9. Piezoelectric Roadways
Piezoelectric materials embedded in road surfaces convert the pressure and vibrations from passing vehicles into electrical energy. In heavily trafficked, polluted cities, these smart roadways can capture kinetic energy that would otherwise disperse as heat and sound. Trials in Israel and California have shown promising results in powering street lighting and traffic systems. For instance, a one-mile stretch of road with piezoelectric devices can generate approximately 72,800 kilowatt-hours of energy per year. (energy.ca.gov) Read about pilot projects at Smithsonian Magazine.