Thermal analysis of a 2.5 MW wind turbine nacelle in variable environmental conditions (Temperature and velocity)

The arise in the demand for energy in the world day by day have increased the importance of wind turbines, which are one of the renewable energy resources. When the large scale wind turbines used to generate electricity in the world commercially are investigated, it is easy to observe that the improvements on airfoil profiles have almost stopped. Especially during the electricity generation in large scale wind turbines, are experienced in high energy losses power transfer and conversion processes. Since these energy losses are converted into the heat, they create very high temperature gradients especially on the surfaces of generator and gearbox and this situation results in design stresses. These design stresses, as result as, both decrease the turbine performance and bring forth deformations. Thus, air-conditioning systems are used for chasing this heat from the nacelle in large scale wind turbines. In a 2.5 MW wind turbine, there are three air-conditioners used for chasing this heat. Two of these air-conditioners have equal power levels. While one of them is cooling the generator, the second cools the gearbox. Each of two has an average of 75 kW power. The other air-conditioner is a smaller scaled one and has 15 kW power. This one is used to cool down electrical equipments and electronic integrated circuits. In this thesis, it is aimed to provide inside the nacelle keeping in suitable operating temperatures by the effect of outside air and, if necessary, by using an additional air-conditioner considering the summer and winter conditions maximum (45°C) and minimum (-30°C) temperatures. In the light of the results obtained from the two and three dimensional CFD analyzes using Fluent 6.3.26, it is observed that the system can operate in suitable temperatures with less air-conditioner power by the help of outside air. Consequently the turbine efficiency has increased since the consumed power inside the wind turbine is reduced.KEY WORDS: Wind Turbine Nacelle, Thermal Analysis