Regenerative Brakes

There’s sometimes some confusion when it comes to describing what Regenerative Brakes are .. so here’s the definition: it’s a type of energy recovery mechanism that is supposed to slow a vehicle down by converting its kinetic energy into another form of energy; this energy can be either used immediately or stored until needed.

The most common form of Regenerative Braking usually involves using an electric motor serving as an electric generator. When it comes to electric railways, the generated electricity is usually fed back into the supply system. If you were looking at battery electric and hybrid electric cars, the same energy is stored and kept in a battery or bank of capacitors for later use. The energy can also be stored via pneumatics, hydraulics or the kinetic energy of a rotating flywheel.

Cars that are driven by electric motors typically use the motor as a generator when it uses Regenerative Braking: it’s operated as a generator when the driver brakes and its output is supplied to an electrical load. The same transfer of energy to the load is what provides the braking effect to the car. In other words, this is what helps you stop and not get into an accident.

As you probably already know, the whole Regenerative Braking system is mainly used on hybrid gas/electric automobiles in order to recoup some of the energy that was lost while the driver was stopping. This same energy is then saved in some sort of storage battery and then used later to power the motor whenever the car is in electric mode.

The typical friction - based braking is used alongside the Regenerative Braking for these following reasons:

- The Regenerative Braking effect tends to drop off at lower speeds. Because of this, the friction brake still needs to be there in order to bring the car to a complete stop.

- Another reason the friction brake is there is because it serves as a back-up just in case your Regenerative Brakes don’t work.

- Most of the road cars with Regenerative Braking only have power on some of the wheels. The power only applies to these specific wheels because they’re the only wheels that are linked to the drive motor.

- The amount of electrical energy that’s capable of dissipation is usually limited by one of two things: either the capacity of the supply system to absorb this energy or on the state of charge of the battery or capacitors. There can be no Regenerative Braking effect if there’s another electrical component on the same supply system that is not currently drawing power.

If you wanted to compare Dynamic Brakes, you’d find that these Brakes dissipate the electric energy as heat by passing the current through large banks of variable resistors. Cars that use these include forklifts, Diesel-electric locomotives, and streetcars. This heat can either be used to heat the inside of your car or it can be dissipated externally by large radiator-like cowls to house the resistor banks.

The main disadvantage of Regenerative Brakes when compared to Dynamic Brakes is that Regenerative Braking has the need to closely match the generated current with the supply characteristics and increased maintenance cost of the lines.

So, reading about these two types of Brakes and Regenerative Brakes in general, which one do you prefer? Of course, if you get a hybrid you really have no other choice.