22-07-2014, 03:27 PM
Design of flywheel for improved energy storage using computer aided analysis
[attachment=66128]
Abstract
Flywheels serve as kinetic energy storage and retrieval devices with the ability
to deliver high output power at high rotational speeds as being one of the
emerging energy storage technologies available today in various stages of
development, especially in advanced technological areas, i.e., spacecrafts.
Today, most of the research efforts are being spent on improving energy
storage capability of flywheels to deliver high power at transfer times, lasting
longer than conventional battery powered technologies. Mainly, the
performance of a flywheel can be attributed to three factors, i.e., material
strength, geometry (cross-section) and rotational speed. While material
strength directly determines kinetic energy level that could be produced safely
combined (coupled) with rotor speed, this study solely focuses on exploring
the effects of flywheel geometry on its energy storage/deliver capability per
unit mass, further defined as Specific Energy. Proposed computer aided
analysis and optimization procedure results show that smart design of
flywheel geometry could both have a significant effect on the Specific Energy
performance and reduce the operational loads exerted on the shaft/bearings
due to reduced mass at high rotational speeds. This paper specifically studies
the most common five different geometries (i.e., straight/concave or convex
shaped 2D
Introduction
A flywheel is a mechanical device with a significant moment of inertia used as a
storage device for rotational energy. Flywheels resist changes in their rotational
speed, which helps steady the rotation of the shaft when a fluctuating torque is
exerted on it by its power source. flywheels have become the subject of extensive
research as power storage devices for uses in vehicles. flywheel energy storage
systems are considered to be an attractive alternative to electrochemical batteries
due to higher stored energy density, higher life term, deterministic state of charge
and ecologically clean nature.
1.2 Flywheel Origins
The origins and use of flywheel technology for mechanical energy storage began several
hundred years ago and developed throughout the Industrial Revolution. One of the first
modern dissertations on the theoretical stress limitations of rotational disks is the work by
Dr.A.Stodola, whose first translation to English was made in 1917. Development of
advanced flywheel begins in the 1970s.
1.3 Comparison among Alternative Forms of Energy Storage
Chemical batteries are widely used in many applications currently. But there are a
number of drawbacks of chemical batteries.
1. Narrow operational temperature range. The performance of the chemical battery will
be deteriorated sharply at high or low temperature.
2. Capacity decreases over life. The capacity of the chemical battery cannot be
maintained in a high level all through its life, the capacity will decrease with time goes on.
3. Difficulty in obtaining charge status. It is not so easy to know the degree of the charge
of the chemical battery because the chemical reaction in the battery is very hard to measure
and control.
4. Overcharge and over-discharge. Chemical battery can neither be over-discharged nor
be over-charged, or its life will be shorted sharply.
5. Environmental concerns. Many elements of the chemical battery are poisonous, they
will do harm to the environment and the people.
Obviously, the presence of the shortcomings of the chemical batteries makes them not
1.5 Applications
1.51Transportation
In the 1950s flywheel-powered buses, known as gyrobuses, were used in Yverdon,
Switzerland, and there is ongoing research to make flywheel systems that are smaller,
lighter, cheaper, and have a greater capacity. It is hoped that flywheel systems can replace
conventional chemical batteries for mobile applications, such as for electric vehicles.
Proposed flywheel systems would eliminate many of the disadvantages of existing battery
power systems, such as low capacity, long charge times, heavy weight, and short usable
lifetimes.
Advanced flywheels, such as the 133 kW·h pack of the University of Texas at Austin, can
take a train from a standing start up to cruising speed.
The Parry People Mover is a railcar which is powered by a flywheel. It was trialed on
Sundays for 12 months on the Stourbridge Town Branch Line in the West Midlands,
England during 2006 and 2007, and will be introduced as a full service by the train
operator London Midland in December 2008 once two units have been ordered.
1.52 Uninterruptible power supply
1.61 Advantages
Flywheels store energy very efficiently (high turn-around efficiency) and have the
potential for very high specific power(~ 130 W·h/kg, or ~ 500 kJ/kg) compared with
batteries. Flywheels have very high output potential and relatively long life.
Flywheels are relatively unaffected by ambient temperature extremes. The energy
efficiency (ratio of energy out per energy in) of flywheels can be as high as 90%.
Typical capacities range from 3 kWh to 133 kWh. Rapid charging of a system occurs
in less than 15 minutes.
Conclusion
After the successful application of proposed procedure outlined in the
previous section, all four steps are executed and equivalent stress distribution
contours are obtained for all six geometries. Kinetic Energy, mass and
maximum equivalent stress obtained in step 2 and 3, are also presented in
Table 2. The maximum stress criterion is used as failure criterion. This implies
that after the optimization in step 4, maximum allowable Equivalent stresses
could be as high as (red colored area), σY = 290 MPa, for AISI 1006 Steel
(cold drawn, even material). Minimum Equivalent stresses are calculated to
be in the range of 120–200 MPa, therefore they are considered to be within
the safe stress interval
[attachment=66128]
Abstract
Flywheels serve as kinetic energy storage and retrieval devices with the ability
to deliver high output power at high rotational speeds as being one of the
emerging energy storage technologies available today in various stages of
development, especially in advanced technological areas, i.e., spacecrafts.
Today, most of the research efforts are being spent on improving energy
storage capability of flywheels to deliver high power at transfer times, lasting
longer than conventional battery powered technologies. Mainly, the
performance of a flywheel can be attributed to three factors, i.e., material
strength, geometry (cross-section) and rotational speed. While material
strength directly determines kinetic energy level that could be produced safely
combined (coupled) with rotor speed, this study solely focuses on exploring
the effects of flywheel geometry on its energy storage/deliver capability per
unit mass, further defined as Specific Energy. Proposed computer aided
analysis and optimization procedure results show that smart design of
flywheel geometry could both have a significant effect on the Specific Energy
performance and reduce the operational loads exerted on the shaft/bearings
due to reduced mass at high rotational speeds. This paper specifically studies
the most common five different geometries (i.e., straight/concave or convex
shaped 2D
Introduction
A flywheel is a mechanical device with a significant moment of inertia used as a
storage device for rotational energy. Flywheels resist changes in their rotational
speed, which helps steady the rotation of the shaft when a fluctuating torque is
exerted on it by its power source. flywheels have become the subject of extensive
research as power storage devices for uses in vehicles. flywheel energy storage
systems are considered to be an attractive alternative to electrochemical batteries
due to higher stored energy density, higher life term, deterministic state of charge
and ecologically clean nature.
1.2 Flywheel Origins
The origins and use of flywheel technology for mechanical energy storage began several
hundred years ago and developed throughout the Industrial Revolution. One of the first
modern dissertations on the theoretical stress limitations of rotational disks is the work by
Dr.A.Stodola, whose first translation to English was made in 1917. Development of
advanced flywheel begins in the 1970s.
1.3 Comparison among Alternative Forms of Energy Storage
Chemical batteries are widely used in many applications currently. But there are a
number of drawbacks of chemical batteries.
1. Narrow operational temperature range. The performance of the chemical battery will
be deteriorated sharply at high or low temperature.
2. Capacity decreases over life. The capacity of the chemical battery cannot be
maintained in a high level all through its life, the capacity will decrease with time goes on.
3. Difficulty in obtaining charge status. It is not so easy to know the degree of the charge
of the chemical battery because the chemical reaction in the battery is very hard to measure
and control.
4. Overcharge and over-discharge. Chemical battery can neither be over-discharged nor
be over-charged, or its life will be shorted sharply.
5. Environmental concerns. Many elements of the chemical battery are poisonous, they
will do harm to the environment and the people.
Obviously, the presence of the shortcomings of the chemical batteries makes them not
1.5 Applications
1.51Transportation
In the 1950s flywheel-powered buses, known as gyrobuses, were used in Yverdon,
Switzerland, and there is ongoing research to make flywheel systems that are smaller,
lighter, cheaper, and have a greater capacity. It is hoped that flywheel systems can replace
conventional chemical batteries for mobile applications, such as for electric vehicles.
Proposed flywheel systems would eliminate many of the disadvantages of existing battery
power systems, such as low capacity, long charge times, heavy weight, and short usable
lifetimes.
Advanced flywheels, such as the 133 kW·h pack of the University of Texas at Austin, can
take a train from a standing start up to cruising speed.
The Parry People Mover is a railcar which is powered by a flywheel. It was trialed on
Sundays for 12 months on the Stourbridge Town Branch Line in the West Midlands,
England during 2006 and 2007, and will be introduced as a full service by the train
operator London Midland in December 2008 once two units have been ordered.
1.52 Uninterruptible power supply
1.61 Advantages
Flywheels store energy very efficiently (high turn-around efficiency) and have the
potential for very high specific power(~ 130 W·h/kg, or ~ 500 kJ/kg) compared with
batteries. Flywheels have very high output potential and relatively long life.
Flywheels are relatively unaffected by ambient temperature extremes. The energy
efficiency (ratio of energy out per energy in) of flywheels can be as high as 90%.
Typical capacities range from 3 kWh to 133 kWh. Rapid charging of a system occurs
in less than 15 minutes.
Conclusion
After the successful application of proposed procedure outlined in the
previous section, all four steps are executed and equivalent stress distribution
contours are obtained for all six geometries. Kinetic Energy, mass and
maximum equivalent stress obtained in step 2 and 3, are also presented in
Table 2. The maximum stress criterion is used as failure criterion. This implies
that after the optimization in step 4, maximum allowable Equivalent stresses
could be as high as (red colored area), σY = 290 MPa, for AISI 1006 Steel
(cold drawn, even material). Minimum Equivalent stresses are calculated to
be in the range of 120–200 MPa, therefore they are considered to be within
the safe stress interval