Sharif Digital Repository

In this research work, a modified fuzzy approach referred to as modified fuzzy logic method (MFLM) is proposed to more conveniently solve intricate decision-making problems under uncertainty and data deficiency. The method resolves major drawbacks like inaccuracy, complexity, and a high volume of computational efforts with the existing approaches for the mentioned problems. Here, MFLM is applied to materials selection for a cryogenic storage tank and a gas turbine blade, which are standard engineering problems used for verification by researchers, and the ranking results are compared with the state-of-the-art techniques in the literature, such as the conventional fuzzy logic method.... 

In distribution networks, failure to smooth the load curve leads to voltage drop and power quality loss. In this regard, electric vehicle batteries can be used to smooth the load curve. However, to persuade vehicle owners to share their vehicle batteries, we must also consider the owners' profits. A challenging problem is that existing methods do not take into account the vehicle owner demands including initial and final states of charge and arrival and departure times of vehicles. Another problem is that battery capacity of each vehicle varies depending on the type of vehicle; which leads to uncertainties in the charging and discharging dynamics of batteries. In this paper, we propose a... 

Hydrogen as an energy carrier can play a significant role in reducing environmental emissions if it is produced from renewable energy resources. This research aims to assess hydrogen production from wind energy considering environmental, economic, and technical aspect for the East Azerbaijan province of Iran. The economic assessment is performed by calculation of payback period, levelized cost of hydrogen, and levelized cost of electricity. Since uncertainty in the power output of wind turbines may affect the payback period, all calculations are performed for four different turbine degradation rates. While it is common in the literature to choose the wind turbine based on a single criterion,... 

Numerical simulation of a dual-swirl gas turbine model combustor is performed under cold and reacting flow conditions using a three-dimensional unsteady Reynolds-averaged Navier-Stokes approach. A multi-species chemical mechanism is used in this study for the analysis of the numerous radicals participating in the ignition process and the flame structure. The other objective of this study is to investigate the flow field under different injector configurations, including both co-rotating and counter-rotating swirler arrangements, different swirl intensities, and vane areas. A comparison of the results with experimental data shows that the predicted velocity and temperature profiles follow the... 

The Under Frequency Load Shedding (UFLS) is the last automated action to restore power system frequency stability when a severe contingency causes a significant drop in the frequency of interconnection or islanded areas. In this paper, a novel probabilistic algorithm that considers the wind turbine frequency response is proposed to design and optimize the UFLS scheme. The uncertainties of power systems such as wind speed, hourly load, inertia time constant, and generation losses are taken into account. The Monte-Carlo Simulation (MCS) method is used to model the power system uncertainties. Additionally, a novel method is developed to calculate the power system frequency response and... 

A transcritical carbon dioxide (T-CO2) cycle is analyzed for waste heat recovery from a gas turbine. The cycle is proposed to produce combined power and cooling using carbon dioxide as a single pure working fluid. Simple, cascade and split cycle configurations are compared for power generation using a recuperator while a low-temperature loop is added for the cascade and split cycles. In a previous report in the literature the power generation part alone was presented for the three configurations and it was concluded that the split cycle can produce the highest power among the three systems. Here, the same configurations are studied combined with a compression refrigeration cooling effect... 

In this paper, a new configuration of a solar combined cooling, heating, and power (CCHP) system is proposed to recover the waste thermal energy of a steam power plant, which provides the cooling and heating needs of an apartment complex located in Tehran. The required energy of the system is supplied by the parabolic trough solar collectors (PTCs) and, if necessary, an auxiliary heater is also used. An ejector refrigeration cycle (ERC) and a steam Rankine cycle are used for cooling and power generation, respectively. The cycle is dynamically modeled over a year using a TRNSYS-EES co-simulator. It is found that the highest Rankine cycle efficiency is obtained in the cold months (January)... 

Effects of dielectric barrier discharge plasma have been studied on the wake velocity profiles of a section of a 660 kW wind turbine blade in plunging motion in a wind tunnel. The corresponding unsteady velocity profiles show remarkable improvement when the plasma actuators were operating and the angles of attack of the model were beyond the static stall angles of the airfoil. As a result the drag force was considerably reduced. It is further observed that the plasma-induced flow attenuates the leading edge vortices that are periodically shed into wake and diminishes the large eddies downstream. The favorable effects of the plasma augmentation are shown to occur near the uppermost and... 

An experimental setup has been developed to analyse the impact of cylinder transverse vibration caused by flow-induced vibration, and to improve wind energy harvesting from these vibrations. The setup consists of a cylinder mounted on four springs and is subjected to a uniform and steady flow of wind. In the first part, the effect of mounting a fixed cylinder as an obstacle with different diameters and distances from the downstream vibrating cylinder is investigated. It has been observed that the vibration amplitude on the wake of an unequal-sized obstacle is greatly amplified compared to the case of a single cylinder or an equal-sized cylinder. Numerical simulations has been conducted to... 

Minimum cost of energy is the main goal of a wind farm layout optimization. This is achieved by maximizing the total energy while minimizing the total costs of the farm. In this study, two sizes of commercial turbines were considered to investigate the effect of a non-homogenous farm on the layout optimization process. A cost model consisting of turbines, cable, transformers, foundation, and service vehicle routes was developed. Using Genetic Algorithm and Artificial Neural Network, first the superiority of the new algorithm in turbines and cable layout was verified versus previous studies. Next, two cases were investigated, i.e. (1) a farm populated with identical turbines and (2) a farm... 

Reducing the renewable energy costs is necessary for the competition with the fossil energies and control strategies have great impact on the efficiency of wind machines. In the wind turbine industry, a practical approach is to maximize the energy capture of a wind machine by optimizing the power coefficient in the under-rated situations. In this paper, with the main objective of maximizing the energy capture in the second region, four different control strategies are compared in the presence of uncertainties. The proposed control methods are compared based on their power capture and robustness against probable uncertainties in the structural and environmental parameters. A two-mass... 

Darrieus type vertical axis wind turbines have several advantages over other wind turbines for local electricity generation in urban environments. However, the main aerodynamic challenge is the negative impacts of the dynamic stall phenomenon on the turbine performance. This study numerically scrutinizes the effects of plasma actuators on the dynamic stall control and performance improvement of a Darrieus turbine. For this sake, unsteady Reynolds-averaged Navier-Stokes equations are solved using a pressure-based finite volume method. The Suzen-Hoang plasma actuator model is employed to calculate the body forces attributed to the plasma actuator. First, the dynamic stall characteristics of... 

This paper presents a multi-model robust control (MMRC) design for an offshore variable speed wind turbine with tension leg platform. The proposed control scheme covers the model uncertainty in the above rated wind speed, and it provides a reliable control for power regulation while minimizing the mechanical loads on the wind turbine structure. For this purpose, the above rated wind speed region is divided into several wind speed groups, and a set of linearized models are obtained from the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) simulator for various mean wind speeds of each group. Using Weibull wind speed distribution, a nominal model with additive uncertainty is generated... 

In this paper, inspired by a gas turbine power plant, the interaction between plant-soil processes has been simulated. It is aimed to indicate that solar energy in the photosynthesis process is equivalent to the fuel in combustion chambers. In the glucose production process, when solar exergy is considered as a fuel, 99.4% of total exergy cost is supplied by solar exergy and only 0.6% of the exergy cost is provided by nutrients’ content. In general, 30% of the total exergy entering the Calvin cycle is consumed in glucose production and the remaining 70% is related to biomass generation (as flue gas in the gas turbine). Moreover, 98% of the total exergy cost of the soil box is related to... 

The concerns regarding the consumption of traditional fuels such as oil and coal have driven the proposals for several cleaner alternatives in recent years. Hydrogen energy is one of the most attractive alternatives for the currently used fossil fuels with several superiorities, such as zero-emission and high energy content. Hydrogen has numerous advantages compared to conventional fuels and, as such, has been employed in gas turbines (GTs) in recent years. The main benefit of using hydrogen in power generation with the GT is the considerably lower emission of greenhouse gases. The performance of the GTs using hydrogen as a fuel is influenced by several factors, including the performance of... 

Excitation Controlled Synchronous Generator-based Wind Turbine (ECSG WT) is a recently proposed Wind Turbine (WT) scheme that has not been fully investigated in detail. This paper intends to analyze the performance of the ECSG WT scheme and compare it with those of two mainstream WT schemes based on electrically excited synchronous generator, i.e., VSC-based full converter WT and diode bridge rectifier-based WT equipped with boost converter on its Direct Current (DC) link. The objective of this comparison is to demonstrate great potentials of ECSG WT to be considered in the wind industry. To do so, two successful Wind Turbine (WT) schemes in the market that are structurally close to ECSG WT... 

The heat transfer simulations of turbine blades with internal cooling are faced with so many uncertainties, of which some originate from the secondary air system, including the inlet hot gas temperature and pressure and the cooling side boundary conditions, and the blade material. The main objective of this work is to carry out a suitable sensitivity analysis on a specific novel turbine vane to improve the thermal performance of its internal cooling system and to quantify how the uncertainties on the designed/calculated values can desirably/undesirably affect the maximum blade surface temperature, which can consequently affect the gas turbine engine efficiency. Furthermore, the sensitivity... 

Plasma actuator is a flow control device which may be used to improve the performance of wind turbine blades at low airspeeds. One of the most robust numerical models to simulate the interaction of the plasma actuator with the fluid flow is the electrostatic model. This model is improved by the authors. Due to the high cost of performing experimental optimization, the optimization of plasma actuators may be investigated by this numerical model. To optimize the aerodynamic performance of a Delft University (DU) wind turbine airfoil in a full stall condition, we used the operational parameters (voltage, frequency and the waveform) applied to the plasma actuator as the main design variables. We... 

The use of hybrid renewable energy has increased in recent years due to the growing environmental concerns caused by the consumption of fossil fuels. The purpose of this study was the economic-environmental feasibility of using hybrid energy systems in one of the most polluted and populated provinces in Iran, Isfahan province. Various components of the hybrid energy system such as wind turbine (WT), photovoltaic panel (PV), diesel generator (DG), converter (CV) along with two scenarios of energy storage including battery (BT) and hydrogen storage have been considered in modeling the energy system. Six scenarios were considered based on the combination of different components for supplying... 

In this paper, the drivetrain identification problem of a horizontal axis gear-driven wind turbine has been considered. The identification problem leads to a precise model of the drivetrain of the wind turbines which plays a key role in the production and transmission of electrical energy. This process consists of two stages: First, offline identification which needs the input–output data from the drivetrain system. These data are obtained from the FAST code. FAST (Fatigue, Aerodynamics, Structures, and Turbulence) is a valid aeroelastic code in the simulation aeroelastic field of offshore and onshore wind turbines. In region 2 (wind velocity is between the cut-in and rated velocities), the...