NbTi foil thermally controlled switches for superconducting converters with operation frequency up to 50 Hz.: Part 1: Experiment
The increase of the operation frequency of superconducting converters up to 50 Hz opens new ways to improve their parameters. Thermally controlled switches using NbTi foil are able to operate at industrial frequency with reasonable efficiency and dynamic parameters. Such switches have been developed and tested. The paper presents experimental results of static and dynamic behavior of the switches. The rectification mode was tested with different shapes of the applied voltage, with currents from 150 to 450 A, voltages from 10 mV to 2.5 V and recovery times between 1 and 10 ms. The switches presented here have experimentally demonstrated superior dynamic parameters at higher efficiency than the ones reported in literature up to now.
An assessment of self-(Cold-) supported SMES systems
Abstract The perceived long-range application of Superconducting Magnetic Energy Storage (SMES) has been for large-scale applications. Since SMES is highly efficient and has a rapid response time, it has a significant technical advantage over other storage technologies. Though the cost per unit of stored energy, $/kWh, for several major components, such as the superconductor and the cryostat, decrease as plant size increases, the amount of structural support that is required to withstand the electromagnetic force is directly proportional to the stored energy. Recognition of this fact led to the proposal of warm- or external-supported SMES, which has been the primary technology researched for the past 20 years. Recently, a team led by Bechtel suggested that cold or self support would be cost effective for SMES plants of intermediate size, i.e., from a few to several hundred MWh. This paper evaluates the cold- or self-supported SMES design to determine if it has sufficient material to withstand the electromagnetic forces. The design is shown to meet a criterion derived from the virial equation. Earlier work, which predicted that larger quantities of material are required, is reviewed.
Continuity, Legitimacy, and Agricultural Development: Conclusions
This chapter aims at bringing together the principal conclusions of the volume, emphasising some particular aspects and questions. Policy continuity in relation to the late 1980s was rightly defined by the Aylwin government policymakers as an essential instrument for further agricultural growth. But in a democratic environment the Aylwin policies, in part precisely because of their strong element of continuity, could be implemented only if they were perceived as legitimate by the majority of the rural population, and by the poor in particular. This means that substantial improvements in agricultural income distribution, and in the quantity and quality of the social services provided to the rural poor, were unavoidable. In order to achieve legitimacy it was, and is, necessary to introduce changes. A lucid, creative combination of continuity and change was the only guarantee of success for the Aylwin policies, and for those of future democratic administrations. Continuity and legitimacy are the fundamental pillars for democratic agricultural development.