But the changes made to the new lightweight urban electric concept vehicle is more of an exercise in what's possible rather than a way to evolve the i3 and i8 into a broader i family of vehicles. Even so, what we see here is interesting, since SABIC found all sorts of new ways to take weight out of the car as part of the Visio.M (Visionary Mobility) project, which was first announced in 2012.
Let's start with the window material, which as you might guess from the quotation marks above, is not made of glass but is instead SABIC's Lexan polycarbonate (PC) resin plastic. The lower weight (the PC helps shed about 29 pounds) adds two miles of range while the PC resin has better thermal conductivity compared to glass and so does even more because the HVAC system can be more efficient. According to SABIC's computational fluid dynamics analysis, an extra 9-10 miles of range, in fact. Without the battery, this concept weighs just 992 pounds. Remember, BMW already made a lot of weight-reduction measures in the i3 thanks to carbon fiber reinforced plastic, so to make the "glass" lighter would only help boost efficiencies on a production vehicle that uses a resin like this. Read more below.
Munich, October 20, 2014
Today, at the Technical University of Munich (TUM), BMW, Daimler, TUM scientists and a consortium of industry participants showcased a lightweight urban electric concept vehicle with various advances, including an all-plastic design of the car's windows. The windows are made of LEXAN resin, a polycarbonate (PC) material, and coating technologies from SABIC, a leading developer of PC glazing for automotive windows and many other thermoplastic solutions for the automotive industry. This approach to the windows helps keep overall vehicle weight to a minimum and contributes to important gains in energy efficiency and extended range, while also delivering other benefits like improved acceleration, vehicle handling and security. Today's announcement comes at a time when automakers worldwide are striving to improve electric vehicle range and efficiency.
Use of SABIC's LEXAN resin compared to conventional glass for the car's windows reduces weight by over 13 kilograms and extends the vehicle's driving range by up to two kilometers for a single battery charge. PC's superior insulating properties reduce demands on the car's heating and air conditioning (HVAC) system and make possible up to 15 additional kilometers in extended range.
"A significant share of an EV's energy consumption depends on its weight," said Stefan Riederer, BMW Research & Technology. "A low vehicle weight allows for smaller and lighter battery designs, in addition to lighter designs of the electric motor, the chassis and other components. The weight savings that we were able to achieve across our EV concept, including the significant drop in weight from the windows with SABIC's materials and development support, allowed us to significantly reduce the amount of energy required to move the car and meet the design intent of the vehicle."
The lighter weight of the PC windows contributes to a lower center of gravity, which tends to have a favorable effect on the vehicle's handling and stability. The reduced weight also means that the vehicle requires less energy to accelerate at a quicker rate. In terms of vehicle security, LEXAN resin has up to 100 times the impact resistance of glass. As a result, the concept car's windows can reduce risk from theft, an important feature for urban cars.
The unveiling of this electric concept vehicle is the culmination of over two-and-a-half years of research and development as part of the Visio.M (Visionary Mobility) project. This joint effort, funded by the German Federal Ministry of Education and Research (BMBF), has focused on producing an exceptionally light electric car that is efficient, safe and mass-marketable. The consortium, in addition to BMW, Daimler and TUM, includes Autoliv, Germany's Federal Highway Research Institute (BASt), Continental, E.ON, Finepower, HYVE, IAV, InnoZ, Intermap Technologies, LION Smart, Neumayer Tekfor, Siemens, Texas Instruments and TÜV SÜD.
The EV features a 15kW electric motor and a weight of 450 kilograms (without battery), standard requirements that allow the vehicle to meet the new European regulatory category L7e (heavy quadricycles).
"The Visio.M concept is a good example of the important contributions that a light-weight enabler like PC glazing can make for global automakers and consumers," said Scott Fallon, general manager, Automotive, SABIC's Innovative Plastics business. "PC glazing continues to prove – in various demonstrations like the Visio.M and in applications that are in production vehicles today – that it can contribute very meaningfully to improved vehicle efficiency and performance. SABIC remains committed to supporting the adoption of this technology so automakers can rise to the challenges of light-weighting their vehicles and take advantage of all the benefits that PC glazing offers."
The Visio.M concept features PC-based front side moving windows, rear quarter windows and a backlite, all produced with LEXAN resin and coating technologies that enable fulfillment of regulatory requirements, including those for glazing located ahead of the B-pillars, which are required for driver visibility. The moving windows use SABIC's proprietary EXATEC™ E900 coating, an advanced plasma coating that meets abrasion resistance requirements and enhances weatherability. Although not required to homologate the backlite, the same plasma coating would also enhance the durability of this window, which includes a wiper. The Visio.M windscreen is also produced with LEXAN resin, recognizing the potential for changes in European legislation which would allow PC to be used in this window application. Current legislation permits PC use in all automotive glazing applications, except the windscreen.
Weight savings, including those that come from PC glazing, can favorably influence the production cost and affordability of electric vehicles. Energy storage systems (batteries) are one of the most expensive parts of an EV. Current EV architectures are based largely on heavier petrol-powered models, which feature expensive, heavy battery packs. In contrast, a small, light-weight EV does not require the same energy storage capacity, which allows a vehicle manufacturer to use a smaller, cheaper battery system and effectively help improve the EV's affordability.
The thermal efficiency benefit, which enables up to 15 additional kilometers in range, is a result of PC's five-fold lower thermal conductivity compared to glass of the same thickness. This lower thermal conductivity reduces demand on the vehicle battery from the HVAC system. SABIC used computational fluid dynamics (CFD) analysis to validate the extended range data.
The Visio.M windows were designed to use PC or glass for testing and comparison purposes. SABIC says that if the windows had been designed for PC alone, additional energy efficiency gains could have been achieved. This is because of PC's greater shape flexibility compared to glass, which allows for curvatures, 3D styling and aerodynamic features that can minimize drag. The greater design freedom from the use of PC can also enable part consolidation and integration possibilities with traditionally separate components such as pillars, mirrors, cameras, rear lighting and spoilers.
More information on SABIC's solutions for the automotive industry can be found on the website (www.sabic-ip.com/automotive). For technical product inquiries, please contact us at www.sabic-ip.com/prtechinquiry.