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With the increasing proportion of renewable energy power generation, its accompanying intermittency and volatility problems are becoming increasingly prominent, and the frequency fluctuation of the power system is becoming increasingly severe. Participation in frequency regulation services can be economically rewarding for generating units. The flywheel energy storage system can effectively improve the frequency regulation capability of coal-fired units. In this paper, the improvement of the FM capability of coal-fired units in the operation of a two-area interconnected power system containing wind power is investigated, and a model of a two-area interconnected power system comprising a turbine generator, wind power, and flywheel energy storage is established. The enhancement of the FM capability of coal-fired units by adding a flywheel energy storage system is analyzed. The simulation results show that adding the flywheel energy storage system improves the FM capability of the coal-fired unit to a considerable extent, and the coal-fired unit can decide the flywheel capacity it needs to be equipped with through detailed economic calculations. [ABSTRACT FROM AUTHOR]

Copyright of Zhejiang Electric Power is the property of Zhejiang Electric Power Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Amidst the growing demand for efficient and sustainable energy storage solutions, Flywheel Energy Storage Systems (FESSs) have garnered attention for their potential to meet modern energy needs. This study uses Computational Fluid Dynamics (CFD) simulations to investigate and optimise the aerodynamic performance of FESSs. Key parameters such as radius ratio, aspect ratio, and rotational velocity were analysed to understand their impact on windage losses and heat transfer. This study reveals the critical role of Taylor–Couette flow on the aerodynamic performance of FESSs. The formation of Taylor vortices within the airgap was examined, demonstrating their effect on temperature distribution and overall system performance. Through a detailed examination of the skin friction coefficient and Nusselt number under different conditions, this study identified a nonlinear relationship between rotor temperature and rotational speed, highlighting the accelerated temperature rise at higher speeds. The findings indicate that optimising these parameters can significantly enhance the efficiency of FESSs, reducing windage losses and improving heat transfer. This research provides valuable insights into the aerodynamic and thermal optimisation of FESSs, offering pathways to improve their design and performance. The results contribute to advancing guidelines for the effective implementation of FESSs in the energy sector, promoting more sustainable energy storage solutions. [ABSTRACT FROM AUTHOR]

To address the issue of insufficient grid inertia support caused by the large-scale integration of renewable energy， a synchronous condenser model of a flywheel energy storage system， along with a control scheme， is developed based on permanent magnet variable frequency speed regulation. This model integrates a flywheel energy storage system with permanent magnet variable frequency speed regulation on the rotor of the synchronous condenser. By utilizing the kinetic energy of the flywheel， the inertia power response capability of the synchronous condenser is enhanced without altering its grid connection method or rapid excitation capability. Both the electromagnetic and mechanical models of the permanent magnet speed-regulated motor and the synchronous condenser of the flywheel energy storage system are constructed. Additionally， a dual-channel coupled power output model that includes the synchronous condenser and the frequency converter is established. Based on this， the paper proposes a power control strategy for synchronous condenser frequency regulation of the flywheel energy storage system using permanent magnet variable frequency speed regulation. Simulations under typical application scenarios have verified the feasibility and effectiveness of this strategy.

In supporting the stable operation of high-penetration renewable energy grids, flywheel energy storage systems undergo frequent charge–discharge cycles, resulting in significant stress fluctuations in the rotor core. This paper investigates the fatigue life of flywheel energy storage rotors fabricated from 30Cr2Ni4MoV alloy steel, attempting to elucidate the material's mechanical properties, crack propagation behavior, and impact of internal defects on fatigue life. Tensile tests reveal that the material exhibited high yield (992 MPa) and tensile strengths (1130 MPa). The Paris formula is used to model crack growth rates, ending in good agreement with the experimental data. Fatigue tests at various stress conditions highlight the material's significant variability in fatigue life and emphasize the need for reliable design approaches. This paper also demonstrates that internal defect size and location critically affect fatigue life, calling for improvements in forging inspection standards. Overall, the present study provides a comprehensive analysis of 30Cr2Ni4MoV steel's suitability for flywheel rotors, balancing safety, and operational efficiency. [ABSTRACT FROM AUTHOR]

Aiming at the excessive power fluctuation of large-scale wind power plants as well as the consumption performance and economic benefits of wind power curtailment, this paper proposes a hybrid energy storage capacity configuration strategy for virtual power plants based on variable-ratio natural gas-hydrogen blending. Firstly, a natural gas-hydrogen blending virtual power plant architecture with the synergy of power-to-gas and carbon capture is established in terms of low-carbon performance, and then a natural gas-hydrogen blending capacity configuration with the synergy of carbon capture and power-to-gas is carried out for the architecture. Secondly, the mathematical modeling is carried out for the liquid storage carbon capture, power-to-gas, hydrogen storage, flywheel energy storage, hydrogen blending gas turbine and hydrogen blending gas boiler. Finally, the objective function of minimizing the cost of carbon trading and storage, the cost of startup and shutdown of coal-fired units and the cost of coal consumption, the cost of wind power curtailment, the cost of purchasing gas, the cost of power-to-gas, the cost of hydrogen blending, and the cost of hydrogen blending is proposed based on the modelings. After the linearization of the models, the Gurobi commercial solver was invoked through MATLAB software to solve the model, and five scenarios were set up for comparative analysis. The results further verified the effectiveness of the proposed strategy. • Empirical mode decomposition algorithm is used to achieve wind power decomposition. • Flywheel energy storage is configured to suppress the wind power. • In-depth analysis of hydrogen blending ratios improves economic benefits. [ABSTRACT FROM AUTHOR]

The literature written in Chinese mainly and in English with a small amount is reviewed to obtain the overall status of flywheel energy storage technologies in China. The theoretical exploration of flywheel energy storage (FES) started in the 1980s in China. The experimental FES system and its components, such as the flywheel, motor/generator, bearing, and power electronic devices, were researched around thirty years ago. About twenty organizations devote themselves to the R&D of FES technology, which is developing from theoretical and laboratory research to the stage of engineering demonstration and commercial application. After the research and accumulation in the past 30 years, the initial FES products were developed by some companies around 10 years ago. Today, the overall technical level of China’s flywheel energy storage is no longer lagging behind that of Western advanced countries that started FES R&D in the 1970s. The reported maximum tip speed of the new 2D woven fabric composite flywheel arrived at 900 m/s in the spin test. A steel alloy flywheel with an energy storage capacity of 125 kWh and a composite flywheel with an energy storage capacity of 10 kWh have been successfully developed. Permanent magnet (PM) motors with power of 250–1000 kW were designed, manufactured, and tested in many FES assemblies. The lower loss is carried out through innovative stator and rotor configuration, optimizing magnetic flux and winding arrangement for harmonic magnetic field suppression. Permanent magnetic bearings with high load ability up to 50–100 kN were developed both for a 1000 kW/16.7 kWh flywheel used for the drilling practice application in hybrid power of an oil well drilling rig and for 630 kW/125 kWh flywheels used in the 22 MW flywheel array applied to the flywheel and thermal power joint frequency modulation demonstration project. It is expected that the FES demonstration application power stations with a total cumulative capacity of 300 MW will be built in the next five years.

Amidst the growing demand for efficient and sustainable energy storage solutions, Flywheel Energy Storage Systems (FESSs) have garnered attention for their potential to meet modern energy needs. This study uses Computational Fluid Dynamics (CFD) simulations to investigate and optimise the aerodynamic performance of FESSs. Key parameters such as radius ratio, aspect ratio, and rotational velocity were analysed to understand their impact on windage losses and heat transfer. This study reveals the critical role of Taylor–Couette flow on the aerodynamic performance of FESSs. The formation of Taylor vortices within the airgap was examined, demonstrating their effect on temperature distribution and overall system performance. Through a detailed examination of the skin friction coefficient and Nusselt number under different conditions, this study identified a nonlinear relationship between rotor temperature and rotational speed, highlighting the accelerated temperature rise at higher speeds. The findings indicate that optimising these parameters can significantly enhance the efficiency of FESSs, reducing windage losses and improving heat transfer. This research provides valuable insights into the aerodynamic and thermal optimisation of FESSs, offering pathways to improve their design and performance. The results contribute to advancing guidelines for the effective implementation of FESSs in the energy sector, promoting more sustainable energy storage solutions.

The flywheel energy storage system (FESS) is a cutting-edge device that stores electrical energy with great efficiency by using a revolving rotor that transforms electrical energy into kinetic energy. Flywheel systems provide some benefits, including cheap maintenance costs, a long lifespan, quick reaction times, and an excellent round-trip efficiency of over 90%. Because of these qualities, FESS has a lot of promise in the energy sector. As a result, the study looked at the system's architecture, characteristics, and contributions to future improvements. To provide the essential knowledge and understanding about the technologies and applications of FESS, this study gave an informative overview of its structure and components by conducting a literature search and screening to clearly define the structure and components. Amber Kinetics, an industry leader in manufacturing FESS, collaborated on the research, which resulted in a descriptive characterization and interpretation of it in terms of control method, stability enhancement, and future possibilities. The M32 Flywheel is composed of 98% steel. It has a mechanical battery that does not decrease in function, unlike lithium-ion batteries, which are chemically based, prone to fire, and difficult to dispose of. FESS significantly contributes to the existing energy market by consistently storing and preserving energy and augmenting and delivering the power required by consumer requests. [ABSTRACT FROM AUTHOR]

Transient power fluctuations may occur in shipboard DC microgrids when switching a pulsed power load (PPL). However, shipboard power systems (SPSs) are isolated power grids with relatively low inertia and capacity, making them unable to respond immediately to sudden changes in pulsed loads, thereby resulting in considerable disturbances and even instability of the system. To mitigate such disturbances effectively, it is recommended to introduce energy storage devices to SPSs. In order to better leverage the buffering characteristics of energy storage devices, this paper establishes a simulation model of the SPS, which includes a micro gas turbine generator, a hybrid energy storage system (HESS), multiple PPLs and an energy management system (EMS). The HESS comprises a battery and a flywheel. Furthermore, a hierarchical coordinated control strategy for HESS in shipboard DC microgrids under multiple pulsed load conditions is proposed, which includes both an upper-layer control and a lower-layer control. The upper layer makes logical judgments through voltage difference and selects the appropriate energy storage mode for power supply. The lower layer adopts a series fuzzy logic control. To validate the effectiveness of the proposed control strategy, two scenarios of transient power mutation and total power demand exceeding the rated power of the generator were simulated by connecting different PPLs to the DC bus at different times. The results indicate that the control strategy effectively realizes the coordinated operation of HESS and gas turbine, as well as power allocation between flywheel and battery within HESS. Moreover, it reduces the frequency of charging and discharging of battery, improves battery life, and prevents the generator from running beyond the rated power.

With the rise of new energy power generation, various energy storage methods have emerged, such as lithium battery energy storage, flywheel energy storage (FESS), supercapacitor, superconducting magnetic energy storage, etc. FESS has attracted worldwide attention due to its advantages of high energy storage density, fast charging and discharging speed, high energy conversion rate, easy maintenance, and no environmental pollution, and has been applied in aerospace, military, electric power, and transportation fields. This article uses the citespace review tool to intrinsically analyze and summarize the papers published from 2010 to 2022 in the field of FESS. Relevant knowledge maps such as keywords and research hotspots that carry out FESS research were obtained. Since this technology is developing gradually ►The historical development of FESS is summarized in this article for new/existing researchers. Finally ►This paper presents the future development trend based on reviewed literatures.

In supporting the stable operation of high-penetration renewable energy grids, flywheel energy storage systems undergo frequent charge–discharge cycles, resulting in significant stress fluctuations in the rotor core. This paper investigates the fatigue life of flywheel energy storage rotors fabricated from 30Cr2Ni4MoV alloy steel, attempting to elucidate the material’s mechanical properties, crack propagation behavior, and impact of internal defects on fatigue life. Tensile tests reveal that the material exhibited high yield (992 MPa) and tensile strengths (1130 MPa). The Paris formula is used to model crack growth rates, ending in good agreement with the experimental data. Fatigue tests at various stress conditions highlight the material’s significant variability in fatigue life and emphasize the need for reliable design approaches. This paper also demonstrates that internal defect size and location critically affect fatigue life, calling for improvements in forging inspection standards. Overall, the present study provides a comprehensive analysis of 30Cr2Ni4MoV steel’s suitability for flywheel rotors, balancing safety, and operational efficiency.

Flywheel energy storage systems (FESS) used in short-duration grid energy storage applications can help improve power quality, grid reliability, and robustness. Flywheels are mechanical devices that can store energy as the inertia of a rotating disk. The energy capacity of FESS rotors can be improved by choosing the optimal rotor geometry, operation conditions, rotor materials, and by tailoring the material properties. A multi-objective formulation is presented in this article to simultaneously improve the energy capacity and reduce the weight of energy storage flywheels using stress-constrained topology optimization to determine the material placement and optimize the stress distribution in the rotor. A Pareto-front of optimal solutions to the multi-objective problem demonstrates that the rotors with the best specific energy content have volume fractions of 55-65%. Local stress constraints with an Augmented Lagrangian formulation are introduced to improve the stress distribution and optimal design and are compared to designs obtained with global stress constraints based on P-norm aggregation approach. We show that designs with local stress constraints have a more uniform stress distribution and fewer stress concentrations compared to stress using P-norm. [ABSTRACT FROM AUTHOR]

The study of material failure is crucial for the design of engineering applications, as it can have significant social and economic impacts. Carbon nanotubes (CNTs), with their exceptional electrical, mechanical, and thermal properties, hold immense potential for a wide range of cutting-edge applications such as superstrong fiber, lightning strike protector, and even space elevator. This review provides an overview of the advancement in understanding the mechanical and electrical failure study of CNTs and their assemblies, serving as a comprehensive reference for utilizing CNTs in various forms. To begin, we emphasize the importance of studying material failure and provide a brief introduction to CNTs. Subsequently, we explore the mechanical and electrical failure characteristics of CNTs and their assemblies, along with notable examples of applications that utilize their failure-resistant properties, such as flywheel energy storage and lightning strike protection. Lastly, we present perspectives associated with analyzing CNT failure and its implications for extreme applications. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The implementation of the “dual carbon” goal, nationally in China, has accelerated the profound transformation of the energy industry, and the development and utilization of large-scale clean energy has become a basic global consensus. However, clean energy is having trouble meeting the needs of rigid energy demands due to its randomness, intermittency, and unpredictability, so energy storage is currently being considered to solve this incompatibility. The flywheel energy storage system (FESS) cooperates with clean energy power generation to form “new energy + energy storage”, which will occupy an important position among new energy storage methods. This study analyzes the basic requirements of wind power frequency modulation, establishes the basic model of the flywheel energy storage system, adopts a six-phase permanent magnet synchronous motor as the system driver, designs an eleven-stage pulse width modulation control method, and proposes a power and current double-closed loop. The control strategy is used to test and simulate the machine-side converter that has been built. The results show that the proposed control strategy is reasonable and effective. By introducing a six-phase permanent magnet synchronous motor into FESS, the system could output higher power under the condition of low voltage and the noise and vibration of the motor are optimized during operation. Most importantly, the stability of the FESS is guaranteed in actual operation.

[Introduction] The primary frequency modulation technology of thermal power units has been considered essential to ensure the power grid's safe and stable operation. [Method] The current primary frequency modulation technology, the auxiliary primary frequency modulation technology, the coupled frequency modulation control strategy, and the potential development direction of primary frequency modulation technology were reviewed. [Result] The results show that the primary frequency modulation technology for the unit mainly includes regulating valve pre-throttling, adjustable regenerative steam extraction frequency modulation, and condensate water throttling frequency modulation. Among them, the condensate water throttling frequency modulation technology should be the main mode. Auxiliary primary frequency modulation technology is mainly based on the fast-response rate characteristics of flywheel energy storage and battery to meet the unit input and output requirements. The focus and difficulty of coupled auxiliary frequency modulation technology are then analyzed. The system modeling and control strategy research based on frequency modulation technology can optimize the matching between unit parameters. [Conclusion] Thus, the application status of primary frequency modulation technology in recent years is compared, and it is considered that flywheel energy storage primary frequency modulation and sliding pressure operation optimization will be the key development direction.

[Introduction] The proposal of the "carbon peak and neutrality" goal increases the necessity of new energy power embedding. To study the method to improve the flexibility of the unit, this paper introduces the flywheel energy storage technology and the related research of the coupled generator set in detail. [Method] The working principle, research status, and achievements of flywheel energy storage as well as application difficulties and measures were summarized, and the specific methods of studying the system modeling and operation strategy of flywheel energy storage were analyzed, and the principle and application characteristics of flywheel energy storage coupled with thermal power generation, wind power generation and solar power generation were analyzed emphatically. [Result] This paper shows that the research on flywheel energy storage systems in China has achieved relatively advanced results and formed a set of effective research methods, and some research has been done on the coupling of flywheel energy storage technology with multi-energy generator set. [Conclusion] In today's environment, flywheel energy storage technology coupled with multi-energy generators has become a research trend and focus, the summary of this paper provides a reference for the subsequent application of flywheel energy storage technology.

With the increasing pressure on energy and the environment, vehicle brake energy recovery technology is increasingly focused on reducing energy consumption effectively. Based on the magnetization effect of permanent magnets, this paper presents a novel type of magnetic coupling flywheel energy storage device by combining flywheel energy storage with magnetic coupling technology. As a high-efficiency energy storage device, it has the advantages of low energy consumption, low vibration, low noise and easy maintenance. In this paper, firstly, the structural characteristics and working process of vehicle brake energy recovery systems are analyzed, and experiments regarding the transmission and efficiency performance are carried out for key components; then a reasonable control strategy is formulated according to the principle of energy recovery; finally, the speed, acceleration, recovery energy and other parameters are analyzed based on the New European Driving Cycle (NEDC) working conditions. The results show that the energy recovery efficiency reaches 35.59%, which verifies the usability of the device. [ABSTRACT FROM AUTHOR]

In view of a whole series of problems such as the reduction of system inertia， the increase of frequency fluctuation， and the deterioration of power quality caused by large-scale wind power integration， a flywheel with high power density is designed for energy storage in wind farm and connected to the low voltage side of the box type transformer for the purpose of peak and valley regulation， system inertia enhancement and frequency regulation. The converter on the side of the flywheel energy storage system adopts current vector control， so that the output power of the system can be flexibly adjusted. The grid-side converter adopts a voltage directional vector control strategy to ensure the stability of the DC bus voltage. In order to verify the operation reliability of the system， Mat lab/Simulink is used to build a simulation model for testing. The results show that the energy storage system is simple to operate， efficient and convenient for installation and construction； a rotation speed modular is designed based on the operation mechanism of flywheel energy storage so that the system can operate within safety domain efficiently； control schemes of current and voltage vector on the system side and grid side are formulated respectively so that the output power can be smooth and the voltage stable.

The intermittence and randomness of wind speed leads to the fluctuation of wind turbine output power. In order to study the applicability of battery, super capacitor and flywheel energy storage technology in suppressing wind power fluctuation, this paper takes a 3 MW direct drive wind turbine as an example, and, through the establishment of a wind storage system model, the dynamic response characteristics and application effects of the three typical energy storage technologies to suppress the power fluctuation of the wind turbine under two wind speed fluctuation scenarios are simulated and studied, and the stability of output power is quantitatively analyzed. Results show that all the three energy storage systems respond well to power command curves, but when the wind power fluctuation is large, the flywheel energy storage has a better effect on suppressing the wind power fluctuation, which can suppress about 70% of the power fluctuation. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Energy storage flywheel systems are mechanical devices that typically utilize an electrical machine (motor/generator unit) to convert electrical energy in mechanical energy and vice versa. Energy is stored in a fast-rotating mass known as the flywheel rotor. The rotor is subject to high centripetal forces requiring careful design, analysis, and fabrication to ensure the safe operation of the storage device.

Increased renewable energy penetration in isolated power systems has a clear impact on the quality of system frequency. The flywheel energy storage system (FESS) is a mature technology with a fast frequency response, high power density, high round-trip efficiency, low maintenance, no depth of discharge effects, and resilience to withstand continuous charge-discharge cycling without lifetime degradation. These FESS properties allows to effectively address the frequency quality problem. This study analyzes the contribution of a FESS to reducing frequency deviations in an isolated system that combines a diesel plant, wind farm, and pump-storage hydropower plant based on the El Hierro power system. This study approaches this analysis by comparing six different FESS governor control schemes (GCSs). Of these six GCSs, the nonlinear proportional variant (NLP $_{\mathrm {V}}$ ) is a singular contribution based on the NLP scheme previously developed by the same researchers. Different governor’s parameter settings for the FESS GCSs were also compared, obtained from the proposed tuning methodology that considers the renewable energy generation distribution, frequency impact, and lifetime degradation of diesel, hydraulic groups, and flywheels. The GCSs were compared in terms of average frequency deviation, Zenith and Nadir frequency difference, wear and tear of diesel electromechanical elements and Pelton turbine nozzles, flywheels cycles per hour, and FESS average state of charge. The results show that including a FESS plant considerably improves frequency regulation. The tuning criteria and GCSs have a clear influence on the results, with NLP and NLPV GCSs offering relevant improvements in frequency deviations.

This paper presents research conducted on the development of an innovative system to increase the amount of energy recovered from a high-speed kinetic energy storage based on a three-phase permanent magnet brushless (PM BLDC) motor/generator (mogen) with a flywheel-shaped rotor, compared to the efficiency obtained for standard solutions with power electronics systems. This kinetic energy storage is currently under development. In the system presented in the paper, the regulated DC output voltage of the 6T thyristor bridge is controlled with a tolerance within ±10% of the reference voltage for a variable power load. The input voltage of the rectifier is a three-phase trapezoidal-shaped voltage from the rotating mogen, whose amplitude can vary from 0 to 650 V and frequency from 0 to 250 Hz voltage. The article presents example results of simulation tests of the mogen-based kinetic energy storage model with the thyristors' firing angle control system. As part of the research, a prototype of the rectifier was built on a laboratory scale, to confirm the validity of the assumptions regarding the synchronization and control method of the bridge using a new design of the thyristor gate drivers. [ABSTRACT FROM AUTHOR]

A Wind Diesel Hybrid System (WDHS) is an isolated power system that combines Diesel Generators (DGs) and Wind Turbines (WTGs). The WDHS has three operation modes: Diesel Only (DO), Wind Diesel (WD) and Wind Only (WO). The latter mode is the only one resulting in substantial savings, as the DG consumes fuel even with no load. Moreover, adding an energy storage system (ESS) can significantly reduce the start/stop cycles in the DG. The FESS is robust, immune to deep discharges and its state of charge (SOC) is simple to monitor. The WDHS considered in this article uses a friction clutch to disengage the diesel engine (DE) from the synchronous generator (SG) in WO mode. The AVR regulates the voltage amplitude and the frequency regulation results from balancing the power produced by the DG and WT with the power consumed by the load and dump load along with the FESS utilisation. The control algorithms of the different elements present in the WHDS are explained, as well as the general control. The FESS always has priority over the DL for the maximum harnessing of the wind power. Simulations assess the proposed solutions for the different operation modes in the WDHS. [ABSTRACT FROM AUTHOR]

In this paper, a new superconducting flywheel energy storage system is proposed, whose concept is different from other systems. The superconducting flywheel energy storage system is composed of a radial-type superconducting magnetic bearing (SMB), an induction motor, and some positioning actuators. The SMB is composed of a superconducting stator and a flywheel rotor. The flywheel rotor is suspended by the superconducting stator, whose one end is fixed to a stable and heavy base. Free-run experiments in the case of the unfixed stator are performed. The natural rotation decay curve, displacement at the upper position of the rotor and displacement at a lower position of the rotor are measured. Moreover, free-run experiments in the case of the fixed stator are performed, and the same dynamic characteristics of the unfixed stator are measured. Especially, impulse responses for the rotor in the case of an unfixed stator are very different from those in the case of a fixed stator. The experimental results discuss some important characteristics of the superconducting flywheel energy storage system, whose rotor is suspended by the superconducting stator. [ABSTRACT FROM AUTHOR]

Copyright of Zhejiang Electric Power is the property of Zhejiang Electric Power Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Southern Energy Construction is the property of Southern Energy Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the increasing pressure on energy and the environment, vehicle brake energy recovery technology is increasingly focused on reducing energy consumption effectively. Based on the magnetization effect of permanent magnets, this paper presents a novel type of magnetic coupling flywheel energy storage device by combining flywheel energy storage with magnetic coupling technology. As a high-efficiency energy storage device, it has the advantages of low energy consumption, low vibration, low noise and easy maintenance. In this paper, firstly, the structural characteristics and working process of vehicle brake energy recovery systems are analyzed, and experiments regarding the transmission and efficiency performance are carried out for key components; then a reasonable control strategy is formulated according to the principle of energy recovery; finally, the speed, acceleration, recovery energy and other parameters are analyzed based on the New European Driving Cycle (NEDC) working conditions. The results show that the energy recovery efficiency reaches 35.59%, which verifies the usability of the device.

Definition: Energy storage flywheel systems are mechanical devices that typically utilize an electrical machine (motor/generator unit) to convert electrical energy in mechanical energy and vice versa. Energy is stored in a fast-rotating mass known as the flywheel rotor. The rotor is subject to high centripetal forces requiring careful design, analysis, and fabrication to ensure the safe operation of the storage device. [ABSTRACT FROM AUTHOR]

Flywheel energy storage has a wide range of applications in energy grids and transportation. The adoption of high-performance components has made this technology a viable alternative for substituting or complementing other storage devices. Flywheel energy storage systems are subject to passive discharge attributed primarily to electrical machine losses, bearing rolling friction, and aerodynamic drag of the flywheel rotor. In the present study, measurements are presented for complete discharge experiments using a flywheel system featuring a vacuum enclosure. Best-fit equations were applied to the test data and compared to analytical models. Analysis of the best-fit equations indicates that they may serve as empirical models for approximating passive discharge under given conditions. Bearing losses, which varied linearly with velocity but were otherwise unaffected throughout the experiments, were larger than aerodynamic drag at low air pressures and low velocities. Aerodynamic drag became significant as velocity exceeded approximately 3400 rpm. The electrical machine was found to be the most significant source of passive discharge at all velocities and pressures. Based on these findings, it is recommended to maintain a low-pressure environment in the flywheel enclosure and to decouple the electrical machine from the rotor whenever possible to eliminate associated losses.

Flywheel energy storage systems (FESS) are devices that are used in short duration grid-scale energy storage applications such as frequency regulation and fault protection. The energy storage component of the FESS is a flywheel rotor, which can store mechanical energy as the inertia of a rotating disk. This article explores the interdependence of key rotor design parameters, i.e., shape, operating speed, rotor radius, standby losses, and choice of material, and their influence on the energy storage characteristics of the FESS. Two commercially manufactured metal flywheels with distinct energy storage characteristics are used as case studies to examine the potential benefit of using shape optimization in combination with operating speed, size, and material selection for rotor design. A sequential hybrid optimization strategy that combines a global genetic algorithm with a gradient-based local method is used to solve the rotor shape optimization problem. The choice of an optimal combination of operating speed and rotor radius, together with shape optimization, is demonstrated to provide 21–46% improvements in the energy capacity of two existing commercial FESS designs. Results show that self discharge losses in the rotor can be reduced by designing optimally shaped rotors with large radii operating at low speeds. It is advantageous, on an "energy-per-cost of material" basis, to use steel as the rotor material for optimally shaped flywheels with large radii operated at low speeds. Conversely, aluminium is a better choice of material for flywheels with smaller radii operated at high speeds. [ABSTRACT FROM AUTHOR]

This paper presents research conducted on the development of an innovative system to increase the amount of energy recovered from a high-speed kinetic energy storage based on a three-phase permanent magnet brushless (PM BLDC) motor/generator (mogen) with a flywheel-shaped rotor, compared to the efficiency obtained for standard solutions with power electronics systems. This kinetic energy storage is currently under development. In the system presented in the paper, the regulated DC output voltage of the 6T thyristor bridge is controlled with a tolerance within ±10% of the reference voltage for a variable power load. The input voltage of the rectifier is a three-phase trapezoidal-shaped voltage from the rotating mogen, whose amplitude can vary from 0 to 650 V and frequency from 0 to 250 Hz voltage. The article presents example results of simulation tests of the mogen-based kinetic energy storage model with the thyristors’ firing angle control system. As part of the research, a prototype of the rectifier was built on a laboratory scale, to confirm the validity of the assumptions regarding the synchronization and control method of the bridge using a new design of the thyristor gate drivers.

A Wind Diesel Hybrid System (WDHS) is an isolated power system that combines Diesel Generators (DGs) and Wind Turbines (WTGs). The WDHS has three operation modes: Diesel Only (DO), Wind Diesel (WD) and Wind Only (WO). The latter mode is the only one resulting in substantial savings, as the DG consumes fuel even with no load. Moreover, adding an energy storage system (ESS) can significantly reduce the start/stop cycles in the DG. The FESS is robust, immune to deep discharges and its state of charge (SOC) is simple to monitor. The WDHS considered in this article uses a friction clutch to disengage the diesel engine (DE) from the synchronous generator (SG) in WO mode. The AVR regulates the voltage amplitude and the frequency regulation results from balancing the power produced by the DG and WT with the power consumed by the load and dump load along with the FESS utilisation. The control algorithms of the different elements present in the WHDS are explained, as well as the general control. The FESS always has priority over the DL for the maximum harnessing of the wind power. Simulations assess the proposed solutions for the different operation modes in the WDHS.

A novel dual-rotor induction motor (DRIM) is proposed as a potential substitution of the traditional motor/generator with a flywheel (MGFW) used in the pulsed power driving system (PPDS) which is especially deployed in mobile platforms. The DRIM is based on the integration of flywheel energy storage and electromagnetic slip coupling mechanism. The DRIM utilizes its outer rotor as a flywheel to store the input mechanical energy. By the interaction between the excitation field produced by the outer rotor and the eddy current induced on the surface of the inner rotor, an electromagnetic torque is generated and simultaneously acted on the two rotors. So the stored energy in the outer rotor can be directly transferred to the inner rotor with the mechanical load through the torque. The substitution of MGFW with DRIM holds potential for simplifying the PPDS and improving its compactness. The configuration and operation mechanism of the DRIM are firstly introduced in this paper. Then transient characteristics of the DRIM are analyzed by the 2D finite element method (FEM). The influences of the excitation pole number and the excitation coil turns on the performance of the DRIM are investigated. Finally, the feasibility of the DRIM is experimentally verified by a prototype.

In this paper, a new superconducting flywheel energy storage system is proposed, whose concept is different from other systems. The superconducting flywheel energy storage system is composed of a radial-type superconducting magnetic bearing (SMB), an induction motor, and some positioning actuators. The SMB is composed of a superconducting stator and a flywheel rotor. The flywheel rotor is suspended by the superconducting stator, whose one end is fixed to a stable and heavy base. Free-run experiments in the case of the unfixed stator are performed. The natural rotation decay curve, displacement at the upper position of the rotor and displacement at a lower position of the rotor are measured. Moreover, free-run experiments in the case of the fixed stator are performed, and the same dynamic characteristics of the unfixed stator are measured. Especially, impulse responses for the rotor in the case of an unfixed stator are very different from those in the case of a fixed stator. The experimental results discuss some important characteristics of the superconducting flywheel energy storage system, whose rotor is suspended by the superconducting stator.

It will lead to the problem of frequency adjustment when the large-scale new energy integrated in the power grid, and large capacity power energy storage is one of the effective solutions for the problem. By analyzing the types of power energy storage and its application scenarios, this paper points out that there are four large capacity energy storage technologies such as electrochemical energy storage, pumped storage, flywheel energy storage and compressed air energy storage which play a role in the power grid frequency adjustment, introduces the performance feature of the four large capacity power energy storage, and summarizes the properties which participate in grid load adjustment, primary frequency modulation, secondary frequency regulation. The characteristic of peak frequency modulation are compared, and the development tendency of research in the future is pointed out.