H2OMG Sampler by NEED Project

H2oMG! Activities Inside: • Force of Water • Moving Water Can Do Work • Wave Energy Design Challenge

• Convection Currents • OTEC Model

Grade Levels:

Elem

Elementary

Intermediate

Secondary

Subject Areas: Science

Technology

Engineering

Math

Teacher Information &Background Hydropower has been used to generate electricity longer than any other renewable resource. The first utility hydropower generating station was installed in Appleton, Wisconsin, and began production in 1882. By the end of the 1880s, hydropower was being used in multiple locations, and was providing all the electric power in Niagara Falls, NY. Over the last 130 years, hydropower generation has been installed all over the United States and the globe. In the U.S., it is the leading renewable resource to produce electricity. While the recent focus for many has been on wind and solar energy, the many ways moving water can be used to generate electricity have remained in the sights of renewable energy researchers. Experts agree that maintaining electricity demand, reducing carbon emissions, and mitigating climate change cannot all occur without hydropower at current, or higher, generation levels. While traditional hydropower has been in use for the last 130 years, researchers are constantly looking for ways to improve conventional hydropower technology by increasing efficiency and reducing environmental impact. Beyond these technological advances, research is also being done on smaller-scale hydropower, such as incorporating modular systems in pre-existing sites like flood-control dams and lock systems operated by the Army Corps of Engineers. An emergent advancement includes deploying microhydro systems that can power a single home using a small spring, or even the moving water in a public water line. This unit will also explore conventional hydropower and also cover marine hydrokinetic energy generation as a way to introduce another future application for harnessing energy from the oceans. The activities in this sampler are designed to introduce your students to hydropower and get them interested in this renewable resource. Activities for each grade level are provided, and many can be completed in one or two class periods. Force of Water is an activity that shows students how the pressure of water can change by altering one variable. Moving Water Can Do Work allows students to directly harness the power in moving water to lift a load. Convection Currents shows students how convection currents form in water and includes a discussion about how those currents drive ocean currents. Two new activities introduced in this sampler are OTEC Model and Wave Energy Design Challenge. The OTEC demonstration shows students how ocean thermal energy conversion works. The wave energy activity challenges students to design a device that taps into the power carried by ocean waves. Complete hydropower curriculum guides are available for free download at https://shop.need.org/collections/hydropower. Guides are available in four levels and include a student guide as well as a teacher guide with additional resources and extensions.

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MATERIALS ACTIVITY

MATERIALS NEEDED

Force of Water Investigations

2-Liter soda bottles (straight sided) Rulers Push pins Duct tape Towels or paper towels

Permanent markers Wallpaper pans or shallow trays Water Buckets (optional) Funnel (optional)

Moving Water Can Do Work

Fast-drying glue Foam craft balls Cups or containers* Heavy duty thread Large paper clips Round-barreled pencils

Ruler Scissors Tape Water Wooden ice cream spoons

Wave Energy Design Challenge

Alligator clips Assorted fasteners (nails, screws, nuts, bolts) Digital multimeters Paper towels or towels Plastic building toy parts (gears, levers, long, thin pieces, etc.) as desired

Rocks or weights for anchoring Small DC motors Waterproof glue Waterproof or water-resistant materials (corrugated plastic, thin plastic sheeting, etc.)

Convection Currents

Boiling water 9oz Clear plastic cups Corrugated cardboard Food coloring (dark color)

Ice water Marbles (using 2 different colors is helpful) Room temperature or tap water in a pitcher Tongs

OTEC Model

Baking sheet or cafeteria tray Heat lamp Ice Low, wide, clear container (9x13 baking dish or clear plastic box) Plastic tubing

Rocks of various sizes Sand Thermometers Plastic wrap Small model of a building

*The cups or containers used need to be tall and wide enough to house the foam ball with wooden spoon blades. It may be necessary to test this ahead of time to ensure the activity will work. The easiest solution is to trim the wooden blades, but students may have other suggestions. Don’t be afread to let them explore.

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Force of water Investigations Original versions of this activity can be found within the following NEED titles at shop.NEED.org: Wonders of Water Energy of Moving Water

Grade Levels Elementary, grades 3-5 Intermediate, grades 6-8 Secondary, grades 9-12

 Time

Background For flowing water to be useful to generate electricity, it needs to have sufficient kinetic energy to transfer to a turbine. The kinetic energy of moving water is equal to one-half its mass multiplied by its velocity squared (KE=½mv2). Turbines take the linear motion of flowing water and transform it to rotational motion, which is used to turn a generator for electricity. If the water is flowing too slowly, the turbine will not have sufficient energy to turn the generator fast enough to generate the power needed. Two ways to modify the velocity of water flowing through a dam are to increase the volume of water flowing through an outlet, or to increase the height of the water behind the dam. This activity helps students understand both methods using simple materials.

Objective Students will be able to identify variables that affect the force of flowing water at a dam.

1-2 class periods

Materials AT EACH CENTER 1 2–Liter soda bottle* 1 Ruler 1 Push pin 1 Wallpaper pan Towel or paper towels

Permanent marker Water supply Duct tape Buckets (optional) Funnel (optional)

*NOTE: Make sure the bottles have flat surfaces without curves or decorative molded features. One-liter bottles can also be an acceptable substitute.

Preparation Gather all materials for the activity. You will need one 2-liter soda bottle for each group in every class. Each exploration should take 10–15 minutes to complete. If the students cannot complete all of the explorations in one class period, set up a schedule for the students.

Classroom Management Tips It will save water if containers or buckets are made available to students to pour their water into between trials (when instructions say to empty the bottle). Ask students to help supply your stock of 2-liter bottles by visiting their recycling bins. It may be helpful to offer a reward.

Procedure 1. Divide the students into six groups and assign them to centers. 2. Review the procedures for the Force of Water explorations with the students. Introduce any vocabulary necessary for describing a damn, such as penstock, gate, or turbine. Answer any questions and explain the schedule for completing the explorations. 3. Instruct the students to formulate hypotheses to answer the questions in the explorations, using the handout or science notebooks. 4. Instruct the groups to complete the explorations according to your schedule. 5. Instruct the groups to answer the conclusion questions. Review and discuss observations and conclusions as a class.

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Effect of Volume on the Force of Water Question What effect does the volume of water have on the force of the water?

Materials 1 2-Liter soda bottle 1 Ruler 1 Push pin 1 Wallpaper pan Towel or paper towels Permanent marker Water supply Duct tape

Preparation Use the ruler to measure from the bottom of the bottle to 5 cm. Mark this spot with a dot, and also mark a line horizontally across the bottle at this height. Continue marking straight up every 5 cm, and horizontally at each mark until you reach 20 cm.

20 cm

Use the push pin to make a hole at the 5 cm mark only. Put a piece of duct tape over the hole. Read the procedure. Record your hypothesis on the next page, or in your science notebook before completing your investigations. Decide if you will need to remove the cap, loosen the cap, or keep the cap in place.

15 cm

Procedure 1. Fill the bottle with water to the 20 cm mark. 2. Place the bottle in the wallpaper pan with the hole pointing into the pan. Place the ruler at the base of the bottle and make marks on the bottom of the pan at each 2 cm increment until you reach the end of the pan. 3. Remove the duct tape and immediately measure the distance the water projects out from the hole. Cover the hole with your finger.

10 cm

4. Record the distance in your table. 5. Repeat steps 1-4 two more times for a total of three trials. 6. Repeat steps 1-4 three times filling the bottle to 15 cm. Record your data with each trial. 7. Repeat steps 1-4 three times filling the bottle to 10 cm. Record your data with each trial.

5 cm

8. Repeat steps 1-4 three times filling the bottle to 5 cm. Record your data with each trial.

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Effect of Volume on the Force of Water Question What effect does the volume of water have on the force of the water?

Hypothesis

Observations and Data Record your data in the table below.

VOLUME

TRIAL 1

TRIAL 2

TRIAL 3

AVERAGE

Conclusion Was your hypothesis correct? Why or why not? What is the effect of the volume of water on the water’s force? Use data to support your answer.

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Effect of Penstock Height on the Force of Water Question What is the relationship between the penstock height and the force of water?

Materials 1 2-Liter soda bottle from previous investigation 1 Ruler 1 Push pin 1 Wallpaper pan Towel or paper towels Water supply Duct tape

Preparation Make sure the outside of the bottle is dry. Using the push pin, make holes at the 10 cm, 15 cm, and 20 cm marks. Cover each hole with a piece of duct tape. Read the procedure. Write your hypothesis on the next page or in your science notebook before completing your investigation.

20 cm

Decide if you will need to remove the cap, loosen the cap, or keep the cap in place.

Procedure 1. Fill the bottle with water to the 20 cm line. 2. Place the bottle at one end of the wallpaper pan with the holes pointing into the pan.

15 cm

3. Remove the duct tape from the 5 cm hole and immediately measure the distance the water projects from the hole. Record the results on your data table. 4. Cover the hole with your finger, refill the bottle with water to the 20 cm line and place back in the pan. Uncover the hole and measure the distance the water projects again. Record your results. Repeat once more for a total of three trials.

10 cm

5. Dry the outside of the bottle. Tape the hole closed. 6. Follow steps 1-5 again for the 10 cm, 15 cm, and 20 cm holes.

5 cm

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Effect of Penstock height on the Force of Water Question What is the relationship between the penstock height and the force of water?

Hypothesis

Observations and Data Record your data in the table below.

Penstock Height

Trial 1

Trial 2

Trial 3

Average

Conclusion Was your hypothesis correct? Why or why not? What is the relationship between penstock height and the force of water? Use data to support your answer.

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Moving water can do work Objective

This activity can be found within the following titles at shop.NEED.org:

Students will be able to describe how a hydropower plant does work to create electricity.

Wonders of Water

Materials AT EACH CENTER

Water and Energy

1 30–cm Piece of heavy duty thread 1 Foam craft ball 1 Round–barreled pencil 2 Tall cups or containers

Wooden spoons Fast–drying glue Large paper clips Ruler Scissors

Water Tape

Grade Levels Elementary, grades 3-5 Intermediate, grades 6-8 Secondary, grades 9-12

Preparation

 Time

Gather the necessary materials from the list above. It may be preferable to have the students cut or snap the wooden spoons in half. This may also be necessary to make sure the spoon blades will fit inside the cup when assembled. Glue these blades to the foam balls far enough in advance of the first investigation to allow for drying time. Hot glue, if available and safe for students, will dry quickly and cut down on time needed for construction and experimentation. Adult or older student helpers can be helpful with this process, depending on the abilities of your students.

30-45 minutes

Procedure 1. Review the Moving Water Can Do Work procedures. Students may use the worksheet or their science notebooks to write a hypothesis and record data and conclusions. 2. Instruct the groups to go to their centers and complete the investigations, recording their data and observations. 3. Have the students complete the conclusion section with their groups. 4. Review the results and conclusions with the class.

Extensions Students can experiment with differing numbers of blades or redesign their system to do more work. If time allows, students can continue the testing and redesign process. As an engineering challenge, provide different materials and no written instructions other than the prompt - “build a water wheel that lifts paper clips.”

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Moving water can do work Question How can water do work?

Materials

1 Round-barrel pencil, sharpened 2 Foam cups 30 cm Thread 1 Foam craft ball 4 Blades (or more) Scissors

Glue Tape Water Paper clips Ruler

Procedure, Part 1 1. Make a hole through the middle of the foam ball with the pencil as shown in Diagram 1. Slide the foam ball to the middle of the pencil. Place rings of glue on either side to secure the ball to the pencil. 2. Insert four blades into the foam ball at equal distances from each other, as shown in Diagram 2. Make sure that the blades are not too long to fit into the cup. Glue the blades into place and let dry. 3. Cut two small, V-shaped grooves on opposite sides of the top of the cup as shown in Diagram 3. 4. Tie one end of a piece of thread to a paper clip. Tape the other end of the thread to the pencil as shown in Diagram 4. 5. Place the pencil into the grooves on the cup so the foam ball is in the center of the cup. Adjust and re-glue the blades so that they do not hit the edge of the cup. 6. When the glue on the blades is dry, place the water wheel system at the edge of a table so the one paper clip hangs off the table. 7. Get a second cup and fill it nearly full with water. Pour the water slowly and evenly onto the blades, as shown in Diagram 5 on the next page. What happens? Record your observations.

Observations ________________________________________________________________________________________ ________________________________________________________________________________________ CONTINUED ON THE NEXT PAGE

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Moving water can do work Question How many paper clips can your water wheel lift?

Hypothesis Read the procedure. Write a hypothesis to answer the question. If _______________________________________________________________________________________________________________ then_____________________________________________________________________________________________________________ because _________________________________________________________________________________________________________

Procedure, Part 2 1. Place four additional paper clips on the end of the string so there are a total of five paper clips. 2. Fill the second cup nearly full with water. Pour the water slowly and evenly onto the blades, as shown in Diagram 5. 3. Measure the distance the paper clips were lifted. Record the data in the table. 4. Pour the water you caught back into the pouring cup. Repeat the test two more times. Record the results and calculate the average distance. 5. Add five more paper clips to the end of the thread and repeat steps 2-4. 6. Continue testing your water wheel, adding five paper clips at a time until you cannot lift any more paper clips.

Data and Observations PAPER CLIPS

DISTANCE 1

DISTANCE 2

DISTANCE 3

AVERAGE DISTANCE

5 10 15 20 25

Conclusion Explain what happened as more paper clips were added to the string.

What would happen if you added extra blades? Test it out if youâ&#x20AC;&#x2122;re able.

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Wave energy design challenge Grade Levels Intermediate, grades 6-8 Secondary, grades 9-12

 Time Several class periods, and possible time outside of class as homework

Background Because of the size of the oceans and the wide availability of wave energy, many research projects have been focused upon ways to harness the energy of ocean waves to generate electricity. However, the U.S. has no systems currently generating wave power outside of the research testing phases. This activity challenges students to develop a way to generate electricity using waves in a controlled environment. In order for students to develop and test their designs, a reliable source of wave energy is necessary. You may have a wave tank in your school or an alternative way to make waves for your students. However, if you do not, we have developed a device you can build and use to generate consistent water waves for your students. The materials and assembly instructions can be found at: shop.NEED.org.

Objectives Students will be able to explain how their devices use wave energy to generate electricity. Students will be able to identify the parts of a generator and explain how they work. Students will be able to explain how wave energy can be used to generate electricity.

Materials Alligator clips Assorted fasteners (nails, screws, nuts, bolts) Digital multimeters Paper towels or towels Plastic building toy parts (gears, levers, long, thin pieces, etc.) as desired Rocks or other weights as needed for anchoring Small DC motors Waterproof glue Waterproof or water-resistant materials (corrugated plastic, thin plastic sheeting, etc.)

Preparation Build a wave maker following our instructions (link above) or your own design, or secure use of a wave tank for classroom use. If working in an environment where CTE classes are taught, engage CTE students on the design and construction of the wave maker. Decide on the design parameters and goals for student designs and whether you will have students work individually or in small groups. If group work is desired, decide if you will assign groups or allow students to choose their own group members. Preview online video resources of proposed and working wave generation technology (see next page), and generate a play list to show students. Gather materials for students to use; include multiples of each tool students might need.

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Procedure 1. Introduce wave energy to students. Explain to them that waves are generated by wind, currents, and tidal flow, and are considered one of the largest untapped energy sources on Earth. Explain that they will be challenged to design or create a model for generating wave energy. 2. Project the Parts of a Generator master. Explain each part and define them. Describe how the generator works. For additional background, refer to NEED’s Secondary Energy Infobook. 3. Itemize and discuss the minimal requirements for student designs and models you have predetermined. Display the requirements for students to renew. Showcase any materials you are providing. 4. Show students the video or other resources you have selected for their use. Ask them what each of the experimental designs has in common and how those designs could be scaled down and modified for classroom demonstration. 5. Explain any guidelines for group work and brainstorming. 6. Allow students some time to collaborate and discuss possible design ideas. Provide a deadline for design completion. Explain that they will design first. Any construction and testing will occur on Design Challenge Day(s). 7. Allow students collaboration or work time in class as appropriate. If the designs are to be completed entirely outside of class, allow a few minutes periodically for group members to work together, and plan for work on their design activities. 8. Discuss any expectations for Design Challenge Day(s). Decide on the number of attempts you will allow and any other requirements you have of students. 9. On Design Challenge Day, allow students as many attempts at generating electricity as you previously discussed. It will be helpful to have paper towels or towels to clean up water that might spill.

Additional Resources Bureau of Ocean Energy Management https://www.boem.gov/renewable-energy/renewable-energy-program-overview Department of Energy Office of Energy Efficiency and Renewable Energy https://www.energy.gov/eere/water/downloads/mapping-and-assessment-united-states-ocean-wave-energy-resource Electric Power Research Institute, Mapping and Assessment of the United States Ocean Wave Energy Resource (pdf) https://www.osti.gov/servlets/purl/1060943 Energy Information Administration Wave Energy Explained https://www.eia.gov/energyexplained/hydropower/wave-power.php National Renewable Energy Laboratory https://www.nrel.gov/water/ Pacific Marine Energy Center https://www.pmec.us/ University of Edinburgh https://www.ed.ac.uk/news/2019/device-could-deliver-wave-energy-to-thousands University of Hawaii Energy Institute https://www.soest.hawaii.edu/soestwp/

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parts of a generator Turbine Generator TURBINE TURBINE SPINS SHAFT

MAGNET

Spinning Coil of Wire

North Pole

South Pole DIRECTION OF ELECTRIC CURRENT TO TRANSMISSION LINES

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Convection Currents Background Ocean currents are driven by convection currents in the ocean and atmosphere. Water is heated in the tropics because the sun is more directly overhead. The warm water spreads out over the colder, deeper water. As the Earth rotates, the air in the atmosphere has the tendency to lag just a bit because of its inertia. This is known as the Coriolis effect. As a result, wind pushes on the warm water on the ocean’s surface and the water gets pushed along in a rotation. Cool water moves in to take its place. Scientists at Pacific Northwest National Laboratories are exploring ways that ocean currents can be used to generate electricity. This activity demonstrates convection currents in a controlled classroom setting.

Objectives

This activity is adapted from NEED’s EnergyWorks unit, and is part of Heat Module Three. Download EnergyWorks at shop.NEED.org.

Grade Levels Elementary, grades 3-5 Intermediate, grades 6-8

 Time 1-2 class periods

Students will be able to explain how convection currents form. Students will be able to predict the direction in which convection currents flow given temperatures of water at various points in the model.

Materials PER STUDENT STATION 2 9 oz Clear plastic cups 8 Marbles, 4 each of 2 colors Corrugated cardboard strip (see Preparation below) Dark-colored food coloring

Materials FOR THE CLASS Boiling water (electric kettles work well) Tongs Ice water Room temperature water

Preparation Cut corrugated cardboard strips at a length equal to the diameter of the bottom of the cups, and a width equal to the diameter of the marbles. Prepare a copy of the Ocean Currents Master for projection. On the day of the activity, prepare an ice water bath and place all of one color marbles inside. Prepare a near-boiling water bath and place all of the other color marbles inside. Allow enough time for marbles to heat or cool accordingly.

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Procedure 1. Introduce the activity to students and explain the instructions. 2. Distribute cups and cardboard strips to students and explain you will provide the hot and cold marbles. Make sure students know which color marbles have been in the ice water so they can keep track. 3. Have each student group fill one cup about 3/4 full with room temperature water from a pitcher or tap. 4. At each student station, remove 4 marbles from ice water and place them in the bottom of the empty cup. 5. The cardboard strip will act like a partition between hot and cold marbles. While students hold the cardboard strip in place across the middle of the bottom of the cup, place 4 marbles from hot water opposite the ice water marbles. The cardboard strip should remain on edge, keeping the hot and cold marbles separate from each other. 6. Instruct students to stack their cups of water inside the cups with marbles and cardboard strip. 7. Each student group should add a drop of food coloring to the side of the cup with the hot marbles. It will probably sink down to the bottom of the cup, leaving a trail of color behind it. 8. Have students look through the side of the cup and observe the swirling pattern of the food coloring in the cup. It should swirl up on the “hot” side of the cup and might continue traveling down on the “cold” side. 9. Direct students to sketch what they see in their science notebooks. 10. Explain to students that convection currents like those they observed occur becasue as a fluid gets warm, it becomes less dense and moves up above the more dense, cooler water. 11. Shift the discussion toward the Coriolis Effect and how it drives ocean currents. Show students the Ocean Currents Master. 12. If you have time, challenge students to develop the model further to fully reflect how ocean currents form. If you have time and resources available, have students construct and test their modified model.

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Ocean currents master

Global Ocean Currents

Warm water current

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Convection currents Question How does heat affect ocean water movement?

Hypothesis

Materials 2 clear plastic cups 8 marbles – 4 of one color from a hot water bath and 4 of another color from an ice water bath Room temperature water or water straight from the tap Food coloring Cardboard strip

Procedure 1. Fill one cup about three-quarters full with tap water or water from the pitcher your teacher provides. 2. After your teacher gives you the marbles from the ice water bath, place the cardboard strip against them, on its edge, as shown in the picture. Your teacher will place the marbles from the hot water bath on the other side of the cardboard strip. 3. Set the cup of water on top of the marbles and let it sit there while your group counts to 10. 4. Carefully drop one drop of food coloring into the cup of water near the side with the hot marbles. 5. Watch the food coloring to see how it is mixed and swirled in the water.

Cold marbles

Hot marbles

6. When you have finished, return your materials as directed by your teacher. Wipe up any water or food coloring at your station.

Cardboard strip

Observations In your science notebook, make a diagram that shows, with arrows, how the food coloring moved in the water.

Conclusion Answer the following in a science notebook: 1. Look at your diagram. What does your investigation show you about how warm water moves? 2. Where in the oceans might you expect to see this kind of movement? Near what kinds of features? 3. What would happen if wind started to blow on the top of one part of your cup of water? Make a diagram showing how the water might move. 4. If you have time in class, describe how your investigation could be changed to more closely show how ocean currents move.

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otec model Grade Levels

Background In the tropics, significant differences in water temperature exist. The surface water may be as warm as 25° C, while deep ocean temperatures near 4° C. This temperature difference is used in a technology called Ocean Thermal Energy Conversion (OTEC). This technology uses a low-boilingpoint substance, such as anhydrous ammonia, to drive a turbine similarly to the way steamdriven turbines operate in common thermal power plants. The warm ocean water is used to boil the ammonia with a heat exchanger. The ammonia gas is fed under pressure through a turbine attached to a generator, and electricity is generated. The cold water from the deep ocean is used to condense the ammonia back into a liquid, and the process repeats. OTEC is feasible where the deep ocean is near to the shore, such as off the Hawaiian islands.

Elementary, grades 3-5 Intermediate, grades 6-8 Secondary, grades 9-12

 Time Preparation time - 2 hours Instruction time - one class period

Objectives Students will be able to explain how OTEC works by describing the process it uses to generate electricity. Students will be able to identify the parts of a generator and explain how each part works.

Materials Baking sheet or cafeteria tray Heat lamp Ice Low, wide, clear container (plastic shoe box or 9x13 baking dish) Plastic wrap

Plastic tubing Rocks of various sizes Sand Small model of a building Thermometers

Preparation Gather all materials and assemble the model (without the ice or heat lamp) before class. Prepare a copy of Parts of a Generator (page 14) to project. The day before discussion in class, freeze water in the baking sheet or cafeteria tray.

Procedure 1. To assemble the model, lay a pile of rocks of various sizes in one end of the clear container. Pile them so they slope down from the end of the container toward the bottom, ending about one-third to one-half the distance between ends. Carefully add sand to cover the rocks. The purpose of the rocks is to prevent the sand from sliding down to the bottom of the container. The rocks and sand represent the land where OTEC is being used. 2. Cut a piece of clear plastic wrap and line the rest of the container, on top of the sand. This will keep the water from infiltrating the sand and rocks and creating a sloppy mess.

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3. Lay a piece of tubing down so it stretches from the bottom of the container at the far end, up the sand, and into the model building. Lay another piece of tubing so it extends from the other side of the building and down the sand, just barely below where the water level will be. Lay a third piece of tubing to exit the building in the middle and extend to the middle region of the water. 4. On class discussion day, set the tray with ice on the table and place the OTEC model container on top of it. Carefully pour water into the container, avoiding disturbing or dislodging the tubing. Position the heat lamp over the model so it shines down on the model from directly overhead. 5. Place one thermometer near the bottom of the “ocean” and another near the surface. 6. Explain to students that the ice represents the very cold water found at the bottom of the ocean, where the temperature can be as cold as 4°C, and the heat lamp represents the sun. Show students the model building, and that it represents the OTEC power plant. 7. After the heat lamp has been on for a few minutes, read the temperature of the water at the surface as well as in the deeper parts of the “ocean.” Tell students that OTEC is designed to take advantage of this temperature difference. 8. Describe the process to students: a. Warm water from the surface of the ocean is pumped into the power plant. A heat exchanger boils a low-boiling-point substance from liquid to gas. Most OTEC power generating sites are using anhydrous ammonia, which boils at -33°C. b. The pressurized gaseous ammonia is used to turn a turbine, which is attached to a generator. The rotational motion of the turbine is transformed into electricity in the generator. c. The pressurized ammonia gas is cooled and condensed by the very cold ocean water, which is pumped in from the deep parts of the ocean. The ammonia is then recycled to continue the process. d. The warm surface water and cold deep ocean water are combined and expelled into the ocean by a third pipe. 9. Allow students time to sketch the model in their notebooks and include a description. 10. Ask students which geographical regions are most suited for OTEC technology, and which areas would not be good candidates for this generation method.

Additional Resources An Evaluation of the U.S. Department of Energy’s Marine and Hydrokinetic Resource Assessments (2013) Chapter 5 Ocean Thermal Energy Conversion Resource Assessment (available from National Academic Press) https://www.nap.edu/read/18278/ chapter/7 Energy Information Administration – OTEC Explained https://www.eia.gov/energyexplained/hydropower/ocean-thermal-energy-conversion.php Makai Ocean Engineering (OTEC company in Hawaii) https://www.makai.com/ocean-thermal-energy- conversion/ NOAA Office for Coastal Management https://coast.noaa.gov/czm/thermalenergy/

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