Results 1 - 10 of 594
Results 1 - 10 of 594. Search took: 0.021 seconds
|Sort by: date | relevance|
[en] The influence of real operating conditions of the solar modules (solar radiation intensity, ambient temperature, wind speed) on their output performances is analyzed. An analytical expression is proposed, allowing to approximate the temperature of the solar modules. An algorithm for assessing the operating power of solar modules based on their data sheet information has been developed. The MatLab-Simulink simulation has shown that the identification of ambient and solar module temperatures leads to errors of up to 20 percent in estimating the operating power of solar modules
[en] Decentralized control of DC microgrid (dcµG) using hybrid renewable energy sources (RES) and battery energy storage system (BESS) which operate with and without grid-connected mode is proposed in this paper. In dcµG integrated with multiple RES and BESS, fluctuating output characteristics of the distributed generations (DGs) due to changing input conditions and the dynamic interactions of the source and load interface converters are main factors which cause stability problem of DC bus voltage. Thus, to solve this problem, the decentralized control scheme which uses bus voltage level as communication link in the control law is proposed in this paper. Accordingly, the control method realizes different operating modes based on the available generations and load demand. Maximum power and constant voltage controls schemes are applied in the DGs interfacing control to regulate the power and voltage variations due to changing input conditions. Furthermore, in the control strategy, the source and battery interfacing converters are controlled autonomously using the bus voltage level without any communication. This maintains the reliability and flexibility of the system. The proposed system model is developed with Matlab/Simulink SimPowerSystem and simulated with real-time simulation using OPAL-RT.
[en] A method for controlling the power of an autonomous photoelectric power plant located on the roof of the second building of the Institute of Power and Electrical Engineering of National Polytechnic University of Armenia is investigated. Based on the proposed method, a universal hardware-software means has been developed which allows to increase the value of the maximum power of the photoelectric power plant by 10 percent
[en] Numerical modeling of heat exchange during water flow in a porous medium In this work we present numerical modeling of water flow in a porous medium, heat conduction in water and medium and their mutual heat exchange. It is a numerical approximation of the solution of a system of three differential equations, the first of which, the flow of water in a porous medium, is strongly nonlinear and degenerate, but independent of the rest. The second, heat conduction in water, is strongly dependent on the previous one and is related to the third equation of heat conduction in the environment. In short, we describe the individual methods used to derive equations and the calculation algorithm. The work is a continuation of last year's work Transport of heat and water in a porous environment. The extension includes a specification of the dispersion coefficient and proof of the existence of a solution. An important benefit of this work is the design of a model to determine the heat transfer coefficient between water and porous media, because it is technically impossible to measure at a given point separately the temperature of the environment and water in the pores. (authors)
[en] Energy is the engine of development and prosperity. All countries need to secure sufficient energy to drive economic growth while working to mitigate the effects of climate change. Renewable sources of energy such as wind and solar power will play an important role in the future. At the same time, use of nuclear power will need to increase to provide the steady supply of baseload electricity. As one of the lowest-carbon technologies for generating electricity, nuclear power will also help countries meet their goals of reducing greenhouse gas emissions. This edition of the IAEA Bulletin, published for the International Ministerial Conference on Nuclear Power in the 21st Century, covers some of the most relevant topics on nuclear power and its role in contributing to sustainable development.
[en] This paper addresses the implementation of an advanced twin extremity chaotic map adaptive particle swarm optimization (TECM-PSO) algorithm to the nonlinear congestion management cost problem in deregulated power system. The goal of proposed approach is twofold: firstly, to identify accurate number of participating generators for rescheduling process using a robust upstream real capacity tracing method requiring less information of generator units, and secondly, to achieve minimum possible rescheduled generation cost function using TECM-PSO algorithm while alleviating all the line overloads. Further to preserve the diversity of the algorithm and to increase its near-global searching capability, the incursion of dynamic constraint handling has also been done in the algorithm to retrieve the feasible solutions in the search space. The objective function is solved for near-global optima by step-by-step execution of the proposed algorithm. Twin extremity chaotic maps have been generated by updating the equations governing the PSO algorithm in order to prevent the particle swarm optimization plugging into local minima with less convergence rate at later stages of iterations. The feasibility of the proposed algorithm is validated on various line outage cases of both the small and large test systems, namely modified IEEE 30-, IEEE 57- and IEEE 118-bus systems. Simulation results show a considerable reduction in net rescheduled generation cost, power losses and rescheduled generation amount, ensuring more secure and reliable operation of power system.
[en] Electron impact excitation cross sections from the ground state to the individual magnetic sublevels of 1s2p3,1P1 states in high-temperature dense plasmas are calculated for highly charged He-like Fe24+ions by using a fully relativistic distorted-wave method. The Debye-HEUckel screening model is used to screen the projectile electron from the nucleus and target electrons. The linear polarization degrees for these lines are obtained. It is found that the cross sections at all incident energies decrease with the increase of the screening for these excitations. The influence of screening on linear polarization degrees of the 1P1 line is very small. The linear polarization degrees of 3P1 line decrease sharply at low incident energy with the increase of the screening. (authors)
[en] Aiming at generating electric energy and producing fresh water, the marine nuclear power platform (MNPP) provides support for the national energy strategy. Considering the coupling effect between steam condensation and nature convection, a three-dimensional condensation heat transfer/one-dimensional natural circulation coupling numerical method was developed to analyze the passive compartment cooling system (PCCS) operating performance. Using Fluent and UDF codes, models of PCCS heat exchanging process between the two sides of heat transfer tubes were established. Then the major thermal-hydraulic parameter responses of PCCS were obtained. The results show that when PCCS working, the steam can condense effectively, and both the temperature and pressure in reactor compartment decrease. The analysis method can provide guidance for MNPP PCCS design. (authors)
[en] Highlights: • By considering the modified boundary conditions, the instability of a NEMS electrostatic actuator in precense of Casimir force, and surface energy, is extensively studied. • The potential energy principle is applied in order to satisfy the equilibrium state in structures subjected to static loading. • To solve the nonlinear fourth-order boundary value problem, the Duan–Rach method of determined coefficients (MDC) is applied. The influence of the surface energy on the instability of nano-structures under the electrostatic force has been investigated in recent years by different researchers. It appears that in all prior research, the response of all structures becomes softer due to the surface effects. In the present study, the pull-in instability of a NEMS device incorporating the electrostatic force and Casimir intermolecular attraction for different values of the surface parameter is investigated by the Duan–Rach method of determined coefficients (MDC) in order to identify the remarkable effect of the surface energy. Although the obtained results verify the behavior of such structures in presence of the fringing field and the Casimir attraction same as the previous investigations, however the incremental effects of the surface energy cause the aforementioned structures to behave more stiffly in contrast.
[en] The transformation of the global energy supply is taking place primarily in the accelerated growth dynamics of the increasing share of renewable energies for power generation. In the last decade, renewable energies accounted for more than 60% of the total investments made worldwide in power generation each year. The capacity of power generation plants based on solar, wind, hydro, bio, geothermal and ocean energy more than doubled between the end of 2010 and the end of 2019 - favored by government subsidies and a strong cost degression. In the course of this development, the share of renewable energies in global electricity generation has steadily increased and reached a new record level of 26.0 % in 2019. This means that renewable energies are now - after coal - the second most important source of energy for electricity supply.
[de]Die Transformation der globalen Energieversorgung findet vor allem in der beschleunigten Wachstumsdynamik beim Ausbau erneuerbarer Energien zur Stromerzeugung statt. Auf erneuerbare Energien entfielen im letzten Jahrzehnt jedes Jahr über 60 % der gesamten Investitionen, die weltweit in der Stromerzeugung getätigt wurden. Die Kapazität der Stromerzeugungsanlagen auf Basis von Sonne, Windenergie, Wasserkraft, Bioenergie, Geothermie und Meeresenergie hat sich von Ende 2010 bis Ende 2019 - begünstigt durch staatliche Förderung und eine starke Kostendegression - mehr als verdoppelt. Im Zuge dieser Entwicklung hat sich der Anteil erneuerbarer Energien an der globalen Stromerzeugungsmenge stetig erhöht und 2019 einen neuen Rekordstand von 26,0 % erreicht. Damit sind erneuerbare Energien inzwischen - hinter Kohle - die zweitwichtigste Energiequelle zur Stromversorgung.