ً‫” وهو الذى أرسل الرياح بشرا‬
‫ وأنزلنا من‬، ‫بين يدى رحمته‬
48 - ‫السماء ما ًء طهوراً ” الفرقان‬
And He it is Who sends the winds as
heralds of glad tidings, going before
His mercy, and We send down pure
water from the sky,
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Wind Resource Assessment
Program
Prepared by
Eng. Ashour Abdelsalam Moussa
Wind Energy Dep.,
New & Renewable Energy Authority (NREA)
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The World’s Energy
Resources Are Limited!
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World Wind Energy 2010
Worldwide capacity reached 196 630 Megawatt,
out of which 37 642 Megawatt were added in 2010
All wind turbines installed by the end of 2010
worldwide can generate 430 Terawatt hours per
annum, more than the total electricity demand of
the United Kingdom, the sixth largest economy
of the world, and equalling 2,5 % of the global
electricity consumption.
The wind sector in 2010 had a turnover of 40
billion Euro and employed 670’000 persons
worldwide.
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China became number one in total installed capacity and
the center of the international wind industry, and added
18 928 Megawatt within one year, accounting for more
than 50 % of the world market for new wind turbines.
Germany keeps its number one position in Europe with
27 215 Megawatt, followed by Spain with 20 676 MW.
World
Market Update 2009
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March 2010 - Page 6
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World
Market Update 2009
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March 2010 - Page 7
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Top-10 Suppliers in 2009
% of the total market 38,103MW
GOLDWIND (PRC)
7.2%
GAMESA (ES)
6.7%
ENERCON (GE) 8.5%
DONGFANG (PRC)
6.5%
SINOVEL (PRC)
9.2%
SUZLON (IND)
6.4%
SIEMENS (DK)
5.9%
GE WIND (US)
12.4%
VESTAS (DK) 12.5%
REPOWER (GE)
3.4%
Others 18.5%
Source: BTM Consult ApS - March 2010
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Wind
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Why assess wind resource
1.The Power in the wind is proportional to Cube of
the wind speed (10% difference in wind speed
makes about 33% change in wind power). This
is the primary reason for wind resource
assessment.
2. Wind speed, wind shear*, turbulence** and gust
intensity all need to be specified when procuring a
wind turbine and designing its foundation….etc.
*Wind shears (large differences in the mean wind speed over the rotor) give
large fluctuating loads and consequently fatigue on the wind turbine blades,
because the blades move through areas of varying wind speed.
**Turbulence causes dynamic loads on wind turbines. The strength of the
turbulence varies from place to place. Over land the turbulence is more intense
than over the sea
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3. Turbine manufacturers concerns max.
turbulence intensity (16%), max. wind shear
acting on blade area (0.2) and max. one
second gust used for foundation design
Wind Resources assessments are the
cornerstone of identifying and mitigating risks
and for realizing the potential rewards from a
project.
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Without wind resource,
no wind project will even be viable.
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Griggs – Putman Wind Index
This index is based on the permanent
tree deformation caused by wind and
is useful for estimating the average
wind speed in an area.
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‫‪Use vegetation to know wind‬‬
‫‪direction and intensity‬‬
‫االساق عمودية واالغصان متحركة‬
‫الساق عمودية واالغصان ثابتة‬
‫ميل كامل والساق عمودية على االرض‬
‫الساق واالغصان كالسجادة‬
‫‪16‬‬
‫ميل متوسط‬
‫ميل شبه كامل للساق واالغصان‬
‫ميل خفيف لالغصان‬
‫ميل جزئى للساق واالغصان‬
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Prevailing Wind Direction
Important to check direction when
setting up instrument
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Information in the resource
assessment will include :• Daily average wind speeds
• Monthly average wind speeds
• Annual Average wind speeds
• Frequency distribution
• Wind Rose
• Wind power density
• Turbulence intensity
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Frequency distribution
•The basic tool for estimate
energy production.
•It shows the % of time that the
wind blowing at certain speed.
The wind speed are binned,
meaning that speed between 0
and 1 m/s are binned as 1 m/s,
wind speeds between 1 and 2
m/s are binned as 2 m/s, and
so on.
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Frequency distribution
+
Power Curve
Energy Production
To assess a site’s wind power production potential, the
wind speed frequency distribution must be multiplied
by a representative wind turbine power curve.
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Wind rose is a useful
tool to know the
wind blows.
It is a valuable tool
for project layout
and micro-siting
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Wind Power density (W/m2)
• It is defined as the wind power available per unit
area swept by the turbine blades.
• It is a true indication of wind energy potential in
the site than wind speed alone.
• Its value combines wind speed distribution and
air density.
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Wind Power Class Table
Class
Resource
Potential
Wind Power
density
w/m2
Wind speed
m/s
1
2
3
4
5
6
7
Poor
Marginal
Moderate
Good
Very Good
Excellent
Outstanding
< 200
200 – 300
300 – 400
400 – 500
500 – 600
600 – 800
> 800
< 5.6
5.6 – 6.4
6.7 – 7
7 – 7.5
7.5 – 8
8 – 8.8
> 8.8
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Turbulence intensity
• It is the rapid disturbances in the wind speed and
direction.
Low < 0.1
Medium 0.1 ~ 0.25
Large > 0.25
• High turbulence level cause extreme loading on
•
•
wind turbine components.
Turbulent locations will severely limit the lifetime
of Wind turbines and maximum the chance of
their catastrophic failures.
Standard deviation used for turbulence
Turbulence intensity = standard deviation of wind
speed/ mean wind speed
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Standard deviation of wind speed calculation (σ)
•A number that indicates how much wind speed changes
above or below the mean
•Example :For set of data v1 =6 m/s
n1= 19 times
v2 =7m/s
n2= 54 times
v3=8 m/s
n3= 42 times
Total Number of times occurrence (n) = 115
mean wind speed = (n1xv1 + n2xv2 + n3xv3)/n =
(19x6 +54x7 + 42x8)/ 115 = 7.2 m/s
σ2 =1/(n-1){(n1xv1^2 + n2xv2^2 + n3xv3^2) – 1/n (n1xv1
+n2xv2 +n3xv3)^2} =1/114 {(19x(6)2+54x(7)2 +42(8)2 –
(1/115)(19x6 + 54x7 +42x8)2} = 0.495 m2/s2
σ = 0.703 m/s
Turbulence intensity = standard deviation of wind speed/ mean
wind speed = 0.703 / 7.2 = 0.097
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Once this assessment is
completed, an accurate
picture of wind resource at
the site should be clear
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Site Ranking Criteria
Note that the maximum possible score for each criterion
is not the same. The differences reflect the relative
importance of the criteria.
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Micrositing
Micrositing is used to position one or
more wind turbines within a given
land area to maximize the overall
energy output of the wind plant.
One km2 of the windy land can host 5
– 7 MW of potential installed capacity.
100 MW wind farm needs (15-20 km2)
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Total power input
P/A= 0.5xxV3
Usable power
P/A= 0.5xxV3x 16/27
Turbine power
P/A= 0.5xxV3x 16/27x
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The distances between the turbines
have a strong effect on the energy
output of the wind park.
This effect is described by the park
efficiency the relation between :(the output of the park) / (the output
of the same number of stand-alone
turbines)
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Wind turbines are typically arranged
in rows perpendicular to prevailing
winds.
If the wind is consistently from one
direction then within-row spacing is
less and row-to-row spacing is
greater.
Within rows the spacing can vary
from 1.5 to 5 times the rotor
diameter.
Row-to-row distances typically vary
from 10 to 20 times the rotor
diameter.
For sites that have energetic winds
from multiple directions, the row-torow spacing and within row spacing
are similar.
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Typical array losses
for a wind farm are
2~4 %.
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•Avoid area of steep slope
The wind on steep slopes
tends to be turbulent.
The construction costs are
greatly increased.
•On hill tops, set the turbines
back from edge to avoid impacts
of the vertical component of the
wind.
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The bottle-neck effect between two elevations
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Highest elevation within a given area
High elevation is good and typically means
increased wind power
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Variation of wind speed with height
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Wind Speeds can be adjusted to another
height using the power law equation :
v2=v1(z2/z1)∝
V2 = the unknown speed at height Z2
v1 = the known wind speed at the
measurement height z1
∝ = the wind shear factor. it changes with
different roughness, often assumed 0.14 over
flat open terrain but can increase to 0.25 for
area with forest or taller buildings.
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Logarithmic Law
This law takes into account the surface
roughness of the surrounding terrain

ln
V

2 
V

ln
1

Z2 

Zo 
Z1 

Zo 
Zo (Roughness Lengths)
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zo
Zo (Roughness Lengths) is the height above ground
level where the wind speed is theoretically Zero
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How to increase the wind
turbine energy production
To increase the energy production of a wind farm of a
specific design, there are two possibilities available:
1. Position the wind turbine at a greater height above
ground. This option involves a wind turbine price
increase. It is therefore necessary to study whether
the increased energy production compensates the
extra price.
2. Optimise the wind farm design by re-locating
turbines or removing the ones that produce less.
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720000
Row 4
3200
3100
719000
Red Belt Northing [m]
721000
Detailed wind resources
at Zafarana
Row 3
3000
2900
718000
Row 2
2800
2700
Row 1
2600
769000
770000
771000
772000
773000
774000
Red Belt Easting [m]
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Please don’t hesitate to contact me for any question
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e-mail : ashour_2am@yahoo.com
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