Wedges of an orange generate enough current and electrical juice – 3.5 volts – to power an LED. The fruit’s citric acid helps electrons flow from galvanized nails to copper wire in this 14-hour exposure. This image was published in September’s Visions of Earth, a trio of photos that appear in each issue of National Geographic. (Photo by Caleb Charland/National Geographic)

Two women pose as they drink real ale at the Great British Beer Festival in the Olympia exhibition centre on August 13, 2013 in London, England. The festival, which runs until August 17, 2013, has over 24 bars serving over 800 different beers, ciders and perries. (Photo by Oli Scarff)

Model Natasha Poly poses on the red carpet as she arrives for the screening of the film “Carol” in competition at the 68th Cannes Film Festival in Cannes, southern France, May 17, 2015. (Photo by Eric Gaillard/Reuters)

Kevin and Merith Starren have their picture taken by Merith's brother Mark Ernst (R) and nephew Logan Ernst (L) in front of a 50-foot snowman named “Granddaddy” in Gilman, Minnesota, March 6, 2014. (Photo by Eric Miller/Reuters)

Employees prepare spacesuits at the Russian-leased Baikonur cosmodrome in Kazakhstan on August 19, 2015. Members of the main crew of the 45/46 expedition to the International Space Station ISS, Kazakhstan's cosmonaut Aydyn Aimbetov, Russian cosmonaut Sergei Volkov and Denmark's astronaut Andreas Mogensen from the European Space Agency, are scheduled to blast off to the International Space Station (ISS) on September 2, 2015. (Photo by AFP Photo)

Sepak Takraw – ISTAF Super Series Korea 2014-15 – Gunsan City, South Korea April 26, 2015: Thailand's Fueangfa (L) in action during the final. (Photo by Jeremy Lee/Reuters)

A groom leads his horse in the equine pool after working out on the track, during early morning workouts for the upcoming Derby race in Mumbai January 29, 2015. (Photo by Danish Siddiqui/Reuters)

Models prepare backstage before a presentation as part of Fashion Weekend Plus Size Summer 2015 collection show in Sao Paulo, July 25, 2015. (Photo by Nacho Doce/Reuters)