SPECIAL REPORT SOLAR IMPULSE IN ASSOCIATION WITH

Record attempt has solar flair Jean Revillard/Rezo.ch

An idea spawned a decade ago finally becomes a future. When Bertrand had his vision, he had no solution, no resources, no funding reality as Solar Impulse prepares for the first round- and no team; he just had the strong will of saying ‘I will do it’. It proves that when you the-world flight by a plane producing zero emissions pull all your resources together you can re- ally achieve the impossible. ANDY BRICE LONDON of 50 engineers, 80 partners and around 100 “Chemistry was absolutely necessary to advisors and suppliers in a bid to embark build this plane and this project is providing oaring above an airbase in Payerne, on the 35,000km flight around the world. outstanding visibility – not only for Solvay, Switzerland, one July morning in The journey started in 2003 when Piccard Bayer MaterialScience and all the partners 2010, a solar powered aircraft was was invited to speak at an internal event for but for chemistry as a whole,” says Michel. about to make history. Some 26 Belgian-headquartered chemical group Solvay, one of four main partners sup- hoursS later, the prototype plane became the Solvay. Born to a family of pioneers and ad- porting the project, has invested some 15m first to stay airborne both day and night venturers, he talked of his successful round- Swfr (€12.3m, $16.8m) into Solar Impulse using no fuel and producing no emissions. the-world flight by air a few years these past ten years – and it has proven an Over 500 hours of flights – and eight FAI earlier. The record-breaking Orbiter 3 chal- extremely worthwhile investment, he adds. (Fédération aéronautique internationale) lenge had quite literally proven that the sky “This is something the whole industry World Records – later, and the team behind was the limit for flights of fancy, and affirmed should be doing,” says Richard Northcote, Solar Impulse has since completed the con- his vision that a trip around the globe might head of sustainability at German polymer struction of a second, larger plane and is be possible without expending fossil fuels. producer Bayer MaterialScience, an official counting down to its biggest challenge: cir- The Solvay management team, inspired by partner on the project. “Solar Impulse has cumnavigating the globe using only the his presentation, discussed the project’s po- proven that companies working closely to- power of the sun. Solar Impulse 2 was un- tential and the Solar Impulse dream took off. gether can come up with even better solu- veiled to the public on 9 April 2014 and took tions. Partnerships like this are really bene- to the skies for its maiden flight on 2 June. ACHIEVING THE IMPOSSIBLE ficial – and the industry should start to do Getting such an ambitious project off the “If there is one word which defines this more of that in terms of addressing the prob- ground was certainly no easy undertaking, kind of project, it’s ‘inspiration’,” says lems that society faces. I think by putting requiring innovative materials and the Claude Michel, head of the Solvay Solar pressure on companies to come up with combined efforts of some of the world’s Impulse Partnership. “Our world is mov- even better solutions than we appreciate leading companies. Over the past decade, ing fast and there are many crises and diffi- today is a good thing – it drives innovation. Swiss explorer and engi- culties but Solar Impulse gives the younger “There is always a danger that industry neer André Borschberg have steered a team generation hope and a positive view on the will stick its head in the sand instead of

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­taking a more long term and therefore sus- tainable approach. There are alternatives to the way we look at technology today – we’re proving that this can be done,” he says. “We need to invest in alternative and renewable energies, look at lighter materials, and focus on sustainability.” “The project and partnership is a flag- ship for innovation and sustainable devel- opment,” says Michel. “The values we have in our company are very similar to those carried by the Solar Impulse project: innovation, a pioneering spirit, respect for planet, and a respect for people. We are not just providing products for the project, we are providing solutions. As a techno- logical partner we have been heavily in- volved in the co-development of the re-

search; we have the technology, products Jean Revillard/Rezo.ch and chemistry to help make the plane fly.” The record-breaking trip showcases the many technologies and materials Central to Piccard’s dream was chang- ing people’s perception towards energy The exact route of the plane is yet to be scrutinized and individually assessed savings and renewables, and to prove confirmed but the journey will be com- by the Solar Impulse team to ensure it that our dependency on fossil fuels pleted in stages, allowing the pilot to rest met their strict requirements. could be reduced – all by harnessing ex- between legs and the iconic aircraft to be “The project made us look at things isting technologies. seen by as many people as possible on the differently,” says Northcote. “There were The key objectives for the team were ground. Its arrival in carefully selected lo- a number of characteristics we had to to make the aircraft as light as possible cations around the globe will help spread meet but the weight requirements really while ensuring optimal performance the message of sustainability and innova- forced us into a new way of thinking. and efficiency. The materials specified tion, which is so central to the project. “If you go back through history, if you for the project were therefore integral to “The hops are very important for look at the space shuttle or moon land- its success and required close collabora- spreading the message – it’s just as im- ings, for example, so much innovation tion between the many companies in- portant as the actual flight round the came out of these incredible projects volved in its construction. world,” adds Northcote. “When Ber- and so many inventions contributed to trand came up with this idea, people the success of these dreams. Now we CAREFUL SELECTION PROCESS said it couldn’t be done; he wanted to take them for granted, of course, as they Built from a myriad of materials common prove the impossible was possible. For a are part of our everyday life.” to applications in the automotive, aviation plane to take off with no energy and land As an example, Northcote points to and refrigeration sectors, Solar Impulse with a full battery, it’s quite spectacular. Bayer’s microcellular foam used to in- uses of a range of specialty polymers, engi- “The great thing is that once you get sulate the doors to the redesigned neering plastics, carbon fibre composites, your products onto the plane and get cockpit. Solar Impulse marks its first foam insulation, lubricants and coatings – them flying around the world, people application but he suggests it will not all carefully selected because of their me- see the value of what chemical compa- be too long until exactly the same foam chanical properties and weight. nies can do in terms of achieving these will be taking the latest range of refrig- The sun’s rays will be absorbed by an dreams. Then they start to realise that erators to new energy saving perfor- array of photovoltaic panels to charge on- the products that are helping to make mance levels. board batteries and allow the plane to fly this whole voyage successful are the “There is a growing consumer-based both day and night. To compensate for the same as those they can buy in everyday pull for more sustainable products and weight of the batteries, the team strived to household items,” he says. new legislation keeps pushing for lower make every fixture and fitting as light- Despite investing so much time, energy consumption and lower green- weight as possible, while retaining the money and manpower in the project, house gas emissions,” he says. structural integrity needed to withstand neither company has been guaranteed a Michel says there has been a similar the harsh conditions at high altitudes. place for all their products on the plane. ripple effect throughout Solvay’s business, Described as a Flying Laboratory, Solar Each and every material was carefully with the techniques and research learned Impulse showcases innovative technolo- on the powertrain and lightweighting of gies and materials on a global stage. “Solar Impulse has the plane, in particular, being relevant to Launching in March 2015, the plane the automotive and aviation sectors. will leave its base in the Arabian Gulf proven that companies “The mobility megatrend means that and head east, via India and working closely together all manufacturers of planes or cars are to China. After a five day flight across can come up with even looking to develop lightweight solu- the Pacific Ocean the route will take tions,” says Michel. “Solar Impulse’s de- Solar Impulse through the US and better solutions” velopment has really been a springboard across the Atlantic and Europe before RICHARD NORTHCOTE for this, whether it’s in the structure of returning to the Gulf region. Head of sustainability, Bayer MaterialScience the plane or in the devices inside.” ■

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ANDY BRICE LONDON however, and it becomes clear that there er, an even more ambitious attempt to fly have been innumerable enhancements a solar plane around the world required itting in its huge hangar in to assist the plane on its epic journey the project’s engineers to head back to the Switzerland, it may appear that around the globe. drawing board and design a bigger, more the latest incarnation of the The original plane powerful machine not only capable of Solar Impulse plane has barely was a resounding suc- crossing continents and oceans, but of changedS from its prototype form. Most of cess, proving the con- comfortably carrying a pilot for up to five its slender frame is still covered in pho- cept of flight powered days at a time. And it had to still remain tovoltaic panels, the nose of the diminu- only by the sun. Howev- as light as possible. tive cockpit pokes out from beneath its wings and the plane retains its trade- mark silver finish. Look a little closer,

Wings Engineers placed 144 ribs at regular 50cm (20 inch) intervals along the wings, providing a rigid structure capable of withstanding the harsh conditions of flight. A flexible film was used to fill gaps between the solar cells and aid aerodynamics. At 72 metres, the wings are wider than those of a Boeing 747.

Solar Impulse

ICB_230614_solar-gatefold.indd 3 25/06/2014 15:22 To withstand the gruelling conditions zontal stabilizer is home to over 17,000 With weight such an important ele- and cope with the longer flight times of a monocrystalline silicon photovoltaic cells ment of the project, the team often had to round-the-world attempt, Solar Impulse 2 to soak up the sun – almost 50% more than make tough decisions to reject materials (SI2) had to be larger and more robust than were used previously. The panels are pro- that would otherwise have been suitable, its predecessor. Despite its size, however, tected by Solvay’s Halar ECTFE (ethylene says Bernd Rothe, Solar Impulse project the new plane weighs only around 2,300kg chlorotrifluoroethylene), a thin fluorine lead, Bayer MaterialScience. “For Solar – more than the prototype’s 1,600kg but copolymer film that at only 17 microns Impulse, the main priority was to be as still little more than a standard family car. thick is far thinner than the 26 microns of light as possible. We developed a glue to SI2 may boast a wingspan of 72 metres and the alternative film that was considered. attach a film to the top of the solar cells be wider than a Boeing 747 commercial The result is a weight saving of around but the Solar Impulse team said no as our but its engines only provide the 35% without compromising the electrical solution was 28g/m2. Even though it had power of a motorbike. performance. excellent properties and transmission, During the challenge SI2 will soar to The cells themselves are among the best and it was a faster process, the existing 8,500m (27,000ft) during the day to absorb currently available and are only 135 mi- solution was 25g/m2. The weight is the the sun’s rays and descend to 1,500m at crons thick, equivalent to a single human main factor for them.” night to conserve energy. A 300m2 surface hair. They are UV resistant and waterproof, More time in the air requires more en- spread over the wings, fuselage and hori- offering vital protection from the elements. ergy storage and the prototype’s larger sib-

Solar Cells Over 17,000 ultra-thin photovoltaic cells cover 300m2 of sky-facing surfaces to absorb as much of the sun’s energy as possible and power the flight. A special film coating ensures that they are UV resistant and waterproof.

Fuselage Gondolas Larger than the prototype, 83% of the new plane is made The four carbon fibre gondolas from light carbon fibre honeycomb structure, which beneath the wings incorporate a strengthens the structure while significantly lowering the 17.5hp motor, lithium polymer battery weight. This technique is already used in competitive yacht and propeller. Specially-formulated racing. The body’s silvery appearance uses the same insulation foam protects the batteries coating that is used on the FIFA World Cup football. from the fluctuating temperatures (-40oC to +40oC) in flight. The motors are up to 94% efficient.

ICB_230614_solar-gatefold.indd 4 25/06/2014 15:22 ling now plays host to 630kg of lithium that has been used on the Adidas Brazuca, polymer batteries – up from 400kg in its “Not only have the materials the official match ball of the 2014 FIFA predecessor. The batteries are hidden be- been improved for the World Cup. The company also provided neath the wings within four gondolas that second plane but the the adhesives that hold the textile fabric in also house 17.5hp engines. The team was place underneath the wings. able to wring out as much power as possi- techniques have evolved” Even the landing gear has undergone an ble thanks to a fluorinated polymer from CLAUDE MICHEL overhaul, helping to shave a few pounds Solvay. As a result, the energy density is Head of the Solvay Solar Impulse Partnership off the plane’s load, says Michel. The met- optimized to 260 watt hours/kg (Wh/kg) – als used in the pneumatic cylinders that far higher than the 180Wh/kg targeted for raise and lower doors have been replaced the original plane. Solef PVDF (polyvi- Solar impulse will help us make advances by a polymer, Ixef PARA (polyarylamide) – nylidene fluoride) is used as a binder for with electric cars.” marking the first time a pneumatic cylinder both electrodes and reduces the weight of Bayer MaterialScience provided the in- or actuator has ever been entirely made of the batteries, while a monofluoro-ethyl- sulation – a lightweight yet strong foam plastics. This innovation proved 20% ene carbonate solvent helps to improve that ensures the batteries are protected lighter than the original version. the ion flow and helps the batteries to from the extreme -40oC to +40oC tempera- “Not only have the materials been im- carry more current. tures experienced mid-flight. The polyure- proved for the second plane but the tech- “The main bottleneck was not really the thane (PU) used for the insulation saves 70 niques have evolved too,” says Michel. energy capture,” says Claude Michel, head times more energy than is used to make it. “For example, the fasteners, bolts and of the Solvay Solar Impulse Partnership, Over 80% of the plane’s body is made screws – all made from high performance “the big challenge was the intermediate en- from ultralight composite materials, pro- plastics – were machined in the first plane ergy storage. You need to capture renewa- viding an incredibly strong frame at a frac- but there was some brittleness because of ble energies and transform them into elec- tion of the weight a conventional fuselage. this process. For the second plane we used tricity but most of the time it’s produced Rather than conventional epoxy-enhanced a moulding process, which means better when you don’t need it. We had to find the solid carbon, a lighter carbon sandwich quality and a more consistent performance. right solution. We contributed to their im- structure was specified at only 25g/m2. Solvay also developed a new lubricant, provement through our electrolytes, addi- Its distinguishing trademark silver finish which will reduce the amount of mainte- tives, binders and separators and I’m con- is thanks to the Impranil coating from nance needed – very important for long vinced that the progress we’ve made with Bayer Materialscience – the same coating duration flights.” ■

Windscreen Hinge Polycarbonate sheets were specified for the The specially-made hinge that window, boasting a glass-like appearance but attaches the door to the cockpit with better properties and at a lower weight. A is produced using polyurethane special coating prevents the windscreen from carbon fibre composite – fogging up and obscuring the pilot’s view. lightweight but extremely strong.

Insulation The plane’s 3.8m3 cockpit is designed to accommodate a single pilot for up to five consecutive days between legs – enough to travel across the Atlantic and Pacific Oceans. To Door protect the pilot, a unique The door to access the cockpit is made foam was specified to from a special polyurethane rigid foam insulate the cabin – and at a with a 40% smaller cell size, reducing fraction of the weight of thermal conductivity by up to 10%. conventional materials.

ICB_230614_solar-gatefold.indd 5 25/06/2014 15:22 IN ASSOCIATION WITH Visionary design or a little over a month – except for a few brief stopovers – Bertand Piccard or fellow pilot André Borschberg, will be con- F fined to a cockpit measuring only 3.8m3. From here they hope to steer the plane into the history books and become the first to fly around the globe using only . The new cockpit is significantly larg- er than that used in the original plane, redesigned to resist the rigours of flight at altitudes of 8,500m, as well as ex- treme temperatures, for up to five con- secutive days at a time. Such a test of endurance has been made

a little easier thanks to the materials and MaterialScience Bayer technologies that have been carefully se- The cockpit has been given a thorough overhaul for the new record attempt lected and refined over the past few years. Bayer MaterialScience – an official with high mechanical properties led us to sulation and mechanical properties, partner of Solar Impulse since 2010 – de- other projects. The team working on SI2 with low heat transfer and minimal signed the entire cockpit shell, at times had the chance to have a different attack thickness. Bayer researchers succeeded dedicating a 30-strong team to its con- angle – normally we work in specific areas in shrinking the pores in the foam by an struction from May through December and adhere to certain restrictions. For SI2 additional 40%, making its insulating 2012. Although most of the materials had where the main thing was lightweighting, capacity 10% better than the current been successfully trialled on the proto- we had to have a new way of thinking – it standard. As a result, its density was type, every element was optimised and wasn’t about processes, it was about mak- only 27.5kg/m3, far below the require- enhanced, says Bernd Rothe, Solar Im- ing the material as light as possible. We ments in most other end-use sectors. pulse project lead, Bayer MaterialScience. learned a lot. Before long, fridges will be Although a comparatively small com- Although the volume of the cabin in- using these microcellular foams.” ponent, the hinge attaching the door had creased by a factor of three to 25kg, only great significance for Bayer MaterialSci- 2kg was added to the overall weight. STRICT REQUIREMENTS ence too. Made from carbon fibre com- The Solar Impulse team had initially Although some materials did not make it posite and reinforced by PU resin, its stipulated the entire cockpit fairing be re- through the selection process, Rothe in- design broke new ground for the com- stricted to only 20kg, he adds – but this sists their development is being pursued pany, says Rothe. “The hinge may be a proved a little too ambitious: “We made within the company. One such example small part fixed to the door but we our calculations and told them that wasn’t were inflammable rigid foams but Solar learned so much from Solar Impulse possible using current materials. It was a Impulse discounted them because their about on lightweight composites and pragmatic approach and needed a lot of density was above targeted levels. Never- that’s been really helpful for us to make discussions and adjustments; this project theless, says Rothe, Bayer MaterialScience further developments in this area.” certainly had a lot of optimisation loops. It continues to work on them. Similarly, the The automotive industry is increasing- may be heavier but given the extra surface team gained indepth knowledge of carbon ly turning to polycarbonate (PC) as a re- area and the increased functionality, on a fibre composites and is now working placement for glass, the lightweight alter- percentage scale it’s a good result.” closely with other companies that are fo- native reducing fuel consumption and

Beneath the special silvery finish that cused on composite production and is CO2 emissions. This technology proved coats the cockpit lies the inner workings planning a series of projects. ideal for Solar Impulse. PC has a glass-like of the Solar Impulse control hub. From “This was a real gain from the SI pro- appearance and is scratch resistant with here, Piccard will be at the controls and ject because we could test these products the same transmission rate and compara- despite the limited cabin space can re- in a short amount of time,” he says. ble mechanical properties. However, it is cline the chair fully to sleep. “That’s the thing with a flying laboratory also far lighter: glass has a density of 2.6 g/ With external temperatures falling as – you can put new materials inside and cm3 and PC, around 1.2 g/cm3. low as -40oC when airborne, ultra-low carry out some fast-lane tests. Not all of A sandwich of 1mm thermoformed density polyurethane rigid foam pro- them will be positive but you learn just as polycarbonate (PC) sheets is used for the vides insulation and protects the pilot. much about the things that didn’t work.” cockpit window, with a 5mm gap be- “We’ve used Solar Impulse as an inter- Another innovation is the door to the tween the plates offering additional in- nal catalyst for our business and a lot of cabin, made entirely from Baytherm Mi- sulation. A special coating limits fog- other projects were started because of it,” crocell foam. The improved lightweight ging during flight and ensures optimal says Rothe. “Making a lightweight foam polyurethane (PU) foam boasts high in- visibility. ■

ICB_230614_solar-gatefold.indd 6 25/06/2014 15:23 IN ASSOCIATION WITH Plane talking In 2003, adventurer Bertrand Piccard took his dream of building a unique aircraft to André Borschberg, an engineer and pilot, and the Solar Impulse project was born. ICIS asked them about their dream, the hurdles they overcame and what the future holds

What was behind your vision for building a solar aircraft? Bertrand Piccard (BP): Our message high- lights the importance of a pioneering and innovative spirit, especially in the domain of clean technologies. Nowadays, the technological solutions that allow Solar Impulse to fly both day and night are ac- cessible to all and are replicable in every- day life. These are not secret, futuristic technologies. If they were used routinely in our society, we would be able to save 50% of our consumption of fossil energies and to produce half of the rest with renew- able energies. Solar Impulse wants to em- phasize the energy solutions as well as the

environmental and political solutions Solar Impulse | Righetti| Rezo.ch from a decidedly constructive angle in André Borschberg (left) and Bertrand Piccard are ready to make history order to engender enthusiasm and the necessary motivation to leave behind this and Bayer MaterialScience for the air- structural test failed. Pushing the limits pervading fatalism. Aviation makes you plane are key in multiple areas such as is no easy task and the failing of the dream, feeds your passions. A plane that ultralight materials and energy savings, led to a partial rebuilding of it, conse- flies without fuel and achieves something efficiency of components, and solar cells quently causing a construction delay. It everyone imagined impossible will fire and in the energy storage through in- was the first time a final structural test our imaginations and encourage many crease of energy density of the batteries. had failed in the history of the project people to invest in the practical solutions Solvay has 13 products on Solar Impulse and even though it was hard to accept, that our society needs. 2 which enhanced its performance while it’s an extremely valuable learning expe- keeping its weight to a minimum. These rience. What has emerged from this situ- How has support from the chemical products have accessed a host of promis- ation is that the flight around the world, industry made this challenge possible? ing new markets, including solar panel scheduled for 2014, was an extremely André Borschberg (AB): The interesting protection, computer and mobile phone ambitious deadline and that 2015 was thing with Solar Impulse is that most of batteries, baggage compartments on more realistic. Moreover, it has made the partners don’t come from the avia- planes and sustainable solutions in mo- room for some stimulating brainstorm- tion industry. In fact only a few of the 80 bility. Bayer MaterialScience developed ing sessions within the team not only on partners are active in this field. All the among other products the insulation how to use the time gained to improve innovative solutions come from other foam. This new foam has very thin pores, the reliability of the aircraft but also to industries, especially the chemical one. high rigidity and structural strength further emphasize the project’s message They push the boundaries out of their while remaining very light. It allows us to and value. comfort zone and came up with solu- do without a cooling or heating system tions to meet the very specific require- for the batteries and in the cockpit. It is After next year’s flight around ments of Solar Impulse: build an air- also used in the best refrigerators and in the world, what next for the Solar plane with the wingspan of a jumbo jet the construction sector. Impulse project? and the weight of a car capable of flying BP: For the time being our focus is to day and night on solar energy only. What were the greatest technical chal- complete the first round-the-world solar lenges you faced during the project – flight in stages. As long as we have not What were the most significant and how were they overcome? succeeded it will be considered as im- contributions from both Solvay and AB: On 5 July 2012, we were on the possible. Let’s start here and afterwards Bayer MaterialScience and how has verge of rejoicing for an accomplished think of the next step. To bring such an their experience helped? mission until, unexpectedly, Solar Im- endeavour to success you have to keep AB: The solutions developed by Solvay pulse 2’s wing spar cracked and the final full focus on it. ■

ICB_230614_solar-gatefold.indd 7 25/06/2014 15:21 “We are delighted to be an official partner in this “The partnership between our Group and Solar exciting project; through our involvement we will have Impulse translates the confidence we place in the unique opportunity to contribute our know-how and personal commitment, in the spirit of enterprise and in innovative new materials. This support underlines Bayer technological innovation as responses to the challenge MaterialScience’s commitment and responsibility to a of sustainable development. In joining the project we sustainable environment as well as contributing to the also accept another challenge that will take us to the success of Solar Impulse’s great technological challenge.” furthermost frontiers of technology by confronting us with Patrick Thomas the best experts on the planet in each discipline. This CEO of Bayer MaterialScience partnership assumes a definite economic dimension as an excellent springboard for promoting and developing Bayer MaterialScience AG the products, services and solutions that the Group will BMS-COM-D Leverkusen, K12 be in a position to bring to it.” Germany Jacques van Rijckevorsel www.bayermaterialscience.com Member of Solvay’s executive committee.

Solvay Solvay Campus Rue de Ransbeek, 310 B-1120 Brussels Belgium www.solvay.com

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