Scheduling Maintenance in Wind Farms

International audienc

A MIP Model and Several Approaches to Schedule Maintenance in Wind Farms on a Short-term Horizon

Taking into account wind prediction when scheduling maintenance on wind turbines can lead to potential gains. Preemption, transfer times for resources, and outsourcing are considered in this problem. The objective is concerned with maximizing the difference between the profits of wind farms related to the estimated production and the costs associated with outsourcing and resources transfers. A MIP model, a benders decomposition technique and a constraint programming approach are proposed

A Benders-based branch-and-cut approach to solve a wind turbine maintenance scheduling problem

We deal with a maintenance scheduling problem rising in the onshore wind power industry. We address the problem on a short-term horizon considering an individual management of the technicians through a space-time tracking. The objective is to find a maintenance planning that maximizes the production of the turbines while taking into account wind predictions, multiple task execution modes, and task-technician assignment constraints. We introduce an exact method to solve this challenging problem. We first propose integer linear programming (ILP) formulations of this problem. Then, on this basis, we build up a Benders-based branch-and-cut approach making use of Benders cuts as well as problem-specific cuts. Our method solves to optimality most of the instances or delivers solutions with a small average gap with respect to upper bounds. The results suggest that our method significantly outperforms the direct resolution of ILP models

A branch-and-check approach to solve a short-term maintenance scheduling problem faced by the onshore wind industry

International audienc

Maintenance scheduling in the electricity industry: A literature review

The reliability of the power plants and transmission lines in the electricity industry is crucial for meeting demand. Consequently, timely maintenance plays a major role reducing breakdowns and avoiding expensive production shutdowns. By now, the literature contains a sound body of work focused on improving decision making in generating units and transmission lines maintenance scheduling. The purpose of this paper is to review that literature. We update previous surveys and provide a more global view of the problem: we study both regulated and deregulated power systems and explore some important features such as network considerations, fuel management, and data uncertainty

Variability of earthworm's functional traits in eastern Amazon is more species-dependent than environment-dependent

Understanding the causes of variability in functional traits is an important question in earthworm ecology. While interspecific variation in anatomical dimensions for the same trait is well accepted, the role of environmental filters, soil degradation, and environmental stress in affecting the variability of functional traits is not well understood. In this study, we sought to determine the relative importance of environmental factors and earthworm species taxonomy on the variability in functional traits within species (intraspecific variability). We focused on eight functional traits including body mass, body length, body diameter, gizzard, gizzard thickness, septum thickness, typhlosole, and gut organic matter. We sampled earthworms of 11 different species in various regions of the eastern Amazon to determine the general responses of different species' characteristics when exposed to various ecosystem and soil conditions. Our results suggest that the functional traits of earthworms are influenced in different ways by environmental conditions. One set of traits, including body mass, body length, and body diameter, was more constant and independent of environmental variability, while another set, including gizzard diameter and length, gizzard muscle thickness, septum thickness, typhlosole, and intestinal organic matter, was more sensitive. The most affected by different environmental variables was septum thickness. We also examined which environmental factors are most important for trait variability. Our study highlights the importance of considering both environmental factors and taxonomic classification when studying the variability of functional traits within earthworm species. Overall, our results suggest that taxonomic classification alone is a good guide for estimating the major functional traits of earthworms in the Brazilian Amazon, but local conditions can their variability is which is essential for informing conservation efforts and maintaining ecosystem function

Maintenance scheduling in wind farms. GDR-RO - Journée conjointe des groupes de recherche P2LS

GT2L et GOTha sur le thème des problèmes d’optimisation intégrésPrésentation (Diaporama

The PrePack optimization problem

International audienc

Structural, electronic, and magneto-optical properties of YVO3_3

Optical and magneto-optical properties of YVO$_3$ single crystal were studied in FIR, visible, and UV regions. Two structural phase transitions at 75 K and 200 K were observed and established to be of the first and second order, respectively. The lattice has an orthorhombic $Pbnm$ symmetry both above 200 K as well as below 75 K, and is found to be dimerized monoclinic $Pb11$ in between. We identify YVO$_3$ as a Mott-Hubbard insulator with the optical gap of 1.6 eV. The electronic excitations in the visible spectrum are determined by three $d$-bands at 1.8, 2.4, and 3.3 eV, followed by the charge-transfer transitions at about 4 eV. The observed structure is in good agreement with LSDA+$U$ band structure calculations. By using ligand field considerations, we assigned these bands to the transitions to the $^4A_{2g}$, $^2E_{g} + ^2T_{1g}$, and $^2T_{2g}$ states. The strong temperature dependence of these bands is in agreement with the formation of orbital order. Despite the small net magnetic moment of 0.01 $\mu_B$ per vanadium, the Kerr effect of the order of $0.01^\circ$ was observed for all three $d$-bands in the magnetically ordered phase $T_{\text{N\'eel}}<116 K$. A surprisingly strong enhancement of the Kerr effect was found below 75 K, reaching a maximum of $0.1^\circ$. The effect is ascribed to the non-vanishing net orbital magnetic moment.Comment: Submitted to Phys. Rev.