Solar Impulse 2 completes world tour

THE solar-powered aircraft Solar Impulse 2 (Si2) landed back in Abu Dhabi, UAE last night, completing its 18-month world tour and proving chemistry solutions used in renewable technologies are sustainable.

The carbon-fibre craft started its more than 40,000 km journey in March 2015, breaking eight world records as it went, including the longest distance flown in by an electric aircraft.

Using solar power alone drawn from over 17,000 solar cells spread over its wings – each measuring the width of a human hair – Si2 flew over China and the US, and the Pacific and Atlantic oceans, without emitting any carbon.

With a top speed of around 100 km/h, Si2 had to complete significant portions of the journey at night. Four lithium polymer batteries – which accounted for around 25% of the plane’s 2.3 t weight – stored excess energy from the cells for non-daylight flight.

The 13-year concept-to-completion project received significant technological and chemical solution contributions by European chemical companies Solvay and Covestro. Together they contributed ultra-lightweight insulation and composite materials for the wing spars and rear stabiliser parts, energy-efficient engines, and heat and UV-protective coatings.

Jean-Pierre Clamadieu, CEO of Solvay, wrote a letter to the pilots Bertrand Piccard and André Borschberg, congratulating them on their work and achievement.

“I would like to say a huge thank you for these extraordinary years, marked with dreams, challenges, big and small technological victories…All limits of materials we have pushed further to make this plane fly with you, reinforce our belief that chemistry provides effective solutions for the sustainable development of our societies.

“Of course the true journey of Solar Impulse has no finish line. The message it carries is one of enduring innovation, possibility, persistence and conviction. Tomorrow’s answers are within reach today,” he wrote.

The pilots have not always had a smooth run on the journey. An unscheduled stop in Japan in June 2015 and a ten-month grounding in Hawaii, after the plane's batteries overheated during the 177-hour crossing were responsible for the delays. The team had to fix the battery fault before it was finally cleared to resume the mission in February 2016.

The final leg of the journey was a 48-hour stint from Cairo, Egypt, covering a distance of almost 2,700 km using nearly 918 kWh of solar energy. Piccard handled the controls during the final landing.

The full log of Si2’s journey can be found here http://www.solarimpulse.com/leg-17-from-Cairo-to-Abu_Dhabi