Energy Storage Coil Research Articles

Influence of Structure Parameters of Flux Diverters on Performance of Superconducting Energy Storage Coil

Influence of Structure Parameters of Flux Diverters on Performance of Superconducting Energy Storage Coil

Demonstration of 10 KJ-Capacity Energy Storage Coil Made of MgB2 With Liquid Hydrogen Indirect Cooling

10 kJ-Capacity Energy Storage Coil Made of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> proposed in the Advanced Superconducting Power Conditioning System (ASPCS) was fabricated, and an electric current test was conducted with indirect liquid hydrogen cooling. This coil consists of three DP (double pancake) coils with an inner diameter of 400 mm and an outer diameter of 606 mm. The first DP was manufactured by the W&R (Wind and Reacted), and second and third DPs were manufactured by the R&W (React and Wind). A thermosiphon system is used for cooling the coils, in which the coolant is circulate without pump. For energization, several DC excitation and AC excitation tests were carried out with liquid hydrogen, and the rated current of 600 A was successfully achieved. The evaluation of both DC and AC losses were also performed, indicating needs to reduce the losses for stable operation under the indirect cooling conditions.

Demonstration and thermal equilibrium analysis of a 10 kJ capacity energy storage coil made of MgB2 with liquid hydrogen indirect cooling

We have demonstrated an advanced superconducting power conditioning system, in which a superconducting magnetic energy storage (SMES) device, a generator based on a fuel cell (FC), and an electrolyzer are used to compensate for electricity fluctuations over a wide frequency range, combined with a liquid hydrogen storage system to both cool the SMES and provide pure hydrogen gas to the FC and other gas-dependent systems. To manufacture the coils for the SMES, we used MgB2, whose critical temperature is below the boiling temperature of hydrogen. We developed a 10 kJ SMES coil system indirectly cooled by liquid hydrogen using thermosyphon passive heat exchange to isolate the flammable hydrogen from the electrical components. We performed a successful demonstration of this system for both DC and AC currents ramped at different rates. In the present study, we use computer simulations involving heat balance equations to evaluate the stability of the system. The results obtained are expected to lead to the design of future large-capacity energy storage systems, such as the MJ class, which offer comparable performance to conventional NbTi SMES devices.

AC Loss Measurement of Double Pancakes Wound With MgB2 Rutherford Type Superconductor

Double pancakes (DPs) for a Superconducting Magnetic Energy Storage (SMES) coil have been developed using MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Rutherford type superconductors. The DPs with 400 mm ID and about 600 mm OD were wound with Rutherford type conductors cabled by twisting multi-filamentary MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> strands. For use in an indirect cooling system, the DPs and thin pure copper sheets as thermal conductors were alternately stacked, and the SMES coil was assembled. In the experiment, while continuous triangular current waveforms up to 600 A and DC current were supplied to two configurations of the SEMS coil, the AC loss at 4.2 K was measured by calorimetric method. By comparing the losses under each excitation and configuration, the AC loss in the SMES coil and an eddy current loss in the copper sheets were obtained, separately. The resultant AC loss in the SMES coil was in agreement with the theoretical values.

Method to Improve the Optimized Calculation Speed of Superconducting Magnetic Coil

This paper proposes a method for saving the optimized calculating time and maximizing the energy storage density of the superconducting magnet coil. The size of the coil is taken as the optimal objective. The genetic algorithm (GA) and the traditional particle swarm optimization (PSO) are analyzed to compare with the proposed PSO. Simulation results show that the improved PSO has faster convergence rate than the GA and stronger astringency than the traditional PSO. The proposed method is used to optimize the size of the superconducting energy storage coil on the premise that the total volume remains unchanged. Experimental results verify the effectiveness of the optimization method.

Analysis on the Effect of Magnetic Energy Storage on the Stability Parameters of a Wind Generator Connected System

The usage of superconducting storage medium for the improvement of system stability is studied in this paper. A Superconducting Magnetic Energy Storage coil (SMES) is used along with the wind energy connected system. The grid connectivity is maintained with the help of converter unit, controlled using fuzzy logic. The system model is simulated on MATLAB/SIMULINK environment and the variations of parameters of the generators are studied.

The MEST, a new magnetic energy storage and transfer system: Application studies to the European DEMO

Abstract A new Magnetic Energy Storage and Transfer (MEST) system, which can improve the power handling in fusion experiments, has been recently conceived. It is particularly suitable to feed the DEMO Central Solenoid (CS), in principle without the need for resistive switching networks (SNUs), but can be applied to supply the Poloidal Field (PF) coils too. The operating principle of this system, described for one central solenoid circuit, is to pre-charge an additional Superconducting Magnetic Energy Storage (SMES) coil at least up to twice the maximum energy expected in the load (CS) and to transfer the energy from one to the other and viceversa via switched-capacitor. With this approach, the energy is exchanged between the load and the storage system, thus flattening the active power profile to be required from the ac side and substantially nullify the reactive power absorbed. In this paper, the application of this concept to the European DEMO is studied, starting from the present circuit configuration and from the current and voltage scenario under consideration for the plasma breakdown and ramp-up. A first tentative rating of the system components is reported, discussing also the future R&D steps to explore the industrial feasibility of such a scheme.

World markets for lithium compounds, 2020-2025

A new Magnetic Energy Storage and Transfer (MEST) system, which can improve the power handling in fusion experiments, has been recently conceived. It is particularly suitable to feed the DEMO Central Solenoid (CS), in principle without the need for resistive switching networks (SNUs), but can be applied to supply the Poloidal Field (PF) coils too. The operating principle of this system, described for one central solenoid circuit, is to pre-charge an additional Superconducting Magnetic Energy Storage (SMES) coil at least up to twice the maximum energy expected in the load (CS) and to transfer the energy from one to the other and viceversa via switched-capacitor. With this approach, the energy is exchanged between the load and the storage system, thus flattening the active power profile to be required from the ac side and substantially nullify the reactive power absorbed.In this paper, the application of this concept to the European DEMO is studied, starting from the present circuit configuration and from the current and voltage scenario under consideration for the plasma breakdown and ramp-up. A first tentative rating of the system components is reported, discussing also the future R&D steps to explore the industrial feasibility of such a scheme.

Study on Conceptual Designs of Superconducting Coil for Energy Storage in SMES

Superconducting Magnetic Energy Storage (SMES) is an exceedingly promising energy storage device for its cycle efficiency and fast response. Though the ubiquitous utilization of SMES device is restricted because of the immense cost of cryogenic refrigeration system to sustain the superconducting state but with the continuous evolution of high Tc superconductors, SMES is turning into a major contender to the existing energy storage devices in the future. Among its several parts, the superconducting coil is considered to be the most crucial segment of this technology and the inductance generated in the coil determines the quantity of stored energy. In this paper, the possible geometrical configurations of SMES coil have been demonstrated. High Tc superconducting tapes are usually employed to form these configurations worldwide. BSCCO (Bismuth strontium calcium copper oxide)-2223 tape superconductor has been considered for studying the conceptual designs of superconducting coil of SMES. Before estimating the results, the value of critical current at different magnetic field densities and temperatures have been addressed through the study of superconducting tape characterization. Numerical results and the relationship among the several parameters for both the solenoid and toroid configurations in different specifications have been presented. Based on the results, the size ratio in solenoid and the mean toroid diameter in toroid arrangement is found to play the vigorous roles in the generation of inductance and hence the energy storage. The results also match the propensity of other studies. Suggestions for maximum energy gain from a specific solenoid configuration have been provided. Future research scopes with alternative superconducting tapes and limitations of this study have been briefly conferred.

MEST: A new Magnetic Energy Storage and Transfer system for improving the power handling in fusion experiments

A new magnetic energy storage scheme is studied for improving the power handling in fusion experiments: it can be applied both to tokamak or RFP experiments to supply the poloidal superconducting coils and can efficiently support the operation of the Central Solenoid (CS), without the need for resistive switching networks, thus with the advantage of energy dissipation avoidance. The basic idea, presented with reference to the CS circuit, is to provide an additional Superconducting Magnetic Energy Storage coil (TC), pre-charged along with the CS one to the same current value and then to transfer step by step the energy from one to the other and vice versa during the different phases of the plasma pulse, via switched capacitor. The principle is applied to the case of a Fusion-Fission Hybrid Reactor, based on Reversed Field Pinch configuration operated exploiting the flux double swing.

A Method to Improve Volume Energy Density for HTS Coil

This paper investigates strategies to improve the volume energy density of superconducting solenoidal energy storage coil. A multiple population genetic optimization algorithm combined with MATLAB and COMSOL is used to optimize the structural parameters of the solenoid coil with rectangular cross section. The maximal radial magnetic flux densities, critical currents, volume energy densities, and tapes utilizing rates of rectangular and other three different step-shaped cross-sectional solenoidal coils are analyzed and compared. The coil with inner and outer step-shaped cross section is proposed as the topology to improve the volume energy density. The current injection strategy that different step coils are supplied with different currents according to the magnetic flux density distribution is employed to further improve the volume energy density.

Development of design for large scale conductors and coils using MgB2 for superconducting magnetic energy storage device

MgB2 wires are commercially available, and their superconducting characteristics have been continuously developed in the last decade. The relatively high critical temperature of these wires has attracted the attention of researchers, especially in the field of superconducting magnetic energy storage (SMES) coil applications in terms of its relatively high critical temperature, as it enables the use of liquid hydrogen for cooling the coils. The sensitivity of multi-filament MgB2 wires to bending strain makes the design of large-scale conductors and coils for an SMES system technologically difficult, and the careful investigation of the applied strains during manufacturing is required. Two-conventional methods have been introduced for the fabrication of the coils: wind-and-react (W&R) and react-and-wind (R&W). These methods have been demonstrated to be suitable for the production of large-scale MgB2 magnets to maximize the coil performance. The W&R and R&W methods have been successfully applied to the designs of conductors and coils, and small W&R test coil fabrication, as well as stability demonstrations are performed in this study. Our study is the first to demonstrate the feeding of hundreds of amperes of transport current using multifilamentary MgB2 wires at around liquid hydrogen temperature in the practical background magnetic field of 2 T. The minimum quench energy and normal zone propagation velocity are also experimentally investigated for the protection of the actual coils for SMES application.

Design and Demonstration of a Double-pancake Coil for SMES using MgB2 Multi-strand cable

MgB2 round wires are now commercially available with applicable critical current density in magnetic fields up to 5 T. One of the promising applications using MgB2 is a superconducting magnetic energy storage (SMES) coil. In our project, multi-strand cables with 600 A nominal current are designed for double-pancake (DP) coils with 400 mm inner diameter. The coil production processes in our project are wind-and-react (W&R) and react-and-wind (R&W) methods, in which a Rutherford-type cable consisting of eight (W&R) or ten wires (R&W) with specific twist pitch is reacted and then used to wind the DP coils, to investigate the suitable manufacturing process for MgB2 coils. The final goal is to fabricate five-stacked DP coils, made up of four DP coils by the R&W method and one DP by the W&R method with a total number of 512 turns, forming a 30 kJ SMES coil and to demonstrate compensation of voltage fluctuation on the BUS line of 48 V DC in a micro grid consisting of renewable energy source and liquid hydrogen supply system in our project. The first DP coils made by the two manufacturing processes are constructed and tested with regard to their properties such as critical current density in liquid helium to keep uniform temperature distribution throughout the coils.

Influence of AC Loss on Stress and Strain of Superconducting Coils

The second-generation (2G) high-temperature superconducting (HTS) coated conductors (CC) are increasingly used in power systems recently, especially in large-capacity superconducting magnetic energy storage (SMES). HTSCC in superconducting energy storage coil is subjected to thermal stress which is caused by thermal contraction due to AC loss. The thermal stress will degrade the critical currents and may cause the displacement of the superconducting coil and insulating epoxy resin. In this work, the AC loss of the superconducting coil is firstly obtained by finite element method (FEM) software COMSOL with the method of iterative conductivity. Furthermore, the effect of AC loss on the superconducting coil is thus analyzed by solving the coupling problems which include magnetic field, mechanical behaviors, and heat transfer in solids. The result shows that the AC loss of the superconducting coil is concentrated in the middle of the coil and the maximum AC loss density is 5.96 × 105 W/m3; the maximum stress laid at the inner radius of the coil and the maximum stress is 0.01 MPa.

Enhancing LVRT Capability and Smoothing Power Fluctuations of a DFIG-based Wind Farm in a DC Microgrid

Two primary challenges with a wind-turbine-based doubly-fed induction generator (DFIG) are low voltage ride-through capability and power fluctuations. To face with these challenges, in this paper, a new method using a superconducting magnetic energy storage (SMES) coil with fault current limiting function (SMES-FCL) is proposed. In this research, a previous configuration for a SMES-FCL is modified. In the modified topology, the number of components is minimized and a fuzzy-based controller (FC) with minimal rules for the SMES is suggested. Because of element minimization, the proposed method has a less implementation cost. Also, using the FC in the SMES leads to high accuracy and robustness, and a fast transient of the control system. The efficiency of the proposed method is supported by extensive simulations in MATLAB/Simulink.

Performance Improvement of a Bi-2223 Solenoid Coil With Optimal Ferromagnetic Disks

Solenoid-type superconducting magnetic energy storage (SMES) coils wound by Bi-2223 tapes have strong anisotropic magnetic field dependence due to the fundamental anisotropic property inherited from Bi-2223 materials. The maximum perpendicular field components appearing around the turns located at the two coil ends degrade the critical current and energy storage capacity of the whole coil, and even cause significant AC loss and possible hot-spots during practical SMES operations. To enhance the critical current and reduce the ac loss of the turns located at the two coil ends, this paper investigates a novel ferromagnetic raised-edge disk structure for adjusting the magnetic field orientation to be as close as possible to a parallel angle. Finite element simulations and performance comparisons with a test 0.2-H Bi-2223 solenoid coil without any ferromagnetic disk, with a conventional flat disk, and with the proposed raised-edge disk are presented. The results obtained show that the proposed raised-edge disk has much better effects towards critical current improvement and AC loss reduction compared to a conventional flat disk, especially for the terminal coil turns near the inner wall of the whole coil.

Voltage Sag Compensation using DVR based Superconducting Magnetic Energy Storage Coil with Pi Controller

Voltage sag is an primary energy satisfactory situation for which the dynamic voltage restorer (DVR) is known as an mighty gadget to mitigate them. The Dynamic Voltage Restorer (DVR) is fast, bendy and effective option to voltage sag hindrance. SMES science has the abilities to carry actual vigor storage attribute to look after consumers from the grid voltage fluctuations. The DVR can restoration the load voltage within few milliseconds. A few configurations and manipulate ways are proposed for the DVR. To clear up this trouble, super conducting magnetic power storage (SMES) situated dynamic voltage restorer (DVR) is introduced to preserve patrons from the grid voltage fluctuations. Because of its excessive vigor density and fast response, it's selected as the vigor storage unit to beef up the compensation ability of DVR. The paper concentrates on efficiency advantages of adding power storage to vigor digital compensators for utility purposes. Simulation results have been presented to illustrate and realize the performances of DVR below voltage sags stipulations. The results got by simulation using MATLAB established the effectiveness of this gadget in compensating voltage sags with very rapid response (relative to voltage sag time).

Eddy-Current Losses of a HT-SMES Coil Under Controlled and Uncontrolled Discharge Conditions

This paper presents an analytical approach of eddy-current loss in a high temperature superconducting magnetic energy storage coil based on finite-element algorithm and numerical circuit analyses. A solenoidal coil with step-shaped cross-sectional shape is introduced to reduce the total eddy-current loss of the whole coil by diminishing the eddy-current losses located at two coil ends. Two coil-current-dependent formulas are derived to estimate the eddy-current loss, e.g., 294 J for a 1.2 H/880 A Bi-2223 solenoidal coil in a 1000 V/500 kW constant-power energy discharge process and then the uncontrolled energy discharge process.

Pareto optimal design of sectored toroidal superconducting magnet for SMES

A novel multi-objective optimization design approach for sectored toroidal superconducting magnetic energy storage coil has been developed considering the practical engineering constraints. The objectives include the minimization of necessary superconductor length and torus overall size or volume, which determines a significant part of cost towards realization of SMES. The best trade-off between the necessary conductor length for winding and magnet overall size is achieved in the Pareto-optimal solutions, the compact magnet size leads to increase in required superconducting cable length or vice versa The final choice among Pareto optimal configurations can be done in relation to other issues such as AC loss during transient operation, stray magnetic field at outside the coil assembly, and available discharge period, which is not considered in the optimization process. The proposed design approach is adapted for a 4.5MJ/1MW SMES system using low temperature niobium–titanium based Rutherford type cable. Furthermore, the validity of the representative Pareto solutions is confirmed by finite-element analysis (FEA) with a reasonably acceptable accuracy.

A Suitable Design Method of SMES Coil for Reducing Superconducting Wire Usage Considering Maximum Magnetic Flux Density

Generally, high magnetic flux density is adopted in superconducting magnetic energy storage (SMES) coil design to reduce superconducting coil size and increase energy density. However, critical current density of the SMES coil is degraded by applying the high magnetic flux density to superconducting wire. This means that adopting the high magnetic flux density is not necessarily suitable for the superconducting wire reduction of the SMES coil. In this paper, the relationship between the maximum magnetic flux density within coil and superconducting wire usage of the SMES coil composed of solenoid or toroidal coil wound by MgB2, Bi2223, or REBCO wire was investigated. As a result, most suitable magnetic flux density within SMES coil for realizing the minimum superconducting wire usage in MgB2 , Bi2223, and REBCO wires were clarified. How to estimate the most suitable maximum magnetic flux density within coil for realizing the minimum wire usage in each superconducting wire was also investigated. Comparison between the rate of change of coil radius times maximum magnetic flux density and critical current density with respect to the maximum magnetic flux density is useful for obtaining the suitable maximum magnetic flux density for the minimum superconducting wire usage.