HYDROPOWER

1. HYDROPOWER By: Tanasia Johnson, Erica Mullikin, Claudia Pagan, Tatiana Roberts, and Kristin Tucker

2. What is Hydropower? • Hydropower: Is energy created using water power. It is created when we use gravity to move the water and create electricity. It is a renewable energy source. • Hydropower works by using a large amount of moving water to move the blades in a turbine and spin a generator to produce electricity. • It is one of the oldest sources of energy for humans

3. Materials Used For Hydropower • Materials Used in Hydropower • Water • Waterfalls located in rivers or water flowing downhill Dams • Dam - Holds the water back. Most hydropower plants rely them. This creates a large reservoir. Usually reservoirs formed are used as recreational lakes, like lake Roosevelt at the Grand Coulee Dam. • Intake – “Gates on the dam open and gravity pulls the water through the penstock, a pipeline that leads to the turbine. Water builds up pressure as it flows through this pipe.” • Turbine - The water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. The most common type of turbine for hydropower plants is the Francis Turbine, which looks like a big disc with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 90 revolutions per minute (rpm), according to the Foundation for Water & Energy Education (FWEE).

4. Materials Continued • Generators - As the turbine blades turn, so do a series of magnets inside the generator. Giant magnets rotate past copper coils, producing alternating current (AC) by moving electrons. • The heart of the hydroelectric power plant. • Most hydropower plants have a lot of these generators. • Generates the electricity. • “The basic process of generating electricity in this manner is to rotate a series of magnets inside coils of wire. This process moves electrons, which produces electrical current.” • Transformer - The transformer inside the powerhouse takes the AC and converts it to higher-voltage current. • Power lines - Out of every power plant come four wires: the three phases of power being produced simultaneously plus a neutral or ground common to all three. • Outflow - Used water is carried through pipelines, called tailraces, and re-enters the river downstream.

5. Materials Continued Pumped-Storage Plants • Pumped-storage plant- In a conventional hydropower plant, the water from the reservoir flows through the plant, exits and is carried down stream. A pumped-storage plant has two reservoirs: • Upper reservoir - Like a conventional hydropower plant, a dam creates a reservoir. The water in this reservoir flows through the hydropower plant to create electricity. • Lower reservoir - Water exiting the hydropower plant flows into a lower reservoir rather than re-entering the river and flowing downstream. • Using a reversible turbine, the plant can pump water back to the upper reservoir. This is done in off-peak hours. Essentially, the second reservoir refills the upper reservoir. By pumping water back to the upper reservoir, the plant has more water to generate electricity during periods of peak consumption.

6. How Hydropower Is Used Microhydropower System -Use energy in flowing water to produce electricity or mechanical energy. -Run-off-the-river systems: -A portion of the river's water is diverted to a channel, pipeline, or pressurized pipeline (penstock). The water is delivered to a turbine or waterwheel. The moving water rotates the wheel or turbine, which spins a shaft. The motion of the shaft can be used for mechanical processes, such as pumping water, or it can be used to power an alternator or generator to generate electricity. -These systems don't require large storage reservoirs. -Often used for microhydropower systems. -Can be connected to a electric distribution system or a stand alone grid -Both used to power homes and business.

7. How It is Used Continued Hydroelectric Power plant -Hydroelectric energy is produced by the force of falling water. The capacity to produce this energy is dependent on both the available flow and the height from which it falls. -Building up behind a high dam, water accumulates potential energy. This is transformed into mechanical energy when the water rushes down the sluice and strikes the rotary blades of turbine. The turbine's rotation spins electromagnets which generate current in stationary coils of wire. Finally, the current is put through a transformer where the voltage is increased for long distance transmission over power lines. Seven percent of the energy produced in the United States is produced by hydropower.

8. Advantages of Hydropower Once a dam is constructed, electricity can be produced at a constant rate. If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when electricity demand is high. Dams are designed to last many decades and so can contribute to the generation of electricity for many years / decades. The lake that forms behind the dam can be used for water sports and leisure / pleasure activities. Often large dams become tourist attractions in their own right.

9. Advantages Continued The lake's water can be used for irrigation purposes. The build up of water in the lake means that energy can be stored until needed, when the water is released to produce electricity. When in use, electricity produced by dam systems do not produce green house gases. They do not pollute the atmosphere.

10. Disadvantages of Hydropower Dams are extremely expensive to build and must be built to a very high standard. The high cost of dam construction means that they must operate for many decades to become profitable. The flooding of large areas of land means that the natural environment is destroyed. People living in villages and towns that are in the valley to be flooded, must move out. This means that they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power schemes can go ahead. The building of large dams can cause serious geological damage. For example, the building of the Hoover Dam in the USA triggered a number of earth quakes and has depressed the earth’s surface at its location.

11. Disadvantages Continued Although modern planning and design of dams is good, in the past old dams have been known to be breached (the dam gives under the weight of water in the lake). This has led to deaths and flooding. Dams built blocking the progress of a river in one country usually means that the water supply from the same river in the following country is out of their control. This can lead to serious problems between neighboring countries. Building a large dam alters the natural water table level. For example, the building of the Aswan Dam in Egypt has altered the level of the water table. This is slowly leading to damage of many of its ancient monuments as salts and destructive minerals are deposited in the stone work from ‘rising damp’ caused by the changing water table level.

12. Works Cited Perlman, Howard. "Hydroelectric Power and Water. Basic Information about Hydroelectricity, USGS Water Science for Schools." USGS Georgia Water Science Center - Home Page. 8 Feb. 2011. Web. 16 Oct. 2011. <http://ga.water.usgs.gov/edu/wuhy.html>. "Energy Savers: Exploring Ways to Use Hydropower." EERE: Energy Savers Home Page. 9 Feb. 2011. Web. 16 Oct. 2011. <http://www.energysavers.gov/renewable_ energy/hydropower/index.cfm/mytopic=50006>. "HowStuffWorks "Hydroelectric Footwear"" HowStuffWorks "Science" Web. 10 Oct. 2011. <http://science.howstuffworks.com/environmental/energy/hydropower-plant4.htm>.