1. Introduction
During the last decade, wind characteristics and wind power potential have been studied in many countries worldwide [
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20,
21,
22,
23,
24,
25,
26,
27,
28,
29,
30,
31,
32,
33,
34,
35,
36,
37,
38,
39,
40,
41,
42,
43,
44,
45,
46,
47,
61,
63,
64,
65], demonstrating that despite the prolonging global economic crisis, the worldwide wind power ascent continues. The world’s wind power capacity added 38.6 GW in 2009, growing by 32%/year and 38.1 GW in 2010 (24%/year growth), demonstrating 110% growth in three years, to extend total installations up to 197.0 GW. A huge part of this capacity was installed in China with 22.7% of the world wind energy yield (about third of the world year’s additions) and USA with 20.4%, while Germany, Spain and India installing cumulative capacity of 30.9% together [
48].
Wind energy became a significant player in the world’s energy market. Global market worth of wind turbine installations in 2009 was around 63 billion US
$. About half a million people are now employed, corresponding to GWEC estimates, by the wind industry around the world [
49]. Main markets of the wind energy are situated in Asia, North America, and Europe, each of which adds more than 10 GW capacity a year.
Considering the Israeli energy market, the desire to add to the natural gas found, which is a nonrenewable local energy resource has also motivated the state to devote various efforts to the ‘green’ energy research and development, primarily in the area of solar energy. Recently, wind energy drew attention of energy initiatives as well. Yet the wind power amount produced in Israel is diminutive comparing to the continuously growing global market; however, the last steps undertaken by the state are destined to improve the situation.
Israel currently operates a single wind farm in Asanyia Hill in the Golan Heights, with total installed capacity of 6 MW (consisting of ten 600 kW turbines), satisfying the consumption of about 5 thousand families. The wind farm operates around 97% of the time and yields revenue of ~1 million US
$ a year. Indeed, wind energy potential of Israel is restricted because of surplus of moderate- or poor-wind velocities’ areas and is limited to the areas with sufficiently constant wind, some of which are being opposed by green groups on landscape conservation grounds. Nevertheless, the state continues efforts for bringing into operation of two more farms with a 50 MW capacity [
50].
It is emphasized in the Israel Knesset document that an improved estimate, based on the wind turbines’ technological development, gives a value much more than 500 MW of the Israeli potential wind energy capacity [
51]. One of perspective areas for efficient wind technology development, considering its climatic characteristics, is the Samaria region.
It is well known that energy yield of a wind turbine mainly depends on wind energy characteristics and turbine power curve [
52,
53]. In this paper, statistical characteristics of the wind speed behavior in Ariel (located in Samaria) are derived and investigated, relying on data collected be meteorological station located in Ariel University campus.
2. Materials and Methods
Eleven years of meteorological data (2001-2011), acquired by Ariel Meteorological Station and supplied by the Israeli Meteorological Service were processed. Measurement samples were taken at 10-meter height above the ground and were available at 10 minutes intervals. The city of Ariel is located at 32° 6′ 21.6″ N, 35° 11′ 16.43″ E, in the center of Israel (
Figure 1). Ariel Meteorological Station is located inside Ariel University campus at eastern part of the city (
Figure 2), residing at 700 m above sea level.
The wind speed data was provided by meteorological station as raw matrix of wind speed ad azimuth versus time at 10 m height, sampled at 10 minutes. In reality, the sample time is much higher than stated and the available data sample is actually an average of tens to thousands of faster samples. An example of monthly wind speed raw data in Ariel represented by 10 minutes samples is shown in
Figure 3.
The raw vector is used to extract mean and standard deviation parameters and then can be either transformed into a histogram (discrete probability distribution function – PDF) or fitted to a known PDF, typically of Weibull type, as shown in
Figure 4. When creating a histogram, the bins are typically chosen to be 1 m∙s
-1 wide to match the resolution of the manufacturer provided turbine power curve data, resulting in the following discrete PDF,
where
is the magnitude of the histogram bin, centered at
.
Weibull PDF is defined by two parameters: shape or Weibull modulus (k, dimensionless), and scale (c, m/s for wind speed). The general form of the Weibull PDF is given by:
for positive wind speeds (v > 0) with parameters c and k = related to the site wind speed mean μ
v and standard deviation σ
v as [
54]:
And
respectively, where:
is the complete Gamma function. In case the wind raw data of a site is unavailable, but the mean and standard deviation of the wind speed are given, Weibull PDF is usually assumed, and its parameters are extracted from (4) and (5). In general, several ways to extract Weibull parameters from raw data exist [
55]; MATLAB function
wblfit was used in this work.
A particular (and very common) case of Weibull PDF is the case where k = 2. It is called Rayleigh PDF and is given by
for positive wind speeds (v > 0) with scale parameter c related to the site mean wind speed as
making (6) to be dependent on average wind speed as [
56]:
It is worth noting that wind energy resource is typically classified according to average wind speed at 10 m height as shown in
Table 1 [
56].
Since power in the wind increases with height [
57,
58], the turbine hub of medium and large-scale wind turbines is usually located a 50 – 150 m height. Therefore, statistical wind parameters must be either measured at hub height or extrapolated from measurements available at smaller heights. In case single height measurements only are available, power law is usually employed to estimate wind speed
at height
as
where
is the wind speed measurement available at height
and
is the surface roughness dependent friction coefficient [
59,
60]. Friction coefficient dependence on terrain characteristics is typically determined from
Table 2 [
56].
According to the above, a software simulator was created receiving meteorological data (excel format) as an input and calculating the following output. Using the wind speed raw data, mean and standard deviation (STD) vales were calculated, followed by Weibull parameters extraction, and plotting respective histograms along with resulting Weibull PDFs. The process was repeated after extrapolating the samples to 70-meter height using friction coefficient of 0.3 according to
Table 2. All the results were calculated monthly, annually, and seasonally. As to wind directions, annual Rose diagrams were created for both 10 and 70 m heights.
Figure 1.
The city of Ariel.
Figure 1.
The city of Ariel.
Figure 2.
Meteorological station location.
Figure 2.
Meteorological station location.
Figure 3.
Typical monthly wind speed raw data.
Figure 3.
Typical monthly wind speed raw data.
Figure 4.
Histogram and Weibull PDF fit of wind speed raw data of
Figure 3.
Figure 4.
Histogram and Weibull PDF fit of wind speed raw data of
Figure 3.
Figure 5.
2001 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 5.
2001 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 6.
2002 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 6.
2002 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 7.
2003 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 7.
2003 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 8.
2004 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 8.
2004 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 9.
2005 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 9.
2005 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 10.
2006 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 10.
2006 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 11.
2007 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 11.
2007 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 12.
2008 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 12.
2008 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 13.
2009 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 13.
2009 wind speed data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 14.
2010 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 14.
2010 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 15.
2011 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 15.
2011 wind speed raw data Histogram and Weilbull PDF. Top–10 m height, Bottom–70 m height.
Figure 16.
2001-2011 Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 16.
2001-2011 Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 17.
2001-2011 parameter variations at 10 m. Top–statistical, Bottom–Weibull.
Figure 17.
2001-2011 parameter variations at 10 m. Top–statistical, Bottom–Weibull.
Figure 18.
2001-2011 spring Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 18.
2001-2011 spring Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 19.
2001-2011 autumn Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 19.
2001-2011 autumn Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 20.
2001-2011 summer Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 20.
2001-2011 summer Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 21.
2001-2011 winter Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 21.
2001-2011 winter Weilbull PDFs. Top–10 m height, Bottom–70 m height.
Figure 22.
2001 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 22.
2001 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 23.
2002 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 23.
2002 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 24.
2003 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 24.
2003 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 25.
2004 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 25.
2004 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 26.
2005 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 26.
2005 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 27.
2006 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 27.
2006 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 28.
2007 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 28.
2007 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 29.
2008 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 29.
2008 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 30.
2009 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 30.
2009 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 31.
2010 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 31.
2010 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 32.
2011 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 32.
2011 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 33.
2001-2011 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 33.
2001-2011 wind rose diagrams. Top–10 m height, Bottom–70 m height.
Figure 34.
Power curves of wind turbines [
66]. The dashed thick curve is the power curve of Enercon’s model E101/3000 turbine, the thick line is the power curve of AWE’s model 54–900 turbine, and the dashed curve is the power curve of EWT’s model Direct wind 52/750 turbine.
Figure 34.
Power curves of wind turbines [
66]. The dashed thick curve is the power curve of Enercon’s model E101/3000 turbine, the thick line is the power curve of AWE’s model 54–900 turbine, and the dashed curve is the power curve of EWT’s model Direct wind 52/750 turbine.
Table 1.
Wind power classification.
Table 1.
Wind power classification.
Wind Power Class |
Average Wind Speed (m/s) at 10 m Height |
1 |
0 – 4.4 |
2 |
4.4 – 5.1 |
3 |
5.1 – 5.6 |
4 |
5.6 – 6.0 |
5 |
6.0 – 6.4 |
6 |
6.4 – 7.0 |
7 |
7.0– 9.5 |
Table 2.
Friction coefficient dependence in terrain type.
Table 2.
Friction coefficient dependence in terrain type.
Terrain Characteristics |
α |
Smooth hard ground, calm water |
0.10 |
Tall grass on level ground |
0.15 |
High crops, hedges and shrubs |
0.20 |
Wooded countryside, many trees |
0.25 |
Small town with trees and shrubs |
0.30 |
Large city with tall building |
0.40 |
Table 3.
Yearly and cumulative wind speed statistics at 10 m height.
Table 3.
Yearly and cumulative wind speed statistics at 10 m height.
Year |
Parameter |
Speed |
Azimuth |
2001 |
Mean |
4.28 |
209.41 |
STD |
2.21 |
81.13 |
2002 |
Mean |
4.89 |
227.31 |
STD |
2.51 |
83.03 |
2003 |
Mean |
4.81 |
224.15 |
STD |
2.57 |
78.48 |
2004 |
Mean |
4.57 |
228.17 |
STD |
2.49 |
80.32 |
2005 |
Mean |
4.64 |
227.63 |
STD |
2.33 |
77.45 |
2006 |
Mean |
4.35 |
231.65 |
STD |
2.20 |
83.15 |
2007 |
Mean |
4.50 |
228.73 |
STD |
2.21 |
79.28 |
2008 |
Mean |
4.50 |
221.94 |
STD |
2.25 |
77.23 |
2009 |
Mean |
4.54 |
231.31 |
STD |
2.38 |
75.39 |
2010 |
Mean |
4.41 |
225.30 |
STD |
2.27 |
79.84 |
2011 |
Mean |
4.26 |
230.11 |
STD |
2.08 |
79.28 |
2001-2011 |
Mean |
4.53 |
226.00 |
STD |
2.32 |
79.76 |
Table 4.
Yearly and cumulative wind speed statistics at 70 m height.
Table 4.
Yearly and cumulative wind speed statistics at 70 m height.
Year |
Parameter |
Speed |
Azimuth |
2001 |
Mean: |
7.72 |
209.41 |
STD: |
3.94 |
81.13 |
2002 |
Mean: |
8.78 |
227.31 |
STD: |
4.50 |
83.03 |
2003 |
Mean: |
8.68 |
224.15 |
STD: |
4.57 |
78.48 |
2004 |
Mean: |
8.24 |
228.17 |
STD: |
4.43 |
80.32 |
2005 |
Mean: |
8.37 |
227.63 |
STD: |
4.15 |
77.45 |
2006 |
Mean: |
7.82 |
231.65 |
STD: |
3.94 |
83.15 |
2007 |
Mean: |
8.07 |
228.73 |
STD: |
3.97 |
79.28 |
2008 |
Mean: |
8.07 |
221.94 |
STD: |
4.04 |
77.23 |
2009 |
Mean: |
8.15 |
231.31 |
STD: |
4.28 |
75.39 |
2010 |
Mean: |
7.91 |
225.30 |
STD: |
4.08 |
79.84 |
2011 |
Mean: |
7.64 |
230.11 |
STD: |
3.74 |
79.28 |
2001-2011 |
Mean: |
8.13 |
226.00 |
STD: |
4.17 |
79.76 |
Table 5.
Monthly, yearly, and cumulative Weibull parameters at 10 m height.
Table 5.
Monthly, yearly, and cumulative Weibull parameters at 10 m height.
Table 6.
Monthly, yearly, and cumulative Weibull parameters at 70 m height.
Table 6.
Monthly, yearly, and cumulative Weibull parameters at 70 m height.
Table 7.
Seasonal variation of Weibull parameters at 10 m height.
Table 7.
Seasonal variation of Weibull parameters at 10 m height.
|
Parameter |
2001 |
2002 |
2003 |
2004 |
2005 |
2006 |
2007 |
2008 |
2009 |
2010 |
2011 |
winter Nov-Jan
|
c |
4.53 |
5.25 |
5.48 |
5.03 |
4.67 |
4.99 |
5.08 |
5.86 |
5.51 |
5.68 |
4.94 |
k |
1.85 |
2.12 |
2.13 |
2.29 |
1.88 |
2.21 |
2.35 |
2.04 |
1.83 |
1.99 |
2.02 |
Spring Feb-Apr
|
c |
4.63 |
5.80 |
5.77 |
5.69 |
6.05 |
5.38 |
4.75 |
5.58 |
5.66 |
5.26 |
5.30 |
k |
1.84 |
2.29 |
2.06 |
2.18 |
2.26 |
1.96 |
2.20 |
2.23 |
1.95 |
1.93 |
1.97 |
Summer May-Jul
|
c |
5.33 |
5.58 |
4.80 |
4.84 |
5.37 |
4.65 |
5.94 |
4.55 |
4.87 |
4.83 |
4.72 |
k |
2.00 |
2.10 |
2.05 |
1.92 |
1.99 |
2.03 |
2.62 |
2.35 |
2.24 |
2.34 |
2.58 |
Autumn Aug-Oct
|
c |
4.53 |
5.43 |
5.21 |
4.75 |
5.48 |
5.23 |
4.90 |
4.33 |
4.50 |
4.14 |
4.29 |
k |
2.39 |
2.08 |
2.08 |
2.05 |
2.05 |
1.99 |
2.51 |
2.30 |
2.41 |
2.36 |
2.50 |
Table 8.
Seasonal variation of Weibull parameters at 70 m height.
Table 8.
Seasonal variation of Weibull parameters at 70 m height.
|
Parameter |
2001 |
2002 |
2003 |
2004 |
2005 |
2006 |
2007 |
2008 |
2009 |
2010 |
2011 |
winter Nov-Jan
|
c |
8.12 |
9.42 |
9.82 |
9.03 |
8.37 |
8.95 |
9.11 |
10.51 |
9.88 |
10.18 |
8.85 |
k |
1.85 |
2.12 |
2.13 |
2.29 |
1.88 |
2.21 |
2.35 |
2.04 |
1.83 |
1.99 |
2.02 |
Spring Feb-Apr
|
c |
8.31 |
10.41 |
10.34 |
10.21 |
10.84 |
9.64 |
8.52 |
10.01 |
10.14 |
9.44 |
9.50 |
k |
1.84 |
2.29 |
2.06 |
2.18 |
2.26 |
1.96 |
2.20 |
2.23 |
1.95 |
1.93 |
1.97 |
Summer May-Jul
|
c |
9.55 |
10.01 |
8.60 |
8.68 |
9.62 |
8.34 |
10.64 |
8.16 |
8.73 |
8.67 |
8.47 |
k |
2.00 |
2.10 |
2.05 |
1.92 |
1.99 |
2.03 |
2.62 |
2.35 |
2.24 |
2.34 |
2.58 |
Autumn Aug-Oct
|
c |
8.12 |
9.73 |
9.34 |
8.51 |
9.83 |
9.38 |
8.79 |
7.76 |
8.07 |
7.42 |
7.68 |
k |
2.39 |
2.08 |
2.08 |
2.05 |
2.05 |
1.99 |
2.51 |
2.30 |
2.41 |
2.36 |
2.50 |
Table 9.
Wind turbine geometric parameters.
Table 9.
Wind turbine geometric parameters.
Turbine |
Enercon’s E101/3000 |
AWE’s 54–900 |
EWT’s Directwind 52/750 |
Area (m2) |
8012 |
2290 |
2083 |
Radius (m) |
50.5 |
27 |
25.75 |
Table 10.
Wind turbine power & economic yield.
Table 10.
Wind turbine power & economic yield.
Turbine |
Enercon‘s E101/3000 |
AWE’s 54–900 |
EWT’s Directwind 52/750 |
Average Power (kW) |
1380.97 |
379.06 |
333.25 |
Power Standard Deviation (kW) |
1160.94 |
326.58 |
275.32 |
Annual Revenue (Million SH) |
6.46 |
1.77 |
1.56 |
Annual Revenue (Million $) |
1.84 |
0.50 |
0.44 |