1. Hydroelectricity, better alternative energy to replace coal<br />Name: Hyo Ji Kim<br />Grade: 10<br />Word Count: 1202<br />Electricity is one of the most indispensable energy in our life. There are many things around us, which are powered by electricity. The energy that people use to create electricity comes from different sources. Some energy resources, including oil, and coal are not endless to use, and they are almost running out today. However, others, such as water, and sunlight are abundant. Among those renewable energy sources, waterpower takes an important part of generating worldwide electricity. This is because some 20 percent of global electricity has been produced by hydro energy projects (Allianz, 2009). This essay will talk about background information, how to solve CO2 problems, disadvantages and advantages, factors of science that are all related to hydropower.<br />Figure 1: Parts of water turbine (U.S Geological Survey, 2009)<br />A hydroelectricity generator is operated in most of water power installations. There is a shaft at the top of the water turbine, which is the fundamental part to produce electricity (See Fig 1). The shaft makes the rotor turn when it is rotating. Then, the rotor goes inside a circular stator. The thing we need to know is the rotor is wrapped in separate coils within a series of long copper wires. That is placed inside a magnetic field. As each coil passes through a magnet in the stator, tiny particles called electrons are created. They flow inside the coil, and finally, electricity is generated from this flow of electrons. Finally, electricity is generated as magnetic field changes in the coils of stator and its change induces an alternating current in the coils of stator (eHow, 2010).<br />Figure 2: How hydroelectric dam works (BBC Bitesize Physics, 2011)<br />Hydropower dam generates electricity in some steps. A dam is constructed near a lake or a big river, and thereby water can be trapped in high level reservoirs. As water is stored, water flows into the dam wall. This water has gravitational potential energy because of the great height of the dam (See Fig 2). As water rushes through the penstock, there is a potential for water to get kinetic energy. The moving water then turns the turbine propeller, where is at the end of the penstock. The shaft from the turbine goes up into the generator, and kinetic energy of the water is transformed to electricity. Electricity is finally produced from the generator. Power lines that connected to the generator carry electricity to people's houses. The rest of water keeps going past the propeller through the tailrace into the river.<br />Over a century ago, coal had taken the place of alternative energy to generate electricity. At first, burning step must be required for creating electricity from coal. However, when coal is burned, harmful air pollutants are released. On average, the United States emitted 2,249 lbs/MWh of carbon dioxide, 13 lbs/MWh of sulfur dioxide, and 6 lbs/MWh of nitrogen oxides by coal-fired generation (U.S. EPA, 2007).<br />Nowadays, hydro energy becomes the best solution to replace coal. Hydropower causes minimal atmospheric pollution than nonrenewable energy sources, such as fossil fuels, and coal. Hydroelectric power plants don't require to burn any fuel. Water is the only resource that hydro energy uses to generate electricity, and thereby it does not emit carbon or greenhouse gases. In fact, 120 million tons of coal is not burned per year because of hydropower projects (Hydroelectric Power). Consequently, almost 249 tons of carbon dioxide are not released into the atmosphere since hydro energy has been utilized (FWEE, 2001). Global warming or ozone depletion are getting slow. In Canada, hydropower is worked on Vancouver’s Sky Train and Montreal ’s subway. The use of hydro energy on public transportation has been resulted the great reduction of CO2 release in these two cities (Canadian Hydropower Association, 2009).<br />Building the hydro dams is necessary to generate electricity, but it has obvious disadvantages. To begin with, hydropower dam brings a great influence on natural river systems. Hydro dams often produce cold and less oxygen water at the bottom of the lake. Fish can be hurt or can be killed, because fish living downstream are adapted to heated and oxygen-rich water (U.S EPA, 2007). Furthermore, Hydro dam is usually required more cost and much time to build than people's expectations. For instance, the plan of constructing Itaipu Dam in Paraguay changed to $20 billion over 18 years from $3.4 billion over 15 years (Stephanie Joyce, 1997).<br />In contrast, there are some advantages of hydro dams. First of all, hydro dams are always able to supply electricity when the energy is demanded instantly. This is because the dam stored water every time to the grid for future use or extra electricity. Moreover, the operation of hydro dams does not create any waste while generating electricity. Electricity is produced in need of using up the water after strong force of water turns the turbine, and thereby there is no waste (Hydroenergy,2009). Hydro energy has remarkable environmental concerns. The construction of hydroelectric dam induces damage on wildlife habitats. Various fish populations are affected by hydroelectric power plants in different ways. Adult salmon have to swim upstream for breeding, but they are not able to move because of large dams. In addition, young salmon live near hydropower plants can be killed by turbine blades while traveling downstream toward the ocean. For remarkable example, there have been dramatic decreases of salmon populations in Northwest due to the huge dams in the Columbia River Basin (U.S. EPA, 2007).<br />Figure 3: Protest movement against hydro dam construction on the Narmada River of Indian who will be displaced soon (Rally, 2008)<br />One of the important social issues of hydro energy is changing people's lives. Approximately 32 to 63 million people, who are usually poor and sick, have been displaced by the construction of hydropower dams (Akwara Christopher, 2009). They should migrate due to the risk of flood and should leave behind their lands. Therefore, displaced people are paid to recompense for it (See Fig 3). Sometimes, people need to wait long time to get money when the government does not have enough money to restore their livelihoods immediately. For example, more than 15 years took for compensation of displaced people after the Aswan Dam in Egypt was constructed (The Pros and Cons of Water Power, 2007). Another social concern that is related to hydropower is an unfair distribution. In some cases, the electricity from hydroelectric dams does not reach rural places. As a result, people in countryside don't get any power. This is because the government only concentrates on power for cities, businesses to make more money. For instance, half of all Paraguayans have no electricity even though their country owns the Itaipu dam, world's largest hydropower facility (The Pros and Cons of Water Power, 2007).<br />To summarize, hydropower is the best sustainable energy source to solve CO2 problems with its minimal impact on environment. In the future, it will be definitely essential to conserve environment and to produce worldwide electricity. However, we still should take much time on improving hydro energy. 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