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V Curve (v + curve)
Selected AbstractsElectrical performance evaluation of low-concentrating non-imaging photovoltaic concentratorPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2008Tapas K Mallick Abstract Second generation prototype photovoltaic facades of reduced costs incorporating devices with optically concentrating elements (PRIDE) incorporate 6,mm wide ,Saturn' solar cells at the absorber of the dielectric concentrator. The concentrators were made using injection moulding technique with potential to manufacture in large-scale applications. Four different concentrator panels have been experimentally verified at outdoors to identify the non-identical current,voltage (I,V) curves. The I,V curve, fill factor and solar to electrical conversion efficiency of four PRIDE concentrator modules have been evaluated from the 24 manufactured in the ,IDEOCONTE' project. The maximum solar to electrical conversion efficiency and the fill factor of the PRIDE concentrator were 9·1 and 70%, respectively. The mismatch loss of the ,unit concentrators' has been identified that occurred due to the lack of bonding between the concentrator unit and the solar cell and the rear glass. The average power concentration ratio of PRIDE concentrators manufactured by the improved method was 2·10 compared to a similar non-concentrating panel and the optical efficiency of the PRIDE system was 83%. Copyright © 2008 John Wiley & Sons, Ltd. [source] Influence from front contact sheet resistance on extracted diode parameters in CIGS solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2008Ulf Malm Abstract The extraction of one-diode model parameters from a current,voltage (J,V) curve is problematic, since the model is one-dimensional while real devices are indeed three-dimensional. The parameters obtained by fitting the model curve to experimental data depend on how the current is collected, and more specifically the geometry of the contact. This is due to the non-uniform lateral current flow in the window layers, which leads to different parts of the device experiencing different front contact voltage drop, and hence different operating points on the ideal J,V curve. In this work, finite element simulations of three-dimensional contact structures are performed and compared to experimental data on Cu(In,Ga)Se2 -based solar cell devices. It is concluded that the lateral current flow can influence the extracted parameters from the one-diode model significantly if the resistivity of the front contact material is high, or if there is no current collecting grid structure. These types of situations may appear in damp heat-treated cells and module type cells, respectively. Copyright © 2007 John Wiley & Sons, Ltd. [source] Explanation of high solar cell diode factors by nonuniform contact resistancePROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2005A. S. H. van der Heide Abstract The current density,voltage (J,V) curve that characterises the performance of a solar cell is often extra rounded, resulting in reduced efficiency. When fitting to the standard one-dimensional models, it is often found that the rounding cannot be fitted by the series resistance only. In these cases, the diode factor m or the depletion region saturation current density J0DR (depending on the model used) is increased. This behaviour could not be explained so far; this paper discusses if a nonuniform contact resistance of the front side metallisation leads to an increase of m or J0DR. The theoretical part of the investigation is the simulation of the curve for a cell with two regions with different contact resistance. It was found indeed that m or J0DR is increased, while the series resistance is not increased as much as expected. The experimental part was the calculation of the J,V curve of a high- m solar cell with local contact resistances measured with the so-called Corescan and the cell's resistanceless J,V curve as measured with the so-called Suns- Voc method. The calculated curve approximated the actual curve quite well, demonstrating in practice that high diode factors can be explained by nonuniform contact resistance. Copyright © 2004 John Wiley & Sons, Ltd. [source] Performance prediction of concentrator solar cells and modules from dark I,V characteristicsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2003I. Antón The indoor performance of concentrator solar cells and modules at operating conditions is a complex task, owing to the required illumination and temperature conditions, and even more so during extensive procedures, such as on a production line. The solution proposed throughout this paper consists of predicting the illumination I,V characteristic of the solar cells, with the dark I,V curve and the photogenerated current as the only input data. As well as this, the technology-dependent components of the series resistance are obtained from the dark characteristics for quality control. Theory and experiments on several types of concentrator cell have been carried out to validate the method. The equipment to be used on a production line has been developed by IES and used by BP Solar to test up to 25 000 cells and 2000 modules for the 480,kWp power plant using the EUCLIDESTM concentrator. Copyright © 2003 John Wiley & Sons, Ltd. [source] Spot modelling of the flare M4.5 dwarf YZ CMiASTRONOMISCHE NACHRICHTEN, Issue 6 2003M. Zboril Abstract We report on a photometric study of the flareM4.5 dwarf YZ CMi as based on photoelectric observations from the seasons 1972/73, 1979/80 and 1996/97. We suggest spot activity to explain the light and colour curves. Spots are generally 500K cooler than the surrounding photosphere and there are basically two solutions available for the observations: high latitude spot changing slightly basic properties such as radius and latitude or active near-equatorial (belt-like) centers represented by three spots. However, the activity centers changed in longitudes (,180°). The typical spot coverage (inclination i = 60°) is 10-15% and 5% for the season 1996/97 or ,25% for the stellar inclination i = 75°. As a by-product, V curve and (V-I) and (V-K) indexes turn out to be most promising in modelling of M-type stars as far as present calibrations are concerned. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Inhibition of cardiac Na+ current by primaquineBRITISH JOURNAL OF PHARMACOLOGY, Issue 3 2002Gerardo Orta-Salazar The electrophysiological effects of the anti-malarial drug primaquine on cardiac Na+ channels were examined in isolated rat ventricular muscle and myocytes. In isolated ventricular muscle, primaquine produced a dose-dependent and reversible depression of dV/dt during the upstroke of the action potential. In ventricular myocytes, primaquine blocked INa+ in a dose-dependent manner, with a Kd of 8.2 ,M. Primaquine (i) increased the time to peak current, (ii) depressed the slow time constant of INa+ inactivation, and (iii) slowed the fast component for recovery of INa+ from inactivation. Primaquine had no effect on: (i) the shape of the I , V curve, (ii) the reversal potential for Na+, (iii) the steady-state inactivation and gNa+ curves, (iv) the fast time constant of inactivation of INa+, and (v) the slow component of recovery from inactivation. Block of INa+ by primaquine was use-dependent. Data obtained using a post-rest stimulation protocol suggested that there was no closed channel block of Na+ channels by primaquine. These results suggest that primaquine blocks cardiac Na+ channels by binding to open channels and unbinding either when channels move between inactivated states or from an inactivated state to a closed state. Cardiotoxicity observed in patients undergoing malaria therapy with aminoquinolines may therefore be due to block of Na+ channels, with subsequent disturbances of impulse conductance and contractility. British Journal of Pharmacology (2002) 135, 751,763; doi:10.1038/sj.bjp.0704460 [source] Rich Phase Behavior in a Supramolecular Conducting Material Derived from an OrganogelatorADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Josep Puigmartí-Luis Abstract Organic conducting fiber-like materials hold great promise for the development of nanowires that can act as connections in miniature electronic devices, as an alternative to inorganic nanometer scale structures. This article presents a conducting organic tetrathiafulvalene-based supramolecular material which possesses a rich phase behavior with different packing of the molecules in the different forms, evidenced by electron spin resonance (ESR) spectroscopy. The distinct phases of conducting nanofibers can be easily fabricated through the temperature control of their preparation process from a xerogel by doping with iodine vapors. A total of four conducting phases have been identified conclusively using ESR spectroscopy as the key analytical tool. Three of the phases show a good long-term stability and areas in which the I,V curves have ohmic behavior when studied by current sensing (conducting) AFM. They offer promise for applications where electrical nanometer scale connections are required. [source] Characteristic variation of superconducting thin films modified by an atomic force microscopePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2005Hyeong-Gon Kang Abstract Superconducting thin film surfaces were modified in order to test a possibility as a channel of superconducting flux flow transistor (SFFT) by AFM lithography. A conventional lithography method has been employed for superconducting strips which were patterned on LaAlO3 substrates. A region of the strips was selectively oxidized by an AFM probe in the presence of the electric field between the probe and the strip. Then the modified surface was analyzed by AFM, EPMA, and I-V curves. The thickness of the strips increases with the bias voltage as well as the scanning number due to the oxidation. The nonsuperconducting material produced by an AFM lithography process affects the characteristics of SFFT in the flux creep mode of I,V curves. This study represents a dynamic idea to fabricate the superconducting flux flow transistors with nano-channel by the AFM lithography. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Experimental evidence of parasitic shunting in silicon nitride rear surface passivated solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2002Stefan Dauwe Many solar cells incorporating SiNx films as a rear surface passivation scheme have not reached the same high level of cell performance as solar cells incorporating high-temperature-grown silicon dioxide films as a rear surface passivation. In this paper, it is shown by direct comparison of solar cells incorporating the two rear surface passivation schemes, that the performance loss is mainly due to a lower short-circuit current while the open-circuit voltage is equally high. With a solar cell test structure that features a separation of the rear metal contacts from the passivating SiNx films, the loss in short-circuit current can be reduced drastically. Besides a lower short- circuit current, dark I,V curves of SiNx rear surface passivated solar cells exhibit distinct shoulders. The results are explained by parasitic shunting of the induced floating junction (FJ) underneath the SiNx films with the rear metal contacts. The floating junction is caused by the high density of fixed positive charges in the SiNx films. Other two-dimensional effects arising from the injection level dependent SRV of the Si/SiNx interfaces are discussed as well, but, are found to be of minor importance. Pinholes in the SiNx films and optical effects due to a different internal rear surface reflectance can be excluded as a major cause for the performance loss of the SiNx rear surface passivated cells. Copyright © 2002 John Wiley & Sons, Ltd. [source] Determinants of force rise time during isometric contraction of frog muscle fibresTHE JOURNAL OF PHYSIOLOGY, Issue 3 2007K. A. P. Edman Force,velocity (F,V) relationships were determined for single frog muscle fibres during the rise of tetanic contraction. F,V curves obtained using isotonic shortening early in a tetanic contraction were different from those obtained at equivalent times with isovelocity shortening, apparently because changing activation early in the contraction leads, in isovelocity experiments, to changing force and changing series elastic extension. F,V curves obtained with isotonic and with isovelocity shortening are similar if the shortening velocity in the isovelocity trials is corrected for series elastic extension. There is a progressive shift in the scaling of force,velocity curves along the force axis during the course of the tetanic rise, reflecting increasing fibre activation. The time taken for F,V curves to reach the steady-state position was quite variable, ranging from about 50 ms after the onset of contraction (1,3°C) to well over 100 ms in different fibres. The muscle force at a fixed, moderately high shortening velocity relative to the force at this velocity during the tetanic plateau was taken as a measure of muscle activation. The reference velocity used was 60% of the maximum shortening velocity (Vmax) at the tetanic plateau. The estimated value of the fractional activation at 40 ms after the onset of contraction was used as a measure of the rate of activation. The rate of rise of isometric tension in different fibres was correlated with the rate of fibre activation and with Vmax during the plateau of the tetanus. Together differences in rate of activation and in Vmax accounted for 60,80% of the fibre-to-fibre variability in the rate of rise of isometric tension, depending on the measure of the force rise time used. There was not a significant correlation between the rate of fibre activation and Vmax. The steady-state F,V characteristics and the rate at which these characteristics are achieved early in contraction are seemingly independent. A simulation study based on F,V properties and series compliance in frog muscle fibres indicates that if muscle activation were instantaneous, the time taken for force to rise to 50% of the plateau value would be about 60% shorter than that actually measured from living fibres. Thus about 60% of the force rise time is a consequence of the time course of activation processes and about 40% represents time taken to stretch series compliance by activated contractile material. [source] | ||||||||||