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[This corrects the article DOI: 10.1371/journal.pone.0211700.].

The operation of the electricity network has grown more complex due to the increased adoption of renewable energy resources, such as wind and solar power. Using energy storage technology can improve the stability and quality of the power grid. One such technology is flywheel energy storage systems (FESSs). Compared with other energy storage systems, FESSs offer numerous advantages, including a long lifespan, exceptional efficiency, high power density, and minimal environmental impact. This article comprehensively reviews the key components of FESSs, including flywheel rotors, motor types, bearing support technologies, and power electronic converter technologies. It also presents the diverse applications of FESSs in different scenarios. The progress of state-of-the-art research is discussed, emphasizing the use of artificial intelligence methods such as machine learning, digital twins, and data-driven techniques for system simulation, fault prediction, and life-assessment research. The article also addresses the challenges related to current research and the application of FESSs. It concludes by summarizing future directions and trends in FESS research, offering valuable information for further advancement and improvement in this field.

An investigation on a flywheel is presented based on finite element modelling simulations for different geometries. The goal was to optimise the energy density (rotational energy-to-mass ratio) and, at the same time, the rotational energy of a flywheel rotor. The stress behaviour of flywheel rotors under the rotational speed at the maximum stress achievable by the flywheel was analysed. Under this condition, the energy density was obtained for the different geometries, as well as the rotational energy. The best energy density performance due to geometry was achieved with a flywheel rotor presenting a new Gaussian section, which is different from the known Laval disk shape. The best results using a single disk involved a rotational speed of nearly 279,000 rpm and a rotational energy density around 1584 kJ/kg (440 Wh/kg). These values still yielded low total energy; to increase its value, two or three rotors were added to the flywheel, which were analysed in regard to stability. In particular, the triple rotor energy density was ≈ 1550 kJ/kg (431 Wh/kg). As some instability was found in these rotors, a solution using reinforcement was developed to avoid such instabilities. The energy density of such a reinforced double rotor neared 1451 kJ/kg (403 Wh/kg), and the system achieved higher total energy. The material assumed for the devices was carbon fibre Hexcel UHM 12,000, a material kept constant throughout the simulations to allow comparison among the different geometries.

In response to the problems of strong specificity, poor universality, and high maintenance difficulty of existing flywheel control software, this paper develops a generalized flywheel control and testing software. By analyzing the problems in the universality, automation, parallelism, and reusability of existing equipment, and adopting the modular design concept, the design is carried out in the mode of hardware generalization to meet the control and testing requirements of various types of flywheel products, improve the universality and testing efficiency of the control software, and verify the accuracy and stability of the control software through experiments.

Energy storage systems are essential in modern energy infrastructure, addressing efficiency, power quality, and reliability challenges in DC/AC power systems. Recognized for their indispensable role in ensuring grid stability and seamless integration with renewable energy sources. These storage systems prove crucial for aircraft, shipboard systems, and electric vehicles, addressing peak load demands economically while enhancing overall system reliability and efficiency. Recent advancements and research have focused on high-power storage technologies, including supercapacitors, superconducting magnetic energy storage, and flywheels, characterized by high-power density and rapid response, ideally suited for applications requiring rapid charging and discharging. Hybrid energy storage systems and multiple energy storage devices represent enhanced flexibility and resilience, making them increasingly attractive for diverse applications, including critical loads. This paper provides a comprehensive overview of recent technological advancements in high-power storage devices, including lithium-ion batteries, recognized for their high energy density. In addition, a summary of hybrid energy storage system applications in microgrids and scenarios involving critical and pulse loads is provided. The research further discusses power, energy, cost, life, and performance technologies.

The energy storage industry has expanded globally as costs continue to fall and opportunities in consumer, transportation, and grid applications are defined. As the rapid evolution of the industry continues, it has become increasingly important to understand how varying technologies compare in terms of cost and performance. This paper defines and evaluates cost and performance parameters of six battery energy storage technologies (BESS)—lithium-ion batteries, lead-acid batteries, redox flow batteries, sodium-sulfur batteries, sodium-metal halide batteries, and zinc-hybrid cathode batteries—four non-BESS storage systems—pumped storage hydropower, flywheels, compressed air energy storage, and ultracapacitors—and combustion turbines. Cost and performance information was compiled based on an extensive literature review, conversations with vendors and stakeholders, and costs of systems procured at sites across the United States. Detailed cost and performance estimates are presented for 2018 and projected out to 2025. Annualized costs were also calculated for each technology.

This study investigates the effectiveness of a hydraulic-pneumatic flywheel system integrated into the rotor of a wind turbine for structural load reduction. The analysis uses the state-of-the-art aeroelastic simulation tools OpenFAST and HAWC2, coupled with a novel Simulink based flywheel and control model, to evaluate fatigue loads mitigation abilities of the flywheel. Fatigue load simulations are performed for cases with and without the flywheel system, with a specific focus on the fatigue life of the tower. The findings indicate that different flywheel control functionalities exhibit varying levels of influence on tower fatigue loading in both simulation environments. A fatigue-life extension of up to 20% is achieved, demonstrating the potential of flywheel control strategies for structural load mitigation.

Flywheels are devices that preserve and release kinetic energy, which makes them one of the newest energy storage technologies. They may produce large amounts of electricity at high rotational speeds. Increasing the capacity of compared to traditional battery-powered technologies, flywheels may provide high power during transfer times and endure longer. Three primary variables impact the flywheel’s performance: spinning speed, material strength and cross-sectional shape. The main objective of this study is to examine how flywheel geometry alters the energy storage and delivery capabilities per unit mass, also known as specific energy, even though the strength of the materials directly determines the kinetic energy level that can be safely generated when coupled with rotor speed. The current document would be talking about the design of Flywheel and types of analysis being performed on the Flywheel by using ANSYS software. Material which yields best results for the applied loads and forces acting on it.

Energy storage systems play a crucial role in the overall performance of hybrid electric vehicles. Therefore, the state of the art in energy storage systems for hybrid electric vehicles is discussed in this paper along with appropriate background information for facilitating future research in this domain. Specifically, we compare key parameters such as cost, power density, energy density, cycle life, and response time for various energy storage systems. For energy storage systems employing ultra capacitors, we present characteristics such as cell voltage, cycle life, power density, and energy density. Furthermore, we discuss and evaluate the interconnection topologies for existing energy storage systems. We also discuss the hybrid battery–flywheel energy storage system as well as the mathematical modeling of the battery–ultracapacitor energy storage system. Toward the end, we discuss energy efficient powertrain for hybrid electric vehicles.

A study on flywheels materials and geometries is presented here with the use of finite element modeling (FEM) simulations. The study analyzes the stress behavior of flywheel rotors subject to the rotational speed that creates the maximum stress that the flywheel can support, and then calculates the rotational energy mass ratio for each geometry. The obtained geometry was Gaussian section for the Flywheel rotor. The material used in this case study is carbon fiber Hexcel UHM 12000. The best results were a rotational speed of ≈ 279.000 rpm and rotational energy density of ≈ 440 Wh/kg. Then, to increase the total energy, Flywheel with 2 and 3 rotors were analyzed. Then the stability under rotation of these Flywheels were analyzed, some instability was found and a solution was presented.