MINES Saint-Étienne

What happened to the French Solar Road project?


“Complete failure”, “colossal disaster”, “total flop”… these are just some of the headlines describing what was intended to be the longest solar road in the world, and a flagship project towards achieving the generalization of the use of renewable energy. So what really happened to the French Solar Road project?

The “Wattway”: a concept doomed from the start 

Scientists didn’t take long to notice the obvious flaws when the idea of building solar roads was first introduced by the French government. Among the defects of such endeavour, specialists singled out the inefficiency of flat surfaced solar panels in capturing sunlight; and thus producing acceptable levels of energy. Besides, it was quite clear that driving over the said panels would not help either: pollution would build up on their surface, reducing their ability to catch sunlight; and vehicles would inevitably cause a lot of damage to them. That’s exactly what happened.

The French government didn’t give much credit to these “allegations” and made the choice of chasing “green electricity” headlines instead of chasing efficiency, with a “first of a kind” solar road, consisting of 2 800 photovoltaic panels, also known as the “Wattway”. In 2016, France thus decided to invest in a rural solar roadway in Normandy, spending 5 million euros in the process. The 1-kilometre long “Wattway” was a test that was part of the ambitious plan to build 1 000 kilometres of highways composed of photovoltaic panels, that would be able to power up to 5 million homes.

Results are far below expectations

Le Monde published a story that labelled the solar road a “fiasco” that was “neither economically viable, nor energy efficient”. The French newspaper stressed that 3 years after its “grand opening” by the French Ministry of the Environment, (who, at the time, praised the project and went as far as calling it “unprecedented”) the road had become so damaged that parts of it had to be demolished as they were beyond repair. In addition, even when in full working order, the solar road never managed to meet the energy production that was announced (5 000 homes). Instead, it was producing only half the energy expected, due to leaves falling on the road. After producing just over 50% of the expected 790 kilowatt-hours (kWh) per day the first year, a total of 149,459 kWh over the year, the solar road generated 78,397 kWh in 2018 and only 37,900 kWh since January 2019.

Engineering mishaps result in a noisy and inefficient road 

Colas, the construction group who built the solar road, had said that the solar panels were strong enough to support even large vehicles as they were covered with a silicon-based resin. But there lies the problem. Because of the resin covering them, driving over the solar panels was very noisy and extremely uncomfortable. Besides, Le Monde reported that the road “looked bad with its ragged joints”, with “solar panels that peel off the road and many splinters all over the resin that protects the photovoltaic cells”. In fact, the road required a lot more maintenance than its builders anticipated. 

To make matters worse, engineers seemed to dismiss the fact that Normandy is one of the least sunny areas in France, known instead for the possibility of having occasional storms. It comes as no surprise then that a few thunderstorms have damaged the road, breaking solar panels. 

All these shortcomings have been reported by the Global Construction Review, which harshly said that the project engineers failed miserably in taking into account several external factors such as the aforementioned thunderstorms and leaf mould. The last nail in the coffin of the solar road was planted by Marc Jedliczka, vice president of the Network of Energy Transition, who stated: “The technical and economic elements of the project were not sufficiently understood. It is a total absurdity to innovate at the expense of solutions that already exist and are much more profitable, such as photovoltaic on roofs”. 

Mines Saint-Etienne’s involvement in the issues related to the sustainable production of cleaner, safer and efficient energy translates into a Master of Process Engineering & Industrial Energy Efficiency. Discover it now!