What is wind energy?
Wind energy is the energy of moving air. People have been using wind energy for thousands of years. The first windmills appeared in ancient Persia more than 5,000 years ago.
In the past, wind energy helped turn grinding stones to crush grain into flour and to pump water out of wells.
Today, wind energy is also used to create electricity, fed into the grid and then used to power our homes and industries.
Why use wind to create electricity?
- There is an everlasting supply of wind energy.
- Wind is a clean, renewable, sustainable energy supply – there is no pollution, no greenhouse gases in creating energy from the wind.
- Throughout the world wind energy technology is well proven and cost effective.
- It is one of the fastest growing electricity generation technologies around the world, with ongoing improvements increasing efficiency and reducing costs.
About wind turbines
Wind turbines have a tubular tower that supports a nacelle (box on top of the tower) and typically has three blades attached to a hub. The blade and hub assembly are also referred to as the rotor.
The nacelle typically houses the main shaft connecting the rotor to a gearbox (for geared wind turbines) and a generator and turbine controls. Direct drive wind turbines have no gearbox, and the shaft connects the rotor directly to the generator.
The tower is anchored onto a foundation with cabling, a ladder and a lift running up the tower.
Typical onshore wind turbines in operation today are up to 230 metres tall with rotor diameters of up to 164 metres.
As technology evolves, onshore wind turbines could be up to 280 metres to the blade tip with rotor diameters of up to 200 metres.
How is wind turned into electricity?
When turbine blades catch the wind, they turn the rotor. Each turn of the rotor is called a revolution. During windy weather, the rotor makes around 22 revolutions per minute (rpm) but depending on the size of the rotor and the wind speed revolutions can vary between 6 and 24 rpm.
The rotor turns a shaft connected to the gearbox, housed in the nacelle. The cogs in the gearbox convert the rotor’s revolutions to around 1,500 rpm and a fast turning shaft connects the gearbox with a generator that produces electricity.
This electricity is sent down the tower via a thick cable then underground to connect to substations where it is transformed to the right voltage for the national electricity grid.
Wind farm infrastructure
A wind farm is a group of wind turbines and their associated infrastructure. Typical elements in a wind farm are shown below.
Wind turbines
Wind turbines have a tubular tower that supports a nacelle (box on top of the tower) and typically has three blades attached to a hub. The blade and hub assembly are also referred to as the rotor. The nacelle typically houses the main shaft connecting the rotor to a gearbox (for geared wind turbines) and a generator and turbine controls. Direct drive wind turbines have no gearbox, and the shaft connects the rotor directly to the generator. The tower is anchored onto a foundation with cabling, a ladder and a lift running up the tower. Capital costs and site conditions (e.g. elevation, accessibility to transport, wind speed) can influence the choice of turbine. Typical onshore wind turbines in operation today are up to 230 metres tall with rotor diameters of up to 164 metres. As technology evolves, onshore wind turbines are expected to be up to 280 metres to the blade tip with rotor diameters of up to 200 metres within the next 5 years.
Access tracks
Access tracks are constructed and maintained within the site for delivery of turbine components, and to ensure all weather access during the operational life of the wind farm. Host landholders also have access rights to use these tracks when in the use by the wind farm. They are all season access tracks approximately 5.5 metres wide on straight ways and typically 7.5 metres (but can be up to 10 metres) in width on curves, with appropriate drainage installed where required. The access track layout is designed in consultation with the landholder with consideration to existing and future land uses.
Hardstands
Also known as crane pads, the hardstand is an area of around 40 x 60 metres located directly beside the base of the turbine. Constructed from gravel, they provide a level and dry working surface to support turbine construction, ongoing maintenance and decommissioning activities. During the construction phase, additional temporary hardstands are required for crane assembly and storage of turbine components prior to erection as well as soil storage, working areas and vehicle parking. On some projects, the crane assembly pads may become permanent for the project’s operational life.
Underground cabling
Underground cabling is installed to connect the turbines to each other and then into a substation. Cabling is installed at a depth of around 1 metre below the natural surface to allow agricultural activity to resume above. Cables typically run in a straight line or parallel to access tracks from the turbines to the substation.
Foundations
Turbine foundations are typically buried underground and are constructed from reinforced concrete. They have a diameter of 20-30 metres at the bottom of the foundation (depending on the turbine and soil conditions) which tapers off vertically to a central ring at the base of the tower. Typically only the section of the foundation right underneath the tower protrudes above ground level. The majority of the foundation will remain underground with only the inner cylinder collar where the tower connects remaining above ground.
Grid infrastructure
Grid infrastructure includes the project’s substation(s). A substation – sometimes also referred to as a collector station – is an electrical station where the power from the individual wind turbines across a project (or section of a project) comes together. Here the electricity is transformed to a higher voltage and then transmitted to the electricity grid – either directly or via a switching station and/or a terminal station via overhead transmission lines. Grid infrastructure can also include a terminal station, energy storage facilities like batteries, and overhead powerlines.
Overhead powerlines
Overhead powerlines are often required on a wind farm to connect the substation(s) to a terminal station and/or the electricity grid. Depending on size, cost and voltage, monopoles or lattice towers are installed.
Temporary construction areas
Temporary construction areas are established during the construction phase to provide a location for turbine components like blades and tower sections – as well as other project components including electrical cabling – to be stored prior to installation. These areas are returned to existing agricultural uses once construction is complete.
Other areas
Other infrastructure required for a wind farm or energy park include concrete batching plants and working areas, operations and maintenance buildings and sometimes a battery energy storage system.