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Solar Energy

Sensational solar cells

Scientists at the Australian National University have developed technology that reduces the cost of solar cells and will revolutionise solar energy.

What's the problem?

The only energy source that can cope with the increasing demand of humans in the long run is the Sun. But before we see solar technologies on a large scale in electricity generation, they will have to become much cheaper. Solar energy systems must compete against non-renewable, environmentally unfriendly, fossil fuels on economic grounds.

The biggest single cost in solar energy systems is the high quality silicon needed for the cells. A solar cell, or photovoltaic cell (which basically means 'light energy to electrical energy') contains a thin sheet or wafer of high quality, expensive silicon. The standard method for producing these sheets, which involves slicing up thick pieces, is relatively difficult and wastes a lot of silicon.

A great Aussie solution

New technology developed by Australian researchers enables the quick and easy production of super thin (50-150 microns) silicon sheets of all shapes and sizes without any wastage. The process, called Epilift, uses about 10% of the silicon required by traditional methods and therefore greatly reduces the cost of solar cells.

The Epilift process further reduces the cost of solar energy systems by producing wafers of silicon with properties that increase the efficiency of energy conversion.

Epilift silicon wafers have two important properties:

1. they are of optimal thickness for solar cells, and
2. they have a textured surface which is ideal for trapping light and preventing reflection.

How does it work?

The Epilift process is very similar in concept to the production of instant lawn. After the land is prepared, seed is sown and grass grows. When growth is complete the grass is carefully removed from the ground and transported for use elsewhere. The land is then ready for another growth cycle.

In the Epilift process a silicon wafer known as the substrate is equivalent to the ground in the instant grass example above.

1. The substrate is placed in a special solution containing small amounts of pure silicon and an extremely thin layer of silicon 'grows' on top.
2. The thin layer of silicon on top is then carefully removed for use in a solar cell.
3. The substrate is then ready for another growth cycle.

Further info, facts and fun

Solar cells convert light directly into electricity. When light strikes a thin slice of silicon it causes a movement of electrons. Solar cells have no moving parts to wear out and they produce no polluting waste products.

• A micron is one thousandth of a millimetre so at 50-150 microns, Epilift wafers are pretty slim!
• Dr Andrew Blakers has had many firsts in solar energy research. He has held four world records in solar cell efficiency since 1983.
• The Sydney Olympics Athlete's village is the world's largest ever solar village. The 655 solar house suburb generates enough power to meet its own needs.
• The amount of energy reaching Earth's surface in one hour is enough to satisfy the current world energy consumption! We just have to work out how to put it to use efficiently and cheaply.

For more info on great Australian Science check out:

CSIRO's Australia Advances http://www.csiro.au/promos/ozadvances
The Australian Academy of Science's Nova http://www.science.org.au/nova
The Australian Science Archive Project http://www.asap.unimelb.edu.au/

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