M.K. Abdelsalam

Test results from the SMES proof of principle experiment

A proof-of-principle experiment (POPE) has been conducted to demonstrate the stability and operation of the superconducting magnetic energy storage (SMES) conductor in an engineering test model (ETM) design. The experimental facility includes: a 100-kA DC power supply; a 4-T, 1-m bore, background field split solenoid: a three-turn-1-m-diameter test coil for the ETM conductor; a dewar for operation of the solenoid and test coil, at 1.8 K and 1 atm; and support systems for vacuum, helium supply and recovery, and data acquisition. The test facility exactly duplicates the electric, magnetic, and thermal conditions expected for the ETM conductor. A report is presented on measurements of conductor stability vs. transport current, applied magnetic field, and cooling from liquid helium. The measurements characterize the conductors stability against finite-length traveling normal zones and against quenches resulting from transient normal zones. The data qualify the conductor for dependable use at 50 kA, 4 T, and 1.8 K.

Micro SMES magnet configurations for reduced stray field applications

Reduced field coil configurations offer an attractive design alternative for small superconductive magnetic energy storage (/spl mu/SMES) systems. These commercially available systems are currently being used for improving the power quality in power conditioning sensitive processes. A reduced field design of /spl mu/SMES would allow its use in high-field sensitive environment. In this paper, proposed multiple parallel solenoids enclosed in one container with alternating field directions is presented and compared to a single solenoid. The parametric study covers stored energy, conductor volume, and overall magnet system dimensions. The efficiency of stray field reduction compared with the conventional single solenoid is also presented.<<ETX>>

Operational aspects of superconductive magnetic energy storage (SMES)

The use of superconducting magnetic energy storage (SMES) is assessed from an operational point of view. The useable storage size for an SMES unit is determined for real utility load demand curves of previous years. The SMES size to be added in the future then becomes an extrapolated size from the size that would have been suitable in past years. Some general conclusions are: SMES should be used for large scale load-leveling rather than small scale peaking; the most likely duty cycle is 8 hours charging at night and 15 hours discharging during day time; the high efficiency (98%) of storage leads to lifetime 15% fuel cost benefits vs. intermediate cycling generation and 30% fuel cost benefits vs. all other storage; and SMES is a new source of ± spinning reserve with rapid 50 msec complete power reversal.

The Potential Impact of Developing High TC Superconductors on Superconductive Magnetic Energy Storage (SMES)

The discovery of superconductivity with Tc > 77 K (liquid nitrogen boiling temperature) is potentially of great importance for large scale electric utility applications such as the transmission and storage of electrical energy. Superconducting magnetic energy storage (SMES) is already a promising technology for electric utility load leveling. Therefore, it is useful to assess SMES with oxide superconductors cooled by inexpensive and plentiful liquid nitrogen (LN2) instead of NbTi cooled by the more expensive liquid helium. Liquid nitrogen cooling will significantly reduce the refrigeration energy requirements, and, especially, would help make small size SMES units more economic. The paper presents the impact of LN2 on efficiency, design and economics of SMES.

Structure optimization of space borne toroidal magnets

An optimization study aimed at minimum weight under certain constraints on module size and weight has been carried out. This study includes a structural material survey of materials with high specific strength and modulus, and an analysis of the effectiveness of coil configuration parameters on the value of E/M, energy stored per unit mass. Some typical structure problems, such as buckling in the bucking cylinder, are also discussed. >

Superconducting magnet design for Fixed-Field Alternating-Gradient (FFAG) accelerator

The FFAG accelerator requires static fields that increase with radius along the accelerator midplane according to B=B/sub 0/(R/R/sub 0/)/sup 13.4/. The field is generated by equally spaced magnets around the circumference and varies from a maximum of 4.1 T to a minimum of -1.9 T. The general coil design employs cryostable magnets wound with aluminum stabilized superconductor. Each magnet has resistive pole face windings outside of the cryostat to allow for field fine tuning after construction. A set of iron-free coil windings generate the required field distribution. >

Performance characteristics of the 60 kA SMES conductor

We report the operating characteristics of the monolithic SMES conductor designed for operation at 60 kA, 5.1 Tesla in a 1.8 K bath of subcooled helium. Details of the experimental arrangement and procedures are presented as background. At 1.85 K the conductor has been operated up to 75 kA, and with maximum field conditions of 4.75 Tesla. Conductor performance is compared to the load line and design point of the Engineering Test Model (ETM). Transient stability is also demonstrated. Maximum conditions experienced by the conductor were limited by facility operation rather than by the conductor itself.<<ETX>>

Conductor joint performance during the Ebasco team SMES POPE (Proof of Principle Experiment)

A joint in the superconductor and stabilizer is added to the ETM conductor in the POPE. The joint design is similar to that proposed by Westinghouse for the SMES ETM field joints. Fabrication of the joint is described. Measurements on the performance of the superconducting joint operated in subcooled He II and of the stabilizer joint at 14 K are reported. Measured superconductor joint resistance is 1.6 n/spl Omega/, which agrees with previous analytic calculations. The stabilizer joint RR matches the conductor stabilizer RR. The joint met or exceeded all operational requirements throughout the experiment demonstrating its reliability and small joule heating.<<ETX>>

Design and optimization of hydrogen cooled pulsed storage inductors for electromagnetic launchers

Experimental results are reported on hydrogen-cooled aluminum cryoresistive coils operating at frequencies greater than 1 Hz. It is shown that eddy current losses due to pulsing are minimized by using single-layer coils. Higher losses of cabled conductors and multilayer coils are caused by self-shielding of each conductor or layer from the AC fields from the other conductors. I/sup 2/R losses for cable is low if the wire size is much smaller than the skin depth (d >

Pulsed magnetic energy storage for space applications

Toroidal energy storage magnets can be used as power supplies for many space applications. Their list of advantages include high efficiency, light weight, zero stray magnetic field, zero electro-magnetic radiation, and fast pulsing. Superconducting toroidal field coils with an inner small cryoresistive shield are proposed. Both the superconducting coil and the cryoresistive coil are connected in parallel. Their configuration is such that energy pulses are drawn mainly from the resistive coil, while the superconductive coil is shielded from the resulting AC field and current produced. The relationships between system parameters, such as coil dimensions, ampere meters, coil surface area and structural mass on one side, and the coil aspect ratio, stored energy and maximum field on the other side are derived for toroidal coils in rectangular and bending free D-shaped configurations.