Back in December 2016, France opened what it says was the world’s first road to be covered with a surface of solar panels.
Set along a one-kilometre route in the small village of Tourouvre-au-Perch, the road was to be used by around 2,000 motorists per day over a two-year test period to establish whether it can generate enough energy to power street lighting in the village of 3,400 residents.
When opening the road in 2016, France’s ecology minister Ségolène Royal set a goal of installing solar panel in one of every 1,000 kilometres of highway throughout France over five years.
Whilst France was the first country to apply solar to roads, the project followed the 2014 opening of the world’s first solar bicycle path, with a 70-metre stretch of path containing solar panels in the town of Kormmenie in the Netherlands. The path consists of rows of crystalline solar cells which were encased within concrete and covered with a translucent layer of tempered glass. A non-adhesive finish and a slight tilt are meant to help the rain wash off dirt and thus keep the surface clean, guaranteeing maximum exposure to sunlight.
France and the Netherlands are not alone in pursuing solar highways. Last December, China opened its first solar roadway – a one-kilometre highway in Jinun, the capital of the north-eastern Shangdong province which it claims will generate one million kilowatts of electricity per year that will be used to power street lights and a road snow melting system.
In England, engineers from Lancaster University are working on smart materials which they say can be embedded into road surfaces in order to harvest and convert vehicle vibration into electrical energy. The researchers hope to design and optimise road systems which can recover around one to two megawatts per kilometre under normal traffic volumes of 2,000 to 3,000 car per hour – enough to power between 2,000 and 4,000 street lamps.
Professor Mahame Saafi, who is leading the research, says the new materials will take advantage of the piezoelectric effect where passing vehicles cause stress on the road surface, producing voltage. The system developed will convert mechanical energy into electric energy to power street lamps, traffic lights and electric car charging points.
The materials will need to withstand high strengths and provide a sensible balance between the amount of energy they produce and their cost.
Moreover, the French based company behind the solar road in France – asphalt maker Colas Group – is looking to expand the technology internationally. It is scouting for 100 test sites around the world as part of their objective of paving 1,00 kilometres of roadway with 1.26 square metre solar panels the company has developed with the French National Solar Energy Institute which it says can provide as much as 116 watts of energy at peak efficiency.
So, should Australia go down this path?
One broad fan of the concept is science personality Karl Kruszelnicki (known commonly as Dr Karl), who has thought about the subject for 25 years and feels it could be used to comprise a ‘small portion’ of Australia’s renewable energy. Dr Karl has previously described the notion of solar roads to media outlets such as News Corporation as an ‘attractive looking idea’.
He says an advantage about solar roads is that the road space is not otherwise used (other than for vehicles) and thus placing solar cells there does not encounter opposition from vested interests.
Dr Andrew Thompson, a researcher at the Energy Climate Change Institute at Australian National University disagrees. Thompson acknowledges that the idea is technically feasible but says it makes little sense economically.
As recycled waste from the petrochemical industry, Thompson says that base has been developed over thousands of years and is cheap, technically sound and environmentally friendly. Installing solar roads would mean putting complicated electronic circuitry under the road base. This would be extraordinarily costly, he said. In addition, it would create infrastructure management problems whereby performing work on say, an underground pipe, would mean cutting into the solar panel.
Despite not being feasible economically, Thompson says putting some solar panels on roads could yield valuable lessons which can be applied elsewhere such as in solar technology more generally. Nevertheless, he says the idea of solving energy generation problems through solar roads is not economically viable.
“It’s definitely technically feasible but economically it is absolute garbage,” Thompson said. “It shouldn’t even be on the radar as far as a serious solution for energy generation.”
According to News Corporation, building roads out of toughened glass typically costs around four to five times as much as typical roads made of asphalt or bitumen. Whilst the Dutch cycle path did produce 3,000 kilowatts of energy, the cost of building the path could have paid for 520,000 kWh, a report in The Guardian said.
That said, the aforementioned researchers in the United Kingdom believe the cost of installing and operating their road harvesting technology would equate to only around 20 per cent of the cost associated with running the 2,000 to 4,000 street lamps they hope to power through their project using conventional means.
Apart from cost, many roads in urban areas are fully or partially shaded by trees and buildings – not to mention cars which drive over them. This reduces the volume of power produced.
There are also safety issues. Whilst solar glass will be made with surface topology to increase traction, concerns remain over what happens as this eventually wears.
Putting solar cells on roads is a concept being tried in various countries.
Any widespread adoption in Australia, it seems, is a long way off.