French civil engineering firm Colas is identifying potential UK sites to test its Wattway photovoltaic road surface. Designed to be installed on top of an existing road, the solar panels generate electricity.

"The UK trials will form part of about 100 trials taking place worldwide,” says Carl Fergusson, Colas' executive director of strategy and development.

The panels are affixed to the road using a resin. Image credit: Joachim Bertrand/COLAS.Designed and tested to endure vehicles passing over their surface, the 7mm-thick panels are affixed to the road using a high-performance resin. A glass bead resin coating is then applied atop the panels to provide frictional and skid-resistance performance equivalent to conventional asphalt mixes without significantly affecting the solar panels' efficiency. The watertight composite “sandwich” is designed to adapt to the pavement’s natural thermal expansion.

Each solar panel comprises an array of 15cm-wide cells composed of a thin film of polycrystalline silicon that transforms solar energy into electricity. These fragile photovoltaic cells are coated in a multilayer substrate made of resins and polymers that are sufficiently translucent to allow sunlight to pass through and resistant enough to withstand large-vehicle traffic.

Electrical connections can be installed at the edge of the roadway or in ducts integrated in the panels themselves. Electronic circuit breakers are designed to ensure safety.

The power generated by Wattway has the potential to be used for highways and transportation infrastructure, such as variable-message signs and street lights. Equally, it can be returned to the grid or used to supply energy to nearby homes and businesses.