Supercapacitors are essential in electric vehicles for supplying power during acceleration and for recovering braking energy. High power and sufficient energy density (per kilo) are required for both an effective power system but also to reduce weight. There are several issues to achieve a high performance/low weight power system that need to be addressed by various groups of scientists and engineers in an integrated framework.
The aim of the project is to develop supercapacitors of both high power and high energy density at affordable levels for the automotive industry, and of higher sustainability than many current electrochemical storage devices.
These targets will be achieved by integrating several novel stages:
(a) computer simulations to optimise the power system and the design of the supercapacitor bank for different supercapacitor models, representing the different supercapacitor cells to be developed and tested in this project;
(b) carbon-based electrodes will be used to reduce the amount of rare and expensive metals;
(c) electrolytes of high operating voltage will be used to increase both power and energy density, although the problem is that they have large ions that reduce the effective surface area of porous electrodes due to low diffusivity;
(d) in this case, innovative electrode structures will be developed based on combinations of high surface area/large pore activated carbon electrodes and low resistance carbon fibrous materials or carbon nanotubes; graphene will also be investigated.
(e) novel methodologies will be developed to integrate the innovative electrode materials in the fabrication process for manufacturing large supercapacitors. These will be tested both at small-scale, and in realistic electric car test rig tests, and be cost and life-cycle-assessed.
Supplying more power and energy for electric vehicles
Supercapacitors have become a fundamental part of electric and hybrid cars, delivering rapid bursts of power for acceleration virtually limitlessly. An EU initiative enhanced these devices by boosting energy storage capacity.
Supercapacitors are energy storage devices that can deliver power rapidly and be recharged almost infinitely without a drop in performance. They have become essential for auxiliary power in electric cars, helping them to accelerate on demand and recover energy during braking.
However, energy storage capacity or energy density of conventional supercapacitors is limited (translating to a weight issue), and they are expensive. The EU-funded AUTOSUPERCAP (Development of high energy/high power density supercapacitors for automotive applications) project addressed the need for a high-performance, low-weight power system with a low-cost target.
Work began with the definition of specific applications and their requirements, and the simulation of the automotive power system with the battery-supercapacitor storage unit. Parametric studies were carried out to study the effects of a supercapacitor on an efficient and sustainable automotive power system.
Overall, results showed that the supercapacitor greatly reduces battery ageing and also displays modest energy efficiency improvements when operating under critical climate conditions. The supercapacitor increases battery life from 400 % to 2 100 % depending on the circumstances.
Cost and life-cycle analyses were conducted for supercapacitors and power systems in electric vehicle applications in order to evaluate performance, cost, recyclability and sustainability.
Recycling protocols for the supercapacitor parts and materials were assembled and tested. It was found that recycled carbon materials such as activated carbon fabrics, multi-wall carbon nanotubes and graphenes do not suffer any additional degradation during recycling. These various forms of carbon can potentially be used for producing supercapacitors for electric vehicle applications.
AUTOSUPERCAP delivered an innovative supercapacitor that exceeds foreseen performance levels, estimated cost, sustainability and materials recycling protocols. At long last, the industry in Europe has a supercapacitor for automotive applications that is economically feasible.