Wind Energy and Tidal Energy, Module 4

Wind Energy : Properties of wind, availability of wind energy in India, wind velocity and power from wind; major problems associated with wind power, wind machines; Types of
wind machines and their characteristics, horizontal and vertical axis wind mills, elementary
design principles; coefficient of performance of a wind mill rotor, aerodynamic considerations of wind mill design, numerical examples.
Tidal Power: Tides and waves as energy suppliers and their mechanics; fundamental characteristics of tidal power, harnessing tidal energy, limitations.

1. 7/23/2021 Dr. Ramesh B T 1 WIND ENERGY Dr. Ramesh B T Asst. Professor Dept. of Mechanical Engineering JIT, Davanagere Email: [email protected]

2. 7/23/2021 Dr. Ramesh B T 2 Classification of methods for solar energy utilisation:

3. 7/23/2021 Dr. Ramesh B T 3 The first known historical reference to a windmill is from Hero of Alexandria, in his work Pneumatics ( Woodcroft , 1851). Hero was believed to have lived either in the 1st century B.C. or The 1st century A.D. His Pneumatics describes a device which provides air to an organ by Means of a windmill. An illustration which accompanies Hero’s description is shown in Figur . There has been some debate about whether such a windmill actually existed and whether the Illustration actually accompanied the original documents. See Shepherd (1990) and Drachman (1961). One of the primary scholars on the subject, however, H. P.Vowles , (Vowels, 1932) does Consider Hero.s description to be plausible.

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6. The Coriolis Effect Air pressure differences cause the movement of air Air moving parallel to the ground is called wind Air moving up or down is called a current 7/23/2021 Dr. Ramesh B T 6

7. Air generally moves from the poles to the equator, this is because air flows from high pressure to low pressure High pressure forms when cold air sinks (at the poles) Low pressure forms when warm air rises (at the equator) But the air doesn’t flow in a straight line Causes air to move in a curved path It is caused by the Earth spinning on its axis The Earth spins fastest at the equator, and slowest near the poles As air moves from the equator to the pole, it will travel east faster than the land beneath it causing the air to follow a curved path 7/23/2021 Dr. Ramesh B T 7

8. So the coriolis effect causes wind flowing from high pressure to low pressure to curve as the wind moves In the Northern Hemisphere , the coriolis effect causes things to curve to the Right of the Observer In the Southern Hemisphere , the coriolis effect causes things to curve to the Left of the observer 7/23/2021 Dr. Ramesh B T 8

9. Wind Winds are created because of the uneven heating the Earth As discussed before, air moves from high pressure to low pressure Areas that are warmer are low pressure areas, so wind blows toward low pressure Areas that are colder are high pressure areas, so wind blows away from high pressure There are two types of winds Planetary (or global) local 7/23/2021 Dr. Ramesh B T 9

10. Planetary wind These winds blow across the entire planet They generally blow at the same speed and direction Some are high in the atmosphere and you cannot feel them on the ground Each hemisphere contains 3 wind belts that divide up the planetary winds Trade winds, Westerlies , and Easterlies 7/23/2021 Dr. Ramesh B T 10

11. Global Wind Patterns 7/23/2021 Dr. Ramesh B T 11

12. Local Winds These winds blow over small areas Unlike planetary winds, local winds can change speed and direct frequently These are the winds we feel on the ground They are influenced by local conditions and local temperature variations 7/23/2021 Dr. Ramesh B T 12

13. Local Wind cont. Land and sea breezes During the day, the land heats up faster than the water, so a breeze will blow from the sea to the land, called a sea breeze At night, the land will cool off faster than the water, so the cool land air will flow toward the warmer ocean water air, creating a land breeze , where the wind blows from the land to the sea 7/23/2021 Dr. Ramesh B T 13

14. Mountain and Valley Breezes During the day, the valley heats up, so the warm less dense air flows up the mountain, creating a valley breeze At night, the mountain will cool off faster than the valley, so the cool mountain air descends because it is more dense, creating a mountain breeze 7/23/2021 Dr. Ramesh B T 14

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16. 7/23/2021 Dr. Ramesh B T 16 Wind Energy In India India is the world’s fourth country by cumulative wind energy capacity – currently at 38GW Renewable energy is growing rapidly in India. With an installed capacity of 13.2 GW, renewable energy sources (excluding large hydro) currently account for 9% of India's overall power generation capacity. By 2012, the Indian government is planning to add an extra 14 GW of renewable sources. In its 10th Five Year Plan, the Indian government had set itself a target of adding 3.5 GW of renewable energy sources to the generation mix. In reality , however, nearly double that figure was achieved. In this period, more than 5.4 GW of wind energy was added to the generation mix, as well as 1.3 GW from other RE sources The total power in2008-2012 was increased to 14 GW, 10.5 GW of which to be new wind generation capacity . The Indian Ministry of New and Renewable Energy (MNRE) estimates that there is a potential of around 90,000 MW for the country, including 48,561 MW of wind power, 14,294 MW of small hydro power and 26,367 MW of biomass In addition, the potential for solar energy is estimated for most parts of the country at around 20 MW per square kilometer of open, shadow free area covered with 657 GW of installed capacity.

17. 7/23/2021 Dr. Ramesh B T 17 The total potential for wind power in India was first estimated by the Centre for Wind Energy Technology (C-WET) at around 45 GW, and was recently increased to 48.5 GW. This figure was also adopted by the government as the official estimate . The C-WET study was based on a comprehensive wind mapping exercise initiated by MNRE, which established a country-wide network of 105O wind monitoring and wind mapping stations in 25 Indian States. This effort made it possible to assess the national wind potential and identify suitable areas for harnessing wind power for commercial use, and 216 suitable sites have been identified. However, the wind measurements were carried out at lower hub heights and did not take into account technological innovation and improvements and repowering of old turbines to replace them with bigger ones At heights of 55-65 meters, the Indian Wind Turbine Manufacturers Association (IWTMA) estimates that the potential for wind development in India is around 65-70 GW. The World Institute for Sustainable Energy, India (WISE) considers that with larger turbines, greater land availability and expanded resource exploration, the potential could be as big as 100 GW .

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19. 7/23/2021 Dr. Ramesh B T 19 Advantages of Wind Power Wind power is cost-effective Wind creates jobs Wind enables industry growth and competitiveness .  It's a clean fuel source . Wind is a domestic source of energy . It's sustainable Wind turbines can be built on existing farms or ranches Wind energy can be used to power vehicles Wind power can be used to pump water

20. 7/23/2021 Dr. Ramesh B T 20 CHALLENGES OF WIND POWER The wind is inconsistent Wind power must still compete with conventional generation sources on a cost basis.  Good land-based wind sites are often located in remote locations, far from cities where the electricity is needed.  Wind resource development might not be the most profitable use of the land Turbines might cause noise and aesthetic pollution Wind plants can impact local wildlife Wind turbines are suited to a particular region Wind turbines can be a safety hazard Installation can take up a significant portion of land  Wind turbines have a visual impact

21. 7/23/2021 Dr. Ramesh B T 21 Wind Turbine A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity , the device may be called a wind generator or wind charger .

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24. 7/23/2021 Dr. Ramesh B T 24 The graph shows the combined effect of wind speed and rotor diameter variation Power Coefficient The fraction of the free-flow wind power that can be extracted by the rotor is called the power co-efficient; Thus, Power Coefficient = Power of wind rotor / Power available in the wind Where, power available is calculated from the air density, rotor diameter and free wind speed as discussed earlier. The maximum theoretical power coefficient is equal to 16/27 or 0.593. This value cannot be exceeded by a rotor in free-flow wind-stream.

25. 7/23/2021 Dr. Ramesh B T 25 Expression For Maximum Power In Wind  As discussed earlier, that the total power can not converted to mechanical power. Consider a horizontal-axis, propeller-type wind mill, henceforth to be called a wind turbine, which is the, most common type today. Assume that the wheel such a turbine has a thickness ‘ ab ’ shown in Fig .

26. 7/23/2021 Dr. Ramesh B T 26 For optimum exit velocity ‘ V e,opt ’, that results in maximum power ‘ P max ’, which can be obtained by differentiating ‘P’ with respect to ‘V e ’, and equating the derivative to zero, i.e.,

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28. Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Vertical axis wind turbines have the main rotor shaft arranged vertically. Key advantages of this arrangement are that the turbine does not need to be pointed into the wind to be effective. This is an advantage on sites where the wind direction is highly variable, for example when integrated into buildings. 7/23/2021 Dr. Ramesh B T 28

29. 7/23/2021 Dr. Ramesh B T 29 Types of VAWM Darries Rotor Savonius Wind turbine Twisted Savonius Wind turbine Types of HAWT https://youtu.be/qSWm_nprfqE

30. 7/23/2021 Dr. Ramesh B T 30 Aerodynamics of wind turbines Aerodynamics deals with the motion of air or other gaseous fluids and the forces acting on bodies moving through them. Aerodynamic theories developed for airplanes and helicopters were adopted for defining the performance of wind turbines. However, now, theories are specifically formulated for wind turbines which are further refined and reinforced with the help of experimental techniques. The  angle of attack   is the angle between the reference line of a body and relative wind.  Chord Line: A straight line joining the leading edge of a propeller  blade  with its trailing edge.

31. 7/23/2021 Dr. Ramesh B T 31 Lift/Drag Forces Experienced by Turbine Blades https://www.youtube.com/watch?v=uK7ubLWvnbE

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34. 7/23/2021 Dr. Ramesh B T 34 The  Betz limit  is the theoretical maximum  efficiency  for a  wind turbine , conjectured by German physicist Albert Betz in 1919 .  Betz concluded that this value is  59.3% , meaning that at most only 59.3% of the  kinetic energy  from  wind  can be used to spin the turbine and generate  electricity . In reality, turbines cannot reach the Betz limit, and common efficiencies are in the 35-45% range. https://www.youtube.com/watch?v=9NwnvA0KS1k

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37. 7/23/2021 Dr. Ramesh B T 37 Design Consideration

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42. 7/23/2021 Dr. Ramesh B T 42 3) Solidity ( : The solidity factor for wind turbine is defined as a ratio of blade area to the circumference of the rotor. Where 'n' is the number of blades used and 'b' is the width of blade and 'D' is diameter of the blade. This ratio ( ) determines the quantity of blade material required to intercept a certain wind area.  

43. 7/23/2021 Dr. Ramesh B T 43 Considerations for selection of site for wind energy conversion systems :   Following factors should be given due considerations while selecting the site for wind energy conversion systems :   Availability of anemometry data .( an instrument for measuring and indicating the force or speed and sometimes direction of the wind .) High annual average wind speed. Availability of wind curve at the proposed site. Wind structure at the proposed site. Altitude of the proposed site. Terrain and its aerodynamic. Local ecology. Distance to roads or railways. Nearness of site to local centre /users. Favourable land cost. Nature of ground.  

44. 7/23/2021 Dr. Ramesh B T 44 Numerical on Wind power

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48. 7/23/2021 Dr. Ramesh B T 48 Tidal and waves Energy

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50. The Long History of Tidal Energy Tidal power buildings were built as early as the 9 th Century throughout Europe. This building was built in Ohalo, Portugal circa 1280. 7/23/2021 Dr. Ramesh B T 50

51. 7/23/2021 Dr. Ramesh B T 51 Tidal and waves Energy Tides are produced by the pull of gravity from the Moon as well as the spin of the Earth. There is a lot of energy in the movement of that much water. Tidal energy is energy produced by the tides of the ocean . The first wave power plant in the world opened in 2008 at the Farm in Portugal. The idea of using tidal power for electricity is fairly recent, but the costs have been too high to make it a major energy source. Recent technological advances have shown that it could become a competitive and viable source.

52. 7/23/2021 Dr. Ramesh B T 52 Types of Tide Diurnal Tide Semi Diurnal Tide Mixed Tide

53. 7/23/2021 Dr. Ramesh B T 53 Tidal Gauge A tide gauge is  a device for measuring the change in sea level relative to a vertical datum .

54. Following figures show how the gravitational forces and centrifugal forces create tides. 7/23/2021 Dr. Ramesh B T 54

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56. 7/23/2021 Dr. Ramesh B T 56 Earth on its axis and the Moon in its orbit both revolve eastward and these causes the tides to occur 50 minutes later each day.

57. 7/23/2021 Dr. Ramesh B T 57 Latitude of the tidal bulges is determined by the declination, the angle between Earth‘s axis and the lunar and solar orbital plane . Spring tides occur when Earth, Moon and Sun are aligned in a straight line and the tidal bulges display constructive interference, producing very high, high tides and very low, low tides. Spring tides coincide with the new and full moon. Neap tides occur when the Earth, Moon and Sun are aligned forming a right angle and tidal bulges displaying destructive interference , producing low high tides and high low tides. • Neap tides coincide with the first and last quarter moon.

58. 7/23/2021 Dr. Ramesh B T 58 Basic Principle of Tidal Power

59. Energy calculation Energy available from a barrage is dependent on the volume of water The potential energy contained in a volume of water is: E = 1 2 A ρ g ℎ 2 where, h is the vertical tidal range, A is the horizontal area of the barrage basin, ρ is the density of water, g is acceleration due to gravity 7/23/2021 Dr. Ramesh B T 59

60. 7/23/2021 Dr. Ramesh B T 60 Components of Tidal power plant

61. 7/23/2021 Dr. Ramesh B T 61 DAM ( Barrage ): The barrages store water behind them. The barrages should provide channels for the turbines, gates and locks. The tidal power barrages should be of shorter length. The length should be less than resonant length of tidal waves. The tidal barrages require sites where a sufficiently high tidal range is available. The barrages require flat bottom. POWER HOUSE: Large size turbines are needed to because of small head available . Hence power house will also be large structure. The types of turbines used are ( i )Bulb type: In systems with a bulb turbine, water flows around the turbine, making access for maintenance difficult, as the water must be prevented from flowing past the turbine. (ii) Rim type: Rim turbines reduce these problems as the generator is mounted in the barrage , at right angles to the turbine blades. Unfortunately, it is difficult to regulate the performance of these turbines and it is unsuitable for use in pumping. (iii)Tubular type: Tubular turbines have been proposed for use some UK projects. In this configuration , the blades are connected to a long shaft and orientated at an angle so that the generator is sitting on top of the barrage.

62. 7/23/2021 Dr. Ramesh B T 62 https://youtu.be/VkTRcTyDSyk

63. 7/23/2021 Dr. Ramesh B T 63 Classification of Tidal power Plant

64. 7/23/2021 Dr. Ramesh B T 64 Single Basin Tidal System: • The simplest generating system for tidal plants, known as an ebb generating system, involves a dam, known as a barrage across an estuary . • Sluice gates on the barrage allow the tidal basin to fill on the incoming high tides and to exit through the turbine system on the outgoing tide (known as the ebb tide).

65. 7/23/2021 Dr. Ramesh B T 65 Double basin Tidal System: another form of energy barrage configuration is that of the dual basin type. With two basins, one is filled at high tide and the other is emptied at low tide. Turbines are placed between the basins. Two-basin schemes offer advantages over normal schemes in that generation time can be adjusted with high flexibility and it is also possible to generate almost continuously. In normal estuarine situations , however, two-basin schemes are very expensive to construct due to the cost of the extra length of barrage. There are some favorable geographies , however, which are well suited to this type of scheme.

66. 7/23/2021 Dr. Ramesh B T 66 Some advantages of tidal energy are: Environment-friendly A highly predictable energy source High energy density Operational and maintenance costs are low An inexhaustible source of energy Some of the disadvantages of tidal energy are: High tidal power plant construction costs Negative influence on marine life forms Location limits The variable intensity of sea waves

67. 7/23/2021 Dr. Ramesh B T 67 Thank you