Shirabe Akita

Technical and Cost Evaluation on SMES for Electric Power Compensation

RASMES (Research Association of Superconducting Magnetic Energy Storage) in Japan developed a road map of SMES for fluctuating electric power compensation of renewable energy systems. Based on the progress of large superconducting coils, the technical status is already established to develop the several MWh class SMES for frequency control, load fluctuation compensation, and generation fluctuation compensation. With integrated operations of several dispersed SMES systems, it is expected that the 100 MWh class SMES for load fluctuation leveling (peak cut) can be introduced in the period of 2020-30, and the first 1 GWh class SMES for daily load leveling can be installed in the period of 2030-40. From the results of Japanese national projects, experimental device developments and SMES design studies, if the output power of SMES is 100 MW, the target cost of SMES can be evaluated with 2000 USD/kW of the unit cost per output power (the unit cost per kW).

Numerical analysis of a.c. losses in superconductors

Abstract A two-dimensional computational code to evaluate a.c. losses in superconductors has been developed using the current vector potential method (T-method), where the vector potential T is defined by ▿ × T = J . The current distributions in both superconductors and normal conductors are calculated while changing the conductivity of the superconductor so that the current density never exceeds the critical current density. The hysteresis and coupling losses evaluated by the numerical code agree with analytical solutions, as far as these are available. In order to verify the validity of the code, an experiment to measure the hysteresis and coupling losses was carried out using Nb-Ti/Cu filaments. The total loss evaluated from the numerical code agrees with that from the experiment. The numerical analysis, however, indicates that the hysteresis loss under quasi-steady magnetic field is less than the loss in the superconductor under transient field.

An optimal configuration design method for HTS-SMES coils

Recently, the properties of high temperature superconducting tapes have been in advance and high temperature superconducting magnets have been constructed and demonstrated. However, the high temperature superconducting tapes have different thermal characteristics compared with low temperature superconducting wires. Therefore, it is necessary to consider these characteristics of high temperature superconducting tapes at the magnet design stage. We proposed an optimal design method for superconducting coils wound with Bi2223/Ag tapes. In this paper, the configuration of 72 MJ SMES coils wound with Bi2223/Ag tapes are optimized.

R&D of a 500 m superconducting cable in Japan

Super-ACE project started to research and develop the superconducting AC power equipment as a national project in 2000 fiscal year. This project is R&D of the basic technologies of high temperature superconducting (HTS) cable, HTS fault current limiter (FCL), HTS magnet for reactor and transformer. Main subjects of the cable are to develop an HTS conductor rated 3 kA, cooling technology of a 500 m HTS cable of 700 A rated current, and the analysis of integrated HTS power system. The paper describes the background of this project, its target, major results of studies, and testing schedule of 500 m cable.

Development of SMES for power system control

Since 1999, a Japanese national project to realize commercially feasible SMES for designated applications has been promoted. Model coils for power system stabilization, load fluctuation compensation and frequency control have been fabricated and tested. In this paper, we introduce the present status of the project, including feasibility studies of an HTS SMES.

Transient thermal characteristics of cryocooler-cooled HTS coil for SMES

Thermal behavior of high-temperature super-conducting (HTS) coil is exceedingly different from that of low-temperature superconducting (LTS) coil. Therefore for the sake of the application of HTS coil to practical use, establishment of a new stability criterion for coil design becomes indispensable. In this study, a small-sized cryocooler-cooled HTS coil wound with Bi-2223/Ag tape was constructed and tested to evaluate the electromagnetic and thermal characteristics in the cryocooler-cooled HTS coil. We carried out experiments subjected to pulse current operation supposing SMES for power system stabilization. The simulation by a newly developed computer program based on the finite element method (FEM) agreed well with experimental results. In the computer program, short-sample data concerning the E-J characteristics, which depend on the orientation of applied magnetic field to the wide face of Bi-2223Ag tape, was adopted. By using the computer program, we also evaluate the thermal behavior of HTS coil graded according to the magnetic field distribution.

Deposition of Y2O3 buffer layers on biaxially-textured metal substrates

Abstract Biaxially aligned Y2O3 layers useful as buffer layers for high-Tc oxide films have been synthesized on metal tapes through a new and simple method. The Y2O3 buffer layers are deposited on biaxially-textured Ni substrates by an electron beam evaporation technique using Y metal as the evaporation source, and controlling the pressure of the deposition chamber. The obtained Y2O3 films are strongly oriented in-plane and out-of-plane. The φ scan through the Y2O3(222) peaks reveals clear fourfold in-plane symmetry and the in-plane full-width at half maximum (FWHM) of 10.9°. The rocking curve through the Y2O3(400) peak reveals the out-of-plane FWHM of 2.3°. The metal tapes buffered by Y2O3 may be served as long and flexible substrates for high performance biaxially-aligned high-Tc oxide tapes.

Experimental study of power system stabilization by superconducting magnetic energy storage

Superconductive Magnetic Energy Storage (SMES) is one of the effective measures to suppress system instabilities in electric power networks because of its fast response at exchanging electric power. Two types of experiments, dynamic and transient, have been performed to suppress instabilities by using an SMES unit on a model power system. The test system has a 60 kVA synchronous generator, a double-circuit transmission line connected to an infinite bus, and an SMES unit with an SCR converter. They simulate a salient pole synchronous generator of 600 MVA and a transmission line of 275 kV with 380 km in length. The SMES unit whose maximum stored energy is 100 kJ can exchange energy matched with the model system. The SMES unit could effectively suppress these instabilities by exchanging energy.

Electrical insulation characteristics of cold dielectric high temperature superconducting cable

For the optimization of electrical insulation design for high temperature superconducting (HTS) cable, evaluation of electrical insulation characteristics especially for butt gap of LN/sub 2/ impregnated cold dielectric (CD) which consists of the wrapped tape insulation impregnated with LN/sub 2/ plays an important role. This paper presents partial discharge (PD) inception and breakdown characteristics in LN/sub 2/ impregnated butt gap model which modeled a weak point of the wrapped tape insulation impregnated with LN/sub 2/ and cable model with short length with polypropylene laminated paper (PPLP/sup /spl reg//), Nomex/sup /spl reg// paper and cellulose paper. PD current pulse was found to have a steep rise time of /spl sim/ ns and amplitude of /spl sim/ tens /spl mu/A at PD inception voltage region. Little dependency of breakdown stress on the insulating material is found. PD inception stress is almost independent of insulation thickness of 1 to 3 mm. The requirement insulation thickness for 66 kV class HTS cable is estimated to be /spl sim/ 5 mm under PD-free condition from viewpoint of long-term reliability.

Dielectric properties of 500 m long HTS power cable

The 500-m high temperature superconducting (HTS) cable has been constructed in the Yokosuka area, CRIEPI, by CRIEPI, The Furukawa Electric Co. and Super-GM. Its design voltage is 77 kV and the thickness of the electrical insulation layer should be 8 mm made of semi-synthetic paper (polypropylene laminated paper). During cooling, the capacitance and dielectric loss tangent were measured periodically. After cooling, which means that the HTS cable was fully filled with liquid nitrogen (LN/sub 2/), the initial voltage withstand test was carried out. This paper describes the design method of the electrical insulation layer including determination of the testing voltage and the result of the initial voltage withstand test, and the permittivity calculated from the capacitance, and dielectric loss tangent.