFC development:

The relatively slow anode reaction necessitates high loadings of expensiveplatinum group metal catalysts.

Methanol crossover to the cathode degrades cell performance through reducedvoltage and power, cathode poisoning, reduced fuel conversion efficiency,cathode flooding.

Carbon dioxide generation at the anode can lead to mass transfer limitationsthat reduce cell performance.

Membrane-electrode assembly durability reduces the useful life of the devices

VolumeDMFC systems offer the potential for small volume and attractive form factors for portable devices due to the high specific energy content of the fuel, low temperatureoperation and the possibility to operate with essentially ambient air pressures (littleor no compression). These advantages, if realized, offer the opportunity to reducethe size and parasitic losses of the balance of plant equipment. This advantage isalready being demonstrated with prototype battery chargers (Motorola) and laptopbattery replacement (Toshiba) devices based on PEM-DMFC technology

Heat & TemperatureThe low temperature operation (typically less than 80 oC), the liquid nature of thefuel and the amount of water circulating in the process make the thermalmanagement and temperature control of DMFC systems attractive for portabledevice applications. The presence of water in the system necessitates designprovision for exposure to sub-zero temperature environments, however.

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Humidity & PressureHumidity is not as great a concern in DMFC systems as in conventional PEMsystems, for example. However, control of water flux at the air electrode (cathode)is crucial to avoid electrode flooding.

System ExhaustSystem exhaust typically consists of warm excess air, CO 2 and water vapour whichshould not present any particular problems or significant design considerations.

Fuel Feed & ControlFuel (methanol) is typically fed to the anode as a dilute (usually 0.5 to 3 moleCH 3OH per litre) solution in water. The reason for this is that methanol crossover increases with anode methanol concentration so in order to keep the crossover attolerable levels very dilute solutions are used. This necessitates the design of accurate methanol injection systems and methanol sensors to maintain optimumfuel concentration and flow rates.

Integration & Other Design FactorsA simple system schematic is found below, illustrating a number of the issuesdefined above.

Figure 6 Representative DMFC Device Schematic

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Solid Oxide Fuel Cells

Detailed DiscussionThe SOFC basic structure is same as the basic fuel cell outlined earlier, in that it

consists of three layers: the electrolyte, anode and cathode. In contrast to aPEM/DMFC system, which uses a proton exchange membrane for the electrolyte,the electrolyte in an SOFC this element is a doped metal oxide. The charge carrier across the electrolyte is an oxygen ion conducted by oxygen vacancy migrationthrough the electrolyte. One of the key electrolyte materials is Yttria-StabilizedZirconia (YSZ) where Y 3+ is a dopant and replaces Zr 4+ . To maintain chargeneutrality, an oxygen vacancy is created in the lattice. The mobility of the oxygenvacancy is extremely low at room temperature and as a result oxygen ionconductivity is low at room temperature. Therefore, a fuel cell made out of YSZneeds a high operating temperature (800-1000 C) to produce power.

PEM/DMFC devices suffer from so-called poisoning of the catalyst sites by thepresence of carbon monoxide, CO. One of the major advantages of SOFC over PEM is its fuel flexibility, in that the electrode does not get poisoned by CO. In fact,CO can even act as a fuel for SOFC devices. In addition, the SOFC device canreform or partially reform fuel internally. Historically, SOFC devices have had lowthermal shock resistance, with the result that system start up times can bemeasured in hours.

Design Issues

VolumeThe Siemens-Westinghouse tubular design mentioned earlier remains the mostdeveloped SOFC system, and has been evaluated in units generating 25kW,100kW and 200kW. Other companies have established advanced planar designs.Both types of stack designs produce a Volumetric Power Density (VPD) of less than1kW of power per liter.

ARC has pioneered technology to dramatically increase power density and reducesystem size with a High Density Tubular SOFC design. One design embodiment,dubbed Micro SOFC (SOFC), has high potential for portable applications. Theproposed SOFC has a tube diameter 2mm and total (tube) wall thickness 250 m. The thickness of the electrolyte is 5 to 15 m. Intuitively, in any unit volume onecan pack a higher number of small tubes then larger tubes. In the case of the SOFC at 2mm diameter, there is a potential increase in the VPD 10 times relativeto conventional planar SOFC devices.

Heat & Temperature

As discussed earlier, SOFC devices require higher operating temperatures toexceed activation energy levels and encourage oxygen ion conductivity through theelectrolyte. Currently, SOFC temperatures must exceed 750C to operate.Obviously, with this kind of temperature in a system, thermal management for portable devices is a crucial system design issue. One approach to deal with thisproblem is through improved materials in electrode fabrication. There is a highpotential in the near future for SOFC operating temperatures to be reduced down to~ 600 C by changing electrolyte from YSZ to cerium gadolinium oxide (CGO) or doped LaGaO 3. ARC is investigating this approach for SOFC devices. In addition,

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significant material advances are occurring in the insulation area, with new-generation aerosol-based products that offer lightweight, high thermal insulation.

Another significant aspect of system thermal management is operating cycle. Thesedevices need to support near instant-on operation, so some form of pre-heat isrequired. Advances in catalytic heating can provide flameless pre-heating for smallSOFC devices. ARCs SOFC devices promise higher thermal shock resistance in apackage with low thermal mass, which means it can pre-heat rapidly.

Lower-temperature operation, high insulation capability, and simplified, flamelesspre-heating hold the potential to address the significant thermal management issuesinvolved in small SOFC devices.

Humidity & PressureTypically, an SOFC system will include 3% moisture in the fuel gas. This reducesthe phenomena of coking, in which carbon forms on the Nickel catalyst sites andplugs pores in the electrode. This dramatically reduces performance and systemlife. The addition of moisture triggers the preferential creation of carbon dioxide,sequestering the carbon.

System ExhaustSOFC systems exhaust H 2 O, CO 2 and excess air.

Fuel Feed & ControlOne important factor is to ensure there is very low sulfur present in the fuelfeedstock. If present, some processing may be required to remove sulfur. After thisstep, liquid fuel will typically be fed through a reformer first, which will extract thehydrogen component and feed the resulting mixture through to the stack. Often, totake advantage of the heat inherent in the stack operation, the reformer will bethermally integrated with the stack. Reformation may be based on steam reformingor partial oxidation, and the output reactants will fuel the stack operation.

Integration & Other Design FactorsAn example system schematic follows below:

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Figure 7 Representative SOFC Device Schematic

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Commercialization Requirements

Fuel Selection & InfrastructureFuel selection and infrastructure is the single most important question confronting

the entire fuel cell industry. Hydrogen generation is well known, and fuel cells canprovide an effective use for the fuel. Transportation, distribution and storage raisesignificant problems. Currently, several approaches are being investigated,including:

The use of high-pressure tanks which contain hydrogen gas;

Hydrogen stored as temporarily bonded constituents in metal hydridecompounds;

Utilizing on-board reformation from conventional liquid fuels like methanol togenerate hydrogen on demand.

However, it is safe to say that no single approach has emerged to solve this

problem.Luckily, the challenge is less daunting for portable devices. In essence, the industryneeds a liquid-based fuel carrier to transport hydrogen. Many suppliers haveembraced methanol as the fuel of choice for this segment, citing the fact that thematerial is already available in industrial quantities, and the hydrogen can beextracted with ease. Methanol works directly in DMFC devices, but it also reforms ata very low temperature approx. 230C, so it can easily be used in SOFC devices aswell.

Industry Standards & Regulatory ApprovalsEven with a generally accepted fuel such as methanol available, a number of issuesremain:

Regulatory approval for transportation, particularly on aircraft

Industry-standard fuel specification for PC-grade methanol

Industry-standard fuel containers, for both distribution and point-of-usepackaging; and consumption

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Call to Action and ResourcesCall to Action: For system or device manufacturers: With many OEM fuel cell producers

announcing portable fuel cell product commercialization starting in 2004 or

2005, manufacturers need to gain familiarity with the technology, and consider how and in what products to introduce it to their customers.

Further Reading and Research: As with most fast-moving industries, the best source of current information will

be conference attendance, web information or conversations with potentialvendors or consultants in this area.

For a solid introduction to fuel cell technology in general, one highly-recommended source is: Fuel Cell Systems Explained, by James Larminie andAndrew Dicks, published by: John Wiley & Sons, in 2000.

Feedback: To provide feedback about this article, please send e-mail to co-author Dean

Richardson, of the Alberta Research Council Inc., at: [email protected] .

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