Tsutomu Tamada

Field Test Result of 10MVA/20MJ SMES for Load Fluctuation Compensation

SMES of the 10 MVA for the power control in power system has been manufactured, and connected to a real power grid. In addition, innovative basic researches, for example, low cost converter, maintenance-free cryo-coolers, inter-locks system and so on, have also been developed. The SMES was installed in the metal rolling factory with hydro power plant. Field test has been carried out for load fluctuation compensation. SMES was able to compensate for the active power according to the fluctuating load, and confirm the situation with a smooth load change of 11 kV bus of hydro power stations. In this paper, field test results will be presented.

Development of a High-Efficiency Conduction Cooling Technology for SMES Coils

YBCO(YBa2Cu3O7) wires have superior characteristics such as high energy densities, thus allowing the fabrication of large-scale, high power-output superconducting equipment applications. A high voltage is desired to achieve a large power output from a superconducting coil, and is realized by improving the insulating properties of the coil with the introduction of solid insulation. However, because high temperature superconducting wires have high critical temperatures and thermal tolerance compared to metal-based superconducting wires, the benefits offered allow the insulated superconducting coil to be directly cryocooled. In a helium circulation cryocooling system, the aluminum-fabricated transmission heat shields are coated around the surface of the coils to cryocool equally, and are embedded into the transmission heat shields with the conducting pipe allowing helium gas to circulate. We manufactured a conduction cooled model coil of 600 mm class diameter, and have verified the ability to realize a cooling of more than 3 W/m2 for coil surface heat flux at an operating temperature of 20 K using the demonstration cooling system. In addition, we have also evaluated the electric insulation performance, which is in contradiction to the cooling performance. The conduction-cooled YBCO coil withstood up to DC 13 kV voltages at 20 K.

Development of High Strength Pancake Coil With Stress Controlling Structure by REBCO Coated Conductor

High strength against electromagnetic force is required for high magnetic field and large capacity coil in order to develop large-capacity superconducting magnetic energy storage (SMES) systems for electric power system control. Also, suppression of delaminating of Yttrium (Y) based coated conductor in a coil is required to manufacture the highly reliable and durable superconducting coil. Insulating coating, using liquid resin of low-temperature-curable-polyamide, was developed and showed durability at very low temperature without deterioration of transport properties of superconducting wire in a coil. Combining paraffin molding, delaminating, and deterioration of transport properties of superconducting wire were not also observed in a coil. These insulating techniques were applied to the pancake coil, in which superconducting wire and the reinforcing outer plates of the coil withstand electromagnetic force. The double pancake coil of this coil structure, called “Yoroi-coil; Y-based oxide superconductor and reinforcing outer integrated coil” was prepared and the durability against electromagnetic force by hoop stress test was verified. The coil achieved 1.5 kA transporting at 4.2 K in 8 T back-up magnetic field without the degradation of transport properties. Maximum hoop stress at the hoop stress test reached 1.7 GPa, based on the calculations. This result confirmed that Yoroi-coil structure has a capability to withstand the large hoop stress, which exceeded the tensile strength of Y-based coated conductors, and bring out highly durable and reliable superconducting coils.

Development of Highly Effective Cooling Technology for a Superconducting Magnet Using Cryogenic OHP

A highly effective cooling technique for a superconducting magnet is proposed by incorporating the cryogenic oscillating heat pipes (OHP) as cooling panels in the coil windings. The OHP is a high performance two-phase heat transfer device, which can transport several orders of magnitude larger heat loads than heat conduction of solids. The cryogenic OHP using , Ne, and as working fluids have been developed and tested at the operating temperature ranges of 17-25 K (H2), 26-32 K (Ne), and 67-80 K (N2). The measured effective thermal conductivities were reached to 500-3,000 W/m · K (H2), 1,000-8,000 W/m · (Ne) and 10,000-18,000 W/m · K (N2). The high thermal transport properties of the cryogenic OHP and its application as the cooling components of superconducting magnets are also discussed.

Development of Cryogenic Oscillating Heat Pipe as a New Device for Indirect/Conduction Cooled Superconducting Magnets

Cryogenic oscillating heat pipes (OHPs) have been proposed as a new heat transfer device for conduction/indirect cooling of high-temperature superconducting (HTS) magnets. OHP is a highly effective two-phase heat transfer device which can transport several orders of magnitude greater heat flux than the heat conduction of solids. The performance of cryogenic OHPs has been intensively examined and the results indicate the ability of dramatically improving the performance of HTS magnets. Semi-empirical correlations stating thermo-physical properties of cryogenic OHPs are introduced based on those of room temperature OHPs. The modeling with non-dimensional quantities is useful for the design of cryogenic OHPs.

Achievement of High Heat Removal Characteristics of Superconducting Magnets With Imbedded Oscillating Heat Pipes

Oscillating heat pipes (OHP) for cryogenic use are being developed to improve the heat removal characteristics of high-temperature superconducting (HTS) magnets. It is generally difficult to remove the heat generated in HTS windings, because the thermal diffusivities of component materials decrease with an increase of the operating temperature. Therefore, a local hot-spot can be rather easily generated in HTS magnets, and there are possibilities of observing degradation of superconducting properties and/or mechanical damages by thermal stresses. As a new cooling technology to enhance the heat removal characteristics in HTS magnets, the cryogenic OHP is proposed to be imbedded in magnet windings. The feasibility of cryogenic OHP has been confirmed by fabricating proto-types and by observing stable operations using hydrogen, neon and nitrogen as the working fluid. A high thermal conductivity was achieved that surpasses those of high-purity metals. We also propose a modified-type OHP to mitigate the orientation dependence.

Unit Coil Development for Y-SMES

A superconducting magnetic energy storage system (SMES) for electric power system control has been developed using Yttrium (Y)-based coated conductor of high performance in Ic and mechanical properties, in order to fulfill the requirements for large capacity and cost reduction of the SMES. The target stored energy of the coil required for the SMES system of 100 MVA output power is 2 GJ class. The conceptual designed coil of toroid type consists of one hundred eighty unit coils of 2.8 m outer diameter and each unit coil is connected to each converter of a multi-cell type. Due to this design concept, the main unit coil specifications of 2 kA current, 2 kV voltage, 600 MPa hoop stress tolerance and 3 W/m2 heat flux around 20 K can realize the SMES system. Coiling technologies have been developing using Y-based wire for SMES. A small multi-layer coil was manufactured and its electromagnetic force characteristics were verified by 600 MPa class hoop stress tests. A bundled-conductor coil of 650 mm class diameter was also manufactured and its current characteristics were verified by 2 kA class large current tests.