Wind Turbine Generators example essay topic

Introduction. Harnessing the natural power of the wind is by no means a new concept. Asides from sailing, wind power has been utilised for many thousands of years, principally for agricultural purposes. Basic windmills are thought to have been used in Persia (now Iran) as early as the 7th century AD. Their ability to make use of otherwise untapped energy sources without the needs and costs of other alternatives, ensured that they remained the machines of preference in several industries throughout both agricultural and industrial revolutions. Whilst their basic concepts have remained true to the basic origins, technological advances have enabled engineers to adapt the mechanics of the mill to enable a more functional and useable source of power.

In the 18th C, engineers developed spring sails (a device incorporating shutters onto the sails) to enable the mill to be run at constant speed during variable wind speeds automatically. The development of the fantail in 1745 also ensured the mills ran in the face of the wind and along with air brakes meant that the mill could run at its most efficient at all times without the risk of doing itself damage in strong winds. Uses developed into water pumping, wood sawing, paper making, pressing oil seeds and a variety of grinding uses. The use of wind turbines for generating electricity was pioneered in Denmark late in the 1890's. The concept was made a reality by Poul la Cour (1846-1908) who had originally trained as a meteorologist. He built the world's first electricity generating wind turbine in 1891 and although his project was a success, decided the greatest problem lay in storage of the electricity.

As a result he used the electricity from his turbines for electrolysis in order to produce hydrogen for the gas lighting in his school.! Stone basic drawback of this scheme was the fact that he had to replace the windows of several school buildings numerous times, as the hydrogen exploded due to small amounts of oxygen in the gas (! )!" DWTMA. As technological barriers were worked through, wind turbines became increasingly complicated. One of the greatest developments was the use of aero foils instead of angled blades. Aero foils have the benefit of using lift to turn the blades in the same manner as an aircraft's wing rises on an air current.

This type of blade replaced the older type, which relied upon drag, to literally push the blades around at a much less efficient rate. Whilst most common type is the horizontal axis wind turbine (HAWT), the alternative is the vertical axis machine such as the Darrieus machine. This second type of machine is far less common due to its size, appearance, costs and noise levels. The result of the thousands of years worth of innovation and development has led to the current style of machines available on the market. The most powerful machines at the moment are multi-megawatt horizontal axis machines with 72 m rotor diameters, mounted on 60 m towers.

Whilst these machines are still prototypes under review, the potential for their expanded use in the future still remains a strong possibility (although for machines of this size their siting will usually be off-shore). The most common type of modern turbine however, is the basic 500-1500 KW horizontal axis machine. The science. The wind turbine generators consist of several components. The blades are fitted to a central hub, which is connected to a gearbox via a low speed shaft turning between 19 and 30 RPM. The gearbox increases the rotational speed to approximately 1500 RPM, which is a more acceptable speed for the asynchronous generator to run at its optimum level.

With the gearbox and generator running for long periods, wear and hence increased noise would cause a nuisance. To tackle this problem, self-cooling and lubricating mechanisms are built into the turbines main housing (called the nacelle). Also incorporated into the nacelle are yaw mechanisms, to ensure the blades are always facing into the direction of the wind, and anemometers to ensure the turbines do not run in too weak winds (excessive noise which is not so easily carried away on the breeze) and not in too strong winds (can over-stress some of the components- dangerous when a broken fibre-glass blade can be flung up to 850 m. (OECD 1988) ). Siting Requirements. At heights of about 1 km, the wind speeds are hardly influenced by the surface of the earth at all.

In the lower layers of the atmosphere, however, the friction against the surface of the earth slows wind speeds. The roughness of the earth's surface can have a dramatic effect on the power gains available to wind farms. For example, wind farms located near or within! yen roughened areas! | such as forests and built up areas will produce significantly less output than those sited on open land with few or no obstacles. It is for this reason that wind farms tend to be located in the! yen unspoiled! | countryside and hence the cause of frequent outcry. As a general rule of thumb, it has been proven that sites which have a prominent view of the surrounding landscape will be the most favorable and this is especially true of hill top sites which can benefit from the so called! yen speed up effect! | which they possess.

An important point to raise in the context of wind slowing condition is that the roughness factor of water is 0, which means it is accepted as having negligible detrimental effects. In light of this fact, it is clear that the siting of wind farms either on the coastlines or out to sea would be beneficial. So what are the arguments? The UK has 40% of Europe's wind resource and at present only uses 0.5 percent of this. This figure lags far behind countries such as Germany and Denmark. With the benefit of having the pioneers of wind energy being native, Denmark is at the cutting edge of wind power technology and as a result, has numerous wind farms in operation generating 1442 MW of power (!

|98 figures). As such Denmark has a relatively large proportion of it's population living in proximity to the sites. One of the most common arguments, commonly echoed by the Commission for the Protection of Rural Wales, is that the siting of single turbines or farms is an eyesore and that the! SS protection of Wales! | greatest asset outweighs the few benefits of a misapplication of a fundamentally sound concept!" . (M. Williams, CPR W 1997) It has been frequently pointed out in surveys such as those by Holdningsunders " pg else, 1993, that! SS people with no specific experiences with wind power believe that noise is louder than those who actually live besides turbines.

!" This is repeated by a Friends of the Earth inquiry in 1991 where a public attitude survey conducted on behalf of the Department of Energy showed that those who already have some experience of wind turbines in their locality are overwhelmingly convinced that the countryside is a suitable place for wind turbines. They even confirmed they believed that! SS they are an efficient use of rural land!" . It has also been proven that men are more critical of wind turbines than women and the situation is the same for middle-aged people as opposed to the young or the old. A paper by Wol sink and Springers in 1993 came to the conclusion that! SS the level of noise annoyance is hardly related to the actual sound level of specific turbines!" .

A site specific study was conducted in Sydthy in Denmark in 1997 by Andersen et al. Sydthy has 12,000 inhabitants and at present 98% of their total power supply comes from local wind farm co-operates. People's attitudes towards the farms tend to reflect that a higher degree of experience of the turbines leads to greater tolerance of the structures. Indeed, in Sydthy, those living less than 500 m from a turbine tended to be more positive about the influence on their lives. Despite the claims from many! yen green! | organizations and manufacturers, many people still do not want further sites to be constructed, especially here in Britain. Whilst surveys and polls depict a nation of environmentally concerned people, there is still a great majority who are only in favour of renewable energy sources in principle.

Renewable energy, and in particular wind power attracts the NIMBY syndrome (Give, 1995) from communities. NIMBY ism is not a special feature of wind power. It can be found in many other situations such as motorways, roads, bridges, tunnels, nuclear power stations and even hospitals and schools. Throughout the many before and after surveys recording the changing public opinions, the patterns remain clear that a majority of people favour the developments, although even the green lobbyists realise that many will never accept the visual intrusion element. Indeed, the results highlight the fact that! SSthere are some hidden variables other than the NIMBY effect in itself, that determine public attitude towards wind power at the local level!" . (S. Damm borg 1997) A lack of public participation in recent developments has given rise to the opinion that many of the newer sites have been developed through a commercial desire to achieve financial benefits at the cost of the local residents.

In a recent study in Friesland, 49% said they would definitely go to public meetings if such meetings were arranged and advertised, although it is unlikely they would feel so inclined if they believed their presence could have no effect on the development. To achieve acceptable levels of acceptance in the community, developers need to instill a feeling of self-autonomy within those who are likely to be affected most. Where the local community is listened to and worked with, the levels of acceptance can be dramatically improved. In some cases, especially where the local residents gain from the projects themselves, residents display a sense of pride over! yen their! | turbines. To achieve some meaningful levels of renewable energy in our national power supply, the government introduced the Non-Fossil Fuels Obligation (NFFO). Effectively, this regulation ensured that all surplus energy, produced by sustainable means, would have to be bought up by the Regional Electricity Company in jurisdiction.

The extra costs incurred are then reimbursed from the fossil-fuel levy funds. Even though the RECs are under obligation to purchase the energy, renewable energy providers may still find it difficult to remain economically viable as they are often charged for a! yen Distribution Use of System! |. This DUoS charge covers the use of the electrical grid to transformers, sub-stations and all the cabling between. Renewable energy suppliers believe these costs to be exaggerated and unnecessary, and have recently asked the government to review these practices. The claimed associated problems.

Aside from the visual intrusion of the turbines themselves, the impact of national grid extensions and pylons also have to be addressed. Pylons themselves do not require a large plot size; however, even a small area in the middle of a field can prove inconvenient for farming purposes. They also carry with them the same negative effects of visual intrusion as the turbines although pylons themselves are more readily accepted due to their common place on the existing landscape. Pylons, power sub-stations, fences surrounding the base of turbines and the blades themselves are also blamed for unnecessary bird deaths. The British Wind Energy Association (BWEA) and the OECD have studied the effects of wind farms on local bird mortality in extensive detail. Danish investigations at Tjaereborg have used radar studies to investigate the impact on low-flying birds.

The results have shown that despite the 60 metre rotor diameter, birds adapt to the installations very quickly and tend to change their flight route some 100-200 m before the turbine and pass by at a safe altitude. Some falcons have even been known find the nacelles good for nesting upon! According to supporters of wind power developments, the only major problem with bird fatalities has been in California, where in the late 1980's a park of colossal proportions was set up. In Altamont Pass over 1000 turbines were erected to form a! SSwind wall!" which literally closed off the pass.! SSThere, a few bird kills from collisions have been reported!" , is the official stance.

In a more objective review of the subject, the Scottish Natural Heritage produced a 68 page critique. The conclusions drawn from it's research point to the misleading representation of other investigations and warn of the need to compare! yen like with like! |. Most similar studies have suffered from a lack of adequate control or baseline data.

At Uk (a wind farm on the Dutch coast) recorded levels in bird activity were noted, although this may have been due more to construction and increased human disturbance than a direct effect of the turbines themselves.! SSA study from the Danish Ministry of the Environment says that power lines, including power lines leading to wind farms, are a much greater danger to birds than the wind turbines themselves!" (DWTMA, 1997). The primary concern of the authors is the thoughtful siting of proposed wind farms. They feel that with sufficient research into migratory patterns, critical habitats and topographical features, the impact on the environment can be vastly reduced. Just as important an element, is to remember that each site needs its own individual environmental assessment, as no two sites are identical. The metal blades, which used to be used on smaller and less powerful machines, attracted some concern from local residents.

The metal rotors were found to! SS reflect radio waves in a manner that interferes with radio and TV reception!" (OECD 1988). The repositioning of slave transmitters out of the line of sight of rotors was an expensive extra cost, although modern preferences tend to use steel and aluminium much less because of weight and metal fatigue respectively. Modern techniques use epoxy composites such as GRP, wood-fibre-epoxy and even Kevlar composites.

These materials are less prone to damage and wear and so tend to last much longer and become more economically viable as well as eliminating electro-magnetic interference. So why not build out to sea? The national planning policy guidance relating to the development and siting of wind farms, is set out in PPG 22 (1994). The document suggests that! SS noise and visual intrusion, especially in areas of particularly attractive countryside, I's etc, should be an important planning consideration.

!" Whilst the technology has moved on in leaps and bounds in terms of noise pollution, the visual intrusion element is still of prime importance. As pointed out by Mervyn Williams, the director of the campaign for the protection of rural Wales, ! SSWind turbines contribute little in terms of electricity production!" . Twenty years ago the power output of! yen normal! | turbines was rarely above the 50 K watt mark.

To take significant electrical power from this energy would have required huge numbers of these machines. Instead they tended to be used for personal or local uses outside of the national grid. Modern technology has evolved these machines into state of the art devices capable of delivering up to 2 M watts each (currently under development for off shore use). Taking the position that wind power does not generate enough electricity to necessitate its use, seems a little dated. Indeed, whilst these monstrous machines may seem out of place adorning the rolling hills of Wales, the possibility of placing them between 10 and 25 miles off the coast seems almost too good to be true. Offshore, where the winds are much faster.

The benefit of faster wind speeds is that the energy contained in the wind varies with the cube of the speed. Hence for a speed twice as fast, 2"d = 2"a 2"a 2 = 8 times the power, and since the sea has a low roughness factor, the speeds are constantly higher than those on land. Due to these higher speeds and the lack of any local people, noise pollution is less of a concern, so the machines are allowed to run at a higher (more noisy) speed, which is far more efficient. Since they are never built within shipping channels, and the fact that any ship which needs good warning of obstacles to turn, have radar these days, it is common practice to paint the turbines in a NATO marine camouflage paint to reduce any visual intrusion.

It is said that even in the lightest fog, the turbines all but disappear from sight. In the UK, two 750 Kw machines were installed last summer in 5 m deep waters as an extension to the five harbour wall turbines at Blyth in Northumbria. The project was part funded by the EU and take advantage of the current NFFO policies in place. At present planning permission still tends to be the main factor in holding up such developments in the UK, although according to UK Power 99, an independent overview publication of the power industry, the DTI is working to simplify the process by creating a!

SS standardised lease agreement with the Crown Estate for the use of the seabed!" . Traditionally, the main factors that prevented the widespread use of offshore developments were the cost of foundations and cabling. Until recent surveys in 1997 the preferred choice of material for foundations was concrete. The surveys found that steel was a far more cost-effective material and was well up to the task. Despite common belief that steel would corrode too quickly, by Cathodic (electrical) protection the structures can be assured to remain stable for over 50 years (the working life for turbine components being 20 years). This would mean the foundations could support at least two generations to off set its initial costs.

Cabling also used to be a prohibitive factor. But adapting oil rig technology has enabled the cheaper method of washing to be used to lay the cables. High pressure jets simply wash channels into the seabed for the cables to run along. With reduced costs and increased benefits coming from off shore developments, off shore wind energy has the potential to make a significant contribution to targets for renewable energy in the UK. Indeed to achieve levels of 10% of the UK's energy supply from renewable sources by 2010 (as proposed in Regional target levels in PPG 11), there will have to be a significant effort made as, at current levels that figure is still a long way off. The sales pitch offered by the DWTMA encourages an economical, renewable and future friendly concept.

This may be true, and according to official government figures, up to 6500 new jobs could be created if the government's targets were attained. These jobs being in manufacture, servicing and installation. But with no large scale turbine manufacturers in the UK it is hard to see where these jobs would come from year round. Final comment. But however willing the government may be to promote renewable energy sources in the UK, public opinion still remains a large factor in the reality of it's future. This point is best illustrated in the Friends of the Earth publication! yenEarthmatters! | in the most recent editions.

An article in issue 40 evoked a response from one reader who states that he believes! SS the greatest immediate threat to the British countryside is not air pollution, road building or house building, but wind power! K! K. to produce meaningful amounts of energy, tens of thousands of turbines would have to be sited on relatively unspoilt uplands and coastal areas of western Britain!" . He tops off his argument by concluding that! SSwind farms are visual pollution, and this cost is greater than any environmental benefits!" . The author of this letter, was from London, who, being an urbanite, stereotypically has the most!

SS romantic view of the countryside!" , with! SS little or scant knowledge of a working countryside!" . Needless to say, both the FOE and other readers commented on this letter but it goes to show how the! SS personal whimsy of a small, vocal minority who claim to be speaking in the interest of the environment!" can still evoke a significant conflict.

Bibliography

Danish Wind Turbine Manufacturers Association web site web of the Environment, Transport and the Regions, web of Trade and Industry (DTI) - and c. f. DTI website, web Impacts of Renewable Energy, The OECD compass project, OECD Paris 1988 Earth matters, Friends of the Earth member's magazine Issues 40-43, FOE 1999, web without end, Michael Flood, Friends of the Earth, London 1991 Green Futures, Magazine of Forum for the Future, Issues 6 1997- issue 11 1998, London Johnston, Bryan, 'Landscape effects leave wind power up in the air,' Planning 1084, 2.
9. 94. Milne, Roger, 'Renewables feel the draught,' Planning no. 1095, 18.11. 94. Microsoft Encarta 1996 Encyclopaedia, web David, 'Renewable energy and rural development,' Town and Country Planning, March 1993.
Review of the impacts of wind farms and other aerial structures upon birds, J Paul Gill, Mike Townley & Greg P Mudge, Scottish National Heritage Review no. 21, Perth UK, 1996 UK Power 99, McMillan- Scott PLC Publications, Cheshire December 1998 Wood, Peter & Wade-Smith, Richard, 'Welsh decision sets the wind farm scene', Planning 939, October! yen 91.
Wind Energy Conservation- from theory to practice- Proceedings of the 19th BWEA Conference (16-18 July! |97), Edited by Ray Hunter, The British Wind Energy Association, Mechanical Engineering publications Ltd, London 1997 Wind Energy- Power for a sustainable future, British Wind Energy Association, London 1997, web.