Kinetic Energy Storage System Research Articles

Optoelectronic Strain-Measurement System Demonstrated on Scaled-Down Flywheels.

Monitoring the strain in the rotating flywheel in a kinetic energy storage system is important for safe operation and for the investigation of long-term effects in composite materials like carbon-fiber-reinforced plastics. An optoelectronic strain-measurement system for contactless deformation and position monitoring of a flywheel was investigated. The system consists of multiple optical sensors measuring the local relative in-plane displacement of the flywheel rotor. A special reflective pattern, which is necessary to interact with the sensors, was applied to the surface of the rotor. Combining the measurements from multiple sensors makes it possible to distinguish between the deformation and in-plane displacement of the flywheel. The sensor system was evaluated using a low-speed steel rotor for single-sensor performance investigation as well as a scaled-down high-speed rotor made from PVC plastic. The PVC rotor exhibits more deformation due to centrifugal stresses than a steel or aluminum rotor of the same dimensions, which allows experimental measurements at a smaller flywheel scale as well as a lower rotation speed. Deformation measurements were compared to expected deformation from calculations. The influence of sensor distance was investigated. Deformation and position measurements as well as derived imbalance measurements were demonstrated.

A Battery-Free Sustainable Powertrain Solution for Hydrogen Fuel Cell City Transit Bus Application

The paper presents a sustainable electric powertrain for a transit city bus featuring an electrochemical battery-free power unit consisting of a hydrogen fuel cell stack and a kinetic energy storage system based on high-speed flywheels. A rare-earth free high-efficiency motor technology is adopted to pursue a more sustainable vehicle architecture by limiting the use of critical raw materials. A suitable dynamic energetic model of the full vehicle powertrain has been developed to investigate the feasibility of the traction system and the related energy management control strategy. The model includes losses characterisation, as a function of the load, of the main components of the powertrain by using experimental tests and literature data. The performance of the proposed solution is evaluated by simulating a vehicle mission on an urban path in real traffic conditions. Considerations about the effectiveness of the traction system are discussed.

Design and Modeling of an Integrated Flywheel Magnetic Suspension for Kinetic Energy Storage Systems

The paper presents a novel configuration of an axial hybrid magnetic bearing (AHMB) for the suspension of steel flywheels applied in power-intensive energy storage systems. The combination of a permanent magnet (PM) with excited coil enables one to reduce the power consumption, to limit the system volume, and to apply an effective control in the presence of several types of disturbances. The electromagnetic design of the AHMB parts is carried out by parametric finite element analyses with the purpose to optimize the force performances as well as the winding inductance affecting the electrical supply rating and control capability. Such investigation considers both the temperature dependence of the PM properties and the magnetic saturation effects. The electrical parameters and the force characteristics are then implemented in a control scheme, reproducing the electromechanical behavior of the AHMB-flywheel system. The parameter tuning of the controllers is executed by a Matlab/Simulink code, examining the instantaneous profiles of both the air-gap length and the winding ampere-turns. The results of different dynamic tests are presented, evidencing the smooth air-gap changes and the optimized coil utilization, which are desirable features for a safe and efficient flywheel energy storage.

Preliminary design of an alternative energy storage system for a city car based on flywheel

Vehicle energy storage systems have a crucial impact on the spreading of hybrid and electric vehicles. Nowadays the most adopted solution is represented by batteries which suffer of ageing that reduces the battery capacity; moreover, the battery recycling at the end of its life is still a challenge and generate pollution. This paper presents a preliminary design of a kinetic energy storage system for city micro-car. The energy is stored by means of flywheel. First, an energetic model of the car powertrain including flywheel and bearings is proposed and used to evaluate the car energy requirement to accomplish its typical journey. Then, material, geometry and motor have been selected to fit all the vehicle space requirements. Then, analysis on the gyroscopic effects induced by the flywheel is shown when it is subjected to car chassis acceleration. Finally, preliminary considerations on bearing layout are drawn by comparing different bearings types.

Preliminary design of an alternative energy storage system for a city car based on flywheel

Vehicle energy storage systems have a crucial impact on the spreading of hybrid and electric vehicles. Nowadays the most adopted solution is represented by batteries which suffer of ageing that reduces the battery capacity; moreover, the battery recycling at the end of its life is still a challenge and generate pollution. This paper presents a preliminary design of a kinetic energy storage system for city micro-car. The energy is stored by means of flywheel. First, an energetic model of the car powertrain including flywheel and bearings is proposed and used to evaluate the car energy requirement to accomplish its typical journey. Then, material, geometry and motor have been selected to fit all the vehicle space requirements. Then, analysis on the gyroscopic effects induced by the flywheel is shown when it is subjected to car chassis acceleration. Finally, preliminary considerations on bearing layout are drawn by comparing different bearings types.

Dynamic simulation of a vessel drive system with dual fuel engines and energy storage

Dredging operations result in severe load changes, and the transient capability of natural gas-fuelled dual fuel engines in gas mode is not sufficient to cope with them. An energy storage system may compensate the difference depending on the system size and control strategy. Previously developed component models are adapted and expanded with natural gas combustion and a kinetic energy storage system. The dual fuel engine’s performance and transient behaviour in gas mode is validated with data from a factory acceptance test. Both the effect of increasing the available engine power and increasing the power of the energy storage system are investigated. The simulation results show the trade-off between the transient capability and lower harmful emissions on one side, and the operational costs and system efficiency on the other side. Increasing the available engine power, enhances the drive system’s transient capability by reducing load change experienced by each engine, but it also increases the fuel energy consumption and global warming potential. A kinetic energy storage system increases the average engine load and fuel energy consumption slightly. The higher engine load results in a lower methane slip and does, therefore, not result in a net increase of the global warming potential.

Modeling, Analysis and Implementation of an Urban Electric Light-Rail Train Hydrogen Powered

A novel hydrogen power configuration of a Light Hybrid Electric (LHE) rail train able to operate along sub-urban non-electrified rail lines is proposed and analysed in the paper. The electric motors of the emission-free LHE rail train are fed by a hybrid power unit consisting of hydrogen fuel cell stacks and a set of high-speed kinetic energy storage systems. A control strategy of the power-train components has been developed to manage power flows in order to reduce the fuel consumption. This advanced and environment friendly hybrid propulsion system offers the opportunity to increase the power-train efficiency so that the fuel consumption is minimised. Simulator software of the proposed HLE rail train has been implemented in order to design the power-train components and compute train performance. A rail transport service is considered and a round trip journey of the LHE rail train is simulated over an existing re-designed not electrified single track line in the sub-urban area of L’Aquila city (Italy). Furthermore, the specific fuel consumption comparative analysis between the hydrogen rail train and a diesel one running over the selected path in the same operating conditions has been performed and the results are discussed in terms of CO2 emissions too. The results show that the proposed LHE rail train is technically suitable and advantage to operate in urban environment.

Fast Energy Storage Systems Comparison in Terms of Energy Efficiency for a Specific Application

One of the key parameters to properly and accurately assess an energy storage system is the energy efficiency, which has a direct impact on the system performance and an indirect impact in its cost. In this paper, a methodology for comparing double-layer capacitors (EDLC) and kinetic energy storage systems (KESS) in terms of energy efficiency is proposed. This methodology, based on accurate loss models, takes real operating cycles into account, so a realistic result is obtained for each particular case. An accurate study of the losses of both technologies is accomplished during the paper, getting a complete model for EDLCs and KESSs, and obtaining efficiency maps for the whole range of operation points. Some conclusions about the convenience to use one or the other alternative and the best way to operate them are presented. In addition, a specific study case related to a wave energy power generation plant has been carried out in this paper, defining a methodology to select the energy storage requirements, calculating the round-trip efficiency and getting some recommendations related to the most appropriate operation strategy to take the most advantage of the energy storage system.

Hydrogen fuel cell and kinetic energy recover systems technologies for powering urban bus with zero emission energy cycle

This study presents an analysis of a hydrogen-fuelled city bus with ‘zero’ emission solar–hydrogen cycle. The study considers an electric vehicle based on four separately powered wheels, connected to a hybrid unit composed by a hydrogen fuel cell and a high-speed kinetic energy storage system. A bus with 21 passengers carrying capacity is simulated to run along urban drive cycles with different slopes. Vehicle power-train components are designed. The balance between the energy consumption for a yearly bus travel and the energy production by means of photovoltaic panels is performed for three different Italian locations and the results are also discussed in terms of CO2 emissions.

Stability and Nonstationary Vibrations of Rotor in Elastoviscous Field

The efforts directed toward ensuring long trouble-free operation of rotating machinery are in the focus of many scientific investigations. Electric power rotors and turbines, aircraft engines, automotive drive trains, kinetic energy storage systems are only few examples of machines that are to operate efficiently and safely. Very often they are imposed on external excitations, which are characterized by time-dependent characteristics and causing nonstationary random oscillations. In this paper, the dynamics of high-speed rotating rotor is analytically and numerically analyzed. The analytical investigations studied the steady-state vibrations in the neighborhood of resonance conditions of a rotor with 6 degrees of freedom in linear homogeneous elastoviscous field. Unstable frequencies zones are determined by “limited” power of an electric motor with linear characteristic and only one time constant. The analytical solution of the differential equations is implemented applying Bogoliubov–Mitropolski's asymptotical method in neighborhood of resonances. The analytical solution verifies the numerical dynamic model derived using a general purpose program system for computer code generation of the dynamic equation and simulation of motion of multibody systems of rigid and flexible bodies. It is regarded an unbalanced rotor attached to a flexible shaft and operating in elastoviscous field. Examples of the rotor in elastoviscous field with clearances in the bearings are presented.

High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings

This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.

Electric energy storages - a method for specification, design and assessment

The energy transition towards a significantly increased use of renewable energies is confronted with numerous challenges. These include the development of efficient energy storage systems, which need to address the specific requirements of the application area. The present paper contributes to this debate with the specification, design and assessment-method (SDA-method). Based on a statistical analysis of the applications load profile, the specifications for the energy storage system are defined and the design process is conducted. This is demonstrated using the example of a kinetic energy storage system. The following assessment considers the energetic behaviour, life cycle costs as well as environmental impacts. In order to fully exploit the comprehensive methodology, in-depth information is required. This relates firstly to the economical use of storages. Secondly, the multidimensional assessment is subject to many uncertainties. Our methodology reveals existing information gaps and helps to identify future research objectives.

Analysis and Experiment of Energy Storage to 2-Axis Spinning Sphere

Concept of kinetic energy storage system with 2-axis spinning sphere is described to improve energy density of mechanical battery, i.e., flywheel energy storage system. Fundamental analysis with finite element method and the first experiment of 2-axis spinning sphere are carried out to clarify the proposed concept. Analytical and experimental results verify that the 2-axis spin makes it possible to storage kinetic energy by a factor of 2 over the conventional 1-axis rotation for the same rotation speed. However, it is shown that the mechanical losses of the prototype system with a geared-type 2-axis spin mechanism is approximately twice as large as the 1-axis rotation sphere. Exploring a novel 2-axis spin mechanism with the least mechanical losses is a critical issue to realize the concept.

Superconductor and magnet levitation devices

This article reviews levitation devices using superconductors and magnets. Device concepts and their applications such as noncontact bearings, flywheels, and momentum wheels are discussed, following an exposition of the principles behind these devices. The basic magneto–mechanical phenomenon responsible for levitation in these devices is a result of flux pinning inherent in the interaction between a magnet and a type II superconductor, described and explained in this article by comparison with behavior expected of a perfect conductor or a nearly perfect conductor. The perfect conductor model is used to illustrate why there is a difference between the forces observed when the superconductor is cooled after or before the magnet is brought into position. The same model also establishes the principle that a resisting force or torque arises only in response to those motions of the magnet that changes the magnet field at the superconductor. A corollary of the converse, that no drag torque appears when an axisymmetric magnet levitated above a superconductor rotates, is the guiding concept in the design of superconductor magnet levitation bearings, which is the common component in a majority of levitation devices. The perfect conductor model is extended to a nearly perfect conductor to provide a qualitative understanding of the dissipative aspects such as creep and hysteresis in the interaction between magnets and superconductors. What all these entail in terms of forces, torques, and power loss is expounded further in the context of generic cases of a cylindrical permanent magnet levitated above a superconductor and a superconductor rotating in a transverse magnetic field. Then we proceed to compare the pros and cons of levitation bearings based on the first arrangement with conventional mechanical bearings and active magnetic bearings, and discuss how the weak points of the levitation bearing may be partially overcome. In the latter half, we examine designs of devices using superconductor magnet levitation, focusing more on issues specific to the application. We note that applications of superconductor magnet levitation devices tend to be most attractive in situations where energy conservation is critical. The most advanced in development are flywheel kinetic energy storage systems incorporating superconductor magnet bearings. Variations in the designs to enhance the performance in some specific regards are examined case by case. Next we present a reaction wheel for attitude control on small satellites, similar in overall design to the flywheel kinetic energy storage systems, but with subtle differences in details of emphasis, due to the difference in purpose and environment. Finally, we take a brief look at the case of vibration isolation devices as an example of a rectilinear modification of the more familiar rotational bearing applications.

A new move in energy recapture

The author explains how Urenco Power Technologies' kinetic energy storage system (UPT KESS) helps to smooth power fluctuations and maintain voltage levels in applications such as wind farms, uninterruptible power supplies, mining, heavy lifting gear and mass transit. At the heart of the system is a patented high-speed composite flywheel, which takes advantage of the basic physical laws whereby kinetic energy is proportional to the square of the speed. The modular KESS stores 14 MJ of energy, of which up to 11 MJ can be usefully used, depending upon the application.

Engineering prototype of a superconducting flywheel for long term energy storage

We built a flywheel system with superconducting magnetic bearings. The bearing consists of six melt-textured YBCO pellets mounted inside a continuous flow LN/sub 2/ cryostat. A disk measuring /spl phi/ 190 mm/spl times/30 mm was safely rotated at speeds up to 15000 rpm. The disk was driven by a high speed three phase synchronous homopolar motor/generator. Maximum energy capacity was 4.8 Wh, maximum power was 1.5 kW. The dynamic behavior of the prototype was tested, characterized and evaluated with respect to axial and lateral stiffness, damping, decay torques (bearing drag), vibrational modes and critical speeds. Experimental data were found to be in agreement with a structural damping model. Rotor unbalance together with the hysteretic nature of the superconducting magnetic bearing gave a significant contribution to the overall losses. At a background pressure of 6/spl times/10/sup -4/ mbar, the coefficient of friction (drag-to-lift ratio) was measured to be /spl mu/=9/spl times/10/sup -6/. The experiments demonstrate the applicability of superconducting magnetic bearings in highly efficient, kinetic energy storage systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>