Sep 2014, Volume 8 Issue 3
    

  • Select all
  • RESEARCH ARTICLE
    Ertugrul YILDIRIM

    In this study, the causal relations between inward foreign direct investment (FDI)-energy use per capita and inward FDI-CO2 emission per capita were analyzed and the inconsistency between the causal relations was investigated via bootstrap-corrected panel causality test and cross-correlation analysis. In this direction, data from 76 countries including the period of 1980–2009 was processed. No supportive evidence was found for changing causal relations to country group which was classified into income level. The findings indicated that while the pollution haven hypothesis was supported for Mozambique, United Arab Emirates and Oman, the pollution halo hypothesis was supported in the case of India, Iceland, Panama and Zambia. For other countries, energy use and CO2 emission were neutral to inward FDI flows in aggregated level. Furthermore, this study urged that increased (decreased) energy use due to the inward FDI flows did not necessarily mean an increase (decrease) in pollution level, and vice versa. For policy purpose, FDI attractive policy should be regulated by taking into account this possibility.

  • RESEARCH ARTICLE
    K. MURALI,T. JAYABARATHI

    This paper proposes application of a catfish particle swarm optimization (PSO) algorithm to economic dispatch (ED) problems. The ED problems considered in this paper include valve-point loading effect, power balance constraints, and generator limits. The conventional PSO and catfish PSO algorithms are applied to three different test systems and the solutions obtained are compared with each other and with those reported in literature. The comparison of solutions shows that catfish PSO outperforms the conventional PSO and other methods in terms of solution quality though there is a slight increase in computational time.

  • RESEARCH ARTICLE
    Roozbeh MORSALI,Tohid JAFARI,Amirhossein GHODS,Mohammad KARIMI

    In this context, a novel structure was proposed for improving harmony search (HS) algorithm to solve the unit comment (UC) problem. The HS algorithm obtained optimal solution for defined objective function by improvising, updating and checking operators. In the proposed improved self-adaptive HS (SGHS) algorithm, two important control parameters were adjusted to reach better solution from the simple HS algorithm. The objective function of this study consisted of operation, start-up and shut-down costs. To confirm the effectiveness, the SGHS algorithm was tested on systems with 10, 20, 40 and 60 generating units, and the obtained results were compared with those of the simple HS algorithm and other related works.

  • RESEARCH ARTICLE
    Kallol ROY,Kamal Krishna MANDAL

    In this paper, a hybrid optimization algorithm is proposed for modeling and managing the micro grid (MG) system. The management of distributed energy sources with MG is a multi-objective problem which consists of wind turbine (WT), photovoltaic (PV) array, fuel cell (FC), micro turbine (MT) and diesel generator (DG). Because, perfect economic model of energy source of the MG units are needed to describe the operating cost of the output power generated, the objective of the hybrid model is to minimize the fuel cost of the MG sources such as FC, MT and DG. The problem formulation takes into consideration the optimal configuration of the MG at a minimum fuel cost, operation and maintenance costs as well as emissions reduction. Here, the hybrid algorithm is obtained as artificial bee colony (ABC) algorithm, which is used in two stages. The first stage of the ABC gets the optimal MG configuration at a minimum fuel cost for the required load demand. From the minimized fuel cost functions, the operation and maintenance cost as well as the emission is reduced using the second stage of the ABC. The proposed method is implemented in the Matlab/Simulink platform and its effectiveness is analyzed by comparing with existing techniques. The comparison demonstrates the superiority of the proposed approach and confirms its potential to solve the problem.

  • RESEARCH ARTICLE
    He TAO,Wenqi ZHONG,Baosheng JIN

    Ellipsoidal particles flowing in the hopper were simulated by using the discrete element method (DEM), and described by the multi-element method. The contact detection algorithm and equations for ellipsoidal particle motion in hopper were developed. And the simulation results were confirmed by experiment. Additionally, the mass flow rate, pressure distribution and velocity distribution of two kinds of particles were examined. The results show that the mass flow rate of ellipsoidal particles is smaller than that of spherical particles. There is a maximum value of pressure drop at the top of the junction. Besides, the pressure drop decreases with the discharging time increasing. The velocity of spherical particle is larger than that of ellipsoidal.

  • RESEARCH ARTICLE
    Fidelis I. ABAM, Olayinka S. OHUNAKIN, Bethrand N. NWANKWOJIKE, Ekwe B. EKWE

    In this paper, the end-use efficiencies of the different energy carriers and the overall energy efficiency in the Nigerian residential sector (NRS) were estimated using energy and exergy analysis. The energy and exergy flows were considered from 2006 to 2011. The overall energy efficiency ranges from 19.15% in 2006 to 20.19% in 2011 with a mean of (19.96±0.23)% while the overall exergy efficiency ranges from 4.34% in 2006 to 4.40% in 2011 with a mean of (4.31±0.059)%. The energy and exergy efficiency margin was 15.58% with a marginal improvement of 0.07% and 0.02%, respectively when compared with previous results. The contribution of the energy carriers to the total energy and exergy inputs were 1.45% and 1.43% for electricity, 1.95% and 3% for fossil fuel and 96.6% and 95.57% for bio-fuel. The result shows that approximately 65% of the residence use wood and biomass for domestic cooking and heating, and only a fraction of the residence have access to electricity. LPG was found to be the most efficient while kerosene, charcoal, wood and other biomass the least in this order. Electricity utilization exergy efficiency is affected by vapor-compression air conditioning application apart from low potential energy applications. In addition, this paper has suggested alternatives in the end-use application and has demonstrated the relevance of exergy analysis in enhancing sustainable energy policies and management and improved integration techniques.

  • RESEARCH ARTICLE
    M. BENADJA,S. SAAD,A. BELHAMRA

    This paper deals with the analysis and control of a photovoltaic (PV) system connected to the main supply through a Boost converter and shunt active filter supplied by a PV system providing continuous supply of nonlinear load in variation. A robust control of a PV system connected to the grid while feeding a variable nonlinear load is developed and highlighted. This development is based on the control of the Boost converter to extract the maximum power from the PV system using the Perturb and Observe (P and O) algorithm in the presence of temperature and illumination. The proposed modeling and control strategy provide power to the variable nonlinear load and facilitates the transfer of power from solar panel to the grid while improving the quality of energy (harmonic currents compensation, power factor compensation and dc bus voltage regulation). Validation of the developed model and control strategy is conducted using power system simulator Sim-Power System Blockset Matlab/Simulink. To demonstrate the effectiveness of the shunt active filter to load changes, the method of instantaneous power (pq theory) is used to identify harmonic currents. The obtained results show an accurate extraction of harmonic currents and perfect compensation of both reactive power and harmonic currents with a lower THD and in accordance with the IEEE-519 standard.

  • RESEARCH ARTICLE
    Youcef BEKAKRA,Djilani BEN ATTOUS

    This paper proposes an indirect power control of doubly fed induction generator (DFIG) with the rotor connected to the electric grid through a back-to-back pulse width modulation (PWM) converter for variable speed wind power generation. Appropriate state space model of the DFIG is deduced. An original control strategy based on a variable structure control theory, also called sliding mode control, is applied to achieve the control of the active and reactive power exchanged between the stator of the DFIG and the grid. A proportional-integral-(PI) controller is used to keep the DC-link voltage constant for a back-to-back PWM converter. Simulations are conducted for validation of the digital controller operation using Matlab/Simulink software.

  • RESEARCH ARTICLE
    Ali ARIF,Abderrazak GUETTAF,Ahmed Chaouki MEGHERBI,Said BENRAMACHE,Fateh BENC HABANE

    This paper considered the implementation of a current control method for switched reluctance motors (SRMs) and presented a novel approach to the accurate online modeling of a three phase 6/4 SRM drive. A three phase 6/4 SRM is given theoretical calculation of inductance of the SRM model. The SRM was then tested in a Matlab/Simulink environment and numerically analyzed by using nonlinear 2D look-up tables created from its calculated flux linkage and static torque data. The simulation studied the hysteresis and voltage control strategies. The ideal waveform of stator current under the voltage-current condition and improved shape of rotor were proposed.

  • RESEARCH ARTICLE
    P. RAJA,N. KUMARESAN,M. SUBBIAH

    It is proposed that a capacitor can be connected permanently across each phase winding of a three-phase induction motor along with the conventional delta-star switching, for further saving in VARh at reduced loads on the motor. The method of choosing a suitable value for the capacitor and the criteria to be adopted for calculating the power output at which the star to delta switching is to be made are also explained. The experimental results on a 3-phase, 4-pole, 415 V, 50 Hz, 3.3 kW induction motor verify the advantages in adding the capacitor to the phase winding of the motor. Compared to using only a single delta connected stator winding or a delta-star switching, the advantages of the proposed addition of a capacitor, are also demonstrated through a case study conducted on a 400 V, 250 kW motor. Any further improvement in grid side power factor can be achieved by employing a static synchronous compensator (STATCOM) of reduced VAR rating.

  • RESEARCH ARTICLE
    Azzouz TAMAARAT,Abdelhamid BENAKCHA

    Due to several factors, wind energy becomes an essential type of electricity generation. The share of this type of energy in the network is becoming increasingly important. The objective of this work is to present the modeling and control strategy of a grid connected wind power generation scheme using a doubly fed induction generator (DFIG) driven by the rotor. This paper is to present the complete modeling and simulation of a wind turbine driven DFIG in the second mode of operating (the wind turbine pitch control is deactivated). It will introduce the vector control, which makes it possible to control independently the active and reactive power exchanged between the stator of the generator and the grid, based on vector control concept (with stator flux or voltage orientation) with classical PI controllers. Various simulation tests are conducted to observe the system behavior and evaluate the performance of the control for some optimization criteria (energy efficiency and the robustness of the control). It is also interesting to play on the quality of electric power by controlling the reactive power exchanged with the grid, which will facilitate making a local correction of power factor.

  • RESEARCH ARTICLE
    Jincheng XING,Youli LI,Jihong LING,Huiyang YU,Liwen WANG

    This paper discussed a comparative study of several state-of-art methods for determining building energy consumption benchmark. A new approach, which combined the idea of “building benchmark” and “operational benchmark” in its rating system, was proposed. A case study was conducted which applied the proposed approach to benchmarking an existing office building in Tianjin. Besides, the calculation of benchmarks of the reference building model and real building model using the rating method in eQUEST was also considered. Furthermore, the simulation results of the reference building model were taken as the baseline to divide real office buildings into different energy performance grades.

  • RESEARCH ARTICLE
    Xuzhan ZHOU,Shanshan LIU,Mingkun WANG,Yiping DAI,Yaohua TANG

    Accurate modeling and parameters of high voltage (HV) grid are critical for stability research of system frequency. In this paper, simulation modeling of the system frequency was conducted of an interconnected power system with HV transmission lines in China. Based on recorded tripping data of the HV transmission lines, system parameters were identified by using genetic algorithm (GA). The favorable agreement between simulation results and recorded data verifies the validity of gird models and the accuracy of system parameters. The results of this paper can provide reference for the stability research of HV power grid.

  • RESEARCH ARTICLE
    Shilei LU,Zhe CAI,Li ZHANG,Yiran LI

    The aim of this study is to evaluate the performance of a centralized open-loop ground-water heat pump (GWHP) system for climate conditioning in Beijing with a cold climate in China. Thus, a long-time test was conducted on a running GWHP system for the heating season from December 2011 to March 2012. The analysis of the testing data indicates that the average heat-pump coefficient of performance (COP) and the COP of the system (COPs) are 4.27 and 2.59. The low value and large fluctuation in the range of COP are found to be caused by the heat transfixion in the aquifer and the bypass in the circulation loop. Therefore, some suggestions are proposed to improve the performance for GWHPs in the cold climate region in China.