A car is seen parked at a service station for electric cars powered by solar energy in the village of Wolpertshausen near Schwaebisch Hall, Germany, March 18, 2016. Wolpertshausen produces up to 30 percent more electricity from renewable sources (biogas generator, wind turbines and solar panels on the roofs) than its 1,300 residents use. Picture taken March 18, 2016. REUTERS/Michaela Rehle 

Juergen Silberzahn, mayor of Wolpertshausen, poses in front of a service station for electric cars powered by solar energy, in the village of Wolpertshausen near Schwaebisch Hall, Germany, March 18, 2016. Wolpertshausen produces up to 30 percent more electricity from renewable sources (biogas generator, wind turbines and solar panels on the roofs) than its 1,300 residents use. Picture taken March 18, 2016. REUTERS/Michaela Rehle 

Power lines and wind turbines are pictured at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

A vehicle drives past the solar panels near wind turbines at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Staff members walk into a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

A power worker walks near solar panels at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Wind turbines and solar panels are seen through a window at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Wind turbines stand around solar panels at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

A staff member works at the control center of a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

People walk past the solar panels at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Solar panels are pictured at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Wind turbines and solar panels are seen at a wind and solar energy storage and transmission power station from State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

People walk past solar panels as a wind turbine is seen at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Wind turbines and solar panels are seen at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Birds stand on the solar panels at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

People walk past the solar panels at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

Wind turbines and solar panels are seen at a wind and solar energy storage and transmission power station of State Grid Corporation of China, in Zhangjiakou of Hebei province, China, March 18, 2016. REUTERS/Jason Lee 

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

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 

Employees remove snow 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 

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 

Dmitry Baikalov, a duty engineer, walks past solar panels 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 

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 

A truck drives past 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 

Men stand in front of solar panels at the Mohammed bin Rashid Al Maktoum Solar Park in Dubai, November 28, 2015. REUTERS/Stringer

Dubai's ruler Sheikh Mohammed bin Rashid al-Maktoum (C) lays foundation stone for a solar plant for generating clean energy in Dubai, November 28, 2015. REUTERS/Stringer TPX IMAGES OF THE DAY

A man speaks on the phone as he walks past solar panels at the Mohammed bin Rashid Al Maktoum Solar Park in Dubai, November 28, 2015. Dubai will spend billions of dollars on generating clean energy, the government said on Saturday, aiming to have solar panels installed on the roofs of all buildings by 2030. The fast-growing desert city state of 2.4 million, located in one of the hottest regions of the world, uses huge amounts of energy to air-condition its skyscrapers and provide water supplies through desalination. The Dubai government will encourage building owners to place solar panels on their roofs and link them to a network of the local power utility, Dubai's ruler Sheikh Mohammed bin Rashid al-Maktoum said in a statement. All Dubai buildings would have solar cells by 2030. REUTERS/Stringer TPX IMAGES OF THE DAY

A farmer plants wheat with his tractor next to the Abengoa solar plant at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 25, 2015. REUTERS/Marcelo del Pozo 

A farmer plants wheat with his tractor next to the Abengoa solar plant at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 25, 2015. REUTERS/Marcelo del Pozo 

Farmers work a wheat field with their tractors next to the Abengoa solar plant at the "Solucar" solar park in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. 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 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. 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 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. 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 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. 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 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. 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 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. 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 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. 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 25, 2015. Spain's Abengoa started insolvency proceedings on Wednesday which could lead to Spain's largest bankruptcy on record, after a potential investor said it would not inject fresh capital into the engineering and renewables company. REUTERS/Marcelo del Pozo 

A tower of Abengoa solar plant at "Solucar" solar park is pictured in Sanlucar la Mayor, near the Andalusian capital of Seville, southern Spain November 13, 2015. REUTERS/Marcelo del Pozo TPX IMAGES OF THE DAY

The sun reflects off a solar collector assembly during sunset at the Andasol solar power station near Guadix, southern Spain June 30, 2015. The plant is the biggest solar farm in the world and provides electricity for up to about 500,000 people. The 620,000 curved mirrors harness the sun's power even after dark, and the glass alone would cover 1.5 square km (0.6 square miles) - the size of about 210 soccer pitches. REUTERS/Marcelo del PozoPICTURE 22 OF 25 FOR WIDER IMAGE STORY "EARTHPRINTS: ANDASOL SOLAR POWER STATION"SEARCH "MARCELO ANDASOL" FOR ALL IMAGES 

The main pipe of a power block at the Andasol solar power station is pictured near Guadix, southern Spain June 29, 2015. The plant is the biggest solar farm in the world and provides electricity for up to about 500,000 people. The 620,000 curved mirrors harness the sun's power even after dark, and the glass alone would cover 1.5 square km (0.6 square miles) - the size of about 210 soccer pitches. REUTERS/Marcelo del PozoPICTURE 21 OF 25 FOR WIDER IMAGE STORY "EARTHPRINTS: ANDASOL SOLAR POWER STATION"SEARCH "MARCELO ANDASOL" FOR ALL IMAGES 

A part of a power block at the Andasol solar power station is pictured near Guadix, southern Spain June 29, 2015. The plant is the biggest solar farm in the world and provides electricity for up to about 500,000 people. The 620,000 curved mirrors harness the sun's power even after dark, and the glass alone would cover 1.5 square km (0.6 square miles) - the size of about 210 soccer pitches. REUTERS/Marcelo del PozoPICTURE 20 OF 25 FOR WIDER IMAGE STORY "EARTHPRINTS: ANDASOL SOLAR POWER STATION"SEARCH "MARCELO ANDASOL" FOR ALL IMAGES 

Staff check a solar collector assembly at the Andasol solar power station near Guadix, southern Spain August 11, 2015. The plant is the biggest solar farm in the world and provides electricity for up to about 500,000 people. The 620,000 curved mirrors harness the sun's power even after dark, and the glass alone would cover 1.5 square km (0.6 square miles) - the size of about 210 soccer pitches. REUTERS/Marcelo del PozoPICTURE 18 OF 25 FOR WIDER IMAGE STORY "EARTHPRINTS: ANDASOL SOLAR POWER STATION"SEARCH "MARCELO ANDASOL" FOR ALL IMAGES