Overview of current development in electrical energy storage technologies and the application potential in power system operation

Due to the stochastic nature of wind, electric power generated by wind turbines is highly erratic and may affect both the power quality and the planning of power systems. Energy Storage Systems (ESSs) may play an important role in wind power applications by controlling wind power plant output and providing ancillary services to the power system and therefore, enabling an increased penetration of wind power in the system. This article deals with the review of several energy storage technologies for wind power applications. The main objectives of the article are the introduction of the operating principles, as well as the presentation of the main characteristics of energy storage technologies suitable for stationary applications, and the definition and discussion of potential ESS applications in wind power, according to an extensive literature review.

A review of energy storage technologies for wind power applications

Energy storage: Applications and challenges

The vanadium redox flow battery, which was first suggested by Skyllas-Kazacos and co-workers in 1985, is an electrochemical storage system which allows energy to be stored in two solutions containing different redox couples. Unlike commercially available batteries, all vanadium redox flow batteries have unique configurations, determined by the size of the electrolyte tanks. This technology has been proven to be an economically attractive and low-maintenance solution, with significant benefits over the other types of batteries. Moreover, the soaring demand for large-scale energy storage has, in turn, increased demands for unlimited capacity, design flexibility, and good safety systems. This work reviews and discusses the progress on electrodes and their reaction mechanisms as key components of the vanadium redox flow battery over the past 30 years. In terms of future outlook, we also provide practical guidelines for the further development of self-sustaining electrodes for vanadium redox flow batteries as an attractive energy storage system.

A technology review of electrodes and reaction mechanisms in vanadium redox flow batteries

Intermetallic compounds containing $f$-electron elements display a wealth of superconducting phases, which are prime candidates for unconventional pairing with complex order parameter symmetries. For instance, superconductivity has been found at the border of magnetic order as well as deep within ferromagnetically and antiferromagnetically ordered states, suggesting that magnetism may promote rather than destroy superconductivity. Superconducting phases near valence transitions or in the vicinity of magnetopolar order are candidates for new superconductive pairing interactions such as fluctuations of the conduction electron density or the crystal electric field, respectively. The experimental status of the study of the superconducting phases of $f$-electron compounds is reviewed.

Superconducting phases of f -electron compounds

From detailed angle-resolved NMR and Meissner measurements on a ferromagnetic (FM) superconductor UCoGe (${T}_{\mathrm{Curie}}\ensuremath{\sim}2.5\text{ }\text{ }\mathrm{K}$ and ${T}_{\mathrm{SC}}\ensuremath{\sim}0.6\text{ }\text{ }\mathrm{K}$), we show that superconductivity in UCoGe is tightly coupled with longitudinal FM spin fluctuations along the $c$ axis. We found that magnetic fields along the $c$ axis ($H\ensuremath{\parallel}c$) strongly suppress the FM fluctuations and that the superconductivity is observed in the limited magnetic-field region where the longitudinal FM spin fluctuations are active. These results, combined with model calculations, strongly suggest that the longitudinal FM spin fluctuations tuned by $H\ensuremath{\parallel}c$ induce the unique spin-triplet superconductivity in UCoGe. This is the first clear example that FM fluctuations are intimately related with superconductivity.

/pdf/superconductivity-induced-by-longitudinal-ferromagnetic-1kqsqek827.pdf

Superconductivity induced by longitudinal ferromagnetic fluctuations in UCoGe.

The redox kinetics of VO2+/VO2
 + and V3+/V2+ couples on a carbon paper (CP, HCP030 N, Shanghai Hesen, Ltd., China) electrode were investigated in terms of their standard rate constant (k
 0) and reaction mechanism. The values determined for k
 0 for VO2+ → VO2
 + and V3+ → V2+ using the CP electrode are 1.0 × 10−3 and 1.1 × 10−3 cm s−1, respectively. The value of k
 0 increases by one or two order(s) of magnitude compared with values obtained using electrodes composed of pyrolytic graphite and glassy carbon. The acceleration of the redox kinetics of vanadium ions is a result of the large surface area of the CP electrode. An inner-sphere mechanism for the reaction on the surface of the electrode is proposed. The kinetic features of vanadium redox reactions on the CP electrode reveal that CP is suitable for use as the electrodes in vanadium redox-flow batteries.

Acceleration of the redox kinetics of VO2+/VO2 + and V3+/V2+ couples on carbon paper

Unambiguous evidence for the microscopic coexistence of ferromagnetism and superconductivity in UCoGe ( T Curie ∼2.5 K and T SC ∼0.6 K) is reported from 59 Co nuclear quadrupole resonance (NQR). The 59 Co-NQR signal below 1 K indicates ferromagnetism throughout the sample volume, while the nuclear spin-lattice relaxation rate 1/ T 1 in the ferromagnetic (FM) phase decreases below T SC due to the opening of the superconducting (SC) gap. The SC state is found to be inhomogeneous, suggestive of a self-induced vortex state, potentially realizable in a FM superconductor. In addition, the 59 Co-NQR spectrum around T Curie shows that the FM transition in UCoGe possesses a first-order character, which is consistent with the theoretical prediction that the low-temperature FM transition in itinerant magnets is generically of first-order.

Microscopic Coexistence of Ferromagnetism and Superconductivity in Single-Crystal UCoGe

We have carried out direction-dependent $^{59}\mathrm{Co}$ NMR experiments on a single crystal sample of the ferromagnetic superconductor UCoGe in order to study the magnetic properties in the normal state. The Knight-shift and nuclear spin-lattice relaxation rate measurements provide microscopic evidence that both static and dynamic susceptibilities are ferromagnetic with strong Ising anisotropy. We discuss that superconductivity induced by these magnetic fluctuations prefers spin-triplet pairing state.

/pdf/anisotropic-magnetic-fluctuations-in-the-ferromagnetic-28w8dhgfs3.pdf

Anisotropic Magnetic Fluctuations in the Ferromagnetic Superconductor UCoGe Studied by Direction-Dependent ^{59}Co NMR Measurements

The present study was undertaken to examine the phase equilibria in the Sn–Ag–Bi ternary system, a promising candidate for use as a Pb-free solder A regular solution approximation as well as the sublattice model was applied to describe the Gibbs energy for the individual phases Themodynamic parameters were achieved by combining the experimental results obtained by differential scanning calorimetry and energy dispersive X-ray microanalysis in the present study with data from the literatures The calculation of phase diagrams showed that there are three invariant reactions in the liquidus surface of the ternary system and that the ternary eutectic point falls at 05%Ag, 539%Bi and 139°C

https://www.jstage.jst.go.jp/article/matertrans/42/5/42_5_722/_pdf

Isamu Satoh

Papers

Superconductivity induced by longitudinal ferromagnetic fluctuations in UCoGe.

Acceleration of the redox kinetics of VO2+/VO2 + and V3+/V2+ couples on carbon paper

Microscopic Coexistence of Ferromagnetism and Superconductivity in Single-Crystal UCoGe

Anisotropic Magnetic Fluctuations in the Ferromagnetic Superconductor UCoGe Studied by Direction-Dependent ^{59}Co NMR Measurements

Thermodynamic Analysis of the Sn-Ag-Bi Ternary Phase Diagram