Few people know it, but supercapacitors are already in use in many car models for brake energy regeneration and Start-Stop systems (not only in electric vehicles). Indeed, ultracapacitors are particularly effective in meeting this need. Able to charge and discharge very quickly and almost without wear, the supercapacitor appears as an ultra-fast and reliable battery.
Start-Stop system to cut the engine off
In 2010, PSA was the first car manufacturer to have had the idea of using supercapacitors to optimize the Start-Stop system that cuts the engine when the car stops with gear lever in neutral to save some fuel.
The first Start-Stop systems used a strengthened starter for a faster restart than the first starting up of the car. Unfortunately, this restart remained slow, noisy, and caused heavy vibrations of the vehicle.
PSA has modified the system by replacing the strengthened starter by a alternator-starter, a reversible alternator which starts the motor with its drive belt. The system then becomes silent, fast, and there are not vibrations anymore during the restart.
Thanks to the use of supercapacitors to power the generator starting up, the system works very well, even for diesel vehicles. Indeed, the mechanical and electrical energy required to start a diesel is roughly twice that required by a gasoline car of the same size.
The kinetic energy is recovered by the system when braking and converted into electricity that will serve to power the alternator during the restart.
Unfortunately, a conventional battery charges too slowly to be able to efficiently store all the energy collected during braking and is not always able to deliver the power needed for a quick restart of a diesel vehicle. After 3 or 4 stops close, the battery would be drained.
Supercapacitors are on the other hand capable of rapidly storing a large amount of electricity, and to return it in few tenths of seconds. In the new electrical architecture of its e-HDI cars, PSA thus integrated supercaps. Arranged under the hood, these supercapacitors size of 2 cans of 33 cl allow efficient electrical storage and rapid restart of the car.
With supercapacitors, the Start-Stop system works even with a very dense traffic and multiple stops per minute. This allows for maximum fuel savings with consumption down 15% on the urban cycle approval. Citroën then announced a gain of 0.4 l / 100 km on average for a Citroën C5 1.6 HDi 112 hp.
Supercapacitor to power vehicle electrical systems
Mazda has announced the development of a new technology based on ultracapacitors: i-ELOOP (for Intelligent Energy Loop).
In the same way, Mazda uses the fast charge capacity of supercapacitors to effectively recover kinetic energy during braking. But this time the system no longer serves only to supply the Stop & Start system called i-STOP at Mazda, it also serves to power the vehicle's electrical systems.
Mazda introduced its braking energy recovery system at the Tokyo Motor Show. The i-ELOOP then equipped the TAKERI concept car heralding the next generation of the Mazda 6.
The i-ELOOP provide energy to power the air conditioning, the car radio, the communication system and other electrical systems. When the engine is off, the system also charges the classic vehicle battery.
I-ELOOP technology will be marketed in 2012 and should provide a fuel economy of about 10% on the roads of cities.