# Kinetic Energy Regenerative Breaking System

11. Jan 2013
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### Kinetic Energy Regenerative Breaking System

• 2. Outline  Why we need brakes?  Overview  Topics related to braking  Regenerative Braking  Working and Elements  Types of KERBS  Storage of Energy  Advantages and Limitations  Conclusion  References 2
• 3. Why we need brakes ?  We need brakes to reduce the speed of moving objects or stop them. Formula 1 cars are capable of decelerating from 124-mph to a standstill in only 2.9 seconds. 3
• 4. Over view  Brakes translate a push of a pedal to slowing down your car.  Disc or Drum brakes play the part of the brake system that does the actual work of stopping the car.  Friction between the various mating surfaces results in braking action and slow down of car. 4
• 5. Topics related to braking  Pascal’s law  “Pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same”  Hydraulic Press – basic concept for brakes  Braking action 5
• 7. Types of Brakes  Basically, purpose of brakes is to apply mechanical resistance i.e. Friction on rotating wheels in order to slow down the car.  The various methods used to apply friction are :  Hydraulic Braking System  Electromagnetic System  Pumping brakes 7
• 8. Regenerative braking • Is an energy recovery mechanism which slows a vehicle or object down by converting its kinetic energy into another form, which can be either used immediately or stored until needed • The energy can be stored : • electrically by battery or capacitors bank • mechanically via pneumatics, hydraulics • kinetic energy in rotating flywheels 8
• 9. Energy transformation  Friction Brake:  Regenerative Brake: This brake system converts Capturing kinetic energy the kinetic energy of vehicle generated from braking and motion into heat converting it to electricity, hydraulic pressure or spring force. 9
• 10. Elements of the KERBS 10
• 11. Working of KERBS • Vehicle has forward momentum • Auxiliary systems, like Hydraulic cylinders, Flywheel apparatus, etc. are coupled to wheels • When brakes are applied, the friction between braking elements and wheel, engages the regenerative system • The rotors experience opposing torque, this activates the system : • Hydraulic pump used to pressurize fluid and store in cylinders • Flywheel used to store as rotary motion • Motor/ Generator used to generate electricity and store in batteries 11
• 12. Types of KERBS  Hydraulic  Hydrostatic Regenerative Braking (HRB) system uses electrical/electronic Components as well as hydraulics to improve vehicle fuel economy  Flywheel assisted  Engines have been using energy-storing devices called flywheels, which are rotating disc, which are considered as “energy storing reservoirs”  Nitilon Springs assisted  Special purpose Compression springs are used to store energy as spring force 12
• 13. Hydraulic KERBS  Braking energy is converted to hydraulic pressure and stored in a high-pressure hydraulic accumulator  When the vehicle accelerates, the stored hydraulic energy is applied to the transmission, hence reducing the fuel to be combusted in the engine 13
• 14. Flywheel KERBS  Packaged inside a single housing is a shaft mounted flywheel that is connected via a chain/gear to the drive shaft  During braking and coasting, the flywheel spools-up (accelerates as it spins) and absorbs a storehouse of otherwise wasted energy 14
• 15. Storage of Kinetic Energy • In a Hydraulic KERBS, • stored as fluid pressure in hydarulic cylinder. • In Flywheel assisted KERBS, • stored as rotational energy in flywheel. • In Nitilon spring assisted KERBS, • stored as spring force or potential energy. • Recent development is that a Motor/Generator is used to convert kinetic energy to electrical energy. 15
• 16. Regenerative Braking Controllers • The brake controller makes the entire regenerative braking process possible. • its monitors the speed of the wheels • calculate how much torque -- rotational force -- is available to be fed back • deciding whether the stored energy should be released immediately or stored temporarily • Special ECU used for the controlling purpose 16
• 17. Comparison  Hydraulic KERBS  Flywheel KERBS  5.55 Wh/kg at 250 Bar  Maximum power pressure boost of 60 kW for  Energy efficiency at 6.67 seconds 73%  Compact weight and  Heavy equipments size  Limited power storage  Higher efficiency  Leakage of hydraulic  Lower cost fluid  Can be used for small vehicles also 17
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• 19. Advantage of regenerative breaking • Improves fuel efficiency • Conservation of Energy • Wear reduction • Higher pick up response • Lower emissions • Kinetic energy regenerated can be stored in form of electricity in batteries, which can be used to power up other auxiliary systems • Use of KERBS in hybrid and electric vehicles will increase the travel distance 19
• 20.  - For example: 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 between 2004 and 2007. 20
• 21. Limitations of regenerative breaking  Added weight of minimum of 25 kilos  The regenerative braking effect drops off at lower speeds  The friction brake is a necessary back-up in the event of failure of the regenerative brake.  The amount of electrical energy capable of dissipation is limited by the capacity of the supply system  Under emergency braking it is desirable that the braking force exerted be the maximum 21
• 22. New braking system technologies  Anti-Lock Brake System (ABS)  Traction Control System (TCS)  Electronic Stability Program (ESP)  Regenerative braking system 22
• 23. Conclusion  Increased fuel efficiency  The lower operating and environment costs  All vehicles in motion can benefit from utilizing regeneration to recapture energy that would otherwise be lost.  As designers and engineers perfect regenerative braking systems, they will become more and more common 23
• 24. References  Cibulka, J. Kinetic energy recovery system by means of flywheel energy storage Advanced engineering 3(2009)1, ISSN 1846-5900  www.gm.com  www.howstuffworks.com  www.wikipedia.org 24