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Monday, September 3, 2007

Sunburnt land has plenty of energy in store

Sunburnt land has plenty of energy in store

IN the 1970s, Australia was leading the world on developing solar technologies. It was driven out of practical necessity rather than some particular vision for a clean energy future.

Back then, organisations such as Telecom and Australian National Railways needed to supply electricity to signal points, phone boxes and other remote infrastructure.

In many cases solar was the cheapest and most efficient means, pioneering Australian technology development ahead of the world.

Australia is still a sunburned country with some of the best solar assets in the world.

In 2004, a federal Government energy futures white paper identified three low-emission energy technologies for which Australia had the potential to exploit a comparative advantage: carbon capture and storage, geothermal and solar.

Solar energy has been idolised for decades as being the perfect energy source: abundant, clean, quiet and still. It does have an annoying habit of switching off at night, but all energy can be stored. For instance solar electricity could be used to pump water up hill and released to run turbines at night.

The real constraint is cost.

Just as fossil fuels such as coal and oil are cheap because they are highly dense forms of energy, solar is more expensive because it is more diffuse and the race is on to capture this energy more efficiently and to bring the cost of the technology down to where it can compete with other supply sources.

Best known are the heavily subsidised black photovoltaic cells found on house rooftops that act like mini-peak load power stations, augmenting household demand during the day, when demand is greatest.

Pioneered at the University of NSW, the cells are very simple technology: the sun's rays hit thin slices of silicon creating an electrical current that is captured by integrated circuits and delivered as electricity.

BP Solar bought out Australian manufacturers Solarex and Tideland and it now manufactures panels at Homebush in Sydney for the domestic and Asian markets, competing with imports mainly from Japan and Germany.

Typical silicon cells can convert about 15 per cent of solar energy into electricity, and purer silicon achieves higher efficiencies but at a higher cost.

World prices for solar-grade silicon have been pushed up with strong global demand and competition with the microchip industry, which uses the same material. Although spot prices have reached up to $300/kg, prices are expected to ease as supply increases in the next year.

The silicon accounts for about half the cost of a photovoltaic solar panel but cell manufacturers have been driving down cost by slicing the silicon thinner.

BP Solar uses cells of about 200 microns thick, butsome technologies in Europe have got this down to 140.

Applying technology developed by the Australian National University, Origin Energy has a $20 million pilot plant in Adelaide that is trying to commercialise sliver-cell technology.

Silicon cells are cut sideways to produce flexible and very thin slivers of about 50 microns thick, allowing more light to hit the silicon when installed, thereby increasing its operating efficiency, but so far about a third of the silicon is wasted in the cutting process.

Dyesol, a publicly listed company at Goulburn in NSW, is developing lower-cost technology using dye and pigment, instead of silicon, to create a weaker electrical current when hit by sunlight.

Described by the company as artificial photosynthesis, the technology is less energy intensive in manufacturing and, because of its lower cost, can be embedded directly into building materials.

It will be more competitive if silicon prices remain high or as it drives costs down and efficiencies up.

Solar is also being developed to replicate large-scale electricity from power stations and Melbourne company Solar Systems received a $75 million grant from the federal Government last September to build a 154MW solar power station near Mildura in north-west Victoria. The plant would be about one-sixth the size of a typical coal fired power plant.

Solar Systems plans on installing more expensive but more efficient Gallium Arsenide photovoltaic cells, but plans on squeezing more energy out of them by installing them on high towers and surrounding them with almost 20,000 angled mirrors called heliostats.

These will track the sun through the day, concentrating solar energy 500 times stronger on to the high-performance cells, but will need sophisticated cooling technology to keep the cells operating efficiently. An aspirational goal for the technology is to deliver electricity at about $50/mW-hour in the same range as natural gas.

Cloud cover reduces the efficiency of photovoltaic cells by 90 per cent and is even lower for concentrated solar, making location crucial to keep efficiency up and costs down.

Adelaide company Green and Gold Energy also has developed a solar concentrator technology called Sun Cube, which uses Fresnel lenses, found in car headlights, to concentrate sunlight on to high-efficiency cells.

The company has just placed an order for $24million worth of cells to build solar farms by 2009, manufacturing of the units to be completed in China.

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