Wind Power and Energy Harnessing Systems

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Wind Power and Energy Harnessing Systems:

Wind Power and Energy Harnessing Systems

Submitted By : Group IV :

Submitted By : Group IV Rohan Nayyar – 137 2

Introduction:

Introduction All renewable energy (except tidal and geothermal power),ultimately comes from the sun The earth receives 1.74 x 10 17 watts of power (per hour) from the sun About one or 2 percent of this energy is converted to wind energy (which is about 50-100 times more than the energy converted to biomass by all plants on earth Differential heating of the earth’s surface and atmosphere induces vertical and horizontal air currents that are affected by the earth’s rotation and contours of the land  WIND. ~ e.g.: Land Sea Breeze Cycle

Slide 4:

The Amalgamation of the Renewable Resources 4

Contd.:

Contd. Winds are influenced by the ground surface to altitudes up to 100 meters slowed by the surface roughness and obstacles. A wind turbine obtains its power input by converting the force of the wind into a torque (turning force) acting on the rotor blades. The amount of energy which the wind transfers to the rotor depends on the density of the air, the rotor area, and the wind speed. The kinetic energy of a moving body is proportional to its mass (or weight). The kinetic energy in the wind thus depends on the density of the air, i.e. its mass per unit of volume. In other words, the "heavier" the air, the more energy is received by the turbine. at 15° Celsius air weighs about 1.225 kg per cubic meter, but the density decreases slightly with increasing humidity.

The Need for Wind Turbines:

The Need for Wind Turbines A wind turbine is old technology applied to meet new challenges. We need to adapt and use every means at our disposal to combat global warming and carbon dioxide build up, yet still provide energy for our modern (lavish) lifestyles. Wind is a renewable energy source. Mills provides means for a non-polluting energy harvest as it does not produce any green house effect gases. Wind energy system operations do not generate air or water emissions and do not produce hazardous waste. Nor do they deplete natural resources such as coal, oil, or gas, or cause environmental damage through resource extraction and transportation, or require significant amounts of water during operation The need for Wind Turbines is hence Immediate and Essential . 6

Potential Of Wind Turbines :

Potential Of Wind Turbines The Indian Scenario The Indian wind energy sector has an installed capacity of 10,891.00 MW (as on October 31, 2009). In terms of wind power installed capacity, India is ranked 5th in the World. Wind in India are influenced by the strong south-west summer monsoon, which starts in May-June, when cool, humid air moves towards the land and the weaker north-east winter monsoon, which starts in October, when cool, dry sir moves towards the ocean. During the period March to August, the winds are uniformly strong over the whole Indian Peninsula, except the eastern peninsular coast. 7

Slide 8:

The development of wind power in India began in the 1990s, and has significantly increased in the last few years. It is estimated that 6,000 MW of additional wind power capacity will be installed in India by 2012. Wind power accounts for 6% of India's total installed power capacity, and it generates 1.6% of the country's power. Wind farm in Muppandal, Tamil Nadu 8

Utilization :

Utilization 9

State-Wise Cumulative Wind Generation Data in (BU) (As on 30.11.2008) :

State-Wise Cumulative Wind Generation Data in (BU) (As on 30.11.2008) 10

Potential Of Wind Turbines :

Potential Of Wind Turbines B) The International Scenario Wind power available in the atmosphere is much greater than current world energy consumption. A comprehensive study in 2005 found the potential of wind power on land and near-shore to be 72 TW, equivalent to 54,000 MToE(million tons of oil equivalent) per year, or over five times the world's current energy use in all forms. The study assumes six 1.5 megawatt, 77 m diameter turbines per square kilometer on roughly 13% of the total global land area (though that land would also be available for other compatible uses such as farming). 11

Slide 12:

The practical limit to exploitation of wind power is set by economic and environmental factors, since the resource available is far larger than any practical means to develop it. With thousands of wind turbines operating, with total capacity of 157,899 MW . World wind generation capacity more than quadrupled between 2000 and 2006, doubling about every three years In recent years, the world has added more wind energy to its grid, with a growth in power capacity of 45% in 2007

Slide 13:

World Wide Installed Capacity of Wind Turbines (1 st 10) 13

Environmental Effect Of Wind Energy:

Environmental Effect Of Wind Energy Compared to the environmental effects of traditional energy sources, the environmental effects of wind power are relatively minor. Wind power consumes no fuel , and emits no air pollution , unlike fossil fuel power sources. The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months of operation Noise can be an important disadvantage of wind turbines, especially when building the wind turbines very close to urban environments. Wind turbines may produce sounds that reduces the mood of people, may cause sleeping problems. In addition, some marine and land-based organisms are also affected by the noise. 14

Types of Wind Mills:

Types of Wind Mills

CLASSIFICATION:

CLASSIFICATION Based on the axis of rotation/orientation: 1. Horizontal axis wind turbines 2.Vertical axis wind turbines According to the size as determined by their power output 1. Small scale( up to 2kw) 2.Medium scale or medium sized machines( 2-100kw) 3. Large scale(>100kw) 16

Slide 17:

According to the type of power output: 1. DC output 2. AC output Based on the rotational speed of the turbines 1. Constant speed with variable pitch blades 2. Nearly constant speed with fixed pitch blades and 3. Variable speed with fixed pitch blades 17

Orientation:

Orientation Turbines can be categorized into two overarching classes based on the orientation of the rotor Vertical Axis Horizontal Axis 18

Vertical Axis Turbines:

Vertical Axis Turbines Advantages Omni directional Accepts wind from any angle Components can be mounted at ground level Ease of service Lighter weight towers Can theoretically use less materials to capture the same amount of wind Disadvantages Rotors generally near ground where wind poorer Centrifugal force stresses blades Poor self-starting capabilities Requires support at top of turbine rotor Requires entire rotor to be removed to replace bearings Overall poor performance and reliability Have never been commercially successful 19

Lift vs. Drag VAWTs:

Lift vs. Drag VAWTs Lift Device “ Darrieus ” Low solidity, aerofoil blades More efficient than drag device Drag Device “ Savonius ” High solidity, cup shapes are pushed by the wind At best can capture only 15% of wind energy 20

Lift & Drag Forces:

Lift & Drag Forces The Lift Force is perpendicular to the direction of motion. We want to make this force BIG . The Drag Force is parallel to the direction of motion. We want to make this force small . α = low α = medium <10 degrees α = High Stall!! 21

VAWT’s have not been commercially successful, yet…:

VAWT’s have not been commercially successful, yet… Every few years a new company comes along promising a revolutionary breakthrough in wind turbine design that is low cost, outperforms anything else on the market, and overcomes all of the previous problems with VAWT’s. They can also usually be installed on a roof or in a city where wind is poor . WindStor Mag-Wind Wind Tree Wind Wandler 22

Horizontal Axis Wind Turbines:

Horizontal Axis Wind Turbines Rotors are usually Up-wind of tower Some machines have down-wind rotors, but only commercially available ones are small turbines 23

Number of Blades – One:

Number of Blades – One Rotor must move more rapidly to capture same amount of wind Gearbox ratio reduced Added weight of counterbalance negates some benefits of lighter design Higher speed means more noise, visual, and wildlife impacts Blades easier to install because entire rotor can be assembled on ground Captures 10% less energy than two blade design Ultimately provide no cost savings 24

Slide 25:

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Number of Blades - Two:

Number of Blades - Two Advantages & disadvantages similar to one blade Need teetering hub and or shock absorbers because of gyroscopic imbalances Capture 5% less energy than three blade designs 26

Number of Blades - Three:

Number of Blades - Three Balance of gyroscopic forces Slower rotation increases gearbox & transmission costs More aesthetic, less noise, fewer bird strikes 27

Slide 28:

SAIL TYPE AND DUTCH TYPE 28

Slide 29:

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Active vs. Passive Yaw:

Active vs. Passive Yaw Active Yaw (all medium & large turbines produced today, & some small turbines from Europe) Anemometer on nacelle tells controller which way to point rotor into the wind Yaw drive turns gears to point rotor into wind Passive Yaw (Most small turbines) Wind forces alone direct rotor Tail vanes Downwind turbines 30

Slide 31:

Control Methods Some of the different types of control methods used are as follows : Pitch Adjustment Yaw Adjustment Electrical Systems Adjustment 31

Slide 32:

Pitch Adjustment The purpose of pitch control is to maintain the optimum blade angle to achieve certain rotor speeds or power output. We can use pitch adjustment to stall and furl, two methods of pitch control. By Stalling a wind turbine, we increase the angle of attack, which causes the flat side of the blade to face further into the wind. Furling decreases the angle of attack, causing the edge of the blade to face the oncoming wind. Pitch angle adjustment is the most effective way to limit output power by changing aerodynamic force on the blade at high wind speeds. 32

Slide 33:

Yaw Adjustment Yaw refers to the rotation of the entire wind turbine in the horizontal axis . Yaw control ensures that the turbine is constantly facing into the wind to maximize the effective rotor area and, as a result, power. Because wind direction can vary quickly, the turbine may misalign with the oncoming wind and cause power output losses . 33

Airfoil Nomenclature Wind turbines use the same aerodynamic principals as aircraft:

Airfoil Nomenclature W ind turbines use the same aerodynamic principals as aircraft 34

Twist & Taper:

Twist & Taper Speed through the air of a point on the blade changes with distance from hub Therefore, tip speed ratio varies as well To optimize angle of attack all along blade, it must twist from root to tip 35

Pitch Control vs. Stall Control:

Pitch Control vs. Stall Control Pitch Control Blades rotate out of the wind when wind speed becomes too great Stall Control Blades are at a fixed pitch that starts to stall when wind speed is too great Pitch can be adjusted for particular location’s wind regime Active Stall Control Many larger turbines today have active pitch control that turns the blades towards stall when wind speeds are too great 36

Slide 37:

Airfoil in Stall Stall arises due to separation of flow from airfoil Stall results in decreasing lift coefficient with increasing angle of attack Stall behavior complicated due to blade rotation 37

Betz Limit :

Betz Limit Betz Limit All wind power cannot be captured by rotor or air would be completely still behind rotor and not allow more wind to pass through. Theoretical limit of rotor efficiency is 59% Rotor Wake Rotor Disc 38

Slide 39:

Tip Speed Ratio Capacity Factor 39

Blade Composition :

Blade Composition Wood Strong, light weight, cheap, abundant, flexible Popular on do-it yourself turbines Solid plank Laminates Veneers Composites 40

Blade Composition :

Blade Composition 2. Metals Steel Heavy & Expensive Aluminum Lighter-weight and easy to work with Expensive Subject to metal fatigue 41

Slide 42:

Windmill Construction

Blade Construction Fiberglass:

Blade Construction Fiberglass Lightweight, strong, inexpensive, good fatigue characteristics Variety of manufacturing processes Cloth over frame Pultrusion Filament winding to produce spars Most modern large turbines use fiberglass 43

Hubs:

Hubs The hub holds the rotor together and transmits motion to nacelle Three important aspects How blades are attached Nearly all have cantilevered hubs (supported only at hub) Struts & Stays haven’t proved worthwhile Fixed or Variable Pitch Flexible or Rigid Attachment Most are rigid Some two bladed designs use teetering hubs 44

Drive Trains:

Drive Trains Drive Trains transfer power from rotor to the generator Direct Drive (no transmission) Quieter & more reliable Most small turbines Mechanical Transmission Can have parallel or planetary shafts Prone to failure due to very high stresses Most large turbines (except in Germany) Direct Drive Enercon E-70, 2.3 MW (right ) GE 2.3 MW (above) Multi-drive Clipper Liberty 2.5 MW (right ) 45

Towers:

Towers Monopole (Nearly all large turbines) Tubular Steel or Concrete Lattice (many Medium turbines) 20 ft. sections Guyed Lattice or monopole 3 guys minimum Tilt-up 4 guys Tilt-up monopole 46

Slide 47:

Basic Parts of a Wind Mill Though large in size, such wind turbines are still very simple with relatively few components. Such simplicity is essential if the wind turbine is to be kept operational through years of extreme conditions . 47

Slide 48:

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Slide 49:

Three turbine blades (1) make up the rotor (2). The pitch (3) of each blade can be changed (i.e. the blade can be rotated) to increase efficiency in low winds and to decrease efficiency (to protect the wind turbine) in very strong winds. In addition a brake (4) is fitted which can be set when dangerously strong winds are approaching or when the turbine is taken down for maintenance. The rotor is spun by the wind causing the low-speed shaft (5) to rotate. This rotation is then passed onto the high-speed shaft (12) via a gearbox (6) which accelerates the speed of rotation to the levels necessary to generate high voltage electricity with the generator (7). Everything is controlled via an electronic controller (8) which takes data inputs from an anemometer (9) which measures the speed of the wind, and a wind vane (10) which detects the direction of the wind. The nacelle (11) - the sealed unit at the top of the tower (15) - can then be automatically rotated to face into the wind with a yaw motor (14) turning the yaw drive (13). 49

Slide 50:

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Slide 51:

Wind Turbine Operation A wind turbine is a revolving machine that converts the kinetic energy from the wind into mechanical energy . This mechanical energy is then converted into electricity that is sent to a power grid. The turbine components responsible for these energy conversions are the rotor and the generator . The rotor is the area of the turbine that consists of both the turbine hub and blades. As wind strikes the turbine’s blades , the hub rotates due to aerodynamic forces . This rotation is then sent through the transmission system to decrease the revolutions per minute . The transmission system consists of the main bearing, high-speed shaft, gearbox, and low-speed shaft . The ratio of the gearbox determines the rotation division and the rotation speed that the generator sees. {For example, if the ratio of the gearbox is N to 1, then the generator sees the rotor speed divided by N. This rotation is finally sent to the generator for mechanical-to-electrical conversion} 51

Slide 52:

The above figure shows the major components of a wind turbine: Gearbox, Generator, Hub, Rotor, Low-speed Shaft, High-speed Shaft, and the Main Bearing. The purpose of the hub is to connect the blades’ servos that adjust the blade direction to the low-speed shaft . The rotor is the area of the turbine that consists of both the hub and blades. The components are all housed together in a structure called the Nacelle . 52

Slide 53:

The Power Curve Because Region I consists of low wind speeds and is below the rated turbine power, the turbine is run at the maximum efficiency to extract all power. In other words, the turbine controls with optimization in mind. Region II is a transition region mainly concerned with keeping rotor torque and noise low . Region III consists of high wind speeds and is at the rated turbine power. The turbine then controls with limitation of the generated power in mind when operating in this region. 53

Slide 54:

Electrical Systems Adjustment We can achieve this dynamic control with power electronics , or, more specifically, electronic converters that are coupled to the generator . The two types of generator control are Stator and Rotor . The Stator and Rotor are the stationary and non stationary parts of a generator , respectively. In each case, you disconnect the stator or rotor from the grid to change the synchronous speed of the generator independently of the voltage or frequency of the grid .. 54

Slide 55:

Electrical Systems Adjustment Control at low wind speeds is most effective by adjusting pitch angle and controlling the synchronous speed of the generator . 55

SITE SELECTION:

SITE SELECTION Wind is the fuel that drives a wind turbine and therefore the turbine needs to be placed where the wind is. No matter how efficient and well designed the turbine itself may be, if not placed in the right location, the turbine will be useless. Therefore, proper site selection is essential in building efficient wind farms

Slide 57:

1 . Reduced turbulence Wind turbines need air that moves uniformly in the same direction. Eddies and swirls, ‘turbulence’ in short, do not make good fuel for a wind turbine. The rotor cannot extract energy from turbulent wind, and the constantly changing wind direction due to turbulence causes excessive wear and premature failure of the turbine. This means that turbines need to be placed high enough to catch strong winds, and above turbulent air 57

Slide 58:

2 .Wind speed Power produced by a wind turbine is proportional to the cube of wind speed. Compared to ground level , wind speed is 20-25% greater at 10 m height and 30-60% greater at 60 m height. Therefore as the height of the tower on which the wind turbine is placed increases, the wind speed increases. But since the tower price increases quickly with height there is a limit to what is practical and affordable 58

Slide 59:

The quick-and-dirty rule of thumb for turbine height is a minimum of 10 meters (30 feet) plus the length of a turbine blade above the tallest obstacle (trees, house etc.) in a 150 meter (500 feet) radius, with a tower height of at least 19 meters (60 feet). If the obstacle is more solid than a few trees (for example a whole tree line) then even more distance than 500' is needed. 59

Slide 60:

Going beyond the rule of thumb , the airflow over any blunt obstruction, including a tree, tends to create a “bubble” of turbulent air of twice the height of the obstacle, extending 20 times the height of the obstacle behind it. Therefore the turbines are built far away from obstacles or higher up. 60

Slide 61:

When it comes to wind turbines, the bottom of a hill, valley, or ravine makes for a poor place to site a windmill. The wind tends to drop in speed at the bottom of a smooth hill, then speed up as it goes up the hill, reaching around twice the wind speed at the top of the hill. The figure below shows this 61

Slide 62:

For obstructions that are not smooth, such as a cliff (i.e. a sudden rise in the landscape) it gets trickier: Sharp edges create turbulence, as illustrated in the figure below. The airflow at the top of the cliff can be stronger than the average wind speed in the area, but close to the cliff’s edge it may also be very turbulent, making it a poor site for a turbine. If the turbine is to be placed on the cliff edge, a 60 feet high tower should be used to get above turbulent air 62

Other Factors Affecting Site Selection:

Other Factors Affecting Site Selection Transportation and road system that exists between the place where the turbines are manufactured and the site. Soil composition and presence of rock determine the tolerance for placement of tower foundations , roads and crane pads. Wind turbines cause noise and sometimes visual pollution and hence need to be placed away from civilization. 63

Slide 64:

Ecology of proposed site locations. For example , wind farms should not be built in the migratory path of birds or in areas that are recognized by their wildlife, plant life or unique geographical features. Proximity to transmission grid affects the economic viability. Site terrain – The more remote and complex the terrain is the higher the development cost is likely to be. 64

Slide 65:

Location where there is constant wind throughout the year. Density and frequency of flying insects-They affect the leading edge of turbine blades and thereby reduce the performance of the turbine. There will be an increase in maintenance costs if blades need to be washed regularly Cost of land Exposure to extreme wind speeds or other climatological events such as cyclones. 65

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