How Much Wind Energy is there? – Brian Hurley – Wind Site Evaluation Ltd.

     brianhurley@wse.ie

see also: http://tx1.fcomet.com/~claverto/cms/where-does-the-wind-come-from-and-how-much-is-there.html

Introduction

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)

                                                                TWh/annum

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.

References:

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 [2004] and IEA[2003] differ due to different accounting procedures.