The basics of wind energy and recommendations to installing Small Wind Systems

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The basics of wind energy and recommendations to
installing Small Wind Systems
Southwest Windpower, Inc.
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Wind is a form of Solar Energy
SOLAR RADIATION 178,000
REFLECTED TO SPACE 53,000
RERADIATED HEAT 82,000
PHOTOSYNTHESIS 100
KINETIC ENERGY 350
HEAT FROM EVAPORATION 40,000
TIDES 3
ABSORBED 120,000
GEOTHERMAL HEAT 30

• Wind is solar energy transformed to kinetic
  energy
• Earth absorbs 120,000 terawatts (1201015 watts)
  of energy from the sun. 0.3 is transformed into
  wind. This is 26 times the worlds current energy
  use.

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The details of wind

• Important information about wind energy that you
  really dont need to worry about but is good to
  know

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Wind energy in scientific notation

• K.E. 1/2mv2
• K.E. of wind 1/2pAv3t
• p density of air
• A swept area
• v wind velocity
• Power K.E. of wind/time

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Wind speed -and- Potential Energy
Energy Available in the wind follows the
equation ½ (air pressure) x 3.14 (pi) x (blade
length)2 x (wind velocity)3
Power in 1 m2 at a wind speed of 3 m/s0.5 x
1.204 x 3.14 x 12 x 33 51 WPower in 1 m2 at a
wind speed of 5 m/s 0.5 x 1.204 x 3.14 x 12 x
53 236 W
Beware of turbines that claim great low wind
speed performance only 51 Watts are available
at 3 m/s using a 1 m blade!
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Wind speed -and- Potential Energy
Energy Available in the wind follows the
equation ½ (air pressure) x 3.14 (pi) x (blade
length)2 x (wind velocity)3
Power in 1 m2 at a wind speed of 4 m/s0.5 x
1.204 x 3.14 x 12 x 43 121 WPower in 1 m2 at
a wind speed of 8 m/s0.5 x 1.204 x 3.14 x 12 x
83 968 W
Every time wind velocity doubles, available
energy increases 8 times!
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Swept Area -and- Potential Energy
How does Swept Area affect Potential Energy? How
does a 1 m blade compare with a 1.5 m blade?
Power in 1 m2 at a wind speed of 5 m/s0.5 x
1.204 x 3.14 x 12 x 53 236 WPower in 1.5 m2
at a wind speed of 5 m/s0.5 x 1.204 x 3.14 x
1.52 x 53 532 W
Swept Area is the best way to determine
Turbine Performance at normal wind speeds (sub 18
mph avg.)
Keep this fact in mind when comparing the
Whisper H40 with the Whisper H80!
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Betz Limit
The maximum amount of energy that may be
extracted from the wind utilizing a wind turbine
is 59 of Available Energy. Most commercial
turbines hover in the 20-35 efficiency
(extracted energy divided by available
energy). How do SWWP Turbines fare at 5 m/s?
Eff. Actual Betz Lmt. Available AIR X 31
30 W 58 W 98 W H40 31
80 W 154 W 260 W H80 28 150 W 314
W 531 W 175 35 420 W 706 W 1196
W
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Weibull Distribution
Frequency at which the wind blows
From Hybrid Power Design Handbook, by C.D. Barley
WIND SPEED AVERAGE IN METERS PER SECOND M/S
All 3 curves have the same Average Wind Speed,
but will vary greatly in energy available.
K2.5 shows more consistent winds. However, the
more gusty site with k1.5 contains significantly
more energy because of the greater occurrences of
10 m/s velocities.
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Roughness for flat terrain
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Wind speed change with height
V Vo(H/Ho)?
HEIGHT WINDSPEED (ft) (mph)
13.5
90
12.9
60
12.2
30
10
0
surface
Tall towers matter each 30 foot increase in
height will result in another 25 Energy Output!
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The Details in Wind
Important information about wind energy that you
really do need to know

• Elevation
• Tower height
• Wind speed average

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Elevation
Altitude Density decreases with altitude
Output compared to power curve 1-500 feet 1-150
meters 100 500-1000 feet 150-300
meters 97 1000-2000 feet 300-600
meters 94 2000-3000 feet 600-900
meters 91 3000-4000 feet 900-1200
meters 88 4000-5000 feet 1200-1500
meters 85 5000-6000 feet 1500-1800
meters 82 7000-8000 feet 2100-2400
meters 79 8000-9000 feet 2400-2700
meters 73 9000-10,000 feet 2700-3000
meters 70
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Siting wind It really is easy
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Barriers to wind flow

• Barriers produce disturbed areas of airflow
  downwind which are called wakes. In barrier
  wakes, wind speed is reduced and rapid changes in
  wind speed and direction, called turbulence, are
  increased.

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Building Obstructions
Good location for wind turbine
Good location for wind turbine
Region of Highly Disturbed Flow
PREVAILING WIND
2H
Turbulence
Turbulence
H
Turbulence
2H
20H
High Turbulence
Undisturbed upstream wind speed profile
5H 10H 15H
Speed Decrease 17 6 3
Turbulence Increase 20 5 2
Wind Power Decrease 43 17 9
15H
Turbulence
10H
5H
Appropriate maximum values depend Upon building
shape, terrain and other Nearby obstacles.
Turbulence
2H
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Siting behind a row of trees
The region underneath the curve has too much
turbulence, and is not a good site to install a
wind turbine. This Region is determined by the
height (H) of the tallest tree. The region with
the straight, smooth lines ABOVE the Curve has
air flow that is laminar, free flowing, which is
IDEAL for a wind turbine.
Good location for wind turbine
WINDWARD
LEEWARD
Good location for wind turbine
Good location for wind turbine
Turbulent Region
H
Turbulent Region
Turbulent Region
Wind Direction
5H
10-15 H
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Streamers and turbulence
Kite
Smooth Flow (Good height to install a Southwest
Windpower Turbine)
Top of barrier-induced turbulence
Predominant wind direction
Turbulent Flow
By using a kite and adding streamers to the line
you can determine the area behind trees or
buildings where turbulence is present. The
area with smooth air flow will have a straight
streamer as opposed to turbulent streamers that
are flapping constantly.
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Acceleration over a ridge
Crest of Windflow (also region of maximum wind
acceleration)
Wind Speed
Possible High Turbulence
Crest of Ridge
200
120
100
50
Wind Speed
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Airflow over cliffs
Turbulence
(A)
(B)

(C)
(D)
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Valleys between mountains
Prevailing winds
Zone of accelerated air flow
Mountains
Plains
Plains
(A)
Mountains
Valleys can be areas of high wind speeds when
winds are funneled and accelerated because of the
topography (valleys between mountains)
Zone of high wind velocities
Mountains
Plains
Valley
(B)
Mountains
Prevailing Winds
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Siting using vegetation

• Brushing Branches and twigs bend downwind.
• Flagging Branches stream downwind, upwind
  branches are short
• Throwing A tree has trunk and branches bent
  downwind
• Carpeting Winds are so strong it will not allow
  vertical growth of tree

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Deformation Ratio
D A/B C/45 Prevailing Wind Direction
C
B
A
Deformation Ratio I II III IV V VI
Probable Mean Annual Wind Speed Range (MPH) 5-9 8-11 10-13 12-16 14-18 15-21
Source Data prepared by E.W. Hewson, J.E. Wade,
and R.W. Baker of Oregon State University.
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Griggs-Putnam Index
Prevailing Wind
0
I
II
III
IV
V
VI
VII
No Deformity
Brush and Slight Flagging
Slight Flagging
Moderate Flagging
Complete Flagging
Partial Throwing
Complete Throwing
Carpeting
The degree to which conifers have been deformed
by the wind can be used as a rough gauge of
average annual wind speed. (Battelle, PNL)
Wind Speed Index I II III IV V VI VII
MPH 7-9 9-11 11-13 13-16 15-18 16-21 22
m/s 3-4 4-5 5-6 6-7 7-8 8-9 10
Km/h 11-14 14-18 18-21 21-25 25-29 29-32 36
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Siting with no vegetation
If your customer can fly a flag, they can run
wind turbine!
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In a nutshell it is just common sense

• Know your wind speed average
• Wind maps
• Local weather or television station
• Local airport
• Site tower 30 (9 meters) above any surrounding
  object within a 300 foot radius
• Know the elevation to estimate energy loss