Volvo Car Group testing lightweight structural energy storage material applied in trunk lid and plenum cover
Volvo Car Group—the only automaker participating in a 3.5-year EU-funded project developing a prototype material which can store and discharge electrical energy and which is also strong and lightweight enough to be used for car parts (earlier post)—has created two components for the testing and further development of the technology. These are a trunk lid and a plenum cover, tested within the Volvo S80.
The material combines carbon fibers and a polymer resin, creating a very advanced nanomaterial, and structural supercapacitors. The material can be moulded and formed to fit around the car’s frame in locations such as the door panels, the trunk lid and wheel bowl, substantially saving on space.
In one of the papers related to the work, a team from Imperial College London (the academic lead on the project), noted:
To date, two main strategies have been applied to the fabrication of multifunctional structural energy storage devices. One straightforward approach is a multifunctional structure, physically embedding energy storage devices into conventional fiber-reinforced composites or using structural composite laminates as packaging to protect the devices. Such devices have been reported to operate normally under low mechanical loads. However, this approach offers only modest mass/volume savings and issues such as delamination at the device/ composite interface may be limiting.
An alternative, potentially more beneficial route is to produce truly multifunctional materials, consisting of multifunctional composite constituents that simultaneously and synergistically provide structural and electrochemical energy storage functions. Earlier work has been focused on multifunctional structural batteries and dielectric capacitors. The concept developed in this work is that of multifunctional structural supercapacitor composites, initially focusing specifically on electrical double layer capacitors (EDLCs), but with an obvious possible extension to pseudocapacitor devices, incorporating redox active elements.—Qian et al., 2013b
As applied in the S80 components, supercapacitors are integrated within the component skin. This material can then be used around the vehicle, replacing existing components, to store and charge energy.
|Close up of the trunk lid carbon fiber composite. Click to enlarge.||Placing the structural super capacitor laminates on the outer skin of the trunk lid. Click to enlarge.|
The material is recharged and energized by the use of brake energy regeneration in the car or by plugging into the electrical grid. It then transfers the energy to the electric motor which is discharged as it is used around the car.
The breakthrough showed that this material not only charges and stores faster than conventional batteries can, but that it is also strong and pliant.
The trunk lid is a functioning electrically powered storage component and has the potential to replace the standard batteries seen in today’s cars. It is lighter than a standard boot lid, saving on both volume and weight.
The new plenum demonstrates that it can also replace both the rally bar, a strong structural piece that stabilises the car in the front, and the start-stop battery. This saves more than 50% in weight and is powerful enough to supply energy to the car’s 12V system.
Volvo suggests that the complete substitution of an electric car’s existing components with the new material could cut the overall weight by more than 15%. This is not only cost-effective but would also have improvements to the impact on the environment.
The project included Imperial College London as the academic lead partner along with seven other major participants in addition to Volvo: Swerea Sicomp AB; Bundesanstalt für Materialforschung und-prüfung BAM; ETC Battery and FuelCells; Inasco; Chalmers (Swedish Hybrid Centre); Cytec Industries (prev UMECO/ACG); and Nanocyl.
Qian H, Diao H, Shirshova N, et al. (2013a) “Activation of structural carbon fibres for potential applications in multifunctional structural supercapacitors”, J Colloid Interface Sci, Vol:395, 0021-9797, Pages:241-248 doi: 10.1016/j.jcis.2012.12.015
Qian H, Kucernak AR, Greenhalgh ES, et al. (2013b) “Multifunctional structural supercapacitor composites based on carbon aerogel modified high performance carbon fibre fabric”, ACS Appl Mater Interfaces, Vol:5, 1944-8244 doi: 10.1021/am400947j