Hydroelectric Power
Hydroelectric Power
Hydroelectric power, also called hydroelectric energy or hydroelectricity, is a form of energy that harnesses the power of water in motion — such as water flowing over a waterfall — to generate electricity. Hydropower uses a fuel —water — that is not reduced or used up in the process. Because the water cycle is an endless, constantly recharging system, hydropower is considered a renewable energy.
Click here to see short video on how energy is created.
Hydropower plants capture the energy of falling water to generate electricity. A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy. Click on the image below to explore how hydroelectric plant works through simulation.
The pros and cons of using hydroelectric power (for more details click here)
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The cost of using hydroelectric power
Hydropower is the most efficient way to generate electricity. Modern hydro turbines can convert as much as 90% of the available energy into electricity. The best fossil fuel plants are only about 50% efficient. In the U.S., hydropower is produced for an average of 0.85 cents per kilowatt-hour (kwh). This is about 50% the cost of nuclear, 40% the cost of fossil fuel, and 25% the cost of using natural gas.
The environmental impact of using hydroelectric power (for more details, click here)
Hydroelectric power includes both massive hydroelectric dams and small run-of-the-river plants. There are environmental impacts at both types of plants.
1. Land use
Hydroelectric plants in flat areas tend to require much more land than those in hilly areas or canyons where deeper reservoirs can hold more volume of water in a smaller space. Flooding land for a hydroelectric reservoir has an extreme environmental impact: it destroys forest, wildlife habitat, agricultural land, and scenic lands. In many instances, such as the Three Gorges Dam in China, entire communities have also had to be relocated to make way for reservoirs.
2. Wildlife impacts
Fish and other organisms can be injured and killed by turbine blades. Reservoir water is usually more stagnant than normal river water. As a result, the reservoir will have higher than normal amounts of sediments and nutrients, which can cultivate an excess of algae and other aquatic weeds. These weeds can crowd out other river animal and plant-life. In addition, water is lost through evaporation in dammed reservoirs at a much higher rate than in flowing rivers.
If too much water is stored behind the reservoir, segments of the river downstream from the reservoir can dry out. Thus, most hydroelectric operators are required to release a minimum amount of water at certain times of year. If not released appropriately, water levels downstream will drop and animal and plant life can be harmed. In addition, reservoir water is typically low in dissolved oxygen and colder than normal river water. When this water is released, it could have negative impacts on downstream plants and animals.
3. Life-cycle global warming emissions
Emissions during a facility’s operation can be significant. Such emissions vary greatly depending on the size of the reservoir and the nature of the land that was flooded by the reservoir. After the area is flooded, the vegetation and soil in these areas decomposes and releases both carbon dioxide and methane. The exact amount of emissions depends greatly on site-specific characteristics. However, current estimates suggest that life-cycle emissions can be over 0.5 pounds of carbon dioxide equivalent per kilowatt-hour. For comparison, estimates of life-cycle global warming emissions for natural gas generated electricity are between 0.6 and 2 pounds of carbon dioxide equivalent per kilowatt-hour and estimates for coal-generated electricity are 1.4 and 3.6 pounds of carbon dioxide equivalent per kilowatt-hour.
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