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So What is Renewable Energy?

Solar Energy

The sun provides energy in two forms – light and heat. The sun can be used to heat water in our homes and businesses. It can also produce electricity. Energy produced by the sun is called solar power.

Since the beginning of mankind we have used the energy of the sun to dry clothes and food, but it wasn't until 1954 that scientists in the United States worked out a way to use the sun to create electricity.

Solar energy falls into two main categories:

1. "Solar photovoltaic" energy.

The scientists invented photovoltaic cells (or panels) to capture the sun's energy and turn it into electricity. They wanted to use this solar electricity to power satellites in space.

Photovoltaic cells are made up like a sandwich - two layers of silicon containing special chemicals. Sunlight is used to charge electrons in the silicon layers. The energised electrons move through the cell and flow into a wire, creating an electric current.

You have many options for using renewable energy at home — from solar-powered outdoor lights to buying renewable energy from your utility to even producing solar electricity at home with photovoltaic (PV) cells.

Solar photovoltaic power is the same technology that powers some calculators and watches. It is also used for remote telephones in some regional areas. The power of the sun is also used as a direct source in solar hot water units.

Solar power is particularly useful in remote areas (and there are a lot of these in Australia) where regular electricity supply is not available.

EnergyAustralia has a 2.75 hectare solar farm (the size of about 5 football fields) at Singleton in NSW. It is the largest of its type in the southern hemisphere and produces enough electricity (400 kW) each year to power about 100 homes.

By generating electricity through the sun we prevent the release into the atmosphere of tonnes of greenhouse gases each year!

2. "Solar thermal" energy (includes solar hot water).

Energy from the sun is absorbed and used to heat things like water. The hot water can be used directly or it can be used to create steam to drive a small turbine which generates electricity. There are not many working examples of this in Australia but there has been a lot of research into it.

Advantages of using solar energy

  • It's almost free once the equipment is installed.
  • Energy from the sun is renewable (it won't run out).
  • It is very useful for remote areas that are not connected to the main electricity grid.
  • It is environmentally safe (ie it produces no greenhouse gases).
  • Australia has heaps of sunshine!

Disadvantages of using solar energy

  • It doesn't work well on days when it is overcast or cloudy and it doesn't work at all at night.

Wind Power

Wind is moving air. It is created when the sun heats the air and cooler air moves in to replace it. This causes wind. Through the ages people have learned to harness the wind's energy. Like the sun, it can also be used to create electricity.

Windmills are used in many countries (such as the Netherlands) to capture the wind's energy. You can also find windmills in parts of outback Australia.

The moving sails of the windmill are connected to wheels that turn to operate machinery. The machinery is used to grind wheat and othergrains into flour or to pump the water from place to place to help irrigate the land.

The energy from turning windmills can also be used to drive turbines which generate electricity. Wind energy is useful for making electricity because it is a renewable resource and does not create pollution or cause damage to the environment.

Wind turbines feature a number of components, including blades, a shaft, a generator and a tower. The blades look like propellers, except that instead of creating wind, they catch the wind.

The shaft is connected to the blades, and it rotates as the blades turn with the wind. The shaft runs to the generator. The generator transforms the rotations of the shaft mechanical energy into electrical energy.

Advantages of using energy from the wind

  • It's free once you install the equipment.
  • Energy from wind is renewable (ie. it won't run out)
  • It is very useful for remote areas that are not connected to the main electricity grid.
  • It is environmentally safe (ie it produces no greenhouse gases).
  • Land used for wind farms can usually be used for other things as well (like farming).
  • Australia has lots of wind!

Disadvantages of using energy from the wind

  • The speed of the wind often changes and some days there is no wind at all.
  • Very windy areas are hard to find, and are often near the coast where land is more valuable.
  • Generating energy from wind creates noise, so turbines shouldn't be built near houses.
  • It can harm wildlife (birds can land on them), so turbines shouldn't be built near bird habitats.
  • They can be quite large and some people think they're an eye-sore.

Landfill or Biomass Energy


Most of the garbage we put out ends up at the rubbish dump. The average person is said to throw away almost 2 kg of rubbish every day, or 728 kg per year.

Most rubbish we throw out is buried in the ground (also known as landfill). The gas generated by landfill as it rots (biomass) is another form of renewable or green energy.

Landfill gas is created when the waste you throw away starts rotting (or decomposing) in the ground. This gas would normally just seep through the ground and into the atmosphere, contributing to environmental problems, like the greenhouse effect. However, it can be captured and processed to create electricity.

Landfill is collected, dried (to get rid of any water), and then filtered (to get rid of any waste particles). It is then fed through pipes to a gas generator that burns the gas to create electricity. The electricity then makes its way to your home and business via the electricity network.

While biomass energy is not as popular as other renewable methods, the interest in biomass as an alternate energy source is growing.

Advantages of using energy from biomass

  • It is environmentally friendly and efficient.
  • It is more reliable generator of electricity than energy from the wind or the sun.
  • It reduces the level of greenhouse gases which landfill produces.
  • When landfill gases are collected the rubbish dump smells better. Plants near the dump also grow better.

Disadvantages of using energy from biomass

  • As the community becomes more environmentally aware (reducing the amount of waste they create through recycling), the amount of available landfill will be reduced.
  • Much greater quantities of landfill gases are required to create electricity (compared to fossil fuels).
  • Biomass energy is more expensive to produce because it is still being fully developed.

Geothermal Energy

Geothermal energy is energy from the heat of the earth. It has been used for thousands of years in some parts of the world for hot water, cooking and heating. It can also generate electricity using steam produced from heat found beneath the surface of the earth.

When water flows over hot rocks, hot water and steam are created and escape to the earth's surface. Bubbling mud pools, hot springs and geysers are examples of geothermal energy. Volcanoes are very violent examples of this type of energy.

The hot water and steam created underground can be used to create electricity (by turning turbines) to heat homes and other buildings. The steam is collected, and used to power a generator, in the same way it is used in a coal fired power station.

The Maoris of New Zealand use hot rocks to cook food in the ground. Around the world people also swim in warm natural springs to help soothe body aches and pains.

Advantages of using geothermal energy

  • It's free once built.
  • It is renewable (ie. it won't run out).
  • It does not take up very much land, and does not spoil the landscape.

Disadvantages of using geothermal energy

  • Some geothermal sites may literally run out of steam.
  • Hazardous minerals (which are difficult to dispose of) may be produced.
  • Geothermal energy sites can be difficult to find.

Hydro Power

Hydro power is electricity created from the force of running water. It is less expensive than mining fossil fuels and does not contribute to the greenhouse effect. Unlike other renewable sources like the sun or wind, water can be stored which makes it a great way to create electricity.

Rivers, dams and waterfalls can be used to generate hydro-electricity. Hydroelectric stations are built where there is running water. The most common are located in dams, where water is stored.

To make hydroelectric power, water from rain or melting snow is collected and stored in the dam. The flow of this water can be controlled with the opening and closing of the gates or pipes. The dam wall can also create a high water level, which creates more pressure in the pipes to the turbine.

A large pipe carries the water from the dam to the turbine. The pressure of the water pushes against the blades and turns the turbines. The rotating turbine is connected to a generator which makes the electricity.

Hydroelectricity provides around 10% of the electricity generated in Australiaand 18% throughout the world.

The most famous source of hydroelectric power is the Snowy Mountains Hydro-Electric Scheme in Australia.

Hydro-power is the leading source of renewable energy. It provides more than 97% of all energy produced by renewable sources. Other renewable sources – solar, wind, biomass and geothermal – account for only 3% of the energy.

Advantages of using energy from water

  • It is renewable.
  • Hydroelectricity produces no gas emissions or waste.
  • It is more reliable than solar and wind power because water can be stored and there is more of it, more often.
  • Hydroelectric stations are inexpensive to operate.

Disadvantages of using energy from water

  • Large dams take up large areas of land and can cause fish and other animals to relocate.
  • Plant life can be affected by a change in water quality.
  • The power stations are expensive to build.
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