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Evaluation of the reliability of solar micro-grids in emerging markets – Issues and solutions
摘要： One of the most important technical features of a power system is its ability to deliver electricity reliably to the customers. Based on interviews with 12 energy service companies (ESCO) currently operating solar micro-grids in northern rural India, this study identified important factors related to technical design, customer behaviour and operations and management (O&M) that may result in contingencies in service. In addition, the study presents companies' innovative solutions to overcome these problems. Initially, the interview method allowed only a rough qualitative comparison of different reliability levels as the availability of comparable data was limited. We found that a more descriptive method for reliability assessment would create equally valuable information on renewable off-grid energy projects. We propose a simple framework for assessing reliability that highlights the particular features of off-grid areas in developing countries.
关键词： Reliability,Micro-grid,Energy systems in developing countries,India,Technical sustainability,Reliability assessment
更新于2025-09-23 15:21:21
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Detecting Water in the Atmosphere of HR 8799 c with <i>L</i> -band High-dispersion Spectroscopy Aided by Adaptive Optics
摘要： High-dispersion spectroscopy of brown dwarfs and exoplanets enables exciting science cases, e.g., mapping surface inhomogeneity and measuring spin rate. Here, we present L-band observations of HR 8799 c using Keck NIRSPEC (R = 15,000) in adaptive optics (AO) mode (NIRSPAO). We search for molecular species (H2O and CH4) in the atmosphere of HR 8799 c with a template-matching method, which involves cross-correlation between reduced spectra and a template spectrum. We detect H2O but not CH4, which suggests disequilibrium chemistry in the atmosphere of HR 8799 c, and this is consistent with previous findings. We conduct planet signal injection simulations to estimate the sensitivity of our AO-aided high-dispersion spectroscopy observations. We conclude that 10?4 contrast can be reached in the L band. The sensitivity is mainly limited by the accuracy of line list used in modeling spectra and detector noise. The latter will be alleviated by the NIRSPEC upgrade.
关键词： planets and satellites: atmospheres,planetary systems,methods: observational,planets and satellites: composition,techniques: spectroscopic,techniques: high angular resolution
更新于2025-09-23 15:21:21
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Theoretical gravity and limb-darkening coefficients for the MOST satellite photometric system
摘要： Aims. We present new calculations of limb and gravity-darkening coe?cients to be used as input in many ?elds of stellar physics such as synthetic light curves of double-lined eclipsing binaries and planetary transits, studies of stellar diameters or line pro?les in rotating stars. Methods. We compute the limb-darkening coe?cients speci?cally for the photometric system of the satellite MOST (Microvariability and Oscillations in STars). All computations were performed by adopting the least-square method, but for completeness we also performed calculations for the linear and bi-parametric approaches by adopting the ?ux conservation method. The passband gravity-darkening coe?cients y(λ) were computed by adopting a more general di?erential equation, which also takes the e?ects of convection into account. Results. We used two stellar atmosphere models: ATLAS (plane-parallel) and PHOENIX (spherical and quasi-spherical). We adopted six laws to describe the speci?c intensity distribution: linear, quadratic, square root, logarithmic, exponential, and a more general one with four terms. The covered ranges of Te?, log g, metallicities, and microturbulent velocities are (1500–50 000 K, 0–5.5, ?5.0–+1.0, 0–8 km s?1), respectively.
关键词： binaries: close,binaries: eclipsing,stars: evolution,stars: atmospheres,planetary systems
更新于2025-09-23 15:21:21
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New constraints on the dust surrounding HR 4796A
摘要： Context.HR 4796A is surrounded by a well-structured and very bright circumstellar disc shaped like an annulus with many interesting features: very sharp inner and outer edges, brightness asymmetries, centre o?set, and suspected distortions in the ring. Aims. We aim to constrain the properties of the dust surrounding the star HR 4796A, in particular the grain size and composition. We also want to con?rm and re?ne the morphological parameters derived from previous scattered light observations, and reveal the dust spatial extent in regions unexplored so far due to their proximity to the star. Methods. We have obtained new images in polarised light of the binary system HR 4796A and B in the Ks and L(cid:3) band with the NaCo instrument at the Very Large Telescope (VLT). In addition, we revisit two archival data sets obtained in the L(cid:3) band with that same instrument and at 2.2 μm with the NICMOS instrument on the Hubble Space Telescope. We analyse these observations with simulations using the radiative transfer code MCFOST to investigate the dust properties. We explore a grid of models with various dust compositions and sizes in a Bayesian approach. Results. We detect the disc in polarised light in the Ks band and reveal for the ?rst time the innermost regions down to 0.3(cid:3)(cid:3) along the semi-minor axis. We measure a polarised fraction of 29% ± 8% in the two disc ansae, with a maximum occurring more than 13? westwards from the ansae. A very pronounced brightness asymmetry between the north-west and south-east side is detected. This contradicts the asymmetry previously reported in all images of the disc in unpolarised light at wavelengths smaller than or equal to 2.2 μm and is inconsistent with the predicted scattered light from spherical grains using the Mie theory. Our modelling suggests the north-west side is most likely inclined towards the Earth, contrary to previous conclusions. It shows that the dust is composed of porous aggregates larger than 1 μm.
关键词： scattering,stars: individual: HR 4796A,planetary systems,instrumentation: polarimeters,instrumentation: high angular resolution
更新于2025-09-23 15:21:21
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The Infrared spectrum of very large (periodic) systems: global versus fragment strategies—the case of three defects in diamond
摘要： The calculation of the full vibrational spectrum (Infrared or Raman) of very large systems (say larger than one thousand atoms) is not only very expensive, but also of relatively low interest, as in many (most of the) cases only a subset of modes, well separated from the large, diffuse bands resulting from the superposition of thousands of peaks, is used for the spectroscopic characterization of the specific system under study. Here, a fragment strategy, consisting in computing and diagonalizing a reduced (in size) Hessian matrix centered around the zone of interest, is illustrated, and its accuracy and efficiency documented, by comparison with the full Hessian diagonalization (FHD) scheme. Three test cases are considered, showing different vibrational features. They are defects in diamond: the VN3 H defect (V stands for the vacancy), where the interesting point is the characterization of the bending and stretching modes of H, well separated from the large band resulting from the perturbation of the diamond manifold; the VH4 defect (four H atoms in the vacancy, with vibrational modes related to H appearing both at high and low wave numbers); and the I2N interstitial defect, with modes in which the N atoms are involved, appearing at wave numbers not far from the manifold of the perfect diamond modes. So the three cases, apparently similar, explore three different situations of interest for the fragment strategy: (1) localized modes very well separated from the large diamond continuous band ( VN3H); (2) modes at upper border of the large diamond continuous band ( I2N ): a case in which the modes of interest appear both as separated from and merged with the large continuous band ( VH4 ). It turns out that in all cases relatively small fragments, containing from 2 to 40 atoms, permit to reproduce with high accuracy (the difference with respect to the FHD being always smaller than 5 cm?1 for the wave numbers, and a few percent for the IR intensity) the spectral feature(s) of interest, at a computational cost that is only a small fraction of the one required by the FHD.
关键词： fragment strategy,vibrational modes,large systems,Infrared spectrum,diamond defects
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - A Method for Uniform Embedment and Self-Assembly of CIS-based QDs for Formation of Ordered QD Thin Films in PV Devices
摘要： GillesPy is an open-source Python package for model construction and simulation of stochastic biochemical systems. GillesPy consists of a Python framework for model building and an interface to the StochKit2 suite of efficient simulation algorithms based on the Gillespie stochastic simulation algorithms. To enable intuitive model construction and seamless integration into the scientific Python stack, we present an easy-to-understand action-oriented programming interface. Here, we describe the components of this package and provide a detailed example relevant to the computational biology community.
关键词： stochastic systems,systems biology,Biological systems,open-source software
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE PES Innovative Smart Grid Technologies Conference - Latin America (ISGT Latin America) - Gramado, Brazil (2019.9.15-2019.9.18)] 2019 IEEE PES Innovative Smart Grid Technologies Conference - Latin America (ISGT Latin America) - Power Flow Analysis on Networks with High Integration of Distributed Photovoltaic Generation
摘要： This article proposes the use of a controlled current source as a photovoltaic generator, due the fact that recent work shows that this choice provides faster processing speed and agile implementation to obtain the power ?ow. This phasorial analysis will be tested using, with some considerations, the 13-Node Test Feeder topology and its input data. Initially, no distributed generation will be considered connected to the feeder and, for a second analysis, photovoltaic distributed generation will be inserted in the system to perform the power ?ow calculation with the proposed model. The reference simulator will be the Knowledge’s Virtual Academy (KVA), because it is a free-access software with a high-level solver to perform the numerical calculation. While the proposed methodology will be implemented in the sotfware Matlab. This study compares and analyze the voltage magnitude, mainly, and angle values obtained for both methods, the KVA result and the proposed method, for the scenarios with and without distributed generation.
关键词： Photovoltaic systems,Electric power systems,Computational system,Power ?ow
更新于2025-09-23 15:21:01
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Behavior of Specialty Optical Fibers in Crude Oil Environment
摘要： Models of biochemical reaction networks commonly contain a large number of parameters, while at the same time, there is only a limited amount of (noisy) data available for their estimation. As such, the values of many parameters are not well known as nominal parameter values have to be determined from the open scienti?c literature and a signi?cant number of the values may have been derived in different cell types or organisms than that which is modeled. There clearly is a need to estimate at least some of the parameter values from experimental data; however, the small amount of available data and the large number of parameters commonly found in these types of models require the use of regularization techniques to avoid over?tting. A tutorial of regularization techniques, including parameter set selection, precedes a case study of estimating parameters in a signal transduction network. Cross-validation results rather than ?tting results are presented to further emphasize the need for models that generalize well to new data instead of simply ?tting the current data.
关键词： parameter estimation,Computational systems biology,nonlinear dynamical systems
更新于2025-09-23 15:21:01
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Dynamic life cycle economic and environmental assessment of residential solar photovoltaic systems
摘要： With the increasing implementation of solar photovoltaic (PV) systems, comprehensive methods and tools are required to dynamically assess their economic and environmental costs and benefits under varied spatial and temporal contexts. This study integrated system dynamics modeling with life cycle assessment and life cycle cost assessment to evaluate the cumulative energy demand, carbon footprint, water footprint, and life cycle cost of residential grid-connected (GC) and standalone (SA) solar PV systems. The system dynamics model was specifically used for simulating the hourly solar energy generation, use, and storage during the use phase of the solar PVs. The modeling framework was then applied to a residential prototype house in Boston, MA to investigate various PV panel and battery sizing scenarios. When the SA design is under consideration, the maximum life cycle economic saving can be achieved with 20 panels with no battery in the prototype house, which increases the life cycle economic savings by 511.6% as compared to a baseline system sized based upon the engineering rule-of-thumb (40 panels and 40 batteries), yet decreases the demand met by 55.7%. However, the optimized environmental performance was achieved with significantly larger panel (up to 300 units) and battery (up to 320 units) sizes. These optimized configurations increase the life cycle environmental savings of the baseline system by up to 64.6%, but significantly decrease the life cycle economic saving by up to 6868.4%. There is a clear environmental and economic tradeoff when sizing the SA systems. When the GC system design is under consideration, both the economic and environmental benefits are the highest when no battery is installed, and the benefits increase with the increase of panel size. However, when policy constraints such as limitations/caps of grid sell are in place, tradeoffs would present as whether or not to install batteries for excess energy storage.
关键词： Grid-connected and standalone PV systems,Life cycle costing,System dynamics modeling,Battery storage,Solar photovoltaic systems,Life cycle assessment
更新于2025-09-23 15:21:01
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Manipulating disordered plasmonic systems by external cavity with transition from broadband absorption to reconfigurable reflection
摘要： Disordered biostructures are ubiquitous in nature, usually generating white or black colours due to their broadband optical response and robustness to perturbations. Through judicious design, disordered nanostructures have been realised in artificial systems, with unique properties for light localisation, photon transportation and energy harvesting. On the other hand, the tunability of disordered systems with a broadband response has been scarcely explored. Here, we achieve the controlled manipulation of disordered plasmonic systems, realising the transition from broadband absorption to tunable reflection through deterministic control of the coupling to an external cavity. Starting from a generalised model, we realise disordered systems composed of plasmonic nanoclusters that either operate as a broadband absorber or with a reconfigurable reflection band throughout the visible. Not limited to its significance for the further understanding of the physics of disorder, our disordered plasmonic system provides a novel platform for various practical application such as structural colour patterning.
关键词： broadband absorption,external cavity,disordered plasmonic systems,tunable reflection,structural colour patterning
更新于2025-09-23 15:21:01