Hydroelectric+Energy+-+Conventional

Rachel & Hannah  **Hydroelectric Energy- Conventional**

**Hydroelectric Generation** Hydroelectric energy generation is the production of electricity from hydropower. This principle is based upon the conversion of energy from flowing water (generally rivers) into electrical energy for commercial, residential and industrial use. This electricity is produced from generators which are driven by water turbines, and it is the turbines which convert the potential energy from falling of fast-slowing water into mechanical energy. media type="youtube" key="rnPEtwQtmGQ" height="281" width="364" //__A More in depth overview:__// When generating hydroelectric power, water is collected and/or stored at a higher elevation and is then led downward through large pipes or tunnels, also known as //penstocks//; the difference between these two elevations is known as the //head//. As the pipes end, the falling water causes turbines to rotate, which thus drives generators. The //generators// are used to convert the turbines’ mechanical energy into electricity. //Transformers// are used to convert the alternating voltage which is suitable for the generators into a higher voltage which is better fit for long distance transmission. The structure in which the the turbines and generators are loacted, and into which the pipes feed, is called the //powerhouse//. Hydroelectric dams are created in order to raise the level of the water behind the dam which in turn creates a higher head and assures a steady flow through turbines, and evens out seasonal fluctuations in discharge. The theory behind this relies on the principles of gravity and kinetic energy. The amount of potential power from a volume of water is directly proportional to the head; a high-head requires much less water than a low-head to produce the same anout of power. Some dams are constructed so that the powerhouse is constructed so that the dam is to one side, allowing for part of the dam being to be used as a spillway to discharge excess water during a flood. In other areas, such as places where the river flows in a narrow steep gorge, the powerhouse can be found within the dam itself.

Moving water has been the most commonly used sour ce of renewable energy for thousands of years. In Ancient Greece and throughout the Roman Empire, mills which processed corn (ground wheat into flour)  were powered by rivers and streams. The Greeks discovered that the kinetic energy of the water current propels the wheel and converts into mechanical energy that runs the mill to grind the wheat/corn.  Come the 1300s, there were more than 5,000 water mills being operated in England alone. Near the end of the 19th century, it was realized that water could be used to generate energy. The first hydroelectric power plant opened in Niagara Falls, Canada in 1879. Two years later all the street lights of the city were hydropowered.  In 1882 the first hydroelectric power plant in the United States was put into commission. Located on the Fox River in Appleton, Wisconsin, it was generating 12 kilowatts of energy, enough to power 250 lightbulbs. Today, the world's largest hydroelectric power plant (second to the Three Gorges Dam in China, due for final completion in 2011) is the Itaipu dam on the Panama River. It supplied 25% of Brazil's and 80% of Paraguay's electricity in 2004.
 * History**

With the growing demand for electrical energy, many forms of new electrical generators are being developed. To succeed in today's society and to support current global viewpoints, generators need to be inexpensive to operate, reliable and environmentally friendly. This is conventional-hydroelectric-energy-generation's main advantage, as they fit into all three categories. In contrast, the methods of wind turbines and solar cells must be located in large, flat windy or sunny areas, which have high property values; and these sources cannot be consistantly relied upon since they depend on weather conditions . In the case of hydroelectricity, dependence on the natural water cycle results is a renewable and reliable source of energy generation- and the water is free! ** As well, in areas with heavy rainfall and/or mountainous topography, the use of hydroelectric power is much more efficeint. For these reasons it thrives in inhospitable or less-inhabited areas, where other generation methods need land which is heavily populated. Hydroelectricity can also thrive in countries with poor oil, coal or gas reserves, as these resources are not needed. Lastly it is highly environmentally advantageous because it does not produce atmospheric or thermal pollution. Therefore hydroelectricity has considerable potential worldwide, in both developed (e.g. Norway) and developing (e.g. Paraguay) countries.
 * Analysis

Another key economic benefit of hydroelectric power is pump storage. It is common for the demand on power to vary throughout the day. To even the load on the generators, pumped-storage hydroelectric stations are occasionally built. During off-peak periods, some of the extra power available is supplied to the generator operating as a motor, driving the turbine to pump water into an elevated reservoir. Then, during periods of peak demand, the water is allowed to flow down again through the turbine to generate electrical energy. Pumped-storage systems are efficient and provide an economical way to meet peak loads. In certain coastal areas, such as the Rance River estuary in Brittany, France, hydroelectric power plants have been constructed to take advantage of the rise and fall of tides. When the tide comes in, water is impounded in one or more reservoirs. At low tide, the water in these reservoirs is released to drive hydraulic turbines and their coupled electric generators. The drawbacks to hydroelectricity are not as exhaustive as other electricity sources, but still significant. Even though hydropower is currently the cheapest way to generate energy, the construction of the dam is very expensive and destructive. Damming rivers can disrupt wildlife and the land surrounding the water. Migration patterns of fish populations, such as salmon, can be permanently altered when they are barred from swimming up stream to spawn. Despite endeavors to reroute their journey, fish levels can significantly decrease. Dams aerate the water, but cause harm to river habitats by decreasing the level of dissolved oxygen in the water.

A controversial hydroelectric dam development is the Three Gorges dam on the Yangtze River, China. This is the world's largest dam, spanning 2.3 kilomtres in width and 185 metres in height. In China's endeavor to create a new mass source of electricity other than coal, they made serious sacrifices. Over 1 milion people have been displaced, as the reservoir behind the dam floods 632 square kilometres of land. This not only eradicates animal habitats, but destroys historical and architectural monuments. As well, submerged waste and industrial plants leak environmental pollutants into the reservoir. The dam is partially in use, but is not due to be completely functioning until 2011.