Wind Turbine
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Transcript of Wind Turbine
Wind TurbinesBY:
RAHEEL AHMADMech Engg.06-mech-28(RCET GJW)
TOPIC:
Outline
• Wind Turbines• Why Wind – causes?• How Wind Works?• How Wind Turbine Works?• Types & Sizes of Wind Turbines• Inside the Wind Turbine• Potential Turbine Power• Terms used in Wind Turbine• Advantages & Disadvantages
Wind Turbines
A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical energy.
If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator, wind turbine, wind power unit (WPU), wind energy converter (WEC), or aero generator.
Why wind Energy – Causes?
Most of our electricity is generated with non-renewable resources:
-Coal-Natural Gas-Uranium for nuclear-power
Energy
Why ?• COAL
– Mine & transport coal burn coal boil water make steam steam pushes turbine turbine coupled to generator
• NATURAL GAS– Drill for & transport gas burn gas
push turbine turbine coupled to generator
• NUCLEAR POWER– Mine & transport uranium uranium
gets hot & boils water make steam steam pushes turbine turbine coupled to generator
• WIND POWER– Wind pushes turbine turbine
coupled to generator
Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth.
Wind
Wind Energy
The terms wind energy or wind power describes the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power
Wind Turbine
How Wind Turbine Works ?So how do wind turbines make electricity?
A wind turbine works the opposite of a fan.
The wind turns the blades, which spin a shaft, which connects to a generator and
makes electricity.
This aerial view of a wind power plant shows how a group of wind turbines can make electricity for the utility grid. The electricity is sent through transmission and distribution lines to homes, businesses, schools, and so on.
Aerodynamics of Wind Turbine Blades•Forces are transmitted from a moving fluid to an object in the flow stream
–Lift = the force component perpendicular to the original flow direction–Drag = the force component in line with the original flow direction
Lift
Drag
http://www.grc.nasa.gov/WWW/K-12/airplane/newton3.html
How Wind Works ?
LIFT AND DRAG• Old-fashioned windmills
use DRAG• DRAG devices are
pushed by the wind• Modern wind turbines
(not windmills) use LIFT• LIFT devices work like
airplane wings• This is why modern
wind turbines have 3 blades
Wind – what causes it ?Wind Flow Over an Air Foil Generates LIFT
Inside Wind Turbine
Inside Wind Turbine
Yaw system
Types of Wind TurbineTurbines can be categorized into two overarching classes based on the orientation of the rotor.
1.Vertical Axis 2.Horizontal Axis
Types of Wind Turbine
1.Vertical Axis Wind Turbine
• Savonius• Darrieus
A type of wind turbine in which the axis of rotation is perpendicular to the wind stream and the ground .
Vertical-axis wind turbines fall into two major categories:
Vertical axis turbines work whatever direction the wind is blowing, but require a lot more ground space to support their guy wires than horizontal axis wind turbines.
Savonius Wind Turbine
The Savonius is a drag-type VAWT which operates in the same way as a cup anemometer
•15 % efficiency
•Applications
Cup Anemometer
An Anemometer is a wind speed measuring device.
Cup Anemometer
Darrieus Wind Turbines A Darrieus is a type of vertical axis wind turbine (VAWT) generator.
Unlike the Savonius wind turbine, the Darrieus is a lift-type VAWT. Rather than collecting the wind in cups dragging the turbine around, a Darrieus uses lift forces generated by the wind hitting aerofoil to create rotation.
Lift vs. Drag VAWTsLift 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
Horizontal Axis wind Turbine
Horizontal axis turbines (more common) need to be aimed directly at the wind.
A wind turbine in which the axis of the rotor's rotation is parallel to the wind stream and the ground.
The wind passes over both surfaces of the airfoil shaped blade but passes more rapidly over the upper side of the airfoil. The pressure differential between top and bottom surfaces results in aerodynamic lift like aeroplane blades
HAWT
•Foundation•Tower•Nacelle•Rotor•Turbine blades
Main Components
Common HAWT Construction
Rotor
• Blades are connected to a hub, which is connected to a shaft• Rotational speed will depend on blade geometry, number of blades,
and wind speed (40 to 400 revolutions per minute typical speed range)
• Gear box needed to increase speed to 1200-1800 RPM for generator
TowersLattice tower
Guyed Pole Tower
Concrete tower
Tubular steel towers
Nacelle
Types Of HAWTIt has two basic types
• Upwind Wind Turbine
• Downwind Wind Turbine
Upwind Wind Turbine• A type of wind turbine in which the rotor faces the
wind. The wind starts bending away from the tower
before it reaches the tower itself.
• The power from the wind turbine drops slightly.
• The basic drawback of upwind designs is that the rotor needs to be made rather inflexible, and placed at some distance from the tower.
• In addition an upwind machine needs a yaw mechanism to keep the rotor facing the wind.
Downwind Wind Turbine• A horizontal-axis wind turbine in which the rotor is downwind (i.e. on the lee side) of the tower.
• They may be built without a yaw mechanism.
• The rotor may be made more flexible. So the blades will bend at high wind speeds.
Number of Blades
Single Blade
Captures 10% less energy than two blade design
Double Blade
Capture 5% less energy than three blade designs
Number of Blades - Three
Increase in Number of Turbine Blade•Number of blades
–Increasing the number of blades tends to increase the aerodynamic efficiency–Increasing the number of blades increases the cost (material and manufacturing–Turbines with fewer blades tend to run most efficientlyat lower tip speed ratios(ratio of tip speed to wind speed)
http://en.wikipedia.org/wiki/Wind_turbine_design
Blade Composition
Wood
-Strong, light weight, cheap, abundant, flexible-Popular on do-it yourself turbines
Blade Composition
• Steel– Heavy & expensive
• Aluminum– Lighter-weight and
easy to work with– Expensive– Subject to metal
fatigue
Metal
Development of HAWT
SPEED n 20 17 13 5 – 15 3 – 10 rpm
Horisontal-Axis Wind Turbines
HAWT vs. VAWT
Multibrid M5000•Power output: 5 MW•Diameter: 116 m.•Turbine speed: 5,9 -14,8 rpm
•Masses: •Blade: 16.500 kg •Hub: 60.100 kg •Nacelle: 199.300 kg
Old Fashioned Turbines
The Persian windmill
The Chinese wind wheel
Wind Turbine Sizes• “SMALL”
– Residential use– 20 kW or less
• “MEDIUM”– Commercial use– 20 kW – 660 kW
• “LARGE”– Utility-scale use– 660 kW – 2+
MW
Wind Energy and Power• Atmospheric pressure differences
accelerate and impart kinetic energy into the air
• Wind energy conversion machines (WEC) convert wind energy into electrical or mechanical forms
• How much power can we extract?
time
)()(
time
K.E. Power
22
1 velocitymass
velocityareadensitytime
mass
2)()( Power
33
21
AVvelocityareadensity
Wind Turbine Size-Power Comparison
Power output
0
1 000
2 000
3 000
4 000
5 000
6 000
7 000
8 000
9 000
10 000
0 5 10 15 20 25
Wind Speed [m/s]
Po
wer
[kW
]
Growth of Wind Energy Capacity Worldwide
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06
MW
Ins
talle
d
Year
Jan 2003 Cumulative MW
Rest of World = 2,803
North America = 5,018
Europe = 21,319
Sources: BTM Consult Aps, March 2001
Windpower Monthly, January 2003
Actual Projected
Rest of World Rest of World
North America North America
Europe Europe
Tip-Speed Ratio
Tip-speed ratio is the ratio of the speed of the rotating blade tip to the speed of the free stream wind.
There is an optimum angle of attack which creates the highest lift to drag ratio.
Because angle of attack is dependant on wind speed, there is an optimum tip-speed ratio
ΩRV
TSR =
ΩR
R
Where,
Ω = rotational speed in radians /sec
R = Rotor Radius
V = Wind “Free Stream” Velocity
Rotor Solidity
Solidity is the ratio of total rotor planform area to total swept area
Low solidity (0.10) = high speed, low torque
High solidity (>0.80) = low speed, high torque
R
A
a
Solidity = 3a/A
Swept AreaThe area through which the rotor blades of a wind turbine spin, as seen when directly facing the center of the rotor blades. The power output of a wind turbine is directly related to the swept area of its blades
Advantages Of Wind Turbine
Environmental Economic Development No air pollution Wind energy is renewable No greenhouse gasses Expanding Wind Power development
brings jobs to rural communities
Disadvantages
May create a lot of noise.
Wind can never be predicted.
Wind energy depends upon the wind in an area and therefore is a variable source of energy.
It covers a large area.