The Solar Impulse 2 plane lands at an airport in Abu Dhabi, United Arab Emirates, July 26, 2016. [Photo/Agencies]

ABU DHABI - A solar-powered aircraft successfully completed the first fuel-free flight around the world on Tuesday, returning to Abu Dhabi after an epic 16-month voyage and demonstrating the potential of renewable energy.

The plane, Solar Impulse 2, touched down in the United Arab Emirates capital at 0005 GMT (0405 local time) on Tuesday.

It first took off from Abu Dhabi on March 9, 2015, beginning a landmark journey of about 40,000 km (24,500 miles) around the globe and nearly 500 hours of flying.

Unfavourable weather at times hindered smooth flying, causing the plane to be grounded for months in some countries.

Swiss explorers Bertrand Piccard and André Borschberg, Solar Impulse founders and pilots, took turns piloting the aircraft with a wingspan larger than a Boeing 747 and weighing only asmuch as a family car.

The Swiss team is campaigning to bolster support for cleanenergy. The propeller-driven aircraft's four engines are powered exclusively by energy collected from more than 17,000 solarcells built the plane's wings. Excess energy is stored in fourbatteries during daylight hours to keep the plane flying afterdark.

Over its entire mission, Solar Impulse 2 cruised ataltitudes of up to 9,000 metres and at an average speed ofbetween 45 and 90 km (12.5 and 25 miles) per hour. The plane had 16 stopovers along the way including in Oman, India, Myanmar,China, Japan, the United States, Spain and Egypt.

Abu Dhabi's green energy firm Masdar is the official hostpartner of Solar Impulse 2. Oil-rich Abu Dhabi is investing billions in industry, tourism and renewables to diversify itseconomy away from oil.