Shadow over solar power removed

Canberra Times
Wednesday 24/9/2008 Page: 5

Researchers at Australian National University have devised a new technology that stops moving shadows "cannibalising" solar cells and eating into generated energy. But the breakthrough technology - which could cut the cost of solar energy by half - will be commercialised and manufactured offshore in the United States and China. Although it could cut the cost of solar energy for many Australian households, it may be years before the new system is available here.

The technology marks another world first for Professor Andrew Blakers and the ANU sustainable energy systems team that developed solar sliver-cell technology. As their name suggests, sliver cells are wafer-thin cells which dramatically cut the size and cost of photovoltaic panels by using less silicon to generate energy.

Professor Blakers said, "Moving shadows can be a serious problem with systems that use solar concentrator cells. If a shadow from a stick, a leaf or a bit of bird poop falls across one cell in a string of cells, it can reduce the energy generated by that string of cells to zero." The electricity voltage bands run along the string of cells, with the level of energy produced "set by the worst- or lowest-performing cell in the string."

If a shadow falls across one cell, others "can gang up on it", with the result being an expensive - and potentially dangerous - rooftop solar system blow-out. "You'd get a red glow, you'd see a puff of stroke coming out and you'd have to replace that whole string of cells." Improved shadow tolerance has been one of the holy grails of international solar research and the global solar market, and the ANU research team has already attracted interest - and financial support - from the US and China for its breakthrough technology.

The ANU system, described by Professor Blakers as "a simple but incredibly useful piece of technology", can maintain power even when shadows fall across a number of solar cells. The ANU has teamed tip with scientists from China's Tianjin University - which has the country's biggest engineering faculty - and Chromastui, a start-up company from California - to develop new and cheaper roof-mounted solar trough concentrator systems.

The Federal Government has contributed $1.8 million to the joint venture under its Asia-Pacific Partnership scheme to promote cleaner climate-adapted technology. A test array of eight solar concentrator troughs was installed on the roof of Bruce Hall at the ANU in 2005. The troughs are like long, curved mirrors that focus the sun's rays on to photovoltaic cells, producing solar electricity, hot water and air conditioning.

The new, smaller and cheaper, shadow-tolerant rooftop solar system will be manufactured in California and either China or India. The aim is to make solar energy more affordable and the system could eventually sell for under $1000 - but, according to Professor Blakers, not in Australia where the uptake of solar photovoltaic systems to date is "less than 1 per cent of the photovoltaics that went into Germany last year".