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| Solar panels with skid resistance: energy-producing tiles that can be laid on roads. Photo: Colas |
According to the global supplier of bitumen and other surface materials, the world's millions of kilometres of roads are empty for as much as 90 per cent of each day, providing a big opportunity to generate solar-powered electricity.
For the past decade, the company has been working with the French National Solar Energy Institute to develop solar panels that are sufficiently resilient and efficient in gathering those rays to warrant the cost of paving roads with them.
The result of those efforts is a solar tile – thinner than a dollar coin and measuring 1.26 square metres – that can provide as much as 116 watts at peak efficiency. 'Wattway' solar road: Built using photovoltaic cells, a promotional video by the company Colas shows the workings of their 'Wattway' solar road.
The developers are aiming to roll out 1000 kilometres of solar roads within five years and are scouting for 100 test sites around the world.
Adelaide and parts of Queensland have indicated an interest in participating and western Sydney could be next, said Azeem Retmullah, Sydney-based general manager for Colas subsidiary SAMI Bitumen Technologies.
Just 20 square metres of the product laid on existing roads can supply enough electricity for a typical home, and 1 km could support about 5000 people, Mr Retmullah said.
The technical challenges are among the reasons why development efforts have taken a decade.
"The fragile photovoltaic cells that you have in the panels are
actually encapsulated in polymers and resins, so they are well
protected," Mr Retmullah said.The tiles must withstand heavy vehicles, and many of them. According to Colas, the product it has dubbed Wattway has been tested to withstand at least 1 million truck tyre passes.
It expects the tiles to have the durability of the pavement it covers. Panels laid in car parks or other lightly used tarmac sites could be expected to last as long as 20 years – not far shy of a rooftop system – while those of heavy-trafficked roads might last only as half as long, Colas claims.
Home driveways are another option.
Mr Retmullah said resins used to protect the panels are "reasonably translucent" even when topped with crushed glass or other materials to give them "skid resistance" comparable to standard bitumen roads.
The company estimates panel efficiency is about 15 per cent, not that far off the 18-19 per cent for conventional solar panels.
Just as roads generally "self-clean" as rain washes off dirt and oil, the panels would be kept relatively clear of sun-blocking materials, he said. They may even reduce potholes.
Costs, of course, may prove the biggest road block to their rollout.
Colas doesn't provide a production price per tile, saying only that the target is to deliver €6 ($8.70) per watt peak capacity. If the technology followed the curve of solar PV panels, dropping by 90 per cent over 20 years, "Wattway should become a competitive solution within a decade".
Richard Corkish, chief operating officer at the Australian Centre for Advanced Photovoltaics based at the University of NSW, is sceptical.
Solar roads "are an idea that's been around for some time," Dr Corkish said. "I worry about the amount of stuff you need to get into [each panel] to make it tough enough to take a B-double."
City roads might also be shaded by trees or buildings for much of the day and while rural roads might have a clearer run at the sun, the market for the electricity will be smaller.
"People can get excited by things that are long shots. We're not picking the low-hanging fruit," he said, noting how many large commercial sites are yet to adopt solar PV.
Michael Caltabiano, chief executive of the Australian Asphalt Pavement Association, said western Sydney was an ideal location to test the product, given its proximity to industry and a huge market.
Mr Caltabiano, a former director-general of the Queensland department of Transport and Main Roads, expects few planning issues for the tiles.
"To put solar panels on a road is not a regulatory problem," he said. "It's the willingness of governments to give it a go."
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