The prototype PERL cells could help solar become a
real competitor against coal power in Australia.
Image: iStockphoto

When it comes to harnessing the sun’s energy, Australian scientists have been the best in the world for years. But a change in the way solar cells are rated has just widened the gap from the rest of the field. Thanks to a new standard of assessment, a prototype PERL cell developed at the University of New South Wales (UNSW) ARC Photovoltaic Centre of Excellence has been pushed from 24.7 per cent efficiency to 25 per cent over night. This world-beating figure is the closest ever achieved to harnessing the theoretical maximum of 29 per cent of the sun’s power. By comparison, the next best is Germany’s effort with 23.5 per cent.

The real value of having more efficient cells in solar panels is that you get more electricity for your dollar. Currently you would need panels to cover approximately 25m² to run an average sized house with a five star energy rating - a feat that would cost around $37,500. By using photovoltaic panels made with PERL cells you could power the same house with roughly 17m² of roof and, depending on the cost of production, for about $10,000 less.

Strangely enough this breakthrough occurred without having to alter the cells at all. It’s actually the sunshine that solar panels convert into energy that has changed (or, rather, the definition of it) - and it’s about time. The last spectrum was classified in 1982 and our understanding of the composition of light has significantly advanced since then. Under the newly established definition, light now includes more energy in the extreme red and blue ends of the spectrum and less in the middle green section.

Fortunately the UNSW team, led by NSW Scientist of the Year Professor Martin Green and Professor Stuart Wenham, had already created a cell that trapped all of those aspects of sunlight. “With the redefinition, some of the features that we’ve incorporated in our cell really come to the fore,” said Professor Green.

As you read this, the group are already working on installing their world-first technology into solar panels. A standard photovoltaic cell on the market has around 17 or 18 per cent efficiency, but it won’t be long before we’ll see panels whose cells crack the 20 per cent mark, according to Professor Green. “As we find better and cheaper ways to incorporate some of the improvements into commercial sequences, we’ll see the gap between the best lab cells and commercial cells narrow down”.

The recalibration of the spectrum has also made UNSW’s cells act as if they’re thicker than they really are, allowing Professor Green’s group to develop silicon-on-glass solar cells that are over 100 times thinner.

But what happens during the winter nights where sunlight isn't as abundant? “The main way of storing electricity on a large scale is to pump water uphill when you have excess and, when you don’t have enough, letting it run downhill through a hydro plant to retrieve the energy,” said Professor Green. Large scale storage methods such as this are quite beneficial now that most of Australia has some form of feed-in tariff scheme in place. That is, electricity suppliers actually pay you for any excess energy your roof produces. Green believes this is the catalyst colar power needs to become a real competitor against coal power in Australia. If it can end our dependency on fossil fuels and earn us money, then it's a furture worth looking forward to.