Unit 10 WIND POWER

1. Unit 10 WIND POWER

2. Wind is caused from the Uneven heating of the earth.

4. The extraction of energy from Wind, especially in the form of Electricity, has enjoyed Renewed interest among Both utilities and governments. Wind energy is the fastest growing Form of energy today, up to 400% increase in the past 20 years.

5. Today, there are over 30,000 Wind turbines worldwide, with An installed capacity of Over 40,000 MW. Wind power’s environmental Impact is almost insignificant, Its main problem being visual “pollution,” although concerns About noise, communications Interference have been expressed.

7. With current wind construction, Bird mortality has fallen Substantially. Infact, bird collisions with Automobiles and windows in high Buildings cause more bird Deaths, by a factor of a million!

8. US wind power estimate map • Favorable California tax incentives resulted in major U.S. wind farms • Altamonte Pass • Tehachapi • San Gorgonio Pass • Other turbines are located in Dakotas, Iowa, OR, Texas, Minnesota, NY, WA, Wyoming, Iowa, PA, VA, Vermont, etc.

10. Wind Statistics and Assessment • Wind speed and direction are measured by an anemometer • Speed is derived from rotating cups or a spinning propeller driving an interrupter device or a small electric generator • Data are logged electronically for later processing • The mean (average) and peak (gust) speeds are of the greatest importance • Turbulence may affect turbine efficiency, but yawing points the turbine into the average wind • Ten-minute averages are used for power assessment, while gust studies may require two to ten points per second

11. Wind resources vary greatly with latitude, season, and surrounding terrain • Extensive data and wind maps exist for wind prospecting • At the mesoscale level, topographic information is being used to create predictions of wind speed from scattered real data • Anemometers can be erected to obtain wind speeds in a likely locale for comparison to NWS long-term records • An alternative is to erect a small wind turbine to sample the energy and help determine where a large turbine should be placed • Wind resources may be excellent, but there is much more to installing a turbine

12. Anemometers • Anemometers measure the speed and direction of the wind as a function of time • Spinning cups or propeller • Ultrasonic reflection (Doppler) • Sodar (Sound detection and ranging with a large horn) • Radar • Drift balloons • Etc. • Wind data are usually collected at ten-minute rate and averaged for recording • Gust studies are occasionally used, and require fast sampling at a higher rate to avoid significant information loss (4 pts/gust) • Spectral analysis indicates the frequency components of the wind structure and permits sampling frequency selection to minimize loss

13. 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 • Don’t average the speed and cube it! • Cube the various speeds and average those cubes to estimate the power • The Bergey wind turbine curve below indicates the energy output in nonturbulent flow Ref.: Bergey

14. How to find the Wind Power • A turbine power curve is cubic to start, but becomes intentionally less efficient at very high wind speeds to avoid damage • At very high winds, the power output may fall to zero, usually by design to prevent damage

15. Wind Energy Derivation Equations (also applies to water turbines) • Assume a “tube” of air the diameter, D, of the rotor • A = π D2/4 (could be rectangular for a VAWT) • A length, L, of air moves through the turbine in t seconds • L = u·t, where u is the wind speed • The tube volume is V = A·L = A·u·t • Air density, ρ, is 1.225 kg/m3 (water density ~1000 kg/m3, or 832 times more than air) • Mass, m = ρ·V = ρ·A·u·t, where V is volume • Kinetic energy = KE = ½ mu2

16. Wind Energy Equations (continued) • Substituting ρ·A·u·t for mass, and A = π D2/4 , KE = ½·π/4·ρ·D2·u3·t • Theoretical power, Pt = ½·π/4·ρ·D2·u3·t/t = 0.3927·ρa·D2·u3, ρ (rho) is the density, D is the diameter swept by the rotor blades, and u is the speed parallel to the rotor axis • Betz Law shows 59.3% of power can be extracted • Pe = Pt·59.3%·ήr·ήt·ήg, where Pe is the extracted power, ήr is rotor efficiency, ήt is mechanical transmission efficiency, and ήg is generator efficiency • For example, 59.3%·90%·98%·80% = 42% extraction of theoretical power

18. Advantages and Disadvantages of Wind Systems • Wind systems, more than solar, provide variable energy as the weather changes rapidly • Storage is required to have energy available when the wind isn’t blowing and smooth it somewhat; batteries now exist for this • This highly variable wind sends variable power to lines; each turbine has different outputs, reducing electrical line variability by the square root of the number of turbines • Large utility size turbines now produce energy at a cost competitive with fossil fuels, but it takes a lot of them to get comparable energy • A typical utility plant may have nearly 1000 MW or 1 GW peak power, while a “large” turbine might be rated at 4 MW at 25 mph wind --- that’s 250 turbines for rated wind speed! • Largest now is the Enercon E-126: 126 m diameter and 7+ MW nameplate rating at Emden, Germany • 10 MW to come: http://www.cpi.umist.ac.uk/Eminent/publicFiles/brno/RISO_Future_10MW_Wind_Turbine.pdf

19. Overview: Wind Turbine Systems • 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 http://telosnet.com/wind/early.html

20. 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

21. 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 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 http://telosnet.com/wind/20th.html http://telosnet.com/wind/20th.html

22. 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 • The two-phase design with the two sections at right angles to each other starts more easily • This is available in parts for experimenter Photo by F. Leslie, 2001

23. 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://www.windmission.dk/projects/Nybroe%20Home/l http://telosnet.com/wind/govprog.html http://telosnet.com/wind/20th.html

24. Horizontal Axis Wind Turbines (HAWT) Sailwing,1300 A.D. Experimental Wind farm American Farm, 1854 Dutch with fantail 1.8 m Modern Turbines Dutch post mill 75 m Ref.: WTC

25. 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

26. Location of Turbines: USA States • If wind projects are measured by commercial success, the Southeast USA isn’t the best area to use! 2003 http://telosnet.com/wind/recent.html http://www.awea.org/projects/index.html, showing MW in each state 9/30/2007

27. 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 turbine • Energy is power times the time of energy persistence Ref.: Bergey

28. Turbine Power Curves • 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 damage • Large 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

29. 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 www.windenergy.org

30. Large Systems: Examples & Locations • WA: FPL Stateline and Vansycle Ridge Wind Farms • HI: Honolulu, OR: Wasco, TX: McCamey, Amarillo • NM: Clayton; near House NM • Many others in IL, NY, OH, PA, CO, WV, WY, IA, PA, MN; see AWEA website NACELLE 1 MW The nacelle is the enclosureat the top of the tower http://www.windenergy.org/Land302_files/frame.htm

31. 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 Windfarm companies usually show a side view of the string, which looks less crowded and interesting

32. 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 preferable • Undersea cables carry power to shore terminals • The turbines are clearly visible if close and often are attacked by NIMBYs who want their “viewscape” unblemished • The proposed Cape Wind farm would appear a finger-width high at arm’s length • NIMBYs want only things found in nature like ships, yachts and windsurfers (John Kerry) in view

33. Cape Wind Politics 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

34. From the “Save Our Sound” Website Area is within view of nearby islands with expensive homes

35. From the “Save Our Sound” Website I presume this family is looking in horror at the simulation?

36. Cape Wind Construction Plan • Pile-climbing barges are used to support the lift cranes and transport the rotor • The 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! http://www.capewind.org/harnessing/pcons02.htm

37. sgroup.cms.schunk-group.com Large Turbine Components Note railing Ref.: www.freefoto.com/pictures/general/ windfarm/index.asp?i=2

38. Rotor Aerodynamics • 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 rotor • Possibly 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 http://homepages.enterprise.net/hugh0piggott/download/windrotord.pdf

39. 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 5 • Blade solidity is the percent of the disk area that is solid with blades • Thrust force is the force of the wind pressing back on the rotor that the tower must resist • Stall occurs when the airstream over the blade separates due to an excessive angle of attack

40. Turbine Installation • Turbine installations consist of many steps • Land acquisition • Local permitting • Possibly provide living quarters for crews • Build a control and operations center • Provide maintenance shops • Install the turbine(s) • Build a switchyard • Connect the turbines through underground wiring to the distribution switchyard http://www.afm.dtu.dk/wind/turbines/wts4.jpg

41. Large Turbines • Large turbine installations usually require new road access for trucks to bring the parts • Monopod towers may be in long sections • Turbine blades are in one piece and may require special long trucks and long-radius-turn roads • Deep (~20 ft) concrete foundations are poured, the tower assembled, and the complete nacelle mounted on top • The blades are hoisted by crane and bolted to the rotor hub on the nacelle • Sometimes, the blades and hub are hoisted together

42. Small Turbines • Small turbines weigh from 10 to 1000 pounds • Manual or crane lifting may be used • A “gin pole” may be clamped to a tower to hold a hoisting pulley overhead to lift tower sections or the generator • Some turbines are light enough that the turbine and tower may be erected as a unit • Towers may also be designed to tilt over for turbine maintenance http://www.w9iix.com/ii00008.htm

43. Turbine Power Control • Turbine States • Stop • Slow rotor, feather blades (turn into wind), apply brakes • Start • Release brakes, set blade attack angle, continually yaw nacelle to wind direction, at speed engage power contactors • Storm Protection • Yaw to 90° from wind, feather blades, apply rotor brakes, continue to yaw to avoid wind on turbine rotor disk • Maintenance • Lock out to “Stop” state to protect workers from backfeed from wiring, engage interlocks, set warning indicators

44. Wind Turbine Siting and Installation • Turbine siting is somewhat of an art, but science is providing tools that speed the selection • Wind modeling provides energy density mapping • Accurate siting strongly determines the economic and energy success of the system • Energy storage is likely to be in batteries for the foreseeable future; more exotic methods are slow in reaching a cost-effective market entry • Since wind energy is the fastest developing energy source, the economic fall of prices will speed its adoption in areas where the wind is powerful • Wind energy is about $2.50/W and comparable with a new coal power plant

45. Grants and Assistance • In some cases, grants and/or anemometer loans from a state or the US Federal government may be approved to stimulate interest in wind energy systems • Some states provide a rebate of up to 50% of the cost • Anemometers for energy testing might consist only of a wind distance indicator with a digital readout of miles of wind (difference the readings & divide by time elapsed) • The tower used should approximate the height of the turbine rotor, but the tower may be a temporary mast like a television antenna would be mounted on • Some experts advise that it is better to simply put up a substantial tower and mount a small wind turbine on it • Wind energy can be used from the small turbine before buying a larger size 070212

47. Conclusion: Wind Theory • The theory of wind energy is based upon fluid flow, so it also applies to water turbines (water has 832 times the density) • While anemometers provide wind speed and usually direction, data processing converts the raw data into usable information • Because of the surface drag layer of the atmosphere, placing the anemometer at a “standard” height of 10 meters above the ground is important; airport anemometer heights often historically differ from 10 meters • For turbine placement, the anemometer should be at turbine hub height • The average of the speeds is not the same as the correct average of the speed cubes! • The energy extracted by a turbine is the summation of each speed cubed times the time that it persisted 070212

48. 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 hurricane • We lowered our 10-ft diameter turbine on Roberts Hall and removed the blades for Hurricane Jeanne • The anemometer remains on the WFIT tower during hurricanes so speed can be read or logged

49. Questions?

50. THE END