Club Watt in Rotterdam uses floor vibrations–generated by people walking and dancing–to power its light system.
The Mall of America in Minneapolis has long relied on human visitors to help warm its corridors, and now London and Paris are piping heat from crowded subway stations into nearby homes.
Scientists in Sweden have harnessed a protein from the glow-in-the-dark Aequorea victoria jellyfish to create miniature fuel cells for electronics and more.
Scientists at the University of California at Irvine developed a method for deriving hydrogen from processed sewage, which has been used to power fuel cells for cars.
This appears in the August 17, 2015 issue of TIME.