Roger W. Boom

Superconductive magnetic energy storage (SMES) external fields and safety considerations

The authors discuss preferred SMES configurations and the external magnetic fields which they generate. Possible biological effects of fields are reviewed briefly. It is proposed that SMES units be fenced at the 10 gauss (1 mT) level to keep unrestricted areas safe, even for persons with cardiac pacemakers. For a full-size 5000 MWh (1.8*10/sup 13/ J) SMES the magnetic field decreases to 10 gauss at a radial distance of 2 km from the center of the coil. Other considerations related to the environmental impact of large SMES magnetic fields are also discussed. >

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.

Superconductive energy storage for large systems

A summary report of a three-year study of superconductive energy storage for large utility systems is presented. The preferred conceptual design choices include: large, thin-walled solenoids, 1. 8 K cooling, TiNb in aluminum composite conductors at 5 tesla, bedrock structural support for both axial and radial forces, and a three-phase Graetz (ac/dc) bridge converter interface to the power grid. Preliminary estimates show that capital costs are given by

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

/kW = 40 + 125 (P/1000)-1/3(t/2)2/3Where P is the average power in MW and t is the discharge (peaking) time in hours. A typical operating loss is 10 ∼ 15% of the stored energy. The concept is technically feasible requiring only present day technology.

Superconductive energy storage for diurnal use by electric utilities

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.

Superconductive Inductor-Converter Units for Pulsed Power Loads

A summary report of a five-year study of superconductive energy storage for electric utility systems is presented, Conceptual designs over that period have all been for one layer solenoids of aluminum-NbTi composite conductors cooled to 1.8 K in superfluid helium, The solenoids are mounted underground in bedrock in one or more tunnels. The two preferred designs in 1980 are: a 15 tunnel solenoid arranged in a circular pattern and a large radius single tunnel solenoid. The electrical energy storage efficiency in all cases is 95 to 96%.

Magnetic and coagulation forces on a suspension of magnetic particles

Pulsed power loads of increasing magnitudes up to several hundred megawatts or more must be supplied in the near future. High energy physics research laboratory experiments and the longer range foreseeable needs for successful nuclear fusion reactors such as the University of Wisconsin Tokamak reactor designs are representative examples. Such large pulsed power demands are at best undesirable if not prohibitive, even for the largest electric power systems. Techniques for storing energy in superconductive inductors employing thyristorized converters are described. Circuits which serve to minimize both the pulsed power and corresponding reactive volt-ampere requirements from the three phase power system are presented. Exploitation of these circuits and related concepts from the control standpoint should provide a basis for designing power conditioning interface equipment to meet the challenging requirements of very large pulsed power loads looking to the future.

The UW-SMES design

Abstract It is shown that the magnetic force on a highly-magnetic particle in a slurry is a strong function of the particle shape and the concentration density of the magnetic particles in the suspension. An expression is derived for the coagulation forces between magnetized particles as a function of magnetic moment, size, and concentration.

The design of large low aspect ratio energy storage solenoids for electric utility use

The evolution of the University of Wisconsin (UW) superconducting magnetic energy storage (SMES) designs for electric utility use is traced from 1970 to the present. The UW-SMES design principles were used in the 1987-90 ETM competition by the EBASCO team of subcontractors (UW, Westinghouse, CBI, and Teledyne). Some recent post-ETM design improvements are discussed. The Wisconsin emphasis on 1.8 K pool cooling, cryogenic stability, and ripple design is stressed.<<ETX>>

A 100 kWh energy storage coil for space application

The preliminary conceptual design of a low aspect ratio solenoid (large diameter and small height) for diurnal energy storageuse is presented. The main advantage of this design is that the total radial force is only 5 ~ 10% that of previous designs resulting in small conduction heat leak through the insulating struts. The external pressure is less than 2 atmospheres which allows surface trench construction in surface rock; the pressures for previous underground bedrock designs were 20 to 100 atmospheres. A new use for diurnals to rage is presented in which larger SMES storage units replace intermediate load generation. In the example given an allowance of