Solar guru receives Australia Day honour

www.abc.net.au
26 Jan 2012

Australia needs to look to Germany if it is to realise the potential of solar cell technology, says an expert who is being honoured today. Professor Martin Green of the University of New South Wales has been made a Member of the Order of Australia (AM) for his work on photovoltaics. "Germany has been the only country that's had a sensible long-term program in place to promote the use of renewables", says Green.

Some argue solar cells are not a competitive option for reducing carbon emissions, and are limited by the fact that they don't generate energy unless the Sun is shining. But according to Green, the "stars are aligning for conventional roof mounted solar" and it is ripe for a new kick start from governments.

Cheaper technology
Green says the cost of solar cells has come down rapidly in recent years largely due to the expanding manufacturing industry in China. "They're now a third to a quarter of the costs of only a couple of years ago", he says. "It's expected that this [decline in price] will continue over the next decade. The projections are that about 60% further will be taken off the costs over that period".

The German experience Green says the advantage of solar cells is they produce most of their energy in the day when energy use is at its highest. While clouds can cut back solar power production, this can be compensated for by energy from other areas that are sunny-as long as the grid covers a large enough geographic area, he says. Green points to data from Germany where nearly one million (mainly rooftop) solar panels supply the equivalent of a dozen nuclear power plants, or about 40% of the maximum demand in Australia. "When you average across the whole country you get a very predictable daily output", he says.

Balancing generation and use
Green says matching the generation of energy with its use is an old issue that the grid has found ways of accommodating. "You just slightly change perspective when you are generating most of your power during the day time [as you would with a system involving photovoltaics]", he says. Green says current day coal and nuclear power stations push out energy all night, when it's not particularly needed. As a result there is a need to store excess energy produced at night or for incentives to encourage energy use during this time.

"We give away electricity to aluminium smelters at night just to provide a load for the power plants at night", says Green. He says in countries like Japan, Germany and the US, excess energy from conventional power plants is currently used to pump water uphill at night for hydroelectricity. Generation of excess energy from photovoltaic cells during the day could be dealt with in a similar way, says Green. Local storage of energy from photovoltaics in batteries is also starting to occur, he says.

Feed-in tariffs
Green says Australian state-based schemes to promote rooftop solar have been undermined by fixed feed-in tariffs. Instead, a sliding tariff scale of the kind used in Germany, which progressively reduces subsidies to solar power and drives down the cost of solar panels, is more sustainable. "The German scheme has been undoubtedly successful", says Green.

"It has single-handedly driven the world market for both wind and solar products and changed the industry from non-viable to the state it is now where it has the chance of being self-sustaining". He says a carbon tax in Australia will only encourage lowest-cost present day low-emission alternatives. The tax should be complemented by German-style schemes to boost photovoltaics, which are presently at a low stage of development but have the potential to lower costs in the future.

Efficiency and sustainability
Green's research team currently holds the record for highly efficient solar cell technology, which has been commercialised through CSG Solar Pty Ltd, of which he is research director. Green says current silicon cells show 25% efficiency in the lab, although commercially available panels operate at just 14 to 15%. His team is working with several companies to improve this efficiency.

He says the thermodynamic limit of converting sunlight into electricity is 74%, and at this point, the best lab device reaches 36% using cells made from exotic materials. Green says the energy being used to make solar cells is also reducing. "Everything that is being done to reduce the cost of the cells also reduces the energy content", he says.

And he says the industry is moving away from the use of toxic chemicals that require expensive disposal, with pollution from solar cell production becoming the exception. "Of the hundreds of manufacturers in China there have been two of them in the last five years that have been found to be not disposing of the wastes of the processing of the silicon for the cells in an acceptable way".