What is a wind turbine?
A wind turbine 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; it is usually 13m across and 1-2m deep. 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 includes 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 44 metres.
What are wind turbines made of?
The towers are mostly tubular and made of steel or concrete, generally painted white. The blades are made of glass-fibre reinforced polyester. They are white because it is inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.
How does a wind turbine generate electricity?
The wind passes over the blades creating lift, which causes the rotor to turn. The blades turn a low-speed shaft inside the nacelle: gears connect the low speed shaft of the rotor with a high speed shaft that drives a generator. Here, the slow rotation speed of the blades is increased to the high speed of generator revolution. The rapidly spinning shaft drives the generator to produce electric energy. Electricity from the generator passes through to a transformer which converts it to the correct voltage for the distribution system. The electricity is then transmitted via the electricity network.
How much electricity does a wind turbine generate?
The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor. Wind turbines manufactured today have power ratings ranging from 250 watts to 7 MW.
What is the wind?
The Earth is surrounded by the atmosphere, which is made up of air. Air is a mixture of gas, and solid and liquid particles. Energy from the sun heats up the atmosphere and the Earth unevenly. Cold air contains more air particles than warm air. Cold air is therefore heavier and sinks down through the atmosphere, creating high pressure areas. Warm air rises through the atmosphere, creating low pressure areas. The air tries to balance out the low and high pressure areas – air particles move from areas of high pressure (cold air) to areas of low pressure (warm air). This movement of air is known as the wind.
The wind is also influenced by the movement of the Earth. As it turns on its axis the air does not travel directly from areas of higher pressure to areas of lower pressure. 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.
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.
How can wind be measured?
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. The wind direction is measured with weather vanes.
After measuring wind data for at least one year, the mean annual wind speed can be correlated to a long-term reference point to calculate mean wind speed. Wind speed and wind direction statistics are visualised in a wind rose, showing the statistical repartition of wind speed per direction.
Wind source maps 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.
How fast do the blades turn?
The blades rotate at anything between 15-20 revolutions per minute at constant speed.
How long does a wind turbine work for?
Wind turbines can carry on generating electricity for 20-25 years. Over their lifetime they will be running continuously for as much as 120,000 hours. After this time they may be refurbished.
What are a wind turbine's lifetime emissions?
According to theEuropean Wind Energy Association,it takes a turbine just three to six months to produce the amount of energy that goes into its manufacture, installation, operation, maintenance and decommissioning after its 20-25 year lifetime. During its lifetime a wind turbine delivers up to 80 times more energy than is used in its production, maintenance and scrapping. Wind energy has the lowest ‘lifecycle emissions’ of all energy production technologies.
By directly reducing the use of fossil fuels, wind energy significantly reduces emissions of the greenhouse gas carbon dioxide and other harmful pollutants. A number of detailed power system studies, as well as real-world experience with wind plants, have demonstrated that wind energy significantly reduces fossil fuel use and emissions. The outcomes of these studies are listed on the website of the American Wind Energy Associationhere.
How are wind farms designed?
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. The turbines need to be easily accessible for maintenance and repair work when needed.
Noise levels can be calculated so the wind farm is compatible with the levels of sound stipulated in relevant 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. This depends on the wind conditions and landscape features of the location, local/national rules such as on turbine height, noise levels and nature conservation, the risk of extreme events such as earthquakes, how easy it is to transport the turbines to the site and the local availability of cranes.
For acoustic studies conducted in wind farms in Australia, please review the study* conducted by Sonus Pty Ltd, an acoustic consulting firm, which found that "the infrasound generated by wind turbines is well below established guideline perception thresholds".
* "Infrasound Measurement from Wind Farms and Other Sources" Prepared for Pacific Hydro LTD, Sonus Pty LTD, November 2010.
How long does it take to construct a wind farm?
Construction time is relatively short – a 10 MW wind farm can easily be built in two months. A larger 50 MW wind farm can be ready in 18 months to three years. It takes 2-3 years to develop, and 1-2 years to build.
Why do turbines sometimes stand still?
There are a number of reasons why turbines are not always spinning:
- Turbines have to be stopped for scheduled maintenance, for repairing components or if there is a failure that needs to be checked.
- Another reason can be too little or too much wind: if the wind is too strong, the turbine needs to be shut down because it could be damaged.
- When electricity demand is low, then electricity from wind turbines is not needed and they switch off.
What are the environmental benefits of wind energy?
Wind energy emits no toxic substances such as mercury and air pollutants like smog-creating nitrogen oxides, acid rain-forming sulphur dioxide and particulate deposits. These pollutants can trigger cancer, heart disease, asthma and other respiratory diseases, can acidify terrestrial and aquatic ecosystems, and corrode buildings. Wind energy creates no radioactive waste or water pollution.
How is electricity transported?
It is important to distinguish between the financial aspects and the physical National Electricity Market. The flow of electricity around the network does not care about contracts. Electricity transportation is governed by physical laws.
When an appliance is switched on, power is instantly transmitted from a power station to the appliance. Although this occurs instantaneously, a specific sequence of events takes place to ensure the delivery of the required electricity.
Electricity often travels long distances to reach the point where it is required because the sites where electricity is generated are often in remote areas where cheap fuel resources are abundant. During the transportation process, a percentage of electricity is always lost through electrical resistance, which heats up electrical equipment (such as conductors and transformers) along the way. To reduce the amount of electricity lost, a transformer at the generating plant converts the electricity from low to high voltage (which is more efficient way to transport large amounts of electricity). Transmission lines then transport bulk supplies of power from generating sites to locations closer to consumers.
At these locations, a substation transformer converts the high voltage electricity to lower voltage for distribution. Distribution lines carry low voltage electricity to consumers who access it through the power outlets in homes, offices and factories. The distribution network has more power line than the transmission network. This is because transmission lines can carry a large anount of power that will then require many distribution lines to take to consumers.
What is the grid and how does it work?
Electricity is distributed to the consumers via the grid – the physical infrastructure of the electricity network. The grid is made up of transmission and distribution networks. The transmission network – made up of the cables and pylons you see dotting the countryside – moves electrical power with a high voltage over long distances, and sometimes across international boundaries. The consumers are connected to the distribution system, which has a medium voltage level.
What is a substation?
The substation is the link between the transmission and distribution network, where the power is stepped down in voltage from the transmission to the distribution level. Once it reaches its final destination, the power is stepped down again to the required local level.
Are wind turbines noisy?
The noise of wind turbines has been reduced significantly with newer technologies. Improved design has drastically reduced the noise of mechanical components so that the most audible sound is that of the wind interacting with the rotor blades. This is similar to a light swishing sound, and much quieter than other types of modern-day equipment. Even in generally quiet rural areas, the sound of the blowing wind is often louder than the turbines.
What is infrasound?
Infrasound is a term used to refer to "acoustic oscillations whose frequency is below the low frequency limit of audible sound"*. Audible noise is a term used to refer to the frequency range between 20 to 200 Herz, however, audibility extends to frequencies below 20 Herz**.
* "International Electrotechnical Vocabulary - Chapter 801: Acoustics and Electroacoustics", International Standard IEC 60050-801:1994, International Electrotechnical Commission, (1994).
** O'Neal, R., Hellweg, R. D. Jr & Lampeter, R. M., "Low Frequency Noise and Infrasound from Wind Turbines", Noise Control Engineering Journal J. 59 (2), March-April 2011.
Do wind turbines harm human health?
Wind energy is one of the cleanest, most environmentally-friendly energy sources. It emits no greenhouse gases or air pollutants. It emits no particles, unlike fossil fuels, which are carcinogenic and severely affect human health.
According to the public statement made by the National Health and Medical Research Council in Australia, "there is currently no published scientific evidence to positively link wind turbines with adverse health effects"*.
* Wind Turbines and Health, NHRMC Public Statement, July 2010
Do wind turbines harm animals and birds?
Big environmental and nature conservation groups like WWF, Greenpeace, Friends of the Earth, and Birdlife support wind energy. Wind farms are always subject to an environmental impact assessment to ensure that their potential effect on the immediate surroundings, including fauna and flora, are carefully considered before construction is allowed to start. Deaths from birds flying into wind turbines represent only a small fraction of those caused by other human-related sources such as airplanes and buildings.
Renewable Energy Target (RET)
What is the RET?
Australia has a target to source 20 per cent of our electricity from renewable sources by the year 2020. The Renewable Energy Target (RET) was developed to drive the deployment of at least 41,000 GWh of renewable electricity by 2020 to meet the 20 per cent target.
Why do we need the RET?
Diversifying Australia's power sources
The RET is transforming our energy sector by diversifying Australia's sources of power. In 2012 more than 13 per cent of Australia's total electricity was generated by renewable energy. This means less reliance on gas that is getting more and more expensive as overseas demand grows.
More than two million small-scale energy systems have been installed across Australia, including more than one million rooftops with solar panels. This is helping Australian households take charge of their own energy bills.
Future cost of gas
Without renewables, Australia would be more reliant on gas – whichthe Australian Industry Grouppredicts will triple in price this decade. The impact of gas price rises is already being felt in Queensland, where the Queensland Competition Authority recently reported that the biggest driver of increasing energy prices is the development and demand for gas, as well as higher prices for gas used for electricity generation.
Meeting Australia's emissions reductions target
Meeting Australia's international commitment to reduce its carbon emissions by five per cent on 2000 levels by 2020 will be harder and more expensive to meet without a RET.
What is the cost of the RET?
The RET currently only contributes between 3 and 5 per cent (depending on which Australian state you're in) to the average household power bill.
In New South Wales, theIndependent Pricing and Regulatory Tribunalhas confirmed the cost of the RET is only about 5 per cent of a $2,129 average annual bill. That equates to $107 per year. This a relatively small cost per household when you consider the thousands of jobs and billions of dollars of investment provided by renewable energy.
In Queensland, the state'sCompetition Authorityhas found the RET will cost the average household less than $50 per year – about 3.5 per cent of the total bill. This is a relatively small cost per household when you consider the thousands of jobs and billions of dollars of investment provided by renewable energy.
The cost that the RET contributes to the average household bill is small compared to other contributors – for example, 41 per cent pays for network charges including maintaining poles and wires. This is forecast to increase to 43 per cent by 2020.
The RET reduces wholesale power prices because it encourages more competition in the energy sector.
How much renewable energy capacity has been installed as a result of the RET?
The RET has resulted in more than 14,000 megawatts of capacity being injected into Australia's energy system and renewables now provide more than 13 per cent of Australia’s total energy supply.
More renewable energy means less reliance on gas that is forecast to triple in price by this decade, according to a report by the Australian Industry Group.
How much investment has RET generated?
The RET has generated $18.5 billion of investment, and if left alone to do its job under stable policy settings is projected to generate a further $18.7 billion to 2030. Much of this investment is in rural and regional areas.
How many jobs has the RET created?
The RET has generated some 30,000 jobs, and is forecast to generate 30,000 more if it's given the stable policy settings it needs to do its job.
What is the environmental impact of the RET?
Carbon emissions are 22.5 megatonnes lower as a result of the RET. Without the RET, Australia would not have met its emissions reduction target under the Kyoto protocol.
What is the RET review?
The Federal Government has confirmed that the review of the RET will commence in early 2014, with a particular focus on the level of the target and its impact on electricity prices. Recent comments from some members of the Federal Coalition and various advisors and stakeholders reveal a concerning call for the RET to be wound back or removed altogether. This presents a real risk to the industry and warrants a concerted effort to defend the policy at the heart of the clean energy sector.
The industry is united in its view that much greater clarity on the future policy settings of the RET is required. This involves ending the continual cycle of reviews and ensuring the scheme can provide long-term and stable investment-grade policy support for renewable energy.
The results of the most recent RET review were released by theClimate Change Authorityin December 2012. You can view these on their websitehere.