The French government has announced plans to pave 1000 km of roads with emerging solar panel technology, heralded as particularly innovative for its ability to be directly installed into the existing pavement.
Created by French transport infrastructure company Colas in collaboration with the French National Solar Energy Institute, each panel in the Wattway system contains 15cm-wide cells making up a 7mm-thick film of polycrystalline silicon that transforms solar energy into electricity.
These fragile photovoltaic cells are coated in a multilayer substrate composed of resins and polymers. The manufacturer claims this substrate is translucent enough to allow sunlight to pass through, and resistant enough to withstand truck traffic.
On the Wattway website, Colas says the technology is also designed to adapt to the pavement’s natural thermal expansion, making it proof against increases in temperature. The surface that is in contact with vehicle tires is treated to ensure skid-resistance, which Colas claims is equivalent to conventional asphalt mixes.
The electrical system is designed to ensure that the entire system does not short circuit if one cell is down. Electrical connections can be hooked up on the side of traffic lanes, in gutters or in ducts integrated in the panels themselves.
Minister of ecology and energy, Ségolène Royal, announced France’s intentions to rollout the technology during a recent press conference.
The technology does have some drawbacks. As it stands, the installation time for the technology is hampered by the need for it to be installed by hand, although Colas says an automated installation system is scheduled for launch in 2016. 
In addition, the performance of Wattway solar panels is less impressive than that of conventional models, with Wattway claiming a 15% energy yield, compared to 18-19% yield.
The photovoltaic panels are expected to move into industrial-scale production in the very near future. While Colas does not spell out the precise cost of installing the Wattway, its website explains:
“Wattway’s price per m2 is to be seen in light of the production cost of electricity. Photovoltaic energy is measured in watt-peak, which takes into account sunlight conditions. Today, depending on the technology used and the support on which the panels are installed, prices fluctuate between 2 to 8 euros/watt-peak. The cost with Wattway is estimated at 6 euros/watt-peak.”
The solar road concept is based on the assumption that roads are only occupied by vehicles 10% of the time. Colas suggests areas such as stadium car parks, large spaces which often stand empty, would also be ideal sites for the technology. 
The company website claims that 20 m2 of Wattway panels can supply the electricity requirements of a single home.
It also explains the technology has applications for:
- Street lights: 1,000 linear meters of Wattway pavement can supply a town of 5,000 inhabitants;
- Traffic lights, variable message panels, etc: 15 m2 of Wattway panels can provide electricity to all the traffic lights at an intersection; and
- Charging stationary electric vehicles via induction: 100 m2 of Wattway panels can provide enough power for an electric car to travel 100,000 km.
However, possibly the most intriguing applications for Wattway would be within a ‘Smart City’ environment. Colas suggests the technology could assist with real-time traffic management, self-driving cars and charging moving electrical vehicles.
There is yet to be any indication of which roadways will be covered with Wattway, or exactly how much the project will cost.
For more information, visit the Wattway website.