Wisconsin Alumni Research Foundation

The United States of America As Represented by the Secretary of

Roger W Boom

Yehia M Eyssa

Harold A Peterson

Warren C Young

Xianrui Huang

Mostafa K Abdelsalam

Glen E McIntosh

Ronald W Moses, Jr

John Sutton

A superconducting energy storage magnet is constructed for mounting in relatively shallow trenches or tunnels to provide superconductive energy storage for applications such as power system load leveling. The magnet includes composite superconductors arranged in substantially planar coil layers around a central axis. A first and second coil layer have an inner support structure between them to which the conductors of the layers are engaged. The inner support structure carries the magnetically induced forces on the conductors of the coils. The net radial magnetically induced force is opposed by the rigid structural material of the inner support structure and by support struts which extend from the periphery of the inner support structure to a surrounding support wall such as the wall of a trench. The conductors in each layer, and the inner support structure between them, have matching vertically (axially) undulating ripples over the circumference of the magnet. The ripples accommodate stresses imposed on the magnet during cool down from ambient temperatures to cryogenic temperatures, while the inner support structure is rigid radially to carry the magnetically induced radial forces on the conductors so that substantially no flexing of the conductors occurs during charge up and discharge of the magnet.

Vertically rippled superconductive magnetic energy storage

A superconducting magnet is formed having composite conductors arrayed in coils having turns which lie on a surface defining substantially a frustum of a cone. The conical angle with respect to the central axis is preferably selected such that the magnetic pressure on the coil at the widest portion of the cone is substantially zero. The magnet structure is adapted for use as an energy storage magnet mounted in an earthen trench or tunnel where the strength the surrounding soil is lower at the top of the trench or tunnel than at the bottom. The composite conductor may be formed having a ripple shape to minimize stresses during charge up and discharge and has a shape for each ripple selected such that the conductor undergoes a minimum amount of bending during the charge and discharge cycle. By minimizing bending, the working of the normal conductor in the composite conductor is minimized, thereby reducing the increase in resistance of the normal conductor that occurs over time as the conductor undergoes bending during numerous charge and discharge cycles.

Superconducting energy storage magnet

A superconducting energy storage magnet is formed having inner (13) and outer (14) coils which are supported and restrained by an inner support structure (15) comprised of thermal and electrically conductive rails (33) which engage and parallel the turns of composite conductors (30, 31) in the two coils. Each of the support rails (33) is electrically isolated from adjacent support rails by insulating spacers (33) between layers and an insulating spacer (35) between the rails for the inner and outer coils. The spacing between turns in the inner and outer coils preferably progressively decreases toward the top and bottom ends of the magnet in a manner to best direct the magnetically induced forces on the composite conductors (30, 31) into the inner support structure. The two layer coil structure causes the forces on the conductors when current is flowing therethrough to be directed primarily inwardly toward the inner support structure (15).

Energy derived from an alternating current power system is stored in a superconducting magnet or inductor. The transfer of the energy is reversible so that the energy stored in the superconducting magnet can be returned to the alternating current power system. Generally, the energy is stored when surplus energy is available, due to low demand. The energy stored in the superconducting magnet may be returned to the power system when demand is high. High efficiency in the storage and return of the energy is achieved. A reversible converter is provided between the alternating current system and the superconducting magnet so that the magnet is supplied with direct current when energy is being stored. The converter may be adjusted so as to convert directcurrent into alternating current when it is desired to return the stored energy to the power system. The converter may comprise a rectifier-inverter system utilizing controlled rectifiers and a variable firing angle controller which is adjustable to control the operating mode of the rectifier-inverter system. The controller may be adjusted so that the system functions as a rectifier unit to convert the alternating current to direct current for the storage of energy in the superconducting magnet. The controller may be adjusted to a different firing angle so that the system functions as an inverter to convert direct current from the magnet into alternating current which is returned to the power system. The energy storage system can have lower losses than systems of prior types, such as pumped hydro-storage systems. The superconductive magnet system also has the ability to damp electro-mechanical oscillations in the power system.

Superconductive energy storage for power systems

An inductor device having a superconducting coil winding capable of maintaining a relatively large current flowing therethrough, and a normal conducting shield winding surrounding the superconducting coil. The superconducting coil and the shield are electrically connected in parallel with the shield functioning to maintain the current and the magnetic field in the superconducting coil substantially constant. The superconducting inductor device can be used to store energy and to return the stored energy to an energy consuming load over a relatively short period without incurring large losses in the superconducting material. This result is obtained by making the self inductance of the shield substantially equal to the mutual inductance between the shield and the superconducting coil, or by inserting a controlled compensating voltage source in series with the shield, so that pulse currents are conducted by the shield. Proper spacing of the shield windings around the superconducting coil will result in substantially no magnetic field present in the coil due to current in the shield.

Shielded superconducting inductor device

An electrical magnet having at least one turn of electrical conductor which is continuously rippled in small radius arcs around is larger circumference. Each ripple in the conductor is formed to lie in a plane normal to the net magnetic field experienced by that ripple. For the special case of a planar turn of conductor, the ripples lie in substantially the same plane as the conductor turn itself. When current is flowing in the rippled conductor, the conductor will experience a magnetically induced force directed outward normal to the conductor. To oppose this outwardly directed force, the conductor is provided support by means which engage the conductor at the inner portions of the conductor between the ripples therein. The support means may consist of members or columns extending to a solid circular wall as, for example, a wall formed in bedrock. The tensile load in the rippled conductor is much less than in an unsupported large radius circular conductor, and, in addition, the rippled conductor is capable of undergoing expansions and contractions without building up damaging strain levels in the conductor. A superconducting rippled conductor magnet may be thermally insulated from warm support structure by thermal shields and vacuum dewars which are also rippled.

Support structure for rippled superconducting magnet

A radial magnetic field gradient applied from an elongated central source is traversed parallel to the elongation by a turbulent flow of a slurried mixture of magnetic and nonmagnetic components in the presence of a force thereon opposing in direction the attractive force of the magnetic field upon the magnetic components whereby the respective components are separated by the disparate forces and the flow acts to continuously advance the separation and direct separated components toward related collecting stations.

Growing community of inventors

Madison, WI, United States of America

Roger W Boom