Solar Impulse 2, the first aircraft completely sustained by solar power to fly around the world, is set to take flight March 2015. The pioneers behind this extraordinary feat, Betrand Piccard and Andre Borschberg, are excited to share their story.
Betrand Piccard is the initiator and chairman of Solar Impulse 2, and André Borschberg is the CEO. Piccard is the voice of the project, carrying its vision and message to the industrial, political and media world. Borschberg assembled the technical team and supervised the airplane’s design and construction, and is responsible for the route strategy.
The two aviation aficionados met in 2003 when the Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Federal Institute of Technology, in Lausanne decided to carry out the feasibility of the project, led by Borschberg.
A graduate from the EPFL as an engineer in mechanics and thermodynamics, Borschberg trained as a pilot in the Swiss Air Force, has a variety of professional airplane and helicopter pilot’s licenses and performs aerobatics in his free time. Borschberg has led numerous technology projects, companies and start-ups as both an investor and entrepreneur.
Piccard studied medicine, completing a double specialization in psychiatry and psychotherapy, at the University of Lausanne, while maintaining pursuit of his passion for aviation. A pioneer of hang-gliding and ultralight flying in the 1970s, Piccard became the European hang-glider aerobatics champion in 1985. Then he obtained his licenses to fly hot-air balloons, airplanes, gliders and motor-gliders. In their 1999 “Breitling Orbiter” project, Piccard and Brian Jones completed the first non-stop, around-the-world balloon flight in 19 days — the longest flight in the history of aviation in terms of duration and distance.
After his around-the-world balloon flight, Piccard realized a lack of fuel was a real risk and using renewable energy sources, like solar, could provide a valuable solution. He vowed to make another around-the-world flight, but this time without using any fossil fuels. Thus the Solar Impulse 1 prototype was born, and Borschberg piloted a successful single day-and-night flight, which led to the development of Solar Impulse 2.
Solar Impulse 2, weighing in at 2.3 tons, uses SunPower solar cells, panels and systems that were installed by a team of 50 engineers and technicians. SunPower’s Maxeon solar cell technology was selected because of its efficiency and thickness of its solar cell, an average of only 135 microns, which is important for the power to weight ratio of the aircraft.
The 17-m wingspan contains more than 17,000 monocrystalline silicon solar cells supplying four electric 17.5 CV motors with enough energy to power the aircraft through the night. The solar cells capture the sun’s energy and convert it into electricity that simultaneously powers the plane’s engines and recharges lithium polymer batteries. This allows the plane to fly throughout the night without a drop of fuel. To maximize energy consumption, the plane ascends to 8,500m during the day and descends to 1,500m at night.
Each generating 17.4 hp, the motors are mounted below the wings and fitted with a reduction gear limiting the rotation of speed of a 4-m diameter, two-bladed propeller to 525 rev/min. This results in a record 94% efficiency.
Two composite materials make up the frame: carbon fiber and honeycomb sandwich. A skin of encapsulated solar cells covers the upper-wing surface, while the lower-wing surface is covered by a high-strength, flexible skin. The plane maintains its rigidity with 140 carbon-fiber ribs spaced 50 cm apart, giving the wing its aerodynamic cross-section and allowing the aircraft to fly between 36 km/h at sea level and 140 km/h at maximum altitude.
With an idea as revolutionary as Solar Impulse 2, a multitude of new technologies and construction models have been developed along the way through collaboration with 80 technological partners. For instance, the insulation foam used with the batteries was developed by Bayer MaterialScience. Likewise, Solvay invented electrolytes that allow energy density on the batteries to be increased, and Decision has created the lightest carbon fibers to date.
“We can already consider multiple developments in the area of ultralight materials and energy savings, in the efficiency of components, in greater reliability and performance of electric motors, in the efficiency of solar cells and in energy storage through increased energy density of batteries,” says Borschberg. “This new [insulation] foam has very thin pores, high rigidity and structural strength, while remaining very light.”
“We also see enormous potential with our newest partner, ABB,” he continues. “[Dedicated] ABB and Solar Impulse [teams are] scrutinizing a multitude of options in several technological fields from solar and storage, to low voltage equipment to see where we can both profit from each other’s expertise.”
A team of design and assembly engineers spent over a decade bringing Piccard and Borschberg’s vision to fruition. The team completed construction on the major parts of the plane this February and completed its final assembly this March. They chronicled the whole process from its conception to completion, including the challenges they faced, in a series of web articles; follow their journey here.
Weather permitting, the first test flight is scheduled for the end of May 2014. Test flights will take place at the Payerne airfield in Switzerland until the end of summer. The first official attempt is scheduled to start March 2015 from the Gulf area.
Although the route has not been fully defined yet, it is known that the flight will total 35,000 km over (in order) the Arabian Sea, India, Myanmar, China, the Pacific Ocean, the United States, the Atlantic Ocean, and Southern Europe or North Africa, before closing the loop and returning to the point of departure. The round-the-world flight will total 25 days and nights of actual flying (500 hours) over about four months. Five stops will occur along the route so Piccard and Borschberg can alternate as pilots.
Flying up to five or six nights in a row in a 3.8m3, unheated, unpressurized, single seater cockpit presents its own set of challenges.
“We have an airplane which is fully sustainable in terms of energy, and our challenge now is to make the pilot sustainable as well,” says Borschberg.
The cockpit has enough space for oxygen supplies (six bottles), food and survival equipment. The parachute and life raft are packed into the back of the seat, which doubles as a reclining berth and toilet. High-density, thermal insulation in the cockpit protects the pilot from extreme temperatures ranging from -40°C to +40°C.
However, it’s not just spatial challenges these pilots will be facing, but also mental and medical. Piccard and Borschberg were taught self-hypnosis and meditation techniques to aid them in maintaining concentration and vigilance. To meet the dietary restrictions, 5.2lbs of food and 84.5oz of water per day, physicians and specialists of high-altitude medicine devised a science-based, personalized nutrition plan for each pilot and will provide medical advice before and during the flight.
A multi-disciplinary team at the Mission Control Center simulates all possibilities, finds the right combination of weather patterns, clears the way for the aircraft to enter controlled airspace and prepare for landing at international airports, and provides continuous transmission of technical parameters via a satellite data-link to ensure constant contact with the pilot.
Even with years of extensive flight experience, due to the dynamics of the plane, Piccard and Borschberg had to re-learn flight tactics, piloting skills and aerodynamics virtually from scratch using a flight simulator developed specifically for Solar Impulse 2.
The plane has a maximum bank angle of 5°, and a vibration into the pilot’s sleeves alerts him if that limit has been exceeded. Additionally, a monitoring system continuously checks the autopilot for anomalies or any other exceeded safe limits.
Partner Focus: ABB
In an April press release, power and automation technology group ABB announced its support for Piccard and Borschberg in their round-the-world solar flight attempt. Together with the Solar Impulse team, ABB is working on developing key technologies related to solar, storage and low voltage products.
“ABB and Solar Impulse are perfect partners with a shared vision of addressing the world’s energy challenges through groundbreaking technological innovation,” says Maxine Ghavi, head of ABB’s Solar Initiative. “Solar Impulse shows what’s possible when one is willing to venture beyond the conventional boundaries, while ABB shows how breakthrough innovation can be transformed into tangible technologies and solutions for a better world.”
With the official unveiling of Solar Impulse 2 on April 9, and test flights already taking place, Piccard and Borschberg have their hands full preparing for Solar Impulse’s maiden flight, but that doesn’t stop these innovators from having even bigger ideas for the future.
“One [idea] that will keep me busy for a long time [is] not only having a plane that flies around the world without fuel with [the] Solar Impulse program, but [to] use this program and this technology demonstration to encourage more people to use those technologies that we use in our aircraft in their everyday lives,” says Piccard.
As seen in many recent reports by the Department of Energy, SNL Energy and GlobalData, solar power is a market on the rise. With a record number of PV installations in 2013, 680 MW installed in Q1 2014, and an estimated 5.3 GW expected to come online by the end of 2014, Piccard and Borschberg couldn’t have planned a better time to show the world solar power’s endless possibilities.
“The undisputable fact is that the global energy demand will continue to grow and much of this demand comes from developing and emerging markets,” says Ghavi. “The question is how to decouple economic growth from environmental impact and the obvious answer is the increased use of renewables, including solar.”
Piccard and Borschberg’s answer: Solar Impulse 2.
“Our goal is to show that it is now possible to achieve things considered impossible without fossil fuels,” says Piccard. “In today’s world we have to cultivate the pioneering spirit to liberate oneself from those certainties and habits that hold us prisoner to old ways of doing and thinking.”
“We would like people to remember that it was useful; that it contributed to changing certain behaviors,” he continues. “If because of Solar Impulse more people save energy and start using new technologies and clean energy sources, and that they understand that sustainable development is an exciting adventure, it will be a great success.”
Keep up to date with all of Solar Impule 2’s recent developments through Twitter: @solarimpulse and #Si2.