Sharif Digital Repository

Offshore wind energy is widely recognized as a renewable energy source that has the potential as a global energy source. Although the use of coastal wind turbines has been successful, it has been challenged in terms of visual, acoustic and environmental impacts. In addition, in terms of technology, it is difficult to achieve high levels of energy from coastal wind resources due to low annual average speed; Therefore, the wind energy industry is trying to make more use of the deep-water wind resources. However, before developing these types of deep-water turbines, economic challenges and technical problems must be resolved. Mooring failure is one of the major issues in the design of offshore... 

This thesis consists of three main chapters. The first chapter is about describing principles about offshore wind turbine, principal concepts. This chapter also explains about advantages and disadvantages of installing wind turbine at offshore fields, and economical aspect of this kind of wind turbine farms. In the second chapter,anumerical method is used to investigate a SeaStar tension leg platform offshore wind turbine response behavior in parked condition. This code considers nonlinearities due to changes in tension of tethers. Wave forces are calculated adopting the Airy wave theory. Furthermore, shear turbulent wind is exerted on tower, with maximum speed 30 m/s on the hub. Since surge... 

Limited fossil resources, daily increase of demand for energy and the most important one that is environmental pollution fact, make people think of renewable energy as a solution. One type of these renewable energies is offshore wind energy that has high potential without any sound and visual noises. Recently a lot of researches have carried out their studies on the topic of offshore wind turbine. Cause of disabling of a lot of software to simulating of dynamic effect of rotating rotors, so in this research has make effort to fabricate and test an offshore wind turbine with different rotor rotating velocities and different heading angle of wind, to catch the effect of these parameter on the... 

Use of wind energy is always one of the aims of man during the times. He used this energy for wheat grinding and sometimes for marine transportations. During recent decades, technology development forced human to harness this energy and use that for electricity production by employing onshore wind turbines. However, the modern engineering employed different arms of engineering such as marine engineering, civil engineering, mechanical engineering and electrical engineering for designing and installation of offshore wind turbines. But, huge water depths in offshore regions make the fixed leg turbines to be unacceptable solution. So, the floating wind turbines with mooring lines which attach... 

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... 

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... 

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 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... 

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... 

Wind energy is one of the fastest-growing renewable energy sources around the world. Nowadays, the use of offshore wind turbines has increased due to the high and uniform wind at sea, as well as resolving environmental issues such as making noise and sound pollution. Advances in wind energy technology has been effective in wind turbine control systems. Because the offshore wind turbines are affected by the turbulent wind and wave profiles, the control system should be designed to increase the output power quality, as well as alleviating the mechanical loads on different parts of the turbine. In this research, multiple model predictive control method is used to control offshore wind turbines,...