Above the clouds, always towards the sun

Solar Impulse, the solar-powered round-the-world flight.

Flying was always one of humankind’s dreams, in order to be able to observe the world where we live like a bird. But the beginnings were difficult, when the Wright brothers took to the air in their first gliders and later motor-powered aeroplanes at the start of the 20th century. Building on that, in the last 100 years, air travel has become one of the biggest commercial sectors with the highest CO2 emissions. Today, we are possibly witnessing a new revolution in air travel – without CO2.

SolarImpulse 1

SolarImpulse is a Swiss company that was founded in 2003 by Bertrand Piccard. He set himself the goal of building a solar-powered aeroplane. After a long search for investors, painstaking development and a lot of virtual flying, SolarImpulse 1 (HB-SIA) was the first aeroplane of its kind, with a wingspan of 63.4 metres and 12,508 solar cells on its wings. It weighed just 1,600 kilos and was powered by lithium polymer batteries and four electric motors. Initially, test flights were only carried out within Switzerland. The real test for SolarImpulse 1 came last year with a crossing of the USA in six stages from the west to the east coast. ECO123 had an exclusive report about it.

The pilots

 

 

 

 

SolarImpulse 2

In the spring, the prototype of the aeroplane SolarImpulse 2 (HB-SIB) was presented in Payerne (Switzerland), along with the plan to fly around the world in it. Bertrand Piccard showed ECO123 the brand new model in the hangar: “While we still had yesterday’s technology in SolarImpulse 1, in SolarImpulse 2 we have tomorrow’s. The most efficient and most powerful electric motors were incorporated, the lightest honeycomb construction method and the cockpit components needing the least power”. As an example, Piccard introduces the new satellite receiver which normally weighs 15 kilos at present, but which it has been possible to reduce to 5 kilos. “We were able to use SolarImpulse 1 as a flying laboratory to gather sufficient information and experience, so that we could build an aeroplane in which you can fly around the world”, André Borschberg added during a tour.
On the outside too you can see the differences between it and its predecessor. Overall, the plane is about ten metres longer and has a wingspan of 72 metres. It weighs 2.3 tonnes. In contrast with its predecessor, the cockpit is pressurised, which offers the pilots greater protection against external conditions. The plane is a flying high-tech laboratory. A new carbon fibre layering technique allows the weight to be reduced to 25 grams per square metre. In comparison, the paper on which you are reading this at the moment weighs 80g/m². The solar cells are only as thick as a hair. The cockpit and the batteries, which have an energy density of 260Wh/kg, are packed with the latest highly insulating foam in order to combat outside temperatures of between -40 °C and +40°C.
But despite the highly developed and integrated technical equipment in and around the plane, there are still two major risk factors. The cabin where the pilot sits alone on a reclining seat is only 3.8m³ big. This is where he has to sleep, eat, drink, exercise, and fly of course. Once under way on the journey around the world, always heading towards the sun, SolarImpulse 2 will land in many places in order to familiarise people both with the plane and the message about flying using renewable energy. But they have to cross two huge oceans. These two legs over the Pacific and the Atlantic are planned to take three to five days each, which could lead to two serious problems. What will the weather be like over the middle of the oceans, and how does the pilot stay awake for between three and five days and have the strength to fly the plane safely?

ECO123 asked the two pilots: how do you proceed if you hit an unforeseen weather situation, such as cloud that lets no sunshine through or something worse, such as storms?
Betrand Piccard: We have two safety backups. Firstly we have the ground team, which keeps abreast of weather conditions and carries out weather simulations. They can forecast the weather for us very well. Secondly, we have no fuel restrictions. We can fly north or south in order to avoid inclement weather.

ECO123: To what extent is SolarImpulse 2 more adaptable to bad weather than SI1, in order to ensure that the plane and the pilot remain unscathed?
Betrand Piccard: It doesn’t help to adapt still more to bad weather. Perhaps it is exactly the opposite. When we flew around Payerne with the first prototype, we knew the weather. Now we’re flying over the Pacific and there the weather can be much more unpredictable. We also have much better possibilities for simulating the route and the weather on the ground. And of course it is possible for the pilot to survive for five days and five nights in this plane. Furthermore, there is enough space in the plane to carry a life raft.

ECO123: How do you prepare yourself mentally and physically for the long flight?
André Borschberg: We both train. Last December and a year ago, Bertrand and I spent 72 hours without a break in the flight simulator. In the course of that, we practised flying but also resting, regenerating oneself and keeping fit during the flight. It is a combination of physical and mental fitness. I do yoga and Bertrand uses self-hypnosis on himself. Of course, the ground crew always keep an eye on us through the health management system.

In the spring of 2015, SolarImpulse 2 will be flying from the Persian Gulf to India and China, across the Pacific to America and across the Atlantic to Europe, and back to the Persian Gulf. The two pilots are considering a stop in Portugal (Beja). A total of ten legs are planned over five months, during which they will swap places in the single-seater plane, and cover 35,000 kilometres taking approximately 500 hours of flying.