In a new ‘insights from industry’, Martin Kreuter, Solar Impulse project leader at Bayer MaterialScience, talks to G.P. Thomas about what materials are playing an important role in the next generation of aviation.
GT: Could you please provide a brief introduction to the industry that Bayer MaterialScience works within and outline the key drivers?
MK: With 2011 sales of EUR 10.8 billion, Bayer MaterialScience is among the world’s largest polymer companies. Business activities are focused on the manufacture of high-tech polymer materials and the development of innovative solutions for products used in many areas of daily life. The main segments served are the automotive, electrical and electronics, construction and the sports and leisure industries. At the end of 2011, Bayer MaterialScience had 30 production sites and employed approximately 14,800 people around the globe. Bayer MaterialScience is a Bayer Group company.
GT: Bayer MaterialScience is currently involved in the solar impulse project – could you provide a background to this project and what it involves?
MK: Bayer MaterialScience is an official partner of the Solar Impulse project and has been since 2010. A research team comprising of around 30 individuals is working on the project in the laboratories of Bayer MaterialScience, on a range of innovative ideas for lightweight construction and energy efficiency. In the next model of the solar-powered aircraft, the proportion of Bayer materials is set to rise again significantly. The aim of the collaboration is to develop and test tailor-made, lightweight, high-performance materials.
The objective of researchers at Bayer MaterialScience is to make the second Solar Impulse aircraft even stronger and lighter than its predecessor, the HB-SIA. The successor model, the HB-SIB, is to circumnavigate the globe in 2015 in five stages.
In September 2012, Bayer MaterialScience became the official partner to have its logo on the aircraft.
GT: How has Bayer specifically been involved in this project and how has this role progressed?
MK: Solar Impulse could prove ground-breaking for Bayer MaterialScience because the company can use this project to implement the very things already anchored in the Bayer philosophy, ‘Science For A Better Life’, meaning conducting research to bring about change and make life better and more progressive. The Solar Impulse project is not about using a ‘cleaner’ energy; it’s about using ‘absolutely clean’ energy. Through the use of innovative materials, we can help find solutions for future, such as the growing population or increasing mobility.
In other words, BMS is addressing exactly those issues the company has already defined as global megatrends. They basically relate to challenges in the fields of climate protection, technology, mobility, living and health. These areas are affected by change for a variety of reasons, including demographic shifts, the finite nature of natural resources, but also the demands of an aging population. The technologies developed for the Solar Impulse project are transferable to many other areas of everyday life, such as energy efficiency in computers, refrigerators or automotive applications.
Above all, we are interested in showing that the chemical industry is not the problem. It can also play a part in helping to solve challenges such as climate change.
GT: Has the aircraft made any flights so far? How successful have these been?
MK: On July 7th, 2010, the aircraft made the first night flight in the history of solar aviation. In September, 2010, the aircraft flew across Switzerland, landing at the international airports of Geneva and Zurich. Under the patronage of the European Communities, Solar Impulse flew to Brussels and to Paris-Le Bourget, where it featured as a ‘guest of honour’.
The aircraft flew to Spain and then to Morocco in 2012 and back to Switzerland, in a mission to fly across the Mediterranean at the invitation of King Mohammed VI to promote the creation of the world’s largest thermo-solar power generating complex at Quarzazate.
The plan to flight around the world will be in 2015.
GT: When will the new aircraft be complete and when is it scheduled to make its first flight?
MK: The plan is to complete the second plane in 2013 and to do the first test flights in 2014.
GT: What modifications are being made to the second model of the aircraft?
MK: As with its predecessor, the major objective of the work on the second plane is to develop and test tailor-made, lightweight, high-performance materials. One of the challenges now is to develop and manufacture a complete lining for the cockpit. The entire construction may weigh no more than 29 kilograms, but must still be capable of withstanding the enormous temperature differences encountered during flight. All our employees involved in the project are excited about the challenge and are giving their best to find solutions. Chemists, lab techs, engineers and technicians at Bayer are conducting research and development works on everything from the design to formulation development and component production. Another area of focus for the Bayer experts in the Solar Impulse project is the production of suitable coatings to improve the properties of the fabrics on board. Lightweight, weather-resistant coatings for covering the wings are particularly important here.
The proportion of Bayer materials in the second aircraft will rise again significantly. That is why the company is working flat out on the development of further ultralight materials. The researchers at Bayer MaterialScience are now able to make materials even more stable by reinforcing the epoxy resin with tiny nanometer-sized tubes of carbon atoms linked together like a honeycomb. These are known as carbon nanotubes, or CNTs, and are marketed by Bayer under the brand name Baytubes®. The CNTs will significantly improve the mechanical properties of the material and help to make the aircraft lighter.
GT: Where will the solar cells be mounted on the aircraft? Have these been specially modified in any way?
MK: There are currently 12,000 cells on HB-SIA’s wings and horizontal stabilizer. The next generation aircraft, HB-SIB, will have 15,000 of them. This might not sound so impressive until you know that the panel building process is all handmade.
GT: Baytherm Microcell is being used as insulation on the flight – could you explain the theory behind this innovative insulator and the benefits of using this?
MK: The innovative polyurethane foam Baytherm Microcell® will be used as insulation in certain places. The material offers significantly greater insulating performance than the current standard because Bayer researchers were able to shrink the pores in the foam by an additional 40 percent. Highly efficient insulation is particularly important for the aircraft because it must withstand temperature fluctuations between minus 50 degrees Celsius at night and plus 50 degrees during the day.
GT: How Have Baytubes® carbon nanotubes been utilised in the new aircraft? What are the benefits of using these?
MK: Carbon nanotubes (CNTs) are a material class that is expected to revolutionize the properties of plastics and ceramics. Li-ion batteries, too, benefit from the conductivity, mechanical strength and surface properties of CNT, which significantly enhance battery life and performance. This is a particular advantage for equipment with high energy requirements that also needs to be lightweight – such as car batteries, for example in hybrid vehicles.
Comprehensive product support enables the company to thoroughly test the safety and environmental compatibility of its nanomaterials. Bayer MaterialScience boasts sound know-how regarding the safe handling of materials such as Baytubes®. We are also involved in numerous national projects and working groups investigating the safety aspects of nanomaterials. Research into the safety of CNT (and nanomaterials in general) is a key part of its innovation strategy.
Nanotechnology is decisive for the success of the project, especially for the development of innovative and lighter material solutions to lower energy consumption. One key factor is to ensure that the material reinforced with Bayer nanotubes does not expand too much when subjected to heat. The team is currently working flat out to further optimize this property, because the aircraft must be capable of withstanding enormous temperature differences. Daytime temperatures in full sunshine can reach nearly 70 °C. That means about minus 50 degrees Celsius. When dusk begins to fall, the Solar Impulse aircraft is at an altitude of 8,700 meters, where the outside temperatures are an arctic-like -80 °C. When different materials are combined, temperature fluctuations like this can have fatal consequences. If the materials expand to varying extents, the composite material can become cracked and break.
GT: Could solar power one day be used in commercial flights?
MK: Solar Impulse is not about transporting people but about transferring messages.
In general solar powered airplanes are possible (just look on what is happening in politics with all the CO2 white papers and in other industries such as automotive). All commercial airplane makers such as EADS and Boeing are heavily investigating on emission-free electric propulsion. Only difference to Solar Impulse, it is very unlikely that the (solar) energy will be harvested on-board and in the air. A more realistic approach is to harvest the energy on the ground and then put it into the airplane (directly in batteries or indirectly via energy conversion to alternative fuels such as hydrogen). We are sure that some aviation people might argue that they are already using the sun today, just by growing crop for biofuels which is used right away in existing airplanes.
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