Renewable Energy and Power Quality Journal

Journal Information
ISSN / EISSN: 2172038X / 2172038X
Total articles ≅ 3,240

Latest articles in this journal

, , Electrical Engineering Department King Fahd University for Petroleum and Minerals Dhahran. Saudi Arabia
Renewable Energy and Power Quality Journal, Volume 20, pp 827-832; https://doi.org/10.24084/repqj20.449

Abstract:
—Model predictive control (MPC) for multilevel converter has a multi-term cost function that requires high computation burden. In this paper, the deviation terms considered are classified into two categories according to their dependency on the voltage vector or the switching states of the multilevel converter. Subsequently, two approaches to reduce the computation burden are proposed. Mathematical models for the proposed MPC approaches are discussed and analyzed. An experimental platform for a fivelevel T-type multilevel induction drive is used to validate the proposed study. The experimental results show that the proposed approaches have substantially reduced the MPC computation burden compared to the conventional MPC techniques.
Daniel Galeano-Suárez, César Duarte, Jairo Blanco Solano
Renewable Energy and Power Quality Journal, Volume 20, pp 709-712; https://doi.org/10.24084/repqj20.409

Abstract:
This paper proposes a voltage sag estimation approach based on linear machine learning models. The proposed approach estimates the voltage sag profile on distributions systems with limited monitored buses. The approach takes advantage of the priory knowledge about the linearity of the problem to train and compare three linear models: Least Squares (LS), Ridge Regression (RR), and Absolute Shrinkage and Selection Operator (LASSO). The approach is tested on the IEEE-34-bus distribution system, and the performance of models is validated through the Mean Square Error (MSE). The results show that the proposed linear machine learning models capture the internal relationships of the problem and estimate the voltage sag with high accuracy on test data.
R. Rapisarda, Department of Civil Engineering and Architecture (DICAR) University of Catania. Italy, F. Nocera, V. Costanzo, C. Sciuto, R. Caponetto
Renewable Energy and Power Quality Journal, Volume 20, pp 548-553; https://doi.org/10.24084/repqj20.361

Abstract:
One of the main goals of building design is indoor comfort, regardless of its use (residential, educational, institutional, etc…). However, to achieve indoor comfort, buildings require a significant amount of energy. In the last decades, designers and researchers have been studying new strategies to improve buildings’ energy efficiency, with the purpose of mitigating the negative environmental impact caused by heavy energy consumption. Green roofs have been one of the most investigated solutions because of the many thermal benefits they can offer, and amongst these, hydroponic green roofs gained momentum. This study aims to analyse the rooftop temperature reduction provided during the hot months by a hydroponic green roof, compared to a traditional roof slab and an extensive green roof, in order to assess the different performances of these systems. In situ experiments were conducted to collect surface temperature of the roof slab during summer, with and without the hydroponic system, in order to assess the potential temperature reduction, which subsequently affects the heat flow through the roof and therefore the indoor air temperature. The results show a significant decrease in the external surface temperature of the roof compared to the bare roof, but also slightly better performance compared to the extensive green roof. Despite first promising results, the knowledge on hydroponic green roofs performance remains limited and some drawbacks need to be assessed. For these reasons, further in situ testing should be carried out, under different climatic conditions and experimental setups.
V. Jaramillo, Universidad Laica Eloy Alfaro de Mamabí. Ecuador, O. Cabeza, Universidade de La Coruña. Spain
Renewable Energy and Power Quality Journal, Volume 20, pp 795-798; https://doi.org/10.24084/repqj20.440

Abstract:
Solar thermal energy is a type of non-conventional renewable energy (NCRE) that takes advantage of the sun's heat to heat a fluid called heat carrier, then in a heat exchanger it produces steam at high pressure and temperature that generates electricity in a conventional thermal process, this process being of crucial importance since the production of electrical energy on a large scale depends on its efficiency. The technology chosen here is that of parabolic cylinder thermosolar (PCT), that reflect solar radiation and concentrate it in a tube located in its focal line. Inside it is a thermal fluid heated up to almost 400 ºC. The objective of the present investigation was the thermodynamic modelling of the power cycle of PCT plant that works under a modified Rankin cycle. The research is quantitative in nature since it allowed us to assess how the different thermodynamic processes occur, and it is also non-experimental, descriptive, explanatory and propositional, establishing causal relationships based on secondary sources. The result was a real temperatureentropy diagram (T-S) in which the thermodynamic modelling of the power cycle is represented.
S. Oviedo-Carranza, J.S. Artal-Sevil, J.A. Domínguez-Navarro
Renewable Energy and Power Quality Journal, Volume 20, pp 789-794; https://doi.org/10.24084/repqj20.436

Abstract:
This document describes the application of multiobjective genetic algorithms as techniques and tools to optimize generation and distribution in small microgrids. In this way, genetic algorithms have been used for the allocation of distributed generation to reduce losses and improve the voltage profile. The IEEE14 network has been taken as a study and analysis model. This smart grid has 14 nodes and integrates several generation units, both conventional and renewable, transformers, and multiple loads. In this way, a multi-objective metaheuristic algorithm is proposed with the purpose of planning the power distribution grid based on a series of conditions such as the optimal generation configuration, the minimization of power losses in the lines, power transfer capacity, the reduction of CO2 emissions, and the optimization of the benefits obtained in renewable generation. The overall purpose is the development of an intelligent microgrid management system that is capable of determining the optimal configuration, by estimating demand, energy costs, and operating costs.
Lv. Huixiang, Chen. Caixue, Xiong. Zhigang
Renewable Energy and Power Quality Journal, Volume 20, pp 470-475; https://doi.org/10.24084/repqj20.343

Abstract:
In order to smooth the wind power output, a wavelet packet-double fuzzy control for hybrid energy storage is proposed to smooth the wind power fluctuation. Firstly, the wavelet packet decomposition is used to decompose the wind power output to obtain the grid-connected power signal and the power signal allocated to the hybrid energy storage. Then, the double fuzzy control algorithm is used to optimise the hybrid energy storage SOC to maintain it within a reasonable range, and to make a secondary correction to the hybrid energy storage power allocation, taking into account the charge states of lithium batteries and super capacitors. The results of the analysis show that the proposed method can smooth out the wind power fluctuations while keeping the energy storage SOC within a reasonable range.
V. Ballestín-Bernad, J.S. Artal-Sevil, J.A. Domínguez-Navarro, J.L. Bernal-Agustín
Renewable Energy and Power Quality Journal, Volume 20, pp 833-838; https://doi.org/10.24084/repqj20.450

Abstract:
This paper describes the design of low-cost variablespeed wind turbines by recycling small electrical machines. In this way, electrical machines such as automobile claw-pole alternators, induction motors for domestic applications, or simply electric motors for some industrial applications are studied, considering their reuse as permanent magnet synchronous generators (PMSG) in small wind turbines or hydro-power turbines. The main purpose is the integration of hybrid energy conversion systems (wind and hydraulic turbines) in small stand-alone microgrids within the rural environment. Likewise, in order to optimize the design, the arrangement of the permanent magnets in the rotor is analyzed. The analysis has been carried out using the FluxMotor simulation software, which is based on the 2D finite element method. At the same time, the FEM software provides a lot of information about the optimization of the electrical machine and its multiple design options and topologies. Suggested designs have similar performance as well as a similar size and weight. The purpose has been to explore different topologies and select the most efficient designs. In this way, it is shown that it is possible to reuse an electrical generator easily, without losing much of the general performance.
J.A. Pérez, K.E. Rodríguez, C. Díaz, D.J. Escalante
Renewable Energy and Power Quality Journal, Volume 20, pp 574-578; https://doi.org/10.24084/repqj20.371

Abstract:
Tenerife is one of the main islands of the Canary Islands, which, due to its characteristics as outermost region, has a high energy dependence as well as a limitation on available territory; in addition, as it has been designated as a Remote Area, the elimination of Animal By-Products (ABPs) in landfills is permitted. This treatment does not contribute to the current trend of a circular economy and negatively harms the environment. The energy recovery of this waste through anaerobic digestion to produce biogas would enhance the use of renewable energies, contributing to the meat industry's energy independence and better management of the waste generated by this industry in Tenerife, promoting an energy transition towards cleaner energies. The study of the potential for biomethanization has been carried out both separately and in co-digestion in search of the best biogas production. Of the samples studied, only biogas was obtained in the anaerobic digestion of the rumen content, sewage sludge and for the co-digestion of viscera (cattle, pigs, goats, sheep, and rabbits) with raw blood and sewage sludge. The latter produces 128 mL of biogas per gram of volatile solids (VS) of the mixture, resulting in a total of 4,800 kWhe of electrical energy for Tenerife's estimated waste in 2019.
L.H. Keel, S.P. Bhattacharyya
Renewable Energy and Power Quality Journal, Volume 20, pp 564-568; https://doi.org/10.24084/repqj20.368

Abstract:
A linear time-invariant (LTI) system is usually characterized by its gains, which are ratios of various output and input signal magnitudes. When the main function of the system is energy conversion, one is more interested in the power or energy gain or loss between input and output terminals. Such a "gain" represents the efficiency of the system as an energy conversion device. In this paper, we show that the power or energy "gain" of an LTI system can be determined as a nonlinear function of three signal gains of the system. This results in an explicit formula for the power (energy) gain in terms of the system parameters. This can then be optimized over the design parameters to maximize the gain and thus the system energy efficiency. A detailed DC circuit example is included for illustration. The energy efficiency of an LTI system operating in a steady state in response to a sinusoidal signal is also determined.
Alejandro J. Extremera-Jiménez, Cándido Gutiérrez-Montes, Pedro J. Casanova-Peláez, Fernando Cruz-Peragón
Renewable Energy and Power Quality Journal, Volume 20, pp 735-739; https://doi.org/10.24084/repqj20.418

Abstract:
Ground Thermal Response (TRT) tests are employed to calculate ground thermal characteristics for Ground Heat Exchanger (GHE) design and optimization purposes. There are plenty of 3D models to increase the accuracy of the calculated characteristics, with which the fluid outlet temperature is obtained based on the experimental inlet temperature. To simulate other behaviours not tested in the GHE, it is necessary to correctly simulate the conduct of the fluid inside the test equipment. For this reason, a simple model has been obtained which considers the absorption of heat by the elements of the equipment during an initial time through a variable equivalent heat capacity term and a load factor.
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