Mazda unveils capacitive regenerative braking system

Capacitor-based system is world first for a production car

Auto manufacturers are always spending millions on technology that will enhance the driving experience. Of late, the emphasis has been on fuel-saving technology, not just because of skyrocketing fuel prices, but because of the environmental impact automobile emissions have. Some manufacturers like Lexus have gone the hybrid way, making the internal combustion engine work only when needed to. Others have developed efficiencies in current technology to go further on the same amount of fuel – BMW, for example, has now switched to electric power steering, which means that the motor can be shut off when the wheel isn't turned (opposed to a hydraulic system whose pump needs to be running whenever the engine is on.) BMW also turns on the alternator to charge the vehicle's battery only when the driver is off the throttle, so there's less load on the engine, leading to less fuel consumption. 

One of the technologies that manufacturers have developed to maximise fuel efficiency is regenerative braking. In a nutshell, your brakes are energy convertors: they slow your car down by changing its kinetic energy – or momentum – into heat energy through friction between pad and disc or shoe and drum. What a regenerative braking system does is convert that kinetic energy into electrical energy, much like a bicycle's dynamo does, while providing the force to slow the car down. It's a win-win situation, and the men from the Zoom-zoom corner have gone one step ahead: they've engineered the first capacitor-based regenerative braking system for a production car. 

The main problem with a capacitor-based system for electrical energy storage has been the time factor. By design, capacitors bleed the charge slowly, so although they're more efficient than an electric motor at getting the charge, they can't store it and therefore were seen as a good option for racing applications, where cars can use the energy stored while braking into a corner to drive out of it even quicker. Capacitors can store and discharge energy quickly and are immune to the 'weakening' that regular batteries undergo over time with many charging cycles, which helps that racecar case. However, that single point of capacitors not being able to store the charge for very long has kept it out of production car plans – until now.

Mazda has unveiled what they call the 'i-ELOOP', short for 'Intelligent Energy Loop'. It is a system that will allow a production car to store electricity generated during braking in a capacitor, although it won't replace a battery and electric motor. It must be noted that this system doesn't need an electric motor and dedicated battery like other regenerative braking systems do. How it works is, the moment the driver gets off the accelerator electrical energy starts getting generated at up to 25V by the variable voltage generator. It gets sent to the capacitor, called an “Electric Double Layer Capacitor,” which can be charged to capacity in a few seconds. It is then fed to a DC/DC converter, which steps it down to a steady 12V and feeds it to the various electrical components in the car. If necessary, it charges the battery as well. In stop-go traffic, Mazda claims it increases fuel efficiency by ten percent.

The i-ELOOP system isn't designed to replace an electric propulsion system, as is clear from the description. This means it does away with a hybrid vehicle's expensive Li-ion battery packs that need to be replaced every few years and electric motors that need periodic maintenance. In conditions like we have in cities like Mumbai and Pune where aggressive driving is the only way to get anywhere in a reasonable amount of time, we can certainly see the benefits the i-ELOOP system affords. The system will start appearing on Mazdas from 2012 onwards.