HIDROGENO REVISION.pdf

7/27/2019 HIDROGENO REVISION.pdf

1/6

20 Te Tenology Tee March 2010

Introduction

One of the most signicant technological issues ofthe 21st Century is nding a way to fulll our energy

demands without destroying the environment throughglobal warming and climate change. Worldwide humanpopulation is on the rise, and with it, the demand formore energy in pursuit of a higher quality of life. In themeantime, as we use up our fossil fuel energy supplies, thequality of our environment is diminishing. By nding away to provide clean, sustainable, environmentally friendlyenergy, we can reduce greenhouse gas emissions and helpreverse the negative trends aicting our planet (Sweet,2006). One very promising technology that is currentlybeing utilized and is continually being improved is the

By David Brus and Doug Hotek

Exploring Hydrogen Fuel CellTechnology

Through simplicity in design

and functionality, and most of

all environmental friendliness,

hydrogen fuel cells can make

a signicant contribution as

an alternative solution to our

countrys energy dependence on

fossil fuels.

hydrogen fuel cell (HFC). It is an energy-conversion devicethat converts hydrogen fuel into usable electricity. HFCtechnology has the potential to help satisfy the rapidly

growing energy demands of the world, and in turn, improvethe quality of our environment. With this kind of potential,research and development in HFC technology continues toproduce viable energy alternatives through the combinedeorts of many scientists, engineers, and technologists(Borowitz, 1999).

e aim of this article is to provide an overview of HFCtechnology, and with it, a description of its simplicity indesign and functionality. In addition, a rationale for HFCcontent and several strategies for teaching about thisexciting technology are presented.

What is a Hydrogen Fuel Cell?An HFC is an electrochemical device that acts to convertchemical energy directly into electrical energy. e entireelectrochemical conversion process is accomplished cleanlyand eciently without the use of any moving parts. Duringthe process, a fuel of hydrogen-rich compounds is convertedinto electricity in the form of direct current that can be usedmuch like a battery, as long as the fuel is supplied to thecell. A combination of fuel cells can be connected in seriesor parallel circuits in order to increase electrical voltage orcurrent output. Stacking cells together in series or parallelcreates what is termed a fuel-cell stack. A variety of fuel celldesigns are being pursued and developed for a wide variety

of applications. Many of these designs have already beenimplemented and continue to gain acceptance as eectivemeans of providing electrical power.

e multitude of HFC designs are classied by the type ofelectrolyte that they employ. Electrolyte types determinehow the HFC functions, specically, the temperature rangeat which they operate, the catalysts they utilize, the fuelthey require, and other factors upon which they depend(USDOE, 2007; Hoogers, 2003). Of all currently utilizedHFC designs, the Proton Exchange Membrane (PEM) fuel


2/6


cell can serve as the focus of beginning HFC instruction,because of [its] simplicity, viability, quick start-up, and

ability to be utilized in almost any conceivable application,from powering a cell phone to a locomotive (Sammes,2006, p. 27). e PEM fuel cell functions through the useof a specially designed and produced polymer that acts tocreate a voltage dierence with the addition of hydrogenfuel and oxygen (Basu, 2007; Hoogers, 2003; Sammes, 2006).A complete breakdown of the PEM fuel cell can be seen inFigure 1, illustrating the simplicity of its components in bothdesign and functionality.

How do Hydrogen Fuel Cells Function?

PEM fuel cells run on hydrogen and oxygen and produceonly electricity, water, and excess heat as by-products oftheir operation. The production of electricity happensthrough an electrochemical process known in scienceas an oxidation-reduction (redox) reaction, whichtakes place at the anode and cathode of the fuel cell.In this type of reaction, what actually occurs are twosimultaneous half reactions. At the anode of the fuel cell,hydrogen is being oxidized (losing electrons), and at the

cathode, oxygen is being reduced (gaining electrons).Fuel cells function by capitalizing on the movement ofthe electrons that takes place in this redox reaction. Thisis accomplished by routing the electron flow through anexternal circuit that can be used to power electrical loads(Kotz 1999). The end result of this reaction is an efficientconversion of hydrogen fuel into usable electricity. PEMfuel cells have a theoretical maximum efficiency of 83%;however, to obtain a usable amount of power, fuel cellsoperate at lower efficiencies, usually between 30 and60% (Barbir, 2005). In this way, the fuel cell can produce

an adequate amount of electrical power for practicalapplications. From a system viewpoint, the functional

simplicity and associated environmental benefits of HFCtechnology can be examined in Figure 2.

Although the science embedded in the functionality of thePEM fuel cell is more complex than can be covered in thescope of this article, the following seven steps (Basu, 2007;Hoogers, 2003; Sammes, 2006) are illustrated in Figure 3 toprovide a quick summary of how the technology works.

1. Gaseous hydrogen fuel enters on the anode (-) sideof the PEM fuel cell. Here at the anode, hydrogen isoxidized and gives up electrons. Prior to use, hydrogengas is either stored in a compressed gas cylinderor obtained from water on the spot through theelectrolysis process. In the production of hydrogenthrough electrolysis, electricity is used to break waterinto hydrogen and oxygen gas.

2. Gaseous oxygen enters on the cathode (+) side of thePEM fuel cell. Here at the cathode, oxygen is reducedand gains electrons. Oxygen can be introduced tothe cathode side of the fuel cell via exposure to theatmosphere (using a compressor or blower) or by pipingcompressed oxygen to the cathode side of the cell, much

like hydrogen was introduced to the anode in Step 1.e major benet of feeding fuel cells pure oxygen isthat each cell achieves a 50-millivolt gain in potentialas opposed to cells operating on air. Additionally, as asystem, pure oxygen-fed fuel cells have greater poweroutput and higher eciencies because they do nothave to power a pump or compressor to obtain oxygenfor the fuel cell; it is already available in storage tanks(Barbir 2005). Pure oxygen-fed fuel cells, however, arelimited to stationary power applications due to thediculty of handling compressed oxygen.

PEM HFC Components

PEM HFC Assembled

Cathode collectorplate

Negative terminal

Hydrogen inlet

Anode collector plate

Hydrogen outlet

Hydrogen flow plate

Gasket

Gasket

Cathode, PEM, Anode(Membrane Electrode Assembly)

Oxygen flow plate

Positive terminal

Inputs

Hydrogen Fuel Cell Functionality

Outputs

Hydrogen

Oxygen

Fuel Cell

Electricity

Heat

Pure Water

Figure 1.

Figure 2.


3/6


3. e hydrogen gas interacts with the platinum-basedcatalyst on the anode side of the fuel cell, and this acts

to break hydrogen into the one proton and one electronof which it is composed. is is the oxidation reactiontaking place.

4. e hydrogen protons are able to diuse throughthe polymer-based electrolyte, which is sandwichedbetween the anode and cathode, but the hydrogenelectrons cannot. e polymer electrolytes abilityto restrict the ow of hydrogen electrons whilesimultaneously supporting the ow of protons is howthe voltage dierence is created by the PEM fuel cell.It is this separation of charges made possible by theplatinum catalyst and specially designed polymer thatproduces all of the electricity for the PEM fuel cell.

5. A voltage dierence is created between the anodeand cathode side of the fuel cell as negative chargesaccumulate at the anode and positive charges at thecathode. Each individual cell has a limit as to howmuch charge it can maintain. erefore, the cells mustbe connected in series or parallel in what is known asa fuel cell stack. Cells are stacked until the desiredvoltage or current from the PEM cell can be achieved.

6. A conductor is connected between the anode andthe cathode, and a ow of electrons, or electricity, isproduced as the electrons ow from the anode to thecathode through an external circuit. is process can bethought of quite simply as hooking up a battery. HFC

technology can, in fact, be used to power anything abattery might.

7. As the electrons and protons reunite at the cathodeside of the fuel cell they combine with the oxygen thathas been introduced on the cathode side to form clean,potable, water. Oxygen is necessary in the function ofthe PEM cell because it provides the oxidant requiredto complete the oxidation-reduction reaction that takesplace in the fuel cell. Without oxygen, the PEM cellwould not function.

Hydrogen Fuel Challenges

As promising as HFC technology may be, it will still facesome of its largest challenges in the establishment of ahydrogen fuel infrastructure. Making hydrogen availableto consumers involves a variety of obstacles that include:production, distribution, storage, and handling. Hydrogenis not an energy source, and it is not a fuel that is naturallyavailable in usable quantities. e hydrogen fuel supplymust be manufactured. Currently, hydrogen is primarilyobtained from fossil fuels through processes that includesteam reforming of natural gas, gasication of coal, andthe partial oxidation of hydrocarbons (Barbir, 2005; Spiegel

2007). Clearly, with most hydrogen being produced fromthese sources, the concept of independence from fossil fuelsis unattainable. Hydrogen, however, also can be producedby clean sources such as the electrolysis of water, withelectricity provided by nuclear, hydroelectric, wind, or solarpower (Barbir, 2005; Spiegel 2007).

Manufacturing hydrogen is only one of the obstacles thatmust be surmounted in order to utilize hydrogen fuel.Additionally, new systems to safely distribute, store, andhandle hydrogen fuel on a large scale must be established

(Hoogers, 2003). Overcoming each of the aforementionedobstacles in providing hydrogen fuel will require aconcerted eort by scientists and engineers. Furthermore,a transition such as the move to hydrogen fuel will dependupon strong support from the government and a well-educated class of end users.

A Rationale for Fuel Cell Education

In todays energy-driven technological world, one of themost prominent obstacles that must be overcome is theneed to nd and develop a clean and sustainable energy

Figure 3.


4/6


supply that can support our modern lifestyle withoutdestroying the environment (Sweet, 2006). Hydrogen

fuel cells represent a very promising energy conversiontechnology that may help drive the transition fromdependence on fossil fuels to energy independence withhydrogen fuel. In fact, the United States Department ofEnergy believes that, in the future, hydrogen will joinelectricity as the primary energy carrier, and that hydrogentechnology will supply every end-use energy need(USDOE, 2007). e government looks at hydrogen as anenergy carrier because of the fact that it is not an energysource or a readily available fuel; it is an intermediary formof energy (Barbir, 2005).

Advocates of HFC technology, such as the California FuelCell Partnership and the South Carolina Hydrogen andFuel Cell Alliance, suggest that if HFC technology is fullydeveloped with an infrastructure to support it, the worldenergy market, as we know it, may completely evolveinto what is being billed as the coming of the hydrogeneconomy. In this scenario, HFC technology will becapable of powering our homes, cars, lawn mowers, laptopcomputers, and even our cell phones (Sammes, 2007).HFC technology may contribute to a transformation of ourpersonal and working lives. We have a chance to decreasethe threat of global warming as we implement more ofour clean energy technologies such as HFC, and fewer ofour dirty, carbon-emitting technologies of old to fulll our

energy demands (Sweet, 2006). eoretically, in a hydrogeneconomy, our country could experience seemingly endlessnew expansion opportunities through new jobs in business,industry, and customer service as we work to support theintegration of fuel cell technology into our lives (USDOE,2006). Envision this awesome picture of a booming economyintertwined with a more environmentally friendly world.However, without the help, hard work, and education of thepublic to develop, produce, and utilize these technologies,this dream of our future will go unfullled.

Educating our countrys youth about the functionalityof HFC technology is of great importance. It is todays

students who will help drive the needed changes towardclean alternative energy, for they will be the ones to feel thefuture positive or negative environmental impacts resultingfrom the energy choices we make today. It will also be theirchoice as to whether to support the development and useof new, clean, alternative-energy technologies. erefore,it is in the best interest of all that we educate our youthabout HFC technology and its potential as an energy source.We are dependent upon the help of our young peopleto overcome the many obstacles found along the way tofuel-cell implementation, and by fully educating them we

can make the transition to hydrogen fuel cells a reality. Astechnology educators, the responsibility falls upon us to

provide students with the necessary knowledge and skillsregarding HFC technology and its capability to supplyenergy for our future.

e future of HFC-based energy will require a well-educated general public in order to properly and safelyutilize the technology. It is this need for education thatprovides an excellent opportunity for technology teachersthroughout the United States. HFC technology is a subjectarea that aligns very well with Standards for TechnologicalLiteracy, Chapter 7, Standard 16Students will developan understanding of and be able to select and use energyand power technologies (ITEA, 2000/2002/2007). Infact, even if not featured in a unit of its own, in order tosuccessfully fulll Standard 16 today, students would almostcertainly need to be exposed to HFC technology. With therising importance of environmental and energy education,technology teachers may better cement their positionsand boost the signicance of technology education forall students by adding an alternative energy topic to theircurriculum (ITEA, 1996).

Instructional Strategies for Fuel Cell Technology

HFC technology can be taught through a variety ofinstructional strategies, such as design and problemsolving, cooperative learning, inquiry-based instruction,

web-based instruction, interdisciplinary instruction, andmodular instruction (Helgeson, 2003). e PEM fuelcell can be explored in an electronics class that utilizeslaboratory experiments to explore the principles of voltageor current. It also can be employed in a power and energycourse by investigating the functionality and feasibility ofHFC technology as a portable or stationary power source.

Figure 4.


5/6


References

Barbir, F. (2005).PEM fuel cells: eory and practice.

Burlington, MA: Elsevier Academic Press.Basu, S. (Ed.). (2007).Recent trends in fuel cell science and

technology. New York, NY: Springer.Borowitz, S. (1999).Farewell fossil fuels: Reviewing Americas

energy policy. Massachusetts: Perseus.Helgeson, K. R., & Schwaller, A. E. (Eds.). (2003). Selecting

instructional strategies for technology education. 52ndYearbook of Council on Technology Teacher Education.Peoria, IL: Glencoe/McGraw-Hill.

Hoogers, G. (Ed.). (2003).Fuel cell technology handbook.Boca Raton, FL: CRC Press.

International Technology Education Association. (1996).Technology for all Americans: A rationale and structure

for the study of technology. Reston, VA: Author.International Technology Education Association.

(2000/2002/2007). Standards for technological literacy:Content for the study of technology. Reston, VA: Author.

Kotz, J. C. & Treichel, P. (1999). Chemistry and chemicalreactivity (4th ed.).Orlando, FL: Saunders CollegePublishing.

Sammes, N. (Ed.). (2006).Fuel cell technology: Reachingtowards commercialization. Germany: Springer.

Spiegel, C. (2007).Designing and building fuel cells. NewYork, NY: McGraw-Hill.

Sweet, W. (2006).Kicking the carbon habit. New York, NY:

Columbia.United States Department of Energy. (03/08/2007). Types offuel cells. Retrieved, February 05, 2008, from http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html.

United States Department of Energy. (03/22/2006).News,DOE seeks applicants for a solicitation of a transition to

a hydrogen economy. Retrieved, February 12, 2008, fromhttp://www.hydrogen.energy.gov/news_transition.html.

David Brus is a high school industrial

technology teacher at Waukee High School

in Waukee, Iowa. He can be reached via

email at [email protected].

Doug Hotek is Associate Professor of

Technology Education and Training at the

University of Northern Iowa at Cedar Falls.

He can be reached via email at doug.hotek@

uni.edu.

Tis is a refereed article.

HFC technology can even be studied in an environmentalscience course to examine its potential for reducing

harmful greenhouse gas emissions while increasing powerproduction. ese are but a few of many strategies thatrepresent eective ways to immerse students minds in theexciting and challenging content of HFC technology.

Another great way to expose students to HFC technology isto employ a class project in which students build a PEM fuelcell from scratch. Using basic hand tools and readily availablematerials to individually or collaboratively make a PEM cell,such as that shown in Figure 4, students learn the simplicityand functionality of fuel cell technology. By the time studentscomplete the project, they have a thorough understanding ofwhat a PEM cell is made of and how it works.

e PEM cell-build project can be adapted to a wide varietyof technology classes. It is possible to dedicate anywherefrom two weeks to an entire semester to constructing thePEM cell, depending upon the depth of study and detaildesired by the instructor. In conjunction with building thePEM cell, students can be emerged in multiple disciplinesof study, including physics, chemistry, and advancedalgebra, as they work to obtain an understanding ofits construction and functionality. Once the fuel cell isconstructed, students are aorded the opportunity to gaineven greater knowledge by investigating electrical current,voltage, and power capabilities. Keeping this in mind,students can explore potential end uses for HFC technologyand modications that can be made to the design toimprove or make fuel cells more feasible for future use.Introducing students to HFC technology through projectand laboratory experiences will expose them to the types ofenergy-related issues that todays generations will have tocombat in the future.

Conclusion

e future of hydrogen fuel cell technology seems verypromising. rough simplicity in design and functionality,and most of all environmental friendliness, hydrogen fuelcells can make a signicant contribution as an alternative

solution to our countrys energy dependence on fossilfuels. For this to happen, more public knowledge andskills in the area of HFC technology are needed. Indeed,technology teachers have an opportunity to help fulllthese educational needs. HFC technology can be taughtin compliance with Standards for Technological Literacyin a number of dierent courses, and through a variety ofinstructional strategies students can even build a functionalfuel cell of their own. By engaging our youth in the study ofthe HFC, we help insure its full potential as an alternativeenergy technology.


6/6

Reproducedwithpermissionof thecopyrightowner. Further reproductionprohibitedwithoutpermission.

HIDROGENO REVISION.pdf

Documents

Transcript of HIDROGENO REVISION.pdf