Photographers gather to take pictures of pilot Andre Borschberg (C) ahead of the take off of Solar Impulse 2-a solar powered plane- in Nanjing, China, May 31, 2015. The world's largest solar-powered airplane, Solar Impulse 2, took off from eastern China's Nanjing on Sunday to continue its round-the-world voyage. The Swiss-made plane left Nanjing's Lukou International Airport at 2:39 in the early morning, with former fighter pilot Borschberg at the controls alone for the entire 8,200-kilometer flight from Nanjing to Hawaii, the toughest leg of its marathon adventure. (Photo by Reuters/Solar Impulse)

Ricardo Azevedo rides his Honda NX 200 motorbike, which he converted to be powered by water, in Salto, northwest of Sao Paulo, Brazil, August 6, 2015. The Sao Paulo civil servant built the motorbike, which can cover up to 500 kilometres (311 miles) fuelled by just one litre of water. Dubbed “Moto Power H2O” the bike is powered by the process of electrolysis, which breaks the water molecule down into its constituent elements. (Photo by Nacho Doce/Reuters)

Rebecca Bailey rides a unicycle during a winter nor'easter snow storm in Boston, Massachusetts, U.S. February 9, 2017. (Photo by Brian Snyder/Reuters)

A partial solar eclipse is seen in a break in the clouds during rush hour in downtown Wichita Kan., Thursday, October 23, 2014. A partial eclipse occurs when the moon covers a portion of the sun as seen from the Earth. (AP Photo/The Wichita Eagle, Travis Heying)

is a concentrated solar power plant with a molten salt heat storage system. It is located within the city limits of Fuentes de Andalucía in the province of Seville, Spain.

Workers work inside a new Antonov airplane at the Antonov aircraft plant in Kiev, Ukraine, September 7, 2015. State-run aircraft maker Antonov built more than 22,000 units of more than one hundred types and modifications of passenger, transport and special-purpose aircraft, including the world's biggest cargo plane Antonov-225 (Mriya), according to the company's official website. (Photo by Gleb Garanich/Reuters)

A crane loads logs at the Novoyeniseisk wood processing plant, with the air temperature at about minus 20 degrees Celsius (minus 4 degrees Fahrenheit), in the town of Lesosibirsk in Krasnoyarsk Region, Siberia, Russia, February 16, 2016. The plant exports timber to Europe, Northern Africa and Asia. The Taiga, also known as the boreal forest, on the coast of the Angara River and Yenisei River is one of the main areas for the industrial cutting of wood thanks to the high quality of the Angara pine. Open air work continues all year around regardless to temperatures which can drop to minus 52 degrees Celsius (minus 61.6 degrees Fahrenheit), according to employees. (Photo by Ilya Naymushin/Reuters)

A undated handout image provided by the Bochum University of Applied Sciences (Hochschule Bochum) on 04 October 2013 shows the German team Bochum's Cruiser class solar car during a test drive in the Northern Territoty, Australia, 16 September 2013. The Dutch vehicle is competing in the World Solar Challenge, driving from Darwin to Adelaide starting on 06 October 2013. (Photo by Hochschule Bochum/EPA)