Solar is popping up just about everywhere, even landfills and parka pockets. So why not roads? Indeed, solar road projects are gaining interest around the world, and some promise to even charge electric cars while moving.

The Netherlands built the first solar road, a bike path, in 2014. France announced a bolder move in January—over the next five years, it plans to install 1,000 kilometers (621 miles) of solar roads, designed to supply power to five million people.

In fact, on December 22, France opened the world's first solar road for cars, in a Normandy village. The 0.6-mile route in Tourouvre-au-Perche is covered with 2,800 square meters of electricity-generating solar panels. The goal is powering street lighting.

The project, which cost