Flywheel KERS is a green, high efficiency and low cost of power train technology applied in vehicle. The vehicle's kinetic energy under braking is recovered and stored as mechanical energy in a flywheel and released as power assistance under acceleration in later. Flywheel KERS can help vehicle to achieve significant power enhancement and fuel savings.
Benefited from the application of new technology and material, flywheel KERS has essential difference with conventional flywheel:
(1) High specific energy: 100¡«130wh£¯kg£¬high specific power: 5 000¡«l0,000 w£¯kg¡£
(2) High energy transformation efficiency: single efficiency: 90%
(3) Compact and lower mass
(4) Wide range of temperature fitted for operation, less sensitive for working temperature
(5) Long lifespan, less sensitive on deep and frequent discharging
(6) Low loss, less maintenance
The flywheel KERS utilizing most cutting edge technology is totally different in application and function with flywheel battery which was in practice in 1970¡¯s & 1980¡¯s.
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Items in comparison |
Flywheel battery |
Flywheel KERS |
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Performance request |
To achieve high capacity of energy delivery by massive energy storage |
To be big power assistance under acceleration and reduce fuel consumption |
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Technology request |
The capacity in massive energy storage and delivery is in priority, energy loss is restricted severely. |
To realize high power assistance by high specific power of flywheel is in priority. To maximize the efficiency of energy transformation and optimize power control system by sophisticated system control strategy. |
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Technology approaches |
Massive energy storage: extremely high flywheel rotation speed, 40,000-50,000rpm; carbon fiber composite utilized in flywheel manufacture; relative heavier of flywheel rotor |
Innovated power system topology: enhanced power delivery and higher efficiency of energy transformation |
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To reduce friction in maximum£ºnon-contact magnetic bearing, flywheel rotating in vacuum |
High efficient system control strategy: to maximum the efficiency of energy transformation, to optimize the status of energy storage and power control system, to maintain the stability of power assistance system | |
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High capacity of energy transformation system: high specific power of dual-way inverter |
Innovated structure and technics: enhanced efficiency of energy transformation, increased power delivery | |
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High power assistance by big specific power of flywheel: Keep ICE operating in the most efficiency section of power curves, less power request and fuel consumption
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Approaches for safety |
Extremely strict |
To be achieved in a massive production way |
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Weight |
Heavy and is not suitable for mobile application |
Capable of being installed in small car |
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Cost |
Expensive |
Capable of massive production |
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Application |
To balance the electricity grid |
New energy automobile |
Three types of flywheel KERS as their respective different energy delivery methods:
Energy storage type:
Its structure is similar with flywheel battery, but the volume of energy stored in it is much lower than flywheel battery. There are total four transformations are experienced when braking kinetic energy recovered goes into flywheel kinetic energy released. When these two different kinetic energy is transformed each other, they need to be transformed into electrical energy for transiting firstly and then chemical energy stored in battery and vice versa
Mechanical type:
The flywheel is coupled with drive shaft via a CVT, the power and energy is also delivered by CVT and in form of mechanical energy. It is no requirement on motor and power battery configured in power train, so it is called all mechanical flywheel KERS.
Electrical type:
The flywheel is coupled with drive shaft via electrical continuously various transmission system which comprises planetary gear set and speed control motor, etc. The major route of power and energy delivery flow is mechanical way, but speed control motor is doing assistance in energy/power management.
Because it is the mechanical form for energy stored in flywheel KERS rather than chemical form in battery applied in conventional hybrid power system, so the specific power in flywheel KERS is much higher than the latter. This character endows flywheel KERS some outstanding performance.
Enhanced power performance and decreased fuel consumption:
Flywheel KERS is capable of delivering surge power to assist primary power source due to its high specific power when vehicle is in starting, climbing or acceleration. This character boosts the vehicle power performance and ensures the primary power source operated in the most efficient section of engine curves.
Due to a big portion of reserve power is realized by flywheel KERS rather than engine itself, so the power of primary power resource can be decreased and then fuel consumption and emission reduced.
High efficiency of energy recovering:
The specific power of flywheel in which energy is stored in form of mechanical energy is far superior to power battery in which energy is stored in form of chemical energy. The flywheel KERS is capable of absorbing kinetic energy in a more efficient way when vehicle is under braking. Its energy absorbing speed is not limited by the speed of chemical reaction as in chemical battery and the efficiency of braking energy recovery is boosted into 70% rather than 35% in the system primarily incorporating battery as energy storage.
Less weight and lower cost:
Flywheel KERS shall replace expensive Power Battery Pack and power electronics applied in conventional hybrid power train with a more efficient way and reduce the weight and cost in system.
Long lifespan and no pollution to eco:
The lifespan of flywheel KERS is capable of covering the whole operation duration of a vehicle and also keep the advantages of long maintenance cycle, no toxic matter inside and no pollution to eco.