(RHIE) Hydropower Lesson

Hydropower

Hydropower generates electricity

Today, moving water can also be used to make electricity. Hydro means water. Hydro-electric means making electricity from water power.

Hydropower is the renewable energy source that produces the most electricity in the United States. It accounted for about 7% of total U.S. electricity generation and 56% of generation from all renewables in 2012.

Hydropower and ocean energy systems indirectly tap the Earth's solar energy flux, which drives the cycling of water between Earth's surface and the atmosphere and heats the upper layer of the oceans. By damming rivers for hydropower or placing turbines in zones of the ocean areas with significant tides and currents, we can use the power of flowing water to generate electricity. Today hydropower generates about 17 percent of world electricity supplies (the same as nuclear energy, although hydropower is credited with only a third as much primary energy as nuclear because it does not generate two units of heat for every unit of electricity). Ocean power systems are still at an experimental stage.

Hydropower relies on the water cycle

Understanding the water cycle is important to understanding hydropower. In the water cycle-

• Solar energy heats water on the surface, causing it to evaporate.
• This water vapor condenses into clouds and falls back onto the surface as precipitation (rain, snow, etc.).
• The water flows through rivers back into the oceans, where it can evaporate and begin the cycle over again.

Mechanical energy is harnessed from moving water

The amount of available energy in moving water is determined by its flow or fall. Swiftly flowing water in a big river, like the Columbia River that forms the border between Oregon and Washington, carries a great deal of energy in its flow. Water descending rapidly from a very high point, like Niagara Falls in New York, also has lots of energy in its flow.

In either instance, the water flows through a pipe, or penstock, then pushes against and turns blades in a turbine to spin a generator to produce electricity. In a run-of-the-river system, the force of the current applies the needed pressure, while in a storage system, water is accumulated in reservoirs created by dams, then released as needed to generate electricity.

Most U.S. hydropower is in the West

Over half of U.S. hydroelectric capacity for electricity generation is concentrated in Washington, Oregon, and California. Approximately 29% of total U.S. hydropower was generated in Washington in 2013 where the Grand Coulee Dam, the largest hydroelectric facility in the United States, is located. While Washington hosts the nation's largest hydroelectric facility and has the most generating capacity of any state, New York State has the largest hydroelectric capacity of all states east of the Mississippi River.

Wave Energy

The world's ocean may eventually provide us with energy to power our homes and businesses. Right now, there are very few ocean energy power plants and most are fairly small. But how can we get energy from the ocean?

There are three basic ways to tap the ocean for its energy. We can use the ocean's waves, we can use the ocean's high and low tides, or we can use temperature differences in the water. Let's take a look at each.

Kinetic energy (movement) exists in the moving waves of the ocean. That energy can be used to power a turbine. In this simple example, to the right, the wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator.

When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.

This is only one type of wave-energy system. Others actually use the up and down motion of the wave to power a piston that moves up and down inside a cylinder. That piston can also turn a generator.

Most wave-energy systems are very small. But, they can be used to power a warning buoy or a small light house.

Tidal Energy

Another form of ocean energy is called tidal energy. When tides comes into the shore, they can be trapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant. Tidal energy has been used since about the 11th Century, when small dams were built along ocean estuaries and small streams. the tidal water behind these dams was used to turn water wheels to mill grains.

In order for tidal energy to work well, you need large increases in tides. An increase of at least 16 feet between low tide to high tide is needed. There are only a few places where this tide change occurs around the earth. Some power plants are already operating using this idea. One plant in France makes enough energy from tides (240 megawatts) to power 240,000 homes.

This facility is called the La Rance Station in France. It began making electricity in 1966. It produces about one fifth of a regular nuclear or coal-fired power plant. It is more than 10 times the power of the next largest tidal station in the world, the 17 megawatt Canadian Annapolis station.

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