Harnessing roads to gather sunlight for power generation is not a pipe dream. In the Netherlands, a cycle lane has been gathering energy since late 2014. The consortium running the SolaRoad pilot test says results go beyond expectations and it is in talks about expansions. Meanwhile, the French government has announced plans to pave 1000km of road with photovoltaic panels in the next five years, supplying power to millions of people.
‘We want to make this business ready by 2018,’ explains Pascal Tebibel, director of strategic foresight at Colas, which unveiled its Wattway panels in October 2015 in France. Its energy harvesting technology is glued onto the surface of pavements, road structures or central meridians as 7mm-thick strips, he explains. ‘This is a multi-layer strip of polymer, with multiple layers, in which solar cells are embedded. It is translucent, which allows light to pass through, and solid enough to withstand any type of traffic.’
The Dutch technology sees solar panels integrated into a structure with a concrete base and a glass top, coated with plastic. The 2.5 by 3.5m modules are tilted to allow rain to wash off dirt and grime.
‘The energy output during the first year was 9,800kWh, which is enough to power three Dutch households, with just 70m of bike lane,’ says SolaRoad spokesperson, Sten de Wit. The consortium is now trying to select the best solar cells from an economic perspective, and de Wit says the roads are being designed so that the extra purchase cost is paid back within 15 years.
‘We are in negotiations with a number of local and regional governments about a follow-up project, involving bicycle roads, regular roads or bus lanes, and we are talking with the state of California about a pilot there,’ says de Wit.
‘The overall cost of the electric power generated would be approximately 100 times larger than commercial rates,’ says Don MacElroy, a chemical engineer at University College Dublin, Ireland, speaking about the Dutch cycle lane, which cost Euros3m. In the French example, given the area proposed, average incident radiation and a module efficiency of 15%, he calculates just 1-2% of total electric power requirements of France would be generated, at a capital cost of 100s of billions, based on the Dutch experiment.
In the UK and Ireland, he says ‘PV in roads is a non-runner. It would be a very costly and, I believe, wasteful exercise’.
Photovoltaics professor Alistair Spoul at University of New South Wales, Australia, concurs: ‘[It] seems like a very expensive way to do solar, in comparison to putting it on people’s rooftops.’