Jeffrey T. Dederer

Tubular Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycle Power Systems — Status

The solid oxide fuel cell (SOFC) is a simple electrochemical device that operates at 1000°C, and is capable of converting the chemical energy in natural gas fuel to AC electric power at approximately 45% efficiency (net AC/LHV) when operating in a system at atmospheric pressure. Since the SOFC exhaust gas has a temperature of approximately 850°C, the SOFC generator can be synergistically integrated with a gas turbine (GT) engine-generator by supplanting the turbine combustor and pressurizing the SOFC, thereby enabling the generation of electricity at efficiencies approaching 60% or more. Conceptual design studies have been performed for SOFC/GT power systems employing a number of the small recuperated gas turbine engines that are now entering the marketplace. The first hardware embodiment of a pressurized SOFC/GT power system has been built for Southern California Edison and is scheduled for factory acceptance tests beginning in Fall, 1999 at the Siemens Westinghouse facilities in Pittsburgh, Pennsylvania. The hybrid power cycle, the physical attributes of the hybrid systems, and their performance are presented and discussed.Copyright

Development of A Multiple HTS Current Lead Assembly for Corrector Magnets Application

Vapor-cooled current leads used for transmitting power to superconducting power equipment such as the corrector magnets in the SSC spools can introduce a significant heat leak into the cryostat which results in cryogen boil-off. Replenishing the boil-off or refrigerating and liquefying the vapors associated with the cooling of these leads may constitute a significant portion of the operating cost and/or the capital investment of the power equipment. Theoretical studies and experiments have demonstrated that the heat leak introduced by a current lead can be significantly reduced by using ceramic high temperature superconductor (HTSC) as part of the conductor in the current leads. 1-11

High temperature superconducting current leads for fusion magnet systems

Superconducting magnets for fusion applications typically have very high operating currents. These currents are transmitted from the room temperature power supplies to the low temperature superconducting coils by way of helium-vapor-cooled current leads. Because of the high current magnitude and the resistive characteristics associated with the normal metallic lead conductors, a substantial amount of power is dissipated in the lead. To maintain a stable operation, a high rate of helium vapor flow, generated by the boil-off of liquid helium, is required to cool the lead conductors. This helium boil-off substantially increases both the installation capacity and the operating cost of the helium refrigerator/liquefier. It has been demonstrated that the boil-off liquid helium can be significantly reduced by using ceramic high-temperature superconductors, such as Y-Ba-Cu-O, in the low temperature part of the lead conductor structure. This design concept has been conclusively demonstrated by a 2-kA current lead test model using Y-Ba-Cu-O

DESIGN AND ANALYSIS OF SMES-ETM ELECTRICAL INSULATION

The mechanical design and the electrical field analysis of the Ebasco/Westinghouse SMES-ETM coil electrical insulation system are presented. The electrical insulation design of the coil includes the turn to turn, layer to layer, and between the coil to the wall of the liquid helium vessel of the cryostat. A finite element analysis code (WEMAP) was used to obtain detailed electrical field plots of the high electrically stressed regions of the coil. These analytical results were used in conjunction with the experimental data of dielectric breakdown, available in the literature or obtained by in-house testing, to determine the optimum configuration and materials of the insulation spacers. An adequate design safety factor between the insulation capability and the maximum operating electrical stress was adopted to ensure the design integrity under all operating conditions and to allow for the uncertainties of the experimental dielectric breakdown data.

Testing and Performance of High Temperature Superconducting Current Leads

Vapor-cooled current leads generally used for transmitting power to a superconducting magnet can introduce a significant heat leak into the cryostat. Refrigerating and liquefying the vapors associated with cooling of these leads may constitute a significant portion of the power requirement of the refrigeration/liquefaction system. Theoretical studies and experiments have demonstrated that the heat leak introduced by a current lead can be reduced by using ceramic high temperature superconductor as part of conductor in the current leads.1–6