The starting point is an estimate of the total quantity of kinetic energy in the atmosphere. Lorenz gives 1.5 x 106Joules/m2 as the quantity of kinetic energy contained in the atmosphere(1). Smil gives a figure described as the annual “solar radiation reaching the earth” as equal to 5.8 x 1024Joules, or 1.84 X 1017W, and 360W/m2(2). Annual Solar radiation absorbed by earths surface(land and sea) 2.9 x 1024Joules, or 9.19 X 1016W, and 180W/m2. Note the solar constant is 1,366W/m2. Smil refers to a source from Lorenz(1976) that “atmospheric motion” was about 2% of 3.5PW insolation. ( Applying 2% to Smil’s 9.19 X 1016W giving 1.84 X 1015W with his figure for winds below 1km 1.22 x 1015W is the right order of magnitude
Smil gives a figure, 3.8 x 1022 Joules, for the annual flux for the winds in the atmosphere below a height of 1km(2). He puts the maximum convertible at 3.8 x 1021 Joules or 1.1 x 106 TWh.
World Wind Resources
The world’s wind resources are estimated to be 50,000 TWh/year(3). The total potential is calculated by taking the land with an average wind speed above 5.1 m/s at 10 m height. Then it has been reduced by 90 % to take into account other uses, population density etc. The assessment does not include Greenland, the Antarctic or offshore areas. Another assessment by Wijk and Coelingh giving 20,000 TWh/year is more conservative (4)
Region Grubb and Meyer (3) Wijk and Coelingh (4)
Africa 10 600
Australia 3 000 1 638
North America 14 000 3 762
Latin America 5 400
Western Europe 480 520
Eastern Europe and CIS 10 600
Rest of Asia 4 900
Approx. world total 50 000 20 000
Another source gives a higher total figure of 106,458TWh/year for the OECD countries only(5). This includes New Zealand and Japan. A Stanford University study found that the total wind power potential over land from class ? 3 areas can be estimated roughly as 72 TW, corresponding to 6.27 x 1014 kWh or 627,000TWh (8).
None of these studies include the offshore potential which is estimated to be in excess of 3000 TWh/annum in European waters alone within a distance of 30km from shore and in depths less than 40m(6). Comparing the Smil figure, 1,100,000TWh, and that from Wind Energy-The Facts report, 50,000TWh, it is to be noted that the Smil figure is for the whole globe both land and sea, whereas the Wind Energy-The Facts report one is the amount that could be extracted by wind turbines in the first 120m of the 1km considered, and taking into account loss and reduction factors. (2)(3). The current production of the 100GW of installed wind turbines would be of the order of 2.2 x 102 TWh assuming a 25% capacity factor.
The world’s electricity consumption was about 18,000 TWh/year for 2005(7). The total available global wind resource on land is therefore more than adequate to supply a very significant proportion of the overall world’s electricity demand.
1. Lorenz, Edward N., The nature and theory of the general circulation of the atmosphere., p110 WMO No. 218 TP.115. World Meteorological Organization
2. Smil, Vaclav. Inherent limits of renewable energies. 2004
3. Wind Energy – The Facts. Volume 1. European Commission
Directorate-General for Energy. 1999.
4. van Wijk, A.J.M. and Coelingh, J.P., Wind Power Potential in the OECD Countries, December 1993. Report commissioned by the Energy Research Center, The Netherlands (ECN)
5. personal communication from Hughes, P, and Hurley, B. Airtricity
6. Garrad Hassan and Partners, Germanischer Lloyd, Windtest KWK. 1995.
7. BP Statistical Review of World Energy June 2006
8. Archer, Cristina L. and Jacobson, Mark Z. Evaluation of global wind power. 2005
*The estimates of global electricity and energy demand by EIA  and IEA differ due to different accounting procedures.