Harvesting wind
Learning Intention:
To understand the workings of wind turbines. To understand that testing and recording information is important in an experiment.
How do wind turbines work? Thanks to NOVA PBS for the video
Discussion:
What do you wonder about the workings of a wind turbine?
A wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, a wind turbine uses wind to make electricity.
How does a wind turbine create electricity?
The wind turns two or three propeller-like blades around a rotor. The rotor is connected to the main shaft, which spins a generator to create electricity. The electricity is sent down thick cables that run down the tower to the ground.
What are some of the benefits of wind turbines? Can you think of any negatives? Do you think the positives outweigh the negatives?
Wind energy is clean energy. It doesn't pollute the air and wind turbines don't produce green house gases. When a lot of turbines are built in one place it is called a wind farm. Wind farms can be on land or at sea.
Have you ever seen a wind farm? Where was it? why do you think it was built there?
Operating a wind farm is not as simple as building a wind turbine in a windy place. There is careful planning and research done to fin out how fast and how often the wind blows on a site and how consistent the wind is.
Where would be a god site around our community? Why?
Both wind turbines and sails on a boat adjust their angle and direction to capture the wind as they move. The blades of a wind turbine work using the same principles of lift and drag as an aeroplane wing, a sail or foils on the America's Cup boats.
Why are wind turbines so tall?
Turbines can be as tall as a 20-story building and they have three 60 metre-long blades. That is longer than the width of a rugby field. A pinwheel works in a similar way to a wind turbine
Activity: Make a Pinwheel to model a wind turbine and test it
Materials:
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Pencil with a rubber top
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Ruler
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Thin card or paper
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Drawing pin
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Scissors
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Pen or pencil
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Felt pens for colouring
Procedure:
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Cut a piece of card/paper 16cm x 16cm square
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Draw a diagonal line across the paper from one corner to the opposite corner.
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Mark the middle of the square and make a small hole. You can use a pencil or the pin.
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Measure 3cm from the hole along each of the diagonal lines and make a mark.
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Cut along each of the diagonal lines from the outside corners to the mark.
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Using a pencil or pin make a hole in the top left corner of each of the four triangle flaps (see diagram).
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Pick up each flap and curl it to the hole in the middle of the square. Thread the pin through the holes, so the head of the pin is on top of the folded flaps.
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Thread the pin through the middle hole.
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Push the pin into the rubber on top of the pencil, being careful not to push the pin too far through the rubber. You don’t want it to stick out the other side.
Testing:
Engineers test everything they build to see how well it works. Make some predictions.
What things will affect how well the turbine/pinwheel works?
Where is the wind the strongest?
Low to the ground or high up?
What will make your pinwheel go faster?
What direction should you point the pinwheel?
Away from the wind, into the wind, at an angle to the wind?
Test all of these factors and record your findings.
Back in the classroom.
What happened?
Were your predictions correct?
Would you change anything on your wind turbine if you built it again? Can you think of anything that would improve the design of your turbine?
Extra:
Explore by varying the sizes of paper you use. Make using a circular piece of card with multiple blades. Test to see the difference.
Glossary:
Wind energy, pungao hau - Electrical energy sourced from harnessing the wind with windmills or wind turbines.
Renewable energy - Energy from something that is not depleted when it is used, like wind or solar power.
Windmill, purere kapo hau - A structure that converts wind power to pump water or mill grain.
Wind turbine, Kopohau - Tall towers with blades that turn in the wind to generate electricity.
Wind farm - A large group of wind turbines for electricity supply.
Lift (in sailing) - An upward force on an aircraft wing or aerofoil. Lift is the result of pressure differences between the top and bottom of an aerofoil.
Drag - The resistance to the movement of a boat through water.
Kinetic energy - The energy of anything moving such as a boat moving or a ball when kicked.
Friction - Is the resistance of motion when an object rubs against another object.
Axle - A rod passing through the centre of a wheel.