Hydro-Québec

About: Hydro-Québec is a government organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Electric power system & Dielectric. The organization has 2596 authors who have published 4433 publications receiving 100878 citations.

Modeling and Resolution of the Medium Term Energy Generation Planning Problem for a Large Hydro-Electric System

Abstract: This paper is concerned with the modeling and resolution of the energy generation planning problem of a large hydroelectric system for a horizon up to two years, with emphasis on hydro plant generation, hydro system aggregation, and objective function modeling. The problem has been formulated as a deterministic discrete-time optimal control problem, with linear transition equations, a highly nonlinear objective, and bounds on both the state and the control variables. The solution algorithm is of the reduced gradient type, with the control variables nonbasic to provide good conditioning. Because of the linear relationship between the state and control variables, the set of feasible directions at a point is a polyhedral convex cone and the bounds both on the state and control variables can be accounted for by means of an algorithm for the orthogonal projection of the gradient on the cone. Some computational experience with this large-scale non-linear program is given, followed by a discussion of implementation.

Design and Validation of a Mobile Robot for Power Line Inspection and Maintenance

Abstract: This paper presents the LineScout Technology, a mobile teleoperated robot for power line inspection and maintenance. Optimizing several geometric parameters achieved a compact design that was successfully tested over many line configurations and obstacle sequences. An overview of the technology is presented, including a description of the control strategy, followed by a section focusing on key aspects of the prototype thorough validation. Working on live lines, up to 735 kV and 1,000 A, means that the technology must be robust to electromagnetic interference. The third generation prototype, tested in laboratory and in field conditions, is now ready to undertake inspection pilot projects.

In situ observation of solid electrolyte interphase evolution in a lithium metal battery

Abstract: Lithium metal is a favorable anode material in all-solid Li-polymer batteries because of its high energy density. However, dendrite formation on lithium metal causes safety concerns. Here we obtain images of the Li-metal anode surface during cycling using in situ scanning electron microscopy. Constructing videos from the images enables us to monitor the failure mechanism of the battery. Our results show the formation of dendrites on the edge of the anode and isles of decomposed lithium bis(trifluoromethanesulfonyl)imide on the grain boundaries. Cycling at high rates results in the opening of the grain boundaries and depletion of lithium in the vicinity of the isles. We also observe changes in the surface morphology of the polymer close to the anode edge. Extrusion of lithium from these regions could be evidence of polymer reduction due to a local increase in temperature and thermal runaway assisting in dendrite formation. Dendrite formation on lithium metal anodes jeopardizes the safety of lithium ion batteries. Here the authors use in situ scanning electron microscopy to follow the evolution of dendrites and isles of a conductive salt forming on the anode surface, causing the battery to fault.

High-resolution electron microscopy study of NiMo nanocrystals prepared by high-energy mechanical alloying

Abstract: A growing interest has emerged in the past few years over a new class of materials called “nanocrystalline solids” (NS). These materials are made of extremely small crystals with dimensions ranging from 1 nm to 10 nm. Up to now, most of these solids were fabricated from the gas phase by an evaporation/ condensation process. Recently, however, high energy mechanical alloying (MA) has been shown to be an excellent tool to produce various types of metastable structures, including NS. Through high energy MA we have fabricated nanocrystalline nickel oversaturated with molybdenum which shows an extremely high electrocatalytic activity for the hydrogen evolution reaction in alkaline solutions. In order to fully understand the chemical properties of these new alloys, we have investigated, through high resolution electron microscopy, the microstructure and the size distribution of the crystalline throughout the milling process. A detailed study of the crystalline interfaces and grain boundaries is also presented.