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A Renewable Energy Resource: The Hydroelectric Power

Types of Energy
Energy resources are materials or processes in nature that can be used to do work. Generally speaking, energy sources can be divided into two categories, non-renewable energy resources, and renewable energy resources. Non-renewable energy resources are resources that cannot be replenished in a short period of time (for example: oil, natural gas, uranium, coal). On the other hand, renewable energy resources are resources that can be replenished within a short period of time (for example: hydropower, wind energy, tidal energy, bio fuels).

Hydroelectric Power
The most widely used type of renewable energy is hydroelectricity. Most hydroelectric energy comes from the potential energy of dammed water driving a turbine to generate electricity, but variations of hydroelectric energy uses the kinetic energy of undammed water. Ultimately, hydroelectric power is a combination of solar energy and gravitational potential energy. Sun¡¯s radiant energy causes water to evaporate and move to higher elevation, and water gains gravitational potential energy when it condensate.
In 1870, world¡¯s first hydroelectric power plan began to generating electricity to the small town of Cragside, England. Within a few decades, hundreds of small-scaled hydroelectric power plan were built around the world. Now, hydroelectricity is world¡¯s biggest source of renewable energy, it supplies about 20% of world¡¯s electricity.

How does a hydroelectric power plan work?
Water trapped in a hydroelectric dam conserves large amount of gravitational potential energy. As the difference between the water level and the water outflow increase, so does the potential energy of the water. The water run through a channel called the penstock to drive the turbine. The rotational energy of the turbine is converted to electricity by the generator. The electricity generated is supplied to public electricity network, and is transferred to homes and businesses.

Controversy
Although...