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Wind turbines convert the energy in wind to electricity by rotating propeller-like blades around a rotor. The rotor turns the drive shaft, which turns an electric generator. Three key factors affect the amount of energy a turbine can harness from the wind: wind speed, air density, and swept area.
In the U. As of the third quarter of , the U. Instead, the air is pushed to the west in the northern hemisphere and to the east in the southern hemisphere. This is known as the Coriolis force. Click to see a diagram of how the movement of the Earth affects wind. The Earth's surface is marked with trees, buildings, lakes, sea, hills and valleys, all of which also influence the wind's direction and speed.
For example, where warm land and cool sea meet, the difference in temperature creates thermal effects, which causes local sea breezes. Wind is usually measured by its speed and direction. Wind atlases show the distribution of wind speeds on a broad scale, giving a graphical representation of mean wind speed for a specified height across an area.
They are compiled by local meteorological station measurements or other wind-related recorded data. Traditionally, wind speed is measured by anemometers — usually three cups that capture the wind rotating around a vertical axis pictured below. The wind direction is measured with weather vanes. After measuring wind data for at least one year, the mean annual wind speed can be calculated. Wind speed and wind direction statistics are visualised in a wind rose, showing the statistical repartition of wind speed per direction.
Wind statistics show the best sites to locate wind farms according to the best wind resources. They also provide further information on how the turbines should be positioned in relation to each other and what the distance between the turbines should be.
A wind turbine is a machine that transforms the kinetic energy of the wind into mechanical or electrical energy. Wind turbines consist of a foundation, a tower, a nacelle and a rotor. The foundation prevents the turbine from falling over. The tower holds up the rotor and a nacelle or box. The nacelle contains large primary components such as the main axle, gearbox, generator, transformer and control system.
The rotor is made of the blades and the hub, which holds them in position as they turn. Most commercial wind turbines have three rotor blades. The length of the blades can be more than 60 metres. See how a wind turbine works! The average size of onshore turbines being manufactured today is around 2. It can power more than 1, average EU households. An average offshore wind turbine of 3.
In , wind turbines were under 1 MW with rotor diameters of around 15 metres. In , the average size is 2. The towers are mostly tubular and made of steel or concrete, generally painted light grey. The blades are made of fibreglass, reinforced polyester or wood-epoxy. They are light grey because it is inconspicuous under most lighting conditions.
The finish is matt, to reduce reflected light. There are many factors at play when designing a wind farm. Ideally, the area should be as wide and open as possible in the prevailing wind direction, with few obstacles. Its visual influence needs to be considered — few, larger turbines are usually better than many smaller ones. The turbines need to be easily accessible for maintenance and repair work when needed. Noise levels can be calculated so the farm is compatible with the levels of sound stipulated in national legislation.
The turbine supplier defines the minimum turbine spacing, taking into account the effect one turbine can have on others nearby — the 'wake effect'. Then, the right type of turbine must be chosen. Construction time is usually very short — a 10 MW wind farm can easily be built in two months. A larger 50 MW wind farm can be built in six months. Costs vary but the biggest cost is the turbine itself.
This is known as its capacity factor. The optimum number of blades for a wind turbine depends on the job the turbine has to do. Turbines for generating electricity need to operate at high speeds, but do not need much turning force.
These machines generally have three or two blades. On the other hand, wind pumps need turning force but not much speed and therefore have many blades. Wind Energy Data. Investment trends. Employment by energy sector. Recent Publications. Offshore Renewables: An Action Agenda for Deployment The report provides insights on various emerging offshore renewable energy technologies an Tracking the Impacts of Innovation: Offshore wind as a case study This report is an initial output of two projects focused on tracking Related Content.
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