The wind: Wind energy come with the wind. The wind moves the blades. These are attached to a rotor from which power is transferred through a gearbox to a generator. The gearbox and generator are contained within a housing called a nacelle.
.
In the last years, research has made great steps: technology, design, materials, software. Wind energy is a light, smart and flexible technology, with a low environmental impact.
Efficiency and visual design have all improved enormously. Wind turbines have also grown larger and taller. The generators in the largest modern turbines are 100 times the size of those in 1980. Over the same period, their rotor diameters have increased eight-fold. the average capacity of turbines installed around the world during 2007 was 1,492 kW, while the largest turbine currently in operation is the enercon e126, with a rotor diameter of 126 metres and a power capacity of 6 mW.
Modern turbines are modular and quick to install; the site construction process can take a matter of months. This is of particular importance for countries in need of a rapid increase in electricity generation. Wind farms can vary in size from a few megawatts up to several hundred.
The wind is for free. The wind is everywhere: It's not like for oil or coal: unlikely we will see wars to control the wind. No one superpower will be able to take control of the wind. No market will speculate on its price. The wind cannot be imported and exported. It comes and goes, but it never disappears. When the air is calm somewhere, the wind is blowing somewere else. A smart network grid can compensate the gaps.
Wind is an intermittent energy source, and thus is often described as unreliable. Today, wind power prediction is quite accurate for aggregated wind farms and large areas. using increasingly sophisticated weather forecasts, wind power generation models and statistical analysis, it is possible to predict generation from five minute to hourly intervals over timescales up to 72 hours in advance, and for seasonal and annual periods. using current tools, the forecast error for a single wind farm is between 10 and 20% of the power output for a forecast horizon of 36 hours. for regionally aggregated wind farms the forecast error is in the order of 10% for a day ahead and less than 5% for 1-4 hours in advance.
Changing weather makes people switch their heating, cooling and lighting on and off, millions of consumers expect instant power for tvs and computers. On the supply side, when a large power station, especially, if it is a nuclear reactor, goes offline, whether by accident or planned shutdown, it does so instantaneously, causing an immediate loss of many hundreds of megawatts. by contrast, wind energy does not suddenly trip off the system. Variations are smoother because there are hundreds or thousands of units rather than a few large power stations, making it easier for the system operator to predict and manage changes in supply. especially in large, interconnected grids, there is little overall impact if the wind stops blowing in one particular place.
The effects of geographical distribution can also be significant. Whereas a single wind farm can experience power swings from hour to hour of up to 60% of its capacity, monitoring by the German iset research institute has shown that the maximum hourly variation across 350 mW of aggregated wind farms in Germany does not exceed 20%. across a larger area, such as the nordel system covering four countries (finland, sweden, norway and eastern denmark), the greatest hourly variations would be less than 10%, according to studies.
Holttinen, H. (2004): The impact of large scale wind power on the Nordic electricity system
The wind is competitive: Wind energy makes sound economic sense. in contrast to new gas, coal or even a nuclear power plants, the price for fuel over the total lifetime of a wind turbine is well known: it is zero. For conventional generation technologies, future price developments are a significant risk factor, and if current trends are any indication, they are likely to continue rising into the unforeseeable future.
The total cost per generated kWh of electricity is traditionally calculated by discounting and levelising investment and O&m costs over the lifetime of a wind turbine, then dividing this by the annual electricity production. The unit cost of generation is thus calculated as an average cost over the lifetime of a turbine, which is normally estimated at 20 years. In reality capital costs will be higher in the early years of a turbine’s operations while the loan is being paid off, where as O&m costs will probably be lower at the beginning of a turbine’s operation and increase over the lifespan of the machine. The cost of generating electricity from wind energy currently ranges from approximately 4-6 €cents/kWh at high wind speed sites up to approximately 6-9 €cents/kWh at sites with low average wind speeds (European Commission, 2003, External Cost –http://www.externe.info/externpr.pdf)
Over the past 15 years the efficiency of wind turbines has been improving thanks to better equipment design, better siting and taller turbines. furthermore, it can be assumed that optimised production processes will reduce investment costs for wind turbines, as described above.
These calculations do not take into account the so-called ‘external costs’ of electricity production. it is generally agreed that renewable energy sources such as wind have environ- mental and social benefits compared to conventional energy sources such as coal, gas, oil and nuclear. these benefits can be translated into costs for society, which should be reflected in the cost calculations for electricity output. Only then can a fair comparison of different means of power production be established. the european commission’s externe project estimated the external cost of gas fired power generation at around 1.1-3.0 €cents/kWh and that for coal at as much as 3.5-7.7 €cents/kWh, compared to just 0.05-0.25 €cents/kWh for wind.
Country
MW
%
US
5,244
26.4
Spain
3,522
17.7
China
3,304
16.6
India
1,575
7.9
Germany
1,667
8.4
France
888
4.5
Italy
603
3.0
Portugal
434
2.2
UK
427
2.1
Canada
386
1.9
Others
1,815
9.1
Top 10
18,050
90.9
Global
19,864
100.0
The wind is clean: Wind energy produces no carbon dioxide - the main greenhouse gas contributing to climate change – during its operation, and minimal quantities during the manufacture of its equipment and constructionof wind farms. By contrast, fossil fuels such as coal, gas and oil are major emitters of carbon dioxide.
Wind power also has a positive effect on the quality of the air we breathe. the combustion of fossil fuels also produces the gases sulphur dioxide and nitrogen oxide, both serious sources of pollution. these gases are the main components of the ‘acid rain’ effect - killing forests, polluting water courses and corroding facades of buildings; not to mention the human health effects.
Wind energy avoids the numerous issues associated with the discovery and exploitation of fossil fuels. deaths from mining, the massive destruction of strip mining and ‘hill-top removal’ and fuel spills are just some of the consequences of dependence on recovering raw materials for electricity generation from under the ground.
Researchers at stanford university’s Global climate and energy project recently did an evaluation of the global potential of wind power, using five years of data from the us national climatic data center and the forecasts systems laboratory. They estimated that the world’s wind resources can generate more than enough power to satisfy total global energy demand. after collecting measurements from 7,500 surface and 500 balloon-launch monitoring stations to determine global wind speeds at 80 metres above ground level, they found that nearly 13% had an average wind speed above 6.9 metres per second (class 3), sufficient for economical wind power generation. Using only 20% of this potential resource for power generation, the report concluded that wind energy could satisfy the world’s electricity demand in the year 2000 seven times over.
Within europe, Denmark already gets 21% of its gross electricity demand from the wind, Spain almost 12%, Portugal 9%, Ireland 8% and Germany 7%. some regions achieve much higher penetrations. In the western half of Denmark, for example, more than 100% of demand is sometimes met by wind power.
Wind energy is reversible:: If mistakenly placed, a wind turbine can be removed easily, with no impact. Its not that easy to dismantle a nuclear power plant (in fact they are usually not dismantled). It is far more difficult to remove the coal emissions from the atmosphere, or manage radioactive waste for centuries.
Wind turbines are highly visible elements in the landscape: hey need to be tall in order to catch the prevailing wind and work effectively. how people perceive them varies, but many see wind farms as elegant and graceful symbols of a better, less polluted future. If compared to nuclear or coal, the visual impact and landscape is considerably lower.
