Wave Wattage Archive pick
April 8, 2002
Of Wind and Wave
 A high-tech economy is one that demands a lot of electricity. The U.S. Department of Energy estimates that over the next 20 years, America will need between 1,300 and 1,900 new power plants to meet its growing energy needs. The government and various private companies hope that the wind and waves — clean, renewable energy sources — will be part of the solution.

The 2002 Global Windpower Conference took place in Paris, France last week. Participants celebrated the fact that 2001 was the biggest year ever for wind power worldwide — and that wind power is the world's fastest growing form of energy. A growth spurt is certainly evident in the United States: last year, the wind-power generating capacity grew by 60%. Even so, wind power supplies less than 1% of the country's energy needs.

Wind farms are not proving the most popular alternative energy choice because they're huge, noisy, and, in congested regions, they take up valuable land. As Europeans know, the answer lies in taking the turbines offshore, where these factors are less important — and where the wind is stronger and more persistent. The United States' first offshore wind farm is expected to meet the energy needs of residents of Cape Cod, Massachusetts. Slated for completion in 2005, the 420-megawatt project will be the world's second largest wind farm. (In first place is a wind farm being developed off the coast of Ireland, which will supply the electricity needs of 500,000 homes and replace some €330 million of imported fossil fuels per year.)

Below the wind turbines, the crashing waves also hold boundless energy just waiting to be harnessed. The World Energy Council says that the oceans can supply more than two times the energy the world currently consumes but, so far, this vast resource has remained largely untapped. The world's first commercial wave power station began operation in November of 2000: the small Scottish island of Islay, with a coastline that's relentlessly pounded by the Atlantic Ocean, was the chosen site. The station now feeds 500 kilowatts of electricity into Islay's power grid, enough to light 400 homes.

Wave energy is being used by countries that have a lot of coastline, such as Great Britain and Australia. The United States does not have any wave energy facilities, but they could help serve power-hungry coastal states like California (see sidebar).

Wind and wave power are growing industries, and they offer a relevant context for you to discuss various science and math concepts with your students.

Powering California
California's power crisis two years ago was caused by a number of factors: a shortage of electrical generation inside the state, reduced electricity available to import from other states, and growth in electricity demand by industry and consumers. Some Bay Area scientists have proposed that wave power could help meet the needs of this densely populated state, because each mile of the its coastline could produce enough electricity to power around 50,000 homes.

Scientists at Sea Power & Associates in Berkeley have designed a wave-energy system called "Wave Rider." Here's how it works. Lightweight concrete floats moored one to two miles off shore are connected to hydraulic pumps. As the floats go up and down, riding the waves, the pumps turn turbines and generate electricity.

Read a profile of Sea Power & Associates from The Daily Californian.

Learn About the Problem
 Science & wave power: The power generator on Islay has two basic components: a wave energy collector and a generator to turn the energy into electricity.

The energy collector is built along the shoreline. The collector has an inlet facing out toward the ocean that allows ocean waves to enter and exit a main chamber. As a wave flows into the chamber, the rising water level inside the chamber compresses the air in the top of the chamber. The air is forced up through an enclosed column and past a turbine. The air spins the turbine like a pinwheel.

As the wave leaves the chamber, air is sucked back down through the column. The turbine is designed to turn the same direction no matter which way the air flows. The flux and ebb of the waves keeps the turbine moving. The spinning turbine spins the electrical generator, which converts the energy into electricity. (The following SimLibrary activities require Logal Express. Get a free trial subscription.)

  1. When a wave enters the chamber, it reduces the volume of the air in the chamber, thereby compressing the air. Students can explore the relationship of gas volume and pressure in the Middle School Gateways activity, Boyle's Law.

  2. Students can learn about the concepts of electrical power, the differences between power and energy, the differences between watts and kilowatt-hours, and the cost of running various electrical appliances in the Middle School Gateways activity, Electric Power.

  3. Students who have spent time at a beach know that waves can move with a lot of force. They can learn how waves transfer energy in the Physics Explorer activity, Energy in the String.

Math & wind power: Students can use Destination Math to review basic skills and then solve the problems in the Think About the Problem section below. (To use Destination Math, you'll need a subscription. Get a free trial subscription.)

  1. Dividing Decimals
    There are plenty of interesting problems to solve relating to the various facts and figures about the Cape Wind Associates' planned wind farm. To prepare, have students review Mastering Skills & Concepts IV: Dividing Decimals: Dividing Decimals by Whole Numbers.

  2. Parallel and Perpendicular Lines
    Many wind turbines have four blades. This Destination Math tutorial begins by noting that the blades on a turbine are perpendicular, like the X- and Y-axis. Have students review Mastering Algebra 1, Course 1: Graphic Solutions of Linear Systems: Graphing Parallel and Perpendicular Lines.

Think About the Problem
 Science & wave power: This is an excellent opportunity to look at types of energy, the useful and effective transfer of energy, and renewable versus non-renewable energy sources. Ask students to do the following:

  • Starting with the Sun — the original source of wind and wave energy — have students follow the transfer of energy across space to Earth, to the creation of wind and waves, to where the energy is captured and converted into electricity at a wind farm or wave-power plant, and finally to their own electrical outlets. Give them as many or as few steaps along the way as you feel necessary.

  • Based on the above, do your students feel that wind energy is a renewable or non-renewable energy source? Is wave energy renewable or non-renewable? Are all sources of electrical energy renewable? Why or why not?

  • Examine the diagram below, which shows a cutaway view of a fixed wave power generator like the one on Islay. Have them identify where in the diagram each of the following energy types occurs:

    • wave energy
    • mechanical energy
    • pneumatic energy
    • electrical energy

Math & wind power: Here are some problems for your students to solve:

For the Birds?
Wind power is "green" because it has little negative impact on the environment. But like any means of generating electricity, wind energy is not without its flaws: many birds have been killed after colliding with the massive turbines. Environmentalists say that wind farm sites — both on land and offshore — must be carefully selected, avoiding birds' migratory routes and nesting areas. The design of the turbines has been altered to reduce the risk to birds. Newer machines have larger, slower-moving blades that turn at 20-30 revolutions per minute (older machines had smaller blades that turned more quickly, likely making them harder for birds to see).

Students can read Dick Curry and Paul Kerlinger's investigation into the impact wind farms have on bird populations. These environmentalists found that bird fatalities from impacts with glass windows and encounters with domestic cats and automobiles outnumber deaths caused by wind turbines.

Environmental groups have criticized many other renewable energy sources too, faulting solar power for the overdevelopment of deserts and hydropower for damage to river habitats.

  1. Dividing Decimals
    The Cape Wind Associates wind farm will have 170 wind turbines laid out in a grid pattern over 25 square miles of saltwater. How many turbines will there be per square mile? How might the turbines be distributed? Students can draw a diagram to show how they would lay out the turbines.

    When the wind farm is operating at maximum capacity, it is expected to produce 420 megawatts of electricity. How many megawatts per square mile is this?

    On a hot day, New England's peak demand can be as much as 25,000 megawatts of electricity. Suppose all of New England's energy needs were to be supplied by a wind farm. How large would the farm need to be to supply 25,000 megawatts of electricity? Give your answer in square miles. How many turbines would this wind farm contain (assuming that it were laid out in the same way as the Cape Wind farm)?

  2. Parallel and Perpendicular Lines
    The rotors on the Cape Wind turbines have only three blades. Have students represent the three-blade rotor on a graph, with a line representing each blade. What conclusions can students come to about the relationship between the lines? Are they parallel, perpendicular, or neither? What is the relationship between the lines' slopes?

    Ask students to "turn the rotor" (i.e., rotate the lines around their point of intersection), and figure out what the slope of each line is. Is the relationship between the lines' slopes constant, as it is for perpendicular lines? Is it independent of or dependent on the lines' orientation?

Extending the Problem
  1. There are many different types of electrical power stations. Wave energy is intended to decrease use of older, traditional power stations, such as those that burn oil, gas, or coal, or nuclear power plants. These types of power stations are costly to run and pollute the environment. But even hydroelectric power plants have been criticized by some as being harmful to the environment. You'll find more information at these Web sites:

  2. Students can learn about a variety of renewable energy sources at the following sites:

  3. Ocean waves have other ways in which they transmit energy. Tsunamis, for example, transfer energy from coastal or underwater landslides, volcanic eruptions, or earthquakes:

  4. Ocean currents transfer thermal energy across and within Earth's oceans:

  5. To look at another form of green energy with your students, try the recent Teaching the News article, "Cow Power." It focuses on using cow manure to generate electricity (and also how cow burps are contributing to global warming).