Journal of Power and Energy Engineering最新文献

{"title":"Conjugate Heat Transfer Predictions of Gas Turbine Hot Walls Jets Cooling: Influence of Short Hole Grid Resolutions Using Computational Fluid Dynamics*","authors":"Abubakar M. El-Jummah, Shehu A. Abdulrahman, Alhaji S. Grema","doi":"10.4236/jpee.2023.1110001","DOIUrl":"https://doi.org/10.4236/jpee.2023.1110001","url":null,"abstract":"Short hole investigations relevant to gas turbine (GT) hot walls cooling heat transfer techniques, were carried out using computational fluid dynamics (CFD) combined with conjugate heat transfer (CHT) code. The CFD software are commercial ones: ICEM for grid modelling and ANSYS Fluent for the numerical calculation, where symmetrical application prevails. The CFD CHT predictions were undertaken for Nimonic-75 metal walls with square (152.4 mm) arrays of 10 holes, whereby the lumped heat capacitance method was applied in order to determine the surface average heat transfer coefficient (HTC), h (W/m2 K) and the dimensionless Nusselt number, Nu. The major parameters considered for the short hole geometries are the pitch to diameter, X/D and length to diameter, L/D ratios and both were varied with range of D values, but X of 15.24 mm and L of 6.35 mm kept constant. Also applied, are variable mass flux, G (kg/s∙m2) and were used in predicting the flow aerodynamics in the short holes. The predictions were for classic thermal entry length into a round hole, as vena contracta, flow separation and reattachment dominates the holes, hence the development of thermal profile through the depth of the GT hot walls. Additionally, the acceleration of the flow along the wall surfaces as it approaches the holes, was a significant part of the overall heat transfer. This was shown to be independent of the hole length, even though the L/D parameter is a critical component to enhanced heat transfer. The CFD CHT predictions showed that validation of the HTC h, Nu and pressure loss, ∆P are in better agreement with measured data and within reasonable acceptance. The ∆P agreement signifies that the aerodynamics were predicted correctly, which is also the reason why the HTC expressed per wall hole approach surface area and Nu were better predicted. This illustrates how effective and efficient the wall internal heat transfer cooling is for gas turbine hot wall heat transfer using airflow jets cooling.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135559758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of the Implementation of Energy Conservation Opportunities Arising from Energy Audits; A Study of Four-Star and Five-Star Hotels in Nairobi Kenya","authors":"Nicholas Ogola, Peter Musau, Cyrus Wekesa","doi":"10.4236/jpee.2023.119002","DOIUrl":"https://doi.org/10.4236/jpee.2023.119002","url":null,"abstract":"This study assesses the implementation of energy conservation opportunities in four-star and five-star hotels in Nairobi. The Covid-19 pandemic had a significant impact on the Hospitality Industry. Currently, there is a growing inclination to furnish guests with superior and sustainable services in an energy-efficient and eco-friendly way. Comprehensive research was conducted from energy audits gathered from the establishments and contracted auditing companies, on top of this, hotel staff were given digital questionnaires. To add to the data, the researcher surveyed the hotels with engineering managers. The Energy Audits found that all 10 hotels had adopted Energy Conservation Opportunities (ECOs). After further analysis, the mean adoption rate of Energy Conservation Opportunities (ECOs) during the past three years was 55.83%, which was below the aim of 100%. According to studies, hotel staff manages energy to cut costs. The researcher found that hotels use up a lot of energy. However, they have conservation potential, depending on government policies, costs, ease of implementation, and management commitment to sustainable practices. Essentially, Energy Conservation Opportunities (ECOs) reduce energy expenditures and boost reliable revenues, especially during high energy prices and uncertainty.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135699333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new control strategy for SSSC to improve low-frequency oscillations damping","authors":"J. Gholinezhad, M. Ebadian, M. R. Aghaebrahimi","doi":"10.22077/IJPE.2016.510","DOIUrl":"https://doi.org/10.22077/IJPE.2016.510","url":null,"abstract":"When power systems are expanded and connected together with weak tie lines, the low-frequency oscillations are increased and the stability margin of the power system decreases. Therefore, when designing the transmission system to be used, it is necessary to maintain the dynamic stability of the power system, and to make sure to have the most possible stability margin. SSSC is a FACTS device connected in series with power transmission lines. SSSC can control power flow very effectively and can inject series inductive or capacitive voltages into the line. In this paper, a new control strategy based on voltage measurement for the SSSC is proposed. The commonly used strategy for SSSC is based on line current measurement; consequently, the injected voltage is in quadrature with the line current. But in the proposed strategy, the injected voltage is in quadrature with the ac voltage at the point of common coupling (PCC) of SSSC. With modifications done in the proposed strategy, compared with the conventional control method, it can be adjusted easily to control the power flow of the transmission line. The simulation is performed in single-machine and multi-machine power systems. The analysis of the results under different disturbances show that the proposed strategy has an appropriate response with respect to the changes in the system states and it is relatively faster in damping power system oscillations, compared with the conventional strategy.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76572739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Internal Protection of Transformer Windings Against Transeint Surges Using ZnO Varistors","authors":"R. Shariatinasab, Z. Ejtemaee, J. Gholinezhad","doi":"10.22077/IJPE.2016.512","DOIUrl":"https://doi.org/10.22077/IJPE.2016.512","url":null,"abstract":"Power system overvoltages due to switching, lightning and other disturbances are the main problem for designers of the power transformers. Once some frequencies of the incoming surges match with some of the natural frequencies of transformer winding, the resonance phenomenon is expected in transformer winding. The resonant overvoltages may destroy the insulation between turns and cause to insulation failure or transmformer damage. In this paper, the transformer winding is modeled based on the lattice diagram concept with variable parameters and the IEEE model of surge arresters has been utilized in order to perform the simulations.  For internal protection of transformer windings, it is assumed that ZnO varistors are installed in parallel to the winding turns. Also the effect of ZnO varistors in reducing the voltage stress across the transformer winding has been investigated for the case of grounded and insolated nutral winding.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89326753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling of a Rectifier Connected PMSG Applied in Wind Energy Conversion System Using State Machine Approach","authors":"M. Shahnazari, A. Vahedi","doi":"10.22077/IJPE.2016.513","DOIUrl":"https://doi.org/10.22077/IJPE.2016.513","url":null,"abstract":"Accurate modeling of the wind energy conversion system is necessary to design and implementation of the control loop for the generator and the frequency converter, in order to extract maximum power from the wind and to investigate the effects of interconnection between wind farms and power system. In this paper the combination of a permanent magnet synchronous generator loaded with a diode rectifier, used in wind energy conversion system, is modeled using a state machine approach. The model is validated through comparison of the proposed model and the experimental results.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78505115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new interval approach for setting the distance relay zones to achieve perfect selectivity and maximum sensitivity","authors":"A. S. Noughabi, Nader Hatefi Torshizi, H. Najafi","doi":"10.22077/IJPE.2016.514","DOIUrl":"https://doi.org/10.22077/IJPE.2016.514","url":null,"abstract":"In this paper, an interval approach is presented to achieve perfect selectivity and maximum sensitivity in distance relay zones, considering uncertainties. For this purpose, first, the uncertainties affecting the settings of the three zones of a distance relay are discussed. Then, by using the Monte-Carlo simulation, the uncertainties are modelled and the impedances seen by the distance relay are obtained for internal and external faults of the protection zones. Under such conditions, the impedance seen by the relay is modelled as interval impedance for each zone of the relay. With interval impedance being known, an upper and a lower bound are obtained for each zone of the relay. Then, the settings of each zone are determined in such a way that at first, perfect selectivity is achieved between different zones of distance relays and second, the sensitivity of each zone is maximized. The sensitivity and the selectivity of the distance relay zones are defined based on the protection philosophy of these zones. The proposed interval method is applied on a sample 8-bus system, and the advantages of the proposed approach in comparison with conventional methods of setting distance relay zones are shown.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78345793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distributed Generation Effects on Unbalanced Distribution Network Losses Considering Cost and Security Indices","authors":"A. Parizad, A. H. Akhazali, M. Kalantar","doi":"10.22077/IJPE.2016.511","DOIUrl":"https://doi.org/10.22077/IJPE.2016.511","url":null,"abstract":"Due to the increasing interest on renewable sources in recent years, the studies on integration of distributed generation to the power grid have rapidly increased. In order to minimize line losses of power systems, it is crucially important to define the size and location of local generation to be placed. Minimizing the losses in the system would bring two types of saving, in real life, one is capacity saving and the other one is energy saving. In this paper, our aim would be optimal distributed generation allocation for voltage profile improvement and loss reduction in distribution network. Harmony Search algorithm (HSA) was used as the solving tool; the problem is defined and objective function is introduced according to losses, security and cost indices. The applied load flow method is based on the equivalent current injection that uses the bus-injection to branch-current (BIBC) and branch-current to bus-voltage (BCBV) matrices which were developed based on the topological structure of the distribution systems. This method is executed on 13 bus unbalanced distribution system and show robustness of this method in optimal and fast placement of DG, efficiency for improvement of voltage profile, reduction of power losses and cost.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83060942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The New Modeling for MPPT Control of Photovoltaic Cellules","authors":"M. Zandi, A. Payman, J. Martin, S. Pierfederici, B. Davat","doi":"10.22077/IJPE.2016.515","DOIUrl":"https://doi.org/10.22077/IJPE.2016.515","url":null,"abstract":"Consideration of the Current-voltage (I-V) characteristics variations of solar modules with temperature and irradiations variations is basic for maximum power point tracking (MPPT). Having a simple and accurate mathematical model for the optimize utilization of the solar modules is essential. In this paper, a novel modeling of photovoltaic systems with novel coefficients is proposed for mathematical description of the current-voltage (I-V) characteristic. Based on the proposed novel temperature and irradiation coefficients, the mathematical modeling of the solar modules is accurate. The accuracy of this proposed model is evaluated through comparison of simulation results to the data provided by experimental tests. The variations of maximum power point parameters (MPPP) versus irradiation and temperature in the experimental tests and the proposed model is evaluated. The proposed model is as well as adaptable for MPPT control operation.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86048795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of Energy Storage Technologies and Applications Pinpointing Renewable Energy Resources Intermittency Removal","authors":"H. Saboori, S. Dehghan, S. Jadid","doi":"10.22077/IJPE.2016.509","DOIUrl":"https://doi.org/10.22077/IJPE.2016.509","url":null,"abstract":"Renewable energy sources (RES), especially wind power plants, have high priority of promotion in the energy policies worldwide. An increasing share of RES and distributed generation (DG), should, as has been assumed, provide improvement in reliability of electricity delivery to the customers. Paper presented here concentrates on electricity storage systems technologies and applications pinpointing renewable energies variability removal. It can be seen from presented issues that there are numerous options to energy storage systems which can assist in generation and load shifting, peak shaving, transmission expansion planning deferral, ancillary services procurement, and power quality issues. Focus of applications is on renewable resources intermittency elimination. Some related issues including relation between electricity markets and storage systems, system expansion and storage systems, and correlation among smart grid issues and storage systems are also presented. As a result, some comparisons are conducted in terms of various interested criterions in the field of energy storage comprising storage capacity, power level, response time, unit investment and operation costs, round trip efficiency, physical dimensions, cycle life time, life time, availability, and environmental impacts.","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74830193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High voltage gain DC-DC resonant converter","authors":"M. A. Shamsinejad, Reza Zare, Maryam Ramazani","doi":"10.22077/IJPE.2016.482","DOIUrl":"https://doi.org/10.22077/IJPE.2016.482","url":null,"abstract":"","PeriodicalId":16872,"journal":{"name":"Journal of Power and Energy Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78092815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}