Roads Paved With Solar Energy

Wattway solar panels (Image credit: Joachim Bertrand)

It would be an understatement to say that the company’s executives were surprised when all of France’s major media showed up at the Colas trade show booth in mid-October.

“It was incredible,” said Christophe Lienard, Colas’ Innovation Group Director. “Our work in road construction and maintenance doesn’t normally get that sort of attention.”

The media were there because Colas debuted the world’s first road surface that generates solar electricity, called Wattway. The panels, which are only a few millimeters thick, can be installed on top of any road surface without any additional civil engineering work, withstand all types of vehicle traffic, and every 20 square meters should generate enough energy to power a home.

Five years ago, the project was nothing more than an after-hours experiment in an engineer’s garage.

“He had a piece of road surface, photovoltaic modules, and some weights,” Lienard explained.

“We knew it had to be possible, but we didn’t know how.”

Colas management took an early iteration of the idea to the head of R&D at France’s prestigious CEA (Atomic Energy Commission), who told them they were crazy unless a truck could drive on it. It was a Friday, as Christophe Lienard remembers, and the CEA’s scientific director, Jean Therme, spent the weekend coming up with a workable solution.

What followed was four years of focused development, in partnership with the National Institute for Solar Energy, as the team confronted and overcame a number of significant challenges.

First, after two years of work, a severe Chinese manufacturing crisis on amorphous photovoltaic panels led to bankruptcies of its major partners in Europe, so it had to start its collaboration from scratch. This included finding a new photovoltaic technology, and the best supplier’s units appeared to be particularly fragile.

This meant that efficiency trade-offs loomed large, both due to the necessity for a strong surface (to endure those trucks), and the fact that while a road faces “up” toward the Sun, it doesn’t track its movement across the sky.

When they tested the product in 2014, they were surprised.

“We were prepared for a big drop in output, but we achieve 70% of the modules’ normal efficiency,” said Lienard. “And we achieved the required durability with a surface that is no thicker than an iPad.”

Wattway promises to help cities generate electricity close to where it’s consumed (something Christophe Lienard calls being “energy positive”). It also opens up novel business models for Colas, which traditionally sold roads and maintenance services, but can now explore a variety of partnership options based on electricity generated by projects.

It has set up a business unit to retail Wattway worldwide, where the engineer who worked in that garage five years ago, Jean-Luc Gauthier, is now the top scientist.

Along the way, Colas also formalized its innovation approach, with Hervé Le Bouc, its Chairman, creating a board that Christophe Lienard would lead, comprised of 12 representatives from various geographies and operational areas. Its first task was to identify the innovation already underway in the 50 countries in which it operates (it found 100), and then do some gap analyses to uncover areas for additional focus.

A subsequent internal contest netted 377 different projects or solutions and, from that, yielded 6 major innovation innovations, of which Wattway is one.

“We’re energized about the future in ways we never were before,” Lienard said. “Our goal is to be lean and be faster at getting more prototypes into the field.”

He wouldn’t reveal much about the other 5 innovation project, though he did say that Colas was in conversations with all the major vehicle manufacturers and Internet services providers about the potential for a ‘smart’ road.