How Solar Panel Highways Work

Solar roadway in China
The first vehicle drives through a photovoltaic road Dec. 28, 2017, in Jinan, China. Visual China Group/Getty

These days, we can find solar panels, also known as photovoltaic cells, just about everywhere. They're on the roofs of our homes, bringing down the cost of electricity. They're even on top of a few cars. In 2019, Toyota began testing outfitting the Prius Prime with solar battery panels on its roof, hood and rear hatch door. Altogether, those panels are slated to provide up to 27.6 miles (44.4 kilometers) of electric power daily, says Green Car Reports. Two other European companies have plans to unveil solar-assisted cars, too.

Some experts have theorized that if we were to lay down a gigantic number of solar panels over a wide area, we could absorb enough sunlight to power entire cities, effectively ending our energy crisis. The problem is, there's nowhere to put them. We can't exactly stick panels across the entire countryside.


Or can we? The U.S., for example, has a network of roads all over the country. Why not place panels along the roadways as sound barriers, or an even more extreme idea – make the roads themselves out of solar panels? They have.

These "solar highways" or "solar roadways" consist of individual solar panels with three layers: a top layer of high-strength, textured glass that provides traction for vehicles, an array of solar cells beneath that for gathering energy, and a base plate that distributes the collected power, according to Solar Roadways. They're more than just solar energy collectors, too. The panels contain LED lights, powered by the sun, that can act as road and warning signs built into the road itself. In addition, they can use gathered heat to melt snow and ice on the roads.


How Feasible Are Solar Roadways?

Though a few different companies, in a few different countries, have attempted solar roads, many of the initial concerns have proven to have merit. For example, flat panels are less effective at capturing sunlight than tilted panels. Shade over even a small portion of the panel drastically reduces efficiency. Dust, debris, a lack of air circulation on the surface, and the thick glass coating necessary to help the panel withstand traffic can also reduce a panel's effectiveness. Furthermore, that glass surface doesn't provide the kind of traction that drivers are accustomed to.

Here's what went wrong in the quest for durable and efficient solar roads, as illustrated largely by the solar road in Normandy, France. The plans for the solar road in Normandy were announced in 2016, but after three years of use, the experiment was declared a failure. The plans called for a stretch of about 620 miles (1,000 kilometers), with the goal of generating enough power for 5 million homes, writes Big Think. The first stretch of road completed was just over half a mile long and was expected to power up to 5,000 homes, but it became clear rather quickly that expectations would not be met.


The solar panels on the French road became damaged more quickly than expected, due to wear and tear caused by traffic and weather, and many had to be removed after they were damaged beyond repair. Worse, even at peak efficiency, the panels proved to be less effective at generating power than regular, tilted solar panels, like those commonly mounted alongside the road rather than on it, or in other locations such as on rooftops and parking structures.

Though Normandy is probably the biggest example of a failed solar roadway experiment, there are others. Along a road in China, a solar panel was stolen, leading to the project's cancellation. In Missouri, the solar panel company and the government failed to reach an agreement on a planned project.

Though the excitement seems to have slowed overall, some projects are still underway. A lab in Atlanta, Georgia, for example, maintains that solar roads are still worth studying and trying to improve them. As of February 2019, an 18-mile stretch along Interstate 85 is still in use. In addition to powering nearby buildings, experts at the Ray C. Anderson Foundation hope that future versions of solar roads can charge electric vehicles and actually self-illuminate to help drivers see. Furthermore, newer versions of the solar panels are more durable and provide better traction. The foundation says it's better positioned financially to work on unproven technology, since the state or federal departments of technology would have a harder time justifying the use of taxpayer funds to continue investing in a project that has already failed to meet expectations.

So whether or not solar roads will be viable remains to be seen, but not everyone is ready to give up on the idea.


Lots More Information

More Great Links


  • Jacquot, Jeremy Elton. "Solar Roadways: Energy-Generating Roads Made Out of Glass and Solar Cells." Aug. 20, 2007. (Sept. 16, 2019)
  • Neimark, Gillian. "Despite criticism, solar roads remain part of Georgia sustainable highway lab." The Energy News Network. Feb. 26, 2019. (Sept. 16, 2019)
  • Northwestern University. "How efficient are solar panels?" (Sept. 16, 2019)
  • Rivera, Dylan. "Oregon installs first highway solar project." The Oregonian. Aug. 7, 2008. (Sept. 16, 2019)
  • Ryan, Dylan. "Solar panels replaced tarmac on a road – here are the results." The Conversation. Sept. 21, 2018. (Sept. 16, 2019)
  • Thomson, Andrew. "Solar freakin' roadways? Why the future of this technology may not be so bright." The Conversation. Dec. 17, 2015. (Sept. 16, 2019)