# Southwest Windpower, Inc.

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Southwest Windpower, Inc.
The basics of wind energy and recommendations to installing Small Wind Systems

Wind is a form of Solar Energy
REFLECTED TO SPACE 53,000 SOLAR RADIATION 178,000 RERADIATED HEAT 82,000 PHOTOSYNTHESIS 100 KINETIC ENERGY 350 HEAT FROM EVAPORATION 40,000 TIDES 3 GEOTHERMAL HEAT 30 ABSORBED 120,000 Wind is solar energy transformed to kinetic energy Earth absorbs 120,000 terawatts (120·1015 watts) of energy from the sun. 0.3% is transformed into wind. This is 26 times the world’s current energy use.

The details of wind Important information about wind energy that you really don’t need to worry about but is good to know

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

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/s: 0.5 x x 3.14 x 12 x 33 = 51 W Power in 1 m2 at a wind speed of 5 m/s x 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!

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/s: 0.5 x x 3.14 x 12 x 43 = 121 W Power in 1 m2 at a wind speed of 8 m/s 0.5 x x 3.14 x 12 x 83 = 968 W Every time wind velocity doubles, available energy increases 8 times!

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/s: 0.5 x x 3.14 x 12 x 53 = 236 W Power in 1.5 m2 at a wind speed of 5 m/s 0.5 x 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!]

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 W W H40 31% W W W H80 28% 150 W W W % 420 W W W

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. K=2.5 shows more consistent winds. However, the more gusty site with k=1.5 contains significantly more energy because of the greater occurrences of 10+ m/s velocities.

Roughness for flat terrain

Wind speed change with height
V = Vo(H/Ho) HEIGHT WINDSPEED (ft) (mph) 13.5 90 12.9 60 12.2 30 10 surface Tall towers matter – each 30 foot increase in height will result in another 25% Energy Output!

The Details in Wind Elevation Tower height Wind speed average
Important information about wind energy that you really do need to know Elevation Tower height Wind speed average

Elevation Altitude: Density decreases with altitude
Output compared to power curve 1-500 feet meters 100% feet meters 97% feet meters 94% feet meters 91% feet meters 88% feet meters 85% feet meters 82% feet meters 79% feet meters 73% ,000 feet meters 70%

Siting wind – It really is easy

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.

Building Obstructions
Good location for wind turbine Good location for wind turbine PREVAILING WIND Region of Highly Disturbed Flow Turbulence 2H 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 43% 9% 15H Turbulence 10H 5H Appropriate maximum values depend Upon building shape, terrain and other Nearby obstacles. 2H Turbulence

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

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.

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

Airflow over cliffs = Turbulence (A) (B) (C) (D)

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

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

Deformation Ratio I II III IV V VI 5-9 8-11 10-13 12-16 14-18 15-21
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.

Griggs-Putnam Index MPH 7-9 9-11 11-13 13-16 15-18 16-21 22+ m/s 3-4
Prevailing Wind 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+

Siting with no vegetation
If your customer can fly a flag, they can run wind turbine!

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

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