Reliability Analysis of PV Inverters Considering Locational Impact

The inverter system is an important piece of equipment for efficiently absorbing the electricity generated from renewable sources and ensuring reliable grid connections. As power electronics advance, inverter conversion efficiency is improving and photovoltaic (PV) energy is becoming a major contributor to the global supply of renewable energy. However, a key consideration is how reliable the PV inverters are. The dependability performance of PV inverters can be influenced by various environmental parameters, such as solar radiation and temperature (collectively referred to as Mission Profile). Given that these conditions vary by location, it is necessary to take them into account when evaluating the dependability performance of a PV inverter. The Mission Profile, including the local solar radiation and surrounding temperature, are important factors determining the lifespan of a PV inverter. This research examines how environmental variables and geographic position affect the dependability performance of PV converters and finds that these elements have a significant bearing on that performance

Use of reverse cross-polarization for editing solid state proton NMR spectra

We present here the use of the cross-polarization- reverse cross-polarization (CP-RCP) method for editing proton spectra by identifying protons attached exclusively to a nucleus such as carbon or nitrogen. Experiments have been done at moderate spinning speeds utilizing the Combined Rotation and Multi-Pulse Scheme (CRAMPS) technique which provided resolution of the spectral lines that is sufficient for several small molecular systems. This approach, in addition to being an editing tool, helps to increase resolution further and also leads to identifying protons such as the OH and the SH protons. Here we present results of the application of the CP-RCP scheme to systems at natural abundance of the nuclei C-13 and N-15. The utility of the method has been illustrated for the case several amino acids, a tri-peptide and a synthesized cocrystal. (C) 2018 Elsevier B.V. All rights reserved

Photoluminescence and energy transfer studies of YAl3(BO3)(4):Sm3+/Tb3+ phosphors for solid state lighting applications

Trivalent samarium (Sm3+)/terbium (Tb3+) co-doped YAl3(BO3)(4) (YAB) phosphors were prepared by solid-state reaction method. The phase, structure, optical and energy transfer studies were systematically characterized through X-ray diffraction, Fourier transform infrared spectroscopy, photoluminescence (PL) and decay measurements, respectively. Upon 406 nm excitation, both Sm3+ single- and Sm3+/Tb3+ co-doped YAB phosphors emit orange-red luminescence with peak maximum at 602 nm. The YAB:Tb3+ phosphor emits green luminescence at 546 nm when excited with 375 nm near UV wavelength. The YAB:Sm3+/Tb3+ phosphors emit green-to-white luminescence as a function of Sm3+ concentration upon an excitation wavelength of 375 nm. The Tb3+ acts as an efficient sensitizer of luminescence of Sm3+ under 375 nm excitation in YAB phosphors. Doped Sm3+ and Tb3+ ions were located at the inversion symmetry sites of YAB lattice. The Commission International de l'Eclairage chromaticity coordinates were calculated from the PL spectra. The energy transfer from Tb3+ to Sm3+ ions was described in detail. The YAB:Sm3+/Tb3+ phosphors can be used as a promising material for solid state lighting devices

Luminescence and gain characteristics of 1.53 mu m broadband of Er3+ in lead telluroborate glasses

Different concentrations (0.1, 0.5, 1.0 and 2.0 mol%) of Er3+-doped lead telluroborate glasses were prepared by conventional melt quenching method. Up on 514.5 nm laser excitation, the near infrared luminescence due to the I-4(13/2)-> I-4(15/2) transition was analyzed. The absorption and emission spectra were used to determine the different spectroscopic parameters by means of the Judd-Ofelt and the McCumber theories. The obtained Judd-Ofelt intensity parameters were used to obtain the radiative transition probability, fluorescence branching ratio and radiative lifetime of the I-4(13/2) emission state. The effect of Er3+ concentration on the emission intensity of I-4(13/2)-> I-4(15/2) transition was discussed. The Stark-level energies of I-4(13/2) excited and I-4(15/2) ground states were evaluated using both the absorption and emission measurements. The wavelength dependent gain coefficient, G(lambda) of I-4(13/2)-> I-4(15/2) transition of Er3+ ion was determined using the absorption and emission cross-sections. The suitability of this glass as a host for Er3+-doped broad-band amplifiers and its advantage over other glasses were discussed. (C) 2013 Elsevier B.V. All rights reserved

Application of modified Judd-Ofelt theory and the evaluation of radiative properties of Pr3+-doped lead telluroborate glasses for laser applications

Praseodymium doped lead telluroborate (PTBPr) glasses were prepared by conventional melt quenching method. The absorption spectra have been analyzed to evaluate the intensity parameters applying the standard and the modified Judd-Ofelt theories. The emission spectra under P-3(2) level excitation (lambda(ex)=447 nm) were investigated to estimate the laser characteristic parameters. These emission measurements together with Judd-Ofelt intensity parameters (Omega(lambda)=2,4,6) have been used to calculate the radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of the transitions from P-3(0) and D-1(2) levels to their lower lying levels. The quenching of fluorescence intensity and experimental lifetime with the increase of Pr3+ concentration and the shift of D-1(2) -> H-3(4) emission peak towards longer wavelengths was discussed. The non-radiative losses due to multiphonon and energy transfer relaxations were also explained. The Commission Internationale de l'Eclairage (CIE) coordinates, color purity and optical band gap energy values were evaluated. Some of the basic laser characteristics such as stimulated emission cross-section, optical and bandwidth gain parameters and fluorescence quantum efficiency were also reported. (C) 2012 Elsevier B.V. All rights reserved