06-04-2011, 11:55 AM
Presented by
MANOHAR KALAHAL
[attachment=11774]
Flywheel energy storage system
Working principle
Electric energy produced by solar ,wind, and hydro is directly connected to flywheel.
Flywheels are rotating wheels used to store kinetic energy.
It works by accelerating a rotor to a very high speed and maintaining the energy in the system as inertial energy.
The flywheel then delivers rotational energy to power an electric generator.
The sum of the kinetic energy of the individual mass elements that comprise the flywheel equals the energy stored.
The kinetic energy of a flywheel is given by
Ek is the kinetic energy
ω is the velocity of disc
The moment of inertia is defined as
Where M is the mass,
R is the radius,
k is the inertial constant
Why Flywheel Storage???
Commonly using energy storage system is electrochemical batteries such as
nickel hydrogen
nickel cadmium
Electrochemical batteries having lot of disadvantages such as
Low efficiency
Heavy weight
Environmental hazards
FLYWHEEL ENERGY STORAGE (FES)
Compare to that of electro-chemical batteries these FES are very useful and advantageous one
FES having
High efficiency
High depth of discharge
Long life
Almost three times that of batteries
Quick charging
COMPONENTS OF FLYWHEEL SYSTEM
Rotor:
- First generation flywheel energy storage systems use a large steel flywheel rotating on mechanical bearings.
-Newer systems use carbon fiber composite rotors that have a higher tensile strength than steel but are an order of magnitude less heavy.
Bearings:
The upper bearing of the unit is a combination magnetic bearing, providing suspension axially as well as radically.
The lower magnetic bearing suspends the shaft in the radial direction only.
At each end of the shaft there is also a touchdown bearing. This provides a back up bearing system should the magnetic bearings fail during testing.
` Magnetic bearings are sometimes used instead of mechanical bearings, to reduce friction.
Motor/generator
The motor/generator unit is located at the lower end of the shaft.
It consists of a two-pole rotor piece with surface mounted samarium cobalt magnets and a carbon fiber retaining wrap.
On the stator side, there are three phase sinusoidally distributed windings in twelve slots.
A water jacket around the stator provides cooling.
FLYWHEEL CONTROL
There are three modes of operation for the flywheel in a spacecraft power system
1) Charge
2) Charge reduction
3) Discharge
Charge
In charge mode, the solar array produces enough current to charge the flywheel at its set point and to provide the required load current. The solar array electronics regulate the DC bus voltage during charge mode
Charge reduction
In charge reduction mode, the solar array continues to provide load current but it cannot provide enough current to charge the flywheel at its set point. When this occurs, the DC bus voltage regulation function is transferred to the flywheel system.
Discharge
In discharge mode, the flywheel system provides the entire load current and regulates the DC bus voltage.
HOW CONTROL SYSTEM WORKS
AEROSPACE FLYWHEEL CHALLANGES
Short-term energy storage .
Any mechanical bearing with contact between the stationary and rotating parts will have enough loss to render the system uneconomical one .
solution to the problem is to use a non-contact active magnetic bearing that employs conventional electromagnets.
A reasonable magnetic bearing consumes a few watts for each kilogram of flywheel weight.
Superconducting magnetic bearings, have losses of 10-2 to 10-3 watts per kg for a 2,000 rpm rotor.
Flywheel its self consumes the energy and dissipated as heat.
ADVANTAGES
Flywheels are not affected by temperature changes.
Quick charging with in 15 min.
High efficiency.
High depth of discharge.
Long life.
simple measurement of the rotation speed is possible to know the exact amount of energy stored.
No limit of energy storage
Flywheels are also less potentially damaging to the environment.
DISADVANTAGES
short term energy storage.
Flywheel energy storage systems using mechanical bearings can lose 20% to 50% of their energy in 2 hours.
They have complex designs.
“Flywheel explosion” takes place when tensile strength of a flywheel is exceeded
APPLICATIONS
Energy storage - replacement for batteries for spacecraft in low earth orbit.
Power peaking for aircraft/spacecraft secondary power.
In the 1950s flywheel-powered buses, known as gyro buses, were used in, Switzerland.
It is hoped that flywheel systems can replace conventional chemical batteries for mobile applications, such as for electric vehicles.
CONCLUSION
This paper concludes that
The batteries that are used in the space craft, have a very limited life span (of the order of 36 months only). Hence the flywheel system is to replace batteries on future spacecraft.
As the flywheel system is a life long technology.
MANOHAR KALAHAL
[attachment=11774]
Flywheel energy storage system
Working principle
Electric energy produced by solar ,wind, and hydro is directly connected to flywheel.
Flywheels are rotating wheels used to store kinetic energy.
It works by accelerating a rotor to a very high speed and maintaining the energy in the system as inertial energy.
The flywheel then delivers rotational energy to power an electric generator.
The sum of the kinetic energy of the individual mass elements that comprise the flywheel equals the energy stored.
The kinetic energy of a flywheel is given by
Ek is the kinetic energy
ω is the velocity of disc
The moment of inertia is defined as
Where M is the mass,
R is the radius,
k is the inertial constant
Why Flywheel Storage???
Commonly using energy storage system is electrochemical batteries such as
nickel hydrogen
nickel cadmium
Electrochemical batteries having lot of disadvantages such as
Low efficiency
Heavy weight
Environmental hazards
FLYWHEEL ENERGY STORAGE (FES)
Compare to that of electro-chemical batteries these FES are very useful and advantageous one
FES having
High efficiency
High depth of discharge
Long life
Almost three times that of batteries
Quick charging
COMPONENTS OF FLYWHEEL SYSTEM
Rotor:
- First generation flywheel energy storage systems use a large steel flywheel rotating on mechanical bearings.
-Newer systems use carbon fiber composite rotors that have a higher tensile strength than steel but are an order of magnitude less heavy.
Bearings:
The upper bearing of the unit is a combination magnetic bearing, providing suspension axially as well as radically.
The lower magnetic bearing suspends the shaft in the radial direction only.
At each end of the shaft there is also a touchdown bearing. This provides a back up bearing system should the magnetic bearings fail during testing.
` Magnetic bearings are sometimes used instead of mechanical bearings, to reduce friction.
Motor/generator
The motor/generator unit is located at the lower end of the shaft.
It consists of a two-pole rotor piece with surface mounted samarium cobalt magnets and a carbon fiber retaining wrap.
On the stator side, there are three phase sinusoidally distributed windings in twelve slots.
A water jacket around the stator provides cooling.
FLYWHEEL CONTROL
There are three modes of operation for the flywheel in a spacecraft power system
1) Charge
2) Charge reduction
3) Discharge
Charge
In charge mode, the solar array produces enough current to charge the flywheel at its set point and to provide the required load current. The solar array electronics regulate the DC bus voltage during charge mode
Charge reduction
In charge reduction mode, the solar array continues to provide load current but it cannot provide enough current to charge the flywheel at its set point. When this occurs, the DC bus voltage regulation function is transferred to the flywheel system.
Discharge
In discharge mode, the flywheel system provides the entire load current and regulates the DC bus voltage.
HOW CONTROL SYSTEM WORKS
AEROSPACE FLYWHEEL CHALLANGES
Short-term energy storage .
Any mechanical bearing with contact between the stationary and rotating parts will have enough loss to render the system uneconomical one .
solution to the problem is to use a non-contact active magnetic bearing that employs conventional electromagnets.
A reasonable magnetic bearing consumes a few watts for each kilogram of flywheel weight.
Superconducting magnetic bearings, have losses of 10-2 to 10-3 watts per kg for a 2,000 rpm rotor.
Flywheel its self consumes the energy and dissipated as heat.
ADVANTAGES
Flywheels are not affected by temperature changes.
Quick charging with in 15 min.
High efficiency.
High depth of discharge.
Long life.
simple measurement of the rotation speed is possible to know the exact amount of energy stored.
No limit of energy storage
Flywheels are also less potentially damaging to the environment.
DISADVANTAGES
short term energy storage.
Flywheel energy storage systems using mechanical bearings can lose 20% to 50% of their energy in 2 hours.
They have complex designs.
“Flywheel explosion” takes place when tensile strength of a flywheel is exceeded
APPLICATIONS
Energy storage - replacement for batteries for spacecraft in low earth orbit.
Power peaking for aircraft/spacecraft secondary power.
In the 1950s flywheel-powered buses, known as gyro buses, were used in, Switzerland.
It is hoped that flywheel systems can replace conventional chemical batteries for mobile applications, such as for electric vehicles.
CONCLUSION
This paper concludes that
The batteries that are used in the space craft, have a very limited life span (of the order of 36 months only). Hence the flywheel system is to replace batteries on future spacecraft.
As the flywheel system is a life long technology.
