Even if you haven't seen huge wind turbines in person, you're sure to have seen photos or videos of them. But what's the process that occurs before they're up and generating electricity?
Here we take a look.
The first stage is to find a suitable location for the wind farm. Using unique software and expertise that has been developed over the last decade, Windlab can prospect the world for suitable sites.
In addition to finding places where the wind blows hard and long, the location must also have access to high voltage electricity lines, have an existing land-use that integrates well with wind-powered electricity production and meet appropriate planning and environmental conditions.
turbulence modellingOnce a suitable potential location has been found, Windlab models different turbine locations, taking into account local wind speeds and turbulence.
predicted sound levelsModeling is also carried out of the pattern of sound coming from the turbines. This helps fine-tune the proposed turbine locations.
Testing and Planning
Individual commercial agreements are then made with local landholders to allow testing and planning to occur on the site.
The computer-modeled information on wind speeds is then validated by on-site measurements. A metrological mast may be erected to measure wind speeds and directions at different heights.
Another method of measuring the wind is to use SoDAR - sonic range and detecting equipment. This allows the measurement of vertical wind profiles without requiring the erection of a mast.
Independent and detailed environmental flora and fauna studies are made and bird and bat movements and populations are analyzed.
The capability of the existing electricity lines to carry power generated by the wind farm is also evaluated.
Civil works and foundations
With the planning complete, construction can begin.
The first step is to build the roads that will allow truck and crane access to allow the turbine towers and parts to be transported to the individual turbine locations.
These roads remain in place after construction has finished, providing good access around the area for landholders.
Concrete footings for the turbine towers can be of two types - a concrete gravity pad that uses a wide base located just beneath the surface soil with a smaller diameter protruding part to which the tower is attached, or a rock anchor that uses a smaller concrete structure and connects the tower to bedrock. Shown here is a rock anchor.
Near to the base of each tower is a transformer that increases the generated voltage from 690V to 33kV. A hardstand is built to site this transformer.
The major parts of the wind turbine are transported to the location to be assembled on-site. The long blades, made from fiberglas epoxy composite, are transported in specific steel shipping crates.
Each blade is shipped separately - the three blades are joined on-site to form the rotor. Blades are typically about 45 meters long.
The towers are usually trucked-in as four 20 meter long sections, each weighing about 38 tons. To provide weather protection the towers are coated in expoxy urethane.
The final major component is the nacelle, containing the generator, gearbox and control gear. This unit, which weighs about 70 tons, uses a fiberglas shell.
Once the parts arrived they can be lifted into position.
Massive cranes are used to assemble the towers section by section.
Multiple wind turbines can be erected simultaneously.
The blades and nose cone are joined to the hub on the ground. This rotor sweeps an area of just over 6,000 square meters - that's more than 64,000 square feet!
The assembled rotor is then lifted into position. This process requires two cranes and can be carried out only in ideal weather conditions.
A major windfarm will employ more than 200 people during the 18 months of construction and will require an ongoing maintenance crew of 6-12 people.
The area of land used by a wind farm - including the roads, transformers and turbine pads - is only 1-2 per cent of the total land area. This means that 98 - 99 per cent of the land can continue to be used as previously.
Wind farms generate an additional revenue stream for landholders and produce environmentally sustainable electricity without emitting greenhouse gases. And while their siting, design and construction involve large and at times complex processes, wind power is a mature, well-proven and effective technology.