Wind power

Wind is the movement of air in response to pressure differences within the atmosphere. Pressure differences exert a force which cause air masses to move from a region of high pressure to one of low pressure. That movement is wind. Such pressure differences are caused primarily by differential heating effects of the sun on the surface of the earth. Thus wind energy can be considered to be a form of solar energy.

Annually, over the earth's land masses, around 1.7 million TWh of energy is generated in the form of wind. Over the globe as a whole the figure is much higher. Even so, only a small fraction of the wind energy can be harnessed to generate useful energy.

One of the main limiting factors in the exploitation of wind power onshore is competing land use. Taking this into account, a 1991 estimate1 put the realisable global wind power potential at 53,000 TWh/year. This figure is broken down by regions in Table 11.1. As the table shows, wind resources are widely dispersed and available in most parts of the world.

The figures in Table 11.1 are probably conservative because modern wind turbines are more efficient than those available when the survey was compiled. Even on this conservative estimate the resource is much larger than world demand for electricity. This is expected to reach 26,000 TWh, roughly half the global wind resource quoted above, by 2020.2

Table 11.1 Regional wind resources

Available resource

(TWh/year)

Table 11.1 Regional wind resources

Available resource

(TWh/year)

Western Europe

4800

North America

14,000

Australia

3000

Africa

10,600

Latin America

5400

Eastern Europe and

10,600

Former Soviet Union

Asia

4600

Total

53,000

Table 11.2 European wind energy resources

Annual resource (TWh)

Potential capacity (MW)

Austria

3

1500

Belgium

5

2500

Denmark

10

4500

Finland

7

3500

France

85

42,500

Germany

24

12,000

Great Britain

114

57,000

Greece

44

22,000

Ireland

44

22,000

Italy

69

34,500

Luxembourg

-

-

Holland

7

3500

Norway

76

38,000

Portugal

15

7500

Spain

86

43,000

Sweden

41

20,500

Source: The figures in this table are taken from Windforce 12.3

Source: The figures in this table are taken from Windforce 12.3

Table 11.2 shows estimates for the wind energy resources in the countries of Western Europe. A glance at these estimates will show that in many cases the national wind resources are again enormous. These figures, too, may represent an underestimate. For example, the potential UK generating capacity has been estimated by the UK Energy Technology Support Unit (ETSU) to be 223,000 MW, nearly four times the figure quoted in Table 11.2 and equivalent to an annual production of 660,000 GWh. The ETSU study used relatively conservative criteria to arrive at its estimate but did not take into account utilisation restrictions. Constraints on building close to population centres or in areas of natural beauty would severely limit available sites. Even with such constraints, the potential would remain vast.

Looking beyond Europe, a US wind potential survey was carried out in 1992.4 It concluded that even with exclusions for environmental and land-use reasons, around 6% of the land area of the USA could be used for wind power generation. This area was judged capable, with some advance in wind turbine technology, of providing a generating capacity of 500,000 MW. The report also concluded that 12 states in the middle of the USA had sufficient potential to generate nearly four times the electricity consumed in the USA 1990.

In Asia, potential Chinese generating capacity has been put at 253,000 MW. Indian potential has been estimated at 20,000 MW but this is certainly a severe underestimate. Both countries are beginning to exploit their potential.

Wind power, though exploiting a renewable resource, is not considered beneficial by all. In the UK, and increasingly in Germany there are lobbies trying to prevent further development of onshore wind farms. This is proving a considerable handicap to wind development in the UK, at least. Under these conditions, offshore wind farming becomes increasingly attractive.

It is more expensive to build a wind farm offshore but this can be offset by higher average wind speeds. The global offshore resource has been estimated to be around 37,000 TWh.5 Offshore sites are available in many parts of the world but the most promising for immediate development are around the coasts of northern and western Europe and of the eastern seaboard of the USA.

At the beginning of 2004 the global wind generating capacity was 40,000 MW.6 It is expected to reach 150,000 by 2012. Offshore capacity at the end of 2003 was just over 500 MW.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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