Sections of the media and opponents of wind farms perpetuate many misleading myths about wind energy. It's important to be aware of the widespread misconceptions about wind farms — and be prepared to give a considered response when they are offered as objections to wind farm developments.
Main topics covered in this article include:
Wind turbines are audible but you can hold a normal conversation under a wind turbine operating at maximum speed, without raising your voice.
Wind farms in Australia are designed to meet strict noise regulations, introduced by state environmental protection agencies to protect the amenity of nearby residents. The regulations require that noise for proposed wind farms is modeled and meets specified 'acceptable' limits. This means that people living near wind farms might hear them at times, but what is heard will be within the regulated limits.
Sound is defined by its frequency (the pitch of the sound), measured in hertz (Hz) and pressure level (the 'loudness of the sound') which is measured in decibels (dB). People can generally hear frequencies between 20 Hz and 20,000 Hz and wind farms tend to generate sounds in this range. Wind farms make three main sounds:
- the ‘swoosh’ generated by the blade tip traveling through the air
- low frequency sound from gears and other mechanical movement
- small pressure pulses when the blades interact with wind flow around the tower.
Decibels are a logarithmic scale which means that a doubling of the perceived noise is equivalent to an increase of 10 dBA. This table shows a few different noise sources with associated noise levels. The levels here are indicative only. How you hear a noise is subjective and depends on background noises and other conditions.
|Noise source||Noise level (dBA)|
|Jet aircraft at 250m||140|
|Pneumatic drill at 7m||95|
|Truck at 50km/h at 100m||65|
|Conversation or busy general office||60|
|Car at 65km/h at 100m||55|
|Busy road at 5km||35-45|
|Wind turbine at 350m||35-45|
|Rural night-time background||20-40|
Dr Mark Diesendorf's book Greenhouse Solutions with Sustainable Energy (2007), chapter 6.
Compared to other human activities, wind farms have an extremely low impact on birds. Wind turbines do occasionally kill birds, but so do people, vehicles, houses, buildings, powerlines and communication towers — and in much greater numbers.
The National Wind Coordinating Committee's 2001 literature review of bird deaths resulting from collisions with vehicles and other man-made infrastructure in the US estimated annual bird deaths associated with various causes:
- vehicles: 60-80 million (different studies in different areas found between 2.7 and 96.3 bird deaths per mile of road each year)
- buildings and windows: 98-980 million
- powerlines: up to 174 million
- communications towers: 4-50 million
- wind farms: 10-40,000 (an average of 2.19 bird deaths per wind turbine per year in the US).
While extensive data is not yet available for wind farms in Australia, early results from bird monitoring at Codrington Wind Farm show an estimated bird mortality rate of 1.2 birds per turbine each year.
Other significant causes of bird deaths include house cats, pesticides, oil spills, electrocution and disease. A 2007 study by the Government of South Australia shows one domestic cat kills more birds in a year than one wind turbine.
When it comes to potential impacts on threatened bird species, wind farms have to go through a rigorous planning process to ensure any such risks are fully assessed before a project can go ahead.
It’s important to note, the presence of a threatened bird species in the vicinity of a proposed wind farm doesn't necessarily mean the wind farm will pose a direct threat. Assessing the risk to birds is complicated, and depends on:
- whether the bird species typically flies at rotor swept height — many birds rarely reach rotor swept height, which is approximately 60 m
- if the bird species would normally fly through the wind farm area
- how the wind turbines are spaced, and where they are in relation to habitat areas, such as waterways, breeding sites, foraging areas and flocking sites
- avoidance rates for the species
- the layout and design of the wind farm, and what avoidance, mitigation and management measures are in place.
National Wind Coordinating Committee's Avian Collisions with Wind Turbines: A Summary of Existing Studies and Comparisons to Other Sources of Avian Collision Mortality in the United States (2001)
Government of South Australia's Cats and Wildlife - how you can protect both (2007)
Using data from the International Energy Agency, the Guardian found that globally, subsidies to fossil fuels are 500% greater than for renewables Fossil fuel subsidies: a tour of the data.
In Australia, the reality is that most forms of large-scale electricity generation receive, or have received, some form of government subsidy.
Many coal and gas-fired generators in Australia were originally built by state governments with public money. This included the construction of hundreds of kilometres of transmission lines to carry electricity to population centres, or to industrial centres like the aluminium smelters in Portland, Victoria.
Furthermore, while many of these generators are now privately owned, coal-fired generators still receive de facto subsidies in that they don't pay for their greenhouse gas emissions or other environmental and health impacts. They also receive economic subsidies from government, for example, funding for coal railways and port facilities. In total, fossil fuels receive economic subsidies amounting to at least $10 billion per year in Australia.
Therefore, it's not surprising that all the cleaner alternatives to polluting fossil fuels, apart from energy efficiency and conservation, are more expensive than fossil fuels. Nevertheless, wind is one of the least-cost alternatives.
As the renewable energy industry is in early stages of development in Australia, federal and state governments have introduced measures to support the industry, given the long-term benefits to the community and the environment. Government schemes, such as the National Renewable Energy Target and state-based schemes like the Victorian Renewable Energy Target, require retailers to buy a certain percentage of renewable energy. This encourages development of the wind industry. Over time, as the markets for renewable energy sources grow, costs decline and their subsidies can be gradually decreased.
Dr Mark Diesendorf's book Greenhouse Solutions with Sustainable Energy (2007), chapter six.
C. Riedy's Report Energy and transport subsidies in Australia (2007 update), Report to Greenpeace Australia Pacific, Institute for Sustainable Futures, Sydney
Efficiency is a metric comparing energy output to energy input. When the input is a free and infinite fuel like the wind, the term 'efficiency' actually becomes irrelevant. A more meaningful term used to compare the output of one wind farm against another is 'capacity factor'.
Capacity factor is a ratio of how much energy a wind farm produces to how much energy it would produce if it operated at maximum output, 24 hours a day for the life of the wind farm. If a 1 MW wind turbine could theoretically produce 24 MWh in a day, but instead it generated 12 MWh because the wind was sometimes slow and occasionally calm, then you could say that for that day the wind turbine had a capacity factor of 50%.
To write that mathematically:
Capacity factor = P/M , where
P = actual amount of energy produced over time, and
M = energy that would have been produced if the wind energy facility had operated at maximum output 100% of the time.
A wind energy facility in Victoria will typically have a capacity factor of 30%, which compares favourably with wind farms in Europe and the United States.
Dr Mark Diesendorf's book Greenhouse Solutions with Sustainable Energy (2007), chapter six.
Internationally, there have been a handful of reports from wind farm opponents that turbines cause ‘wind turbine syndrome’, with wide-ranging symptoms including sleep disturbance, headaches, tinnitus, dizziness, vertigo, nausea, irritability, and problems with concentration and memory. The National Health and Medical Research Council's review of published scientific literature in 2010 found no published scientific evidence suggesting wind farms cause any pathological effects (that is, harm to the body or hearing).
The review looked into health concerns associated with infrasound (sound below the hearing threshold of most people). The review found no evidence to link wind turbine effects (including electromagnetic interference, shadow flicker and blade glint) with any adverse health effects. However, the review did say that noise from wind turbines has been linked with health and well-being effects such as annoyance, nuisance and dissatisfaction; as well as interference with activities like speech, sleep and learning. Also, it suggests that, "if people are worried about their health they may become anxious, causing stress-related illness”, meaning people may exhibit genuine symptoms that could have arisen because of a wind turbine, even though the turbine is not the direct health risk.
The National Health and Medical Research Council has committed to maintain a watching brief on the issue and will make a detailed literature review available on its website in mid 2012: National Health and Medical Research Council.
In contrast, existing coal-fired generators have significant effects on human health, as they emit:
- oxides of nitrogen and sulphur, and ntiric and suphuric acid — irritants that can cause respiratory illness, asthma, and even death
- particulates, which when inhaled can cause breathlessness and increase cardio-respiratory problems
- vapourised mercury, which accumulates in the environment and can appear in significant concentrations in fish at the top of the food chain, including tuna, shark, swordfish and mackerel, and in shellfish that accumulate mercury from the organisms they filter. Mercury is a particular problem for pregnant women and infants, as exposure to even low levels of mercury can cause developmental problems
- other toxins, such as boron and fluorides, and even low-level radioactivity.
NHMRC Release of NHMRC Public Statement: Wind Turbines and Health (2010)
Professor David Shearman's report: An energy policy for Australia: Doctors for the Environment Australia Appendix 1: Coal and gas - health effects (2006)
The Clean Energy Council's Report on Environmental Noise
'Wind energy and other renewable energy sources will never substitute coal-fired electricity in Australia because they cannot provide base-load (24-hour) electricity'
Large-scale, distributed wind energy, together with other renewable energy sources and energy efficiency measures can provide base-load power, with gas playing a transitional role.
'Base-load' describes the amount of electricity needed continuously — 24 hours a day, every day of the year. In simple terms it is the power needed for industrial processes and essential services (traffic lights, public transport, hospitals). Typical base-load power demand for Victoria is shown here:
The above image shows intermediate and peak demand periods, which result from changing levels of demand throughout the day. It's essential that electricity grids can meet these different demand periods using generators with suitable characteristics.
Base-load generators are able to provide continuous electricity at the level of overnight demand, but are too inflexible to follow fluctuations in demand and meet the daily peaks.
Intermediate-load generators run during the daytime and early evening, filling the gap between the base and peak-load generators.
Peak-load generators run for short periods each day to meet daily peaks in demand and to help back-up other generators when they break down.
In Australia, most base-load electricity demand is met by coal-fired generators, with a few gas-fired generators. However, as highlighted by Dr Mark Diesendorf in his 2010 paper, this base-load demand could be met by a range of renewable energy sources. A suggested mix for base-load power generation is:
- Bioenergy, based on the direct combustion of crop and plantation residues, or their gasification, followed by combustion of the gas.
- Geothermal power – a new type of geothermal power (called hot rock, enhanced or engineered geothermal) is being developed in Australia, the USA and Europe.
- Solar thermal electricity, with overnight thermal storage in molten salt, water, graphite or a thermochemical store such as ammonia.
- Hydro-electricity in regions with very large storage capabilities (e.g. Sweden, Iceland, Tasmania).
- Large-scale, geographically distributed wind power, with occasional back-up from peak-load generators.
A single wind turbine acts as an intermittent source of power, which varies according to wind speed. However, as the wind is usually blowing somewhere, if many wind farms are connected to the grid, dispersed in different wind regions, wind becomes a much more reliable source of electricity.
Replacing a 1,000 MW coal-fired power station, with an average annual output of about 850 MW, would require a group of wind farms with a combined rated power of about 2,600 MW.
Although this substitution would involve many wind turbines (for example, 1,300 turbines, each rated at 2 MW), the area of land actually occupied by turbines and access roads would only be 5 to 20 square km, depending upon wind speed. Farming continues between the wind turbines. In comparison, a coal-fired power station and its open-cut coal-mine may occupy over 50 square km.
Furthermore, as it's possible to predict wind reasonably accurately, only a small amount of peak-load generation such as gas or hydro would be needed to provide back-up, ensuring demand can be met.
It's also worth noting that coal isn't a completely reliable source of base-load electricity. Generators break down from time to time. Coal-fired generation is also affected by weather conditions and the availability of water, and coal-mines are susceptible to bushfire. As recently as 2009, there were significant power outages across Melbourne, due to a record heatwave and fires near Latrobe Valley power stations. With more days of extreme heat, diminishing water resources and a greater likelihood of fire in eastern Australia predicted as a result of climate change, coal-fired electricity is likely to become less reliable.
CSIRO's report on Climate variability, climate change and drought in eastern Australia (2010)
Dr Mark Diesendorf's article on The Base Load Fallacy and other Fallacies disseminated by Renewable Energy Deniers (2010)
Stewart Needham's research paper The potential for renewable energy to provide baseload power in Australia (2008)
Every megawatt-hour (MWh) generated by a wind farm in Australia displaces generation from fossil fuels. The level of GHG abatement varies for different states. In Victoria, a report by McLennan Magasanik Associates found that on average, every MWh of wind energy generated displaces one tonne of GHG emissions.
McLennan Magasanik Associates Assessment of Greenhouse Gas Abatement from Wind Farms in Victoria (2006)
Like any large infrastructure, a wind turbine's production and installation requires energy. However, one of the major benefits of renewable energy is that once a project is constructed, it will then generate energy for decades without the need for further resources other than those it captures and converts. This is in stark contrast to fossil fuel energy sources, which not only require a lot more energy to build in the first place, but also need a lot of energy to operate.
Wind turbines generate far more energy over their lifetime than it takes to build, install and decommission them. Turbine manufacturer Vestas did a lifecycle assessment for their V80-2.0 MW turbine model and found it would regenerate the entire amount of energy it consumed over its lifetime in just 7.7 months. At a high-wind site, this could be as short as three months.
Studies in the US and the UK have found no evidence to suggest wind farms decrease property values. While there haven't been broad scale studies into the impact of wind farms on surrounding property values in Australia, a study by Henderson and Horning on the Crookwell Wind Farm found no reduction in land or property values.
'Wind farm developers will walk away at the end of a project’s life leaving the landholders with the burden of removing the turbines and rehabilitating the site'
Wind farm lease agreements generally include a clause requiring the wind farm operator to decommission the wind farm at the end of its life, including removing all infrastructure and restoring the site to its original condition.
The perception that wind farms have adverse environmental impacts is partly due to wind power being a relatively new source of energy in Australia. This means it has to go through a rigorous modern planning process that usually includes a detailed environmental assessment. Many coal-fired generators were built before detailed planning processes were introduced, and before we had such an understanding of fossil fuel's impact on the environment.
The reality is, wind energy is one of the most environmentally friendly sources of electricity. Here's why:
- Wind farms generate electricity without consuming resources like water or fossil fuels.
- They emit no greenhouse gases or toxic gases whatsoever, during operations, and relatively little during construction. They have minimal impact on the local environment or nearby communities.
- Wind turbines recoup the energy used to build them within just a few months of operation, and yet they have an operational lifetime of at least 20 years. Compare this with fossil fuel generators, which consume non-renewable energy and resources throughout their operational lifetimes.
- Wind farms are usually installed on agricultural land that has previously been cleared of trees by farmers.
- Wind turbines can be built where they avoid environmental features such as waterways, native forests and cultural heritage sites — and have to meet strict noise regulations.
- The foundations for wind turbines generally have a very small physical footprint (an area of about 20 x 20 metres and up to about three metres deep). This means existing farming practices can and do continue around the turbines.
- While wind turbines may be tall and imposing, and some people may not like the look of them, their impact on the landscape isn't permanent. Wind turbines can be completely removed at the end of their lifetime, and the land returned to its previous state. What's more, most components can be recycled. In contrast, landscape changes in coal-mining areas can damage much larger land areas and are often permanent.
While foundation design depends on the site's ground conditions, a typical wind turbine has a foundation area of up to 20 x 20 metres in area (sometimes as little as 13 m), and up to three meters deep. The relatively small footprint means wind farms can usually exist alongside farming operations with very little impact.
Dr Mark Diesendorf's book Greenhouse Solutions with Sustainable Energy (2007), chapter six.
America Wind Energy Association and Canadian Wind Energy Association 'Wind turbine sound and health effects' , An expert panel review, December 2009
Colby, W. D. (2010), Presentation: Sound and Health
Diesendorf, Dr Mark, 'Greenhouse Solutions with Sustainable Energy', UNSW Press, 2007
Diesendorf, Dr Mark, 'Time to bust some myths about renewable energy', Crikey 2010
Environment Protection and Heritage Council, (EPHC), (2009). National Wind Farm Development Guidelines – Public Consultation Draft. Commonwealth of Australia, Adelaide.
European Wind Energy Association (EWEA) (2010), Wind Energy Factsheets
Frew, Wendy It’s an ill wind, Sydney Morning Herald 2006
Jakobsen J., (2005). Infrasound emission from wind turbines. Journal of Low Frequency Noise, Vibration and Active Control, 2005;24(3)
Leventhall, G. (2010), Presentation: Wind Turbine Syndrome – an Appraisal
Leventhall, G. (2004), Notes on Low Frequency Noise from Wind Turbines with special reference to the Genesis Power Ltd Proposal, near Waiuku NZ . Prepared for Genesis Power / Hegley Acoustic Consultants
Morton, Adam Turbine noise no health threat , The Age 2010
National Health and Medical Research council (NHMRC), (2010). Wind Turbines and Health – A Rapid Review of the Evidence
NHS 'Are wind farms a health risk?' , August 8 2009
Office of Energy Efficiency and Renewable Energy's report on The Impact of Wind Power Projects on Residential Property Values in the United States: A Multi-Site Hedonic Analysis