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More recent posts about wind turbines The wind turbine debate - 2011Tim Padfield, 22 December 2011 The noise workshop, November 2011Here is a summary of the noise report, from Infinergy. Tim Padfield, 22 December 2011 The Helium BalloonOur energetically campaigning neighbour, Ian Phillips, has collected a petition to have a helium balloon tethered at the wind turbine site to give an impression of the height of the towers. The director of Tresoc, Ian Bright has "retorted angrily", according to Ian's letter to the Totnes Times (Wednesday, 21 December 2011). I try here to bring some objective science to calm this dispute. The distance between the tip of the proposed turbine tower and the public right of way near Luscombe cross is close to the limit for human range finding by binocular vision, which depends on the light intensity and the age of the observer but is generally put at 500 - 600 m. Beyond that, the brain has to use other ways to judge distance. In this particular case the only available mechanism is to use the remembered size of the suspended object when it was viewed close enough for binocular vision to give a good impression of its size. Alternatively, one could use an object of familiar size, for example the director of Tresoc hoisted aloft in a wicker basket. However one chooses to improve judgement of distance at a distance, a balloon on a tether is a poor imitation of a tall column with rotating blades at the top. A defect of the recent display of predictive pictures at the village hall was that the position of the observer's eyeball was not defined, by a hole in a screen or by a chalk line on the floor. The perspective impression from a flat picture depends on the distance to the observer. A good way to fix this is to make a diorama in a box with a small hole, so the observer can only use one eye, at a defined distance from the scene. Binocular vision is thus suppressed and the diorama gives an impressively realistic impression. This was a popular Victorian entertainment, sadly fallen out of fashion. The best we can do without carpentry is to print the picture from the totnescommunitywindfarm website, take it to Luscombe Cross, close one eye and fiddle the paper around until the actual scenery matches that on the image. The turbines will then appear as a reasonably accurate impression. This exercise is less festive than the proposed balloon, but consider that helium is one of the scarcest of our natural resources, and difficult to recycle because it escapes from the earth's atmosphere into space. Tim Padfield writes, 2 December 2011: The Totnes Times for 30 November 2011 has two letters arguing against the Luscombe Cross wind farm. I try to keep a neutral view on this matter until all the evidence and predictions are available. Meanwhile, the misinformation spread by opponents of the wind farm offends my sense of fairness and honesty in debate. John Cetti writes: "I have never seen any figures published about the actual percentage of wind power generation over a period against the theoretical, for a good reason. The results are so bad that it would kill further installations..." Mr Cetti has skimped on his research as well as assuming a result which he cannot find. There is abundant information about the output of wind turbines, which achieve about 30% of their rated power, averaged over a long period. See Just about every statement in Mr. Cetti's letter is an assertion without evidence. The claim that nuclear power stations have to run at full power in parallel with wind turbines is an ancient myth which doesn't get more convincing with repetition. The load on the UK electricity grid roughly doubles from around 30 GW at night to 55 GW at peak demand around 18:00. http://www.mpoweruk.com/electricity_demand.htm It is dispiriting that such baseless and divisive rhetoric is published by a local newspaper. The other letter, by Richard Shepherd, is more interesting. He questions the designation of the wind farm as a Community project, pointing out that the likely actual shareholding by TRESOC is undefined; only the maximum 49% is quoted in the company literature. Both TRESOC and Infinergy have been reticent about benefit to the community, as distinct from benefit to local shareholders in the companies. There is an honorable tradition of wind farm operators making voluntary contributions to benefit the whole community where their turbines are planted. Let us hope for clarity and generosity in TRESOC's news releases as the project progresses. 22 Nov 2011 A comment has been removed by the editor because it was anonymous. In view of the adversarial development of this debate the editor now requires both the name and address to be given. If you don't want your address revealed you can email it to the editor, or send your contribution to be posted by the editor. Luscombe cross wind farm noise assessmentA report by Tim Padfield on the noise assessment workshop at Harbertonford village hall, 19 November 2011, 10:30 to 13:00 The noise assessment was reported by Andy McKenzie and Sylvia Broneske from the acoustic company Hayes McKenzie (http://www.hayesmckenzie.co.uk). Andy introduced the units of sound measurement, with the aid of two loudspeakers calibrated to give exact decibel values of typical wind turbine noise. He went on to explain the various adjusted decibel values for noise of which the most relevant to the discussion is dBLA90. This is the noise, weighted according to the frequency sensitivity of the ear (that is the 'A' bit) which is exceeded 90% of the time. The 90 subscript means that the measurement excludes the intermittent noise from passing cars, aeroplanes and strimmers and gives a value for the background noise during the quietest 10% of the measuring period. The background noise increases in windy weather, so the background level is measured at various wind speeds to give a graph of background noise against wind speed. The background noise is also separated into day and night values. At this point, Andy introduced the industry guideline for acceptable noise, designated ETSU-R-97. This provoked remarks from the floor about alleged defects in this method. However, right or wrong, it is the guideline that is used by local authority planning officers to define the noise limits within which the wind farm must operate. Though not itself a 'legal' standard, it is used to make legally binding restrictions on wind farm operations. This guideline advises a limit within the range 35 - 40 dB (43 dB at night) in quiet conditions but in windy weather the turbine noise is permitted to rise as the background noise rises but may never exceed 5 dB above the background. This is why the measurement of background noise must be done before installation of the turbines. Its value is archived and can be compared with the actual noise after installation of the turbines, to ensure that they comply with the planning conditions. After this introduction to the principles behind the measurements, Sylvia took over to describe the actual measurements around the proposed turbine site. A map of the region is first overlaid by sound contours derived from the turbine manufacturer's specification. These contours are smooth and take no account of the local topography, assuming an entirely flat landscape. The houses closest to the turbine site are identified and they are chosen for background noise measurement. Four sites were chosen. Measurements were made over 18 days in September 2011. There were queries from the floor over the siting of the measuring device at Brockhills, which is on the busy A381 road. However, the dBLA90 measurement should exclude local traffic noise, and will certainly do so at night. There was a query about the site at Dundridge Gardens, since the background noise was being measured in a quiet place in a valley instead of on a nearby unsheltered location. However, this actually gives better noise protection, since it gives a lower background which the turbines may only exceed by 5 dB. The graphs of actual background noise and predicted turbine noise were presented for all the measuring sites. Predicted noise levels were within the guidelines at all properties. When the report is released for general viewing the quite complicated graphs will be available for detailed study. There were statements from the floor citing turbine noise recorded in youtube videos. To give a measured example of turbine noise Andy set the loudspeakers to produce 40 dB of typical wind turbine noise in the third row of the audience, which was given a hand held sensor to check the value. The turbine noise was certainly audible, for the few moments when the audience was quiet, and gave a good impression of the maximum noise permitted to be heard at nearby houses. The matter of the swishing noise at three times the rotation speed, commonly called AM noise (amplitude modulation), was raised. Andy explained that this was under investigation by acousticians but its precise cause or effect is not yet understood. The chosen design with the rotor raised high above the ground will minimise this phenomenon, because it is at least partly due to varying wind velocity at different heights within the disc of air carved by the blades. The continuity of the acousticians' presentation was spoiled by repeated interruptions. It will surely help in future if we have an independent chairperson to control proceedings. It is understandable that strong emotions and fears are aroused by this major project but a presentation of guidelines and measurements which are designed to protect us against turbine noise should be heard with courtesy, whatever opinion one may have about this particular proposal. Tim Padfield, 20 November 2011 Ian Phillips writes, 13 November 2011 STOP THE LUSCOMBE CROSS WIND TURBINES - PUBLIC MEETING The public meeting on 7th Nov. at Harbertonford village hall drew over 50 people, chaired by Ian Phillips. Guest speakers John O’Sullivan and Hans Schreuder explained how wind energy relies on the almost 100% continuation of existing methods of power generation, owing to its extreme variability. Recent research in Holland shows that, far from reducing the “carbon footprint”, wind turbines actually increase it. A clip was shown of the film “Pandora’s Pinwheels” (via the internet) about families in OZ and NZ, living up to 3 miles from wind turbines, driven out of their homes by low frequency noise, and with experts discussing the health threat. The same fate has befallen some families in Britain. Harberton and Harbertonford lie within approx. a one and a half mile radius of the proposed turbines, and these are not “farms” but “wind power stations”. As industrial plant, they should be subject to the British Standard BS4142 and not the existing guideline, ETSU-R-97, which was drawn up by the wind industry themselves, and described by the Department of Trade and Industry as “not fit for purpose”. A golden rule is that if you can see the blades, you may hear the sound of them, and most of Totnes lies well within a three mile radius. They challenged the belief that we need wind energy because the carbon dioxide from fossil fuel use is causing a runaway overheating of the planet. They showed, via numerous charts/graphs and quotes, that temperature changes over the last century have been very small, and that there is no warming this century. Further, satellite produced data on the amount of polar ice cover shows no overall trend over several decades. And the polar bear population has, in fact, increased greatly since the 1960s. A petition is underway to ask the developers and landowner to erect a helium balloon on the site, as this is the only way to demonstrate the reality of the 325ft height of these proposed structures. For those who would like to be kept in touch with the debate, who are concerned about the Wind Power Station proposal, the following link has the power point presentation used at the public meeting on Nov.7th and will be updated regularly. www.tech-know.eu/Harbertonford Ian Phillips, The Melbray, Moreleigh Road, Harbertonford, Tel 01803-731008 From Tim Padfield 9 November 2011 The debate about the proposed Luscombe Cross wind turbinesOn 7 November, Ian Phillips and friends brought into Harbertonford village hall two heavy guns of the global warming war, John O'Sullivan and Hans Shreuder. Although the meeting was announced as 'Stop the Luscombe wind turbines' the speakers concentrated on criticising the predictions of global warming. O'Sullivan was the first main speaker. He made abundant use of the rhetorical trick of repeating "Don't trust me - check the source data". Except that the source reference was not always given, as when he twice asserted that "if you can see a windmill, you can hear it". Since the proposed turbines will be visible from Dartmoor, will they scare the ponies? Another trick of presentation was to insinuate that noise from wind turbines is a major nuisance, by describing at great length the conflicting industrial noise standards. However, there were no measurements given for the actual noise from turbines in a similar situation to those proposed. So there was no way to judge if the actual noise will be well below any of the limits set by any of the inconsistent standards. The entirely irrelevant matter of the low toxicity of carbon dioxide to humans was presented as a reason not to fear the rise of this gas in atmospheric concentration. A graph of the difference between wholesale and retail electricity prices was presented as fact, but the difference was then insinuated to be caused by the subsidy to green energy, without evidence. The toxic waste from neodymium production for turbine magnets was emphasised. However, this metal is used in countless products from jewellery hasps to earphones. We can share outrage against the evils of industrial pollution, but we are all in countless small ways complicit in the ugly byproducts of global industrial capitalism. This won't change because we stop the erection of two wind turbines. Hans Schreuder followed with a rapid fire of factoids of apparent profundity, too specialised for critical evaluation by an audience far removed in time from their A-level physics studies. He poured wide ranging scorn on false theories of the early 20th century physicists, and of modern physicists, but his examples of errors were either irrelevant or wrong. His repudiation of a commonly encountered explanation of the greenhouse effect in a glazed box is no embarrassment for atmospheric scientists because the atmospheric greenhouse effect rests on the entirely different physics of the convective rise and cooling of air. He contested the accepted approximation that the earth without atmosphere would radiate from each square metre at one quarter of the intensity of the incoming solar radiation flux, pointing out that the sun illuminates half the earth at a time, so the proper intensity ratio is a half rather than a quarter. This ignores the glancing angle of incidence of the sun's rays towards the edge of the illuminated hemisphere, which reduces the energy absorbed per square metre of the earth's surface, while not affecting in the same way the outgoing radiation from the earth. Such an elementary error, unrelated to global warming, casts much doubt on the validity of his quickfire sequence of assertions that everyone else is wrong, not just about global warming, but about physical principles first asserted by Planck, Boltzmann and Einstein in the early 20th century and found in countless experiments to give good agreement with measurements. Turning to turbine technology, Hans released a comical sneer at wind turbine electricity for being uncouth, because it has to be converted and phase synchronised with the elegantly smooth sine voltage of the national grid. The audience was encouraged to believe that wind turbine electrons are deformed cripples compared with electrons put into the grid from other sources. These presentations from the podium gave this reviewer a powerful impression of manipulation overriding reasoned argument; too clever to resort to outright lies but rich with over-emphasis on emotive irrelevances and repetitive reference to noise. There was almost no material presented of direct relevance to this project, the presentations were largely concentrated on trashing global warming, with the implied consequence that wind turbines would not be considered a viable energy source without the subsidies released by global warming concerns. At question time, the meeting was brought back to the explicit subject under discussion by Jackie Clayton, who asked what alternative there is for people who feel a moral duty to accept the consequences of a rich lifestyle, which means sharing the burden of producing the electricity that powers it. The response from Ian Phillips was nuclear fusion or thorium fission. These are both distant dreams. At a more immediately practical level, this reviewer points out that the two turbines under discussion will send around one and a half megawatt of power on average into the local grid. Locally generated electricity reduces transmission losses in the grid, which in return fills in the gaps when the wind fails. The productivity of these two pylons will be surprisingly large, compared with the output of the largest existing hydro-electric power station on the Harbourne, which has a maximum output power of 17 kW but averages about 5kW, gathered from a catchment area larger than this parish. Fuel crops produce around 5kW per hectare. A house roof solar voltaic array will generate an average 0.5 kW. The revenue from the two turbines will be approximately a million pounds a year, and they will create power locally and cleanly. They have merit as sustainable energy generators regardless of the dispute over global warming. Their potential contribution to our wealth, with small side effects, merits serious, informed discussion rather than bombastic claims and counter-claims designed to appeal to emotion rather than reason. Tim Padfield An explanation of the grid connection of the two wind turbines proposed for Luscombe Cross21 September 2011 Extracted by Tim Padfield from an email from Tony Berndes, Primary System Design Manager, Western Power Distribution Electricity will flow from a generator towards the load (demand) through the path of least resistance. Harberton appears to be located in the region of two of WPD's 33kV lines, the source of both of these lines is our 132/33kV substation near Totnes. One line supplies the demand in the Salcombe area and the other the Kingsbridge area. In simple terms, if a generator of around 5MW was to connect on to one of these 33kV lines, the energy would generally tend to flow towards the demand (ie Salcombe or Kingsbridge). However, it is possible that under times of lower demand and higher generation output (ie when the generation is greater than the demand for electricity at Salcombe/Kingsbridge), then some of this energy would flow back to the source substation at Totnes, and may therefore then go towards Totnes town. I should add that it may be possible that a generator of this size may seek to connect to our 11kV network, and if this were the case (and electrically technically acceptable) then the electricity would flow to the local loads/demand on that 11kV network, working it's way back to the 33/11kV substation that it is connected to. Mandy Burton, TRESOC Administration responds (14 September 2011) Dear Mr Padfield, Many thanks for your email. I have forwarded it to our Directors, one of whom will respond to the points you raise shortly. In the meantime, I have included in this email below an explanation from Infinergy, our technology partner on the wind farm project, of how we reached the figure for the number of households we expect the turbines to serve. We use 'up to' normally to show what our calculations for turbine output give us but since that varies year on year, we like to be cautious and say that they can provide for that number of households or a bit less should it be a poorer wind year. In terms of Totnes Community Wind Farm, we might have been too conservative actually. I'll give you our calculation so you see what i mean: A typical modern wind turbine works 70-80% of the year, generating variable outputs each day depending on the wind speed of that day. In a year, the turbines at the Totnes Community Wind Farm site are expected to reach about 29% of their installed capacity of 2.3 megawatts. This is called the capacity factor or load factor and is a common way of calculating any generator’s output; as an example, for coal fired plants it’s around 50-60%. Electricity production (turbine output) is calculated in megawatthours. So what we do is, we look at the capacity of the turbine (2.3MW), the fact that we expect it to make 29% and multiply that by the number of hours in the year, which is 8760. The outcome is 5,843MWh per year. The average annual electricity consumption of a UK household is 4.39MWh (Source: Digest of United Kingdom Energy Statistics 2009, Table 5a). Dividing the turbine output over the household consumption brings us to 1330 homes per year. We are proposing 2 turbines, so that is 2660 households. We rounded this figure down to a more convenient figure of 2500. An open letter to TRESOCfrom Tim Padfield I have had a flyer inviting subscriptions to TRESOC pushed through my letter box in Harbertonford. In it you quote Jonathan Porritt "It falls to organisations like TRESOC to put the record straight..." So why do you persist in writing misleading claims that the windmills "will provide for the energy needs of up to 2500 homes in Totnes via a power line running straight from the site into the town."? Firstly 'up to 2500' could be anything from one to 2500 - a popular way to provide the illusion of a large number without risking criticism for being over optimistic. I think you mean 'about 2500'. Secondly, the wind turbines will feed into the adjacent national grid line, which runs between Totnes and Kingsbridge. It is true that distributed generating power reduces the electricity transmitted through the grid, but when the wind fails, electricity generated by Norwegian hydro-electric generators, and French nuclear power stations, and Spanish solar arrays, fills the gap so the natives of Totnes do not lose power to their hair dryers and wide screen televisions. This farsighted initiative from the 1930s emphasises the value of sharing, exactly the opposite to your complacent assertion that the juice flows only into Totnes. It would be possible to pipe electricity directly to 2500 homes through an independent network, leaking the occasional surplus into the grid and earning some money from it, but I don't think that is what TRESOC plans to do. So please make your brochure scientifically accurate, in the spirit of Jonathan Porritt's remark. The 2.3 MW figure presumably describes the optimum power output in a stiff breeze. More relevant is the likely kWh per year, because this is what predicts the revenue and the usefulness of the installation. You must be aware that there is considerable opposition to the wind turbines in Harberton, Dundridge and Harbertonford, which are the closest communities to the site and which, according to your brochure, can only watch with dismay as the electricity slides away down the hill into Totnes. That is not good diplomacy. I suggest that you write an accurate description: that the turbines will feed xx MWh per year of energy into the national grid, which would typically supply xxx households. The TRESOC shareholders will get a portion of the revenue from the very generous feed-in tariff and a nice warm glow from feeling that they are benefiting the environment everywhere. Tim Padfield, 14 September 2011 |