Hydroelectric power is generated through the energy of flowing water, using a turbine to power a generator. It is clean, renewable, and does not produce harmful waste or by-products. However, large projects can cause serious environmental problems, such as the displacement of people and destruction of habitats.
Hydroelectric power (HEP), or hydroelectricity, is electricity generated through the energy of flowing water. It has the advantage of using only renewable resources, and of not producing harmful waste or by-products, and is therefore seen by many as an environmentally friendly alternative to the burning of fossil fuels which still supplies most of the electricity consumed worldwide. HEP programmes, however, often encounter considerable opposition as they themselves cause serious environmental problems.
Principle
People have harnessed the energy of water movement for centuries. In ancient Greece and China, water wheels were installed in fast-flowing rivers to turn millstones and other equipment, and they continue to be used today in some parts of the world. In fact, these devices use gravity, as water flows from a higher area to a lower one.
Hydroelectric power plants are based on the same basic principle, but instead of using kinetic energy directly, the force of the water drives a turbine which in turn powers a generator, producing electricity that can be used on site or transported to other regions . As with other turbine methods of generating electricity, the magnets in the turbine move relative to the static conductors. This results in an electric current flowing through the conductors.
There are a number of different designs for hydroelectric power plants, but the most common involves building a large dam across a lake at a relatively high elevation to form a water reservoir and allow water to flow from it, in a controlled manner, downhill to the generator, which is at a lower elevation. Water flow can be maximized during periods of high electricity demand and reduced when demand is lower. In most cases, the water is replenished by rainfall, but some power plants can use the excess electricity to pump water to the reservoir at times of low demand.
Advantages
The main advantages of hydroelectricity are that it is clean and renewable. Since it does not involve the combustion of fossil fuels, such as coal, oil and natural gas, it does not produce emissions of harmful pollutants such as soot and sulfur dioxide. Equally important, it does not produce carbon dioxide, the gas that causes the “greenhouse” effect and which is believed to be responsible for climate change, through the production of energy. It has the advantage over nuclear energy that it does not generate hazardous waste that presents long-term disposal problems.
HEP is also renewable, as it does not use a limited resource. While coal, oil, natural gas and eventually even uranium will run out, water is inexhaustible. Once the plant has been built, the necessary water is available at no cost, unlike the fuels that have to be extracted from the ground. The water supply is continuously renewed in most areas by rainfall, which in effect means that the sun provides energy, as its heat evaporates water from the surface which falls as rain.
Disadvantages
While HEP is clean and renewable, it’s not necessarily environmentally friendly. Large projects capable of delivering significant amounts of electricity usually require damming lakes or rivers, resulting in the flooding of large areas of land. This can lead to the displacement of people and the destruction of habitats. Drastic alterations to waterways can also have a profound impact on wildlife, ecosystems and, in some cases, agriculture. Migrating fish, such as salmon, can have their waterways blocked by dams, although this can be mitigated by installing a fish ladder, a series of steps the fish are able to navigate.
The most suitable locations for hydroelectric plants are often of great scenic beauty and can lose some of their value due to new roads, pylons and other construction associated with a HEP project. Some projects have had unintended consequences. For example, the Aswan High Dam in Egypt, which was very successful in providing power, also controlled the annual flooding of the downstream River Nile. At first this was thought to be another benefit, but the floods had been laden with nutrient-rich silt which allowed for farming along the Nile, and once the dam was in place, all that silt collected uselessly in the reservoir. , depriving the downstream soil of necessary nutrients. Another possible problem, according to some studies, is that decaying vegetation in areas flooded to supply HEP can emit significant amounts of carbon dioxide, offsetting the benefits of clean energy generation.
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