Generating Electricity: Wind and Water

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A match made in energy heaven, wind and water are wonderful sources of clean, renewable energy. Let us see what goes into this electricity generation by making some wind and water turbines ourselves!

Big Ideas: 
  • Mechanical, kinetic energy from wind and water flow can be harnessed and converted into electrical energy.
  • Wind, though a great source of renewable energy, is not always consistent. Pairing this with hydro, which allows for energy storage (potential energy), makes it a more viable source of electricity.

Purpose

The purpose of this experiment is to develop and appreciation for the details involved in the generation of electricity using wind and water, as well as to explore some of the challenges faced by each energy source.

Introduction

We know much about the physics behind constructing these energy generation devices (read more on wind turbines here), but there are some challenges and advantages that are not immediately apparent.

The concept is simple: wind possesses kinetic energy in its movement. When wind passes through the blades of a turbine, this energy turns the blades and is converted into electrical energy, which can then be used to power our homes.

But what do we do when the wind isn't blowing? Energy must be continually supplied to households if we are to have power on demand. There is the possibility of storing the energy in batteries for later use, but this is costly, and making a battery can release more greenhouse gas than what is offset during its lifetime- defeating the purpose of using a clean energy source to begin with.

This is where water, or hydro, power comes into play. When energy production is low or demand is high, water is released into the hydro turbines to generate electricity. On the other hand, when demand is low or the wind is strong, the water gates are simply shut so that water can be saved for other times. There are even some power plants where the turbines are run backwards to refill the water reservoir of a hydro electric dam when there is excess energy to spare from other sources. The energy is stored as potential energy.

The images below illustrate how water can be used to both generate and store energy.1

Using this method, we can store energy in a clean and efficient way. Water turbines can be more than 90% mechanically efficient thanks to careful design of turbine blades, structure, and motor design. This means when we store and then re-release energy, we lose less than 20% of the energy put in through the process of pumping up the water and running the turbines again. While this is less than the near 100% charging efficiency of batteries, we can do this without emitting extra, unwanted carbon. With wind power able to harvest energy straight out of the air and hydro power capable of making up for the intermittency of wind power, we can see why this combination is called a match made in energy heaven.

In this set of experiments, students can generate their own wind or hydro electric power by constructing a wind/water blade attachment for the generator/ gearbox used in this Hand Crank activity. Using their wind/ water turbines, students are able to explore how mechanical energy from external sources can be harnessed and turned into electrical energy, as well as the effect of different gear ratios.

To try and illustrate how the two systems could be connected, i.e. how the energy generated from the wind turbine could be stored as water and used again for energy, the UBC Physics and Astronomy outreach team tested the wind turbine in conjunction with a water pump (KidWind Small Water Pump). Unfortunately, the efficiency and reversibility of this particular water pump were too low to provide a clear demonstration.

Materials

  • Hand crank generator/ gearbox (We purchased the Tamiya 3-Speed Crank-Axle Gearbox Kit
  • Cardstock or poster paper
  • Pencil, scissors
  • Fan to provide wind (industrial fan works best)
  • Digital multimeters to measure voltage, current

Teachers' Toolbox and Tips

  • Older students have the opportunity to design and build their own wind turbine blades. KidWind provides a ton of resources on wind and renewable energy, including an advanced blade design manual. Their wind turbine hubs can be used for this activity, drilled to fit the shaft of the Tamiya hand crank generator.

Steps

  1. Make sure the generator is set to the desired gear ratio:
  2. Gears are essentially wheels with teeth that lock together so that the turning of one gear will turn another. They have a wide variety of engineering applications, and in the case of our gearbox/generator, serve the purpose of changing the speed of rotation.

    A high gear ratio of 204:1 means that one turn of the axle, whether it be with the hand crank or via wind power, will turn the rotating part of the electric generator 204 times! This resulting rotation is what creates electricity. A lower gear ratio means the rotating part will turn fewer times with one turn of the axle, but it will take less force to turn the axle.

    If you test the different gear ratios on the hand crank generator, you can feel that it takes more effort to turn the high-geared generator! In fact, it takes so much force that it is not ideal for a wind turbine; instead, the medium (58:1) and low (17:1) gear ratios will work best.

  3. Make a pinwheel wind turbine attachment:
    1. Take a square sheet of semi-rigid paper (The UBC Physics and Astronomy team have tested sizes 8.5" x 8.5'' (from letter-sized cardstock) and 20'' x 20'' cut from poster paper).
    2. Fold the square along the diagonal, then unfold it back again. Repeat this along the other diagonal, so that the paper now looks like a square with an “X” made by the creases.
    3. Carefully poke a hole near each corner and at the centre, and cut along each crease until you reach 3-5 cm from the paper’s centre, as shown in the picture below.

    4. Pick up each of the holes and align them with the hole in the centre to create four blades (bend, do not fold), taping them down to create your pinwheel.
    5. What is left is to attach the pinwheel onto the hand crank generator/gearbox. If the generator is attached to a handle, first disassemble the handle as shown below:

    6. The two parts that make up the main body of the handle can be used to the hold the pinwheel in place. First attach one to the shaft securely, slide the hole of the pinwheel onto the shaft, then attach the second, "sandwiching" the pinwheel in place.
    7. Using the electric fan for wind, test out your new wind turbine! Can you measure the voltage and current generated? If both low and medium gear ratios were used, compare the two at the same wind power: what happens to the speed of blade rotation? What happens to the electricity generated (voltage, current, power)?
    8. Experiment to see how does direction/ angle of wind affects the rotation speed of your blades. What can you do to improve your blades (structural integrity, aerodynamics)? What happens when you have bigger blades?
  4. Make a water turbine attachment
  5. Create a similar attachment for a water turbine, e.g. a water paddle from waterproofed cardboard or plastic sheets. Use your imagination! Check out the Hydro-electric Dam Demo for inspiration.

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