Volvo Car Group (Gothenburg, Sweden) has implemented a revolutionary concept for lightweight, structural energy-storage components that would permit automakers to integrally mold battery components within composite auto body-panel laminates. The technology, designed to improve the utility and efficiency of future electric vehicles (EVs), was developed during a research project funded and overseen by the European Union. Imperial College London took the academic lead and worked with eight other major participants, including Nanocyl (Sambreville, Belgium) and Cytec Industrial Materials (Heanor, Derbyshire, U.K.), with Volvo as the sole participating auto OEM. (CompositesWorld first covered the project in February 2010: “Composites partnership researches body/battery combo for electric cars,” short.compositesworld.com/t3ZObYv6.)
The project team identified a feasible solution to the weight, size and cost disadvantages associated with the heavy, bulky batteries used in hybrid-electric and plug-in electric cars today: a material consisting of carbon fiber combined with carbon nanotubes.
The focus of the project was on the combination of carbon fiber laminates that contain carbon nanotubes combined with a polymer resin. The result, says Volvo, is a very advanced nanomaterial — in effect, structural supercapacitors. The laminate is layed up, shaped and then cured in an oven; the nanotubes are integrated within the component skin. This material can be molded to replace existing components on the vehicle, such as body panels, and then be used to charge and store electrical energy (see diagram). According to Volvo, the material is recharged and energized by the use of brake energy regeneration in the car or by plugging into the electrical grid. Like a conventional battery, it supplies power to the EV’s electric motor. That said, experimental work has shown that this material not only charges and stores energy faster than conventional batteries, but it is also suitable for structural applications. The research project took place over nearly four years and has now been realized in the form of body panels on a Volvo S80 experimental car.
Volvo has evaluated the technology by creating two components for testing and development: a boot (trunk) lid and a plenum cover that were tested on the S80. The boot lid is a functioning storage component that has the potential to replace the standard batteries in today’s cars, yet it’s lighter than a standard boot lid, saving weight. The new plenum has demonstrated that it can also replace both the rally bar, a strong structural piece that stabilizes the car in the front, and the start-stop battery. This saves more than 50 percent in weight, compared to previous materials, and is powerful enough to supply energy to the car’s 12-volt electrical system.
Volvo says that “complete” substitution of an electric car’s components with the new material could cut the overall weight by more than 15 percent, which would save money and result in lower environmental impacts. The carmaker adds that EVs play an important role in its future product portfolio, and it will continue the work.