06 Electrical power generation and utilization (scientific, technical)

lithium ion cells. These cells provide 2.4-2.5 V operating voltage and without the safety concerns associated with using lithium metal or carbon anodes.

00/01936 Stability enhancement of a multimachine power system using fuzzy logic based power system stabilizer tuned through genetic algorithm Lakshmi, P. and Khan, M. A. E/w. Pow~. .S.!,.sf. Res.. 2000. 22. (2). 137-145 The paper presents a procedure for application of Fuzzy Logic Power System Stabilizer (FPSS) for stability enhancement of a multimachine power system. The location of Power System Stabilizer (PSS) is determined using critical modes and participation factors for different operating conditions. A simple configuration is chosen for FPSS with a speed deviation of synchronous generator and its derivative as input signals. The parameters of the stabilizers are tuned through simulation of non-linear model of power system under chosen disturbance using Crowding Genetic Algorithm (CGA) to minimize a Root Mean Square Deviation (RMSD) index of the concerned state variable which maximizes the damping of the critical mode. Results obtained from a two-area, five-generator power system indicate the improved performance of FPSS over conventional P55.

00101937 Stability of a Cu10 photoelectrode in an electrochemical cell and the performances of the photoelectrode coated with Au and SIO thin films Khan, K. A. App’lictl _&erg!, 2000. 65. (l-4). 59-66. The photoresponse and stability of CuzO films have been examined. Thermodynamic calculations showed that. for CuzO, there exists a region of chemical stability potential between -0.218 and -0.489 V(SCE) for oxidation and reduction potential, respectively. In an aqueous solution, a deterioration in power output occurs at a rate of 50% per day. To stahilize the photocurrent, thin deposits of Au and SiO films onto CuzO electrodes have been studied. For the Au deposition, the photocurrent was either quenched or reduced. For the SiO deposited photoelectrode, its effect was to decrease the quantum efficiency of Cu,O. However, the deposition does not affect the band gap at 2.1 I eV (which ensued for an uncoated sample).

OOlO1938 Synthesis and characterization of novel urethane crosslinked ormolytes for solid-state lithium batteries De Zea Bermudez, V. So/it/ Srote lorric,.~. 1999. 116. (3.4). 197-209. This paper proposes a novel family of Li+-based organic/inorganic materials obtained by the sol-gel process. The compounds, named urethanesils, are ohtained as thin. transparent, elastomeric and amorphous monolithic films. They incroporate solvating pendant Me end-capped short poly(oxyethylene) chains, which are covalently bonded to the silica backbone by means of urethane cross-links. The reaction between 3- isocyanatopropyltriethoxysilane and hepta(ethylene glycol) Me ether (HEGME) encourages the formation of urethane linkages. Li+ has been introduced in the urethanesils as lithium triflate (LiCF1S03). Two compositions of salt have been considered: n = 100 and 8, where n represents the molar ratio of (OCH2CH,) units per lithium ion. Conclusive evidence is produced by infrared spectroscopy that. although the oligopolyether chains of HEGME become less disordered upon formation of the inorganic network, disorder is induced by the additions of salt.

00101939 Synthesis of Li,Ni,,ssCoO.rsOa by the PVA-precursor method and charge-discharge characteristics of a lithium ion battery using this material as cathode Ho-Jin, K. J. Pnw~ .Sowu~.v. 1999. X3. (I-2). X4- 92. Polycrystalline powder of Li,Ni,, x?Co .O cl is 2 was synthesized from poly (vinyl alcohol) gel (a PVA- precursor). The crystalline phase of Li,Ni,,&oa iTOz was developed without any minor phase above 600°C. The crystallization proceeded without any prominent heat event, which indicated homogeneous distribution of constituents and insignificant amount of diffusion barrier. The crystalline powder prepared from the PVA-precursor had relatively smaller particle size, larger surface area. and higher carbon content than the one prepared by the conventional solid state reaction. Charge-discharge property was studied by using a coin-type cell containing Li,NionsCocr isO: as cathode material. and LI metal as the anode. in a potential range of 2.X-4.3 V. Initial discharge capacity (at a rate of C/IO) of the was 170 mA h/g. At high rate of IC. the cycling reversibility for the cell with Li,Ni,,,$Co,, ,TO~ prepared from the PVA-precursor was observed to be much better than that with the one prepared hy the solid state reaction. After 90 continuous cycles at constant rate of IC the decrease of discharge capacity was less than 20 mA h’g in the case of the PVA- precursor method. whereas it was about 80 mA h/g for the solid state reaction.

00101940 The Gaston Plant6 medal address - metallic and alloy structures in battery grids Bagshaw, N. E. J. of Poi~r S~WW.S, 2000. X5. (I). Y- 14. Any metallic structure consists of an array of positively charged ions in a sea of electrons. Actual metal structures are not perfect lattices but contain imperfections or dislocations. The dislocations enable the metal to be deformed. Replacing some of the ions in the parent lattice by ions of the alloying metal to form a solid solution forms alloys. The degree of solid solution depends on the geometry of the system: the relative sizes of the two ions. Some metals also form compounds and the likelihood of this occurring depends on the relative electronegativity values of the elements concerned. It is shown that the ionic sizes and electronegativity values can be used

together to form a solubility chart and such a chart ix constructed for lead and its potential alloys. From the chart, it is posnihle to explain the properties of lead alloys, such as hardness, creep strength. grain-refining activity and castability. The grain boundaries in alloy structures are full of dislocations and are therefore areas of high activity. It is shown that. in some cases, severe intergranular corrosion can occur which could result in disintegration of a battery grid and premature failure of a battery. Examples of actual battery grid alloys and their properties illustrate the above principles of metal and alloy structures. Possible future developments of alloys are also proposed.

00101941 The pioneer plant concept: co-production of electricity and added-value products from coal Neathery. J. Fw/, 1999. 78. (7). XI 5 -X23 Technologies have been developed for the clean. efficient use of coal for power generation; however, there exist some harriers to their adoption and implementation. These technologies are essentially based upon the gasification of coal, which also provides ,I route for the synthesis of chemicals and fuels from coal. An overview is given of commercial experience of power generation hy integrated gasification combined-cycle, and chemical production. Against this background, a ‘Pioneer Plant’ concept is described that can facilitate the introduction of advanced technologies through the co-production of power and added value products in a single plant. A discussion is also included on the potential technological, economic, and greenhouse gas reduction advantages that can be realized through the development of such a multiplex operation.

00101942 The use of instantaneous symmetrical components for balancing a delta connected load and power factor correction Ghosh, A. and Joshi. A. E/W. PWI L’I’ SI )I Kc\.. 2000. 54. (I ). 67 74. This paper presents a novel way of generating the reference currents for an active filter and/or a static compensator. A compensator structure is proposed which is capable of balancing an unbalanced delta-connected load that may also draw harmonic currents. In addition to balancing the load, the supply side power factor is also made unity. The theory of instantaneous symmetrical components is used here to obtain three-phase reference currents that are to be tracked by the compensator in a hysteresis band control scheme. Simulation studies are used to demonstrate the feasibility of such a scheme.

00101943 Theoretical calculations for usin positive electrode compression to increase lead-acid battery 7 I fe Edwards, D. B. and Schmitz, C. J Pow~ Srurv~ v\. YWOO. X5. ( I). 63 7 I Investigators have confirmed that applying a small amount of mechanical pressure. approximately 1 bar (IO Pa), to the face of the positive electrode can dramatically increase the life of deep cycled. lead acid batteries. In this paper. we calculate the pressures required to stabilize the active material in the positive electrode based on the ‘Agglomerate of Spheres’ model. The calculations agree closely with the experimental observations. In addition to these calculations, we also provide another possible interpretation of the ‘Agglomerate of Spheres’ model and give an improved estimate for the surface tension of lead dioxide, an important physical quantity for the model.

00101944 Thermal modeling and design considerations of lithium-ion batteries Al Hallaj, S. J. POIIW .%Jww\. 1999. X3. (I 2). I X A simplified one-dimensional thermal mathematical model with lumped parameters was used to simulate temperature profiles inside lithium-ion cells. The model makes use of heat-generation parameters established experimentally for the Sony (USl8650) cell. The simulation results showed good agreement with temperature measurements at C:2. (‘3. and C6 discharge rates, while some deviation was noticed for the Cl discharge rate. The model was used to simulate temperature profiles under different operating conditions and cooling rates for scaled-up cylindrical lithium-ion cells of IO and 100 A h capacity. The results demonstrate a strong effect of the cooling rate on cell temperature for all discharge rates. A si,gnificant temperature gradient inside the cell was found only at higher cooling rater. where the Biot number is expected to he greater than 0. I. At Iow,er cooling rates. the cell behaves as a lumped sy\lerrl with uniform tcmperatui-e. To establish the limits of temperature allownhle in scale-up hy the \implifird model. commercial lithium-ion cells at different open circuit potential\ &cre tested inside an accelerated rate calorimeter (ARC‘) to determine the onset- of-thermal-runaway (OTR) temperatures. Sony (I’Sl8650) cells at 4.06. 3.0. and 2.X V open circuit voltage (OCV) here tested and their measured OTR temperature were found to be 104, 109. and 144’C. respectively. A shai-p drop in the OCV. indicating internal short circuit. was noticed at temperatures close to the melting point elf the \eparator material for all open circuit voltages.

00101945 Transient study of two 500 kV coupled lines in a transient network analyzer Trad. 0. (‘I lr/. E/N. Powr~. .S.v.\r. Rcs.. 1000. 12. (2). I I I I I7 Modern transmission systems require adapting old networks to new schemes with major operation flexibility. Frequently. the new opcrntion states may lead the equipment out of the design condition\. This paper shows switching transient studies, carried out over an old system, to improve its performance. The disconnection of one section of the system,

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