Large-scale unit commitment under uncertainty: an updated literature survey

The Unit Commitment problem in energy management aims at finding the optimal production schedule of a set of generation units, while meeting various system-wide constraints. It has always been a large-scale, non-convex, difficult problem, especially in view of the fact that, due to operational requirements, it has to be solved in an unreasonably small time for its size. Recently, growing renewable energy shares have strongly increased the level of uncertainty in the system, making the (ideal) Unit Commitment model a large-scale, non-convex and uncertain (stochastic, robust, chance-constrained) program. We provide a survey of the literature on methods for the Uncertain Unit Commitment problem, in all its variants. We start with a review of the main contributions on solution methods for the deterministic versions of the problem, focussing on those based on mathematical programming techniques that are more relevant for the uncertain versions of the problem. We then present and categorize the approaches to the latter, while providing entry points to the relevant literature on optimization under uncertainty. This is an updated version of the paper "Large-scale Unit Commitment under uncertainty: a literature survey" that appeared in 4OR 13(2), 115--171 (2015); this version has over 170 more citations, most of which appeared in the last three years, proving how fast the literature on uncertain Unit Commitment evolves, and therefore the interest in this subject

Local regularity analysis of strata heterogeneities from sonic logs

Borehole logs provide geological information about the rocks crossed by the wells. Several properties of rocks can be interpreted in terms of lithology, type and quantity of the fluid filling the pores and fractures. <br><br> Here, the logs are assumed to be nonhomogeneous Brownian motions (nhBms) which are generalized fractional Brownian motions (fBms) indexed by depth-dependent Hurst parameters H(z). Three techniques, the local wavelet approach (LWA), the average-local wavelet approach (ALWA), and Peltier Algorithm (PA), are suggested to estimate the Hurst functions (or the regularity profiles) from the logs. <br><br> First, two synthetic sonic logs with different parameters, shaped by the successive random additions (SRA) algorithm, are used to demonstrate the potential of the proposed methods. The obtained Hurst functions are close to the theoretical Hurst functions. Besides, the transitions between the modeled layers are marked by Hurst values discontinuities. It is also shown that PA leads to the best Hurst value estimations. <br><br> Second, we investigate the multifractional property of sonic logs data recorded at two scientific deep boreholes: the pilot hole VB and the ultra deep main hole HB, drilled for the German Continental Deep Drilling Program (KTB). All the regularity profiles independently obtained for the logs provide a clear correlation with lithology, and from each regularity profile, we derive a similar segmentation in terms of lithological units. The lithological discontinuities (strata' bounds and faults contacts) are located at the local extrema of the Hurst functions. Moreover, the regularity profiles are compared with the KTB estimated porosity logs, showing a significant relation between the local extrema of the Hurst functions and the fluid-filled fractures. The Hurst function may then constitute a tool to characterize underground heterogeneities

Iron and Aluminium Removal from Algerian Silica Sand by Acid Leaching

This work refers to a process of purification of silica sand and, more particularly, to a process of iron and aluminium removal from the Algerian silica sand particles. Iron compounds are among the most difficult impurities to release from the sand particles. Several methods to remove iron from the sand particles are used; in our work we employed the acid leaching process as optimal solution to purify the silica sand. To this purpose, our work began by characterization of sand samples using X-ray fluorescence, for measurement of concentrations of major mineral oxides, and using atomic absorption, to determine the iron and aluminium concentrations in the silica sand particles. Through this study, the samples were enriched by acid leaching method, by removing the impurities from the crystal lattice, as well as from its surface. Thus reduction the impurities concentration increases, at the same time, the SiO₂ concentration. The obtained enriched silica can be used as raw material for silicon production, destined for photovoltaic application

Sand Dune Characterization for Preparing Metallurgical Grade Silicon

Dune sand, from Biskra, Algeria which is in the Great Algerian huge desert attracts tourists from all over the world. Dune sand composes around 80% of the total area of the desert. To date only a few studies have been conducted on this sand. The purpose of the present study is to shed light on the textural and physico-chemical characteristics of this sand using several characterization methods, and to understand the potential for using for photovoltaic applications. The chemical composition of Biskra sand indicated a high purity quartz with 97.6% silica, and a presence of others oxides. Granular analysis enabled the determination of the size of the sand grains which was found to be fine to medium. On the other hand, a Scanning Electron Microscopy and optical observations were carried out, the micrographs observations indicated the presence of different shapes of sand grain, some rounded whereas others are angular edged or elongated. X-ray diffraction indicates the highly crystalline nature of the Biskra sand

3DIP: An iterative partitioning tool for monolithic 3D IC

Conference of 2016 IEEE International 3D Systems Integration Conference, 3DIC 2016 ; Conference Date: 8 November 2016 Through 11 November 2016; Conference Code:129057International audienceCoolCubeTM is a monolithic 3D (M3D) technology offering a vertical density of integration 20 times higher than face to face copper hybrid bonding (F2F Cu-Cu), thanks to ultra-thin Monolithic Inter-tier Vias (MIVs). In this work, we propose a new partitioning tool exploiting this characteristic for 2-tier Cell-on-Cell ICs before placement. It is based on a fast and iterative algorithm that explores the space of solutions and minimizes the estimated cost of wires with balanced area between tiers without limiting the number of MIVs. A mathematical formulation of the 3D partitioning problem and a comprehensive framework, based on simulated annealing (SA) algorithm coupled with a dedicated cost function, are detailed and compared with Min-Cut (MC) partitions commonly used. It appears that our solution can decrease the estimated total cost of wires by 41% and 45% for the LDPC and FFT/AES units. It also reduces the total cost of wires by 30% to 44% compared to the MC algorithm for the same units and with no significant increase in runtime

Valorization of Algerian sand for photovoltaic application

Extracting quartz from sand, as well as extracting silicon from quartz requires knowledge of the physical and chemical properties of quartz found in the sand. In this work the chemical composition, the crystallographic phase, crystal system, space group, unit cell parameters, the absorption bands, the granulometric analysis and the microscopic observations of quartz in the sand from Mostaganem (Algeria) region have been carried out using X-ray fluorescence, X-ray diffraction, infrared spectroscopy, sifting, optical and scanning electron microscopy in order to determine the rate and the nature the crystallinity of its various components and to discover a layer rich in silica, containing a sufficient reserve to feed a unit manufacturing pure silicon starting from silica. The study is driven by current economic importance of the silicon application in the field of photovoltaic solar cells. The X-ray fluorescence indicates that Mostaganem sand has got a very good purity (99.5% silica). The crystallographic parameters of Mostaganem sand have been determined through analysis of X-ray diffraction. The following parameters were found, hexagonal crystal system, space group P3221, unit cell parameters: a=b=4.9030 Å, c=5.3999 Å. The infrared absorption spectrum of studied sand exhibits absorption bands characterizing the SiO₂ compound, due to Si-O-Si and Si-O aggregates and others. The granulometric analysis determines the percentage of the various fraction of the grain. The microscopy observation gives the shape of the grain. The results show finally that Mostaganem sand has got good proprieties for the photovoltaic application

Niobium addition effect in molds at last cooling step on EN-GJL250 gray cast iron: Microstructural changes and electrochemical behavior

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