Energy Generation and Storage Using Water  Printable view

Energy from falling water

Falling water possesses energy. Look at the photo of a water wheel driven by falling water. When water falls downwards, its gravitational potential energy is converted into kinetic energy. The kinetic energy is transferred to the water wheel and the water wheel rotates. If the water wheel is connected to a generator, electricity can be generated. This is the basic principle of hydroelectricity: using falling water to generate electricity.

Fig. 1   A water wheel driven by falling water.   Fig. 2   Hydroelectricity is an important renewable energy source.

Of course, the design of a hydroelectric power plant is much more advanced than that of a water wheel. For a typical hydroelectric power plant, a dam is built to store water at a higher level. Water is controlled to flow through the dam, driving the turbine generators near the base of the dam to generate electricity.

The animation below shows the operation of a hydroelectric power plant.

Flash animation: Hydroelectric power plant
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Water cycle

How does water get to high places in nature, allowing us to make use of its gravitational potential energy to generate electricity? The answer lies in the water cycle of the Earth.

Let's take a look at the water cycle illustrated in the figure below. When the sun heats up the water in the sea, some water is evaporated. The rising water vapour forms clouds in the sky. The water vapour condenses and falls to the ground as rain. As water flows down from high places as river, its gravitational potential energy can be used to produce electricity.

Fig. 3   The water cycle: (1) solar radiation heats up the sea, (2) sea water vaporizes, (3) water vapour forms cloud, (4) water vapour condenses as rain and falls to the ground, (5) water flows down from high places as rivers, returning water to the sea. Some water is retained by the land.