geothermal_energy.pdf

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U.S. DEPARTMENT OF Energy Efficiency &ENERGY EDUCATION AND WORKFORCE DEVELOPMENTRenewable EnergyENERGY

Geothermal Energy

(Five Activities)

Grades: 5-8

Topic: Geothermal

Authors: Laura J. W. Butterfield, Ph.D., Brandon A. Gillette,

and Richard Shin

Owner: National Renewable Energy Laboratory


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Geothermal Energy

Laura J. W. Butterfield, Ph.D.Brandon A. Gillette

Richard Shin

Middle School


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For the Teacher

Deep inside the Earth, at depthsnear 150 kilometers, the temperatureand pressure is sufficient to melt rockinto magma. As it becomes less dense,the magma begins to flow toward thesurface. Once it breaks through thecrust it is referred to as lava. Lava isextremely hot; up to 1,250 °C. Averagelava temperatures are about 750°C. Anormal household oven only reachestemperatures near 260°C (500°F)!

The rock located just above themagma is also very hot but remainssolid. What if we could harness thisthermal energy and use it to generateelectricity or heat homes andbusinesses? We would have adomestic, clean, and nearlyinexhaustible energy supply.Geothermal energy is one of thecomponents of the National EnergyPolicy: “Reliable, Affordable, andEnvironmentally Sound Energy for

America’s Future”, (pg. 6-5).Our ancient ancestors knew

about this free and reliable energy.They bathed and prepared food in hotsprings and many cultures consideredgeysers and other surface geothermalfeatures as sacred places. Today, dueto the explorations and calculations of

many scientists and engineers, we’verealized that only 1% of the geothermalenergy contained in the uppermost tenkilometers of the Earth’s crust is 500times that contained in all the oil andgas resources of the world! The nextstep is designing technology that canharness this immense, renewable, andlow to no - emission energy reservoir.

Geothermal energy can beusefully extracted from four differenttypes of geologic formations. Theseinclude hydrothermal, geopressurized,hot dry rock, and magma.

Hydrothermal reservoirs havebeen the most common source of

geothermal energy productionworldwide. They contain hot waterand/or steam trapped in fractured orporous rock formations by a layer ofimpermeable rock on top. Hydrothermalfluids can be used directly to heatbuildings, greenhouses, and swimmingpools, or they can be used to producesteam for electrical power generation.These power plants typically operatewith fluid temperatures greater than130oC.

Geopressurized resources arefrom formations where moderately hightemperature brines are trapped in apermeable layer of rock under highpressures. These brines are founddeeper underground than hydrothermalfluids and have high concentrations ofsalt, minerals, and dissolved methanegas. In addition to producing steam for

electrical power generation, mineralscan be extracted from brines and usedas supplementary revenue for a powerplant. This process is known as coproduction.

Hot dry rock reservoirs aregenerally hot impermeable rocks atdepths shallow enough to be accessible


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(


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Science and Technology¾ Content Standard E:

• Abilities of technologicaldesign

• Understandings aboutscience and technology

Science in Personal and SocialPerspectives¾ Content Standard F:

• Populations, Resources, andEnvironments

• Science and technology in

societyHistory and Nature of Science¾ Content Standard G:

• Science as a human

endeavor

• Nature of science

Technology Description

Exploration and Drilling

Many scientists, including geologists andhydrologists, chemical and civilengineers, and expert drilling

technicians come together to collect andanalyze information on thecharacteristics of a potential geothermalresource site. Sites are evaluated basedon three primary criteria: heat content,fluid content, and permeability of therock.

Fortunately for geothermalexplorers, hundreds of thousands of testholes have already been drilled all overthe world by oil and gas companies.Researchers are able to use data fromthese deep wells to obtain informationabout the thermal energy in the area.These holes can also provide a way touse structural methods such asseismicity, gravity, and magneticsurveys to help determine thepermeability beneath the surface.

Electrical resistivity surveys can showhow electricity flows through the rockand fluid beneath the surface and canhelp determine amount of availablehydrothermal fluid.

Once a site is identified as havinggeothermal potential, more exploratorywells are drilled and more data iscollected and analyzed. Only afterextensive checking and rechecking is asite recommended for development asone of the following energy conversionsystems.

Energy Conversion

The technology used to convertgeothermal energy into forms usable forhuman consumption can be categorizedinto four groups. The first three: drysteam, flash steam, and binary cycle,typically use the hydrothermal fluid,pressurized brine, or EGS resources togenerate electricity. The fourth type,direct use, requires only hydrothermalfluid, typically at lower temperatures, fordirect use in heating buildings and otherstructures. The addition of a small-scaleelectric heat pump into the systemallows the use of low temperaturegeothermal energy in residences andcommercial buildings.


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Dry Steam Power Plants Flash Steam Power Plants

These were the first type of geothermalpower plants to be built. Thetechnology was first used at Lardarello,Italy, in 1904, and is still very effectivefor generating electricity. The plantuses steam that is accessed by drillingdirectly into the underground source.The steam is piped through a turbineand generator unit, and then condensedback into water and injected back into

the subsurface reservoir. This helps toextend the life of the system. Steamtechnology is used today at The Geysersin northern California, the world'slargest single source of geothermalpower. The emissions from this group of

plants consistof excesssteam andvery small

amounts ofsulfur dioxide,hydrogen

sulfide, and carbon dioxide. Becausethere is no combustion taking place, thelevels of these gasses are much lowerthan emissions from fossil fuel firedpower plants.

In these power plants, hydrothermalfluid at temperatures greater than 360°Cis pushed to the surface by the highpressure in the subsurface reservoir. Asthis very hot fluid reaches the surface, itenters the separator where the pressuredrops instantaneously and most of theliquid flashes into steam. The forcegenerated by the steam is used to driveturbines and produce electricity. The

fluid not flashed into steam leaves theseparator and rejoins the water fromthe condenser. The fluid is then

injected backinto the Earthso that theprocess can berenewed overand overagain. An

example of an area using a flash steamoperation is the CalEnergy Navy I flashgeothermal power plant at the Cosogeothermal field.


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Binary Power Plants

These are different from dry steam orflash steam power plants in that thehydrothermal fluid from the subsurfacereservoir never comes into contact withthe turbine/generator units. In this two-step process, hydrothermal fluid that isnot quite hot enough to be used in aflash steam plant is fed into a heatexchanger. Here, heat is transferredfrom the hydrothermal fluid to a

“working liquid” with a lower boilingpoint than water (usually isobutane orisopentane). The working liquid turnsinto an energized vapor much like thesteam in the flash power plant and turnsthe turbine/generator unit, producingelectricity. The hydrothermal fluid andthe working liquid are both contained in

“closed loops” and never come incontact with each another. The vapor

from the working liquid is condensedand the hydrothermal fluid is returnedto the earth. This cycle can be repeatedas quickly as the Earth can reheat thefluid. An example of an area using aBinary Cycle power generation system isthe Mammoth Pacific binary geothermalpower plants at the Casa Diablo

geothermalfield. Becausewarmhydrothermalfluid is a morewidespreadresource than

hot fluid or pressurized brines, binarysystems have the potential to make asignificant contribution to the overallproduction of geothermally generatedelectricity.

Direct use of hot water fromgeothermal resources can be used toprovide heat for industrial processes,

crop drying, or heating buildings. Inthis method, the hot fluid is pumped

directly into abuilding’s hotwater-basedheating system,under sidewalks, orinto pools. The cityof Klamath Falls,Oregon, is locatedin an area of

abundant near-surface hydrothermalfluid at the southern part of the CascadeRange. The Oregon Institute ofTechnology is actually heated by thisdirect-use system. Sidewalks in thearea have tubes buried beneath them soas to prevent the buildup of snow andice in the winter. Other examples ofdirect use geothermal resources existacross the entire western United States

including the Capitol Mall in Boise,Idaho. Here, the city’s geothermaldistrict heating system heats even theIdaho State Capitol Building.Geothermal water is also used by localindustries in greenhouses, at fish farms,and by dairies.


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Geothermal Heat Pumps

Also called ground source heat pumps,these systems can be used for heatingand cooling buildings virtually anywhere,especially in regions where thegeothermal potential is low. The

internal heat energy of the Earth andthe insulation from surface rocks andsoils keep the subsurface at a nearconstant temperature of about 55 °F (13

°C). Wells are drilled to access the

ground water at this temperature, andtwo types of systems can be employed.

An open loop system simply pulls waterup, runs it through the heat pump toadd heat in the summer, and removeheat in the winter, and then recycles it

back into the aquifer. A closed-loopsystem has the same function, except aloop of tubing is buried undergroundand filled with fluid, usually antifreeze.These systems work well in areas withmoderate climates. Supplementalheating and cooling systems arerequired in more extreme areas. Some

consumer resistance to geothermal heatpumps does exist due to the high initialpurchase and installation cost.However, all geothermal heat pumpseventually provide savings on normalutility bills, some in as little as 3 or 4years.

Overall US Geothermal PotentialThe sources and functions of

various types of geothermal power varyacross the nation. The map belowshows that this energy can be tappedand harnessed virtually anywhere in theUnited States. Current research isfocusing on increasing efficiency of

current technologies, and expanding theuse of this resource into newapplications.

Useful sources of information aboutgeothermal energy resourcesinclude:

Web Resources:

Geothermal Education Officehttp://geothermal.marin.org

Geothermal Technologies Programhttp://www.eere.energy.gov/geothermal

http://geothermal.marin.org/http://www.eere.energy.gov/geothermalhttp://www.eere.energy.gov/geothermalhttp://geothermal.marin.org/


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Geo-Heat Centerhttp://geoheat.oit.edu

Idaho National Engineering andEnvironmental Laboratoryhttp://geothermal.id.doe.gov

National Renewable Energy Laboratoryhttp://www.nrel.gov/geothermal

Sandia National Laboratoryhttp://www.sandia.gov/geothermal

United States Department of Energy,GeoPowering The Westhttp://www.eere.energy.gov/geothermal

/deployment_gpw.htmlBooks:

Cataldi, R. Stories from a Heated Earth,Our Geothermal Heritage.Sacramento, CA: GeothermalResources Council, 1999.

Dickson, M. H. Geothermal Energy.West Sussex, England: John Wiley &Sons Ltd., 1995.

Edwards, L. M. Handbook of GeothermalEnergy. Gulf Publishing Company,1982.

Elder, J. Geothermal Systems. New York, New York: Academic Press,1981.

Magazines, Handouts, etc:

Duffield, W. A. Geothermal Energy –Clean Power From the Earth’s Heat.Reston, Virginia: United StatesGeological Survey, 2003

Geothermal Today. Washington, DC:United States Department of Energy,2004

Resources for Following Projects:

Calorimeter

Calorimeter, Student Double Walled,Science Kit, #WW6097200, $29.95(http://www.sciencekit.com)

ThermometersPlastic-back high range thermometers(-30 to 110 °C), alcohol-filled. ScienceKit #WW4600701, $1.95(http://www.sciencekit.com)

Uncoated Nails40d or larger nails from a local hardwarestore. Many stores carry both steel andaluminum nails. These will need to bebent into a U shape before the activity.

Heat Transfer Kit

This kit contains Styrofoam cups, lids,thermometers, and an aluminum heattransfer bar. Sargent Welch#WL6819R, $16.50, pkg. of 5 $82.50

Other possible science supply companiesinclude:

Carolina Biological- www.carolina.com Frey Scientific – www.freyscientific.com

http://geoheat.oit.edu/http://geoheat.oit.edu/http://geothermal.id.doe.gov/http://www.nrel.gov/geothermalhttp://www.sandia.gov/geothermalhttp://www.eere.energy.gov/geothermal/deployment_gpw.htmlhttp://www.eere.energy.gov/geothermal/deployment_gpw.htmlhttp://www.sciencekit.com/http://www.sciencekit.com/http://www.carolina.com/http://www.freyscientific.com/http://www.freyscientific.com/http://www.carolina.com/http://www.sciencekit.com/http://www.sciencekit.com/http://www.eere.energy.gov/geothermal/deployment_gpw.htmlhttp://www.eere.energy.gov/geothermal/deployment_gpw.htmlhttp://www.sandia.gov/geothermalhttp://www.nrel.gov/geothermalhttp://geothermal.id.doe.gov/http://geoheat.oit.edu/


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Project Ideas

What factors affect the heat

transfer from rock to water?

Learning Objective: The students willknow and understand that heat flow is afunction of the heat capacities of thesubstances involved in the transfer aswell as the substances’ startingtemperatures.

Controls and Variables: type of rock,mass of rock and water, starting

temperatures of rock and water, time

Materials and Equipment: Styrofoamcups with lids OR calorimeters,thermometers, water at roomtemperature, small samples of varioustypes of rocks (i.e. granite, basalt,sandstone, gneiss), mass balance,boiling water bath OR incubator to heatrocks, tongs, graduated cylinders

Safety and EnvironmentalRequirements: Caution should beused when handling hot materials.

Suggestions:Rock samples should be heated to aconstant temperature, then placed intowater of known temperature in thecalorimeter or cup. From here, thestudents can measure the total energychange or the rate of energy transfer,compare rock samples or masses of thesame rock, or even substitute differentmetals or household materials.

2 How is energy transferredbetween fluids in a binarygeothermal power plantwork?

Learning Objective: The students willknow and understand that conductioncan transfer thermal energy from oneliquid to another.

Controls and Variables: containersize, volume of liquid, temperature ofliquid, type of liquid, time, material oftransfer bar or nail

Materials and Equipment: Heattransfer kit OR Styrofoam cups w/ lids,large nails (bent into U shape), andthermometers; water at varioustemperatures, other liquids (alcohol),graduated cylinders


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Safety and EnvironmentalRequirements: Caution should beused when handling hot materials.

Alcohol is volatile and should be keptaway from any heat source.

Suggestions: Students can select fromthe many different variables in thisexperiment. For example, they candetermine the effects of large volumesof liquid on smaller volumes or varystarting temperatures of liquids. Theycan also experiment with nails ortransfer bars made from differentmetals and/or liquids with differentboiling points.

How does salinity affect the

boiling point of water?

Learning Objective: The students willknow and understand that theconcentration of solutes in a solution willaffect the boiling point of the liquid.

Controls and Variables: type of

liquid, volume of liquid, amount ofsolute, type of salt, boiling point ofsolution

Materials and Equipment:

hot plate, beakers, high rangethermometers, water or other liquids,sodium chloride or other salt, massbalance, graduated cylinders

Safety and Environmental

Requirements: As with all experimentsthat involve heating and pressure youwill need to wear eye protection andheat insulating gloves.

Suggestions: Students can selectfrom many different variables in thisexperiment. For example, they can

determine how the same salt affects theboiling point of different liquids, or howdifferent salts affect the boiling point ofwater.

4 How do the emissions from ageothermal power plantcompare to those from afossil fuel power plant?

Learning Objective: The students willknow and understand that thecombustion products from fossil fuelpower plants contain particulates (soot)and contribute to air pollution, while themajor emission from a geothermal

power plant is clean water.

Controls and Variables: fuel source,time, mass of particulates, mass of fuelsource

Materials and Equipment:combustible materials such as candles,Sterno cans, Bunsen burners, charcoal,and wood chips; matches, small pie tins

for burning materials, hot plate, teapot,water, small mirror, tongs, oven mitts,0.01 gram mass balance

Safety and Environmental

Requirements: Caution should beused when handling hot materials,especially the mirror. Fuels arecombustible and should be keptcontained while burning. When usingthe Bunsen burner, be sure to keep themirror high above the flame.


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Suggestions: Students can usemultiple fuel sources to determine theamount of particulates produced byeach source.

How does the size andnumber of turbine blades andsteam jets affect theperformance of a model drysteam power plant?

Learning Objective: The students willknow and understand that the thermalenergy in steam, when coupled with aturbine, can be converted to mechanicalenergy that can be used to generate

electricity.

Controls and Variables: size andconfiguration of turbine, size of holes inbottom of can, number of holes, spacingof holes, speed of turbine

Materials and Equipment: aluminumpie tins (8”), aluminum foil, empty soupor coffee can, 20 cm length of stiff wire

or coat hanger, cork, medium cookingpot, hot plate, duct tape, pliers withwire cutter, scissors

Safety and EnvironmentalRequirements: As with all experimentsthat involve heating and pressure youwill need to wear eye protection andheat insulating gloves. Exercise cautionwith working with sharp edges of soupor coffee can and pie tin.

Suggestions: Students can experimentwith different sizes and configurations ofholes for the steam to pass through.They can also change the configurationof the turbine blades to produce moreor less angle or change the diameter ofthe turbine. The speed of the turbine

can be calculated by putting a mark onone edge of the turbine and countinghow many revolutions it makes in aspecific amount of time.

How to Construct the ModelTurbine: Half - fill a medium saucepan with water and cap it with a securelayer of aluminum foil. Be sure to wrapthe edges under the lip of the pan tominimize steam escape. Punch a holeabout half the diameter of the coffee orsoup can in the middle of the foil.Cut a hole in the center of a pie platewith the same diameter as the foil.Place this over the foil to provide

support for the soup can. This is thesteam generator.Construct a turbine from an aluminumpie pan, making sure that the turbine issmaller in diameter than the can. Bendthe stiff wire into a hanger for theturbine and duct tape it to the side ofthe can, bottom side up. Push the corkonto the end of the hanger. Pierce theexact center of the turbine with astraight pin, then push the straight pininto the bottom of the cork to suspendthe turbine over the can. The turbineshould hang relatively horizontal andspin freely.


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More Project Ideas

What affect does water or steampressure have on geothermal energy

production?

How does the salinity and temperatureof hydrothermal fluid affect the metalsand/or plastics that are used inconstruction of a power plant?

What are the social and economicimplications of putting a power plantnear a hot spring, which are oftendeveloped at tourist areas?

What type of geothermal system wouldbe most appropriate for your state,town, school, or house? What savings,in both electricity and dollars, could ageothermal system provide to yourcommunity?


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Glossary

• binary cycle

• co-production

• dry steam

• electrical

resistivitysurveys

• Enhanced

GeothermalSystem (EGS)

• flash steam

• ground sourceheat pumps

• heat capacity

• heat exchanger

• heat flow

• hydrothermal

fluid• particulates

• pressurizedbrines

a two-part geothermal power plant that enables the use oflower temperature hydrothermal fluid by exchanging heatenergy to a liquid with a lower boiling pointthe extraction of mineral resources from hydrothermal fluidsand pressurized brines that generates additional revenue forthe power utilitya power plant that uses steam at temperatures above 100°Canalysis method that can determine the presence ofunderground water resources

method for using hot, dry rock to produce hydrothermal

fluid

a power plant that uses hydrothermal fluids at temperaturesabove 360 °C which flashes into steam as it enters the plantequipment that allows the transfer of energy into or out of ahydrothermal fluidthe amount of energy it takes to raise the temperature of asubstanceequipment that allows the transfer of energy from one fluidto another without direct contact between the fluidsthe transfer of thermal energy from a higher temperaturesubstance to one of lower temperaturewater that has been heated by the Earth and usuallycontains dissolved minerals and gassestiny particles of carbon and impurities that are released ascombustion occurshydrothermal fluids that are at high temperatures andpressures that contain high levels of dissolved solids


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Appendix

SCIENCE FAIR JUDGING GUIDELINES

Science Project Evaluation CriteriaJudging is conducted using a 100-point scale with points assigned to creative ability,scientific thought or engineering goals (II a and b respectively), thoroughness, skill, andclarity. Team projects have a slightly different balance of points that includes points forteamwork. A chart of these point values is located at the end of these criteria.Following is a list of questions for each criterion that can assist you in interviewing thestudents and aid in your evaluation of the student’s project.

I. Creative Ability (Individual – 30, Team – 25)1. Does the project show creative ability and originality in the questions asked? the

approach to solving the problem? the analysis of the data? the interpretation of

the data? the use of equipment? the construction or design of new equipment?

2. Creative research should support an investigation and help answer a question inan original way. The assembly of a kit would not be creative unless an unusualapproach was taken. Collections should not be considered creative unless theyare used to support an investigation and to help answer a question in an originalway.

3. A creative contribution promotes an efficient and reliable way to solve a problem.When judging, make sure to distinguish between gadgeteering and genuinecreativity.

II.a. Scientific Thought (Individual – 30, Team – 25)1. Is the problem stated clearly and unambiguously?

2. Was the problem sufficiently limited to allow plausible attack? One characteristicof good scientists is the ability to identify important problems capable ofsolutions. Neither working on a difficult problem without getting anywhere norsolving an extremely simple problem is a substantial contribution.

3. Was there a procedural plan for obtaining a solution?

4. Are the variables clearly recognized and defined?

5. If controls were necessary, did the student recognize their need and were theycorrectly used?

6. Are there adequate data to support the conclusions?


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7. Does the student recognize the data’s limitations?

8. Does the student understand the project’s ties to related research?

9. Does the student have an idea of what further research is warranted?

10.Did the student cite scientific literature, or only popular literature (i.e.: localnewspapers, Reader’s Digest)?

II.b. Engineering Goals (Individual – 30, Team – 25)1. Does the project have a clear objective?

2. Is the objective relevant to the potential user’s needs?

3. Is the solution workable? Unworkable solutions might seem interesting, but arenot practical. acceptable to the potential user? Solutions that will be rejected or

ignored are not valuable. economically feasible? A solution so expensive itcannot be used is not valuable.

4. Could the solution be utilized successfully in design or construction of some endproduct?

5. Does the solution represent a significant improvement over previousalternatives?

6. Has the solution been tested for performance under the conditions of use?(Testing might prove difficult, but should be considered.)

III. Thoroughness (Individual – 15, Team – 12)1. Was the purpose carried out to completion within the scope of the original

intent?

2. How completely was the problem covered?

3. Are the conclusions based on a single experiment or replication?

4. How complete are the project notes?

5. Is the student aware of other approaches or theories concerning the project?

6. How much time did the student spend on the project?

7. Is the student familiar with the scientific literature in the studied field?


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IV. Skill (Individual – 15, Team – 12)1. Does the student have the required laboratory, computation, observational and

design skills to obtain supporting data?

2. Where was the project done (i.e.: home, school, laboratory, universitylaboratory)? Did the student receive assistance from parents, teachers,scientists, or engineers?

3. Was the project carried out under adult supervision, or did the student worklargely alone?

4. Where did the equipment come from? Did the student build it independently?Was it obtained on loan? Was it part of a laboratory where the student worked?

V. Clarity (Individual – 10, Team – 10)1. How clearly can the student discuss the project and explain the project’s

purpose, procedure, and conclusions? Make allowances for nervousness. Watchout for memorized speeches that reflect little understanding of principles.

2. Does the written material reflect the student’s understanding of the research?(Take outside help into account.)

3. Are the important phases of the project presented in an orderly manner?

4. How clearly are the data presented?

5. How clearly are the results presented?

6. How well does the project display explain itself?

7. Is the presentation done in a forthright manner, without cute tricks or gadgets?

8. Did the student do all the exhibit work or did someone help?

VI. Teamwork (Team Projects only - 16)1. Are the tasks and contributions of each team member clearly outlined? How did

you delegate responsibilities between each of the team members?

2. Did you designate one person to be the team leader? If so, what were his/herresponsibilities? Do you feel that a team leader is a necessary component for ateam project? Why or why not?

3. Was each team member fully involved with the project, and is each memberfamiliar with all aspects? How did you approach other team members to makesure the work got done?


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4. Did you find it difficult finding the time to work together? What actions did youtake to assure that you met as often as necessary to complete the project?

5. Does the final work reflect the coordinated efforts of all team members?

Evaluation CriteriaIndividualProjects

TeamProjects

Creative Ability 30 points 25 points

Scientific Thought/Engineering Goals 30 points 25 points

Thoroughness 15 points 12 points

Skill 15 points 12 points

Clarity 10 points 10 points

Teamwork - - - - - 16 points

TOTAL POSSIBLE SCORE 100 points 100 points

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