CECS Spotlight: From cell to sell

An inexpensive solar technology has real potential to improve the pervasiveness of green power.

Two Australian colleagues on their way to a conference sit in a virtually empty carriage. At times they are animated, sometimes deep in thought.

It's ironic that the sun isn't shining on Professor Andrew Blakers and Dr Klaus Weber as they discuss, over the noise of the clattering train, an idea that could transform the world of solar panel research and development.

As the train pulls into Edinburgh, Blakers and Weber have an inkling they're onto something, but reservations persist.

They mull and deliberate, exhausting every avenue for pitfalls, as they make the hour-long hike to Arthur's Seat in Holyrood Park, which overlooks the historic city. From the top, Edinburgh is laid-out before them, and they can see miles into the countryside beyond the city.

It is a snapshot of city life that could pertain to any of the world's major metropolises - a hum of consumption powered by fossil fuels, non-renewable energy, surrounded by a natural environment too often taken for granted.

"I think at this point we were convinced that our idea was something that desperately needed to be looked at," Blakers says.

Although the concept of harnessing the energy of the sun's rays to provide power through solar technology is not new, mass production of solar panels has been dogged by the high cost of the raw material, hyperpure crystalline silicon.

"The big driver in solar panel research is to somehow reduce the cost of the silicon," Blakers says. "It's been very difficult to change the standard processing of the silicon wafers that are used in solar panels. We're stuck with a certain size."

Enter the idea that occurred to Blakers and Weber on the Scottish train - a way to processes the silicon more effectively, providing far more silicon surface area from a single wafer. Simple though this might seem, it was a total revolution of thought on producing a traditional solar panel.

"I think we knew from the beginning it was a good idea," Weber says. "Of course you get excited, but you have enough experience to realise that you'd better sleep on it.

"If you wake up the next morning still thinking 'Yep, this is a good idea', that's a great sign.

"Then you do a bit of homework and a few experiments before you realise it's the real thing. 90 per cent of ideas don't get there.

"But with the solar SLIVER cells it passed that stage easily. I guess then we progressed through different stages of emotion: guarded optimism, then quiet optimism and then excitement.

"As time goes by you get more excited - but that's a process that extends over many years and there are many hurdles you have to jump."

One of the first hurdles was going to their private sector research and development partner to convince them that they had an idea superior to another, different concept that had been already developed to the pre-commercialisation stage.?The new solar cells proved to have enough potential - and to be such a good idea - that the company, Origin Energy, took the concept on.

Creating commercially viable solar panels was always going to be a challenge, given the cost of raw materials and production, but with government support for solar research and schemes declining, commercial viability is paramount.

"When you buy a solar panel these days it will almost certainly be made of crystalline silicon wafers that have been processed into cells," Blakers says. "If you look at the cost of one of these modules, about half is the cost of the silicon wafers. Another quarter of the cost is turning the silicon wafers into solar cells and the fourth quarter is packaging those solar cells behind glass."

SLIVER cells use the crystalline silicon wafers more effectively. The wafer begins as a round disc that is about 1mm thick and 15cm in diameter. One thousand closely spaced long and narrow grooves are then made all the way through the wafer using a micromachining technique, but these grooves stop short of the edge of the wafer, so it remains intact.

The silicon wafer is processed and metallised to convert the narrow slivers of silicon between each of the grooves into solar cells, which are then cut out of the disc. Each of the SLIVER cells is rotated through 90 degrees to obtain area multiplication, thus producing a thousand thin sun absorbing cells, each 1mm wide, 100mm long and only 0.05mm thick.

Another member of the SLIVER cell team, Dr Vernie Everett, has devised an elegant solution to the problem of handling, mounting and interconnecting thousands of individual SLIVER cells to form a SLIVER module.

"The beauty of the SLIVER cell technology is that it is made in the volume of the wafer. This is a three-dimensional process rather than a two-dimensional process, as you would find in conventional solar cell processing. If you put all the bells and whistles on you get up to one square metre of solar panel out of one 15 centimetre silicon wafer," Blakers says. "That's an area multiplication of 60."

The individual SLIVER cells are about the width of a pine needle and as thick as a human hair. Like a pine needle they can be bent, and will break if bent too far. To form a working solar panel, they are placed just millimetres apart on a reflective back panel, covered with glass and electrically interconnected. When sunlight hits the solar panel, it is absorbed into the SLIVER cells either directly or, after hitting the reflective backing, is absorbed into their underside. The spacing and thickness of the SLIVER is varied to suit specific requirements. SLIVER modules can be partially transparent, flexible and bifacial (meaning that light can be absorbed from either side). There are many applications for SLIVER panels in architecture, Blakers maintains.

"If you look at solar panel power output in terms of hyperpure silicon consumption, for a state-of-the-art traditional solar panel you need about 10 kilograms of this expensive hyperpure silicon to generate one kilowatt of power," Blakers says. "A SLIVER panel requires less than one kilogram of silicon per kilowatt. In addition, there is a huge saving in wafer processing, because the number of wafers that need to be processed per kilowatt is reduced by up to sixty-fold with the SLIVER cell process. That's why we're so excited about it."

As well as using the silicon more effectively, the production of the SLIVER panels uses existing processes. This is important for getting into mass production quickly.

"There isn't any technique used in the production of the SLIVER cell technology that would be considered cutting edge," Weber says. "We often have to adapt each technique to suit our uses, but the important thing is it's standard technology, which means it's easy to procure and we can recruit people who are already experts in the technique."

Blakers pays tribute to the team that has produced the SLIVER cell technology at the ANU Centre for Sustainable Energy Systems. "We have a great team that has worked well together for many years."

Over the past year, the SLIVER has won a number of Australian and international awards - further testament to its potential to dominate the renewable technology market. By 2020, it is estimated that renewable energy technology sales will be worth $100 billion a year globally.

Blakers likes to compare it to the potential of the mobile telephone market in 1990. "If you've got the right technology, you become an Ericsson or Nokia," he says. "It's an exciting industry to be in and it's a once in a lifetime opportunity."?The team also believes in the SLIVER cell as an environmental and social product, in part because of its commercial appeal and its potential to democratise energy.

They believe that the latest generation cell has the potential to cost less than 10 cents per kilowatt hour. Comparatively, Canberra residents currently pay about 12 cents retail per kilowatt hour from traditional power sources.

It is essential that solar energy be this cost efficient to compete with other greenhouse-neutral technologies, including wind energy and carbon sequestration.

"If it pans out that this version of the technology really can be produced to cost less than 10 cents a kilowatt hour, suddenly you've got a cost-effective energy technology that uses an infinite resource in the sun, and provides a guaranteed energy supply in almost every country, particularly in equatorial poor countries, at a cost that's affordable," Blakers says.

"SLIVER technology has the potential to have a profound impact on energy policy and climate change policy worldwide."

According to Weber: "It's a social technology in that it works particularly well in rural and remote communities that get a lot of sunlight, and it allows individuals to look after their own energy needs, based on how much energy they consume.

"You know, we think every air conditioner should be powered by SLIVER panels, because of course when the sun is blazing hot outside the panel's working really well. It's a perfect match."

Equally, the panels for individual homes are placed on roofs, making effective use of space, and any large panel arrays would be best set up in arid regions, such as central Australia, where there is land to spare.

"You wouldn't need much land to provide all of Sydney's power," Blakers says. If 50 per cent of the world's electricity was provided by solar technology in 2050, it would only require 0.2 per cent of the world's land surface area to generate, he says.

In areas like Tasmania, or Scotland, where sunlight hours can be brief, the researchers say solar power will always work in tandem with other renewable energy, such as wind power, to cope with demand fluctuations.

So although Edinburgh may not be best suited to solar technology, it will always be the birthplace of a very bright idea.