A growing amount of renewable electricity is being harnessed from the wind. Australia has an abundant supply of wind resources, which, if utilised adequately, can save significant greenhouse gas emissions.

Domestic wind generators (also called turbines) are usually used in stand alone power systems and are designed to charge a battery bank.
Although wind generators produce AC (alternating current) power similar to the grid, there are currently no guidelines for interconnecting small domestic sized wind generators directly to the grid. They may only be connected via an inverter.

The main body of the wind generator comprises a set of blades, the alternator and the tail section. The power of the wind makes the blades turn. The blades are connected to the rotor inside the alternator, which turns and generates electrical power. The alternator consists of magnet and copper wire. The inside stays still and the outside rotates. This produces the current. The tail ensures that the wind generator is facing directly into the wind.

The wind generator produces alternating voltage and current, and these are rectified to provide DC (direct current) at the correct voltage to charge batteries. This process is similar to charging the battery in a car.

Wind speed increases as the height above the ground increases

Cost: $40 000

Height: 35 mBlades: 7.5 m

Up to 300 revolutions per minute (wind farm in Atherton Tablelands 30 rpm)

Advantages: clean energy, night and day,

Disadvantages: Noise, Cost, aesthetics, cyclones – ensure no damage; make sure the tail is not allowing the blades to utilise the wind. the wind generator maintenance required – the wind generator is lowered about 3 times a year for maintenance which includes maintaining the blades.

WIND GENERATORS

A wind generator is a device that generates electrical power from wind energy.

Wind generators have traditionally been wind turbines, i.e. a propeller attached to an electric generator attached to appropriate electronics to attach it to the electrical grid or to charge batteries.

A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator, wind power unit (WPU), or wind energy converter (WEC).

Modern wind turbines

The wind turbines on High Knob in the Moosic Mountains of Pennsylvania

Turbines used in wind farms for commercial production of electric power are usually three-bladed and pointed into the wind by computer-controlled motors. These have high tip speeds of up to six times the wind speed, high efficiency, and low torque ripple, which contribute to good reliability. The blades are usually colored light gray to blend in with the clouds and range in length from 20 to 40 metres (65 to 130 ft) or more. The tubular steel towers range from 200 to 300 feet (60 to 90 metres) tall. The blades rotate at 10-22 revolutions per minute.[12][13] A gear box is commonly used to step up the speed of the generator, although designs may also use direct drive of an annular generator. Some models operate at constant speed, but more energy can be collected by variable-speed turbines which use a solid-state power converter to interface to the transmission system. All turbines are equipped with shut-down features to avoid damage at high wind speeds.

Horizontal axis

Components of a horizontal axis wind turbine (gearbox, rotor shaft and brake assembly) being lifted into position

Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and are usually pointed into the wind. Most small turbines are pointed by a simple wind vane, although there are now a number of more modern designs which are classed as down wind machines and which require no tail vane. Large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.[9]

Since a tower produces turbulence behind it, the turbine is usually pointed upwind of the tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted up a small amount.

Turbine design and construction

Components of a horizontal-axis wind turbine

Main article: Wind turbine design

Wind turbines are designed to exploit the wind energy that exists at a location. Aerodynamic modeling is used to determine the optimum tower height, control systems, number of blades{fact|april 2009} and blade shape.

Wind turbines convert wind energy to electricity for distribution. Conventional horizontal axis turbines can be divided into three components.

  • The rotor component, which is approximately 20% of the wind turbine cost, includes the blades for converting wind energy to low speed rotational energy. These blades are usually made of composite fiber materials, and are increasingly being coated with specialized epoxy resins to further protect them and offer higher efficiency.
  • The generator component, which is approximately 34% of the wind turbine cost, includes the electrical generator, the control electronics, and most likely a gearbox component for converting the low speed incoming rotation to high speed rotation suitable for generating electricity.
  • The structural support component, which is approximately 15% of the wind turbine cost, includes the tower and rotor yaw mechanism.[18] Most of the structural components for today's turbines are made of steel and specially painted to inhibit corrosion.

Advantages and disadvantages

See also: Environmental effects of wind power

Livestock ignore wind turbines,[25] and continue to graze as they did before wind turbines were installed.

Wind turbine development has both positive and negative environmental impacts.

Wind energy system operations do not generate air or water emissions and do not produce hazardous waste. Nor do they deplete natural resources such as coal, oil, or gas, or cause environmental damage through resource extraction and transportation, or require significant amounts of water during operation. Wind's pollution-free electricity can help reduce the environmental damage caused by power generation from fossil fuels.[26]

Wind turbines consume no fuel, and emit no air pollution, unlike fossil fuel power sources. The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months of operation.[27]

Wind power is an intermittent power source. The power production from a wind turbine may increase or decrease dramatically over a short period of time with little or no warning. In the absence of large scale energy storage, or extra geographically dispersed turbines, the balance of the grid must be able to quickly compensate for this change.

The economics of wind turbines can be challenging as well.[28] With high quality wind resources often located in areas inhospitable to people,[29] logistics and transmission capacity can introduce significant obstacles to new installations.[30] However, in the UK, new offshore wind farms are being located adjacent to population centres. The London Array is an example of this. The new Whitelee Wind Farm is located 15 kilometers (9 miles) outside of Glasgow, Scotland’s largest city.

The impact of wind turbines on wildlife has often been cited as a disadvantage of wind installations. Wind turbines can pose a small danger to birds and bats, both directly and by displacement. However, preliminary studies estimate that wind turbines kill approximately 20 times fewer birds per unit of energy generated compared to fossil fuel power plants; 14.5 million birds were killed by fossil fuel power generation in the USA in 2006, compared to around 7000 killed by wind turbines.[31]Early installations such as the Altamont Pass installation used short steel towers with high rotor speeds, leading to high numbers of bird deaths. Studies of modern monolithic tower structures have shown lower impacts on bird populations. The Black Law Wind Farm has received praise from the RSPB for benefiting wildlife.

Some individuals living in very close proximity to large turbine installations have voiced complaints about their visual impact.[32] Complaints about noise have also been made. However, local residents near the Ardrossan Wind Farm have found wind turbines to be "silent workhorses" which are impressive looking, and bring a calming effect to the town.[33]

Some opponents of wind turbines claim that turbines produce infrasound; however, measurements of wind turbine noise signatures have found that the sound pressure levels produced are too low to have any effect.[34][35]

Environmental effects of wind power

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Livestock ignore wind turbines,[1] and continue to graze as they did before wind turbines were installed.

Compared to the environmental effects of traditional energy sources, the environmental effects of wind power are relatively minor. Wind power consumes no fuel, and emits no air pollution, unlike fossil fuel power sources. The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months of operation.[2] Garrett Gross, a scientist from UMKC in Kansas City, Missouri states, "The impact made on the environment is very little when compared to what is gained." While a wind farm may cover a large area of land, many land uses such as agriculture are compatible, with only small areas of turbine foundations and infrastructure made unavailable for use.[2]

Danger to birds and bats has been a concern in some locations. However, studies show that the number of birds killed by wind turbines is negligible compared to the number that die as a result of other human activities, and especially the environmental impacts of using non-clean power sources. Bat species appear to be at risk during key movement periods. Almost nothing is known about current populations of these species and the impact on bat numbers as a result of mortality at windpower locations. Offshore wind sites 10 km or more from shore do not interact with bat populations.

Aesthetics have also been an issue in some areas. In the USA, the Massachusetts Cape Wind project was delayed for years mainly because of aesthetic concerns. In the UK, repeated opinion surveys have shown that more than 70% of people either like, or do not mind, the visual impact. According to a town councillor in Ardrossan, Scotland, the overwhelming majority of locals believe that the Ardrossan Wind Farm has enhanced the area, saying that the turbines are impressive looking and bring a calming effect to the town.[3]