Johan Söderbom, Thematic Leader for Smart Grids and Energy Storage at EIT InnoEnergy, explains why ultra-capacitors will be critical for the transition towards electrification and automation of vehicles.
Ultra-capacitors have been used in the automotive sector since the turn of the century, with Japanese companies like Honda and Toyota being early innovators, but the technology has made slow progress in the industry. Recently, western manufacturers such as General Motors and Tesla have begun incorporating ultra-capacitors in their vehicles, and Lamborghini recently joined forces with Massachusetts Institute of Technology (MIT) to develop ultra-capacitors for use in its latest hybrid vehicle. Volvo is also collaborating with a leading manufacturer, Maxwell Technologies (now owned by Tesla), to develop ultra-capacitors for its vehicles.
The key question, however, is why now? The answer is in part based on technological development, but also on the wider impact that electrification and automation is having across the industry and beyond. Ultra-capacitors have clear advantages over batteries such as very long life times (more than 10 years), quick charging/discharging times, the ability to operate in extreme environments (temperatures of -40°C to +65°C), and the ability to recycle stored braking energy for acceleration and hence lower fuel consumption/emissions Their drawbacks, however, are also significant, including high cost and low energy densities.
The case for ultra-capacitors is not to replace batteries completely but rather to support them as secondary power sources in a hybrid configuration. In this instance, battery life can be extended significantly (and operating cost reduced) through load reduction with ultra-capacitors taking over the short-term power requirements of the vehicle. Typical applications include engine start/stop when the vehicle is at a standstill to reduce emissions and fuel consumption, and power steering requirements. Further, as the trend towards electrification and automation amplifies, there will be more requirements for electronics and short-term power in vehicles such as wifi, 5G, video streaming, and other automated systems.
An increase in autonomous vehicles will lead to the need for higher connectivity between vehicles, and more sensors and Internet of Things (IoT) devices are expected to be incorporated into vehicle architectures to read traffic and road signals, thereby drastically increasing power requirements. It is here that the fast charging benefit of ultra-capacitors can be truly appreciated as they can potentially help with the adoption of electric vehicles by addressing the slow charging issue.
A critical component
Ultra-capacitors should therefore be viewed as a critical part of a vehicle infrastructure that generates additional value through lower cost of ownership by reducing battery replacements (and size), reduces emissions from lower fuel consumption, and enables the inclusion of additional devices into vehicles without having to increase the power demand on batteries. In this way, ultra-capacitors can reduce the total cost of ownership of vehicles and facilitate the shift towards electrification and automation.
As vehicle architecture evolves, the systems that are expected to adopt ultra-capacitors include safety and powertrain, engine throttle, cooling fans, oil pumps, doors, seating, electrical windows, car heating and air conditioning, and audio and video.
Further development is needed by the industry, including redesigning vehicle architecture, but new forms of capacitors such as Li-ion or graphene-based ultra-capacitors that have higher energy density and costs that are comparable with Li-ion batteries will make them more attractive in the future.