France’s minister of ecology and energy, Ségolène Royal, recently announced the country’s intention to, over the next five years, pave 1000 km of roads with a composite material that can adapt to thermal expansion in road surfaces. This will mark the first time roads will be able to produce electricity while preserving their full capacity to bear vehicle traffic. It is considered a major technological breakthrough and a building block for cutting-edge projects involving intelligent roads and “Smart Cities.”
The material, known as Wattway, was developed by French infrastructure specialist Colas in partnership with the French National Solar Energy Institute. Back in October 2015, at the World Efficiency Congress in Paris, Colas unveiled Wattway panels. As Colas explains on its website, each Wattway panel contains 15-centimeter-wide (approx. 6 inches) cells making up a very thin layer of polycrystalline silicon that transforms solar energy into electricity. These photovoltaic (meaning able to convert solar energy into electricity) cells are coated in a multilayer substrate composed of various resins and polymers.
The substrate is translucent enough to allow sunlight to pass through, but also resistant enough to withstand truck traffic. The composite “sandwich” is also designed to adapt to the pavement’s natural thermal expansion. The surface of the panel that is in contact with a vehicle’s tires is tailor-made to ensure equal skid resistance compared to traditional asphalt roads.
Unlike other solar road solutions from the past, Wattway solar panels are installed directly on the pavement, without any additional civil engineering work.
“A mere 20 m² of Wattway can produce enough electricity to supply a single household (not including heating),” said Colas in a press release from October. “This cutting-edge solar technology will provide renewable energy as close as possible to where electricity consumption is the highest and demand is constantly increasing.”
An American company, Strongwell, based in Bristol, Va., has also created panels, which, while not used in a translucent application, also generate electricity. The technology, Strongwell’s pultruded fiberglass DURAGRID HD-4000 2.5” grating panels, served as a trench cover at the Utah State University Electric Vehicle and Roadway research facility. The project, which won an ACE award at CAMX, displayed the benefits of FRP – including light weight, high strength, nonconductivity and no electromagnetic interference.