Sharif Digital Repository

Nowadays, modern life needs energy resources. In the last few centuries, countries have focused on the use of fossil fuels. However, excessive use of fossil fuels, such as oil and coal, has resulted in enormous environmental hazards. Global warming and air pollution are the most visible manifestations of these hazards. In recent years, energy researchers have been looking for alternative sources. The result of this approach is to pay attention to clean and renewable resources such as wind energy.Wind turbines are used to generate electrical energy out of wind. Among the different types, floating offshore wind turbines have been mostly considered because of various benefits. However, they... 

Vibrations in HAWT reduce their efficiency and increase maintenance costs. In this paper, the blade edgewise vibrations are reduced by using several actuators in different parts of the wind turbine blade and optimization of the number and locations of actuators. The wind turbine blade dynamic behavior is investigated by using dynamic modeling. The actuators are trusses that are located inside each blade and apply control force to different parts of the blade. Active control force is applied to reduce edgewise vibrations. The designed controller is applied and simulated on NREL 5MW wind turbine. By applying the controller, the edgewise vibrations of wind turbine blades are significantly... 

In recent decades, renewable energy resources (especially wind power as the fastest-growing energy source) have increasingly been employed for providing electrical energy all over the world given to the rising energy demands, reduction in non-renewable fossil fuels as well as severe restrictions applied to the utilization of these fuels because of their contribution in environmental pollution, generating greenhouse gas emissions, and consequently earth warming. The main factors in the development of wind energy systems to date are the easy access to this energy source in all seasons and its cost-effectiveness compared to other counterparts. One of the key components utilized for converting... 

Use of renewable energy has already increased significantly. One of the renewable and suitable sources for replacement with fossil fuels is wind energy, especially wind turbines. But the design, construction, installation maintenance and operation of wind turbines are relatively expensive. One of the most expensive parts of a wind turbine is its gearbox. Wind turbines gearbox due to fluctuating loads unexpected is likely to suffer a premature fatigue. The purpose of this project is to calculate some of the oscillating loads applied to the gearbox and then to investigate the effect of these loads on the service life of the gearbox components. Tower shadow effect and wind shear effect are the... 

For validation of simulation, plasma actuator was modelled on a flat plate in quiescent flow, which is result in low-speed jet near the wall. The results were compared with similar model and were showed good agreement with them. After that, blade was modelled in three-dimensional manner with MRF technique and periodic method and the results were validated in clean situation (absence of plasma). In the following, turbine was analysed with a code, which was written in MATLAB software based on BEM method and the results were compared with present CFD simulation. Then, plasma actuator was used in chordwise in parts of the blade to improve wind turbine performance. Also it was used in spanwise... 

In this study, a framework for reliability analysis of offshore wind turbine structures has been presented. The rapid development of these structures in the world due to the increasing need for electrical energy and limited sources of fossil fuels has increased the importance of research on the behavior and condition of these structures. For Iran, despite its fossil fuels resources due to its international voluntary commitments to reduce greenhouse gases such as Paris agreement, the use of renewable energy such as offshore wind energy is important. Also, the offshore wind turbine structure is affected by different forces and environmental conditions in its life cycle, which are associated... 

In recent years, much attention has been paid to wind energy and the expansion of wind farms to replace fossil fuels with this energy source. Wind turbine blades are currently made of composite materials using thermoset matrices. These materials are not recyclable, and it is impossible to return their resins or fibers to the production cycle. In this research, an attempt has been made to replace thermoset resins with thermoplastic materials that can be recycled. In the following, manufacturing and performance aspects of thermoplastic resins have been examined, and the optimal material has been selected using the modified fuzzy logic method (MFLM). In this study, reactive processing of... 

Recent decades have seen a growing demand for high-power wind turbines resulting in turbines with larger blades and the advent of high-megawatt wind turbines. The blades of the megawatt-scale turbines experience more complicated flow phenomena compared to those of the smaller-scale wind turbines. Needless to say, the importance of an accurate solution and detailed analysis of all the parameters, including blades aerodynamic and aeroelastic performance as well as fluid-structure interaction, is more significant for the megawatt-scale turbines compared to smaller-scale turbines. The conventional methods of aerodynamic solutions for the blade, including analytical methods, such as BEMT78 and... 

This project has been carried out to investigate the feasibility of using thermoplastic materials in constructing large wind turbine blades made of composite materials. By proving the similarity of the mechanical behavior of blades made of thermoplastic and thermosetting composite materials, the possibility of using these materials with better recycling capabilities has been studied. By studying different thermosetting and thermoplastic resins and checking the Processing methods and mechanical properties of thermoplastic resins, the materials for blades have been selected. The suitable manufacturing method for producing large blades with dimensions above 30 meters is the vacuum-assisted... 

Optimization-based wind farms control focusing on fatigue loads minimization represents a promising approach to establish a balanced tradeoff between power production in wind farms and lifetime extension of the wind turbines. This dissertation aims to develop a novel strategy to determine individual wind turbine power set-points in such a way that fatigue loads imposed on the units are minimized. The research considers main oscillation modes of the turbine structure and the determining forces to evaluate the amount of fatigues.Based on detailed modelling of wind farms which includes influences of wake effects on the mean wind speed and turbulence intensity, a novel approach is used to... 

Dynamic increasing amplitude and period (DIAP) [1] is a time-domain analysis methodology developed based on endurance time (ET) analysis method [2], which can be used to evaluate the response of marine structures when encounters a continuous loading, such as storm conditions. In this method, instead of using separate records with different intensities, a single loading record with an increasing intensity over time is used for structural analysis. The ability to enter spectral concepts, considering the effects of waves with different frequencies and amplitudes, taking into account the effects of randomness of waves and the possibility of short duration analysis are some of the specific... 

The power control of horizontal axis wind turbines can affect significantly the vibration loads and fatigue life of the tower and the blades. In this thesis, we are going to consider both the power control and vibration load mitigation of the tower fore-aft vibration. For this purpose, at first, we developed a fully coupled model of the NREL 5MW turbine. This model considers the full aeroelastic behavior of the blades and tower and is validated by experiment results, comparing the time history data with the FAST (Fatigue, Aerodynamics, Structures, and Turbulence ) code which is developed by NREL (National Renewable Energy Lab in the United States). In the next, to estimate EWV, a novel... 

The rapid development and growth of the offshore turbine industry has led to the construction of offshore wind farms in earthquake-prone areas, and due to the shape of the structural system, which consists of a long cylindrical tube with a heavy mass on top of it, this structure is a sensitive structure. It has a dynamic behavior, and many environmental loads such as wind load, wave load, current load, and earthquake load in seismic areas are dynamic in nature. In this research, it investigates the seismic dynamic behavior of 5MW offshore wind turbine using the ISO-19901-2 standard and the Endurance Time method. In the modeling of this structure, Soil Structure interaction and Fluid... 

For many years, humans have been able to use wind energy to meet some of their needs. By improving science and the discovery of electricity as the mother of energy that is very easy to use, mankind thought of converting wind energy into electricity, so wind turbines were invented. Despite the wide spread of onshore wind turbines, their visual, acoustic and environmental negative effects still cause dissatisfaction among the residents of the areas where these turbines are installed. Also, the high wind speed in the seas compared to the land ares has caused the interest to use offshore wind turbines to increase in the past years. For this reason, an attempt has been made in this thesis to... 

Nowadays, electrical energy is one of the crucial requirements in human beings’ lives. Since the majority of the world’s energy is met by fossil fuel, the problems such as global warming, the reduction of fossil fuel resources, and unpredictable oscillation of the prices of such fuels have led to a serious crisis for the people of the world. Furthermore, due to the increasing energy demand, the economic development of most countries has a strong correlation with fossil fuel prices. The abovementioned problems have made a lot of countries take alternative policies in terms of generating energy, one of which is using renewable energy resources. This approach is reported to be clean and... 

The purpose of this project is designing a controller for a floating offshore wind turbine to exctract maximum power from wind energy in the first operating region of wind turbine. The NREL 5 MW OC3-Hywind floating wind turbine with BARGE platform will be used for this project. By using Turbsim software, proper wind profile for the first operating region of wind turbine will be produced. This profile will be excecuted for the FAST software that is simulates the mechanical part of wind turbine. By implementing the doubly fed induction generator in Simulink enviroment and designing the controller for doubly fed induction generator, the desired torque for maximizing the exctraction power of... 

Technology systems are vulnerable to various defects. Acuator failures reduce the performance of control systems and even they can damage the entire system. Incorrect reading from the sensors is the cause of many inefficiencies, because errors can reduce the quality and efficiency of a product line. In addition, failure of a single system's component can cause a system failure. Electromechanical energy conversion devices are composed of hundreds different components and subunits that are subject to varying adverse environmental conditions, and that is why the sensors, actuators, and components are likely to malfunction. Unexpected defects and unplanned repairs result in high operating costs... 

One of the main drivers for the substantial growth in wind energy utilization in the world is the growing demand for renewable energy sources to reduce greenhouse gas emissions. At greater distances from the coastline, more and steadier potential energy resources are available. This has led the world offshore wind energy industry to grow at a faster rate than onshore in the past two decades. In deep waters, the wind turbine is mounted on a floating platform, whose movements increase the complexity of the turbine control system and enhance the mechanical loads on the various components of the turbine. Reducing these mechanical stresses is equivalent to increasing the lifetime of the turbine... 

The use of wind energy due to the clean and unlimited nature of this energy has received more attention and for this purpose, the types of wind turbines that mainly include; monopile turbines and jacket-based turbines; is used In this research project, it has been tried using criteria such as equal weight of structures with different bracing shapes and taking into account the normalized energy and redundancy factors of the platforms; An optimal structure that can achieve a better capacity curve with the same material cost, which includes ultimate stress and greater ductility, and along with all the above factors; The redundancy of the structure has also been considered to minimize the risk... 

Due to the higher wind speed in the seas and the lack of barriers in front of the turbine, and the lack of residents next to them, the noise of the turbine makes them uncomfortable, and the lack of a limit to the turbine's dimensions, has made the offshore wind turbines receive a lot of attention. And the jacket platform also costs much less to build and maintain than floating platforms. Given that these structures are built on the codes of oil rigs, most of them are designed overdesigned, so it is essential to optimize these rigs so that they are less costly and less material is used to build them. In this thesis, we considered shape optimization by considering a real jacket wind turbine...