Ahmed N.A.,College of Technological Studies |
Ahmed N.A.,Assiut University
IEEE Transactions on Industrial Electronics | Year: 2011
This paper presents a novel high-frequency soft-switching power conversion circuit for high-power induction heating (IH) applications such as the following: 1) heat treatment of metals; 2) hot water; and 3) superheated steam producers. This high-frequency power conversion circuit can operate from single-phase or three-phase systems to produce high current for high-power IH applications under the principles of soft-switching operation. It can regulate its ac output power from the rated value to a low power level. A dual-mode control scheme based on high-frequency pulse width modulation (PWM), in synchronization with the utility frequency positive and negative half-cycles, and pulse density modulation (PDM) is proposed to extend the soft-switching operating range for wide-output power regulation. A dual-pack heat exchanger assembly is designed to be used in consumer and industrial fluid pipeline systems and it is proved to be suitable for hot water, steam, and superheated steam producers. Experimental and simulation results are given to verify the operating principles of the proposed power conversion circuit and to evaluate its power regulation and conversion efficiency. © 2011 IEEE.
AlRashidi M.R.,College of Technological Studies |
EL-Naggar K.M.,College of Technological Studies
Applied Energy | Year: 2010
This paper presents a new method for annual peak load forecasting in electrical power systems. The problem is formulated as an estimation problem and presented in state space form. A particle swarm optimization is employed to minimize the error associated with the estimated model parameters. Actual recorded data from Kuwaiti and Egyptian networks are used to perform this study. Results are reported and compared to those obtained using the well known least error squares estimation technique. The performance of the proposed method is examined and evaluated. Finally, estimated model parameters are used in forecasting the annual peak demands of Kuwait network. © 2009 Elsevier Ltd. All rights reserved.
Fardoun A.A.,United Arab Emirates University |
Ismail E.H.,College of Technological Studies |
Sabzali A.J.,College of Technological Studies |
Al-Saffar M.A.,College of Technological Studies
IEEE Transactions on Power Electronics | Year: 2012
Three new bridgeless single-phase ac-dc power factor correction (PFC) rectifiers based on Cuk topology are proposed. The absence of an input diode bridge and the presence of only two semiconductor switches in the current flowing path during each interval of the switching cycle result in less conduction losses and an improved thermal management compared to the conventional Cuk PFC rectifier. The proposed topologies are designed to work in discontinuous conduction mode (DCM) to achieve almost a unity power factor and low total harmonic distortion of the input current. The DCM operation gives additional advantages such as zero-current turn-ON in the power switches, zero-current turn-OFF in the output diode, and simple control circuitry. Performance comparisons between the proposed and conventional Cuk PFC rectifiers are performed based on circuit simulations. Experimental results for a 150W/48 V dc at 100 V rms line voltage to evaluate the performance of the proposed bridgeless PFC rectifiers are provided. © 1986-2012 IEEE.
Alajmi A.,College of Technological Studies
Energy and Buildings | Year: 2012
The building considered in this case study is a 2-story educational facility with a total floor area of 7020 square meter located in a harsh hot summer climate (State of Kuwait) and served by 4 air-cooled reciprocating chillers. Energy audit techniques were carried out by an energy audit team (EAT) to identify any energy conservation opportunities (ECOs). Level 1 (walk-through assessment) and level 2 (survey and data analysis) audits were conducted over all building zones. These levels of assessments proved that the building and its mechanical and electrical systems were improperly maintained and inefficiently operated. The building assessment produced a list of ECOs classified as non-retrofitting (no or minimal cost) and retrofitting (with cost) recommendations. Interestingly, the non-retrofitting ECOs saved 6.5% of the building's annual energy consumption, while the retrofitting ECOs can save up to 49.3%; this results in a 52% total saving. The savings were calculated using a building simulation software (DesignBuilder). Finally, a cost analysis of the findings was performed; the result showed a pay-back period of less than 6 months for both non-retrofitting and the most effective retrofitting actions. © 2012 Elsevier B.V. All rights reserved.
Mahmoud M.A.,College of Technological Studies
Critical Reviews in Solid State and Materials Sciences | Year: 2016
This article provides a review of methods of predicting mass-induced resonance shifts in microcantilevers. It combines a review of factors that influence resonance frequency shifts, such as material properties, size effects, and support compliance with a comparative study of accuracy of predicting resonance shifts due to mass adsorption. The applicability and accuracy of widely used formulas to correlate mass addition with resonance shift are assessed through comprehensive comparison with experimental measurements and numerical methods. The methods include both distributed parameter and lumped parameter formulations. The applications include distributed added masses, tip masses, and added mass at arbitrary locations along a cantilever span. © 2016 Taylor & Francis Group, LLC.
El-Daou M.K.,College of Technological Studies
Computers and Mathematics with Applications | Year: 2011
We develop a method to solve a class of second-order ordinary differential equations with highly oscillatory solutions. The method consists in combining three different techniques: LegendreGauss spectral Tau method, exponential fitting, and coefficient perturbation methods. With our approach, the resulting approximate solutions are expressed in terms of an exponentially weighted Legendre polynomial basis en<0, where ωn are appropriately chosen complex numbers. The accuracy and efficiency of the method are discussed and illustrated numerically. © 2011 Elsevier Ltd. All rights reserved.
Al-ajmi F.F.,College of Technological Studies
Building and Environment | Year: 2010
In Kuwait, as in most countries with a typical dry desert climate, the summer season is long with a mean daily maximum temperature of 45 °C. Centralized air-conditioning, which is generally deployed from the beginning of April to the end of October, can have tremendous impact on the amount of electrical energy utilized to mechanically control the internal environment in mosque buildings. The indoor air temperature settings for all types of air-conditioned buildings and mosque buildings in particular, are often calculated based on the analytical model of ASHRAE 55-2004 and ISO 7730. However, a field study was conducted in six air-conditioned mosque buildings during the summers of 2007 to investigate indoor climate and prayers thermal comfort in state of Kuwait. The paper presents statistical data about the indoor environmental conditions in Kuwait mosque buildings, together with an analysis of prayer thermal comfort sensations for a total of 140 subjects providing 140 sets of physical measurements and subjective questionnaires were used to collect data. Results show that the neutral temperature (T n) of the prayers is found to be 26.1 °C, while that for PMV is 23.3 °C. Discrepancy of these values is in fact about 2.8 °C higher than those predicted by PMV model. Therefore, thermal comfort temperature in Kuwait cannot directly correlate with ISO 7730 and ASHRAE 55-2004 standards. Findings from this study should be considered when designing air conditioning for mosque buildings. This knowledge can contribute towards the development of future energy-related design codes for Kuwait. © 2010 Elsevier Ltd.
Fardoun A.A.,United Arab Emirates University |
Ismail E.H.,College of Technological Studies
IEEE Transactions on Industry Applications | Year: 2010
In this paper, a new single-switch nonisolated dcdc converter with high voltage transfer gain and reduced semiconductor voltage stress is proposed. The proposed topology utilizes a hybrid switched-capacitor technique for providing a high voltage gain without an extreme switch duty cycle and yet enabling the use of a lower voltage and RDS-ON MOSFET switch so as to reduce cost, switch conduction, and turn-on losses. In addition, the low voltage stress across the diodes allows the use of Schottky rectifiers for alleviating the reverse-recovery current problem, leading to a further reduction in the switching, and conduction losses. The principle of operation and a comparison with other high step-up topologies are presented. Two extensions of the proposed converter are also introduced and discussed. Simulation and experimental results are also presented to demonstrate the effectiveness of the proposed scheme. © 2010 IEEE.
Ahmed N.A.,College of Technological Studies
10th International Power and Energy Conference, IPEC 2012 | Year: 2012
In this paper, development and simulation of an efficient small-scale centralized dc-bus grid connected hybrid wind/photovoltaic/fuel cell for supplying power to a low voltage distribution system are presented. The hybrid system consists of wind and photovoltaic as a primary power system. A fuel cell is added as a secondary system to ensure continuous power supply and to take care of the intermittent nature of wind and photovoltaic. The objective of this study is to design and control a hybrid system that guarantees the energy continuity. A simple control method is applied to the proposed configuration to simultaneously achieve three desired goals: to extract maximum power from each hybrid power system component; to guarantee dc bus voltage regulation at the input of the inverter; and to transfer the total produced power to the grid at unity power factor, while fulfilling all necessary interconnection requirements. The simulation results indicate that the dc-dc converters are very effective in tracking the maximum power of the wind and photovoltaic sources, the fuel cell controller responds efficiently to the deficit power demands. © 2012 IEEE.
Alrashidi M.R.,College of Technological Studies |
Alhajri M.F.,College of Technological Studies
Energy Conversion and Management | Year: 2011
An improved particle swarm optimization algorithm (PSO) is presented for optimal planning of multiple distributed generation sources (DG). This problem can be divided into two sub-problems: the DG optimal size (continuous optimization) and location (discrete optimization) to minimize real power losses. The proposed approach addresses the two sub-problems simultaneously using an enhanced PSO algorithm capable of handling multiple DG planning in a single run. A design of experiment is used to fine tune the proposed approach via proper analysis of PSO parameters interaction. The proposed algorithm treats the problem constraints differently by adopting a radial power flow algorithm to satisfy the equality constraints, i.e. power flows in distribution networks, while the inequality constraints are handled by making use of some of the PSO features. The proposed algorithm was tested on the practical 69-bus power distribution system. Different test cases were considered to validate the proposed approach consistency in detecting optimal or near optimal solution. Results are compared with those of Sequential Quadratic Programming. © 2011 Elsevier Ltd. All rights reserved.