3.introduction to wind energy
DESCRIPTION
it describes the history of wind energy in india.TRANSCRIPT
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Introduction
to
Wind Energy
History
Turbine Types
Large Systems
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WIND POWER - What is it?
All renewable energy (except tidal and geothermal power), ultimately comes from the sun
The earth receives 1.74 x 1017 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 earths surface and atmosphere induces vertical and horizontal air currents that are affected by the earths
rotation and contours of the land WIND.
~ e.g.: Land Sea Breeze Cycle
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Wind Zones in India
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Early History
5000 BCE (before common era): Sailing ships on the Nile River were likely the first use of wind power
Hammurabi, ruler of Babylonia, used wind power for irrigation
Hero (Heron) created a wind-pumped organ
Persians created a Vertical Axis WT (VAWT) in the mid 7th Century
1191 AD: The English used wind turbines
1270: Post-mill used in Holland
1439: Corn-grinding in Holland
1600: Tower mill with rotating top or cap
1750: Dutch mill imported to America
1850: American multiblade wind pump development; 6.5 million until 1930; was produced in Heller-Allen Co., Napoleon, Ohio
1890: Danish 23-meter diameter turbine produced electricity
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5Early History
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6Early History
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7Early History
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June 19 20, 2007 Wind Energy 8
English Post Mills
Built around a central post
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Wind Energy 9
Livestock Water
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Later History 1920: Early Twentieth Century saw wind-driven water-pumps commonly used in
rural America, but the spread of electricity lines in 1930s (Rural Electrification Act) caused their decline
1925: Windcharger and Jacobs turbines popular for battery charging at 32V; 32Vdc appliances common for gas generators
http://telosnet.com/wind/20th.html
http://telosnet.com/wind/20th.html
1940: 1250kW Rutland Vermont (Putnam) 53m system (center)
1957-1960: 200kW Danish Gedser mill (right)
1972: NASA/NSF wind turbine research
1979: 2MW NASA/DOE 61m diameter turbine in NC
Now, many windfarms are in use worldwide
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11
Grandpas Knob
Smith Putnam Machine
1941
Rutland, Vermont
1.25 MW
53 meters (largest turbine for 40 years)
Structural steel
Lost blade in 1945
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12
Increased incentives
Rise in oil prices in early 1970s prompted governments research and incentives
Key players: Rocky Flats Small HAWTs < 100 kW
NASA Lewis Large HAWTs > 100 kW
Sandia Labs VAWTs
Result: the Mod series Mod 0 Plum Brook, Ohio
Mod 1 Boone, North Carolina
Mod 2 Washington, Calif, & Wyoming
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13
Mod 0 (200 kW)
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June 19 20, 2007 Wind Energy 14
Mod 1 (2 MW)
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15
Mod 5b (3.2 MW)
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Modern Wind TurbinesTurbines can be categorized into two classes
based on the orientation of the rotor.
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Types of Turbines: HAWT & VAWT
HAWT (Horizontal Axis Wind Turbines) have the rotor spinning around a horizontal axis
The rotor vertical axis must turn to track the wind
Gyroscopic precession forces occur as the turbine
turns to track the wind
VAWT (Vertical Axis Wind Turbines) have the rotor
spinning around a vertical axis
This Savonius rotor will instantly extract energy regardless of the wind direction
The wind forces on the blades reverse each
half-turn causing fatigue of the mountings
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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
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VAWT Examples
Darrieus troposkein blades (jump rope)
Savonius rotor ~1925
Madaras rotor using the Magnus Effect
Rotors placed on train cars to push them around a circular track
Vortex Turbine
The SANDIA Darrieus turbinewas destroyed when left unbraked overnight
http://telosnet.com/wind/govprog.html
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Some VAWT concepts
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Vertical Axis Wind Turbines (VAWT)
Savonius
Darrieus
with Savonius
Panemone,
1000 B.C.
Giromill
This sample shows the diversity of VAWT over the years
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VAWTs 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 VAWTs. They can also usually be installed on a roof or in a city where wind is poor.
WindStorMag-Wind
WindTree Wind Wandler
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Vertical Axis Turbines
Advantages
o Omni directional
- accepts wind from any direction
o Components can be mounted at ground level
- ease of service
- lighter weight towers
o Can theoretically use less use less materials to capture the same amount of wind
Disadvantageso Rotors generally near ground
where wind is poorer
o Centrifugal force stresses blades
o Poor self-starting capabilities
o Requires support at top of turbine rotor
o Requires entire rotor to be removed to replace bearings
o Overall poor performance and reliability
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Some HAWT concepts
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HAWT Examples
Charles Brush (arc light) home turbine of 1888 (center)
17 m, 1:50 step-up to drive 500 rpm generator
NASA Mod 0, 1, 2 turbines
The Mod-0A at Clayton NM produced 200kW (below left)
http://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/20th.html
http://www.windmission.dk/
projects/Nybroe%20Home/l
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Horizontal Axis Wind Turbines (HAWT)
Ref.: WTC
1.8 m
75 m
American
Farm, 1854
Sailwing,
1300 A.D.
Dutch with
fantail
Modern
Turbines
Experimental Wind farm
Dutch post
mill
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Horizontal Axis Wind Turbines
Small (
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Horizontal vs. Vertical-Axis
Turbine type Advantages Disadvantages
HAWT Higher wind energy conversion efficiency
Access to stronger wind due to tower height
Power regulation by stall and pitch angle control at high wind speeds
Higher installation cost, stronger tower to support heavy weight of nacelle
Longer cable from top of tower to ground
Yaw control required
VAWT Lower installation cost and easier maintenance due to ground-level gearbox and generator
Operation independent of wind direction
More suitable for rooftops where strong winds are available without tower height
Lower wind energy conversionefficiency (weaker wind on lower portion of blades & limited aerodynamic performance of blades)
Higher torque fluctuations and prone to mechanical vibrations
Limited options for power regulation at high wind speeds.
Source: B. Wu, Y. Lang, N. Zargari, and S. Kouro, Power conversion and control of wind energy systems, Wiley, 2011.30
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Large Systems: Size and Numbers
Rotor hub is high above turbulent ground wind layer
Production line assembly
660kW to 7 MW power models
Groups of 10 to 1000s of turbines
Attractive, modern appearance
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Large Turbine Components
060217
Ref.: www.freefoto.com/pictures/general/ windfarm/index.asp?i=2
sgroup.cms.schunk-group.com
Note railing
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Airfoil Nomenclaturewind turbines use the same aerodynamic principals as aircraft
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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.
= low
= medium
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Airfoil
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VR = Relative Wind
V
R r
V
= angle of attack = angle between the chord line and the direction of the relative wind, VR.
VR = wind speed seen by the airfoil vector sum of V (free stream wind) and R (tip speed).
Apparent Wind & Angle of Attack
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Calculation of Wind Power
Power in the Wind
- Effect of air density ()
- Effect of swept area (A)
- Effect of wind speed (V)
AV= power of wind
Swept Area: A=R
Area of the circle swept by the rotor(m).
R
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Betz Limit
Betz Limit
5926.27
16C max,p
Rotor Wake
Rotor Disc
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%
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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
RV
TSR =
R
R
Where,
= rotational speed in radians /secR = Rotor Radius
V = Wind Free Stream Velocity
R
R
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Performance Over Range of Tip Speed Ratios
Power Coefficient Varies with Tip Speed Ratio
Characterized by Cp vs Tip Speed Ratio Curve
0.4
0.3
0.2
0.1
0.0
Cp
121086420
Tip Speed Ratio
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Power Curve