An Electrify SG engineer shows how a PowerPod is installed to record data of photovoltaic solar panels on a rooftop in Singapore, December 18, 2017. Picture taken December 18, 2017. REUTERS/Edgar Su 

An Electrify SG engineer shows a PowerPod that will be installed to record data of photovoltaic solar panels on a rooftop in Singapore, December 18, 2017. Picture taken December 18, 2017. REUTERS/Edgar Su 

A Pere David's deer rests next to a watering hole and a solar panel in Thompson, Texas on August 30, 2017. Picture taken on August 30, 2017. REUTERS/Adrees Latif TPX IMAGES OF THE DAY 

A worker works at a solar power plant by Superblock, Southeast Asia's biggest producer of solar power in Phetchaburi province, Thailand, August 23, 2017. REUTERS/Athit Perawongmetha TPX IMAGES OF THE DAY 

Photovoltaic panels are seen on a farm outside the town of Mosta, Malta, August 7, 2017. REUTERS/Darrin Zammit Lupi 

Photovoltaic panels are seen on a farm outside the town of Mosta, Malta, August 7, 2017. REUTERS/Darrin Zammit Lupi 

Photovoltaic panels are seen on a farm outside the town of Mosta, Malta, August 7, 2017. REUTERS/Darrin Zammit Lupi 

Members of the Nemeth family sit in their room lit by solar-charged LED strips that will help them reduce their energy bill under a programme run by the Romaversitas Foundation in Bicske, Hungary, December 15, 2016. Picture taken December 15, 2016. REUTERS/Bernadett Szabo 

Tesla's electric car, Powerwall and solar roof are shown by Tesla Motors Inc Chief Executive Elon Musk, unveiling new energy products aimed at illustrating the benefits of combining his electric car and battery maker with solar installer SolarCity Corp, in Los Angeles, California, U.S., October 28, 2016. REUTERS/Nichola Groom/File Photo GLOBAL BUSINESS WEEK AHEAD PACKAGE - SEARCH 'BUSINESS WEEK AHEAD NOV 7' FOR ALL IMAGES 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake TPX IMAGES OF THE DAY

A solar panel is shown during installation on a residential roof in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Workers lift a solar panel onto a roof during a residential solar installation in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

A solar installer carries a solar panel during an installation at a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Workers lift a solar panel onto a roof during a residential solar installation in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Multiple homes with solar panels are shown in Scripps Ranch, San Diego, California, U.S. October 5, 2016. Picture taken October 5, 2016. REUTERS/Mike Blake 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Solar installers from Baker Electric place solar panels on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

A solar installer from Baker Electric installs a solar panel on the roof of a residential home in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

A DC to AC solar converter is shown during the installation of a residential solar power system in Scripts Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

A DC to AC solar converter is shown during the installation of a residential solar power system in Scripps Ranch, San Diego, California, U.S. October 14, 2016. Picture taken October 14, 2016. REUTERS/Mike Blake 

Multiple homes with solar panels are shown in Scripps Ranch, San Diego, California, U.S. October 5, 2016. Picture taken October 5, 2016. REUTERS/Mike Blake 

Multiple homes with solar panels are shown in Scripps Ranch, San Diego, California, U.S. October 5, 2016. Picture taken October 5, 2016. REUTERS/Mike Blake 

Multiple homes with solar panels are shown in Scripps Ranch, San Diego, California, U.S. October 5, 2016. Picture taken October 5, 2016. REUTERS/Mike Blake 

Multiple homes with solar panels are shown in Scripps Ranch, San Diego, California, U.S. October 5, 2016. Picture taken October 5, 2016. REUTERS/Mike Blake 

Belgian scientists Marjolein Vanoppen and Sebastiaan Derese demonstrate the use of a machine that turns urine into drinkable water and fertilizer using solar energy, at the University of Ghent, Belgium, July 26, 2016. REUTERS/Francois Lenoir

Belgian scientists Marjolein Vanoppen and Sebastiaan Derese (R) demonstrate the use of a machine that turns urine into drinkable water and fertilizer using solar energy, at the University of Ghent, Belgium, July 26, 2016. REUTERS/Francois Lenoir TPX IMAGES OF THE DAY

Solar panels are seen on the roof of a car park in Mountain View, California April 7, 2016. REUTERS/Noah Berger TPX IMAGES OF THE DAY

A tower belonging to the Abengoa solar plant is seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain March 4, 2016. REUTERS/Marcelo del Pozo TPX IMAGES OF THE DAY

The Solar Impulse 2 airplane, flown by test pilot Markus Scherdel, flies off the coast of Oahu during a test flight from Kalaealoa Airfield in Kapolei, Hawaii, March 3, 2016. REUTERS/Eugene Tanner/Pool 

The Solar Impulse 2 airplane, flown by test pilot Markus Scherdel, flies off the coast of Oahu during a test flight from Kalaealoa Airfield in Kapolei, Hawaii, March 3, 2016. REUTERS/Eugene Tanner/Pool 

The Solar Impulse 2 airplane, flown by test pilot Markus Scherdel, flies off the coast of Oahu during a test flight from Kalaealoa Airfield in Kapolei, Hawaii, March 3, 2016. REUTERS/Eugene Tanner/Pool 

The Solar Impulse 2 airplane, flown by test pilot Markus Scherdel, flies off the coast of Oahu during a test flight from Kalaealoa Airfield in Kapolei, Hawaii, March 3, 2016. REUTERS/Eugene Tanner/Pool 

A field with heliostat mirrors are seen during the construction of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen 

Heliostat mirrors reflect their surroundings in a field at the construction site of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen TPX IMAGES OF THE DAY

A general view picture shows the foundations of a 240 meter (787 feet) solar-power tower, which is under construction in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen 

A vacuum lifter and crane moves a heliostat mirror during the construction of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen 

A worker is silhoutted as he works on the construction of a boiler at the building site of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen 

Heliostat mirrors reflect the sky in a field at the construction site of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen 

Construction workers install heliostat mirrors during the construction of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen 

Construction workers use a vacuum lifter and crane to move heliostat mirrors during the construction of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen 

A solar panel is placed on rubble along a street in the Douma neighbourhood of Damascus, Syria February 9, 2016. REUTERS/Bassam Khabieh 

Bricks are placed behind a fence near a closed brick factory on the outskirts of Beijing, China, January, 18, 2016. On the outskirts of Beijing, the disused factories of Chaomidian show the impact of China's drive to shut down thousands of small firms causing big pollution. Amid scrapheaps and idle machinery, the community has clean air these days - and no jobs. Picture taken January 18, 2016. REUTERS/Jason Lee

Dmitry Baikalov, a duty engineer, inspects equipment at the Abakan solar electric station in a suburb of the Siberian town of Abakan, Khakassia Republic, Russia, December 17, 2015. Owned by EuroSibenergo company of the En+ Group, the solar electric plant in Siberia with a generating capacity of 5.2 megawatt (MW) will be in operation on December 21, according to the official representative of the company. Picture taken December 17, 2015. REUTERS/Ilya Naymushin 

Towers belonging to the Abengoa Solar plant is seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

Towers belonging to the Abengoa Solar plant are seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

Towers belonging to the Abengoa Solar plant are seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

Towers belonging to the Abengoa Solar plant are seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

Towers belonging to the Abengoa Solar plant are seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

Towers belonging to the Abengoa Solar plant is seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

A tower belonging to the Abengoa Solar plant is seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

A tower belonging to the Abengoa Solar plant is seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

A tower belonging to the Abengoa Solar plant is seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

A tower belonging to the Abengoa Solar plant is seen at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 30, 2015. REUTERS/Marcelo del Pozo 

Solar panels are installed by workers on the Champs Elysees avenue in Paris ahead of ahead of the World Climate Change Conference 2015 (COP21), in Paris, France, November 29, 2015. REUTERS/Benoit Tessier 

A cyclist wears a helmet with a solar panel attached as he participates in a march the day before the Paris World Climate Change Conference, along the main street of Adelaide, South Australia November 29, 2015. REUTERS/David Gray