Flywheel energy storage systems store energy mechanically using a rotating mass. They use a motor/generator to accelerate the rotor and store energy kinetically, then decelerate it to discharge the stored energy. Flywheels are best for peak powers of 100 kW to 2 MW for durations of 12 to 60 seconds. A key component is magnetic bearings to levitate the flywheel in a vacuum environment at high speeds. Flywheels have advantages of high power density, long lifetime, and short recharge times but also challenges of developing durable bearings and addressing mechanical stresses at very high speeds.

1. Flywheel Energy
Storage System

2. Introduction
 A flywheel, in essence is a mechanical battery - simply a mass rotating
about an axis.
 Flywheels store energy mechanically in the form of kinetic energy.
 They take an electrical input to accelerate the rotor up to speed by using
the built-in motor, and return the electrical energy by using this same
motor as a generator.
 Flywheels are one of the most promising technologies for replacing
conventional lead acid batteries as energy storage systems.

3. Design of flywheel energy storage system
 Flywheel systems are best suited for peak output powers of 100 kW to 2 MW and for
durations of 12 seconds to 60 seconds .
 The energy is present in the flywheel to provide higher power for a shorter duration,
the peak output designed for 125 kw for 16 seconds stores enough energy to
provide 2 MW for 1 second.

4. Flywheel Energy Storage System

5. Component of FESS
 Flywheel
 Motor/Generator
 Magnetic bearings
 External Inductor

6. Flywheel
 Flywheels store energy in a rotating mass of steel of composite material.
 Mechanical inertia is the basis of this storage method.
 Use of a motor/generator, energy can be cycled (absorbed and then
discharged)
 Increasing surface speed of flywheel, energy storage capacity (kWh) of
unit increased.

7. Motor/Generator
 Permanent Magnet (PM) machines have the most advantages,
including higher efficiency and smaller size when compared with other
types of motors/generators of the same power rating.
 PM also exhibit lower rotor losses and lower winding inductances,
which make it more suitable for a vacuum operating environment
and the rapid energy transfer of flywheel applications.
 The motor/generator is designed to be operated at high speed for
minimize system size.

8. Magnetic Bearings
 Magnetic bearings consists of permanent magnets, which support the
weight of the Flywheel by repelling forces, and electromagnets are used
to stabilize the Flywheel.
 The best performing bearing is the high-temperature super-conducting
(HTS) magnetic bearing, which can situate the Flywheel automatically
without need of electricity or positioning control system.
 HTS magnets require cryogenic cooling by liquid nitrogen.

9. External Inductor
 The high-speed PM machines offer low inductances with low
number of stator turns and large operating magnetic air gaps .
 The low inductances result in High Total Harmonic Distortion
(THD) which increases the machine power losses and temperature.
 Using an external inductor in series with the machine in charging
mode is necessary to reduce the THD and bring it within an accepted
range.

10. Working of a flywheel energy storage system
Its work in three mode:-
 Charging mode
 Stand by mode
 Discharging mode

11. Applications of FESS
 Power Quality/UPS
 Industrial Pulsed Power
 Light rail power
 Flywheel in distribution network
 Hybrid and electric vehicles

12. Advantages of FESS
 High power density.
 High energy density.
 The lifetime of the flywheel is almost independent of the depth of the charge and
discharge cycle.
 No periodic maintenance is required.
 Short recharge time.
 Flywheel systems are not sensitive to temperature since they are operating in a
vacuum containment

13. Disadvantages of FESS
 Complexity of durable and low loss bearings
 Mechanical stress and fatigue limits
 Material limits at around 700M/sec tip speed
 Potentially hazardous failure modes
 Short discharge time

14. Future work in FESS
 Advanced flywheel system rotate above 20,000 rpm in vacuum enclosure made from
high strength carbon composite filament will be very efficient.
 The flywheels are not the primary source of power generation.
 Rather, when there is too much power on the grid, it is shunted to the flywheel facility
and used to set the flywheels in motion.
 Then, when the power is needed a few seconds or minutes later, the momentum of the
flywheels is used to generate power back into the grid.

15. Conclusions
 The state of charge can easily be measured, since it is given by the rotational velocity
 The fast rotation of Flywheel rotors is suitable for direct generation of high voltage.
 Environmental friendly materials, low environmental impact.

16. Thank
You