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Figure 1. Vertical global profiles of: differences between 2000 and 5-year average of (a) wind speed, (b) temperature, and (c) dew point temperature; (d) average temperature, dew point temperature, and wind speed (day and night) for the year 2000.

greater, are located near coasts, such as in Alaska and northern Europe. Overall, the application of the LS methodology to the world shows that 10.1% of the sounding locations belong to class 3 or greater at 80 m (Table 1) and are therefore suitable for wind power generation.

[24] Figure 3 shows the world map of V10 observed at all sounding locations with 20 or more valid readings. This map can be used to evaluate the world 80-m map (Figure 2) because there should be a correlation between windy locations at the surface and windy locations at 80 m. In fact, the two maps show generally the same distribution of wind power class (e.g., South-East Asia and Australia). Wind shear, however, can vary at locations with similar surface conditions, and thus generate differences in wind classes at 80 m. As shown in Table 1, 75.6% (75.4%) of the sounding stations fell in class 1 at 80 m (10 m). Fewer stations fell in class 3 or greater at 80 m (10.1%) than at

10 m (14.7%), suggesting that the LS methodology might be conservative when applied directly to vertical profiles (Step 1 above). Note that more stations are shown at 10 m (570) than at 80 m (446) because not all sounding stations retrieve a complete vertical profile of winds.

[25] Wind shear can be evaluated further in Table 2, which shows the number of stations that stayed in the same class at 80 m and at 10 m (Class80 = Class10), moved up (Class80 > Class10), or moved down (Class80 < Class10) among the 446 sounding stations for each 10-m class. In 75.3% of the cases, a sounding station was found to offer the same wind power potential at 80 m as it did at 10 m. This suggests that, to a first approximation, a station with good potential at 10 m offers also a good potential at 80 m. However, for a given wind power class at 10 m, the LS methodology was more likely to estimate a lesser than a greater wind power class at 80 m (17.9% versus 6.7%

Figure 2. Map of wind speed extrapolated to 80 m and averaged over all days of the year 2000 at sounding locations with 20 or more valid readings for the year 2000.

respectively). This, again, is indicative of a conservative approach.

[26] When applied to the 7753 surface stations (Steps 2 and 3), the LS methodology produced similar results to those obtained for the sounding stations in terms of percentages in each wind power class. From Table 1, about 76% of the surface stations were in class 1 and ~13% offered appreciable wind power potential at 80 m (class 3 or greater). However, this value was slightly larger than that at 10 m (12.1%), the opposite of what was found for sounding stations. In fact, the application of the LS methodology to surface stations was more likely to predict a move up (10.6%) than a move down (6.9%) at 80 m for a given 10-m class (Table 2). This finding could potentially compromise the conservative nature of the methodology and will be analyzed in detail in the next section.

[27] Since a map of V80 at 7753 surface and 446 sounding stations analogous to Figure 2 is difficult to read, results will be shown for the following regions: Europe,

Australia, South America, North America, South-East Asia, North-Central Asia, and Africa. Comparison with previous work is limited to published studies and to reports freely available to the public.

[28] The map of Europe is shown in Figure 4. A previous European map was created by Troen and Petersen [1989] (available at http://www.windpower.org/en/tour/wres/ euromap.htm). Both maps show that the greatest potential in Europe is along northeastern coasts, particularly in France, Belgium, Netherlands, Germany and Denmark. The coasts of the United Kingdom and the islands in the North Sea have stations mainly in class 7 too. However, the present study did not find class 7 potential over the Scandinavian Peninsula and Ireland; this study also offers results for Eastern Europe. A wind atlas for the Baltic region was developed by Rathmann [2003], but at 50 m above ground and for a constant roughness length of 0.10 m. Figure 4 shows that Slovakia and the Czech Republic have several locations in class 7, but none is found in Austria or Russia (except along the northern coast). Table 3 shows that

Table 1. Number and Percent of Stations in Each Wind Power Class at Both 80 and 10 m for the Year 2000 at Sounding, Surface, and All Locations Worldwide With at Least 20 Valid Measurements8

Class

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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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