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# Regenerative Braking

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by

## Syed Ali

on 4 January 2013

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#### Transcript of Regenerative Braking

REGENERATIVE BRAKING SYSTEM BRAKES WORKING ADVANTAGES A brake is a device that decelerates a moving object / prevents an object from accelerating.
Brakes use friction to convert kinetic energy into heat
Guiding principle- kinetic energy increases quadratically with velocity -K = mv^2 / 2
When the brake is pushed the caliper containing piston pushes the pad towards the brake disc which slows the wheel down.
Our MODEL We have demonstrated the basic principle of regenerative braking mechanism in our model.

An electric motor brake is basically an ordinary electric motor run backward. Instead of supplying the motor with electricity to make the shaft turn, some outside force is applied to the shaft to make it turn, which results in the generation of electricity.

This external force is supplied by the momentum of the wheel. REGENERATIVE BRAKING CONVENTIONAL BRAKING SYSTEM Conventional braking systems use friction to counteract the forward momentum of a moving car.
As the brake pads rub against the wheels, excessive heat energy is created.
This heat energy dissipates into the air, wasting up to 30% of the car's generated power.
In a regenerative braking system, the objective is to recapture the energy byproduct that results when the brakes are applied.

In electric or hybrid automobiles, the electric motor that drives the car's wheels plays a major part during braking.

When the brake pedal is pressed, the regenerative braking circuit switches the motor so that it now operates in reverse to counter the direction of the wheels. This reversal actually makes it perform like a power generator or dynamo that produces electrical energy.

The electricity developed is routed towards the car's storage batteries to recharge them. Regenerative braking technology funnels the energy created by the braking process back into the system in the form of charging the battery for further use.
In a regenerative braking system the energy normally lost in the braking process is transferred to the generator from the rotating axle and then transferred to the battery, thus saving energy.
OVERVIEW A switch is used as brake which cuts off power supply from battery to the motor.

With no electrical input and the wheel still moving the motor acts as a generator and generates electrical energy.

This energy is generally used to charge the battery but we have put some electrical load (LEDs) to demonstrate electricity is being generated.
Reduction of pollution

Increase in engine life

Braking is not total loss

Wear Reduction
Reduction in Pollution Railway vehicle – The Delhi Metro saved around 90,000 tons of carbon dioxide (CO2) from being released into the atmosphere by regenerating 112,500 megawatt hours of electricity through the use of regenerative braking systems.
Increase in Engine Life
Regenerative brakes have been able to improve the performance of engines.
This has been exhibited in the Motor sport industry –The system used by F1 cars is called K. E. R. S (Kinetic Energy Recovery System) Braking
Not a Total Loss Conventional brakes apply friction to convert a vehicle’s kinetic energy into heat. In energy terms, therefore, braking is a total loss: once heat is generated, it is very difficult to reuse. The regenerative braking system, however, slows a vehicle down in a different way.
Wear
Reduction An electric drive train also allows for regenerative breaking which increases Efficiency and reduces wear on the vehicle brakes. LIMITATIONS The regenerative braking effect drops off at lower speeds, therefore the friction brake is still required in order to bring the vehicle to a complete halt.

The friction brake is a necessary back-up in the event of failure of the regenerative brake.

Most road vehicles with regenerative braking only have power on some wheels (as in a 2WD car) and regenerative braking power only applies to such wheels, so in order to provide controlled braking under difficult conditions (such as in wet roads) friction based braking is necessary on the other wheels.
NS Munam Bin Tariq (ME-148)
NS Muneeb Ahmed (ME-149)
NS Syed Affan Ali (ME-157)
NS Nayab Shiraz (ME-172) Types Of Regenerative Braking System Electric energy storage. When you hit the brakes, this system engages an integrated motor-generator which is connected to the spinning wheels. The motor slows down the car and converts the motion into electrical energy, which is stored in batteries. These systems typically need a large payload of batteries or supercapacitors to store this energy, so they are usually only used on vehicles that are already hybrid or electric. These systems can capture and return around 50% of the energy lost in braking.

Compressed Gas energy storage. When you hit the brakes, this system engages a pump which forces compressed air into a tank. This converts the mechanical energy of motion into elastic energy in the gas. When you want to re-accelerate, the gas is let back out through the pump, which works in reverse to accelerate the car. These systems can capture and return around 70% of the energy lost in braking.

Flywheel energy storage. When you hit the brakes, this system engages a clutch which transfers the mechanical energy of motion into a single spinning disc called a flywheel. The disc is held on very smooth bearings so it can be accelerated to spin at a very high rate. When you brake the car the flywheel gets spun up. When you want to accelerate the flywheel is connected to the wheels and the energy from the flywheel can get you started. These systems can capture and return around 70% of the energy lost in braking.
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