The Technology Behind the Solar Plane Solar Impulse-2

Flying on nothing but the energy generated by sunlight, the “zero fuel” solar plane, Solar Impulse-2, has just completed the second leg of its 10-leg trip around the world.

Taking off from Abu Dhabi (UAE) and flying to Ahmedabad, India via Muscat (Oman), the ultra-light aircraft is powered by 17,000 solar cells that generate electricity to run its four propellers.

Excess energy is stored in four energy-dense lithium-ion battery packs, which enable Solar Impulse-2 to fly through the night. Its 72m wingspan, by the way, is wider than the wingspan of the Boeing 747 (68.5m), known to all you aviation enthusiasts at the “Jumbo” jet.

Comparison: Solar Impulse-2 vs. Boeing 747

Comparison: Solar Impulse-2 vs. Boeing 747

Solar Impulse-2 weighs in at a featherweight 2.3 tons, and is designed to be highly efficient in flight, with its massive wings providing maximum lift with minimum drag (air resistance). Its battery packs sit behind its propellers, while the solar cells line the top of its wings.

Piloted alternatingly by one of two highly experienced pilots – Bertrand Piccard and Andre Borschberg – the single cockpit, single seat airplane consumes very low energy. However, its performance does come at a compromise on its airspeed, the top speed is only 100 miles per hour (160 kilometers per hour).

To put that in context, commercial airliners cruise at speeds in excess of 500 mph. For its journey to India, Solar Impulse-2 flew in at a leisurely 43 mph (70 kmph).

Its predecessor, Solar Impulse-1, made a widely covered flight from Europe to North Africa and across mainland USA. Solar Impulse-2 now takes it to the next step, and part of its journey will involve flying across the vast Pacific ocean.

Solar Impulse-2: a window into our future

While it may still just be a prototype, the aircraft is certainly a window into our future. It can fly at an altitude of up to 9,000m. That’s higher than Mt. Everest, in case you didn’t remember, and well within the flight altitude of commercial airliners.

Solar Impulse-2’s flight also implies that as solar cells become more efficient and battery packs capable of storing more energy, similar aircraft may be able to fly much faster and possibly with much heavier payloads (for instance, carrying more people).

The $150 million aircraft will now fly to Varanasi, before crossing over into Myanmar and China.

Interestingly, Andre Borschberg has already drawn up plans for the project’s next iteration, Solar Impulse 3.0, which will be an unmanned drone capable of flying non-stop for 6 months.

It just goes to show how quickly solar technology is progressing, and the kind of radical new applications we can expect in the future. Until then, you can follow Solar Impulse-2 live at


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Aniruddha Bhattacharjee
Aniruddha Bhattacharjee
Aniruddha has been a renewable energy researcher and report writer for over 3 years. He has also been a content developer for multiple websites, including portals on travel and tourism, restaurants and personal finance. He holds a bachelor's degree in mechanical engineering and a master's in endangered species conservation. Apart from renewable energy, Aniruddha is a keen motor sports and aviation enthusiast, and a beginner in photography.
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