Sunday, October 28, 2012

Energy Generation: Large Wind Turbines

Electricity generation from the wind is the best developed of the newer renewable energy technologies. It relies on relatively simple mechanical processes, once built the running costs are very low, and it has benefited from recent technological advances in the aeronautics industry. The fuel is free and inexhaustible and there are no waste products. This means it can compete with the cost of energy based on conventional fossil fuels, even though the price of electricity from traditional generation has fallen over the past 10 years.

The UK has the greatest potential for wind power in Europe, but we have been slow to exploit it. Other European countries such as Germany and Denmark lead the way. Studies show we could obtain 15 per cent of our current electricity needs from onshore wind, and the potential for offshore wind power is vast.

Wind power is a clean, renewable form of energy, which during operation produces no carbon dioxide. It also emits no sulphur dioxide, the cause of acid rain. While some emissions of these gases will take place during the design, manufacture, transport and erection of wind turbines, enough electricity is generated from a wind farm within a few months to totally compensate for these emissions. When wind farms are dismantled (usually after 20 years of operation) they leave no legacy of pollution for future generations.

Although there are vast quantities of wind energy available, harnessing the wind involves capturing energy that is relatively diffuse in the environment. Critics claim large, centralised power stations are more efficient, and that wind power will never be able to replace them. While individual turbines may not contribute much on a
national scale, collectively they can make a huge difference. The Department of Trade and Industry (DTI) calculates that onshore wind could theoretically meet 100 per cent of our current electricity demand, and that the offshore resource could supply 10 times this amount. More conservative estimates, taking into account factors such as land availability, suggest a practicable figure of 40 per cent of current electricity generation from on- and offshore wind.

Is electricity from the wind reliable? It is true that wind turbines only operate when the wind blows. However, the UK is the windiest country in Europe so we have a large resource waiting to be used.Less windy countries such as Germany are already meeting 3.5 per cent of their electricity needs from wind. There is a lot of confusion about the reliability of different sources of electricity. No power stations are able to operate all the time without stopping. Many so called reliable sources such as nuclear plants suffer from unexpected ‘outages’ when reactors must be shut down, often at short notice, for essential safety maintenance. Unreliability of this kind is far harder to deal with as the amounts of electricity involved are generally much higher. By comparison the variation in output from wind farms distributed around the country is scarcely noticeable. A great advantage of wind power is that the available wind resource is much greater during the colder months of the year, when energy demand is at its highest. At present the National Grid can be operated effectively and economically with up to 20 per cent of the electricity capacity being provided by variable energy sources such as wind. At the levels being considered over the next few decades for wind energy production, such variability can easily be accommodated by the grid system. It is true that we could never rely on wind turbines alone to provide for all our electricity needs. But there are storage technologies we can use, such as pumped storage hydro power schemes (where water is pumped up-hill, thus acting like large batteries for the electricity system), as well as more flexible renewable technologies such as energy from bio-waste and bio-crops. Coupled with these sources, wind farms can replace a large portion of our existing nuclear and fossil-fired electricity generation without reducing the overall reliability of our electricity supplies.

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