How much solar energy is used today?
Above - A large photovoltaic array on a commercial building roof, which adds to the power supply needs of that building.
It is estimated that enough sunlight falls on the earth’s surface every hour to meet world energy demand for an entire year. Although the sun’s energy is free, special technology is required to transform it into other energy forms, such as electricity. The cost of the technology, for example photovoltaic cells, can be quite expensive. Large amounts of energy from the sun is used around the world, but solar power provides less than 0.1 per cent of the world’s electricity. In the United States, more than 10,000 homes are powered entirely by solar energy.
Renewable sources contributed to five per cent of energy used in Australia’s electricity generation in 2004/2005. In Western Australia, solar energy accounted for about 0.4 per cent of electricity generation in 2005/2006. Instead, Western Australia predominantly relies on fossil fuels - coal, petroleum and natural gas – for our energy needs.
These fuels have taken millions of years to form from fossilised plant and animal remains crushed deep below the earth's crust (although natural gas can also be of recent formation). Over a long period of time the combination of heat and pressure has caused the fossilised remains to become rich sources of heat energy which can be burned in power stations to provide electricity. And because plant and animal life are dependent on the sun's energy we can say that coal, petroleum and natural gas are the indirect results of solar energy – or solar energy stored up from long, long ago.
 Next Section >> History of solar power.
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