I am grateful to Proof. R. K. Shoo, Head of the Department of Mechanical Engineering, for permitting me to make use of the facilities available in the department to carry out the project successfully. Last but not the least I express my sincere thanks to all f my friends who have patiently extended all sorts of help for accomplishing this undertaking. Finally I extend my gratefulness to one and all who are directly or indirectly involved in the successful completion of this project work.
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 search efforts are being spent on improving energy storage capability of flywheels 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 Lowell 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.
As shown in Fig, a typical yester consists of a flywheel, a motor/generator, and controlled electronics for connection to a larger electric power system. Figure 1. 1 Basic components of flywheel wheel energy storage system The input power may differ from the output power in its temporal profile, frequency, or other attributes. It is converted by the input electronics into a form appropriate for efficiently driving a variable-speed motor. The motor spins the flywheel, which stores energy mechanically, slowing down as it delivers energy to a load.
That decrease in mechanical energy is converted into electrical form by the generator. A challenge acing the motor and the generator designer is to size the system for the amount of storage (energy) and delivery rate (power) required and also to minimize losses. The output electronics convert the variable-frequency output from the generator into the electric power required by the load. Since the input and output are typically separated in a timely manner, many approaches combine the motor and generator into a single machine, and place the xi input and output electronics into a single module, to reduce weight and cost.
Modern high-speed flywheels differ from their forebears in being lighter and spinning much faster. Since the energy stored in a flywheel increases only linearly with its moment of inertia but goes up as the square of its rotational speed, the tradeoff is a good one. But it do raise two issues: flywheel strength and losses caused due to air friction. To keep from flying apart, modern flywheels are complex structures based on extremely strong materials like carbon fibers. 1. 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 Development of advanced flywheel begins in the sass. 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 he 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 nontoxic so-appealing to the users nowadays. Instead, flywheel energy storage system become potential alternative form of energy storage. Lead-acid Flywheel battery Storage mechanism Chemical Mechanical Life(years in service) 3-5 Technology Promising Number of manufacturers -700 -10 -7000 -2 Temperature range Limited Less Limited Environmental concerns Disposal issues Slight Larger Smallest $50-$100 $400-$800 Annual sales(us $millions) Relative size (equivalent power/energy) Price, per kilowatt system .
Given the state of development of flywheel batteries , it is expected that costs for flywheel can be lowered with further technical development. On the other hand, electrochemical batteries already have a tremendous economy of scale that has driven costs down as far as they are likely to go. Besides what have been mentioned in table, there are also some other potential advantages that flywheel energy storage system has over chemical battery. Refer to: 1 . Higher energy storage density. The flywheel battery whose speed exceeds error/ min can generate more than rowers/lbs energy .
But the energy storage density of the nickel-hydrogen battery is only 5-6 Hrs/lb. 2. No capacity decreases over life. The life of the flywheel battery depends mainly on the life of power electronic devices and can reach about 20 years. 3. No overcharge and over-discharge. The performance of the flywheel battery is not influenced when t is discharged heavily, and the overcharge can be avoided with assistance of power electronic devices. 4. Since mechanical energy is proportional to the square of the flywheel speed, the stored energy level indicator is a simple speed measurement.
In addition, the charge of the flywheel battery can be restored in several minutes, but it will take about several hours for chemical battery to charge. Energy is stored in the rotor as kinetic energy, or more specifically, rotational energy: where w is the angular velocity, and I is the moment of inertia of the mass about the center of rotation. The moment of inertia for a solid-cylinder is for a thin-walled cylinder is and for a thick-walled cylinder is where m denotes mass, and r denotes a radius.
More information can be found at list of moments of inertia When calculating with SSL units, the standards would be for mass, kilograms; for radius, meters; and for angular velocity, radians per second. The resulting answer The amount of energy that can safely be stored in the rotor depends on the point at which the rotor will warp or shatter. The hoop stress on the rotor is a major consideration in the design of a flywheel energy storage system. Xiv t is the tensile stress on the rim of the cylinder p is the density of the cylinder r is the radius of the cylinder, and w is the angular velocity of the cylinder. . 5 Applications 1. 51 Transportation In the sass flywheel-powered buses, known as grouses, were used in Hovered, 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 skew 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 Sturbridge 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 Flywheel power storage systems in current production (2001) have storage capacities comparable to batteries and faster discharge rates.
They are mainly used to provide load leveling for large battery systems, such as an uninterruptible power supply for data centers. Flywheel maintenance in general runs about one-half the cost of traditional battery UPS systems. The only maintenance is a basic annual preventive maintenance routine and replacing the bearings every three years, which takes about four hours. 1. 53 Amusement ride The Incredible Hulk roller coaster at Universals Islands of Adventure features a vapidly accelerating uphill launch as opposed to the typical gravity drop.
This is achieved through powerful traction motors that throw the car up the track. To achieve the brief very high current required to accelerate a full coaster train to full speed uphill, the park utilizes several motor generator sets with large flywheels. Without these stored energy units, the park would have to invest in a new substation and risk browning-out the local energy grid every time the ride launches. The VIA has re-allowed the use of KERR (see kinetic energy recovery system) as part of its Formula 1 2009 Sporting Regulations.
Using a continuously variable transmission (C.V.), energy is recovered from the drive train during braking and stored in a flywheel. This stored energy is then used during acceleration by altering the ratio of the C.V.. In motor sports applications this energy is used to improve acceleration rather than reduce carbon dioxide emissions-?although the same technology can be applied to road cars to improve fuel efficiency. 1. 55 Flywheel energy storage systems are widely used in space, hybrid vehicles, military field and power quality. Space station, satellites, aircraft are the main application field in space.
In these fields, flywheel systems function as energy storage and attitude control. For the applications in hybrid vehicles and military field, flywheel systems are mostly used to provide pulse power. But for power quality application, flywheel systems are widely used in USPS, to offer functions of uninterruptible power and voltage control. Xvi Figure 1. 2 Applications of Flywheel Energy Storage System Figure 3 shows an example of NASA on the FESS development. The blue arrows represent energy storage combined with attitude control, which mostly used in space stations, satellites, and so on.
Red arrow represents pulse power, which are used in aircrafts, combat vehicles and hybrid electric vehicles. Green arrow represents uninterruptible power & voltage control, which is used in UPS, aircraft launch and utility peaking. From the figure, we can see that Anna’s near term researches on flywheel are mostly concentrated on space applications, but the far term researches are turning to industry applications gradually.