January 08, 1991

Article at Reuters

Powerful new solar cells may make sun-power cheaper than coal

Dr Richard Corkish (left) and Prof Martin Green (middle) with Chinese Minister of Science and Technology Wan Gang in the UNSW laboratory where the solar cells are fabricated

By Wilson da Silva

SYDNEY – Scientists in sun-drenched Australia are improving the efficiency of solar cells, offering hope solar power will be cheaper than coal-fired electricity within a few years.

Researchers at the University of New South Wales (UNSW) in Sydney are perfecting techniques using lasers to make solar cells with the world’s highest efficiency.

 “We’re aiming to reduce solar power production costs to about half the level of coal-fired plants, and we think this is achievable in the next 10 years. There are certainly no technical impediments,” said Professor Martin Green, group leader at UNSW’s Centre for Photovoltaic Devices and Systems.

Unlike coal-fired power, solar energy does not pollute the air or contribute to global warming. Solar collectors have no moving parts and produce power continuously for 30 years before needing maintenance. Excess solar energy can be stored in batteries for use at night or on cloudy days.

But solar power has remained largely untapped because it is significantly more expensive than coal or hydroelectric power.

Photovoltaic cells use the sun’s energy to dislodge electrons from atoms of silicon or other materials. The electron, with a negative charge, and the atom that released it with a positive charge, migrate to separate terminals, generating an electric current.

UNSW scientists say their cells have the world’s highest efficiency – the ratio of the energy deposited as sunlight to the electricity produced – at 24.2 per cent, 40 per cent better than existing cells.

Scientists in the United States and Japan have recorded slightly higher efficiencies, but these were attained with concentrated, not natural, light and were not independently confirmed, they said.

Ian Lowe, Griffith University scientist and former member of Australia’s National Energy Research Council, said the UNSW cells would almost halve the cost of producing solar power.

Existing cells generate power for between 20 and 40 U.S. cents per kilowatt hour, about the same as diesel generators, he said.

UNSW scientists believe they can eventually boost their efficiency to 26 per cent, or nearer to what is considered the theoretical limit of 30 per cent. This would cut costs to around five U.S. cents per kilowatt hour.

If so, solar power would be a viable alternative to existing energy sources, allowing utilities to lessen their reliance on oil as a source of power, Lowe said. “Oil is a very dodgy basket to put all of your eggs in,” he said.

UNSW scientists are boosting their cell’s effiency by using lasers to remove defects that impede the flow of sunlight into the electric contacts.

The cells are composed of tiny crystalline pyramids that capture and direct light energy into contact leads. The concept was invented at UNSW and is now used by researchers worldwide.

The experimental cells, dubbed PERL – short for passivated emitter, rear locally-diffused – are still cumbersome to make.

The researchers are working to reduce the cost of the silicon wafer on which the cell is mounted, which represents most of its cost.

Production engineering may be as important as cell efficiency. Not until cell manufacturing becomes automated and efficiencies of scale achieved will solar cells become commercially viable on a wide scale, industry analysts say.

Group leader Green believes his team will streamline the process and make it easier for mass production. Cells would then be as affordable as the glass that coats them, making solar power cheaper than energy from coal-fired plants.

An early generation of cells made with laser grooves has efficiency of around 20 per cent. They are being made under licence by by AEG Telefunken AG of Germany and British Petroleum Co Plc.

These cells were a boon for solar power since they could be connected to existing solar arrays and deliver more power for the same cost and same amount of area exposed to sunlight, said research engineer Mike Willison. “They will deliver double the bang for the same amount of bucks,” he said.

They also were used to power the Spirit of Biel, the Swiss solar-powered car that last year won the solar car race from Darwin through the Australian outback to Adelaide.

UNSW is also working with the New South Wales Department of Minerals and Energy to develop a “solar farm” that would feed sun-power into a city’s electricity grid in peak periods. The university has been studying solar cell manufacture since 1976.