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Wattway de Colas

Wattway : the French solar road paving the way for clean energy

Innovations in construction very rarely spark the interest of the French population, with one recent exception. Conceived in France, and emerging as the first of its kind worldwide, the solar road is already making waves throughout the energy sector. The photovoltaic road (or parking lot) is the fruit of a 5-year joint research project between Colas – a subsidiary of the Bouygues road works group – and the National Institute of Solar Energy. Their combined effort has created Wattway: a road surface that comes in the form of photovoltaic tiles covered in a resistant resin. This strong tar promises to withstand the heavy traffic of trucks weighing around 13 tonnes per axel.

“In Chambéry and Grenoble, we successfully tested Wattway using one million vehicles-worth of traffic, and the surface didn’t move,” explained Hervé Le Bouc, the director of Colas, during the initial presentation for this new technology in October 2015. “All of Colas’s expertise –protected by two patents – has culminated in the creation of this clear coating, which is designed to protect the fragile photovoltaic cells.”

With Wattway there is no need to rip up and relay existing roads, as the tiles are easily installed over the original surface. Connectors then transfer the electricity produced from the tiles either directly to points of use – such as street lights or traffic lights – or to energy transport and storage systems.

According to estimates from the French Environment and Energy Management Agency (Ademe), four metres of Wattway road (or 20m²) are able to supply enough electricity to run a home, minus the heating. They also claim that 15m² can power the traffic lights at an intersection, and one kilometre of road can light up a town with 5,000 inhabitants.

There are already many possible applications of this technology, and we have yet to see what other interesting ideas lie in store. However, there are groups of sceptics that need convincing.

Firstly, there are the energy companies who doubt that the cost of energy production can rival that of conventional solar farms. Or then there are the road transport professionals, who have reservations about the resistance of the tiles. “In any case, Wattway is clearly not intended for heavy traffic as Colas only tested its tiles with a million truck crossings. On a motorway with heavy traffic at a rate of 80,000 vehicles per day including 15,000 trucks, the one-million mark is reached in less than three months,” remarks an expert. This would be a short life span indeed for the Wattway road.

“By 2018, we will have tested the different uses of Wattway with various partner clients from both the public and the private sector, across one hundred different application sites both in France and internationally. This includes thirty this year,” states Pascal Tebibel, director of strategic foresight at Colas. “The tests will be done under realistic conditions, covering areas ranging from 20 to 100m² (maximum).”

Following an announcement in June, the first of these tests is currently being conducted with the department of Vendée and will see the creation of a 50m² parking lot in a sports complex.

The energy generated will power a charging station for electric cars. The plan for the second test site has not yet been revealed.

The French Minister of Ecology, Ségolène Royal, is already steaming ahead with the plans. In January, Royal stated that she wanted to install 1,000km of solar roads within 5 years, before announcing in March that she wanted to make 5 million euros available for the project (although this has not yet materialised). Royal then visited the SNA factory in Tourouvre (Orne) on 26 July, which is where 5,000m² of tiles are being made for the application sites. If Wattway is still on the right track once the testing phase is over, “SNA has a production line capable of producing 150,000m²,” explains Pascal Tebibel. “In 2018, we can then move onto commercialisation.”

By Myriam Chauvot – Les Echos, France

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