WIND ENERGY ASSESSMENT

1. WIND ENERGY ASSESSMENT Khaled Daoud Wind Energy Division National Energy Research Center March 29, 2012

2. ENERGY RESOURCES The World’s Energy Resources Are Limited! Conventional Energy Resources • Oil • Coal • Natural Gas March 29, 2012

3. Renewable Energy Sources Wind Solar Renewable Energy Sources Water Geothermal Biomass Biogas March 29, 2012

4. SOLAR Geothermal Wind T Distribution Lines Transformer Biomass Water Biogas Renewable Energy Sources G Generator Your Home All renewable energy, ultimately come from the sun. March 29, 2012

5. Why Renewable Energy? The growth of energy demand Fast depletion of fossil fuel. Global environmental problems. 5 March 29, 2012

6. RENEWABLE ENERGY • Renewable energy resources may be used directly Or indirectly to create other more convenient forms of energy. • Examples of direct use are solar ovens, geothermal heating, and water heating and water pumping by windmills. • Examples of indirect use which require energy harvesting are electricity generation through wind turbines or photovoltaic cells, or production of fuels March 29, 2012

7. Wind Energy Resource • Wind energy is a sub-product of solar energy • Earth receives 1.74 x 10 17 W of solar energy - 2% of it is transformed to winds • Wind energy is the kinetic energy of the moving winds March 29, 2012

8. Wind Energy Resource • Reason: unevenly radiation of earth surface by the sun • The regions around equator, at 0° latitude, are heated more by the sun than the rest of the globe March 29, 2012

9. Wind Energy Resource • Hot air is lighter than cold and will rise into the sky until it reaches approximately 10 km altitude and will spread to the North and the South. If the globe did not rotate, the air would simply arrive at the North Pole and the South Pole, sink down, and return to the equator March 29, 2012

10. Wind Energy Resource The Coriolis force • Due to the earth rotation, any movement on the Northern hemisphere is diverted to the right (left in the southern) if we look at it from our own position on the ground. • Named after the French mathematician GustaveGaspardCoriolis 1792-1843 March 29, 2012

11. Wind Energy Resource Global winds and Coriolis force • The wind rises from the equator and moves north and south in the higher layers of the atmosphere. • Around 30° latitude in both hemispheres the Coriolis force prevents the air from moving much further. At this latitude there is a high pressure area, as the air begins sinking down again. • As the wind rises from the equator there will be a low pressure area close to ground level attracting winds from the north and south. • At the poles, there will be high pressure due to the cooling of the air. March 29, 2012

12. Wind Energy Resource • The geostrophic wind • The global winds are the geostrophic winds. They are largely driven by temperature (pressure) differences and are not very much influenced by the surface of the earth. Geostrophic winds are found at altitudes above 1 km above ground level. • Surface winds • Winds are very much influenced by the ground surface at altitudes up to 100 metres. The wind will be slowed down by the earth's surface roughness and obstacles. Wind directions near the surface will be different from the direction of the geostrophic wind because of the earth's rotation (i.e. Coriolis force). When dealing with wind energy, we are concerned with surface winds, and how to calculate the usable energy content of the wind. March 29, 2012

13. Wind Energy Resource Surface Winds: Sea Breeze • Land masses are heated by the sun more quickly than the sea during daytime. The air rises, flows out to the sea, and creates a low pressure at ground level which attracts the cool air from the sea. • At nightfall there is often a period of calm when land and sea temperatures are equal. Monsoon March 29, 2012

14. Wind Energy Resource Surface Winds: Land Breeze • At night the wind blows in the opposite direction. • The land breeze at night generally has lower wind speeds, because the temperature difference between land and sea is smaller at night. The monsoon known from South-East Asia is in reality a large-scale form of the sea breeze and land breeze, varying in its direction between seasons March 29, 2012

15. Wind Energy Resource Surface Winds: Mountain Winds • They originate on south-facing slopes (north-facing in the southern hemisphere). When the slopes and the neighbouring air are heated the air ascends towards the top following the surface of the slope. At night the wind direction is reversed. • Foehn in the Alps in Europe, • Chinook in the Rocky Mountains • Zonda in the Andes. March 29, 2012

16. Wind Energy Resource Local winds: • Mistral flowing down the Rhone valley into the Mediterranean Sea, • Scirocco, a southerly wind from Sahara blowing into the Mediterranean sea. March 29, 2012

17. Wind Energy Resource Wind systems in the Mediterranean sea region March 29, 2012

18. Wind Energy Resource Atmospheric boundary layer • At 1 km above ground level, the wind is not influenced by the surface of the earth at all (geostrophic winds). • In the lower layers of the atmosphere, however, wind speeds are affected by the friction against the surface of the earth. March 29, 2012

19. Wind Energy Resource • Friction is created due to the roughness of the terrain and the influence of obstacles • Forests and large cities slow the wind down considerably • Concrete runways in airports slow the wind down a little. • Long grass and shrubs and bushes slow the wind down considerably. • Water surfaces are even smoother have even less influence on the wind March 29, 2012

20. Wind Energy Resource Effect of Obstacles March 29, 2012

21. Wind Energy Resource Effect of Obstacles March 29, 2012

22. Wind Energy Resource Affecting the wind: Temperature Roughness Obstacles Orography sea beach grass trees hills woods buildings cities valleys & mountains Meteorology Thermals wind from sea March 29, 2012

23. Wind Resource Assessment 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. 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 March 29, 2012

24. Wind Resource Assessment * 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 March 29, 2012

25. Wind Resource Assessment Without wind resource , no wind project will even be viable. Wind Resources assessments are the cornerstone of identifying and mitigating risks and for realizing the potential rewards from a project. March 29, 2012

26. Wind Resource Assessment Site Visits and Evaluations • Visits should be conducted to all suitable areas with the main goals of verifying site conditions. • The evaluator should use the following:- • The site topographical map • A Global Positioning System (GPS) • A Camera • A compass March 29, 2012

27. Wind Resource Assessment • Preliminary Area Identification based on information such as : • previous wind data, • Topography, • Flagged trees ..etc. • A new wind measurement sites can be selected. March 29, 2012

28. Wind Resource Assessment Prevailing Wind Direction Important to check direction when setting up instrument March 29, 2012

29. Wind Resource Assessment 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. March 29, 2012

30. Wind Resource Assessment • 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 March 29, 2012

31. Wind Resource Assessment Frequency Distribution • The basic tool for estimating energy production. • It shows the % of time that the wind blowing at certain speed. • The wind speed are binned, meaning that wind speed between • 0 - 1 m/s are binned as 1 m/s, • 1 - 2 m/s are binned as 2 m/s, • and so on. March 29, 2012

32. Wind Resource Assessment X Energy Production Frequency Distribution Power Curve X To assess a site’s wind power production potential, the wind speed frequency distribution must be multiplied by a representative wind turbine power curve. March 29, 2012

33. Wind Resource Assessment Wind rose is a useful tool to know the wind direction. It is a valuable tool for project layout and micro-siting March 29, 2012

34. Wind Resource Assessment • 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. March 29, 2012

35. Wind Resource Assessment Wind Power Class Table March 29, 2012

36. Wind Resource Assessment Once this assessment is completed, an accurate picture of wind resource at the site should be clear March 29, 2012

37. Thank You March 29, 2012