What is wind power?
Wind energy is a renewable energy whose origin is wind. This energy source takes advantage of the kinetic energy generated by the effect of air currents to transform it into other useful forms for human activities. Historically, wind energy has been used since ancient times to move sail-driven boats or operate mill machinery when moving its blades.
Wind energy is an abundant, renewable, clean resource that helps reduce greenhouse gas emissions. The installation of wind turbines makes it possible to reduce the dependence on thermoelectric plants that work with fossil fuels, or nuclear power plants (in both cases, non-renewable energy sources). For this reason, it is considered a type of green energy.
Wind energy depends indirectly on solar energy. When the sun heats the air changes density. The difference in density between different air masses causes movement and air currents. The denser (cold) air weighs more and tends to fall.
Origin of wind energy
The origin of wind energy is the wind. For this reason we can consider it an inexhaustible source of energy.
What is the origin of the wind?
Wind energy is related to the movement of air masses that move from areas of high atmospheric pressure to adjacent areas of low pressure, with velocities proportional to the pressure gradient.
The winds are generated because of the non-uniform heating of the Earth's surface by solar radiation. Between 1 and 2% of the energy coming from the Sun becomes wind. During the day, the masses of air over the oceans, seas and lakes remain cold in relation to the neighboring areas located on the continental masses. In this sense, wind energy is related to solar energy.
The continents absorb a smaller amount of solar radiation and, therefore, the air that is above the earth expands, becomes lighter and rises. The coldest and heaviest air that comes from the seas, oceans and great lakes is set in motion to occupy the place left by the hot air.
Production of electricity from wind power
In order to take advantage of wind energy in an efficient way it is convenient to study some data. It is important to know the diurnal and nocturnal and seasonal variations of the winds, the variation of the wind speed with respect to the height above the ground, the entity of the bursts in short periods of time, and maximum values occurred in historical series of data with a minimum duration of 20 years. It is also important to know the maximum wind speed. To be able to use the wind energy, it is necessary that it has a minimum speed of 12 km / h, and that it does not exceed 65 km / h. Wind turbines have a maximum capacity that if exceeded must be stopped for safety.
Wind energy is used through the use of wind machines (or windmills) capable of transforming wind energy into mechanical rotation energy. The obtained kinetic energy can be used to directly drive operating machines or for the production of electrical energy. In the latter case, the conversion system, which comprises a kinetic generator with its control and connection systems to the electricity grid, is known as a wind turbine.
The low energy density of wind energy per unit area, has as a consequence the need to proceed with the installation of more machines for the use of available resources. The most common example of a wind farm is represented by the "wind farms" (several wind turbines implanted in the territory connected to a single line that connects them to the local or national electricity grid).
Currently it is used, above all, to drive wind turbines. In these, the wind energy moves a propeller and by means of a mechanical transmission system, the rotor of a generator, normally an alternator, which produces electrical energy is rotated. For a facility to be profitable, they are usually grouped into concentrations called wind farms.
Small wind turbines
These are small-sized plants, suitable for domestic use or to integrate the electricity consumption of small economic activities typically in autonomous mode, that is, in the form of individual generators, which are then connected to the electricity grid with a contribution to the so-called generation distributed or storage facilities.
In general, these plants consist of horizontal axis wind turbines with a rotor diameter of 3 to 20 meters and a cube height of 10 to 20 meters. In general, for small wind turbines we mean systems with a nominal power between 20 kW and 200 kW, while for micro wind energy we mean systems with nominal powers of less than 20 kW.
For these small plants, the installation price is higher, reaching around 1500-3000 euros per installed kW, since the market for this type of plant is still underdeveloped.
High-altitude wind turbines
There are numerous projects, mostly still at the prototype level, for the exploitation of high-altitude wind energy, which point to a reduction in energy production costs compared to traditional wind systems. A high-altitude wind turbine is a design concept for a wind turbine that is located in the air without a tower, thus benefiting from the highest and almost constant wind speed at high altitude, avoiding the expense of tower construction, or the need of rotation of contacts or yaw mechanisms.
The challenges for a project of this type include the guarantee of having a safe suspension capable of keeping the turbines hundreds of meters from the ground in strong winds and storms, transferring the generated energy to the ground. These problems are currently faced mainly by resorting to increasingly reliable technologies developed in the field of drones. In addition, there may be interference with aviation activity.
Magnetic wind energy
A promising development of wind energy is wind-magnetic, which is produced with some type of magneto-wind turbine with the effect of reducing the friction experienced by the rotor and the y-axis of the main rotor pinion with a remarkable efficiency and lower maintenance cost.