Wind energy and wind turbines explanation in simple words

Wind energy explanation
Wind Energy

Wind energy is a motion or kinetic energy of motioning air. The wind, which has energy, appears because of the uneven heating of the atmosphere by the sun, unevenness of the earth's surface, and the rotation of the Earth. Wind speed determines the amount of kinetic energy and we can convert it into mechanical energy or electricity. We can use mechanical energy, for example, for grinding grain and pumping water. We can also use mechanical energy to operate turbines that produce electricity. This work focuses specifically on wind power, and not on other non-electric forms of wind power.

There are two principal ways in which we can convert wind energy (for both mechanical and electrical purposes): using either the “aerodynamic drag” or “lift” force. Aerodynamic drag means placing one side of the surface against the wind while the other side is on the leeward side. Movement because of aerodynamic drag occurs in the same direction as the wind blows. The lifting method slightly changes the direction of the wind and creates a force perpendicular to the direction of the wind. The aerodynamic drag method is less effective than the lift method.

Wind energy concentration

The concentration of wind energy differs from 10 W / m-2 (with light breeze 2.5 m / s) and up to 41000 W / m-2, during a hurricane with a wind speed of 40 meters per second (m / s) or 144 km / h. Wind energy is always proportional to the wind speed's cube. This means that electric power is sensitive to wind speed (when doubling wind speed, power increases eight times)

The wind speeds necessary for generating electricity should be at least 2.5–3 m / s and not over 10–15 m / s. Many regions of the Earth are not suitable for placing wind turbines, and almost the same number of regions is characterized by average wind speed in the range (3-4.5 m / s), which can be an attractive option for generating electricity. However, a significant part of the Earth’s surface is characterized by an average annual wind speed exceeding 4.5 m / s, when wind energy can certainly be economically competitive.

Assessing wind resources in a particular area is a complex task that requires comprehensive data. The availability and The reliability of wind speed data is low in many regions of the world. The potential for generating wind power depends on the following four factors:

  • latitude and prevailing wind patterns
  • relief and height
  • water bodies
  • vegetation and development

The wind speed prevailing in the region can be determined based on the global model (low- and high-latitude eastern, mid-latitude western, and low-wind, tropical convergence zones). Also, the sea and land breezes are often observed in coastal areas, and high-altitude areas can amplify air disturbances caused by thermal cyclones.

Global trends

Wind energy, with its inception in the late 1970s, has become a global industry in which energy giants take part. In 2008, new investments in wind energy reached $51.8 billion (€35.2 billion) (UNEP, 2009).

According to statistics published by the European Wind Energy Association (EWEA, 2011), thriving markets exist in places with accommodation conditions. In 2008, wind power plants generated about 20% of all Danish electricity, over 11% in Portugal and Spain, 9% in Ireland and almost 7% in Germany, over 4% of all electricity in the European Union (EU) and almost 2% in the United States ( IEA Wind Power, 2009).

Since the year 2000, the total installed capacity has grown by an average of 30% per year. In 2008, over 27 GW of electric power was installed in over 50 countries, resulting in global land and sea potential of 121 GW. In 2008, the World Wind Energy Council estimated that about 260 a million megawatt-hours (260 terawatt-hours) of electricity had been generated.

When planning the placement of wind power plants, it is advisable to have more information about wind speed, and not just a national map, since terrain features such as topography, elevation, water bodies and vegetation have a significant impact on wind resources.

Wind turbines designs

The possibility of generating electricity is determined by the design of wind turbines. All wind turbines comprise blades that rotate an axis connected to a generator that produces an electric current.

Wind turbines can be located almost everywhere where there is the wind, for example, at sea, on land, and in a built-up place.

Wind turbines have various sizes and rated power. The largest turbine has blades with a scope greater than the length of the football field, the height of a 20-story building, and produces enough electricity to power 1,400 buildings. Conversely, a wind turbine the size of a small house has blades with a diameter of 8 to 25 feet, a height of over 30 feet, and can provide electricity to a fully electrified building or small business.

The size and power of wind turbines differ. We distinguish three fundamental types of wind turbines: with a horizontal axis, with a vertical axis and channel.

Horizontal axis turbines (Propeller wind turbines)

Propelled wind turbines (abbreviated HTP) are dominant. This view is like a windmill with propeller blades that rotate around a horizontal axis.

Propeller wind turbines have a rotor main axis and an electric generator at the top of the mast. We should direct the rotor axis towards the wind. Small turbines are guided downwind by simple guides mounted perpendicular to the rotor blades, while large turbines typically use a wind sensor to control the rotary motor. Most large wind turbines have a gearbox that converts the slow rotation of the rotor into the fast rotation of the generator, which is important for generating electricity.

Experts make the blades of the wind turbines rigid to prevent the blades from hitting the mast in powerful winds. Also, the blades are located at a considerable distance from the mast and sometimes slightly inclined.

Since experts create turbulence behind the mast, they usually locate turbines on the side from where the wind blows. Otherwise, turbulence can lead to fatigue stress accidents, which reduces the reliability of the installation. Despite the problems of turbulence, installations were built with the turbine in the wind's direction, since they do not need an additional mechanism for their orientation in the wind, and, during strong winds, their blades can bend, which reduces the slip zone and reduce the way of wind resistance.

Vertical axis wind turbines (Wind rotor wind turbines)

Wind turbine wind turbines (IWT) are of various types, but they all have one thing in common: the main rotor shaft is located vertically (rather than horizontally).

Engineers design various models specifically for places where the direction of the wind is very variable or restless. Experts consider iWTs easier to install and maintain, as the generator and another key component can be placed close to the ground (there is no need for the mast to hold the components of the turbine and the components become more accessible).
IWT is less effective than AVP because:

  • They often create rotation resistance.
  • Often installed at a lower height (ground or roof of a building), where the wind speed is lower.
  • The presence of vibration-related problems, such as noise and faster wear and tear of the supporting structure (since the airflow has greater turbulence at low altitudes).

IWT Daria

Patented by French aviation engineer Georges Jean-Marie Darier in 1931, we often call the Darier wind turbine the “egg whisk” because of its appearance. It comprises several vertically directed blades that rotate around a central axis.

The difference between the HTP and the Darya IWT is that the axis of the propeller turbine always collides with the wind, and the Darier turbine is a cylinder perpendicular to the airflow. Thus, part of the turbine works, and the other part just spins in a circle.

The difference between the HTP and the Darya IWT is that the axis of the propeller turbine always collides with the wind, and the Darier turbine is a cylinder perpendicular to the airflow. Thus, part of the turbine works, and the other part just spins in a circle.

The blades allow the turbine to reach speeds that are higher than the actual wind speed, which makes them suitable for generating electricity, and not for pumping water, for example. The Darier turbine can operate at wind speeds up to 220 km / h and in any direction.

The major disadvantage of the Darier turbine is the inability to turn it on independently. Starting the turbine requires an external drive (for example, a small engine or a set of small Savonius turbines). At a sufficient speed of rotation, the wind creates sufficient torque, and the rotor rotates around its axis with the help of wind.

The Daria turbine is theoretically as efficient as the propeller type if the wind speed is constant, but we rarely realize this efficiency because of the occurring physical stresses, design features, and variability of the wind speed.

A particularly Darier turbine is Type H (or Gyromill). To get wind energy, it works on the same principle as the Darier wind turbine, but instead of curved blades, experts use 2 or 3 straight blades individually attached to the vertical axis.

IWT of Savonius

The Savonius turbine is a simple turbine that was invented in its modern form by the Finnish engineer Sigurd Johannes Savonius in 1922. We usually use it in cases requiring high reliability rather than high efficiency (for example, in ventilation, in anemometers, in domestic micro-production).

Savonius turbines are much less efficient than the high-voltage and high-voltage weapons of Daria (about 15%, Calculation of wind energy), but unlike the former, they work well in turbulent winds and, unlike the latter, they turn on themselves. Structurally, they are stable, can withstand powerful winds, and remain without damage and are quieter compared to other types.

Unlike the Darier turbine, which operates under the action of the “lift” force, the Savonius turbine operates according to the principle of “aerodynamic drag”. It comprises 2-3 “buckets”: curved elements experience less resistance when moving against the wind than when moving downwind because of the curved shape of the buckets. From an aerodynamic point of view, it is this differential resistance that makes the Savonius turbine spin.

Wind energy calculation

Wind power (P in watts) at a known wind speed is calculated using the following formula:

P = ½ x “air density” x “coverage area” x (wind speed) 3

Above sea level, “air density” is approximately 1.2 kg / m3, “wind speed” is wind speed (m / s) and “coverage area” refers to the area of ​​space covered by the wind turbine rotor. We can calculate by the length of the turbine blade:

A = π x (blade length) 2

However, as soon as important technical requirements for wind turbines are taken into account (for example, strength and wear resistance, gear ratio, bearings, generator requirements), the limit of the amount of energy that can be obtained from wind energy is reduced to 10-30% of actual wind power. This limit is called a “power factor,” which is unique to each type of wind turbine. To calculate the amount of energy extracted, this power factor (CP) must be entered in the above formula:

P available = ½ x “air density” x “coverage area” x (wind speed) 3x CP

The power factor CP depends on the wind turbine and varies from 0.05 to 0.45.

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