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” وهو الذى أرسل الرياح بشراً بين يدى رحمته ، وأنزلنا من السماء ماء

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” وهو الذى أرسل الرياح بشراً بين يدى رحمته ، وأنزلنا من السماء ماءً طهوراً ” الفرقان - 48. 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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” وهو الذى أرسل الرياح بشراً بين يدى رحمته ، وأنزلنا من السماء ماءً طهوراً ” الفرقان - 48

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,


Wind Resource Assessment ProgramPrepared byEng. Ashour Abdelsalam MoussaWind Energy Dep., New & Renewable Energy Authority (NREA)

the world s energy resources are limited
The World’s Energy Resources Are Limited!

COAL - 100 YRS.


GAS - 30 YRS

uranium - ???

Human Beings ???


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



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

March 2010 - Page 6


World Market Update 2009

March 2010 - Page 7

why assess wind resource
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.

  • 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


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.


Without wind resource,

no wind project will even be viable.


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.


Use vegetation to know wind direction and intensity

االساق عمودية والاغصان متحركة

الساق عمودية والاغصان ثابتة

ميل خفيف للاغصان

ميل متوسط

ميل كامل والساق عمودية على الارض

ميل جزئى للساق والاغصان

ميل شبه كامل للساق والاغصان

الساق والاغصان كالسجادة

prevailing wind direction
Prevailing Wind Direction

Important to check direction when setting up instrument

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

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.


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.


Wind rose is a useful tool to know the wind blows.

It is a valuable tool for project layout and micro-siting

wind power density w m 2
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.

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


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
Once this assessment is completed, an accurate picture of wind resource at the site should be clear

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.


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)


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


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)







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-to-row spacing and within row spacing are similar.

Typical array losses for a wind farm are 2~4 %.


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.
highest elevation within a given area
Highest elevation within a given area

High elevation is good and typically means increased wind power

Wind Speeds can be adjusted to another height using the power law equation :


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.


Logarithmic Law

This law takes into account the surface roughness of the surrounding terrain

Zo (Roughness Lengths)



Zo (Roughness Lengths) is the height above ground level where the wind speed is theoretically Zero


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:
  • 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.
  • Optimise the wind farm design by re-locating turbines or removing the ones that produce less.