چكيده به لاتين
Abstract
Wind and solar are two emerging renewable sources of clean energy. Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human timescale such as sunlight, wind, rain, tides, waves and geothermal heat. In this study we will focus on generating energy from wind power. Modern utility-scale wind turbines range from around 600 KW to 5 MW of rated power, although turbines with rated output of 1.5–3 MW have become the most common for commercial use. The power available from the wind is a function of the cube of the wind speed, so as wind speed increases, power output increases up to the maximum output for the particular turbine. Thus, to obtain higher efficiency out of these systems, the tendency for design and construction of taller towers becomes more rationale. Therefore, the structural stability of these towers becomes not only a function of their ability to withstand the operational loadings but also to simultaneously resist the lateral forces exerted on these towers such as wind loadings and/or seismic loadings. For this purpose, and in order to capture the true response of such towers under the effect of seismic and wind loadings, 58 accelerogram records from variety of strong worldwide events are selected for dynamic time history analysis of the towers. The earthquake records are divided into three groups of near-field, mid-field and far-field accelerogram records. To enhance the analytical results, the two horizontal earthquake components and the vertical component of each record are simultaneously applied to each tower. Due to seismic hazards existing in many parts of the world, the design and construction of wind turbine towers in areas of high seismicity requires a thorough investigation. It is important to understand how wind turbines might respond under seismic loads in combination with wind and operation loads. Therefore, in this study the structural behavior of wind turbine towers, with generating electric power capacities of 750KW to 10MW, are investigated when subjected to strong earthquake loadings. At the end, important seismic parameters for wind turbine towers will be discussed and compared. Various seismic parameters that can affect the structural design of wind turbine towers will be discussed. Different wind loadings that are mandatory and are the basis for wind design of towers will be presented and the results obtained from the seismic and wind loading will be compared. Also, the importance of simultaneous consideration of both seismic and wind loads in a single loading combination will be discussed. If was found that near field earthquakes, have more adverse effect on such structures since only a fraction of earthquake energy will be dissipated through damping and the remaining will enter into the structures. In turbines with higher power outputs, the generated forces under maximum design wind load are almost equal to those obtained under the combination of maximum operation wind and earthquake loadings. Therefore, it is better to consider both loadings in design procedure.
Keywords: the structural design of wind turbine, time-history analysis, the effect of seismic and wind loadings, near field- mid field and far field.
