Australian wind farms can be expected to have an operating life of around 25 years.
I regularly drive past a local wind farm, and I often see a number of turbines that aren’t moving, even on a windy day.
A wind turbine may be stopped for a number of reasons:
1. The wind turbine could be undergoing scheduled maintenance to keep the turbines running smoothly. For safety reasons, our technicians make sure that the turbine is switched off before undertaking maintenance activities.
2. The wind turbines will stop automatically for a range of self-maintenance activities, including periodic greasing of the turbine, safety systems tests, and to unwind the power delivery cables at the top of the tower (a wind turbine can be turned around 3 times by the wind before it will automatically unwind itself).
3. The wind speed might not be high enough at that particular location for the turbine to run. Wind speeds can vary significantly, even across a single wind farm, so it is not uncommon to see some wind turbines operating, while others are stationary. On a calmer day the turbines may be seen to be only turning slowly or not at all but the turbine will be ready to generate as soon as wind conditions allow.
4. In very rare circumstances, turbines will stop operating in response to extreme weather conditions. For example, if the ambient temperature at hub height reaches 40 degrees celsius, the turbine automatically shuts down (when this occurs, the temperature at ground level is significantly higher, so this is a very rare event).
The amount of time that a wind farm is stopped for maintenance in a year is very small, and the availability of a wind farm to produce electricity typically exceeds 97% annually.
Visiting a wind farm can be an amazing experience. However, a wind farm is a commercial operating power plant, and while every effort is made during the design, construction and ongoing maintenance to ensure a wind farm is as safe as possible, there are still potential risks that must be actively managed, just like any work site.
Wind farms are generally located on private properties, and often co-exist with existing farming practices, such as grazing. The technicians working on a wind farm will be actively supporting these activities, such as keeping gates closed between paddocks, but someone who is not familiar with the farm operations may inadvertently have a negative impact.
To help local communities access information about wind farms, many projects include viewing platforms and visitor centres and displays.
In addition, there are periodic supervised tours of wind farms around Australia. If you are interested in visiting a wind farm, then it is a good idea to contact the wind farm owner to register your interest so that they can let you know when a wind farm tour is planned.
The Clean Energy Council coordinates a National Wind Farm Open Day. More information about this is available from the website, www.cleanenergycouncil.org.au
To get to the top of a turbine the technicians must climb an 80-metre ladder, or in the case of some turbines catch a small lift located inside the tower. As you can imagine, technicians make sure that they take all the tools they need with them, so that they don’t have to make the trip more than once!
Our technicians work on top of the turbine in all weather conditions. All technicians undergo extensive training about working safely at heights and are required to refresh this training every year.
The wind direction on a wind farm site can vary within a few hundred meters depending on the terrain.
When a wind farm is being designed, the shadow flicker effect over the course of a year is modelled to ensure that local amenity is not disturbed.
State planning laws have strict guidelines about shadow flicker. In some cases, to meet these strict planning conditions, and to protect local amenity,particular turbines can be programmed to turn off for a few hours a year when shadow flicker may be an issue.
The commercial three-bladed wind turbines in Australia today use mature technology based on decades of experience in other countries.
In the early days of wind farming, turbines were developed with 1, 2 and 4 blades. More blades mean that more of the energy in the wind can be captured, but there are diminishing returns and extra costs for each additional blade.
Three bladed turbines provide the best balance between efficiency, cost, and reliability.
The electricity from the wind farm is fed into the electricity network.
Wind turbines are generally painted a neutral colour to help minimise any impact on visual amenity. Our wind turbines are in fact painted a light grey colour. This is so they don’t appear too bright when the sun is shining, and blend into the background when it is overcast.
However, there are some communities that are keen to highlight wind turbines. In Victoria, the artist Ghostpatrol has painted beautiful murals on the turbine towers at the community-owned Hepburn Wind Farm.
Turbines use a very small amount of electricity to perform a range of functions, such as powering the control computer, and to maintain the correct temperature of various components such as the gearbox and generator.
The amount of electricity used is tiny. A typical Senvion turbine in Australia might use up to 16 megawatt-hours of electricity in a year. To put that in context, this is around one quarter of one percent of the energy produced.
Thermal power stations use a lot more electricity relative to the energy they produce. For example, 10% of electricity produced by the Hazelwood Power Station in Victoria is used within the power station as part of the electricity generating process.
The planning permit conditions for a wind farm include consideration about what happens at the end of its life. For example, a condition might require the wind farm owner return a site to its preconstruction condition within 12-months of decommissioning.
Compared to most other forms of power generation, wind farms have a very small impact on the land they occupy, and remediation is a relatively straightforward process.
The value of the materials in a wind farm, such as the steel in the towers, would cover the costs of remediation, so bank guarantees are not necessary.
This will depend on the turbine, but typically wind speeds need to be around 3 to 4 metres per second for a wind turbine to start producing electricity.
Wind turbines are designed to shut down as a protection mechanism under extraordinary circumstances, such as unusually high wind speeds. However, the maximum wind speed that a turbine can withstand will vary between different turbine designs.
When designing a wind farm, the wind speeds at that site dictate what sort of turbine is installed in that location. If a site were expected to consistently experience very high wind speeds, than a turbine that is designed for those conditions would be selected.
The following graph shows the power curve for a MM92 turbine, part of the Senvion product range.
This graph shows how the power output increases with wind speeds up to around 10 metres per second where the maximum output is reached. The graph also shows that the turbine will stop operating automatically at wind speeds of 22 metres per second or higher to protect the equipment.
Wind turbines store a very small amount of electricity to support integration with the electricity network. Some turbine manufacturers are looking at the potential for storing more power – but this is not commercially available at the moment.
A typical turbine will have a maximum RPM of around 20 revolutions per minute (or 1 revolution every 3 seconds). When you see a wind turbine operating, the blades do not appear to rotate quickly – but because the blades are so long (eg 92 metres for Senvion Australia’s 2.05 megawatt MM92), the tip speed is very fast and can reach speeds of over 250 kilometres an hour.
Detailed wind monitoring determines the location of individual wind turbines. Turbulence can affect the operation of a wind turbine, so the impact of each turbine on the airflow is modelled when siting turbines. The distance between turbines will therefore vary depending on the prevalent wind direction and the topography of the site. Generally, the distance between turbines would be the equivalent of around 5 rotor diameters in line with the prevailing wind direction.
A nacelle is the cover that houses all of the generating components in a wind turbine, such as the generator, gearbox and drive shaft.
The wind turbines used in commercial wind farms in Australia are not suitable for built up areas as nearby buildings can create turbulence which can affect the effective operation of a turbine.
There are, however, other wind energy technologies that are being applied in cities. For example, the ANZ centre in Melbourne’s Docklands has a row of roof-mounted wind turbines, and the Eiffel Tower in Paris now includes two operating wind turbines.
A typical 2-megawatt wind turbine can provide enough electricity to power around 1,000 homes.
Wind farms deliver local job opportunities during the construction of a project, and to support its ongoing operation.
The Clean Energy Council has undertaken an analysis of the direct and indirect employment benefits of a typical 50-megawatt wind farm, which is summarised in the following table.
Wind farms deliver a range of opportunities for local businesses, such as accommodation and food service providers, domestic electricians,transport operators, machine operators, quarries and concrete businesses.
Women can and do work as wind technicians, although, like the electrical trades more broadly, only a small percentage of wind technicians are female.
When recruiting for wind farm technicians we are looking for people with a background in mechanical or electrical/electronic trades. With these skills, individuals can be readily trained in wind power mechanical and electrical systems in order to undertake maintenance.
Local transport companies, earthmoving contractors, hotels, restaurants, and other service industries can all benefit from the construction and operation of the wind farm.
Analysis by the Clean Energy Council found that for a typical 50-megawatt wind farm:
A study undertaken by Sinclair Knight Mertz (SKM) for AGL has estimated that construction of the four existing Hallett wind farms in South Australia added an equivalent of 1.15% to the Gross Regional Product of the Mid North Region.
Wind farms must meet stringent noise standards. Typically the noise from a wind farm at a residence must not exceed around 35 – 40 dB, which is the equivalent of a quiet room.
Solar panels work best when they are angled to face the sun, for example on rooftops.
The National Health and Medical Research Council (NHMRC) is Australia's peak body for developing health advice for the Australian community.
In its 2010 report, ‘Wind Turbines and Health: A rapid review of the evidence’ the NHMRC found that:
"There are no direct pathological effects from wind farms and any potential impact on humans can be minimised by following existing planning guidelines."
In its subsequent ‘Public Statement on Wind Farms and Health’ released in August 2011, the NHMRC stated:
"There is currently no published scientific evidence to positively link wind turbines with adverse health effects."
Most recently, in its ‘2015 NHMRC Statement and Information Paper: Evidence on Wind Farms and Human Health’ the NHMRC stated:
“After careful consideration and deliberation of the body of evidence, NHMRC concludes that there is currently no consistent evidence that wind farms cause adverse health effects in humans.”
The NHMRC has stated that, within 1,500 metres, high quality research into possible health effects of wind farms is warranted given the concern expressed by some members of the community and the poor quality of current evidence.
The Health Canada Wind Turbine Noise and Health Study is a significant international research project that commenced in 2012. This study is not complete, so was not included in the NHMRC work. The Health Canada study looked at the experience of over 1,200 households living near wind turbines. Preliminary results indicate that sleep disorders and illnesses are not linked to exposure to wind turbines.
Around Australia, strict standards for wind farm developments must be met, ensuring that wind farms do not pose a risk to health in terms of noise, shadow flicker, blade glint and electromagnetic fields.
Wind turbines are responsible for very few bird deaths. It is estimated that for every 10,000 bird fatalities, less than 1 is caused by wind turbines. By comparison, over 70% of bird deaths are due to collisions with buildings and power lines, with domestic cats responsible for a further 10%.
In order to receive planning approval in Australia, a wind farm developer must:
Once a wind farm is built, the wind farm owner is responsible for ongoing monitoring of the impact of the wind farm on bird species, and any bird deaths must be recorded.
If threatened or endangered birds and bat species do live around or migrate through a wind farm, very stringent regulation applies to ensure that any impacts are minimal. Many wind farm operators are required to implement a monitoring program during key times such as migration or breeding to oversee potential issues.
Senvion Australia builds community-scale and commercial-scale wind farms, which are not suitable for an individual’s back yard.
However, there are small wind generators available that are specifically designed for domestic use.
Sustainability Victoria has developed a Consumer Guide to Small Wind. Turbine Generation (2010) which is available from its website, www.sustainability.vic.gov.au
Wind turbines are not a fire hazard.
Wind turbines have a variety of on-board control systems that have been specifically designed to mitigate the risk of fire.
Fire Management Plans (FMPs) are developed for all Australian wind farms and apply to both construction and operational phases of projects. A FMP requires project proponents to record all potential project-related bushfire risks and establish specific management strategies to address these risks. For example, the plan may require only diesel-fuelled cars on wind farm sites prior to the construction of roads to mitigate the risk of grass fires from petrol vehicles. Contingency plans are also developed for situations of increased fire risk, such as total fire ban days, and if there are bushfires in the vicinity of the wind farm.
Statutory planning permits also mandate certain management practices. For example, at the Oaklands Hill Wind Farm in Victoria, a planning permit condition required water tanks to be installed on site for use in the event of a fire.
The planning permit also required the wind farm to determine a series of Emergency Services Procedures in consultation with a range of parties, including the Country Fire Authority, Police and Local Council. These procedures apply from the time when the wind farm first begins generating all the way through to decommissioning.
Wind farm projects generally require upgrades to existing road infrastructure, increasing the accessibility of farms to emergency vehicles should a bushfire break out in the vicinity of the wind farm.
The CFA’s Emergency Management Guidelines for Wind Farms (2007) notes that the potential for fire from wind turbines is inherently low.
The risk of fire starting as a result of a lighting strike is actually reduced by the presence of wind turbines. Although they attract lightning, WTGs are designed to safely channel lightening to the ground. A built-in lightning protection system safely dissipates the electricity from the blades or the nacelle into the ground.