Wind Power - Energy For A Sustainable Future

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 airbrakes 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, papermaking, pressing oil seeds and a variety of grinding uses.

The use of wind turbines for generating electricity was pioneered in Denmark late in the 1890s. 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.

ÐŽ§One 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 (!)ЎЁ DWTMA.

As technological barriers were worked through, wind turbines became increasingly complicated. One of the greatest developments was the use of aerofoils instead of angled blades. Aerofoils have the benefit of using lift to turn the blades in the same manner as an aircraftÐŽ¦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 72m rotor diameters, mounted on 60m 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 500-1500KW 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 850m. (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 earthÐŽ¦s surface can have a dramatic effect on the power gains available to wind farms. For example, wind farms located near or within ЎҐroughened areasÐŽ¦ 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 ЎҐunspoiledÐŽ¦ 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 ЎҐspeed up effectÐŽ¦ 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 EuropeÐŽ¦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 (ÐŽ¦98 figures). As such Denmark has a relatively large proportion of itÐŽ¦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 ÐŽ§protection of WalesÐŽ¦ greatest asset outweighs the few benefits of a misapplication of a fundamentally sound conceptЎЁ. (M. Williams, CPRW 1997)

It has been frequently pointed out in surveys such as those by Holdningsunders„pgelse, 1993, that ÐŽ§ people with no specific experiences with wind power believe that noise is louder than those who actually