Solar powered lights are pictured along the Hoernli ridge on the Matterhorn in Zermatt, Switzerland, July 13, 2015. REUTERS/Denis Balibouse 

A model poses on a solar "lazy sun bed" for luxury boats during the Monaco Yacht show, September 22, 2010. REUTERS/Eric Gaillard 

Matoula Kastrioti, 46, who suffers from multiple sclerosis, sits on a "Seatrac", a solar-powered device that allows people with kinetic disabilities to enter and get out of the sea autonomously, at a beach in Alepochori, west of Athens July 12, 2013. REUTERS/Yorgos Karahalis 

A laborer checks the solar panel of a street light at a newly constructed solar housing complex in the eastern Indian city of Kolkata July 8, 2008. The buildings are integrated with photovoltaic technology and the complex is constructed by West Bengal Renewable Energy Development Agency. REUTERS/Parth Sanyal 

A solar-powered light panel is seen inside a provisional camp for earthquake victims while people sell electronic products in Port-au-Prince September 30, 2010. REUTERS/Eduardo Munoz 

Surinamese native Georgette Adipi of the women's organization Maipafolo works with her solar-powered sewing machine in the Maroon village of Nieuw Aurora, whose inhabitants are descendants of slaves, along the upper Suriname River in district Sipaliwini, September 26, 2012. REUTERS/Ranu Abhelakh 

El Alto public university students stand next to prototype of a solar car in El Alto, Bolivia, April 23, 2015. REUTERS/David Mercado 

A tower at Abengoa solar plant at "Solucar" solar park is seen in Sanlucar la Mayor, near the Andalusian capital of Seville, Spain, November 17, 2014. REUTERS/Marcelo del Pozo 

The Solar Impulse 2 airplane, piloted by Andre Borschberg, prepares to land at Kalaeloa airport after flying non-stop from Nagoya, Japan in Kapolei, Hawaii, July 3, 2015. The aircraft, powered only by the sun's energy and piloted alternatively by Swiss explorers Borschberg and Bertrand Piccard, has broken a world record for the longest non-stop solo flight. REUTERS/Hugh Gentry 

A model wears a jacket with an integrated solar module in Buenos Aires, Argentina, October 1, 2008. The module converts sunlight into electric power that can be used to charge cell phones, iPods, digital cameras and rechargeable batteries. The jacket is part of a collection called "Intelligent clothes" by the Argentine brand Indarra.dtx. REUTERS/Enrique Marcarian 

Solar panels generate carbon-free electricity for Austin City Hall in Texas December 15, 2010. REUTERS/Chris Baltimore 

The Turanor PlanetSolar, the world's largest solar-powered boat, travels on the Seine river next to the Eiffel tower in Paris September 10, 2013. REUTERS/Charles Platiau 

A man looks at the world's first energy powered wheel for bicycles during the 'Intersolar' Europe trade fair in Munich June 13, 2012. The front wheel called 'Roola' is developed by proEco, powers at 250 watt and travels up to 65 km (40 miles). REUTERS/Michaela Rehle 

FH Bochum Solar Car Team from Germany, drives their solar car SolarWorld 1 across the Canadian prairies in the North American Solar Car Challenge near Medicine Hat, July 22, 2008. REUTERS/Todd Korol 

A general view shows solar panels to produce renewable energy at the photovoltaic park in Les Mees, in the department of Alpes-de-Haute-Provence, southern France March 31, 2015. REUTERS/Jean-Paul Pelissier 

A parking structure at the University of California San Diego uses innovative solar trees to collect renewable energy from the Sun February 8, 2011. Each "Solar Tree" will generate more than 17,000 hours of clean energy per year, enough to power more than four single family homes and avoids 13.2 metric tons of carbon emissions. REUTERS/Mike Blake 

A bus passes a green "Solarbox" to charge his phone in central London October 3, 2014. Some of London's famous red telephone boxes are going green, transformed into free, solar-powered mobile chargers to provide a carbon-neutral source of energy in the city. REUTERS/Luke MacGregor 

A laborer, who works in a salt pan, covers her face beside a solar panel outside a shelter in Little Rann of Kutch in the western Indian state of Gujarat March 2, 2014. REUTERS/Ahmad Masood 

A student test drives a motorized rickshaw running on solar energy on the streets of Lima October 28, 2010. Werner Pacheco, a teacher and researcher at the San Marcos University's School of Electronics and Electrical Engineering (FIEE), built the first solar motorized rickshaw in Peru with a group of students, which runs primarily on solar energy panels attached to the roof of the body and connected directly to the engine. The vehicle can also be pedaled or run on batteries, according to Pacheco. REUTERS/Mariana Bazo 

A general view of the new PS20 solar plant which was inaugurated last month at "Solucar" solar park in Sanlucar La Mayor, near Seville, October 7, 2009. The solar thermal power plant uses mirrors to concentrate the sun's rays onto towers where they produce steam to drive a turbine, producing electricity. REUTERS/Marcelo del Pozo 

A woman stands in front of an illuminated house powered by solar energy at Meerwada village of Guna district in the central Indian state of Madhya Pradesh June 18, 2012. REUTERS/Adnan Abidi 

A man looks at a lighted solar tree at the Jerusalem Festival of Lights at Jerusalem's Old City June 9, 2010. REUTERS/Ronen Zvulun