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These pages are independent of 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 2010/03/05 About these pages Contact: email daveclarkecb@yahoo.com |
What follows is an independent point of view from someone with no reason to either gloss over, or exaggerate, the problems and limitations of wind turbines and wind farms. Sadly, in my experience groups opposed to wind farms are not above lying to try to gain public support for their stance, on the other hand the wind farm companies emphasise 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 have written a bit on the advantages of wind power and on the pros and cons of various methods of generating electricity elsewhere.
As in so many things, the NIMBY factor (Not In My Back Yard) is often very much involved when people object to wind farms. 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 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, so we must build sustainable energy supply systems.
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Table, Factors, wind vs solar | Relative efficiency of turbine Graphs, Wind power generation in one month | Power curve of a wind turbine | Relative efficiency of turbine |
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Home Wind home Top Index |
Is wind power the answer to greenhouse and climate change?Some people, David Bellamy is a vociferous example of this group, object to wind farms saying that they are not the answer to greenhouse. Their problem seems to me to be a too high expectation. Wind power is not the answer, it is however a part of the answer to a very big problem, the biggest single problem Man has faced to now.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 way of achieving most of the above points. |
Are wind turbines noisy?
Wikipedia states the following: "Modern large turbines have low sound levels at ground level. For example, in December 2006, a Texas jury denied a noise pollution suit against FPL Energy, after the company demonstrated that noise readings were not excessive. The highest reading was 44 decibels, which was characterized as about the same level as a 10 mile/hour (16 km/h) wind."I have visited many wind farms in Australia (all those in SA and Victoria up to the time of writing (April 2009), and several in WA. No matter what the strength of the wind, one has no trouble conducting a normal conversation immediately beneath a modern utility scale wind turbine (for example, greater than 1 megawatt). The sound can vary from minute to minute, depending on the direction of the wind in particular; it seems that a greater level of noise can result from turbulance when air flows over a turbine blade at some angle other than the optimal. It may be possible to hear turbines up to distances of, say, one kilometre given the right wind conditions, but I don't see how anyone could honestly say that they were noisy. However, it could well be true that some people living between 500m and 1.5km from a turbine find that the sound does keep them awake at night, when the wind is from certain directions and at certain strengths. (I believe that the French equivalent of the Australian Medical Association has ruled that wind turbines should not be built closer to a home than 1.5km.) When wind farms are built wind farmers either buy those houses that are close to proposed turbine sites or arrange the sites so that they are at least 400 to 500m from occupied houses. I have camped overnight beneath the turbines of Starfish Hill wind farm and had no problem at all getting a good night's sleep; the sound of the turbines, if anything, was relaxing. I recognise that this is subjective and that the experience of others may be different.
Infrasound: low frequency noiseInfrasound is sound of such a low frequency as to be inaudible to humans. There have been claims that infrasound (not just from wind turbines) has caused health problems, but this seems to be controversial.There have been claims that infrasound has caused illness near the Waubra wind farm in Victoria. ABC on-line news reported the following, 2009/11/04: An engineer from the University of Ballarat says tests have revealed that the turbines at the Waubra wind farm, west of Ballarat, do generate a low frequency noise. Residents near the wind farm say the sound is damaging their health. Engineering lecturer Graeme Hood says his noise recording equipment recorded low frequency, inaudible sounds between 60 and 80 decibels. He says that is well below what is internationally recognised as being detrimental to health. "The current thinking I suppose from the experts is that [for] infrasound [to] have some effect on the human body, [it] needs to be up around the 120 decibels," he said. "Now if that was an audio level, you don't need much more to make your nose bleed, you know it is a very loud noise, even though you can't hear it. We didn't find anything like that of course." | |||||||||||||||||||||||||||||||||||||||||
Do wind farms have health effects?
I have not found any credible evidence that there is special or unusual health effects associated with wind turbines. I believe that flashing light can bring on epileptic fits in people who are susceptible to the latter. In places close to turbines – no further than a kilometre or so – for short periods during the day and at particular times of the year, the moving turbine blades can pass in front of the sun and cause the sunlight to flash. This can be annoying, but I have never heard that it caused any harm to epileptics or anyone else. How close should a turbine be to a house?I'm not at all sure of this but believe that in Australia some turbines have been permitted within 500m of houses. A Victorian parliamentarian, Peter Kavanagh, has said that "The equivalent of the AMA [Australian Medical Association] in France, has put out a policy and it says that wind farms shouldn't be located within one-and-a-half kilometres of residences". The expert panel review discussed in the box on the right did not make definite conclusions about how far turbines should be built from houses, but did say that setbacks of as much as a mile (approx. 1.5km) were not warranted.
The minimum distance that a wind turbine should be from an occupied house is
largely a matter of opinion and is therefore difficult to determine.
Nina Pirpont's research into the health effects of wind turbine noiseAn article in the South Australian press on 2009/08/04 dealt with a study by pediatrician Nina Pierpont who is reported to have stated that wind turbines "can lead to a greater risk of heart disease, panic attacks and migraines".Pirpont has made a number of claims about health problems experienced by people living within 1.5km of wind turbines; including sleep disturbance, headaches, tinnitus, dizziness and nausea in a book that she apparently self-published. (It is notable that this research has apparently not been published in any peer-reviewed scientific journal.) The author's net page is at http://www.windturbinesyndrome.com/, a page criticising Pirpont's work is at "http://www.grist.org/article/ 2009-08-03-attack-on-industrial-wind-puffed-with-false-peer-review-claims/" (there are no spaces in this URL). My impression is that valid questions have been raised about the claim that Pirpont's book was properly peer-reviewed and there seem to be valid criticisms of her methodology; in particular it seems that Pirponts subjects were few (28) and apparently selected because they claimed to have health problems associated with wind turbines, and there was no control group. This is not to say that she is necessarily wrong. |
Do wind farms cause social conflict?It has been alleged that "wind farms cause significant, long-standing social conflict and division within rural communities." 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."In the area that I live in (Mid-North South Australia), within 60km of several of Australia's biggest wind farms, few people oppose wind farms in themselves; some people are quite reasonably concerned with conserving environment in wind farm areas. I have not heard of any significant social conflict in the region due to wind farm construction. There are other areas where 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. Isn't it just as valid to say, rather than "wind farms cause social conflict", "wind farm opponents cause social conflict"? The fact is that any industrial development, especially a conspicuous one, is likely to cause some conflict in some cases. |
Paucity of information from operators
Many wind farmer's Net sites give minimal data and are rarely updated. Internet sites are easily and cheaply updated and the operators must have the information. One wonders why they are so stingy about sharing it. 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 I have not been able to get actual water consumption figures from wind farmers. 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. They are also holding back the development of the technology to the detrement of the nation's take-up of sustainable energy. 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 many cases.
Some in the industry only provide information in the form of PDF files; in some cases these are so large that anyone on a limited download plan, or only mildly interested, would not look at them (for example TME Australia had one that was 5MB). HTML can be much more efficient; this page, for example, including images, is about 180kB. Most, if not all, wind farm operators do not like to release the records of the amounts of power that their wind farms generate. A common claim from many wind farm oponents is that wind farms do not generate significant amounts of electricity. How can the public gauge the truth while the wind farm operators hide the facts? 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. |
Do wind farmers consult sufficiently with local communities?A resident of Hallett, where AGL has one wind farm operating and another under construction, complained to me that AGL had very little consultation with the local community before committing to build their wind farms. As of the time of writing (January 2009) I do not know whether this is true, but have inquired (AGL have not responded to a number of my inquiries).In my own experience Pacific Hydro who is building the Clements Gap wind farm in the Crystal Brook area, consulted widely with the local communities. Roaring 40s, the developers of Waterloo, Stony Gap, and Robertstown wind farms also seem to be making a good effort to inform the local people. |
Do wind farmers support local communities?There are several wind farms near Hallett (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). So far as I know, most wind farmers do support the local community. For example, Pacific Hydro, which is building a wind farm near my home town, Crystal Brook, is to give $50 000 each year for community projects for the life of the wind farm. |
Are wind turbines just a short-term source of sustainable energy?A complaint about wind power that came up in conversation was that wind turbines have a short life and that we should be looking for long-term answers to energy supply, such as solar.In fact modern (~2009) wind turbines have an expected life span of around 25 years; typical solar photovoltaic panels are guaranteed for twenty years. Solar thermal or concentrating photovoltaic systems have not been around anywhere near twenty years so their life-spans are unknown, but I would think they would be unlikely to last any longer than 25 years, at least without major rebuilding. 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 dilema, 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. |
Efficiency of wind turbines
From an environmental point of view, 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. In the case of fossil fuels, efficiency is very important. Fossil fuels are a finite resource, we can only use them once and then they are gone; and when burned they release pollutants into the atmosphere. It is essential that we minimise the amount of fossil fuels we burn and maximise the amount of energy that we extract from every tonne that we do burn. On the other hand, wind is a renewable resource, we can never use it up, and the process of taking energy from it produces no pollution. Also, if a particular turbine takes little energy from the wind that passes through it, the main result is that the velocity of that wind is not much reduced. (The turbine might produce turbulance, this has environmental implications and has been discussed elsewhere on this page). 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 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
speed winds.
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.
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Are wind turbines a fire hazard?There have been two fires in wind turbines in South Australia that I know of. Neither of these caused a bushfire, but the possibility is there.The area around the base of all turbines is kept clear of vegetation, but a fire in the nacelle, on top of the tower, could result in sparks and burning material falling on the ground at a distance from the tower. The turbine access tracks would help emergency services access any fire. |
Wind turbines and television receptionA complaint against one of the Hallett wind farms was that the turbines had very badly affected television reception in the area. I was told that reception had become so bad that the wind farm operator had installed satellite dishes on the affected houses.Brendan Ryan of Suzlon has given me some information on this: "AGL is pretty far down the track in putting a whole new TV tower in the Mid North to cover the reception problems. They are real and have always been the main issue with windfarms. The geography doesn't do any favours either and of course there is a lot of perception associated with TV. If the resident can see strobes across their TV picture, chances are it is due to the windfarms." |
Weather radar interferenceThe moving blades of the wind turbines cause some problems to the operators of weather radars. Large stationary installations also cause radar reflections, but these are more easily compensated for. |
Is solar power somehow 'better' than wind power?Some people seem to believe that solar power is somehow better or more environmentally friendly than wind power.
How should we judge which is 'better'? Logically we need to look at the cost, in both financial and environmental terms, of each in relation to the amount of electricity generated; and we should look at how wind and solar fit the electricity demand cycle. 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 (although there is still a bias toward the old fossil fuel power generation methods rather than anything sustainable). The people who invest their money in wind farms and the business people running the companies that build wind farms are not stupid. What are the factors involved?
The table above shows that deciding whether solar or wind is the least environmentally damaging is not easy. | ||||||||||||||||||||||||||||||||||||||||
Leakage of oilLeaking lubricating oil or hydraulic fluid may be a problem. Fluids running down turbine blades may be scattered over the surrounding area, in some cases causing contamination of drinking water.Of course the potential of this would be similar to any other machinery in operation, for example, farm tractors and earth moving equipment. |
Erosion of sitesA complaint heard from a Hallett resident was that the building of roads and hardstands in the hills of the area was going to lead to terrible erosion problems in the future. I should record here that I have visited many wind farms and am yet to see significant erosion caused by them.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 turbinesOne of the most commonly heard complaints against wind turbines is that the fast moving turbine blades kill birds; this is true, but the numbers of bird deaths seem not to be great. 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 three Australian wind farms is between 0.23 and 2.7 birds per turbine per year. Far more birds are killed in collisions with steel-lattice towers, power lines, house windows, cars etc. Several of the world's bird protection organisations hold that climate change is a far greater threat to birds than are turbines. 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:
Wikipedia states that... "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." Testimony given by Audubon (the major bird-welfare group based in the USA) to the US Congress is available in the page, Congressional Testimony on Benefits of 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. If readers know of independent scientific studies of bird (and bat) mortality in Australian wind farms I'd love to add some of the results here. |
Fragmentation of bird habitatI have received correspondence from Chia-Yang (John) Tsai of the Changhua Coast Conservation Action, Taiwan. He stated that his studies indicate that while bird collision has not been a significant problem, the fragmentation of bird habitat by wind farms can be.
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). |
Pygmy bluetongue lizardsThe pygmy bluetongue, Tiliqua adelaidensis, is classed as an endangered species and occurs in grasslands of Mid-North South Australia; the same region as the Hallett wind farms. A few populations occur in the Port Wakefield to Balaklava area.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 at least ten of these sites. Soil disturbance in lizard habitat does destroy 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 plowed land, and are very slow to re-occupy plowed land. |
Loss of native vegetationIn Australia wind farms are usually built on the tops of ridges; bare, rounded ridges are prefered by the wind farmers because the air-flow is less turbulant.
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General environmental concernsSpecific environmental concerns such as bird and bat deaths, fragmentation of bird habitat, visual objections, erosion and effects on tourism and 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.
The question of whether a wind farm can change the local climate is dealt with elsewhere on this page, and I have discussed whether very extensive development of wind power Australia-wide might affect weather on the Wind power potential page. |
Do turbines frighten stock?
The argument that wind turbines frighten sheep, cattle, horses or other livestock is one that is used by wind farm opponents periodically. I think the photograph above shows that, if ever turbines do frighten stock, the stock become accustomed to the turbines and behave quite normally in their near vicinity. Whether there is a period during which stock 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 fealing is that neither cattle nor sheep would be much concerned by wind turbines. I'd be pleased to receive any first-hand information on this question. |
The wind doesn't blow all the time
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A part of this problem could be overcome by introducing Supply Dependent Load, which is discussed in my Sustainable Electricity page.
Sometimes too much energy can be generated by wind farms; this could cause overloading problems in the electricity grid. NEMMCO 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 important, the article stated that there had been no need to constrain production from the turbines at any time.
The fact that wind farms are wide spread in Australia helps. If the wind slows in one area chances are that it will still be blowing in other places. Unfortunately much of Australia's wind power is concentrated in south-eastern Australia and if this area is covered with a meteorological high pressure area then much of the country's wind power will not operate. WA is not on the National Power Grid so even if the wind is blowing in WA it is of no help to eastern Australia.
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.)
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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. It should be possible to set up desalination plants to run when there is excess electricity. Electricity can not be 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. This and other suggestions for solving the problem of variability of supply of sustainable energy are discussed on my Sustainable Electricity page.
Improved wind forecasting would provide forewarning of changes in the quantity of wind-generated electricity entering the grid.
Wind turbines shut down when the temperature goes above 43 degreesFrom Terry Teoh of Pacific Hydro:"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.) |
Bat deaths
The article stated that most of the bats were common species including red bats, eastern pipestrelles and hoary bats. What was of great concern was the fact that quite probably only a small percentage of the bats killed were being found. Little research seems to have been done into this potential problem in Australia. I believe that Brett Lane and Associates of Melbourne wrote the wind industry's 'best practice' guidelines on bat and bird monitoring. Some further information was available at Safewind (link no longer available). This page indicated that the greatest problem is with migratory species, presumably because they fly higher than hunting bats. 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. Death by barotraumaAn article printed in the New Scientist, 25th August 2008, discussed a new study by Erin Baerwald and colleagues of the University of Calgary in Canada that showed that many bat deaths at wind farms were caused by the sudden drop in pressure near wind turbine blades. This causes the bats' "delicate lungs to suddenly expand, bursting the tissue's blood vessels. This is known as a barotrauma, and is well known to scuba divers". The study's data suggested that this was the sole cause of 50% of the bat deaths examined in southern Alberta, and was at least a contributing cause in 90% of deaths. The article can be read at New Scientist. |
Wind farms cause power surges?Apparently, if wind power becomes a major component (say greater than 10%), power surges due to gusting of wind at wind farms can cause problems in a power grid.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. |
Can a wind farm change the local climate?Can wind farms affect rainfall?
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.
Turbulance from wind turbinesIt has been suggested that the turbulance caused by wind turbines causes increased mixing in the lower layers of the air and that this has an affect on the local weather.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." Can wind farms affect temperatures?There is some research indicating that local temperatures might be increased by up to 2 degrees by wind farms. It seems logical that a slight temperature increase might follow from the lowering of wind velocity due to the turbines; the wind takes some of the heat from the soil, animals, buildings, etc. Slowing the wind would reduce this effect.It is also a possible that turbulance from wind turbines could cause changes in the local temperatures.
These questions deserve research.
Turbines increase the 'surface roughness' of the landWind blowing over bare flat land moves with little friction. Wind blowing over forested land is much more affected by the friction in the lower layers due to blowing through the trees. Wind farmers talk of the degree of 'surface roughness' and its effect on wind flow.An array of turbines will have a similar effect on wind flow, they will slow the wind at lower levels due to the energy that they take from it and the turbulance 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. 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.
Links/research on wind turbines and weatherIn a Net search I was unable to find any research into the likely or actual effect of on-shore wind farms on local rainfall. This seems to be a significant lack.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 availble, 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. "Weather response to management of a large wind turbine array" by D.B. Barrie and D.B. Kirk-Davidoff (3.4MB) can be downloaded at www.atmos-chem-phys-discuss.net/9/2917/2009/acpd-9-2917-2009-print.pdf. It discusses modelling of the effect of a continent-scale wind farm on US weather. |
Is the energy consumed in construction of a wind farm comparable to the energy that farm will produce?Some 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.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 studdy 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.
The related question of the carbon dioxide balance of wind farms is covered on this page in CO2 and wind farms. Pacific Hydro state 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". Considering my calculations below on the pay-back time for the CO2 released in the manufacture of the concrete foundation of a wind turbine, the above statements seem quite reasonable. A publication of Wind Energy (Denmark) dated December 1997 states that the energy payback time for a 600kW turbine is 3.1 to 3.8 months and Suzlon estimated that the energy payback time for Clement Gap wind farm will be five months. |
Is the carbon dioxide released in wind farm construction comparable to the amount that will be saved by using wind power rather than some form of fossil fuel?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. I have looked into this question in some depth because a friend was concerned by it. Joseph Davidovits, Geopolymer Institute, Saint-Quentin, France states: "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 1.5MW 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 1.5MW 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.Since doing the above calculations I have been informed (May 2007) by Peter Reed of Suzlon (Australia) that while 216 tonnes of concrete is sufficient for the footings of the Suzlon 2.1MW turbines being constructed at Hallett Wind Farm (where they are able to use rock anchors), 800 tonnes of concrete would be required for a 'gravity footing' for the same turbine. I believe this would be used where the turbine was to be constructed in an unconsolidated sediment foundation. Less than a week of operation would be required to 'pay back' the CO2 released from the manufacture of the approximately 80 tonnes of cement in these 800 tonne footings. |
Do wind farms really save carbon dioxide emissions?Some who object to wind farms claim that the amount of CO2 released during wind turbine manufacture and wind farm construction is greater than the savings that result from wind farms displacing fossil-fuelled electricity.
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." I have written about my own investigation into the amount of CO2 released from wind-farm concrete elsewhere. |
| Visual objections to wind farms |
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Visual objections to wind farms"Beauty is in the eye of the beholder". So is ugliness. Some people like the look of a row of wind turbines slowly turning on the top of a ridge, others find them offensive. It is, of course, insupportable to claim that one group is right and the other wrong.Almost everyone, it seems, 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. How we perceive wind turbines visually depends in part on whether we believe that they are, in themselves, desirable and useful. Those who see turbines as a part of the answer to the greenhouse/climate change problem are more likely to consider them beautiful, those who think wind-generated electricity is over-rated or that either climate change is not happening or is not due to Man's activities are more likely to see turbines as intrusive and ugly. 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 |
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There is no need, either for safety or in law, for the lights to be so bright. |
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.
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 candella on tall wind turbines in Australia, the New Zealand authority holds that lights of 20 candella are acceptable at Tararua III wind farm, even near an airfield (Terry Teoh, Pacific Hydro, pers. com. Sept. 2008). In Denmark 10 candella lights are used, and in Germany there are vareous standards, but usually blinking 100 candella 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 airial acident, 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.
January 2009I have been informed that CASA is putting together a team to review and identify air navigation lighting on wind turbines. The team is expected to complete its review sometime after mid 2009, when the wind farm industry will be given opportunity to respond. We can only hope that better sense will prevail and the future recommendation will be for less bright lights.If you have an opinion on this subject, why not have your say on the blog, or better yet, contact CASA. |
Water requirement of wind farmsWind farm objectors have claimed that wind farms consume enormous amounts of water. This is quite false. During construction water will be required for making the concrete needed for the footings of the towers, and for things like damping-down the dirt while road-building, but these things need very small amounts of water relative to those used for mining coal or cooling coal-fired power stations. (Depending on the type of turbine-tower footing that is built, from 200 to 800 tonnes of concrete are needed for each tower, requiring something like 70 to 300kL of water.) (I have attempted to obtain actual water consumption figures from several people in the wind farm industry, but to no avail. March 2010.)In fact one of the greatest advantages of wind power is its very small water requirement; coal-fired and nuclear power stations need boiler water and huge quantities of cooling water; even some forms of solar power require water for cooling, wind farms need none. A typical coal or nuclear power station would use much more water in one day than would be needed to build a typical Australian wind farm. |
Do wind farms turn away tourists?The allegation that a wind farm will turn away tourists is one that is often used by wind farm opponents. So far as I have been able to find out, it is quite false. I could refer to information from the wind farm industry, but skeptics would rightly say that that could be biased. The links below are from sources that appear to be unbiased.The Scottish Government (2008/03/12) published research indicating "minimal impact on the growth of Scotland's tourism industry". 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". |
Wind farms and land valuesThere seems not to have been scientific studies of this in Australia (I'd be pleased to hear about any if I'm wrong), however overseas studies indicate no adverse effect of wind farms on land values.Concerning the land on which the turbines are built; turbines are usually on the tops of hills where the land is too steep to crop, so no cropping land is usually lost. Stock quickly get used to turbines and will happily graze right under them. The value of a property is dependent on its earning potential and having turbines on a property greatly increases earning potential. The licensing fee normally paid by turbine operators to land owners varies from at least $4000 per turbine per year up to $10 000 at (Dalby, Queensland) and possibly as high as $14 000. (See also elsewhere). So fairly obviously values of land having turbines on it are likely to increase. The Clean Energy Council provide a fact sheet on wind farms and land values. My own inquiries with people in the real estate business in the Mid North region of SA (Jan. 2009) indicate that the value of land with turbines on it has risen because of the increased earning potential, while there has been no significant change to the value of land near wind farms. |
Wind turbine litterThe Industrial Wind Action Group, an anti-wind power organisation, claims that "More than 100 broken windmills dot the landscape in California near Palm Springs".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 failed wind turbines do not become a blot on the Australian landscape. A comment I can make here is that the very large wind turbines that have been used in Australia will have a high scrap value and therefore it will probably be worth dismantling them rather than leaving them once they become unusable. |
Lack of transmission linesMost reasonably intelligent Australians would realise that wind power developments in Australia have taken place where there are reliable and relatively strong winds. Fewer people realise that wind farms are also built near high-capacity power lines; there are many areas that have top-class wind resources, but are not being seriously considered for wind farm development because of the lack of transmission lines.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. Governments build transmission lines for coal-fired power stations and mines, one wonders why they do not for sustainable wind power? (Yet another indication that Australian governments are not seriously 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. |
Do wind farms replace coal-generated electricity?A commonly heard objection to wind farm construction is worded something like "no coal-fired power station has ever been closed down because of wind farms". While the statement as it stands is probably true, there is another that is equally true, "every kilowatt-hour of electricity fed into the grid from a wind farm is a kilowatt-hour that does not need to be generated by a fossil fuel fired power station".
The main reason that coal fired power stations stay in service in addition to new wind farms is that the power consumption in Australia continuously increases. Consider, for example, how popular big plasma TV sets are; they can consume as much power as a refrigerator. Wind farms have not replaced coal-fired power stations, but they may have avoided the necessity of building new ones and they have allowed coal-fired power stations to work at lower rates of production than they would otherwise have done. 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. |
How much electricity do wind farms generate?
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. The graph at the right, from South Australia's Electricity Supply Industry Planning Council, shows that just over 10% of SA's electricity came from wind farms in 2007/08. Note also on the graph that while wind energy is still a small part of total SA electricity it is by far the fastest growing component. 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 50MW would be only moderate in size, even if the average household consumption is 1kW we can calculate that this moderate-sized wind farm would generate enough electricity to supply more than 17 000 homes. Finally, it must be remembered that each megawatt-hour of electricity generated by a wind farm means that one less megawatt-hour need be generated by a fossil-fueled power station. |
In what range of wind speeds do turbines operate?I have heard it said that most of the time the wind is either too weak to run a turbine or it is so strong that the turbine has to be shut down. The fact is that the capacity factor for most Australian wind turbines is at least 30%. This indicates that they generate around 30% 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 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. |
LinksOther recommended sources of information...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. The Danish Wind Industry Association has an excellent Guided tour of wind power; this is by far the most detailed explanation of all aspects of wind power that I know of. Wikipedia has an extensive page on the Environmental effects of wind power. |
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IndexOn this page...Aboriginal sites Air navigation lights Are wind turbines noisy? Barriers to animal movement Bats killed by wind turbines Bird deaths from 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? Distance between turbines and houses Do turbines frighten stock? Does wind replace coal? Efficiency of wind turbines Electricity generated must be consumed Energy consumed in wind farm construction Erosion of sites Factors, wind vs solar Fee to landowner for wind turbine Fire hazard Fragmentation of bird habitat General environmental concerns Health effects Health effects relating to noise High temperature shut down How much electricity do wind farms generate? Infrasound: low frequency noise Introduction Is solar better than wind? Lack of consultation? Lack of support for local community? Lack of transmission lines Leakage of oil Links Links: Wind farms and weather Native vegetation Paucity of information from operators Power curve of a wind turbine Power surges Pygmy bluetongue lizards Relative efficiency of turbine - graph Relative efficiency of turbine - table Research by Nina Pirpont Roads on wind farms Site damage Social conflict Solar complements wind Specific wind power problems Top Turbulance from wind turbines Visual objections Water requirement Weather - turbines and surface roughness Weather radar interference Wind farm effect on tourism Wind farms and land values Wind is intermittent Wind power generation in one month Wind power not the answer Wind power problems Wind speed range of turbines Wind turbine litter Wind turbines and TV reception Wind turbines are short-term? |