War of the currents

The war of the currents was a series of events surrounding the introduction of competing electric power transmission systems in the late 1880s and early 1890s. It grew out of two lighting systems developed in the late 1870s and early 1880s; arc lamp street lighting running on high-voltage alternating current (AC), and large-scale low-voltage direct current (DC) indoor incandescent lighting being marketed by Thomas Edison's company. In 1886, the Edison system was faced with new competition: an alternating current system initially introduced by George Westinghouse's company that used transformers to step down from a high voltage so AC could be used for indoor lighting. Using high voltage allowed an AC system to transmit power over longer distances from more efficient large central generating stations. As the use of AC spread rapidly with other companies deploying their own systems, the Edison Electric Light Company claimed in early 1888 that high voltages used in an alternating current

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Related publications (6)

Study of a Novel OCXO Characterization Based on Oven Supply Currents for Enhanced Holdover Compensation

Jean-Pierre Aubry, Marcel Baracchi Frei, Cyril Botteron, Pierre-André Farine, Elham Firouzi, Davide Manetti, Nicolas Charles Yves Voirol

2008

Realization of high efficiency micromorph tandem silicon solar cells on glass and plastic substrates: Issues and potential

Christophe Ballif, Mathieu Gérard Boccard, Peter Cuony, Matthieu Despeisse, Andrea Feltrin, Franz-Josef Haug, Sylvain Nicolay, Martin Python

High conversion efficiency for (amorphous/microcrystalline) "micromorph" tandem solar cells requires both a dedicated light management, to keep the absorber layers as thin as possible, and optimized growth conditions of the microcrystalline silicon (μc-Si:H) material. Efficient light trapping is achieved here by use of textured front and back contacts as well as by implementing an intermediate reflecting layer (IRL) between the individual cells of the tandem. This paper discusses the latest developments of IRLs at IMT Neuchtel: SiOx based for micromorphs on glass and ZnO based IRLs for micromorphs on flexible substrates were successfully incorporated in micromorph tandem cells leading to high, matched, current above 13.8 mA/cm2 for pin tandems. In nip configuration, asymmetric intermediate reflectors were employed to achieve currents of up to 12.5 mA/cm2. On glass substrates, initial and stabilized efficiencies exceeding 13% and 11%, respectively, were thus obtained on 1 cm2 cells, while on plastic foils with imprinted gratings, 11.2% initial and 9.8% stable efficiency could be reached. Recent progress on the development of effective front and back contacts will be described as well. © 2010 Elsevier B.V. All rights reserved.

2011

Prospects for the use of high-T-c superconductors in fusion magnets and options for their test in SULTAN

Pierluigi Bruzzone, Stephen Alfred March, Boris Stepanov, Davide Uglietti, Rainer Wesche

In the last few years, the critical current densities of long commercially available REBa2Cu3O7-x (RE-123, where RE represents Y or a rare earth element) coated conductors have reached values of 250 A/cm-width at 77K and zero applied field. Even higher values of 600 A/cm-w (77 K, B = 0) have been demonstrated in shorter lengths. The attractive features of the use of these high-T-c superconductors (HTS) are operation temperatures above 20K and/or magnetic fields higher than those envisaged for the ITER TF coils. Possible operation conditions for HTS fusion magnets have been studied taking into consideration the possible further improvements of RE-123 coated conductors. Investigations of stability and quench behavior indicate that stability is not a problem, whereas quench detection and protection need attention. Because of the high currents necessary for fusion magnets, many tapes need to be assembled into a transposed conductor. The qualification of HTS conductors for fusion magnets would require their test at magnetic fields of 11 land currents well above 10 kA. The possibilities to test straight HIS conductor samples in SULTAN have been considered. For a test at 4.5 K, only the development of a low resistance joint between the HTS conductor under test and the NbTi transformer of SULTAN would be necessary. Tests up to 20K would require that the HTS sample is connected with the NbTi transformer by a conduction-cooled HTS bus bar of large thermal resistance similar to the HIS module of a current lead. HIS conductor tests at temperatures around 50K would be possible with modified cryogenics. (C) 2013 Elsevier B.V. All rights reserved.

Elsevier Science Sa2013

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