HEP+-+Dominic

=__ Physics 11.4 presentations__= =__Hydroelectric Power__=

Long ago people used to use running water from rivers or streams to turn giant wooden wheels that were attached to grinding wheels to grind corn or wheat. For example, the photo on the right. The flow of the river turns the wheel at the bottom.



Today, we can use the power of rivers to feed our own electricity needs. Hydroelectric power uses the kinetic power of moving rivers to create electricity. In a typical hydroelectric dam, there are a few basic components:

//**Dam** - The dam holds back lots of water, creating a reservoir// //**Intake** - As seen on the left, gravity pulls water through the penstock which is a pipeline going to the turbine. This happens when the intake gates are opened. **Power Lines** - Power lines then carry the electricity to where it is needed. There is a more complicated version of exactly how the electricity is taken out however that is not part of this subject. //
 * Turbine** - The water, having built up a lot of pressure, turns the turbine that is connected to the generator above it.
 * Generators ** - The turbine blades turn, along with a series of magnets inside the generator. Giant magnets rotate past coils of copper, producing alternating current through moving electrons.
 * Transformer** - This is inside the powerhouse and it takes the alternating current (AC) and converts it to a higher-voltage current.


 * __More about the generator__ **

The explanation above about how the generator manages to turn the kinetic energy of the water into electricity so I will explain it in more depth here.

The turbine converts the energy of the water into mechanical energy. The generator then converts it into electrical energy.

Based on the principles of Faraday, when a magnet is moved past a conductor, it causes electricity to flow. The rotor is a large collection of large electromagnets that spins inside a circle of copper wire called the stator. When the turbine turns, the magnetic field between the copper coil and the magnets create an electric current.


 * __AN EXAMPLE - THE THREE GORGES DAM__

// __Statistics__ // 

The Three Gorges Dam is the largest concrete structure in the world, measuring 185m high and more than 2km long. It harnesses the power of the Yangtze River. It took 12 years to complete, starting in 1994. It has 26 turbines with plans to add more generating 18,200 megawatts, the largest in the world. In 2003, the sluice gates were closed, flooding scenic gorges and moving 1.4 million people to create a giant reservoir that holds as much water as Lake Superior.

**


 * __Pros of HEP__ **


 * Few Breakdowns
 * Renewable energy
 * Clean, no pollution
 * Can be shut down immediately


 * __Cons of HEP__**
 * May destroy ecosystems
 * Drowning/flooding of scenic and inhabited areas
 * Plant decay may cause as many greenhouse gases as conventional methods
 * Huge problems if the dam breaks
 * Expensive

//In the case of the three gorges dam, it took roughly 30 billion US dollars to build.//


 * __Bibliography__

http://drake.marin.k12.ca.us/stuwork/rockwater/Upload%20this%20doc--dams%20and%20hydropower%20report/pros%20and%20cons.html

http://ga.water.usgs.gov/edu/hyhowworks.html

http://www.howstuffworks.com/hydropower-plant.htm

http://www.energyquest.ca.gov/story/chapter12.html

More info found on** http://www.absoluteastronomy.com/topics/Three_Gorges_Dam