| Tidal power traditionally involves erecting a | | | | to work well, you need large increases in |
| dam across the opening to a tidal basin. The | | | | tides. An increase of at least 16 feet |
| dam includes a sluice that is opened to allow | | | | between low tide to high tide is needed. |
| the tide to flow into the basin; the sluice | | | | There are only a few places where this tide |
| is then closed, and as the sea level drops, | | | | change occurs around the earth. Some power |
| traditional hydropower technologies can be | | | | plants are already operating using this idea. |
| used to generate electricity from the | | | | One plant in France makes enough energy from |
| elevated water in the basin. Some researchers | | | | tides to power 240,000 homes. |
| are also trying to extract energy directly | | | | |
| from tidal flow streams. | | | | 3. Ocean Thermal Energy |
| | | | |
| There are three basic ways to tap the ocean | | | | The final ocean energy idea uses temperature |
| for its energy. We can use the ocean's waves, | | | | differences in the ocean. If you ever went |
| we can use the ocean's high and low tides, or | | | | swimming in the ocean and dove deep below the |
| we can use temperature differences in the | | | | surface, you would have noticed that the |
| water. | | | | water gets colder the deeper you go. It's |
| | | | warmer on the surface because sunlight warms |
| 1. Wave Energy | | | | the water. But below the surface, the ocean |
| | | | gets very cold. That's why scuba divers wear |
| Kinetic energy (movement) exists in the | | | | wet suits when they dive down deep. Their wet |
| moving waves of the ocean. That energy can be | | | | suits trapped their body heat to keep them |
| used to power a turbine. In this simple | | | | warm. |
| example, the wave rises into a chamber. The | | | | |
| rising water forces the air out of the | | | | Power plants can be built that use this |
| chamber. The moving air spins a turbine which | | | | difference in temperature to make energy. A |
| can turn a generator. When the wave goes | | | | difference of at least 38 degrees Fahrenheit |
| down, air flows through the turbine and back | | | | is needed between the warmer surface water |
| into the chamber through doors that are | | | | and the colder deep ocean water. Using this |
| normally closed. | | | | type of energy source is called Ocean Thermal |
| | | | Energy Conversion or OTEC. It is being used |
| This is only one type of wave energy system. | | | | in both Japan and in Hawaii in some |
| Others actually use the up and down motion of | | | | demonstration projects. |
| the wave to power a piston that moves up and | | | | |
| down inside a cylinder. That piston can also | | | | Some of the oldest ocean energy technologies |
| turn a generator. Most wave-energy systems | | | | use tidal power. All coastal areas |
| are very small. But, they can be used to | | | | consistently experience two high and two low |
| power a warning buoy or a small light house. | | | | tides over a period of slightly greater than |
| | | | 24 hours. For those tidal differences to be |
| For more information see: Ocean Energy | | | | harnessed into electricity, the difference |
| Potential | | | | between high and low tides must be at least |
| | | | five meters, or more than 16 feet. There are |
| 2. Tidal Energy | | | | only about 40 sites on the Earth with tidal |
| | | | ranges of this magnitude. If there is one |
| Another form of ocean energy is called tidal | | | | thing we can safely predict and be sure of on |
| energy. When tides comes into the shore, they | | | | this planet, it is the coming and going of |
| can be trapped in reservoirs behind dams. | | | | the tide. This gives this form of renewable |
| Then when the tide drops, the water behind | | | | energy a distinct advantage over other |
| the dam can be let out just like in a regular | | | | sources that are not as predictable and |
| hydroelectric power plant. In order for this | | | | reliable, such as wind or solar. |