1,720,965 research outputs found
A new approach for performance assessment of parallel and non-bottleneck machines in a dynamic job shop environment
No full texturpose: The current study aims to propose a new analytical approach by considering energy consumption (EC), maximum tardiness and completion time as the primary objective functions to assess the performance of parallel, non-bottleneck and multitasking machines operating in dynamic job shops. Design/methodology/approach: An analytical and iterative method is presented to optimize a novel dynamic job shop under technical constraints. The machine’s performance is analyzed by considering the setup energy. An optimization model from initial processing until scheduling and planning is proposed, and data sets consisting of design parameters are fed into the model. Findings: Significant variations of EC and tardiness are observed. The minimum EC was calculated to be 141.5 hp.s when the defined decision variables were constantly increasing. Analysis of the optimum completion time has shown that among all studied methods, first come first served (FCFS), earliest due date (EDD) and shortest processing time (SPT) have resulted in the least completion time with a value of 20 s. Originality/value: Considerable amount of energy can be dissipated when parallel, non-bottleneck and multitasking machines operate in lower-power modes. Additionally, in a dynamic job shop, adjusting the trend and arrangement of decision variables plays a crucial role in enhancing the system’s reliability. Such issues have never caught the attention of scientists for addressing the aforementioned problems. Therefore, with these underlying goals, this paper presents a new approach for evaluating and optimizing the system’s performance, considering different objective functions and technical constraints
Theoretical analysis of wind flow characteristics to investigate the mass and momentum parameters using a novel computational fluid dynamics-based approach
No full textIn this article, an experimental study of a wind turbine in a wind tunnel is performed. The objective has been to present a novel analytical computational fluid dynamics (CFD)-based approach through considering the residual levels of the mass and momentum parameters under effect of different air flow characteristics surrounding the wind turbine, which have an effect on the power losses, turbine’s performance and the economic viability. The involved decision variables are considered to be the wind velocity, the pressure and the turbulence. Evaluation of the convergence showed that the residual level for the maximum method is estimated to be approximately 10–1 to 10–3 times higher than the root mean square. Results also concluded that between two studied turbulence models, the turbulence eddy frequency is found to be more efficient compared with turbulence kinetic energy. In higher iterations compared with the initial iterations, a significant difference between the pressure and the Cartesian velocity components has occurred and the residual level of the velocity components indicated a more efficient convergence compared with the pressure. The overall environmental analysis concluded that on the basis of the CFD residual values, it would be possible to adequately determine the CFD efficiency of the wind energy system in a wind tunnel. It has been demonstrated that, among different decision variables, velocity components of the mass and momentum parameters and the turbulence eddy frequency were determined to produce further accurate results in comparison with the pressure and the turbulence kinetic energy
Design and simulation-based optimisation of a renewable energy system consisting of wind and hydrogen for the purpose of reliable electrification
No full textIn this study, design and simulation-based optimisation of a hybrid power system is investigated. The energy system is designed in such a way that when the electricity is produced from the wind power, it would either be transmitted into the grid for the purpose of medium or large-scale electrification or in the case of surplus electricity, it would be utilised for small-scale hydrogen production. The wind energy production transmitted to the grid is estimated with the optimum value of approximately 2,000 kWh per day. The hybrid energy system has been adjusted so that the incoming energy supplied from wind energy production powers the electrolyser thus producing hydrogen from the power plant. Through considering various ranges of design coefficients including hydrogen price, hydrogen production, electricity price and electricity transmitted to the grid by harnessing the wind power, the net monthly revenues reached a maximum level of € 1,974.87 per month
Technical and economic modelling and evaluation of a water distribution system equipped with an autoclave for industrial production applications
No full textPurpose: The purpose of this paper is to investigate the autoclave-pump pressured water distribution system. Pressured water is used in many manufacturing processes, as a raw material or as a service fluid for different applications. Design/methodology/approach: The performances and the total installation costs of such systems are strongly related to its design and to its decision variables definition. The authors first identify the independent variables (i.e. the decision variables) and the dependent variables of the system and, second, propose a techno-economic mathematical method able to determine its minimum installation cost with an integrated approach. Findings: The trade-off between the autoclave installation costs versus the pump installation costs is demonstrated. A sensitive analysis of the cost of the system as function of its decision variables has been performed to propose a practical graphical analysis tools to proper design the integrated pump-autoclave pressured water distribution system. Originality/value: Many previous researches focus only on the pump system optimization or in the tank system optimization without an integrated approach. The wide utilization in industry of the autoclave-pump pressured water distribution system together with the lack of similar contributions in this area enforces the value of this research
Analytical Approach for Assessing the Layout of Wind Farms
No full textThis study presents a novel analytical approach for the layout and numerical optimization of a wind farm. The objective functions are to maximize the wind farm’s energy production and to minimize the cost of energy. To verify our analysis, a test case study of a 1.5 MW Nordex S77 wind turbine generator (WTG) was considered. The proposed framework consists of two main parts. First, we assessed a simulated wind farm’s layout from the technical and economic perspectives by simultaneously optimizing both the cost of energy and energy production. These parameters were estimated under the effects of two predominant wind directions. Among the proposed layout structures of the wind farm, the optimum values of cost and energy were found to be 5,657 MWh and 7.189 €cents/kWh respectively. Next, two scenarios specifying the decision parameters of the algorithm were considered. An optimization approach was proposed based on an efficient mathematical meta-heuristic methodology known as the firefly algorithm (FA). In this part of our study, a model was developed which evaluates the cost parameter as the main objective function and indicator of the investment cost using the levelized cost of electricity (LCOE). The optimized investment cost for an individual WTG in the wind farm was determined to be €11,388 during the operating period of the power plant using a discount rate of 12%
Techno-economic modelling, analysis and simulation of a water distribution system integrated with pump and autoclave components
No full textWater distribution networks (WDNs), have a complex structure. Their least-cost design and simulation is therefore crucial to convey adequate quantities of water from sources to consumers using the most efficient way. The current research attempts to present an original approach to perform the technical and economic evaluation of a WDN integrated with an autoclave system. For this purpose, a mathematical modelling method is employed to investigate the techno-economic viability of the simulated water system under the effect of the system's design variables. The autoclave's minimum and maximum pressure values as well as the pump flow capacity rates are considered as the free variables of the system and then entered into the proposed analytical model. Afterwards, a tradeoff analysis among the primary components of the system, i.e., pump and autoclave cost has been performed. In the next step, an evaluation on the cost of energy was also carried out to demonstrate the cost variations according to the different pressure values. Results are indicative of the significant changes in the total system cost under the effect of the design variables. In the last stage of this paper, a sensitivity and graphical analysis of the decision variables was also performed to define the input parameters, thus determining the optimum maximum pressure of the autoclave system by which the total cost of the water system is minimized. The technical variables such as the autoclave volume and pump differential head were also investigated during the performed analysis
Techno-economic design of wind farms: A multi-scenario cost-based application
Full text linkWind is a clean source of energy which is spread over wide globe regions. This natural source of energy encourages the planners and stakeholders establishing investments towards installation of wind farms. Wind energy experts are looking through efficient alternatives for the best utilization of the wind energy. Design of wind farms is a fundamental stage of wind energy projects. This study aims to address this issue by considering wind farm design to reduce the levelized cost of the generated wind energy. In the first part of the paper, an analysis of previous research works is carried out to find the latest advancements concerning the design of the wind farm layouts. In the next step, a real application, geo-located in Iran, investigates the effect of different layouts for the wind turbines. A cost approach based on the net present value (NPV) and the levelized cost of energy (LCOE) is used. The results show the optimum positioning of the wind turbines within the site to minimize interferences among the blades maximizing the economic return on the investment
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Towards optimum energy utilization by using the inverters for industrial production
No full textIndustrial machines usually experience considerable energy consumption and alternate production rates, as function of the market demand. These machines are typically equipped with electrical motors used to power the tools required for the manufacturing processes. Large mismatches between the changing production rates and the effective motor speeds can have a significant impact on the energy utilization. In order to variate the electrical motor speed, as function of the market requirements, inverters can be incorporated in industrial systems, increasing flexibility as well as the energy savings. In this study, inverters are employed for converting DC to AC mode in a simulated industrial system. The production rates are modeled using different distribution functions comparing the cases with and without the inverter technology. The investment analysis is developed considering the retrofitting costs of the production systems versus the energy saving. The results of the study demonstrate a comparison model which aims to aid the practitioners and industrial experts during the decision-making process, by considering different production patterns, as input, and returning the system economic feasibility, as output
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