frank r. leslie, b. s. e. e., m. s. space technology, ls ieee 3/2/2010, rev. 2.0.5 fleslie @fit.edu;...
TRANSCRIPT
Frank R. Leslie, B. S. E. E., M. S. Space Technology, LS IEEE
3/2/2010, Rev. 2.0.5
fleslie @fit.edu; (321) 674-7377
www.fit.edu/~fleslie
12.2 Wind Turbine Systems
Wind Turbine Theory
Crude oil ~$47.46 on 3/10/2009
$78 on 3/1/10
In Other News . . .
160 m diameter, 10 MW under development http://www.cpi.umist.ac.uk/Eminent/publicFiles/brno/RISO_Future_10MW_Wind_Turbine.pdf
Clipper building “Brittanica” 10 MW turbine for offshore use at Newcastle, UK
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Wind energy turbines stem from early Persian panemones – a vertical axis spinner for grinding grain
Not all power (59.3% max) can be extracted from the wind, but the turbines are relatively simple technology
This presentation discusses the types and construction of wind turbines
Wind turbine is a generic term, and it generally denotes an electrical power generator; windmills are specifically for grinding corn, wheat, or other grains
NASA used term “WECS” for WindEnergy Convertor System
There are also wind pumps for water;wind mills are for grinding grain
12.2 Overview: Wind Turbine Systems
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http://telosnet.com/wind/early.html
12.2 About This Presentation
12.2.1 History12.2.2 Turbine Types12.2.3 Small Turbines12.2.4 Large Systems12.2.5 Components and Airfoils12.2.6 Turbine Power Issues12.2 Conclusion
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12.2.1 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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12.2.1 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
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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
12.2.2 Types of Turbines: HAWT & VAWT
HAWT (Horizontal Axis Wind Turbines) have the rotor spinning around a horizontal axisThe rotor vertical axis must turn to track the
windGyroscopic precession forces occur as the
turbine turns to track the wind
VAWT (Vertical Axis Wind Turbines) have the rotor spinning around a vertical axisThis Savonius rotor will instantly extract energy
regardless of the wind directionThe wind forces on the blades reverse each
half-turn causing fatigue of the mountingsThe two-phase design with the two sections at
right angles to each other starts more easilyThis is available in parts for experimenter
100223 Photo by F. Leslie, 2001
12.2.2.1 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)
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http://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/20th.html
http://www.windmission.dk/projects/Nybroe%20Home/l
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12.2.2.1 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
12.2.2.2 VAWT Examples
Darrieus troposkein blades (jump rope)Savonius rotor ~1925Madaras rotor using the Magnus Effect
Rotors placed on train cars to push them around a circular track
Vortex TurbineThe SANDIA Darrieus turbine
was destroyed when left unbraked overnight
090309 http://telosnet.com/wind/govprog.html
12.2. Vertical Axis Wind Turbines (VAWT)
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Savonius
Darrieuswith Savonius
Panemone, 1000 B.C.
Giromill
This sample shows the diversity of VAWT over the years
ExperimentalSavonius
If wind projects are measured by commercial success, the Southeast USA isn’t the best area to use!
The Florida Keys would be a likely area to evaluate coastal breezes
12.2.2 Location of Turbines: USA States
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http://telosnet.com/wind/recent.html
http://www.awea.org/projects/index.html, showing MW in each state
2003
9/30/2007
12.2.3 Small Wind Turbines: American
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In 1854, patented wind pumpers were popular across the US, later spreading to other nations
By 1870, improvements made with sheet steel blades stamped to an aerodynamic contour
These turbines use 2 turns of the rotor to 1 stroke of the pump lift rod gear ratio to allow starting at a low wind speed
AEI states that there are some 30,000 farm wind pumps in the Southern Great Plains at 0.25 kW each, or some 5 MW total
Typical present-day at www.ohio-windmill.com
12.2.3 Small Wind Turbines: Bergey
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Equipment: BWC 7.5 kW Wind Turbine, 3 kW Solar, ~ 90 kWh Battery Bank
Performance: ~ 40 kWh / Day at 240 VAC, 60 Hz
Customer: Renegade Radio Installation: May 1996
Results: Over 98% availability. Alternator replaced in May 1998 following wiring fault.
http://www.bergey.com/
Bergey produces small wind turbines up to 50 kW
12.2.3 Small Wind Turbines: Southwest Windpower
090310 http://www.windenergy.com/
We are have two 400-watt Air-X turbines and a 1000-watt, 10-ft diameter H-80 in our Florida Tech Wind/Solar Sea Breeze study
These turbines are available in several variations
Amateur or hobbyist wind turbines are often somewhat crude, but many sources of construction information are available
Books by Paul Gipe and Hugh Piggott are essential references
Blades are usually made of fir, pine, fiberglass, or metal Turbine at right uses a bicycle front axle for strength,
PVC blades, and a permanent magnet servomotor as a generator
12.2.3 Small Wind Turbines: “Homemade”
040218 Photos by F. Leslie, 2003
Malabar Days FL 2002?
12.2.4 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
070221 www.windenergy.org
WA: FPL Stateline and Vansycle Ridge Wind FarmsHI: Honolulu, OR: Wasco, TX: McCamey, AmarilloNM: Clayton; near House NMMany others in IL, NY, OH, PA, CO, WV, WY, IA, PA,
MN; see AWEA website
12.2.4 Large Systems: Examples & Locations
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NACELLE 1 MW
http://www.windenergy.org/Land302_files/frame.htm
The nacelle is the enclosureat the top of the tower
12.2.4 State Line Wind Farm, WA & OR
This telephoto from the anti-Cape Wind Project group, “Save Our Sound”, shows a string of turbines from the end to emphasize ugliest visual effect
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Windfarm companies usually show a side view of the string, which looks less crowded and interesting
Photos by F. Leslie, 2002
12.2.4 Large Systems: SE Washington/Oregon
FPL Stateline and Vansycle Ridge Wind Farms in southeast WA and northeast Oregon
Wasco OR shown; plowed fields for wheat underneath
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12.2.4.1 Large Systems: Offshore Installation
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Renewable Energy Research Laboratory
University of Massachusetts
Installation
Photos: Courtesy GE Wind
Manwell, J.A.. Univ. Mass.
Initial matching of alternating current frequency/phase to the utility grid used induction alternators (the a.c. form of a generator)
Induction phase-matching to the grid required that the rotor turn synchronously with the utility power frequency, usually 1800 or 3600 rpm (multiples of 60 cycles per second
These fixed speeds meant that the blade operation efficiency varied greatly with the wind speed
The field frequency that provides generator magnetic fields can be dynamically changed with electronic conversion to produce synchronized output from a variable speed rotor
12.2.4.1 Large Systems: Synchronous Generation
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12.2.4.1 Large Systems: Asynchronous Generation
A return to asynchronous (variable speed) operation allowed the rotor speed to change with wind speed, avoiding many blade airflow inefficiencies
Electronic convertors were used to change the variable frequency and voltage, or “wild”, electricity to the standard; i.e., 60 hertzElectronic conversion circuitry has decreased
in price over the last decade as high power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) became available
Single-phase can be converted to three-phase power
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12.2.4.1 Offshore Wind Farms
Wind farms are often placed offshore a few miles because the winds are unimpeded (have a good “fetch”, or upwind distance, of the wind)
Depths of less than 60 feet are preferableUndersea cables carry power to shore terminalsThe turbines are clearly visible if close and often
are attacked by NIMBYs who want their “viewscape” unblemishedThe proposed Cape Wind farm would appear a
finger-width high at arm’s lengthNIMBYs want only things found in nature like ships,
yachts and windsurfers (John Kerry) in view
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12.2.4.1 Offshore Wind Farms: UK
060221 http://www.offshorewindfarms.co.uk/sites.html
There are numerous wind fields established offshore where the wind speed is continuously high and unimpeded
Atlantic Ocean winds are strong here
12.2.4.1.1 Blythe Windfarm
Northumberland 2 MW turbines on an existing seawall
090309http://www.power-technology.com/projects/blyth/blyth1.html
12.2.4.1.2 Middelgrunden
The Middelgrunden offshore windfarm is located near Copenhagen, Denmark040223
Photo Copyright Jens H. Larsen
http://www.middelgrunden.dk/MG_UK/construction_photos/photosoffshore.htm
Twenty 2 MW turbines
76m diameter
64m above sea level
R
12.2.4.1.2 Middelgrunden Photos
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Turbines turn slowly at 8 to 20 rpm
There is a staging platform and entry hatch at the base
Some have a raised platform about 30 feet above sea level
12.2.4.1.3 Cape Wind Politics
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The Cape Wind Project http://www.capewind.org/ of 170 turbines has many detractors who don’t want to see wind turbines on Horseshoe Shoal offshore of Cape Cod MA
Environmentalist organizations are divided as to lower GHGs with clean wind power instead of coal or possible bird/bat strikes or other disturbances
Greenpeace is supporting the project; Audubon and Humane Society protest it; Sierra Club waffles on it
Robert Kennedy, Jr. opposes the windfarm although the Natural Resources Defense League organization that employs him as their lawyer endorses windfarms
A heavily funded, posh website by http://www.saveoursound.org/site/PageServer protests the project
12.2.4.1.3 From the “Save Our Sound” Website
060221 Area is within view of nearby islands with expensive homes
12.2.4.1.3 From the “Save Our Sound” Website
080218I presume this family is looking in horror at the simulation? - FRL
12.2.4.1.3 Cape Wind Construction Plan
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http://www.capewind.org/harnessing/pcons02.htm
Pile-climbing barges are used to support the lift cranes and transport the rotorThe barge is
jacked up to get a steady platform
A tall crane lifts the rotor to be pulled into place and bolted on
Not good for a windy day!
12.2.5 Large Turbine Components
060217Ref.: www.freefoto.com/pictures/general/ windfarm/index.asp?i=2
sgroup.cms.schunk-group.com
Note railing
12.2.5 Small Turbine Components
A small turbine has a free-spinning assembly that the wind turns in azimuth by pushing on the tail
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http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf
The blades of an airplane propeller are curved on the front and flatter on the back towards the plane
The blades not only pull the plane forward by their angle, but the airflow over the curve develops lift or pulling forces that move the plane forward
Turbine rotors are reversed with the curve at the downwind side and with the angle of the blade reversed; wind hits the flatter side
A model airplane propeller can’t be used as a turbine blade since the key dimensions are backwards from a wind rotorPossibly a propeller manufacturer could be persuaded to make
a “standard” profile blade that could be used in 2s, 3s, or 4s Model helicopter blades can be used since they are just one bolt-on
blade instead of a double-sided propeller; hub sets the angle
12.2.5.1 Rotor Aerodynamics
060219 http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf
12.2.5.2 Airfoils and their Design
Propellers pull the rotor into the air, which is why the British call them “airscrews”
Rotors for wind turbines are pushed by the wind, and use lift on the downwind side of the blades to pull them around the shaft faster
Blade numbers vary from 2 to perhaps 5Blade solidity is the percent of the disk area
that is solid with bladesThrust force is the force of the wind pressing
back on the rotor that the tower must resistStall occurs when the airstream over the blade
separates due to an excessive angle of attack
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12.2.5.2.1 Airfoils and their Design
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Rpm = wind speed x tip-speed-ratio x 60 / (diameter x ); TSR often ~6
Revolutions (rpm) = V x TSR x 60 / (2πR)Bergey Windpower Co. uses an advanced
pultruded blade shape made without a twist (below right)The plastic is stretched through a die to form
the shape
12.2.5.2.2 Airfoils Design: Tip Speed Ratio
The rotational tip speed divided by the wind speed yields the tip speed ratio or TSR
Drag rotors that have no lift always have a TSR of ~1 or less; they are just dragged around by the wind; Savonius or cup anemometer
Airfoil rotors gain “lift” from the wind flowing over the blade and can turn up to ~14 times the wind speed; a TSR of 6 is more likely
Matching the generator speed is helpfulThe TSR should be low enough to keep the
blade tip below ~135 mph to avoid loud noise060219
Lift = Cl ρ/2 AV2
Drag = Cd ρ/2 AV2; note similarity between lift and drag
Nominal lift and drag curves for the profile are used to select the values required
These curves are measured in a wind tunnel and can’t be computed
12.2.5.3 Lift and Drag Forces on Blade
050224 www.windmission.dk
u
L
Blade Pitchβ
α
The blade is moving rapidly and the direction of the relative wind changes with rotor speed
Angle of Attackφ
Drag Force
12.2.5.3.1 Blade Angle and Wind Forces
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Relative Wind, W
Chord Line
V1 = ~2/3 x wind velocity, V0,due to slowed wind
Lift Force
Resultant Force
RotationForce, F
RotationalVelocity
Thrust
Wind
L sin ΘD cos Θ
Maximize F = L sin Θ – D cos Θ
An airplane propeller won’t work as a wind turbine rotor; it’s backwards
Poor Lift
Lift pulls
12.2.5.3.2 Prop vs. Rotor
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AirplanePropeller CW WT Rotor
CCW WT Rotor
AirplanePropeller
Flipped Over
Wind
Wind
Motion
Weak Motion;
Backwards!
Driven Motion
Motion
No good for rotor
Lift pulls
Lift
Rotor “lift” helps pull rotor around
12.2.5.4 Blade Design
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Since the relative wind near the hub is closer to the true wind speed, the pitch of the blade must be higher there
Near the tip, the pitch is just 0-2 degrees and the blade is nearly parallel to the direction of rotation
Still, since so much of the torque comes from the end of the blade, suboptimal shapes that are designed without twist are often used for economic reasonsThe angle is then optimized at about 80-100%
of the blade radiusThe hub attachment must be very strong to resist
flexing that would break the blade at the rootThe leading edge is rounded so the wind
“attaches” to the surface of the blade as the direction changes
12.2.5.4.1 Blade Construction: Shape
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The blade profile changes angle and shape from the root to the tip
http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf
A knot-free plank is rough cut to get the outside shape
Edges are marked and excess cut away
A pattern is used to form each station along the blade
The area between blades is cut away and sanding finishes the surface smoothly
The blade profile changes angle and shape from the root to the tip
The width from nose to tail is called the chord The thickness is from one side to the other in percent of
chord; in NACA shape designation 4412 has a 12% thickness (NACA now NASA)
The round nose reduces the tendency to stall
12.2.5.4.2 Blade Construction: Shape
080228 http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf
chord
12.2.5.4.3 Blade Construction: Shape
030306
PE9 is not as wide as the previous root profile, but is much larger than PE15 at the tip
Note the slope is flatter
http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf
12.2.5.4.4 Blade Construction: Shape
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These profiles must now be made in the material, perhaps by carving wood or grinding/molding plastic
Profile templates are made to test the remaining material
When slicing or planing off the wood, when it needs just one more stroke to be done, don’t do it!
Sand the profiles to smooth the shape and fair in the curves; the blades must weigh the same on each side
The blade root must remain as thick and strong as possible to avoid breaking in gusts
Coat the blades with thin polyurethane sanding sealer and then sand with fine 250 grit sandpaper
When finished, coat with two coats of polyurethane varnish to keep water out of the wood
http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf
12.2.5.4.5 Rotor Construction: Balance
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The rotor support might be made from steel 4-5/16 inch electrical box covers; these are strong and galvanized ($0.85 each)
Some use a drilled pulley to bolt to the blades for strength The center must attach to the generator shaft, and the
blades attach to both plates, preventing blade canting from centrifugal force
With the blades somewhat loosely assembled, balance the hub plates horizontally on a point to detect a heavy blade
Next, measure the distance between the blade tips and move them slightly to equalize the distances between tips
Tighten the blade root bolts more, and fasten the rotor on a horizontal shaft in oiled bearings – perhaps a bicycle hub
If the rotor turns because one blade is heavier than the others, balancing is needed; trim the surface a little or swap blades
A temporary weight is placed on lighter blades to assess how much material is to be removed or in moving the blades in the bolt holes
12.2.5.5 Rotor Speed, Torque, and Power
Direct-drive generators or alternators avoid the losses of gearing or a belt transmission
The rotor is designed to turn at some optimum speed, and will perform less efficiently at lower or higher speeds
The generator must reach the required voltage at a reasonable rotor speed, thus must perform well at 200 to 600 rpm at perhaps the top 30% of wind speeds
If the generator is available first, design of the rotor blades must match the generator speed
If the rotor is available first, selection of the generator must match rotor speed
Rotor torque sets the starting speed, yet if the wind speed is too low to start spin, there is little wind power; don’t worry!
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12.2.6 RPM and Torque; Starting Speed
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Power = Torque, Q, x Speed, Ω (omega) or N,so Torque = P/Ω
The rotor must overcome bearing resistance, residual unbalances, magnetic cogging attraction, etc., and accelerate to a useful speed to generate charging power
During a gust of perhaps two to four seconds, the rotor must accelerate to a new speed to extract energy from the gust; light, small rotors can do this; 100m ones can’tOtherwise, the wind may cause airflow stall
over the blades as the rotor angular momentum changes too slowly due to inertia
Momentary stall protects the turbine from throwing blades
12.2.6.1 Power Is Proportional to Wind Speed Cubed
Recall that the average wind power is based upon the average of the speed cubed for each occurrence
The wind energy varies from trivial to useful to disastrous!
Precautions are needed to protect the turbineEnergy is power times the time of energy persistence
Ref.: Bergey
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12.2.6.1.1 Turbine Power Curves
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Since power is negligible at low speeds of 6 mph or less, it doesn’t matter that the turbine won’t start then
The distribution of wind speeds indicates the relative probability that wind will exceed a given value
Much of the power occurs in the top 30% of the wind speeds, so these speeds set the design parameters
For this reason, it is desirable to keep the turbine extracting power in strong winds while still protecting it from damageLarge turbines are turned out of the wind at
approximately 30 to 35 mph or their blades are turned (rotated) into the wind to produce less torque
12.2.6.1.2 Turbine Power Curves
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Fortis Montana 5800
http://www.gale force.nireland.co.uk/turbine_power_curve.htm
12.2.6.1.2 Turbine Power Curves
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Fortis Passat 1400
http://www.galeforce.nireland.co.uk/turbine_power_curve.htm
12.2 Conclusion: Wind Turbine Theory
The rotor must be matched to the generator or alternator to obtain the maximum extracted energy over a year
Although most turbines won’t rotate until the wind speed reaches 6 mph; there is no significant energy lost below this speed; power is proportional to the cube of speed
If turbine placement can increase the wind speed by 10%, the power increases by 33%
All parts must be designed to survive high winds, say 130 mph; this is important to survive a hurricaneWe lowered our 10-ft diameter turbine on Roberts Hall
and removed the blades for Hurricane JeanneThe anemometer remains on the WFIT tower during
hurricanes so speed can be read or logged
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References: Books
Gipe, Paul. Wind Power: Renewable Energy for Home, Farm, and Business. VT: White River Junction, Chelsea Green Publishing Company, 2004. ISBN 1-931498-14-8.
Piggott, Hugh. Windpower Workshop. Centre for Alternative Technology publications, 2000. ISBN 1 898049 27 0.
Boyle, Godfrey, ed.. Renewable Energy: Power for a Sustainable Future. Oxford Univ. Press, Oxford, England, 477 pp., 1996.
Gipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea Green Pub. Co., 1993. 0-930031-64-4, TJ820.G57, 621.4’5
Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136
Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN 0-12-656152-4.
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References: Websites, etc.
http://www.windpower.org/index.htmhttp://groups.yahoo.com/group/awea-wind-home/ Join this group for access to expertshttp://www.ndsu.nodak.edu/ndsu/klemen/Perfect_Turbine.htm basics of small turbineshttp://www.windturbine-analysis.com/index.htm Darrieus turbine analysis as a student project –
Excellent!http://www.sandia.gov/wind/http://www.power-technology.com/ http://telosnet.com/wind/index.html Excellent history and progress reviewhttp://www.eere.energy.gov/windpoweringamerica/ http://www.middelgrunden.dk/MG_UK/project_info/turbine.htm Offshore windfarmhttp://www.capewind.org/harnessing/pcons02.htmhttp://www.bergey.com/http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf Learn how to build a turbine!http://homepages.enterprise.net/hugh0piggott/pmgbooklet/index.htm Build a PM generatorhttp://users.aber.ac.uk/iri/WIND/TECH/WPcourse/page2.html How blades workhttp://www.espace-eolien.fr/ouest/Images_Gou.HTM French turbine photoshttp://www.windpowerindia.com/index.asp__________________________________________________________________________________-awea-windnet@yahoogroups.com. Wind Energy [email protected]. Wind energy home powersite elistrredc.nrel.gov/wind/pubs/atlas/maps/chap2/2-01m.html PNNL wind energy map of CONUS [email protected]. Elist for wind energy experimenterstelosnet.com/wind/20th.htmlsolstice.crest.org/dataweb.usbr.gov/html/powerplant_selection.html
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