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Imagine that streets and roads were producing solar power. That’s Colas’ challenge: building solar-energy producing roads, a world must-haveMYRIAM CHAUVOT / JOURNALIST
"Les Échos" Oct. 13th, 2015
The road surface is composed of photovoltaic cells covered with a transparent alloy in order to resist trucks passages-- © Joachim Bertrand / COLAS
Colas, Bouygues’ road subsidiary, has designed a road coating composed of solar cells for roads and car parks. If a 2,5% rate of all road surfaces were thus covered in France, a 10% part of the country's energy needs would be met.
The "Autoroute du Soleil" is widely known in France as the holidays’ highway leading to French Riviera, but who has ever dreamt of a solar road ? (or a solar car park). That would be a real power station through the simple exposition of its coating to sun. Colas, the road works subsidiary of Bouygues, launched this newly-designed road, known as « Wattway » officially on Tuesday. Presently stepping in industrialisation scale, the coating composed of solar cells will be available from next January, after five years of research led jointly with the National Institute for Solar Energy (Ines, French acronym).
"No need to rebuild infrastructures", said Hervé Le Bouc, Colas CEO. "It’s a road coating sold in the form of concrete slabs which will cover roads or car parks". These slabs are sticked to the existing road and consist in a classic photovoltaic cell, long of 15 cm and covered with a resin substrate able to bear vehicles traffic, even trucks. That’s a kind of multi-layered structure, waterproof and designed to meet the same characteristics of abrasion and slickery as usual road coatings. " In Chambéry and Grenoble, we have successfully tested Wattway in a cycle of one million of vehicles, namely twenty years of usual traffic experienced on a road, and the coating has not changed an inch", said Hervé Le Bouc. " That’s pretty good ", he insisted, "as solar panels are highly breakable and would have crushed together. That’s the result of Colas’ know-how and the core of it is the nature of the coating which protects these panels ".
The test area is linked through a subterranean connection to a system retrieving the energy produced by these panels exposed to sun. « Then some inverters send back the energy in ERDF grid. Either households may be fed thus directly by being plugged in the grid ".
A one-kilometer long road may provide light to a 5,000 inhabitants city.
The industrial applications of such know-how are multiple : for instance for public light, providing power for illuminated easy-to-read displays of bus stops or traffic lights in urban fields, either power needs of houses in low-density populated areas. The Wattway slabs present an energy efficiency close to that of solar panels in solar farms and have been tested by three companies with success, particularly in car park entrances. According to an ADEME assessment, 4 linear meters of road (namely 20 m2) would cover a household energy demand (heating excluded), 15m2 would feed crossroad traffic lights and a whole kilometer would provide light to a 5,000 inhabitants towns. Wattway would reload electric cars by induction : 100m2 would provide energy to make 100,000 km yearly, according to INES.
" If a quarter of all roads were covered, we would provide all France’s energy needs", Hervé Le Bouc said. "If only 2,5% of all surfaces were covered with this road coating, we would meet at least 10% of all demand. That’s what this project is worth for ". Wattway will develop further in the next three or four years. " First, we offer to some customers to equip small surfaces : such as shopping centres car parks or parts of roads, like some 100 meters lengths, in order to test the product in real conditions. By four years, following a cruise development, we will be able to equip lengths of several kilometers".
President Hollande’s visit.
Following President Hollande’s visit in the third tester’s premises in late August, " we received many phone calls from towns, bus lines managers, who expressed interest in this coating, in order to provide power for bus stops, or from mass distribution managers for their car parks. We will start marketing the product through 1,000 agencies located in 50 countries. By late June, we intend to end up the training of one marketer by agency. Then we will start marketing the coating in our 400 French agencies, which will sell Wattway in early January. We will start to export only in a second stage, to start with North America. But other countries, such as Denmark, have shown a strong interest in this new technology".
What about the cost ? «"We will charge the same rate as that of solar farms, in a way to offer an alternative mean to this kind of photovoltaic power production ", he said. "Then, everything will be subjected to the regulation defining the purchase price of this green energy ; in fact such rate would drive customers’ desire to be equipped with it, as they would probably choose to resell this energy to ERDF network, which is far more profitable than consumption of their own. "Nevertheless", Hervé Le Bouc said, " for now, customers’ wish is driven by the product image, namely the idea of green energy ".