There are some 60 million kilometers (37.3 million miles) of roadways in the world, just sitting there. But adapting these surfaces to do anything besides passively carry traffic has proved difficult and prohibitively expensive.
However, an idea has gained traction in the last few years: embedding solar cells in roads. In 2014, an American couple launched the Solar Roadways project and collected more than $2 million on the crowdfunding site Indiegogo. Their effort, however, is much farther from reality than the Netherlands-based consortium SolaRoad, which has been operating a 70-meter (230-foot) cycle path that generates enough electricity for one or two households.
Read more on Quartz, published May 15, 2015.
Image by SolaRoad.