Flywheel Energy Storage Device Research Articles

Performance Prediction of Inertial Auto-Reinforce Magnetic Flywheel Energy Storage Device Using Finite Element Magnetic Modeling

A new feature for flywheel energy storage device is proposed considering the deficiencies in former technology. This feature is introduced as auto-reinforce performance which means giving-back the kinetic energy for flywheel after speed-down occurred (as result of sudden loading). Auto-reinforce performance is an ability to recover the kinetic rotational energy which significantly keeps longer the stored energy of a flywheel device. This novel concept of flywheel is engineered by installing a number of Permanent Magnets (PM) in certain mounting. Hence, the magnetism configuration such magnetic strength, magnetic energy density, pole direction, geometry, and dimension are influential parameters to the mechanical performance. By practicing Finite Element Magnetic Modeling (FEMM), it is possible to predict some designed mechanical parameters such magnetic force and magnetic torque. Finally by evaluating these mechanical parameters, the key performance of this device such as percentage of energy reinforcement and percentage of discharge elongation can be predicted. The main ideas of this paper are: 1) presenting the development stages especially in design prediction using Finite Element Analysis (FEA) software; and 2) discovering the correlation of designed magnetic properties and mechanical parameters for prototyping references.

Control of a Flywheel Energy Storage System for Power Smoothing in Wind Power Plants

This paper deals with the design and the experimental validation in scale-lab test benches of an energy management algorithm based on feedback control techniques for a flywheel energy storage device. The aim of the flywheel is to smooth the net power injected to the grid by a wind turbine or by a wind power plant. In particular, the objective is to compensate the power disturbances produced by the cycling torque disturbances of the wind turbines due to the airflow deviation through its tower section. This paper describes the control design, its tuning, as well as the description of the experimental setup, and the methods for the experimental validation of the proposed concepts. Results show that the fast wind power fluctuations can be mostly compensated through the flywheel support.

Auto-reinforce Magnetic Flywheel as Recent Advancement of Automobile Flywheel

A new feature for flywheel energy storage device is proposed, considering the deficiencies on existing technology. This feature is introduced as auto-reinforce performance which means an ability to recover the kinetic energy after speed-down occurred as impact of sudden loading or sudden braking. The performance will significantly keep longer the stored energy of a flywheel device. This novel concept of flywheel is engineered by installing a number of Permanent Magnets (PM). The magnetism configuration such magnetic strength, magnetic energy density, pole direction, geometry, and dimension are influential parameters to its performance. By executing Finite Element Magnetic Modeling, it is possible to predict the design parameters such magnetic force and magnetic torque. Finally by evaluating these mechanical parameters, the key performance of this device such as percentage of energy reinforcement and percentage of discharge elongation can be predicted for prototyping references.

The Optimization of Power Smoothing Control Strategy for Wind Farm Based on Flywheel Energy Storage Device

The instability and intermittency of wind makes the output power of the wind turbine randomness and volatility. Due to its fast pulse response and high charge-discharge rate, the flywheel energy storage can effectively reduce the power fluctuations caused by the wind farm. This article optimized the control strategy for the permanent magnet synchronous motor (PMSM) based flywheel energy storage system to reduce the active power fluctuations. Fuzzy inference method is used to make the desired smoothing active power value more precise. The rotor flux oriented vector control strategy with improved proportional resonant controller (PR controller) is proposed based on the mathematical model of PMSM to improve the robustness of the system in current control.

The Application of Flywheel Energy Storage Device in Marine Gas Turbine Generator Set

Marine gas turbine generator set; Flywheel energy; Stability Abstract. Based on modular modeling idea, the modular model of marine generation system was set by the technology of systematic simulation. One set of simulation models of marine gas turbine generation system was generated. Results show that flywheel energy storage device can enhance the stability of power grid and play a better role in making marine gas turbine generation system stable under heavy load fluctuations.

Rotor Losses in a Switched Reluctance Motor - Analysis and Reduction Methods

Due to the increasing hybridization and electrification of vehicles, flywheel energy storage devices are an important area of research. In automotive application besides the weight criteria, some additionally con- strains, such as size, e! ciency and especially cost have to be fulfilled. Therefore typically a compact design, in which the rotor of the needed electrical machine simultaneously acts as storage mass is chosen. Since the machine is running in vacuum and the rotor can dissipate its heat only by means of thermal radiation or through the bearings if conventional bearings are used, the rotor losses play a vital role. In this work the rotor losses of a switched reluctance machine are analyzed in detail and a method to reduce the rotor losses is proposed.

Improving the Integration of Wind Power Generation Into AC Microgrids Using Flywheel Energy Storage

The connection of wind power generation into ac microgrids (MGs) is steadily increasing. This incorporation can bring problems onto the power quality and dynamics of the electrical grid due to the lack of controllability over the wind. In this work, a flywheel energy storage (FES) is used to mitigate problems introduced by wind generation into MGs. A dynamic model of the FES device is briefly presented and a technique to control the power exchanged between the device and the power system is proposed. The control technique has three modes, namely: voltage control (VC), frequency control (FC), and active power stabilization (APS). Simulation tests on the behavior of the FES device are analyzed when it works in combination with wind generation in the electrical microgrid. Results show an acceptable performance of the proposed control techniques along with a high effectiveness to smooth the active power fluctuations of wind generation.

A Study on the Stability of Marine Gas Turbine Generation Module Power System

Based on modular modeling idea, the modular model of marine generation system was set by the technology of systematic simulation. One set of simulation models of marine gas turbine generation system was generated. Results show that flywheel energy storage device can enhance the stability of power grid and play a better role in making marine gas turbine generation system stable under heavy load fluctuations.

A Novel Energy Storage System based on Flywheel for Improving Power System Stability

In this paper, a novel flywheel energy storage device, called the flexible power conditioner, which integrates both the characteristics of the flywheel energy storage and the doubly-fed induction machine, is proposed to improve power system stability. A prototype is developed and its principle, composition, and design are described in detail. The control system is investigated and the operating characteristics are analyzed. The test results based on the prototype are presented and evaluated. The test results illustrate that the prototype meets the design requirement on power regulation and starting, and provides a cost-effective and effective means to improve power system stability.

Interaction of bulk superconductors with flywheel rings made of multiple permanent magnets

Compared to conventional mechanical bearings, superconducting bearings have the advantage that there is no friction loss. Thus the superconducting bearings are employed for a flywheel energy storage device, and thereby one can construct the system that stores the energy for a long duration. Hence, superconducting flywheel energy storage system has attracted worldwide attention. For practical applications of the superconducting energy storage system, the stored energy must be maximized that can be achieved by either increasing the diameter of the levitated flywheel or the rotational velocity. Since the suspended flywheel in the superconducting flywheel energy storage system is made of permanent magnets, its size is limited by the size of permanent magnets. In addition, when the rotational speed is increased, there is possibility for the magnet ring to fracture due to a large centrifugal force. We therefore proposed the construction of the magnetic flywheel ring by simply arranging small permanent magnets pasted into machined grooves in Al disk 650 mm in diameter. Then we measured the force interaction between superconductor sample and a invented flywheel design. We have found that the field is almost uniform when the distance from the flywheel surface exceeded 15 mm, showing that frictionless rotation is possible at the gap larger than 15 mm. Furthermore, the repulsive force density was 0.48 N/cm 2 at 15 mm, which demonstrates that the mass of 161.32 kg can be levitated.

Disturbance Attenuation Using a dc Motor for Radial Force Actuation in a Rotordynamic System

This paper presents a technique for attenuating the external disturbances acting on the rotor of a prototype flywheel energy storage device. The approach uses a three-phase axial flux brushless dc motor to simultaneously produce a torque and a radial force. This is accomplished by using two phases of the motor for torque generation, and one phase to produce the radial force. The paper develops a set of equations that can be used to predict the forces generated by the motor coils. These equations are used to implement a feedback control system to suppress the effects of external excitations. The nonlinear controller requires the velocity measurements and the angular displacement of the flywheel. The controller essentially adds damping to the system, and the constant feedback gains solve an optimization problem that involves a H∞ bound on the disturbance attenuation. The experimental results clearly demonstrate that the dc motor can be used to suppress unwanted radial vibrations due to external disturbances.

Simulation-Based Evaluation of Electronic Energy Storage Devices in Buses for Reducing Emissions

Emerging concerns about emissions and increasing energy costs have led to interest in developing and applying electronic devices for energy storage (popularly known as flywheel batteries or simply flywheels) in transportation applications to recover the energy used in braking rather than dissipating it as heat. Each time a vehicle stops, its kinetic energy is dissipated as heat. Fuel is then used to accelerate the vehicle again. A flywheel energy storage device that stores the braking energy and then reuses it for acceleration has the potential to improve fuel economy and reduce pollution. It is important to evaluate the application of this technology in transit buses to assess better any need for increased development. A three-step computer simulation is used to evaluate the reduced emissions of carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxides (NOx) in a flywheel-equipped bus. First, drive cycles over which buses operate are specified. Second, because flywheel energy storage reduces the effects of acceleration and deceleration to the engine, the emissions models (which are sensitive to acceleration and deceleration modes) are identified and selected. Finally, emissions are computed and compared with emissions for a bus without a flywheel. Results indicate conceptually that the flywheel application reduces acceleration effects, which in turn significantly reduce emissions. It is therefore strongly recommended that the flywheel energy storage device be further researched for transportation applications.

Formation mechanism of defects around the Y211 inclusion trapped within the melt-textured Y123 domain

The melt processed Y123 oxide superconductor shows a very high magnetic levitation force and there is lots of research to develop its application technology such as a fly wheel energy storage device. Our recent study on the microstructure of the melt-processed samples showed that oxygenation condition significantly affected the magnetic properties of the YBCO sample. We examined the microstructure around the Y211 inclusion trapped within the melt-textured domain to understand the formation mechanism of the defects such as CuO stacking faults, dislocations and BaCuO platelet boundaries. The microstructures of the YBCO samples were heat-treated in flowing oxygen for various times. No defects were observed around the trapped Y211 inclusions and in the Y123 matrix of the tetragonal sample. Meanwhile, dislocation, transformation twins, the CuO stacking fault and BaCuO platelet structure were observed in the sample transformed into superconducting orthorhombic phase by low temperature heat treatment. The CuO stacking fault and BaCuO platelet structure are developed along the [100] and [010] direction on the a-b plane of the orthorhombic Y123. The formation mechanism of the defects was discussed on the basis of the oxygenation-induced decomposition mechanism.

Combustion driven pulsed linear generators for electric gun applications

Energy storage and pulse forming for electromagnetic and electro-thermal chemical guns has historically been accomplished through the use of complex power trains. Such power trains typical involve a prime power source, electrical or mechanical power conversion devices, capacitive or flywheel energy storage devices, and sophisticated switching and control elements. Kaman Electromagnetics (KEC) has developed concepts for simpler pulse power systems where chemical energy is converted more directly into an electrical output which can be utilized by an electric gun load without further conditioning. One family of devices which has shown considerable promise is the linear flux compressor. Early work with flux compressors used explosives and was suited only for microsecond duration pulses. More recent efforts utilizing propellants and even conventional hydrocarbon fuels can provide millisecond duration pulses which are well suited for electric gun type loads. Internally funded efforts indicate linear flux compressor pulse power supplies can be considerable smaller and lighter than conventional systems. This paper presents the operational principles and design issues of linear flux compressors suitable for EM guns. Point designs, performance simulations and general scaling relationships are also presented.

Performance of a magnetically suspended flywheel energy storage device

This paper describes a high-power flywheel energy storage device with 1 kWh of usable energy. A possible application is to level peaks in the power consumption of seam-welding machines. A rigid body model is used for controller design, stability, and robustness analysis. Flywheel systems tend to have strong gyroscopic coupling which must be considered in the controller design. The gyroscopic coupling can cause instability in addition with system nonlinearities, digitization, time delay, filter characteristics, and adaptive unbalance cancellation. Different approaches, such as decentralized control, controller design with a linear quadratic regulator (LQR), and cross feedback control are analyzed. Cross feedback control leads to a better system performance and is easy to implement. Experimental results are given. The startup behavior and the disturbing forces of the system while rotating are shown.

Design principles for a flywheel energy store for road vehicles

This paper introduces a flywheel energy storage device capable of enhancing the fuel economy of a hybrid-type road vehicle. A number of possible drive types is considered and the permanent magnet machine drive is shown to provide the best solution. Reasons for selecting a device using an axial-field configuration with single rotor and double stator sections are described. Electrical, magnetic and mechanical design data are presented for a full-scale prototype device with 240 kJ of usable energy storage and 25 kW of power transfer, operating at speeds up to 50000 revs per minute, with a 10% duty cycle.