The author is not beholden to any company, lobby group, or government. *
This page was previously a part of Wind Power in Australia;
and was created as a separate page 2008/08/26, modified 2014/07/22
About these pages – Google search Ramblings
Contact: email firstname.lastname@example.org
What follows is an independent point of view written by someone with no reason to either gloss over, or exaggerate, the problems and limitations of wind turbines and wind farms.
Sadly, in my experience many who are opposed to wind farms are woefully ill-informed and are not above lying or using facts in a misleading way to try to gain public support for their stance; many of them share with creationists and climate science deniers a willingness to twist the truth and ignore inconvenient evidence. And they are usually motivated by selfish and short-sighted desires including looking after their finacial backers in the case of many politicians, or chasing short-term financial gain in the case of the bosses of the fossil fuel industry. What they seem to forget (or just ignore) is that it is to all our advantages to take serious action to reduce our greenhouse gas production.
On the other hand it is true that some wind farm companies have acted unethically at times, with insufficient consideration for the people who are going to be living near wind farms at other times, and they generally emphasize the advantages and down-play the disadvantages of wind turbines.
A balance is needed.
If any reader believes that something on this page is wrong I'd be pleased to hear reasons and read supporting evidence; my email address is above. I started this page in 2008 and to the present (April 2013) while many people have provided helpful ideas for improvements and additions, no-one has pointed out any serious errors.
The problems that wind farms cause should be balanced against the problems that will arise if we do not build wind farms; greenhouse/climate change and ocean acidification will cause incomparably more environmental damage than wind farms do, and fire hazards, health problems and bird mortality will all be greater without wind farms. I have written a bit on the benefits of wind power and on the pros and cons of various methods of generating electricity elsewhere.
The reality is that our life-style in the early twenty-first century requires huge amounts of energy and wind turbines are one of the least environmentally harmful ways of generating electricity. Obviously wind turbines need to be built where the wind blows reliably and strongly. Perhaps those tempted to object to wind farms should consider whether they would prefer a coal-fired or nuclear power station nearby?
It is imperative that we greatly reduce our totally unsustainable rates of greenhouse gas production. Society is certainly not willing to give up private cars, air conditioning, computers, television, refrigeration, and all the other energy consuming equipment of the modern life-style (see What should be done), so we must build sustainable energy supply systems.
Wind turbines are very conspicuous; they have to be. They have to be built in windy places; this usually means either on the top of a ridge or close to the coast, perhaps both. They are very tall. Being tall and on top of ridge-lines means that they will quite probably be visible from forty or fifty kilometres, and the fact that they are moving most of the time only makes them more inclined to catch the observer's attention. Anyone who takes a disliking to them will be frequently reminded of their presence.
It is also reasonable for people to object to a new source of noise.
Community-owned wind farms are
much more common in Denmark than in Australia
and experience seems to show that some degree of ownership makes people
much more accepting of nearby wind turbines.
It will be interesting to see how the local acceptance of the community-owned
wind farms at Mount Barker
in WA and Hepburn in Victoria
(Especially in the latter, because it has many more share-holders and
surrounding area is much more densely occupied.)
This subject is further covered under
Generally popular, locally opposed.
The benefits of wind power are discussed in
Why support wind power.
I have discussed people's
supporting or opposing wind power developments elsewhere on this page, and
attitude to wind turbines in relation
to unsubstantiated claims of ill-health due to wind turbines on another
Noise problemsTurbines can, under some circumstances be heard at distances at least as great as 2.5km. While the sound is not loud, some people find it annoying, and at smaller distances (perhaps 1km or less) it may stop some people from sleeping and lead on to anxiety and stress in some people; this, in turn, can lead to health problems.
Power availability and transmission problemsThe wind does not blow all the time. When the wind is not blowing wind turbines do not generate power. At times of peak electricity demand winds tend to be lighter than average.
When any type of generation is not in the same place as consumption there is the need to transmit the power from one place to another. This requires very expensive high capacity, high voltage, transmission lines. For example, South Australia has much more wind power per capita than other states; if wind generation is high and consumption is low in SA then the power must be sent interstate.
Trust Power have offered a financial solution for this at their proposed Palmer Wind Farm in South Australia. They are offering annual cash payments to nearby residents. Another, perhaps preferable, arrangement would be a gift of shares in the wind farm, as then the receiver would have an interest in the running and profitability of the wind farm.
Of course, even without the sort of direct benefit Trust Power are talking about the neighbouring people may benifit indirectly, for example by the community funding that most wind power developers set up, or from contracting or employment etcetera, but there has not generally been a good balance of financial advantage in the immediate vicinity of a wind farm.
Invasion of space problemsSome people move to country areas because of the relatively undeveloped feel of the place. Others have lived in an area for a long time and have developed a feeling of attachment to the place as it is and understandably might not think it will be improved by a row of wind turbines on nearby hills.
Aesthetic problemsThis is related to the invasion of space problem above. Some people like the look of wind turbines, others hate them; it is a matter of personal preference – 'beauty is in the eye of the beholder'.
The life of a wind turbine is expected to be around 25 years. What happens to it when it reaches the end of its useful life? Some wind farms in the USA have simply been abandoned, leaving broken and rusting towers in conspicuous positions. (No wind farm has ever been abandoned in Australia.)
Environmental problemsThere are a number of environmental concerns that are perfectly valid. Wind turbines do kill some birds and there are problems involved with the necessary distruction of remnant native vegetation and possible erosion problems connected with the building of roads and hardstands. It seems that wind turbines kill a worrying number of bats, but there is a lack of research on this; birds are pretty and visible, bats are rarely seen and are not 'cute and cuddly'. great many other industries) use magnets based on a group of elements called rare earths; the mining of rare earth minerals in third world countries has been carried out with little concern for environmental damage. Much of the world's rare earths come from China, see the Guardian Weekly for a description of some of the environmental damage there.
Problems to do with poor practice
Social disruptionSometimes, when a wind farm is proposed, comunities are split into supporters and opponents. Occasionally bad feeling arises. In my experience this is more often due to people spreading misinformation about wind farms than being due to the wind farms themselves. For example, there has been no social disruption due to the Clements Gap and Snowtown wind farms (both near my home) because there was no vocal opposition.
Other problemsWind turbines can cause problems with television reception and cause interference to radar installations. Shadow flicker can be annoying when the shadow of moving turbine blades fall on a house at certain times of the day and year. Wind turbines limit where aircraft can go and this can pose problems for agricultural aircraft services. Fires in wind turbines, while rare, are very difficult to fight.
Finally, we must consider where we are going to get our energy if we do not build sustainable energy infrastructure such as wind farms. Very few people will be willing to get by with substantially less energy and using fossil fuels or nuclear power comes with far more problems than does wind power. We must do all we can to slow climate change. "You cannot make an omelet without breaking eggs."
single problem Man has faced to now.
The Australian Electricity Generation Report 2008 from The Climate Group stated that South Australia was the only eastern state to reduce its greenhouse gas production in that year (a fall of 6%); this was mainly thanks to wind power taking the place of some of the fossil-fuelled generation. More recent reports, including one in 2011 by the Australian Energy Market Operator (AEMO) showed that this trend has continued.
Our society must not confine itself to building wind farms, we must also:
Substantially increasing the price of energy would probably be the simplest and most efficient (but difficult to sell politically) way of achieving most of the above points.
In the Ballarat hearing of the Senate inquiry into the impact of wind farms on land values (2011/03/28) Councillor David Clark of the Pyrenees Shire Council said:
"We did a revaluation in early 2010, so six months after Waubra wind farm was operating. We did not see an effect on commercial agricultural land. It had moved up and our belief is there were other factors driving the price of that. We did not see an effect on the nearby township of Waubra. Prices again had moved up in the case of that township, which is about 1.2 to 1.5 kilometres away."Two years later, in the Pyrenees Shire Council Meeting Minutes, General Revaluation of Properties, 2012; of ten areas listed under 'Residentual Properties' Waubra shows the largest rise, 10.1%. The average change of the remaining nine areas was a rise of 2.9%. The valuations are done every two years.
If people are being driven from their homes by the Waubra Wind Farm one would expect a big decline in land values; the fact of the matter is quite the opposite.
The greatest distance from which I have ever definitely heard turbines is 3 km, and then only once and in ideal conditions. I have visited Waterloo township about ten times while the turbines were operating and have never heard the turbines from the township.
So how could turbine noise be driving people from houses at such a distance that the residents would rarely hear the turbines, even when they were outside? Could it be that people were moving out of Waterloo because they wanted to live in a larger town with more services (there are no shops in Waterloo)?
This also relates to the question of Land values and wind farms; plainly, if a house truly had been abandoned due to noise nuisance, its value on the market will drop substantially.
There are many small towns in Australia, so it happens that wind farms
will often be within a few kilometres of a small town.
There may well be special factors involved in the vacant houses at Waterloo; perhaps these have nothing to do with the wind farm?
At the Clare hearing of the Parliamentary Committee on Wind Farms, a wind farm opponent, John Faint, was asked "Are there likely to be factors other than the wind farm that have led to the decline of the local population?" (Question No. 886) He answered:
"No. Farms have become bigger, so if the farms have been sold they are usually bought by the neighbours, so families are lost that way. That is probably common all over the state. But the only other industry in Waterloo has been a quarry. That employed a few locals, but that has been leased out to a company called Fulton Hogan, and they are not operating there at the moment because they are a big company and they go where the work is. There is probably one permanent person there and a casual, and there would have been perhaps 20 people there at one stage. That would have helped the local community, but that is probably it, the main thing. However, as I said, the wind farm has not created any [jobs]."Previously (question No. 818), another wind farm opponent, Ms Wanda Allott, had said:
"When I first moved there [Waterloo] virtually every second house was empty. After five years virtually every house was full. ... The wind farm comes and within six months people are leaving. ... and now the town is virtually empty again."The Waterloo houses could well have filled because of jobs at the quarry (Mr Faint said that it was the only industry other than farms). And Mr Faint said that the quarry jobs had disappeared; isn't it very likely that that is why people have left Waterloo? (Of course Mr Faint is wrong to say that the wind farm has not created any jobs. There are a number of people employed in operation and maintenance.)
I went to the Waterloo wind farm on the evening of 2012/02/10 and set up my swag beneath one of the turbines. The number of kangaroos on the ridge impressed me; I must have seen at least eight, including a small joey. I also saw a pair of wedge-tailed eagles circling near the turbines. All were apparently in good health.
The wind varied from a moderate to a stiff breeze, so the turbines were operating all night. While I could plainly hear the turbines whenever I woke at night, I had no problem at all in getting a good night's sleep. Right at the foot of the turbine the sound of the turbine gear-box dominated the sound of the blades as they passed through the air. I noticed that when I moved away 100m or more all I could hear was sounds of the blades.
When passing through Waterloo in the evening I stopped my car and listened for the turbines. I could not hear them. The breeze in the nearby trees was making a fair amount of sound. In the morning I again passed through Waterloo and stopped. There was still a stiff breeze on the ridge where the turbines were, but very little air movement in Waterloo. I thought I might just be able to hear the turbines, but could not be sure.
Some people might well find the sound of turbines annoying and, if they were very close to the turbines, I could believe that they might be, unlike me, kept awake by the sound; but I totally fail to understand how people could find turbine sounds objectionable at distances of several kilometres.
Natural justice demands that people whose amenity has been impacted by noise or some other problem to do with turbines should receive some sort of compensation. But if one person is compensated, how do you stop others who may be similarly placed in relation to turbines, but not have any real problems with them, jumping on the band-wagon and demanding similar compensation just because they think they can get it? How do you treat people who might honestly, but erroneously, believe their health has been impacted by wind turbines? Leave it to the courts?
The power given to Victorian householders to veto any proposed turbine within 2 km is not an answer because all the power is with the householder and none with the wind farm builder; there must be a balance. Many people live perfectly happily with wind turbines much closer than 2 km.
Should compensation be based on recorded noise levels, the difference between ambient noise and wind turbine noise, or something else? Ideally, it should depend on the true impact on the individual; but how to measure that?
There was very little, if any, social conflict associated with wind farm construction in Australia until about 2008; around the time that the anti-wind farm lobby started to become active.
Is it the wind farms, or some inept wind farm developers who get on the wrong side of the local people, or even unethical wind farm developers; or is it wind farm opponents, or is it those who tell lies about wind farms and wind energy, or even climate change deniers – who deny that there is any need to change to renewable energy at all – who cause social conflict?
I emailed Frank Brennan, CEO of the Wattle Range Council where both the Canunda and Lake Bonney wind farms have been built (the latter being the biggest in the country as of mid 2008). He replied "There has been no 'significant and long-standing social conflict' from the lake Bonney or Canunda Windfarm developments – to the contrary there has been significant local community support for these projects."
The Central Western Daily (Orange) reported on 2011/12/05 that Blayney mayor Bruce Kingham stated that "In the 11 years since the [Blayney] wind farm [was built], we have had not one complaint".
At the sod-turning ceremony, Snowtown Wind Farm Stage 2, on 2012/10/25, Mayor of Wakefield Plains Council, James Maitland, said that he "was not aware of any negativity" regarding the project.
Clements Gap Wind Farm, 15 km from my home, has not caused any social conflict that I know of.
So, there have been a number of wind farms built without social conflict. Social conflict only happens when people oppose wind farm projects and opposition often arises in response to misinformation about wind power.
The arguments for and against proposed wind farms do, no doubt, cause enmities. This is unfortunate, but probably unavoidable; many people see wind turbines as a part of the answer to the greenhouse/climate change problem, others see them as a blight on the landscape. The fact is that any industrial development, especially a conspicuous one, is likely to lead to disagreement in some cases.
Disagreement is not conflict. People within a community have always disagreed about many things. So long as the discussion is rational and unemotional there is no need for real conflict.
Climate change is the greatest environmental and ethical challenge to
21st century society; changing from fossil fuels to renewable energy is one
of the actions that is essential to combating climate change.
I can accept that some people don't like wind turbines on aesthitic grounds,
I agree that there are some
genuine and valid problems with
wind farms; but I refuse to turn a blind eye to people who tell lies about
The neighbours who do not have a direct share in the largess must, at least in some cases, feel that they are having to accept the visual impact, sometimes hear the turbines, and even believe that their health is being impacted, while gaining nothing.
In many cases the whole community benefits, due to jobs, work for contractors, accommodation demand, not to mention community funds, but these may not be seen as benefiting those neighbours who see themselves as missing out.
A specific case in which envy seems to be a major factor in the development of opposition to a wind farm is the Ceres Project on SA's Yorke Peninsula, where some potential turbine hosts demanded more money than the proponent was willing to pay. After they were passed over they had a big part in setting up the opposition group Heartland Farmers.
Ignorance of the facts of wind power is obvious in many wind power opponents. For example, I have read from opponents several times that wind farm construction uses huge amounts of water; this is not true, but it is difficult to get actual water consumption figures from wind farmers.
The companies that do the earth works for wind farms seem even less comunicative than the wind farmers themselves.
Those companies that make little or no effort to inform Australians on the facts about the wind farms that they are proposing, and wind power in general, are doing a disservice to informed discussion and, in the long run, are letting down their industry.
Several of those people in the wind industry who have provided information for these pages have done so on the condition that I don't disclose their names, several others didn't want me to publicise their email addresses. In the interests of credibility I would like to be able to attribute the data on these pages, but the lack of openness in the industry makes this impossible in some cases.
Some in the industry only provide information in the form of PDF files that are very poorly indexed, so until they are downloaded it is very difficult to know what they might contain.
It was in response to this lack of easily accessible information that in late February 2008 I started expanding my wind farm pages – which previously had mainly concentrated on wind farms in South Australia – to cover the whole of Australia.
Unbiased studies into bird and bat impact, the effect of wind farms on property values, noise, sunlight-chopping, etc. should also be made easily and freely available. This is the responsibility of government as well as the wind industry.
Finally, I should say that there are many individuals in the wind power industry who have been very generous in providing me with information. It seems that those in charge of public relations are most at fault.
In my own experience Pacific Hydro who built the Clements Gap wind farm in the Crystal Brook area, consulted widely with the local communities. Roaring 40s (and then TRUenergy), the developers of Waterloo, Stony Gap, and Robertstown wind farms also seem to be making a good effort to inform the local people.
There have been complaints that the wind farm companies explain rather than consult; that they tell people what is going to happen rather than ask what should be done. In my experience this is true. But wind turbines must be built in the best places to build wind turbines; there is not a huge space for compromise if a wind farm is to be economically viable.
Communities are made up of individuals. Each individual who lives near a proposed wind farm will have an opinion on where turbines should, and more to the point, should not be built. Aesop said something to the effect of "He who tries to please everyone will please no-one".
The people of Australia demand copious amounts of electricity. The climate change problem demands that we reduce our carbon intensity. Wind power is one of the most technically advanced and competitive forms of renewable energy available. Of course the concerns of the local people should be listened to, and if there are consensuses to be found, they should be complied with if this is a practicality, but ethically, isn't there an obligation to aim at the greater good – of everyone and the world as a whole – rather than sacrificing the greater good in order to try to please all the local people?
|Wind turbines at North Brown Hill Wind Farm|
(Mid North South Australia).
A resident of Hallett complained to me that AGL, the owner of the Hallett
wind farms, has not provided any financial or other support for the
Hallett community, while admitting that support was given to Jamestown,
another nearby town.
I inquired about this, but did not receive a response (AGL have not responded to a number of my inquiries).
Most wind farmers do support the local community. For example, Pacific Hydro, which has built a wind farm near my home town, Crystal Brook, gives $50 000 each year for community projects for the life of the wind farm. Also there are many commercial gains to a community during wind farm construction: lease payments to land owners, work for local contractors, business for hotels, restaurants and providers of accommodation, etc. Once finished there are jobs in maintaining the wind farm.
Also see community funding by wind farmers.
It is quite possible that wind turbines will last longer than 25 years, but the technology is improving quickly and typical 25-year-old turbines have become obsolete, Salmon Beach, Esperance, WA, for example, became obsolete in 15 years.
Other sustainable energy systems, tidal, wave and hot-rock geothermal have not yet reached ages such as twenty or 25 years, but again they would be unlikely to last any longer than that. Hydro-power stations last longer than 25 years, but even they must need major maintenance at periods of a decade or two.
There is no one solution to our current dilemma, reducing energy consumption should have a higher priority than building wind farms, but wind power is just as much a long-term solution to the sustainable energy problem as is any generation technology.
Often these people are confusing efficiency with capacity factor, but in any case it is worth giving some thought to what could be meant by efficiency when applied to wind turbines.
The Oxford English Reference Dictionary defines efficiency as: "The ratio of useful work performed to the total energy expended or heat taken in."
Efficiency is very important in the case of fossil fuel power stations because fossil fuels are a finite resource – once we use them they are gone – and when burned they produce carbon dioxide and other substances that kill people and cause climate change and ocean acidification; so it is very important to get as much electricity as we possibly can per tonne of fossil fuel. A typical ratio of 'useful work' (electricity generated) to 'heat taken in' for fossil fueled power stations is about 1/4; ie; 25% efficiency.
It could be said that before windmills and wind turbines all the energy in the wind was being wasted – that is, the efficiency of converting wind energy to useful work was 0%. The more wind energy that is converted to useful energy, including electricity, the more we improve on that. If we don't convert the wind into useful energy it could be called a wasted resource.
At the most wind turbines convert somewhere around 40% of the power of the wind that passes through them into electricity. The energy of the wind is in its movement; to take all the energy from the wind would be to take all the movement from the air; with a little thought you can see that this would be quite impossible. The theoretical limit to the amount of power that a turbine can take from the wind is 59%; this is called the Betz limit.
Defining efficiency in the case of wind turbinesThe efficiency of a wind turbine could be defined as the electrical energy generated divided by the power that has been taken from the wind. In what follows, efficiency is considered to be the electrical energy generated divided by the power available from the wind.
What is lost if wind turbines take relatively little energy from the wind?Does it matter that wind turbines do not take all or most of the energy from the wind that passes through them? The answer has to be no. Wind is a renewable resource, we can never use it up, and the process of taking energy from it produces no pollution. If a particular turbine takes little energy from the wind that passes through it, then the velocity of that wind is not much reduced. No harm is done. (The turbine might produce turbulence, this has environmental implications and has been discussed elsewhere on this page).
The amount of power generated by actual Australian wind farms is given at Power generation of wind farms.
Energy in wind
Consider the power curve shown in the graph above (and the table on the right). It shows that when the wind velocity rises above 14m/sec the turbine does not generate more electricity, in spite of the fact that the energy in the wind increases.
We can calculate (from the cube relationship mentioned above) that this turbine is at its most efficient, in the sense of taking the greatest proportion of the available energy from the wind, at a wind speed of about 8m/sec. We can then calculate how its efficiency varies at other wind speeds, relative to that. This is laid out in the table on the right.
Note that if this wind turbine is 40% efficient at a wind speed of 8m/sec
then it is only 3.6% (0.09×40%) efficient at a wind speed of 24m/sec.
That is to say that it takes proportionally very little energy from the higher
So while the turbine does not reach its maximum rate of electrical generation until the wind speed gets to about 14m/sec, it is at its maximum efficiency at much lower wind speeds.
An article by wind farm opponent David Libby in which he calculates an efficiency of 24% for a particular wind turbineThe piece below was titled Absurdly Inefficient and published on the Net site Stop These Things, 2012/12/30. The arithmatic seems to be correct, but the conclusion strange to say the least.
Libby calculates that at a wind speed of 14m/second a particular turbine will generate 2MW of electricity while the total power available in the air passing through the turbine is 8.5MW (giving an efficiency of about 24%, very similar to that of coal-fired power stations). What he does not explain is why the 'failure' of the turbine to take a larger proportion of power from the wind is any sort of problem. Much of the power that was in the wind remains in the wind – is this bad?
Wind power opponents have a hang-up about wind turbines being inefficient, but, so far as I know, not one has ever explained how this claimed inefficiency is a problem.
Mr Libby has calculated that this particular wind turbine is 24% efficient. What harm is being done due to the wind turbine being less than 100% efficient? What is lost? Where is the problem?
The 24% efficiency that Mr Libby calculated is similar to the efficiency of coal-fired power stations and far ahead of the 15% efficiency of internal combustion engine-powered cars in converting the energy in the fuel into useful power delivered through the wheels.
Fossil fuels are dug or pumped from the ground and burned to generate electricity; it's very simple and very dirty. The industry receives a huge subsidy in the form of a license to dump its toxic wastes into the atmosphere.
Natural gas is often claimed to be considerably cleaner than coal, but natural gas is mostly methane, a very strong greenhouse gas. Recent research has indicated that leakage of methane into the atmosphere from gas wells and particularly from coal-seam-gas operations, might do more climate-changing harm even than coal.
The fossil fuel power stations dump their wastes into the atmosphere at no cost to their operators, but huge cost to the environment. These wastes cause climate change and many deaths and serious illnesses due to particulate matter, sulfur dioxide and oxides of nitrogen. See Wind turbines save lives and No level playing field.
Sustainable forms of power (including wind) require more work and more infrastructure for the same amount of power generation compared to fossil fuel power stations – thus have higher initial costs – but do not have the environmental problems associated with fossil fuel power.
If Australian governments were to cut out direct and indirect subsidies to the mining industry, and the fossil fuel power generators had to either stop dumping carbon dioxide into the atmosphere or pay for cleaning up the environmental damage that this causes, the fossil fuel industry could not compete economically with wind power.
While wind farmers get a premium for the power they generate, they generally do not get government money to build the wind farms.
|Wind turbines at North Brown Hill Wind Farm|
The only exceptions I know of are one or two very small community owned wind farms that might have had significant government funding.
In general, wind farms are built with private money.
However, they cannot compete with fossil-fuelled power stations so long
as the latter are allowed to dump their wastes into the atmosphere without
These wastes cause
climate change and many deaths
and serious illnesses due to particulate matter, sulfur dioxide and
oxides of nitrogen (see
Wind turbines save lives.
The electricity from renewable energy power stations is generally more
expensive than from fossil-fuelled power stations, so electricity
retailers have to have incentives to buy renewable energy.
The report, which was prepared for the Department of Energy and Climate Change in the United Kingdom, can be downloaded from the UK Government site.
I do not know how the figures for the graph were calculated, but probably
most of the 'support' for wind power in Australia would be from the
Renewable Energy Certificates connected with the wind-generated electricity.
Refer to the source report for more information.
Timing of wind power generation
The fact that wind power is not available on demand makes wind-generated electricity less valuable than electricity that can be generated on demand. However, the importance of these points can be exaggerated, and is often exaggerated, by those who oppose sustainable energy (the box on the right contains one example).
The fact that around 26% of South Australia's power was produced by wind farms in 2011, and greenhouse emissions from power generation in SA declined by about 20% from 2005 to 2010, with no reduction in power reliability, proves that renewable energy can provide a substantial part of Australia's electricity needs and produce a positive contribution to the climate change crisis.
Gas-fired generators are relatively cheap to build, although expensive to run and damaging to the environment because of their greenhouse gas production. It is the gas-fired power stations that commonlyy 'fill in the gaps' between power generation and demand in Australia.
A more environmentally friendly way of generating power at peak load is pumped hydro. Alternatively demand-side management of the electrical supply system could be implemented, where some of the loads are controlled to suit the level of supply.
One of the advantages of solar power in Australia is that its maximum output occurs on the sunniest days, which are often also when the higher power demands come; although by 5 or 6pm, at peak load, their power generation is very much in decline.
Weather radarThe moving blades of the wind turbines cause some problems to the operators of weather radars. The radar installations can be programed to ignore the returning signals from the wind farms. Large stationary installations also cause radar reflections, but these are more easily compensated for.
Surveillance radarThe following was provided by Pager Power Ltd.
Surveillance radar, used to detect aircraft and display their position on radar screens, can also show returns from other moving sources such as cars, trains and blades of a wind turbine. Wind turbine radar effects are dependent upon factors such as the type of radar installation; the distance to the turbines and the extent to which the turbines are visible to the radar. A common effect seen on Primary Surveillance Radar screens is that the rotor blades can produce intermittent radar returns. For this reason radar operators can object to turbine developments.
Technical effects include desensitization, receiver saturation and false returns. The most significant of these, for an air traffic control radar, is false returns. On older analogue type radar wind turbines can appear as clutter. There are many sources of clutter including insects, weather, traffic and birds.
In 2009 wind must be more profitable than solar. If it were not so then surely we would be seeing solar power stations all over the place instead of wind farms? There is no government bias toward wind power and away from solar that I know of. The people who invest their money in wind farms and the business people running the companies that build wind farms are not stupid.
By the way, a typical utility scale wind turbine has an installed capacity of 2MW and a capacity factor of 34% while the average Australian roof-top solar installation is 2kW and solar PV has a capacity factor of about 16%; so a typical wind turbine will generate as much electricity as 2000 average roof-top solar systems and a wind farm of 50 such turbines will generate as much power as 100 000 roof-top solar systems.
The table above shows that deciding whether solar or wind is the least environmentally damaging is not easy. Also see How does wind power compare to roof-top solar?.
Of course the potential of this would be similar to any other machinery in operation, for example, farm tractors and earth moving equipment.
Brendan Ryan of Suzlon gave me the following:
"The access roads are built to a high standard, I always joke that you can tell them apart from the local roads as they are in better condition. The drainage plan for the site is well thought out and the road compaction is quite high as well as the forming of the shoulders. Built Environs have to do maintenance work several years after the road is built to tease out any areas that may be an issue such as where ponding occurs. I think if you look at Hallett Stage One after several rain events you will find the roads holding up okay."
I inquired with Built Environs (who have constructed roads and hard-stands on several SA wind farms), but got no reply.
|Bird deaths from wind turbines|
North Brown Hill Wind Farm
Bird deaths from wind turbines
The USA National Wildlife Federation has a page on 'Encouraging Renewable Energy'. They write "NWF works to remove the barriers so that America and the rest of the world will quickly expand wind, solar, geothermal and biomass energy to power a new clean energy economy for all Americans."
ResearchThe Canadian journal, Avian Conservation & Ecology, published a research paper titled 'Canadian Estimate of Bird Mortality Due to Collisions and Direct Habitat Loss Associated with Wind Turbine Developments' in 2013. The authors used data from carcass searches from 43 wind farms and concluded that on average about 8 birds were killed per turbine per year.
Benjamin Sovocool, for the peer-reviewed Journal of Integrative Environmental Sciences (vol. 9, No. 4) wrote a paper titled The Avian and Wildlife Costs of Fossil Fuels and Nuclear Power in which he compared bird deaths from these sources of electricity to wind power. His paper was a synthesis of findings from many studies and was dated 2012/06/30. He provided figures of 0.27 avian fatalities from wind power per gigawatt-hour of electricity generated, 0.6/GWh for nuclear power and 9.4/GWh for fossil-fueled power stations.
"Estimates of bird mortality at wind facilities in the contiguous United States" by Scott R. Loss, Tom Will and Peter P. Marra; published in Biological Conservation, Vol. 168, Dec. 2013, Pages 201-209.
This synthesis study conclued that between 140 000 and 328 000 birds are killed annually by wind turbines in the USA. Loss et. al. list bird deaths "per MW", presumably meaning per installed MW. I have converted this to bird deaths per generated GWh, based on a 30% capacity factor. Loss's figure of 5.76 deaths/MW for the contiguouls USA becomes 2.19/GWh; about ten times as high as Sovocool's estimate (see above).
The UK Centre for Sustainable Energy published a document Common concerns about wind power in which it was stated that "wind turbines are responsible for less than 0.01% of avian mortality caused by humans, with by far the largest cause of deaths being standing buildings (more precisely, the windows), power lines and domestic cats". In the long term every wind turbine saves bird's lives by slowing the climate change that will be a far greater bird killer.
The recorded rate of bird mortality associated with the three Australian wind farms that I have seen figures for is between 0.23 and 2.7 birds per turbine per year. Several of the world's bird protection organisations hold that climate change is a far greater threat to birds than are turbines.
A study of avian mortality by Environment Canada gives the following figures for annual bird deaths:
Reference: "A Synthesis of Human-related Avian Mortality in Canada" by Anna M. Calvert, Christine A. Bishop, Richard D. Elliot, Elizabeth A. Krebs, Tyler M. Kydd, Craig S. Machtans and Gregory J. Robertson; Environment Canada, 2013.
Quoting from a fact sheet published by the Australian Greenhouse Office and AusWEA (Australian Wind Energy Association)...
"A US study published in 2001 carried out by Western Ecosystems Technology puts wind turbine collision into perspective with bird collisions with other structures: [deaths per year?]It should be noted that wind farm bird deaths per gigawatt generated are likely to be more numerous in the US than in Australia because:
At the Codrington wind farm in Victoria (14 turbines of 1.3 MW each) 20 bird and bat deaths were detected between 2001 and 2003.
"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 such as traffic, hunting, power lines and high-rise buildings and especially the environmental impacts of using non-clean power sources. For example, in the UK, where there are several hundred turbines, about one bird is killed per turbine per year; 10 million per year are killed by cars alone."
Wikipedia also discusses bird impact in its article on the Environmental effects of wind power.
Mike Barnard has an enlightening piece on Quora about birds and wind farms. Mike writes that:
"Replacing all fossil fuel generation with wind turbines world wide would save roughly 14 million birds lives annually. Declawing all house cats would save up to 500 million birds lives annually. Turning off lights in all windows at night would save up to 950 million birds live annually."He goes into far more details in his piece, and he gives the references to back-up his statements.
Audubon has a Net page on its position on wind power. Basically, Audubon recognise that wind turbines do pose threats to birds, but that Climate Change is a much greater threat and sustainable energy, including well sited wind farms, are needed if the world is to limit the damage done to birds by Climate Change.
"Acciona implements a comprehensive bird monitoring program at the Waubra Wind Farm in accordance with Avifauna Management Plan which was approved by the Minister for Planning in October 2006. This Plan was supported by extensive bird surveys of the site prior to commissioning of the wind farm.
Novel Scavenger Removal TrialIn order to test how many carcasses of birds killed by turbines are removed by scavengers researchers place bird carcasses and see how long it takes for scavengers to remove them. A paper by Smallwood, Bell, Snyder and Didonata (Journal of Wildlife Management 74(5):1089-1097; 2010; DOI: 10.2193/2009-266) (no longer available on the Net?) suggests that in conventional trials researchers might have dumped too many carcasses in small areas to get accurate results.
Doctor Hull has some interesting graphics illustrating her studies, but as these are in papers that she has submitted for publication in peer-reviewed journals she was not able to release them at the present.
I have taken the liberty of slightly modifying the text that I received in an attempt to make Tsai's meaning clearer (his English is limited).
"We found that a very direct effect of wind turbines on birds is the disruption of flying path between feeding and roosting sites. That is, the wind turbines cause a habitat fragmentation or a barrier effect. This is sometimes crucial for birds in their energy balance. If they spend too much time avoiding wind turbines or finding a safe way to their roosting sites, they are at higher risk of loosing their optimal habitat use pattern (the shortest route or minimization of energy expenditure).
The lizards live in spider burrows after either evicting or eating the spiders. Information on the species is available from several pages at Environment SA who state that there are 22 known sites with an estimated population of several hundred lizards living in each of at least ten of these sites.
Soil disturbance in lizard habitat destroys lizard burrows and kills lizards. It seems that they do not live much in stony hill-top areas, perhaps because there are few spider burrows in such hard and stony ground. The lizards cannot live in recently ploughed land, and are very slow to re-occupy ploughed land.
ABC Rural carried an article headlined "Introduction of wind farms helps find endangered lizards". A part is quoted:
Senior herpetology researcher at the [South Australian] Museum, Doctor Mark Hutchinson, says greater environmental scrutiny for wind farm developments has had an unexpected side-effect. "In the periphery of it where people are looking to put in tracks or other things, down the bottoms of hills and on the edges of where the windfarms are going, the lizards have turned up.
On the whole wind farms will provide more protection to bushland and grassland than cause damage. Climate change is a far greater threat to Australia's native vegetation than is the growth of the wind power industry. The June 2011 issue of Scientific American included a study about fire hazard linked to climate change. It seems that the area burned by wild fires in the US in the average year, given a one degree rise in temperatures, is expected to be up to six times as large as at present, depending on the ecoregion. And bushfires are not the only hazard to native vegetation that comes with climate change.
So we must replace the fossil-fuel fired power stations with renewable energy. Wind power is the most economically viable form of renewable energy at present (2012). Solar has great potential and is fast becoming cost-competative to wind, but is not there yet. The potential for hydro power in Australia is quite small, and if we dam rivers to get more hydro that will be much more damaging to the environment than will wind power developments.
In South Australia...
There is more native vegetation at:
The proposed Mt Bryan Wind Farm is an interesting case, where damage to native vegetation has been claimed by opponents, but where very little will take place so far as I can tell.
Of course remnant native vegetion is valuable and should be retained wherever possible.
and bat deaths,
fragmentation of bird
erosion and effects on
land values are dealt
with elsewhere on this page.
Roads must be built to gain access to wind turbine sites and 'hard-stands' flattened out where the turbines are to stand; there are environmental problems associated with road building, with the roads themselves and the hard-stands. Roads and road damage outside the area of actual wind farm construction is discussed elsewhere on this page.
Dust can be a problem during wind farm construction due to increased traffic movements. The increased traffic itself can also be a problem.
Wind farm opponents commonly complain that the heavy traffic needed to bring in wind farm components damages local roads. Like so many statements from wind farm opponents this is a half-truth. Yes, the additional heavy traffic does damage some of the roads, but I believe that there is also usually an arrangement between the wind farmer and council or between wind farmer and government whereby the wind farmer has to cover the cost of the necessary road repair.
The image on the right was printed in the Warrnambool Standard with the caption "A driver tries to traverse the crumbling Macarthur-Penshurst Road". In fact it is obvious that the driver is intentionally driving on the road shoulder for the purpose of obtaining a picture with impact. It also appears that the road is not "crumbling" in this section, the sealed part seems to be in good condition, it is only the earth shoulder that is rutted.
The road shoulder has probably been damaged by heavy wind farm traffic and it would be necessary for vehicles to move onto the shoulder when passing oncoming traffic, but it is a pity that so much of the media gives a higher priority to impact and sensationalism than truth.
In fact environmental organisations are strongly in favour of wind power. For example:
Whether there is a period during which animals get used to the turbines I don't know.
Having been a dairy farmer for eight years, and having had sheep grazing on
my property at Clare for the last 15 years, my own feeling is that neither
cattle nor sheep would be much concerned by wind turbines.
I discussed this with a farmer who has a stud sheep business as well as turbines on his property near the Clements Gap Wind Farm; he told me that the sheep like the turbines, resting in their shade in summer, and that he had no problem with falling lambing rates since the turbines were built.
I have often seen sheep sheltering in the shade cast by wind turbine towers, as in the photo at the right.
Nichols Poultry have their own 225kW wind turbine, one of the biggest in Australia in private hands, on their free-range poultry farm in Tasmania. Nichols have a Net site on which they provide information about their operation. Would Nichols do this if wind turbines harmed animals?
The wind doesn't blow all the time
It is very important to distinguish between variability and reliability. Wind turbine generation is variable depending on the wind, but wind turbines are typically around 97% to 99% reliable. The wind can be forecast with a fair degree of accuracy, so those who run the power grid know how much power to expect from wind farms.
It is also very important to understand that all forms of generation require backup. All power stations are closed down for periodic maintenance and are subject to sudden and unexpected breakdown. The power transmission grid is also subject to unexpected failure at times. The advent of wind power has made little difference to the way in which the power grid operates.
|Power generated from all AEMO monitored wind farms in Australia, 2012/01/15, combined output|
The Y-scale is megawatts (MW), the X-scale is time in 24-hour notation.
The graph above shows combined generation from most of the wind farms in eastern Australia on 2012/01/15. Note that the output varies only slowly and gradually – the slope of the line is gentle. Having a gradually varying output like this, combined with the fact that wind speed is predictable to a fair degree, makes it easy for the grid operator to bring other generators on-line as required. (2012/01/15 was the most recent full day of data available when this section was added; it was a pretty typical day.)
|Power generated from all AEMO monitored wind farms in Australia, 2012/01/15, shown individually|
The Y-scale is capacity factor, the X-scale is time in 24-hour notation.
Each coloured line records the output of one wind farm.
Even within one large wind farm though, variation is 'averaged-out' because
as the wind slows in one part of the wind farm it might be blowing more
strongly in another part.
Compare this graph with the one of the small Wonthaggi Wind Farm, below.
Wind can now be forecast fairly reliably 24 to 48 hours ahead. When wind farms are not generating the electricity deficit can be taken up by other generators such as natural gas-fired power stations. Most of the backup generators only run when required to make up the short-fall in power generation and are idle at other times. Of course there are costs involved in keeping power stations on standby. Some backup also needs to be kept running as spinning reserve so that it can be brought on-line at very short notice, but this has always been so in case of break-down of generators.
In fact, since the variability of power generation from wind farms is slow and predictable it is easier to cope with in a power grid than the occasional breakdown of a large fossil-fuel or nuclear generator, which will be sudden, unpredictable, and produce a big deficit in the power supply-demand balance. If one turbine in a wind farm breaks-down the power output of the whole wind farm will only drop a little because the other turbines continue operating.
All power stations are off-line some of the time. Fossil-fuelled power stations are typically available around 85% of the time; at other times they are undergoing maintenance or suffering breakdown, etcetera. For example, on the evening of 2013/05/31 600MW of generating capacity from AGL's Torrens Island power station was lost and at the same time 200MW was lost from Origin Energy's Osborne plant, both in South Australia. (This is equivalent to the maximum power output from about 400 wind turbines.) The system coped with this loss. There has always been backup in the system, the advent of wind power has not produced any need for greater backup.
A part of the problem of the pseudo-random variability of supply and demand could be overcome by introducing Supply Dependent Load, which is discussed in my Sustainable Electricity page and hydropower could also be used to balance generation and consumption (as is done very effectively with wind power in Denmark balanced by hydropower from Norway).
If it was economically (or environmentally) justified, then additional power supply-and-demand balancing methods could be introduced. I have included a section on how pumped hydro power can be used to balance the generation of wind power on my Sustainable Energy page. Of course developing pumped hydro has its own cost, but power that can be generated on demand and at short notice receives high prices in a supply and demand based power system, so it could prove to be economically justified.
Sometimes too much energy can be generated by wind farms; this could cause overloading problems in the electricity grid. AEMO has the power to make wind farmers limit their generation at such times.
The proportion of electricity that can be generated by wind before problems relating to variability of supply become intolerable has been debated for years. The magazine Wind Power Monthly reported that Denmark generated 31.5% of its power by wind in January 2008 (apparently January is its windiest month) and had generated even more in January 2007 (35.5%). Even more importantly, the article stated that there had been no need to constrain production from the turbines at any time.
Sustainable energy must be diversified; we need to develop alternatives such as solar and wave energy as well as wind. When an area is covered by a meteorological high pressure area, and consequently has light winds, there is a good probability that the sun will be shining and solar power output will be high. (See Solar complements wind.)
A part of the answer to the intermittency of the wind would be to use electricity when it is abundant to desalinate seawater. Australia has major water supply problems; in SA these are particularly severe on Eyre Peninsula (which has excellent wind resources). It should be possible to set up desalination plants to run when there is excess electricity. Electricity can not easily be stored, but water can be, readily and cheaply. Why not have the desalination plants organized so that they switch on when power is abundant and switch off when the power supply declines? Using wind power to desalinate water on Eyre Peninsula is discussed in Eyre Peninsula Water.
Improved wind forecasting would provide forewarning of changes in the quantity of wind-generated electricity entering the grid.
Regional variation in wind
There are 39 data points in the marked area of the graph: 39 days when there was low wind farm output in both SA and NSW.
The total of the data points, or days, in the whole graph is 200.
So, while there were 39 days in which there was low wind farm output in both states, there were 161 days in which there was not!
That is, there were four times as many days when low wind generation in one state coincided with significantly higher generation in the other state than days with low generation in both states.
Reliability is often confused with variability, especially by opponents of wind power.
In regard to the amount of power a particular wind farm will supply to the grid at any time: "wind farm operators ... estimate the wind farms energy output one hour in advance for each 5 minute period of supply. This is successfully achieved by using sophisticated short term forecasting models that interpret weather information as it affects the wind farm in real time." (From the Ceres Project FAQs.)
There is an informative article on the reliability of wind power on Into The Wind, the American Wind Energy Association blog. For example, it showed that Germany, which gets 10% of its electricity from wind power has a power system that is the most reliable in Europe and has a 'reliability score' 16 times better than that of the USA. The German system is also four times more reliable than that of France; which relies heavily on nuclear power.
"Wind generators have a high temperature alarm at around 43 degrees and will shutdown at around 45 degrees to protect components. That's measured at the nacelle 70m above ground. At Challicum Hills (near Ararat) during 2004 our wind farm experienced 15 minutes of unavailability due to high ambient temperature. That's 0.003% of the year."It was reported in The Adelaide Advertiser on 12th February 2006 that the operators of the Lake Bonney Stage 2 wind farm said that all its 46 turbines shut down on January 22nd when temperatures exceeded 40C. (It seems that the turbine fire on that day was not due to a turbine overheating but to an electrical fault during maintenance.)
Temperatures above 43° are rare where wind farms are built, and often occur on calm days when turbines are either not working or working at low capacity.
The US Geological Survey in cooperation with the US Fish and Wildlife Service produced a report titled Bats and Wind Energy – A Literature Synthesis and Annotated Bibligoraphy in 2012. Three of the points it gave were:
Little research seems to have been done into this potential problem in Australia. It seems there is a great need for research.
I believe that Brett Lane and Associates of Melbourne wrote the wind industry's 'best practice' guidelines on bat and bird monitoring.
Iberdrola Renewables, Acciona, and BP have bat concerns over several USA wind farms that they were intending to develop. It seems that the Indiana bat, an endangered species, has suffered from 'white noise syndrome', and there is concern that wind farms might prove a problem to the species.
Wikipedia discusses bat impact in its article on the Environmental effects of wind power. Wikipedia stated that "In April 2009 Wind Energy Cooperative released initial study results showing a 73% drop in bat fatalities when wind farm operations are stopped during low wind conditions, when bats are most active." There would be little loss to the turbine operators in stopping the turbines at such times, in areas where bat fatalities are a problem, because very little power is generated in low winds; see Wind speed range of turbines. (More on this below.)
On 2012/04/19 I discussed this research with Dr Cindy Hull, who has studied bird and bat kills in relation to the Bluff Point and Studland Bay wind farms. She informed me that in her opinion the 'death by barotrauma' question was not settled. Later, in a paper published in the New Zealand Journal of Zoology, and on the same subject, Dr Hull stated that collisions were thought to be the primary cause of fatality; referring to:
Note that if 50% of the bats were killed solely by barotrauma and barotrauma was a contributing cause of death in 90% of deaths then it follows that the bats killed by this cause must have to fly quite close to a moving blade to be injured by barotrauma. If it were not so then one would expect higher percentages of deaths to be due to barotrauma.paper with PhD student Erin Baerwald and Jason Edworthy and Matt Holder of TransAlta Corporation on this (September 2009):
"Scientists at the University of Calgary have found a way to reduce bat deaths from wind turbines by up to 60 percent without significantly reducing the energy generated from the wind farm. The research, recently published in the Journal of Wildlife Management, demonstrates that slowing turbine blades to near motionless in low-wind periods significantly reduces bat mortality."
An article by Edward B Arnett, Manuela MP Huso, Michael R Schirmacher and John P Hayes published in Frontiers in Ecology and the Environment, 2011 recorded research in which it was found that bat mortality was substantially reduced by slightly increasing the turbine cut-in speed. The authors suggested that this could be done at times of greatest likelihood of bat deaths with little effect on power generation.
In 2013 Edward Arnett, Gregory Johnson, Wally Erickson, and Cris Hein published the report: A synthesis of operational mitigation studies to reduce bat fatalities at wind energy facilities in North America. This pulled together conclusions from a number of field studies in which researchers recorded bat fatalities while experimenting with cut-in speeds.
Bats cannot fly at wind speeds much greater than around 4m/sec, the normal cut-in speed of wind turbines. Turbines generate very little power at such low wind speeds, so increasing the cut-in speed to, say, 6m/sec. for some time would result in little loss of generation.
I have not read any half-way convincing evidence to support the truth of this claim, and find it very hard to imagine how it could happen. Bees would very rarely, if ever, fly high enough to be hit by a turbine blade.
I add the point to this page as an example of one of the difficult to credit claims being made against wind turbines with no apparent basis in reason or science.
There are well known problems occurring in the world's honey bees; varoa mites and colony collapse disorder among the more prominent of them. Separating pollination problems, or bee number reduction problems caused by wind turbines, from these much better researched and credible problems, would require careful research, and I have not heard that any such research has been done.
I believe that regulations imposed on the operators of wind farms in Australia do not allow major power surges. The wind farm operators have to put in place devices stopping power surges entering the electricity grid.
|A misty Autumn morning at a wind farm|
A farmer from an area downwind of a proposed large wind farm expressed
concern to me that the slowing of the wind might cause greater rainfall
at the wind farm and less rain downstream.
At first it seemed unlikely to me that any effect would be significant,
but on more investigation some interesting points started showing up.
Relief rainfallFrom Wikipedia: "Orographic or relief rainfall is caused when masses of air pushed by wind are forced up the side of elevated land formations, such as large mountains." Wind farms on the tops of ridges will have the effect of making the ridges 'appear' to the air-flow to be a little higher; it would therefore be very reasonable to expect an enhanced orographic effect.
When a wind turbine takes energy from the wind flowing through it, it slows that wind down. A bit of thought then shows that for the same volume of air to pass a point in the same time, but at a lower speed, it must take up more space. Putting it another way; if you think of a cylinder of air the diameter of the turbine blades approaching the turbine, then the velocity of the same air slowing as it passes through the turbine, the diameter of the cylinder on the down-wind size has to be bigger because the velocity is lower and the same amount of air per unit time must pass through it. The slow-moving air on the down-wind size of the wind farm will take up more space than the higher-speed wind would have before the wind farm was built, so this will cause the air-mass above to rise a little higher to pass over the obstruction.
In Australia, I suspect that most people will think that a slightly increased local rainfall is a very good thing. On the other hand, it would mean that there would be a little less moisture in the air that moves away from the wind farm into other areas.
How much will a wind farm increase the effective height of a ridge?In 2009 the rotor heights of typical wind turbines are about 80m above local ground level; a typical spacing seems to be about four turbines per linear kilometre along ridge lines; rotor diameter is about 90m. So looking across the ridge the turbines take up 4×90m=360m in every 1000m, or about 1/3 of the profile. A modern wind turbine takes up to about 30% of the energy from the wind that passes through it (the theoretical maximum, the Betz limit, is 59%). It seems to me that something in the order of 10 to 20m of effective height added to the ridge would be reasonable; but that is more quess than estimate. Of course if there was more than one row of turbines the effect would be stronger.
Research into the significance of this effect would be useful.
Turbulence from wind turbines will also cause some changes in the local temperatures. The turbulence increases the mixing of the air at very low levels with that at higher levels.
Nature Climate Change, one of the Nature Publishing Group, published a paper by Liming Zhou, Yuhong Tian, Somnath Baidya Roy, Chris Thorncroft, Lance F. Bosart and Yuanlong Hu, titled "Impacts of wind farms on land surface temperature". It was published online 2012/04/29. "Here we present observational evidence ... based on analyses of satellite data for the period of 2003-2011 over a region in west-central Texas, where four of the world's largest wind farms are located". The results of the study "show a significant warming trend of up to 0.72°C per decade, particularly at night time, over wind farms relative to non-wind farms".
The 'per-decade' part of the statement is misleading, as the satelite data only showed a rise in temperature, not a continuing trend. Apart from this the slight surface temperature rise should surprise no-one; earlier research (2004, S. Baidya Roy and S. W. Pacala) has shown a similar effect and if looked for, it probably would be found downwind of any tall structure that causes turbulence, such as grain silos.
At night time a layer of cool, calm air can develop close to the ground.
The turbulence from nearby turbines, or other tall structure, can cause the
warmer air above to mix
with this cool layer; increasing temperatures at the surface.
These higher temperatures, and increased air movement over the surface, can
increase moisture loss from the soil.
An array of turbines will have an effect on wind flow similar to that of trees, they will slow the wind at lower levels due to the energy that they take from it and the turbulence that they cause.
In many parts of the world trees and forests have been cleared from huge areas; Australia has lost a very large proportion of the scrub, woodland and forest that it once had in its agricultural areas. Will the introduction of wind farms change the 'surface roughness' back to nearer what it was before the trees were cleared?
Again, research into the likely effects on weather should be carried out.
Pim Rooijmans, of Utrecht University, did a master's thesis on the "Impact of a large-scale offshore wind farm on meteorology"; a 3MB pdf file was available, but no longer is. Rooijmans wrote of a reduction in rainfall in one rainfall event in one place, of more than 50%, but increased rainfall elsewhere. Rooijmans' figures were based on computer modelling rather than actual events.
The New York Times published an article that discussed research published in The Journal of Geophysical Research; lead author, Dr. Somnath Baidya Roy. These researchers, using simulations, found that:
"In the Great Plains [of the USA] there is a nighttime stream of fast-moving air that separates cool, moist air near the ground from drier, warmer air above. The simulation found that the [hypothetical] turbines catch this nocturnal jet, and the ensuing turbulence causes vertical mixing."This would cause more drying of the soil than would happen otherwise, and would also have implications for heating or cooling of homes. Roy suggests a solution – create better rotors. "We found that low-turbulence rotors are more economically efficient, they tend to generate more electricity than conventional rotors," he said.
The researchers said that:
"During the day, the effects from the disturbed airflow are negligible, since natural turbulence mixes the lower layers of the atmosphere. But the researchers found that in the predawn hours, when the atmosphere is less turbulent, a large windmill array could influence the local climate, raising temperatures by about 2 degrees Celsius for several hours. The rotating blades could also redirect high-speed winds down to the Earth's surface, boosting evaporation of soil moisture."
Informative linksWindlab have researched turbulence and its effects on wind turbines.
This video clip, taken from a light aircraft, shows wind turbines operating in low cloud, but without causing any apparent turbulence.light aircraft and wind turbine turbulence.
The energy consumed in construction of a wind farm is very much less than the energy that farm will produceSome wind power detractors have claimed that more energy is used in constructing wind turbines and building wind farms than is saved by the wind turbines displacing fossil-fuel fired power stations. Investigation shows that this is false. (I have included several references and one calculation of my own in the discussion below; it can be seen that all come to similar conclusions.)
The same journal, Renewable Energy (20  279-288), published a paper by L. Schleisner, titled 'Life cycle assessment of a wind farm and related externalities'. Schleisner discusses two hypothetical wind farms, one offshore and one land-based. He concluded that the energy pay-back time for the offshore wind farm would be 0.39 years and for the land-based wind farm 0.26 years; both being less than 2% of the assumed 20-year lifetime of the wind farms. The journal Renewable Energy has an impact factor of 2.2.
The Danish wind turbine manufacturer Vestas report in a "Lifecycle Assessment of a V90-3.0 MW onshore wind turbine" that it will typically 'pay back' the energy consumed in the whole life of the turbine in 6.6 months. Their lifecycle assessments are available on the Internet.
Suzlon, another wind turbine manufacturer, estimated in regard to the Brown Hill Range Wind Farm in SA that 'the payback period of "embodied energy" of the whole wind farm is approximately 5 months'.
The technical term for the amount of energy consumed in the process of obtaining energy compared to the energy obtained is Energy Return on Investment (EROI) and I have covered this in some detail in Wind power. In the study discussed there, wind farms, on average, produce around 18 times as much energy as is used in their construction. One would expect that this figure will increase as wind farms operate for longer periods and as the technologies mature; indeed, given an energy payback period of six months and a (conservative) turbine life of 20 years one can calculate an EROI of 40 (neglecting any energy involved in repairs and maintenance).
Pacific Hydro have stated in a publication that "on average it takes only two to three months for a wind turbine to recover all the energy required to build it".
A publication of Wind Energy (Denmark) dated December 1997 states that the energy payback time for a 600 kW turbine is 3.1 to 3.8 months.
The related question of the carbon dioxide balance of wind farms is covered on this page in CO2 and wind farms.
A little thought will show anyone with any grasp of engineering at all that this is a crazy claim, but what is the fact?
Lane Crockett, head of Pacific Hydro, has informed me (2014/06/12) that "a typical 2 MW wind turbine will use about 5 kW when not spinning". To put this into perspective, the same turbine, in eastern Australian conditions, will generate a long term average of around 700 kW.
The CO2 released from the manufacture of the cement used in the concrete bases of wind turbines is comparatively smallThis relates to another claim that has been made by wind farm opponents that seems to be completely without any basis in fact. The calculations below show that the CO2 released into the atmosphere during cement manufacture is 'payed-back' in the first day or two of turbine operation.
Around 150 tonnes of concrete are used in the foundations of a single wind turbine. Cement manufacture releases large amounts of CO2 to the atmosphere. Is this pollution comparable to the CO2 abatement resulting from the wind farm's electricity replacing coal-fired electricity?
Also see CO2 and wind farms, which deals with the total amount of carbon dioxide released from wind farm construction, elsewhere on this page.
Joseph Davidovits, Geopolymer Institute, Saint-Quentin, France stated:
"Studies have shown that one ton of carbon dioxide gas is released into the atmosphere for every ton of Portland cement which is made anywhere in the world."
From McCaffrey "The Cement Industry's Role in Climate Change" (the link, http://www.propubs.com/climate/climate.html, is no longer working), one can calculate that for each tonne of cement that is manufactured, about 0.9 tonnes of carbon dioxide is released into the atmosphere.
The Information Unit on Climate Change, Switzerland,
states that about a half a tonne of carbon dioxide is released from
the roasting of the raw materials for each
one tonne of cement manufactured. This does not include the carbon
dioxide released from burning fuel.
How much CO2 is released for each wind turbine?From the above we could work on 0.9 tonnes of CO2 for each tonne of cement, as a rough figure. A publication of Pacific Hydro states that each of their 1.5 MW turbines at the Challicum hills had 150 tonne foundations. Working on 10% of the foundations being cement (the remainder sand, gravel, steel and water) this gives a figure of 15 tonnes of cement resulting in the release of 13.5 tonnes of CO2 to the atmosphere.
Pacific Hydro state that the CO2 abatement due to the power production of each of their 1.5 MW turbines is 5000 tonnes per year (13.7 tonnes per day). My calculations confirm those of Pacific Hydro.
ConclusionIf these figures and calculations are correct, the 13 or 14 tonnes of CO2 released from the manufacture of the cement is paid back in the first, or early on the second, day of turbine operation.
Abatement: CO2 and wind
Note the very large decline in South Australia's EI; due almost entirely to
the introduction of wind power.
Much of this reduction is due to far less use of the state's only remaining
coal-fired power station, the Northern, which, as of 2013, was being run for
only the warmer half of each year.
Its declining capacity factor is shown
elswhere on these
Wind power in Australia became significant in around 2003 and steadily
The Australian Energy Market Operator (AEMO) in the draft 2011 South Australian Supply and Demand Outlook report showed that emissions from electricity generation in SA declined by about 20% over the same period as generation by wind farms increased from near zero to 20% of total generation. See their graph.
The Australia Institute is an independent public policy research centre funded by grants from philanthropic trusts, memberships and commissioned research. It has a pdf document about The facts and fallacies of wind power. In this document The Australia Institute's researchers stated that taking into consideration all the CO2 released during manufacture, construction and management of a wind farm, every megawatt-hour (MWh) of wind farm electricity comes with a carbon cost of 14kg of CO2 while coal-fired electricity comes with a carbon cost of around one tonne of CO2 per MWh.
They further state that:
"the emissions related to the manufacture, construction and operation of the wind farm are likely to be equal to less than two per cent of the emission reductions that arise as a result of the displacement of fossil fuel-based electricity generation."
|Average abatement intensity from wind generation, kt CO2e/GWh|
Put simply, in the Victorian situation, for every MWh of power generated by a wind turbine about a tonne less CO2 will be released into the atmosphere than would be without the wind power. See the McLennan Magasanik report for a full explanation.
A single, typical 2 MW wind turbine operating at a typical capacity factor of 35% will generate around 6 000 MWh each year and save about 6 000 tonnes of CO2 from entering the atmosphere each year. A typical wind farm of 30 turbines will save 180 000 tonnes of CO2 each year.
|Decoupling of electricity generation and emissions|
Graph credit – Hugh Sadler, CEDEX report by Pitt and Sherry.
|Visual objections to wind farms|
Visual objections to wind farms
Almost everyone agrees that there are some places – particularly areas of great natural beauty – where wind turbines should not be built. I can't imagine that anyone would suggest that a row of wind turbines on top of the Wilpena Pound Range in the Flinders Ranges would be desirable.
In an article about the proposed Merredin Wind Farm the Merredin Mercury printed the following:
In a study in Geographical Research published by Wiley-Blackwell, it was found wind farms have a negative impact on landscapes with a high scenic quality, but a positive effect on dull and mundane landscapes. Author Dr. Andrew Lothian said while people may be apathetic to the appearance of wind farms, their location is critical. "Wind farms in scenic areas, particularly the coastal areas, are regarded as damaging to the landscape," he said. "However, in agricultural areas of low scenic quality, wind farms seem to beautify the otherwise mediocre surroundings."
Also see Air navigation lights, below.
|Air navigation lights|
There is no need, either for safety or in law, for the lights to be so bright. AGL had them switched off around the end of 2009.
Air navigation lights
In Denmark and New Zealand lights on wind turbines are one hundredth the brightness of many of those used on Australian turbines.
The air-navigation lights on the first two of the Hallett wind farms, 50 kilometres away from my place in the Clare hills, were not only visible to me, they were conspicuous (photo above). If I walked about 1km west I could see another line of red flashing lights, this time of the Snowtown Wind Farm, 40km away. (The lights of Snowtown Wind Farm are also conspicuous from Crystal Brook, about 40km to the north.) (All of these lights have since been switched off [2012/03/27].) Whether an individual finds the lights objectionable or not is a matter of that individual's perception.
In Australia the Civil Air Safety Authority (CASA) decides how bright the lights must be when the turbines are in the vicinity (approximately 30km) of an aerodrome.
"CASA cannot mandate the lighting or marking of structures outside the vicinity of aerodromes. It is CASA's view that this is a decision for, and the responsibility of, the developer" (pers com Paul Trotman, CASA)."CASA did publish an Advisory Circular (AC 139-18) to provide guidance to wind farm developers, this has since been withdrawn.
"Mr Byron (Chief Executive Officer, CASA) has ... directed that CASA now undertake an appropriate safety study into the risk to aviation posed by wind farms and develop a new set of guidelines."
There is no air safety necessity for the lights to be so bright that they are conspicuous at 50km. Being easy to see from 5km would be quite enough for air safety; using the inverse-square law of illumination this would require only one hundredth the present brightness in the lights. Indeed, I have been informed that while CASA advised the use of lights of 2000 candela on tall wind turbines in Australia, the New Zealand authority holds that lights of 20 candela are acceptable at Tararua III Wind Farm, even near an airfield (Terry Teoh, Pacific Hydro, pers. com. Sept. 2008).
In Denmark 10 candela lights are used, and in Germany there are various standards, but usually blinking 100 candela lights are used. (Tobias Geiger, Westwind Energy, Global Windpower conference, Adelaide 2006)
The wind farmers must take the bulk of the blame for the bright lights. As stated above, CASA only has an advisory roll, the wind farmers could use dimmer lights without breaking any law. One can only suppose that they use very bright lights because they fear that if they used anything dimmer and there was an aerial accident, they might be sued. They don't want to take any risks with their money. If the lights annoy people, that is of less concern than the remote chance of a big law suit.
If the lights must be bright for those times when visibility is poorer, then there could be two sets of lights, one for good visibility and one for poor – with an automatic system detecting poor visibility and switching from one to the other. At least in South Australia the dimmer lights would be sufficient more than 95% of the time.
Excessively bright lights on wind turbines conspicuously contradict the need to minimise energy consumption. Having obvious wastage of energy, even if it is trivial in comparison to the total energy generated, associated with devices that are aimed at reducing greenhouse gas production seems particularly incongruous.
During construction, water is required for making the concrete needed for the footings of the towers, and for things like damping-down while road-building, but these require small amounts of water relative to those used for mining coal or uranium or cooling coal-fired, or nuclear, power stations.
Terry Teoh of Pacific Hydro informed me that in building their last three wind farms (totalling 159 MW installed) they used 36ML of water. Tim Knill of AGL estimated rather less water requirement; my own estimate was similar to Terry Teoh's figure.
For comparison I believe that a typical Australian wet-cooled coal-fired power station uses around 1.5 kL per MWh of electricity generated. The 159 MW of wind farm referred to by T. Teoh above generates about 322 GWhr of electricity per year. That amount of electricity generated by a wet-cooled coal-fired power station would require about 480ML of water. That is about 13 times as much water, every year, as was used to build the Pacific Hydro wind farms.
Comparing with agriculture might also be interesting. The average water consumption for wine-grape growing in the Murrumbidgee Irrigation Area (MIA) is 5ML/ha/year; in the Clare Valley, about 1ML/ha/year. So a single 36ha vineyard in the Clare Valley would use as much water, each year, as was used to build the Pacific Hydro wind farms. In the MIA, 36ML would only be enough for 7.2ha for one year, probably not a big enough vineyard to provide a living for a single family.
One of the greatest advantages of wind power is its very small water requirement.
This seems to be completely unfounded. I worked in the groundwater field for over thirty years and cannot imagine any way in which the turbines or turbine foundations could harm groundwater resources.
As mentioned under water requirements of wind farms relatively little water is used during construction and a negligible amount is used during operation of a wind farm. Wind farms displace fossil fuel power stations that often use huge volumes of water for cooling.
Of course any industrial development, including many farming developments, can lead to contamination of surface and groundwater, but I've never heard of any significant contamination due to wind farms anywhere in the world.
ERTP (Electronic Resources for Tourism Professionals; link no longer available) published an abstract of a paper by Cara Aitchison (University of the West of England) entitled "Lies, damned lies and wind farm survey statistics: disentangling survey methodologies and motives in tourism impact studies". She wrote
"The small scale of the research undertaken to date, the geographical specificity of each survey commissioned and the variable research methodologies employed has resulted in a fragmented research base that has left planning inspectors unable to reach a definitive conclusion on this subject."She also mentions opponents of wind farms "use of alternative and unorthodox survey methodology which resulted in highly contentious research findings".
The Quebec Source for Information on Global Trends in International Tourism has a page by Julianna Priskin titled 'Do wind farms affect tourism?' In its conclusion Priskin states that "The few studies mentioned here suggest that even though the majority of tourists may appear positive about wind farms" and goes on to provide a cautionary note.
|Turbines, fog and gum trees|
The photo at the right is of the Kamaoa Wind Farm, Hawaii. I have no information on the length of time that the turbines remained in a neglected state.
We in Australia must take care that old, unviable wind turbines do not become a blot on the Australian landscape. The owner of the wind farm should be made to remove it when it is no longer operating. Government has a responsibility to make sure that this will be done; perhaps there should be money compulsorily held in trust accounts specifically for the dismantling of wind turbines at the end of their useful lives?
The very large wind turbines that have been used in Australia will have a high scrap value and therefore I would expect that it will be worth dismantling them for their steel, copper and other valuable components, rather than leaving them once they become unusable.
The break-up of a rotating turbine is an extremely rare event. It has never happened in Australia (as of November 2013). An anti-wind power Net site (Caithness Windfarm Information Forum) records an average of about 20 blade-failure events per year world-wide (not necessarily in utility scale wind turbines). There are around 250 000 utility scale wind turbines in the world. Assuming that all 20 blade failure events recorded by Caithness were in utility scale turbines, we can calculate a probability of one turbine in 12 000 suffering from blade failure in any one year. That is, a probability of blade failure of 0.000083 in any one year, or 0.00000023 on any particular day.
So far as I have been able to find out, no one has ever been injured by a piece of a blade thrown from a utility-scale wind turbine.
No country anywhere in the world has abandoned wind power, most of those with good wind resources are building more wind farmsSome objectors to wind power make the point that wind farms are being abandoned in Europe and the USA and that this must prove that these countries have learned that wind power is no good. It is a fallacy based on a half-truth.
The wind farms that are being abandoned are old ones, with old, out-dated turbines. Wind turbine technology has been steadily improving over the past few decades; the best turbines of twenty years ago cannot compete with modern turbines. Why keep a wind farm with out-of-date and (by modern standards) inefficient technology going when there are more efficient options?
In Esperance, WA for example, small, old, out-dated turbines have been replaced with bigger, newer ones; the capacity of the new wind farms (5600 kW) is much greater than the old one (360 kW). It's called progress!
No country that has a significant development of wind power is abandoning wind power; they are all building far more new wind power station capacity than the old that they are abandoning. Total installed wind power world-wide is increasing at an exponential rate.
In South Australia, for example, southern Eyre and Yorke Peninsulas, Kangaroo Island and the Limestone Coast (south-eastern SA) would have more wind farm development if the existing transmission lines had more capacity. This problem is discussed in greater depth in Sustainable energy in Australia.
The Electricity Supply Industry Planning Council Annual report for 2009 stated that "Further development of wind in South Australia will require significant investment in networks that, at times, already struggle to cope with the transfer of high levels of wind energy, particularly in the mid-north and south-east of the State."
Governments fund and build transmission lines for coal-fired power stations and mines, but no Australian government has yet funded and built a transmission line for sustainable electricity. (Yet another indication that Australian governments are not serious about developing sustainable energy?)
Christeen Milne, Greens MLC in Tasmania, has suggested that wind power development regions (WPDR) should be identified and transmission lines built to these in anticipation of wind farm development. This would replace the present ad-hock industry growth. The US state of Texas is following a similar approach. Among other qualities required for an area to be classed as a WPDR would be for the local people to be generally in favour of wind development.
The only promising sign (as of November 2010) seems to be the Eyre Peninsula Wind Project, a proposal to build major power lines on South Australia's Eyre Peninsula to connect to major wind resource areas.
Many coal-fired power stations are burning less coal because of wind farms. In South Australia, for example, wind farms now produce 26% of the electricity and, while coal-fired stations used to produce 42%, they now only produce 25% of the state's electricity. Over the six years this has been happening, greenhouse gas emissions from power generation has been decreasing.
The main reason that coal-fired power stations have stayed in service for so long is that the power consumption in Australia, until recently, increased faster than wind farms were being built. Consider, for example, how popular big plasma TV sets are; they can consume as much power as a refrigerator. Air conditioning too, is a big electricity consumer, and is becoming more common, at least partly driven by rising temperatures due to climate change (which, of course, is driven largely by burning fossil fuels).
Wind farms result in less CO2 being released into the atmosphere than would be the case if they were replaced by fossil fuel power generators.
In fact the typical utility-scale wind turbine seen in Australia today has the capacity to generate up to about two megawatts, and on average will generate about 35% of that (see capacity factor, on another page). The capacity factors achieved in a number of South Australian wind farms is shown on another page.
The graph, from the Australian Energy Market Operator (AEMO) 2011 draft 2011 SA Supply and Demand Outlook report, shows that 20% of SA's electricity came from wind farms in 2010/11. Note also on the graph wind energy is growing quickly. The same report stated that SA's greenhouse gasses due to electricity generation decreased by about 20% over the same period.
Andrew Miskelly provides daily wind farm output in a graphical format in wind farm performance.
Many of the wind farmers, when announcing a new wind farm, will make a statement about how many homes it will be able to supply with electricity. I have listed some of the numbers used by various companies elsewhere on this site; they vary from 400 to 740 homes supplied per installed megawatt of wind power. These figures seem to assume that the average household electrical consumption is between 470 and 875 Watts; 470 Watts seems to me a little on the low side to be credible. Still, given that an Australian wind farm with an installed capacity of 50 MW would be only moderate in size, even if the average household consumption is 1 kW we can calculate that this moderate-sized wind farm would generate enough electricity to supply more than 17 000 homes.
The average roof-top solar power system in Australia is 2.043 kilowatts (Office of the Renewable Energy Regulator) and will generate about 3.2 megawatt-hours of electricity each year. A typical 2.1 megawatt wind turbine will generate about 6300 megawatt-hours each year, as much as around 2000 roof-top solar power systems!
The working for these calculations is shown on the right. See the glossary for an explanation of capacity factor and note that the capacity factor for Australian wind power is about twice that for Australian solar PV.
So, while putting a solar power systems on your roof is a step in the right direction in the fight against climate change, providing support to a wind-power company that wants to build wind turbines would be a much bigger step.
It is worth noting that the total solar PV installed in 2011 exceeded the total wind power installed in the same year – although, because of the lower capacity factor of solar, the power generated from this installed wind power will still be considerably greater than from the installed solar PV.
capacity factor for
wind farms is around 35%.
This indicates that they generate about 35% as much power as they would
if they were operating at full capacity all the time.
As the wind becomes stronger than this the turbine generates more and more power until the nominal (or full-power) wind speed is reached. (From 4m/sec. to 14m/sec. in the graph.)
As the wind increases above the nominal speed the turbine continues to generate its maximum power until the wind gets up to the cut-out (or stop wind speed). (From 14m/sec. to 25m/sec. in the graph.)
If the wind speed increases above the cut-out speed the blades are 'feathered' (turned about their axes so as not to produce rotational force at the hub) and the turbine stops. (Above 25m/sec. in the graph.) Winds of greater than 25m/sec. (90km/hr) are very rare in Australia.
Wind turbines generate power from the cut-in wind speed right up to the cut-out wind speed. A graph showing a one month generation record from a wind farm is above. It shows that most of the month that farm was generating some power. The graph was not chosen because it was in any way exceptional.
The amount of wind energy theoretically available is proportional to the cube of the wind speed.
On 2012/03/21 a wind turbine at Wonthaggi Wind Farm in western Gippsland, Victoria, was damaged by lightning, apparently resulting in a blade being broken. (ABC on-line news) This is the only serious turbine damage due to lightning strike that I have heard of in Australia where there are over a thousand operating utility scale turbines (as of mid 2012).
Less fires started by lightning?Interestingly, while a lightning strike on a grassy or treed hill-top might well start a fire, if that hill is protected by a row of turbines the fire risk would be greatly reduced. Instead of being able to start a fire by striking the ground the lightning that strikes a wind turbine will be conducted safely to the earth.
In an electrical storm wind turbines will be hit by lightning just as communication towers and power transmission pylons have been struck by lightning for decades. Fires are rarely (if ever) started following a lightning strike on a communication tower or power pylon; similarly there is no reason to believe that a fire will be started by a lightning strike on a wind turbine.
On 2012/11/28 a neighbour of mine told me that he had seen multiple lightning strikes on the turbines of the Snowtown Wind Farm during a thunder storm a few days earlier; result – no fires. I have also received a record of twenty lightning strikes on a South Australian wind farm; result – no fires.
It may be claimed that wind turbines attract lightning. This is true to some extent; lightning will tend to strike anything that sticks up higher than anything else in the vicinity – hence the advice of not standing in an open field in a thunder storm. It is conceivable that the presence of wind turbines will very slightly increase the number of lightning strikes (because a slightly lower voltage build-up will be required to produce a strike over the slightly shorter distance from cloud to ground). But, so long as the towers stop the lightning strikes from causing a fire, what harm is there in this?
Interestingly, I don't think anyone likes the look of a line of power pylons. Wind farm construction requires the construction of a transmission line to take the power from the wind farm to the nearest point at which it can be fed into the main power grid.
If wind turbines are not built, other forms of power generation will have to be built. Is a fossil-fuelled or nuclear power station more aesthetically pleasing than a row of wind turbines?
Trees and other native vegetation have been removed from some ridges to allow the building of turbines and the access roads. At one time many Australians would have thought the removal of trees from land a step forward and an improvement, but I think that time is long past; most Australians now would prefer that trees be left in place.
I used to believe that this was simply a fabrication, or at least an exaggeration, of the wind power opponent groups, but unfortunetly some companies have attempted to do this (see the box on the right).
Wind farm companies have to come to agreements with land-owners about the use of land for the wind farm turbines. If any particular land-owner knew what the other land-owners were being offered then he would have an advantage in his negotiations with the wind farmers. Similarly, if a wind farm company has to buy-out the house of someone who has a problem with turbine noise, they do not want the details of the deal known to everyone. They may have to buy-out someone else later on, and knowing the details of any previous buy-out would give the person selling an advantage.
Any secrecy is undesirable in these sort of cases because secrecy leads to mistrust and suspicion. Any secrecy can also be used by wind farm opponents to cast suspicion on the motives of wind farm developers; with some justification.
Unfortunately it is normal business practice to try to minimise costs, so the wind farmers make their agreements with land-holders confidential. In real life, farmers quite probably will talk to their neighbours about how much they have been offered to host wind turbines; so it is questionable what confidentiality agreements achieve.
If the wind farmers hope to win the trust of the communities in which they are intending to develop their projects, they should minimise secrecy. Everyone knows that there is some secrecy/confidentiality, but by its very nature, no-one can know how much there is. Secrecy often leads to mistrust.
Had they agreed to have the turbines on their land then there would be no cause for friction with their neighbours who also had turbines, they would not have incurred any costs in opposing the development, their land value would have increased because of the increased income it generated, and they would have benefited from the development.
Wind farm opponents have said that Denmark is shutting-down wind farms because they don't work; this is quite false, Denmark continues to build more wind farms (many off the coast because of limited available land space – it is a densely populated country).
Denmark routinely produces more than 20% of its electricity from wind and has generated over 30% in a few months. There are plans to increase the share of wind power in Denmark up to 40%. It does power-share with Norway, a nearby country that has a lot of hydro-power.
In May of 2011 I was told that Denmark is to stop building wind turbines onshore and will only build offshore in future. I had an email from Karina Lindvig of the Danish Wind Energy Association stating that "there is absolutely no truth to that story".
A survey of over 16 000 Europeans by Eurobarometer conducted from February to April of 2002 found that "Denmark, Netherlands and Sweden place the most faith in renewables".
I would suggest that this in not a fault of the turbines or those who build the turbines, but an indictment of our greed for cheap and plentiful energy. So long as we want more and more energy it has to come from somewhere, and wind turbines are less damaging than most of the alternatives.
But actually propose building a wind turbine within two or three kilometres of someone's house and the likelihood of opposition increases greatly. The obvious conclusion is that this is simply NIMBYism (Not In My Back Yard). While there is a lot of truth in that, it's not the whole story.
There are a number of reasons why people might oppose wind farms. One is that some feel a wind farm is an unwarranted invasion and spoiling of the place that is their home and environment. Some people just don't like the look of wind turbines and don't want to have to see them every time they go outside. Many don't make a judgement based on ethical reasons; don't weigh-up the total good against the total bad. They are willing to forget about the global need to reduce greenhouse gas production (it is a problem that is invisible and largely in the future) and oppose the more immediate perceived 'blight on their landscape'. Unfortunately, in the case of wind power developments, many people listen to the abundent and varied lies spread by those who hate wind turbines, and are swayed by them; while if they knew the facts, they would feel differently.
It is becoming clear that, if local opposition to wind power is not to overwhelm general approval, there needs to be more reward for those people who host turbines in their vicinity, but do not currently receive any income from them. How this might be done, beyond the Community funding that often comes with wind farms, is not an easy question to answer.
And who should pay for it? Wind farms benefit the whole population by increasing the amount of renewable energy available; so should some compensation be paid out of taxation revenues? It would seem simpler and preferable if it were left to the wind farm operators, but care must be taken to not kill the goose that lays the golden egg.
|Turbines at sunrise|
North Brown Hill Wind Farm
"Taking figures from the start of the commercial wind energy industry in 1975 up to 2010, there have been 44 recorded fatalities (this includes a technician who reportedly committed suicide by hanging), an average of 0.054 deaths/GWey. Conventional fossil fuel industries have considerably higher rates, ranging from 0.197/GWey for natural gas, to 6.921/GWey for coal and 15.058/GWey for liquefied petroleum gas. The outlier is nuclear energy, with just 0.048 deaths/GWey due to accidents – although it should be remembered that the hazards associated with nuclear energy are much greater in the event that something goes wrong, with 'latent mortality' difficult to quantify."*GWey is an abbreviation for Gigawatt-energy-years, so the fatalities are related to the amount of energy produced in order to allow a comparison of safety in the various power generation industries.
On the other hand:
"Renewable Energy Target (RET) costs are forecast to comprise around 11% of the total increase in residential electricity prices at a national level. This increase in costs is related to an expansion in the renewable energy generation target from the Mandatory Renewable Energy Target of 9,500 GWh to the RET of 45,000 GWh by 2020. Other components of the residential electricity price include feed in tariff scheme costs and the costs of other state based energy efficiency and demand management schemes. Together these cost components comprise around 5% of residential electricity prices at a national level and are not expected to have a significant impact on the total residential electricity price over the reporting period in most jurisdictions."The report also gives 3% as the "contribution to national price increases" from the Renewable Energy Target.
PJM, the independent grid operator for all or parts of 13 US states produced a report that confirmed that wind energy is decreasing both the price of electricity and emissions of harmful pollutants. (See Into The Wind.)
Opponents of renewable energy (including the Liberal party) like to connect the proposed carbon tax with a rise in electricity prices. Energy prices are rising world-wide; and will continue to do so. The cheap sources of petroleum have been used up, those that remain cost more to exploit. Until recently consumption of electricity has risen steadily (in Australia and world-wide), this has led to a need from the building of expensive new electricity transmission and distribution infrastructure. Domestic solar power has helped to decrease the average demand for power from the electricity grid, but peak power consumption, so far as I know, has not declined, and the generation and transmission system has to be able to cover peak demand. Ultimately this must all be paid for by the end consumers of the electricity.
There is no justification for the claim that power prices would fall without a carbon tax.
Renew Economy has an informative article on the relationship of wind power to electricity costs in South Australia, dated 2012/03/21.
Heat wave of January 2014Giles Parkinson on RenewEconomy pointed out that solar and wind power forced wholesale electricity prices down. He quoted a report by Sinclair Knight Merz:
"We conclude that wind generation is likely to have significantly reduced the price impact brought about by sharply rising demand during the heat wave period. In the seven days to 19 January, wind farms contributed around 6 per cent of overall supply in SA and VIC, and as a consequence, wholesale prices were at least 40% lower (on a consumption weighted average basis) than they would have been without the contribution of wind."
ACT has the highest renewables target and lowest electricity pricesSophie Vorrath, writing for RenewEconomy says that the proposed development of up to 550MW of wind, solar and waste to energy projects, working toward their 90% renewables target (by far the highest on the mainland), will help them retain the lowest electricity prices of any state or territory in Australia.
No wind turbines damaged in major 2011 Tohoku Japanese earthquakeKelly Rigg wrote the following in the Huffington Post on 2011/03/17.
"Colleagues and I have been directly corresponding with Yoshinori Ueda leader of the International Committee of the Japan Wind Power Association & Japan Wind Energy Association, and according to Ueda there has been no wind facility damage reported by any association members, from either the earthquake or the tsunami. Even the Kamisu semi-offshore wind farm, located about 300km from the epicenter of the quake, survived. Its anti-earthquake "battle proof design" came through with flying colors."The catastrophic failure of the Fukushima nuclear power station due to the tsunami caused by the earthquake is well known.
Also see the Wikipedia article.
|The Moon and a turbine|
One need only look at the US experience to see that agriculture and wind power are very compatible. The top three US states by value of agricultural production are also the top three states by installed wind power.
The figures for agricultural production above were obtained from Stuff about states, dated 2004 (I was unable to find more recent data), and the figures for wind power were from Wikipedia, dated the end of 2012.
Another section of this page deals with the relationship between wind turbines and aerial agriculture.
On 2014/02/06 I contacted CASA Aviation Projects asking for more information on the aircraft accidents. They were unable to provide any more information on the claims, nor contact details for the authors, so some doubt about the veracity of the claims exists.
On 2014/04/28 it was reported that a light plane crashed "into a wind farm" in South Dakota, USA. The weather was foggy at the time. The reason the plane was flying so low was not reported. (In Australia at least, it is illegal to fly so low except in special circumstances.)
At the end of 2012 there was 274GW of installed wind capacity world-wide; probably around 200 000 utility scale turbines and roughly the equivalent, in capacity, of about 100 000 modern turbines. Wind turbines would be easily avoided as they are large and conspicuous.
Power lines, especially the thin wires used for supplying rural homes, stretched between poles that may be 500m apart, are a major hazard. Collision with power lines do happen, and the construction of wind farms involves building more power lines.
This is my own opinion; a pilot who can avoid power lines that are almost invisible except within a hundred metres or so should have no difficulty at all in avoiding something as huge and obvious as a wind turbine.
Aerial spraying should be done in calm conditions because of potential spay-drift; in calm conditions the turbines will be still. They typically do not start generating electricity until the wind speed reaches four metres per second, so during spaying operations there will not be any turbulence created by the turbines to bother the aircraft. I have been told that some aerial agricultural operations, such as mouse baiting and the application of fertiliser, are best done from altitudes higher than wind turbines.
I have been informed that it is standard procedure for any farmer who agrees to have wind turbines on his property to also agree to not use aerial agricultural methods – for insurance reasons. If this is so, then the loss of business to aerial agricultural operators would explain why they seem to be opposed to wind farm development.
The AAAA make the point that the presence of wind turbines on land affects, not only the operation of aircraft on that land, but also on nearby land. While the owners of the land with the turbines are financially advantaged by the wind farmers, neither the owners of the nearby land nor the aerial operators receive any compensation for any economic harm done to them.
From my reading of the AAAA document the main concern is the economic impact that wind farms have on the 'aerial application' industry. The document does not include the word 'turbulence'.guidelines document on wind turbines. While the document did not give anything definitive on turbulence, it did say:
"There is evidence of considerable research activity on modelling and studying the wake characteristics within wind developments, using computational fluid dynamics techniques, wind tunnel tests and on site lidar measurements. A thorough literature survey would be necessary to establish the scale and the advances of the research findings."and:
"... the CAA has received anecdotal reports of aircraft encounters with wind turbine wakes representing a wide variety of views as to the significance of the turbulence. Although research on wind turbine wakes has been carried out, the effects of these wakes on aircraft are not yet known. Furthermore, the CAA is not aware of any formal flight trials to investigate wake effects behind operating wind turbines."
I have not been able to find much credible information on this matter. I'd be pleased to hear from anyone who knows of any. On 2012/02/01 I emailed the Civil Air Safety Authority of Australia (CASA) inquiring about light aircraft and wind turbines. I had received no reply by 2012/02/18.report was done for Transfield by Rehbein Airport Consulting.
Relevant to this subject the report states:
"A wake length equivalent to 6 times the rotor diameter is considered a minimum in wind conditions of 10-15 knots [18-28 km/h or 5.1-7.7m/sec]. When the wind turbines are operating in winds of 15 knots [28 km/h or 7.7m/sec] or greater the wake from a single turbine is still prevalent at 10 blade diameters and can persist for up to 16 blade diameters downwind of the turbine. The majority of modern wind turbines reach their maximum output, and in theory, generate the strongest wake turbulence in wind speeds of approximately 47km/h [25 knots or 13m/sec]. At this speed, and in combination with the wake produced by other turbines, the wake may exist up to 5km downstream from a large turbine cluster of several rows.
"Unlike most of the mid-north, the Yorke Peninsula is relatively flat and predominately farmed densely for wheat, barley and legumes. Due to these farming practices it has been argued that aerial spraying may not be possible for neighbours of the wind farm if wind turbines are installed. At the moment we are attacking this issue via a 4 tier study;The Ceres Project is a very large proposed wind farm with undersea cable connecting to Adelaide. Managing the risk to aviation safety of wind turbine installations (wind farms)/wind monitoring towers" on 2012/07/15.
I quote the section of this document that dealt with turbulence in full:
"Wind farm operators should be aware that wind turbines may create turbulence which noticeable up to 16 rotor diameters from the turbine. In the case of one of the larger wind turbines with a diameter of 125 metres, turbulence may be present two kilometres downstream. At this time, the effect of this level of turbulence on aircraft in the vicinity is not known with certainty. However, wind farm operators should be conscious of their duty of care to communicate this risk to aviation operators in the vicinity of the wind farm. CASA will also raise awareness of this risk with representatives of aerial agriculture, sport aviation and general aviation."Note that the document states "turbulence which [is] noticeable" and "turbulence may be present two kilometres downstream". There is no suggestion that this level of turbulence is dangerous to aircraft.
Aerial spraying of insecticide and herbicide can only be safely done when there is little or no wind. At other times the spray will drift off-target. When there is little or no wind, wind turbines will not be operating and so will not create turbulence. It should also be remembered that many things create turbulence in the wind; trees, hills and coastal cliffs are common examples, even convection on a warm day can cause turbulence.
So far as I have been able to discover, no aircraft, anywhere in the world, has ever crashed into a wind turbine or due to turbulence from a wind turbine or wind farm.
HearsayI have been told of a helicopter pilot who made a point of flying backward and forward on the downwind side of a South Australian wind farm. He may not want to be identified so I will not give information on the helicopter or wind farm involved. I was told that he was wanting to test whether the turbulence would have any effect on his aircraft; and found no noticeable effect at all.
There are several reasons I cannot believe that the problem she had had anything to do with the turbines. One reason is this: I slept under those same turbines on the night of 2012/02/09 (my swag is visible behind the car in the photo on the right). (The turbines were operating all night, at varying speeds.)
I noticed no pressure changes in my ears at all – indeed, I had a perfectly good night's sleep.
She was 4000m from the turbines, I was maybe 80m (right underneath). So she was 50 times as far away as I was. Using the inverse square law of physics, that would indicate that any sound (sound is vibrations in air pressure) from a single turbine where she was would be 50 x 50 = 2500 times weaker than where I was. (An adjustment would need to be made because she was probably roughly equally distant to a number of turbines. But even allowing for this the sound intensity where I was would be hundreds of times higher than where she was.)
Wind farms, and sustainable energy in general, are necessary if the world is to limit climate change. Some people, perhaps those who tend to look at 'the bigger picture' or 'the greater good' will see a proposed sustainable energy development as being desirable and a cause for pride in their area.
On the other hand, many people will see a wind farm as an intrusion into their neighbourhood. If they do not see wind power as desirable and necessary they might be offended and believe it to be an imposition that is being pushed onto them by big business or government. This is related to NIMBYism, but is not entirely that. These people quite probably feel protective toward their immediate vicinity. Some of them will have worked to improve their locality in some sort of voluntary capacity.
The only answer to this problem (I consider it to be a problem, others may not do so) would seem to be to try to make people understand how disastrous unmitigated climate change will be and therefore to see the urgent need for the development of sustainable energy.
and others have tried to explain how illness may be caused by wind turbines
by claiming that wind turbine sound can be louder at a distance
than it is close to the turbine.
Dr Laurie has been reported as saying "You can stand underneath the turbines
and not hear a thing, but up to five kilometres away they can sound like a jet
engine or a low rumble or a washing machine."
This is absurd, a physical impossibility!
(I've studied wind power for years and visited most wind farms in SA, Victoria and WA; the greatest distance I've ever heard wind turbines from is 2.5 km and then they are barely audible in ideal listening conditions. See elsewhere. The dose-response principal of epidemiology is also relevant to this point.)
Apart from the laws of physics one simply needs to visit a wind farm to convince oneself that the 'louder at a distance' claim is nonsense. As you move from turbine to turbine it is always the nearer ones that you hear, you never hear those further away drowning out the nearer ones.
There are some special circumstances where sound might diminish by something less than the inverse-square of the distance, over a flat surface (such as water) and where there is a temperature inversion, for example, but still it always diminishes with distance. Hills and valleys could direct sound in some directions more than others, but this does not stop the sound diminishing with distance. And when a number of turbines are involved, while you double your distance from one, you might not be doubling your distance from others; the sound level you hear depends on all of the turbines and their distances.
Some sounds from turbines can be stronger in some directions than in others (from my own experience).
It is possible that once in a while pulses of sound coming from different turbines at regular intervals could arrive at a particular spot simultaneously and reinforce each other. Such pulses from two turbines would double the sound intensity at a point, that is increase it by about 3dB, from three turbines the sound would be increased by 4.7dB. Sounds from two turbines combining would happen occasionally, from three more rarely, and from more than three very rarely. See also noise and wind turbines.
Motivation is related to attitude and a person's attitude to wind power has a big affect on whether or not they are likely to believe they have been made sick by nearby wind turbines. I have discussed my motivation elsewhere.
I have dealt with the question of Why support wind power elsewhere, so will try not to repeat those points here.
In the simplest case we have two choices: business as usual, or tring to limit climate change and its speed of onset.
Ethics, moral philosophy, is about balancing our personal wants and needs against those of other people, and, I have argued, against the needs of all other life on Earth: the biosphere. Climate change modelling indicates that thousands or even millions of species are likely to become extinct and millions or even billions of people will be displaced if we do nothing; there will be terrible wars over land, water, and food. In any view of ethics such dire damage in the future would oblige taking serious action in the present to avoid or limit climate change, if such action is possible and can be achieved without huge costs.
That we can do something without huge costs has been shown by the South Australian experience: in early 2003 SA had no wind power, in 2011, 26% of South Australia's electricity was generated by wind power and over the same period the percentage of coal-fired electricity decreased from 42% to 25%. The financial cost has not been great, while the price of electricity in SA has increased, the increases are no greater than elsewhere and have been ascribed mainly to the costs of updating old infrastructure in the transmission system, rather than having anything to do with the cost of building and integrating wind power.
What costs and benefits have there been in developing the wind power in South Australia?
Environmental costs and benefitsThere are environmental costs involved in developing wind power, a number of them are discussed on this page. However, the environmental costs of not developing renewable energy – letting climate change continue unabated – will be far greater.
Economic costs and benefitsIt is difficult to be sure, but wind power is probably more expensive than electricity generated by burning fossil fuels (unless you add in the environmental costs of the fossil fuel option). (Fossil-fuel power is subsidised through subsidies given to the mining industry; the Australia Institute has estimated these subsidies at $4b per year.)
Of course SA cannot get by on wind power alone, the wind doesn't blow all the time, alternative power sources had to be retained. If much more wind power is developed, we will have to look at sustainable methods of generating electricity, including pumped hydro-power.
The wind farms have brought with them jobs for local people, business for local contractors, stores, hotels and other providers of accommodation. Many wind farms provide community development funds for the people in the vicinity.
Social costs and benefitsI live in Mid-North South Australia where there is a greater concentration of wind farms than anywhere else in Australia and where you might expect social costs to be at their highest. There are some people (estimated at a vocal half-dozen) in the vicinity of the Waterloo Wind Farm who are very vocal in their opposed to that development; there are several (perhaps another half-dozen) in the vicinity of the Hallett wind farms. Of course there are others who are less vocal elsewhere.
At least some of these people claim health problems due to the turbines; on another page I have explained at length that there is no acceptable evidence for more than annoyance and some sleep deprivation being directly due to wind turbines. There is certainly fear and anxiety in some people, but these are brought about by causes other than the turbines; the fear and anxiety can lead to some serious health problems.
Certainly some people feel that there are already enough wind turbines in the Mid-North; they would rather not see any more. This is a point of view based on aesthetic preferences.
One must then consider the social benefits. While some people don't like the look of wind turbines, others, like me, consider them graceful, elegant, and symbols of a more responsible future. Had the wind farms not been built more coal-fired power stations might have been, with consequent health problems that come with the toxins that they release into the atmosphere.
I hold, therefore, that the net social costs of wind power have been slight, and far outweighed by the benefits, especially if you consider slowing climate change as one of the benefits.
I have skimmed over the philosophical points above very lightly; I apologise for that. As for everything on these pages, I welcome reasoned comment, my email address in near the top of this page.
bird deaths section.
Links relating to wind turbines and health are on my
General links relating to wind power are given on my
Wind links page.
Recommended sources of information...
Mike Barnard has written an excellent summary of wind power myths and what the facts are.
The Australia Institute is an independent public policy research centre funded by grants from philanthropic trusts, memberships and commissioned research. It has a 134kB pdf document about The facts and fallacies of wind power.
Another useful document is "Wind Energy: The myths and the facts", from Sustainability Victoria, the full URL of the page is "http://www.sustainability.vic.gov.au/www/html/ 2148-wind-energy-myths-and-facts.asp".
The Clean Energy Council also provide fact sheets on wind farms, but they could hardly be called a disinterested party.
Paul Gipe wrote an excellent review of a book (the book was written in French, the review in English), edited by Vincent Boulanger and titled Wind Turbine Noise: Rumors, Gossip, Lies, and Stories. Obviously the fallacies about wind power are not confined to English-speaking countries.
Wikipedia has an extensive page on the Environmental effects of wind power.
An expert panel review of "Wind Turbine Sound and Health Effects" conducted for the American Wind Energy Association and the Canadian Wind Energy Association was available from the American Wind Energy Association (but the original link is no longer working).
Rational and informed arguments from anyone disagreeing with any of the
points made on any of my pages are welcome.
Do not expect me to change anything if you do not give convincing evidence
in support of your arguments.
My email address is near the
top of all my pages.
Suggestions of additions are always welcome, compliments particularly so.
What constitutes valid evidence?First, some examples of things that are not convincing evidence:
Some examples of valid evidence:
A good night's sleep at Waterloo
Abandoned homes at Waterloo?
Abatement intensity – table
Access roads help fire-fighting
Aerial fire-fighting and wind turbines
Agriculture and wind farms; are they compatible?
Agricultural Aviation Expert Witness Report
Air navigation lights
Are other countries abandoning wind power?
Barotrauma and bats
Barriers to animal movement
Bats killed by wind turbines
Bird deaths from wind turbines
Bird deaths at Waubra
Bird mortality - graph
Blade failure in wind turbines
CO2 and wind farms
CO2 released from wind-farm concrete
CO2 released per MWh - coal
Can a wind farm change the local climate?
Can wind farms affect rainfall?
Can wind farms affect temperatures?
Can wind power provide base-load
Can wind power provide peak-load
Carbon intensity – table
Conflict-my own experience
Cost of electricity
Cost of renewables to the consumer
Cut-in speed (of turbines) and bat deaths
Denmark and wind power
Do environmentalists oppose wind farms?
Do turbines frighten animals?
Do wind farms cause social conflict?
Do wind farms get government money?
Does wind replace coal?
Dr Cindy Hull on birds
Dubious fire claim
Earthquakes and wind turbines
Efficiency of wind turbines
Electricity generated must be consumed
Embodied energy in turbine tower
Emissions intensity – graph
Energy consumed in wind farm construction
Energy payback time for wind turbines
Erosion of sites
Factors, wind vs solar
Feeling of place
Financial support for wind power in Australia
Fire hazard without wind farms
Fragmentation of bird habitat
Fraud – speculation
General environmental concerns
Generally popular, locally opposed
Gradual variation when many wind farms
Groundwater and wind turbines
High temperature shut down
Honey bee problems?
How much electricity do wind farms generate?
How much power do wind turbines use?
How does wind power compare to roof-top solar?
How much CO2 does wind power save?
Hull, Dr Cindy, on birds
Inequible spread of financial benefit
Infrasound: low frequency noise
Infrasound: Geoff Leventhal
Infrasound: Peter Seligman
Is solar better than wind?
Lack of consultation?
Lack of support for local community?
Lack of transmission lines
Land values and wind farms
Leakage of oil
Life of wind turbines?
Light aircraft, agriculture and wind turbines
Light aircraft and wind turbine turbulence
Links: Wind farms and weather
Louder at a distance?
Motivation of proponents and opponents
Mt Emerald Wind Farm aeronautical assessment
NIMBY; not in my back yard
Noise; my own experience
Noise and wind turbines
Noise complaints when turbines not operating
Noise sources other than wind turbines
Paucity of information from operators
People driven from their homes?
Power curve of a wind turbine
Power from all wind farms: combined 2012/01/15 – graph
Power from all wind farms: individually 2012/01/15 – graph
Power used when turbine not generating
Pressure in the ears
Pygmy bluetongue lizards
Relative efficiency of turbine - graph
Relative efficiency of turbine - table
Renewables are suppressing electricity prices
Roads and road damage
Regional variation in generation
Retail electricity prices
Room (sound) modes
Solar complements wind
Specific wind power problems
Tasmanian wedge tailed eagles
TV reception and wind turbines
Timing of wind power generation
Too many turbines
Turbine footing (or foundation)
Turbine wake plumes and aircraft movements
Turbulence from wind turbines
Valid wind power problems
Weather - turbines and surface roughness
Why do people object to nearby wind farms?
Wind farm effect on tourism
Wind farms reduce CO2 emissions
Wind is variable
Wind power generation in one month
Wind power not the answer
Wind power problems
Wind speed range of turbines
Wind turbine litter
Key word indexThis index concentrates on the one most relevant word. (Many subjects cannot be indexed by a single word)...