Energy sources

HYDRO

What is it?

A fast-flowing river has the power to push small fish and rubble downstream. But did you know that this power can also be harnessed to produce electricity? Electricity produced from the force of running water is known as hydroelectric power.

Running water is a renewable energy source that has been used for thousands of years. For example, water mills use the flow of water to turn a wheel to grind grain. The first use of water flow to make electricity was in 1882 on the Fox River in the United States. It produced enough electricity to light two paper mills and a house!

Hydroelectric stations are built where there is running water. The water is channelled past a turbine, which turns with the water flow and creates electricity. The water then goes back into the river and through to the ocean. After that, the heat from the sun evaporates the water so that it rises into the atmosphere and forms clouds.

These clouds eventually rain back into the rivers and lakes - restarting the cycle. So it's easy to see how hydroelectricity is a renewable source of energy.

Three main types of hydroelectric stations

1. Dams - this is the most common type. A river is dammed, and the water is released past the turbines whenever electricity is needed.
2. Rivers - instead of building a dam, sometimes a power station is built on a fast-flowing river. The generating process is the same, except the water flow cannot be controlled or stored for later use.
3. Pumped storage - this is where two dams or lakes are used, one higher than the other. When electricity is needed, water flows from the top dam down past the power station, and into the bottom dam. When electricity is no longer needed, water is pumped back up to the top dam to be ready for the next time. Pumped storage systems are usually used in the day when the most electricity is needed, and the top dam is usually refilled at night when much less electricity is needed.

Advantages

Hydroelectricity doesn't release any gases into the atmosphere and produces no waste. This makes it very environmentally friendly. It is renewable and more reliable than some other forms of renewable energy - like solar and wind power.

Unlike wind and sunshine, water can be stored when there is a lot of it, and used when there is not. Hydroelectric power stations can start almost instantly, unlike coal fired stations which have to wait for coal to be mined.

Hydroelectric stations are not very expensive to run and have a long life. Many dams built for hydroelectricity were built for flood control or irrigation, and so building costs are shared. Dams are also popular for sightseeing, water sports and other recreational activities.

Disadvantages

Unfortunately, large dams can have a negative effect further upstream - they can displace all animals living in the area, moving them out of their homes, and take up large areas of land. The amount of water and quality downstream can be reduced, having a harmful effect on plant life.

Use in Australia and the world

Hydroelectricity is by far the most common form of renewable energy. It produces 18% of the world's electricity and makes up around 10% of the electricity generated in Australia. The two places where most of it is produced are Tasmania and the Snowy Mountains.