SCIENCE, TECHNOLOGY, SOCIETY Fuel-Cell

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Fuel-Cell

f you were to ask middle level students what type of car theywould like to drive when they get their driver’s license, theywould no doubt respond with “a sports car” or an SUV. Al-though they are years away from being licensed drivers, mosthave spent considerable time contemplating their dream car.

DRIVERSWANTED

by Todd Clark and Rick Jones

Todd Clark is a science education advisor in theOffice of Science at the U.S. Department of En-ergy in Washington, D.C. Rick Jones is a highschool science teacher and Einstein Fellow fromBillings, Montana.

Fuel-Cell

ISuggesting that maybe they should consider a fuel-cell car or a hybridvehicle may generate some laughs, but may also pique their curiosity.

Recently, President Bush commented that the greatest environ-mental progress made in this century will be through technologyand innovation (Bush 2003). His administration has committed

$1.7 billion over the next five yearsfor research on the use of fuel cellsfor personal transportation (Abraham2003). While the political climateseems favorable for the developmentof fuel-cell vehicles for personal trans-portation, the market’s demand maynot be so favorable. Nonetheless,middle level students will be the next

generation of drivers and voters, and theyneed to be able to make informed decisionsregarding the nation’s energy and transpor-tation policies and understand how such de-cisions impact our environment.

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S C I E N C E , T E C H N O L O G Y , S O C I E T Y

FIGURE 1 Chemical equations

The combined chemical reaction for fuel cells is simply:

2H2 + O2 → 2H2O (1)

This is the combination of two other chemical reactions,one at the cathode:

O2 + 4H+ + 4e¯ → 2H2O (2)

and one at the anode:

2H2 → 4H+ + 4e¯ (3)

FIGURE 2 Critical-thinking questions

• What would be the advantages and disadvantages ofhydrogen as an “energy currency” relative to our currentuse of carbon-based fuels for energy storage?

• There was some expectation that battery-storage electricvehicles would be the next generation of personaltransportation. Why does that seem unlikely today? Howare fuel-cell vehicles different from electric vehicles and howare they similar? Do the same drawbacks that apply toelectric cars with batteries apply to fuel-cell vehicles?

• Fuel-cell cars will initially be more expensive than gasoline-powered cars. How should consumers decide if theadditional expense is warranted? Should the governmentprovide incentives for drivers to purchase alternatively fueledvehicles? Why or why not?

• The infrastructure of gasoline stations throughout thecountry to provide fuel for gasoline-powered cars was builtup over many decades. How would an infrastructure toprovide hydrogen to fuel-cell cars be different and is therea best method for making this transition, if it occurs?

FIGURE 3 Materials list

• Thames and Kosmos Hydrogen Fuel-Cell Car Kit (plasticcar body with water reservoir removed)

• One empty juice box (with 10-cm x 3-mm plastic straw)

• One 6-speed gearbox kit (Tamiya)

• One bag “OO” gears, shafts, and accessories for2-mm shaft (Solar World)

• Two high-speed, 2.54-cm-diameter racer wheels for 3-mmaxle with matching O-ring (Pitsco)

• Two 5-cm-diameter pulley wheels for 3-mm axle withmatching O-ring (Sargent Welch)

• Four brass sleeves (3-mm x 1-cm)

• One 30-cm x 3-mm brass axle rod

• Four alligator clips

• Two 30-cm length pieces of 20-gauge copper wire

• One bottle instant bond cement

• Four 5-mm cable staples and 4 small wood screws

• One roll electrical tape

• One utility knife

• One set small (jeweler’s) screwdrivers

• One 15-cm x 50-cm x .6-cm piece foam core

• One 15-cm x 30-cm x .6-cm piece balsa wood

• One 7.5-cm x 46-cm x .6-cm piece balsa wood

Fuel-cell technologyFuel cells generate electricity by the reverse reaction ofelectrolysis of water. In the electrolysis, electrical currentcauses water molecules to separate into their componentgases: two-parts hydrogen and one-part oxygen. In a fuelcell, hydrogen combines with oxygen to produce electric-ity, heat, and water (see Figure 1 for the chemical equa-tions used in a fuel cell).

The U.S. Department of Energy (DOE) has commit-ted resources to help teachers and the general public un-derstand the science behind this new technology and thebenefits and disadvantages of fuel-cell technology (seecritical-thinking questions in Figure 2).

Start your enginesAs an initial introduction, it may be helpful to have thestudents brainstorm what they know about hydrogen, thesources of hydrogen on Earth, and its potential uses. Askstudents if it is possible to race a model car using only dis-tilled water as fuel or how NASA provides safe electricalpower aboard the space shuttle.

The idea for using hydrogen and oxygen to produceelectricity has been around for about 100 years and prac-tical use of fuel cells to provide electrical power for spacecraft has been a reality for more than 40 years. Studentsmay be provided with the materials necessary to designand carry out several experiments that will allow them toseparate hydrogen and oxygen from water. From these ex-plorations, students will have the necessary conceptualunderstanding of electrolysis.

More than just a car raceIn May of 2003, in conjunction with the DOE’s NationalScience Bowl, 50 students from around the country par-ticipated in the First Annual Fuel-Cell Car Challenge atthe National 4-H Center in Chevy Chase, Maryland. Stu-dents had approximately 12 hours to design, construct,and race their cars in two events: driving up an inclined

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plane with increasingly steeper angles and a head-to-head,double-elimination speed race. In this competition, stu-dents were provided key components, such as a fuel cell,in addition to other materials like balsa wood and juiceboxes (for adapting this competition for use in your class-room, see the complete list of materials in Figure 3).

Students designed vehicles that were as varied as theirpersonalities, and the time limit was still long enough toallow for multiple designs and redesigns as students ex-plored their understanding of gear ratios, torque, friction,and Newton’s laws of motion. The winning team for theinclined plane test used impressive gear ratios (1,300:1)to climb a 44-degree incline, while the winning team forthe speed race used a three-wheel design (to reduce fric-tion) with a long, narrow chassis to help the car alignquickly with the guide wire.

The competition, while exciting, was secondary tolearning about how fuel cells operate, engineering designprinciples, and cooperative problem-solving skills.

Driving is learningBy building and racing these cars, students learn firsthand

two advantages of using fuel-celltechnology: (1) the fuel is hydro-gen, which is the most abundantelement in the universe and (2)the product of the internal reac-tion is water (see Figure 2), whichis far more benign than the many

products of the incomplete combustion ofhydrocarbons.

Students also discover that another ad-vantage of using a fuel cell to generateelectricity is that there are no movingparts, making it more efficient than a gen-erator. Like batteries, fuel cells can be con-nected in series and in parallel to meet dif-ferent electrical loading requirements. Inaddition, the output of a fuel cell—wa-ter—can be converted back into hydrogenand reused as fuel.

Competitions with fuel-cell-poweredmodel cars can help teachers integrateseveral science areas. Students learn

about chemistry when they study the chemical reactionsthat produce electricity and water in fuel-cell operations.Students apply their knowledge of physics when they studygear ratios, friction, Newton’s laws, and the center ofgravity in constructing their model cars. Students en-gage in engineering when they work as a team to design,modify, redesign, and test their vehicles. Finally, studentslearn about communication when they work with team-mates to develop a division of labor that will allow themto construct their cars in a timely manner. n

ReferencesAbraham, S. 2003. Remarks prepared for Secretary of Energy Spen-cer Abraham at International Energy Agency Ministerial Work-ing Dinner, Monday, April 28, 2003, Le Meridian Etoile HotelParis, available at www.evworld.com/databases/shownews.cfm?pageid=news290403-06Bush, G.W. 2003. Comments made by President George W. Bushat the National Building Museum, February 6, 2003 www.whitehouse.gov/news/releases/2003/02/20030206-12.html.

Internet resourcesDOE fuel cell information—www.eere.energy.gov/hydrogenandfuelcells/education.htmlHow fuel cells work—science.howstuffworks.com/fuel-cell.htmJunior Solar Sprint Rules—www.nrel.gov/education/student/natjssrules.htmlModel fuel-cell car kits—www.thamesandkosmos.com/store/fuelcell1.html and www.heliocentris.com/products/school.htmlNational Middle School Science Bowl—www.scied.science.doe.gov/nmsb/default.htm

Racing student-designed fuel-cell cars up an inclined plane.

Explore Fuel cells at

www.scilinks.org.Enter code SS070402