Presentation on theme: "The basics of wind energy and recommendations to installing Small Wind Systems Southwest Windpower, Inc."— Presentation transcript:
The basics of wind energy and recommendations to installing Small Wind Systems Southwest Windpower, Inc.
Wind is a form of Solar Energy u Wind is solar energy transformed to kinetic energy u Earth absorbs 120,000 terawatts (120·10 15 watts) of energy from the sun. 0.3% is transformed into wind. This is 26 times the worlds current energy use. RERADIATED HEAT 82,000 ABSORBED 120,000GEOTHERMAL HEAT 30 SOLAR RADIATION 178,000 PHOTOSYNTHESIS 100 TIDES 3 HEAT FROM EVAPORATION 40,000 REFLECTED TO SPACE 53,000 KINETIC ENERGY 350
The details of wind Important information about wind energy that you really dont need to worry about but is good to know
Wind energy in scientific notation K.E. = 1/2 mv 2 K.E. of wind = 1/ 2p Av 3 t – p = density of air – A = swept area – v = wind velocity u Power = K.E. of wind/time
Wind speed -and- Potential Energy Power in 1 m 2 at a wind speed of 3 m/s: 0.5 x x 3.14 x 1 2 x 3 3 = 51 W Power in 1 m 2 at a wind speed of 5 m/s 0.5 x x 3.14 x 1 2 x 5 3 = 236 W Energy Available in the wind follows the equation ½ (air pressure) x 3.14 (pi) x (blade length) 2 x (wind velocity) 3 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 Power in 1 m 2 at a wind speed of 4 m/s: 0.5 x x 3.14 x 1 2 x 4 3 = 121 W Power in 1 m 2 at a wind speed of 8 m/s 0.5 x x 3.14 x 1 2 x 8 3 = 968 W Energy Available in the wind follows the equation ½ (air pressure) x 3.14 (pi) x (blade length) 2 x (wind velocity) 3 Every time wind velocity doubles, available energy increases 8 times!
Swept Area -and- Potential Energy Power in 1 m 2 at a wind speed of 5 m/s: 0.5 x x 3.14 x 1 2 x 5 3 = 236 W Power in 1.5 m 2 at a wind speed of 5 m/s 0.5 x x 3.14 x x 5 3 = 532 W Swept Area is the best way to determine Turbine Performance at normal wind speeds (sub 18 mph avg.) How does Swept Area affect Potential Energy? How does a 1 m blade compare with a 1.5 m blade? [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.ActualBetz Lmt.Available AIR X31% 30 W 58 W 98 W H4031% 80 W 154 W 260 W H8028%150 W 314 W 531 W 17535%420 W 706 W1196 W
Weibull Distribution From Hybrid Power Design Handbook, by C.D. Barley WIND SPEED AVERAGE IN METERS PER SECOND – M/S Frequency at which the wind blows 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 surface HEIGHT WINDSPEED (ft) (mph) V = Vo(H/Ho) Tall towers matter – each 30 foot increase in height will result in another 25% Energy Output!
The Details in Wind u Elevation u Tower height u Wind speed average Important information about wind energy that you really do need to know
Elevation Altitude: Density decreases with altitude Output compared to power curve feet1-150 meters100% feet meters97% feet meters94% feet meters91% feet meters88% feet meters85% feet meters82% feet meters79% feet meters73% ,000 feet meters70%
Siting wind – It really is easy
Barriers to wind flow u 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 H Region of Highly Disturbed Flow 2H 20H PREVAILING WIND Undisturbed upstream wind speed profile 5H 10H 15H High Turbulence 5H10H15H Speed Decrease 17%6%3% Turbulence Increase 20%5%2% Wind Power Decrease 43%17%9% Appropriate maximum values depend Upon building shape, terrain and other Nearby obstacles. Good location for wind turbine Turbulence 2H2H
5H10-15 H H WINDWARD LEEWARD Turbulent Region Turbulent Region Turbulent Region Wind Direction 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 Siting behind a row of trees
Streamers and turbulence Top of barrier-induced turbulence Turbulent Flow Smooth Flow (Good height to install a Southwest Windpower Turbine) 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. Predominant wind direction Kite
Acceleration over a ridge 100%50% 120% 200% Possible High Turbulence Crest of Ridge Crest of Windflow (also region of maximum wind acceleration) Wind Speed Wind Speed
Airflow over cliffs (A) (C) (D) (B) = Turbulence
Valleys between mountains Zone of accelerated air flow Prevailing winds Mountains Plains (A) (B) Zone of high wind velocities Valley Mountains Plains Prevailing Winds Plains Valleys can be areas of high wind speeds when winds are funneled and accelerated because of the topography (valleys between mountains) Mountains
Siting using vegetation u Brushing: Branches and twigs bend downwind. u Flagging: Branches stream downwind, upwind branches are short u Throwing: A tree has trunk and branches bent downwind u Carpeting: Winds are so strong it will not allow vertical growth of tree
Deformation Ratio D = A/B + C/45 Prevailing Wind Direction BA C Deformation Ratio IIIIIIIV VVI Probable Mean Annual Wind Speed Range (MPH) Source: Data prepared by E.W. Hewson, J.E. Wade, and R.W. Baker of Oregon State University.
Griggs-Putnam Index Prevailing Wind 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 m/s Km/h IIIIIIIVVVIVII No DeformityBrush and Slight Flagging Slight Flagging Moderate Flagging Complete Flagging Partial Throwing Complete Throwing Carpeting
Siting with no vegetation If your customer can fly a flag, they can run wind turbine!
In a nutshell – it is just common sense u Know your wind speed average –Wind maps –Local weather or television station –Local airport u Site tower 30 (9 meters) above any surrounding object within a 300 foot radius u Know the elevation to estimate energy loss