From moving air to electricity
A wind turbine captures some of the kinetic energy in moving air. The blades are shaped like aircraft wings, so wind flowing past creates lift that turns the rotor. The rotor turns a shaft, and the shaft drives a generator. The result is electrical power that is conditioned and fed to a local site, a collector network or the wider grid.
Utility turbines are large machines installed in groups called wind farms. Smaller industrial turbines may serve a single facility, a remote site or a farm, often alongside a grid connection. The basic principle is the same, but the scale, the controls and the permitting differ a great deal.
What is inside the turbine
Most large turbines share the same major parts.
- Rotor and blades. Usually three blades on a hub. Pitch systems rotate each blade slightly to control how much wind it catches.
- Nacelle. The housing on top of the tower that holds the drivetrain, brake, yaw drive and controls.
- Drivetrain. On many designs a gearbox raises the slow rotor speed to something a conventional generator can use. Some designs are direct-drive and omit the gearbox. Where a gearbox is present, its maintenance needs resemble those of other gearbox types in industry, with extra difficulty from the height.
- Generator and power electronics. A converter often adjusts the electrical output so that it matches the grid frequency even when rotor speed varies.
- Tower and foundation. Taller towers reach steadier, stronger wind.
- Transformer and switchgear. Output is stepped up to a higher voltage for collection and transmission, using equipment similar to industrial transformers and switchgear found elsewhere in the power system.
Why wind speed matters so much
The power available in wind rises with the cube of the wind speed. As a simple illustration, doubling the wind speed makes eight times as much power available in the air passing the rotor, because 2 x 2 x 2 equals 8. A turbine can only capture part of that, and every design has a speed below which it will not generate (cut-in) and a speed above which it shuts down to protect itself (cut-out).
This cube relationship explains why a modest difference in average wind between two sites can make a large difference to output. It is also why wind output varies over time, with calm periods and windy ones.
Siting considerations
Choosing a location is typically a long process that involves measurements and studies, not a quick decision. Common considerations include:
- Wind resource. Developers usually measure wind over a period of time at proposed heights before committing.
- Obstructions and terrain. Buildings, trees and hills create turbulence that reduces output and adds wear.
- Grid access. The nearest suitable connection point and its capacity can decide whether a project is practical.
- Road and crane access. Blades and tower sections are long and heavy, so roads, bends and ground conditions matter.
- Neighbors and environment. Noise, shadow flicker, visual impact, birds and bats, and protected land are normally reviewed under local rules.
- Aviation and radar. Authorities often have to be consulted.
- Ground and foundations. Soil conditions affect design and cost.
Rules and approval processes differ widely by country and locality, so a general article cannot say what applies to a specific site.
Operation and maintenance
Turbines are monitored remotely and inspected on a schedule. Typical items include blades, bearings, the gearbox oil, the yaw and pitch systems and electrical connections. Condition monitoring and vibration analysis help to spot developing faults, which is useful because a crane visit to a nacelle is costly and depends on the weather.
Working at height and on high-voltage equipment is hazardous. It is done by trained, certified crews using the manufacturer’s procedures, lockout and tagout style energy isolation and local regulations.
Where wind fits for an industrial user
An industrial site rarely relies on wind alone. Wind output is variable, so most facilities combine it with the grid, storage or on-site generation. Some buy wind-sourced power through their utility instead of building a turbine. Others compare it with options such as industrial solar power. A broader comparison of options is made in the discussion of alternative power sources, and any decision is better made with a qualified engineer who can use real wind data and the local rules.