The idea of boosting vehicle fuel economy by using windmill components might sound a little Quixotic, but here goes.

Mazda is working on a new braking system called i-ELOOP. It captures energy from the vehicle's inertia and produces an electric charge from the alternator just as the driver lets off the gas pedal. This energy is captured quickly in a Electric Double Layer Capacitor, which are commonly found in wind turbines. The system will debut on the 2014 Mazda6 and is part of the company's Skyactiv fuel-economy boosting efforts.

Under the most optimal conditions (i.e., when running every imaginable battery-draining component in the car), Mazda's new system can boost fuel economy by as much as 10 percent. More typically, though, fuel economy will increase by about one mile per gallon.

In 2011, the Japanese automaker said it was aiming to boost fleetwide fuel economy by about 30 percent over the next three years through its Skyactiv program. That effort starts down the fuel-saving path by using improvements in engine design, aerodynamics and weight-reducing parts. Later, bigger changes to the powertrain (i.e., plugs) go into effect. You can read about the general timeline here.
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Regenerative Braking System
Regenerative braking systems convert a vehicle's kinetic energy into electricity as the driver applies the brakes. The electricity is then stored for later use. It can be used to power the headlights, climate control, audio system, or any other electrical equipment. This reduces the need for the engine to burn extra fuel to generate electricity, thereby improving fuel economy.

Mazda's i-ELOOP is a unique regenerative braking system that uses a capacitor instead of a battery to store the electricity. Capacitors can be charged and discharged extremely quickly, enabling electricity to be supplied as and when it is needed. By efficiently recovering, storing and reusing energy, i-ELOOP improves fuel economy by approximately 10 percent in real-world driving conditions.

i-ELOOP's New Technologies
A variable voltage alternator (12V-25V) for efficient electricity generation as the vehicle decelerates

A high-capacity Electric Double Layer Capacitor that rapidly stores large amounts of electricity and efficiently redistributes it. (i-ELOOP is the world's first passenger vehicle regenerative braking system to use a capacitor)

i-ELOOP starts to recover kinetic energy the moment the driver lifts off the accelerator pedal and the vehicle begins to decelerate. The variable voltage alternator generates electricity at up to 25V for maximum efficiency before sending it to the Electric Double Layer Capacitor (EDLC) for storage. The alternator can fully charge the capacitor in just a few seconds. A DC/DC converter steps down the electricity from 25V to 12V so it can be used for the vehicle's electrical components.

Providing there is sufficient charge stored, all the vehicle's electric components are powered by the capacitor and the battery, thereby removing the need for the engine to generate electricity through the alternator by burning extra fuel. The alternator is switched off when the accelerator pedal is depressed and when the i-stop idling stop system is active, and switched on only when the vehicle is decelerating. During city driving with frequent acceleration and deceleration, charging mostly recommences before the capacitor is fully discharged. Therefore, i-ELOOP can provide nearly all of the vehicle's electricity requirement. This combination of minimizing the amount of fuel needed for electricity generation and efficiently recovering, storing and reusing energy enables Mazda to deliver significantly improved fuel economy.


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    • 1 Second Ago
  • 14 Comments
      Rotation
      • 2 Years Ago
      That step-up and step down is more complex than indicated. The voltage on a capacitor rises linearly with the amount of energy stored in it. This, unlike a battery which will drop only 20% (or whatever) from full to empty. This whole thing doesn't make any sense. Why use a capacitor with its low capacity when a battery could absorb electricity as fast as it is made here. BMW implemented a system like this two years ago using a battery. And no, you'll never get 10%.
        PeterScott
        • 2 Years Ago
        @Rotation
        Sure it makes sense. The cycle life of a Ultra-Capacitor is measured in hundreds of thousand if not millions of cycles. Which means it should never wear out in usage. So no expensive replacement for the user years down the road. While capacitors have low energy density, you can get by with less energy density (in this application) because they have very high power density and essentially unlimited cycle life. Using capacitors to actually move an EV would be pointless, but this usage plays to capacitor strengths.
        Joeviocoe
        • 2 Years Ago
        @Rotation
        "You could discharge and recharge a lead-acid battery by an amount equivalent to the capacity of this capacitor and not damage it" Not true at all. " It can be used to power the headlights, climate control, audio system, or any other electrical equipment." -Press release Climate Control is much too much of a power load to be constantly handled through battery cycles. Lead Acid batteries, even deep cycle, cannot.
        Rotation
        • 2 Years Ago
        @Rotation
        You could discharge and recharge a lead-acid battery by an amount equivalent to the capacity of this capacitor and not damage it. It would wear out at the same rate as it otherwise would. High power density is not critical here. The alternator cannot generate all that much power and the draw from it can be no larger than a lead-acid battery could take, because no system connected to the outputs can assume the capacitor is charged at all, it must be able to work off the lead-acid battery alone. This doesn't play to capacitor strengths at all.
        2 Wheeled Menace
        • 2 Years Ago
        @Rotation
        Lead acid battery: lasts approximately 300 full cycles. Capacitor: lasts many millions of full cycles. In a normal car application, the lead acid battery is basically running a 5-10% cycle depth, that's why it can last for 5-8 years. But it wouldn't live long as a mild hybrid battery.
          Rotation
          • 2 Years Ago
          @2 Wheeled Menace
          This isn't a mild hybrid. The energy collected cannot be used to move the vehicle. This is the same in operation as BMW's Brake Energy Regeneration system. BMW's system uses a lead-acid battery (glass mat) and works fine. You are missing out on that fact that the amount of energy stored and discharged here is large compared to the capacitor capacity but small compared to lead-acid capacity, so the lead-acid battery wouldn't be deep-discharged.
          Rotation
          • 2 Years Ago
          @2 Wheeled Menace
          This isn't a mild hybrid. The energy collected cannot be used to move the vehicle. This is the same in operation as BMW's Brake Energy Regeneration system. BMW's system uses a lead-acid battery (glass mat) and works fine. You are missing out on that fact that the amount of energy stored and discharged here is large compared to the capacitor capacity but small compared to lead-acid capacity, so the lead-acid battery wouldn't be deep-discharged.
          Rotation
          • 2 Years Ago
          @2 Wheeled Menace
          This isn't a mild hybrid. The energy collected cannot be used to move the vehicle. This is the same in operation as BMW's Brake Energy Regeneration system. BMW's system uses a lead-acid battery (glass mat) and works fine. You are missing out on that fact that the amount of energy stored and discharged here is large compared to the capacitor capacity but small compared to lead-acid capacity, so the lead-acid battery wouldn't be deep-discharged.
      Rick
      • 2 Years Ago
      Yawn Mazda SSSsssss x 1 mile per gallon extra SSSSsss Just put a diesel engine in it.
      2 Wheeled Menace
      • 2 Years Ago
      Hm, are we intentionally confusing people with the article title? A windmill capacitor is just a capacitor. And this is just a start-stop mild hybrid type system here.
      Rotation
      • 2 Years Ago
      I calculated, the storage for the largest Chemi-Con ELDC is 1200F. At 15V, that's 135KJ of energy storage. That's 37.5Wh. This is about 2/3rds the amount of energy storage as in an iPad 2 (far less than an iPad 3). To be honest, this figure seems perhaps optimistic to me, given Mazda says they can fill the cap in a few seconds. How big an alternator do you think is in there? 200A? At 20V (average) that is 2kW. A few seconds of power from that (let's say 5 seconds) is 2.7Wh.
      • 2 Years Ago
      Electronic components suppliers Your news about Electric Double Layer Capacitors is very useful. The illustrations are easy to the users to understand the process of EDLC. www.shrutimechatronics.com/stock-list.php
      PeterScott
      • 2 Years Ago
      Relatively small improvement. But I like that the extra cycling is in a capacitor, which should have near unlimited cycle life and should likely last the life of the car.
        Joeviocoe
        • 2 Years Ago
        @PeterScott
        Not having to recycle lead acid... Win for the environment.
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