Energy Transmission and Grid Integration of AC Offshore Wind Farms
The aim of this chapter is to introduce the reader to the wind energy. In this way, as the primary source of wind energy, how the wind is created and its characteristics are evaluated. Due to its nature, the wind is an un-programmable energy source. However, it is possible to estimate the wind speed and direction for a specific location using wind patterns. Therefore, in the present chapter, how to describe the wind behavior for a specific location, the kinetic energy contained in the wind and
... ts probability to occur is described. To convert the wind energy into a useful energy has to be harvested. The uptake of wind energy in all the wind machines is achieved through the action of wind on the blades, is in these blades where the kinetic energy contained in the wind is converted into mechanic energy. Thus, the different ways to harvest this energy are evaluated, such as: different kind of blades, generators, turbines... Once, the wind and the fundamentals of the wind machines are familiar, the advantages / disadvantages between offshore and onshore energy are discussed. The wind The unequal heat of the Earth surface by the sun is the main reason in the generation of the wind. So, wind energy is a converted form of solar energy. The sun's radiation heats different parts of the earth at different rates; this causes the unequal heat of the atmosphere. Hot air rises, reducing the atmospheric pressure at the earth's surface, and cooler air is drawn in to replace it, causing wind. But not all air mass displacement can be denominate as wind, only horizontal air movements. When air mass has vertical displacement is called as "convection air current" The wind in a specific location is determinate by global and local factors. Global winds are caused by global factors and upon this large scale wind systems are always superimposed local winds. Global or geostrophic winds The geostrophic wind is found at altitudes above 1000 m from ground level and it's not very much influenced by the surface of the earth. The regions around equator, at 0° latitude are heated more by the sun than the regions in the poles. So, the wind rises from the equator and moves north and south in the higher layers of the atmosphere. At the Poles, due to the cooling of the air, the air mass sinks down, and returns to the equator.