What’s Good and What’s Bad about Wave and Tidal Energy? Wave and Tidal energy, sometimes called ocean or marine energy, are forms of water power in addition to methods previously discussed in a previous article about hydropower: http://www. kidsdiscover. com/teacherresources/whats-goodand-whats-bad-about-hydropower/ However unlike hydroelectric dams, which harvest power by installing an artificial obstruction in a flowing waterway, wave and tidal energy devices simply use the power of the ocean waves and/or rising and falling tides.
It is another clean and sustainable source of energy that has barely been put to work to power the planet. Some energy experts consider ocean power to be where wind power was twenty years ago. It’s the “wave” of the future. Waves are formed when wind blows over the water’s surface. In many parts of the world, the wind blows consistently enough to create non-stopping wave action along the shorelines. The energy contained in ocean waves comes from both the surface motion and the pressure fluctuations beneath the surface. Tides are also waves, but they are not created by the wind.
They exist in all the oceans due to the gravitational pull of the moon and the sun on the earth, mostly the moon. Mechanical energy from ocean waves and tides has tremendous potential as a source of alternative power. Throughout history, people living in wave-rich areas of the world have been trying different ways to harness that free energy. Tide mills in Europe date back to the Middle Ages. Tide mills took advantage of the height of low and high tides. The people constructed a dam that spanned a tidal inlet. At high tide, water flowed through a hannel, called a sluice, and into the dam reservoir via a oneway gate. When the tide began to fall, the gate automatically closed. The stored water was then released, and the energy of the flow turned a water wheel, which generated power. The first large-scale tidal power plant was built in France in 1966. Tidal and wave power can be generated in two basic ways. Ebb generation describes the method used by tide plants. The other method, called wave or tidal farming, has turbines anchored in the seabed, harvesting the underwater tidal currents.
There are both onshore and offshore systems for harvesting ocean energy. The onshore systems are built along shorelines, harnessing the power of breaking waves and rising tides. One type of onshore technology is called a Pendular Device. A box is open to the ocean on one end. The action of the waves causes a flap that is hinged over the opening to swing back and forth. That motion provides power for a hydraulic pump and generator. Another example is a tidal barrage, which is based on the early tidal mill designs and operates in much the same way.
An offshore example is a SeaGen Turbine. This machine resembles an underwater windmill, with two underwater propellers attached to a tall column. The whole structure is anchored to the seabed. Still another innovative device is called a Wave Dragon. It is an overtopping mechanism that allows waves to create a buildup of water. The water is then released. The energy of the falling water, much like a tide mill, can be used to turn hydro turbines and generate power. Other offshore wave energy systems use buoys with submerged pumps and generators.
One is called a Salter Duck. It uses the bobbing motion of ocean waves to power a pump. Most offshore systems are situated more than 131 feet (40 meters) deep in the ocean. As of today, many scientists and engineers believe that the global potential to employ ocean energy could power the world, if we could figure out how to both use and transport it in safe, practical and affordable ways that do little harm to the environment. While hundreds of designs have been proposed, patented and tried, there are just a few methods that are currently being used commercially.
There are both pros and cons to harnessing all that “free” power. Here are some of the *pros* for ocean energy: • It only requires waves and/or tides to work, a consistent, renewable, and dependable source of power. • There is no pollution from the devices. • Ocean energy has low operating and maintenance costs. • There are improved designs happening today. • It is a domestic source of energy found over much of the world. •Some systems also serve as storm surge barriers. There also some *const when it comes to ocean energy: • There can be high costs to construct the systems. There are potential impacts on marine life, tidal basins, and other ocean and shore ecosystems. Offshore systems can be a potential traffic hazard to shipping traffic. • Onshore systems can be an “eyesore. ” • Remote locations and transferring electricity to where it is needed can be costly. • Alternative energy is in direct competition with energy resources that are already subsidized, such as gas and oil.
Discussion and Research Projects: • Ocean energy sounds like an excellent source for alternative energy! But the impact it has on the environment and other oncerns are important, too. Discuss the pros and cons presented here, and challenge students to come up with other problems and their possible solutions. They should be armed with more information than we had room to include in this article. • Tidal gates were used during the Middle Ages. What other means did people in our history try to harness energy from waves or tides? • There are several types of devices being used or experimented with to harness the energy from the ocean today. A few are mentioned here as examples.
Have students research and study all the different devices they can find, identify if they are ebb generation or wave/tidal farming, then let groups pick out one method and present their findings on success, cost, environmental impact, etc. · Where are all the wave and tidal power plants in the U. S. or in the world today? Why were those locations chosen? What environmental impacts are they having? How do people make use of other alternative energy resources – not just ocean, but geothermal, hydroelectric, wind, and solar?
