How Winds are Created n n The earths

How Winds are Created n n The earth’s winds are caused by pressure differences across the earth’s surface due to uneven heating Local Winds: During the day the air over the land is heated more than the air over the sea. Opposite during the night ¨ Day pattern: Wind blows from sea to land ¨ Night pattern: Wind blows from land to sea

How Winds are created n n n Global Winds: Occur due to greater heating of the air near the equator than the poles. Thus wind blows in the direction from the poles to the equator Large ocean and land masses also affect the wind pattern It is important to understand these wind patterns for the evaluation of potential wind sites

U. S. Wind Resource Map

Classes of Wind Power Density at 10 m and 50 m(a). 10 m (33 ft) 50 m (164 ft) Wind Speed(b) Power m/s (mph) Class Density (W/m 2) 1 <100 <4. 4 (9. 8) <200 <5. 6 (12. 5) 2 100 - 150 4. 4 (9. 8)/5. 1 (11. 5) 200 - 300 5. 6 (12. 5)/6. 4 (14. 3) 3 150 - 200 5. 1 (11. 5)/5. 6 (12. 5) 300 - 400 6. 4 (14. 3)/7. 0 (15. 7) 4 200 - 250 5. 6 (12. 5)/6. 0 (13. 4) 400 - 500 7. 0 (15. 7)/7. 5 (16. 8) 5 250 - 300 6. 0 (13. 4)/6. 4 (14. 3) 500 - 600 7. 5 (16. 8)/8. 0 (17. 9) 6 300 - 400 6. 4 (14. 3)/7. 0 (15. 7) 600 - 800 8. 0 (17. 9)/8. 8 (19. 7) 7 >400 >7. 0 (15. 7) >800 >8. 8 (19. 7)

Modern Wind Turbine Wind power systems are composed of: n Tower n Rotor with 2 or 3 blades (fiberglass reinforced plastics, epoxy laminates n Yaw Mechanism such as a tail vane n Low-speed shaft, high-speed shaft, and gearbox (Mechanical Drive Train) n Electrical generator n Speed sensors and control Modern wind power systems also include: n Power electronics n Control electronics n Batteries to improve the load availability when in stand-alone mode n Transmission link connecting to the area grid

Characteristic of Wind Turbines n Variations in wind speed causes fluctuations in the amount of power produced ¨ ¨ n n n Short Term: Gusts and Turbulence Long Term: Seasonal Changes WTs have a cut-in, cut-out and a peak power output for a given wind velocity Power from the wind is proportional to the area swept by the rotors In practice, the max power efficiency is 45%

Global Picture

Wind Power ce: GWEC (Global Wind Energy Council) 2008: /www. gwec. net/fileadmin/documents/Press. Releases/PR_stats_annex_table_2 nd_feb_final. pdf

Wind Power Source: GWEC (Global Wind Energy Council) 2008: http: //www. gwec. net/fileadmin/documents/Press. Releases/PR_stats_annex_table_2 nd_feb_final. pdf

Top 10 total installed capacity Top 10 added capacity (2008) Source: GWEC (Global Wind Energy Council) 2008: http: //www. gwec. net/fileadmin/documents/Press. Releases/PR_stats_annex_table_2 nd_feb_final. pdf

Total Installed Wind Capacity

Total Installed Wind Capacity

Cost Analysis Wind energy generation costs have dramatically decreased over the last 25 years from 40 cents/KWh to 4 cents/KWh n 20 years from now wind energy is expected to be cheaper than conventional sources of energy n

Advantages and Disadvantages of Wind Turbines n Advantages ¨ Clean Source of Energy ¨ Unlimited Supply ¨ Popular with the Public n Disadvantages ¨ How do wind plants impact the power system grid (Not enough data) ¨ Very expensive to install and connect to the power grid

Wind Turbine Power: P = 0. 5 x rho x A x Cp x V 3 x Ng x Nb P = power in watts (746 watts = 1 hp) rho = air density (about 1. 225 kg/m 3 at sea level, less higher up) A = rotor swept area, exposed to the wind (m 2) Cp = Coefficient of performance (. 59 {Betz limit} is the maximum theoretically possible, . 35 for a good design) V = wind speed in meters/sec (20 mph = 9 m/s) Ng = generator efficiency (50% for car alternator, 80% or possibly more for a permanent magnet generator or gridconnected induction generator) Nb = gearbox/bearings efficiency (depends, could be as high as 95% if good)

Wind Turbine Noise Levels

Electricity Demand Varies throughout the Day Natural Gas Nuclear Total Coal Capacity Coal Source: ERCOT Reliability/Resource Update 2006

Wind and ERCOT daily load Source: Dispatchable Hybrid Wind/Solar Power Plant, Mark Kapner, P. E

ERCOT load duration curve 2007 Source: Dispatchable Hybrid Wind/Solar Power Plant, Mark Kapner, P. E

Average hourly wind speed Jan. Nov. 2008 16. 00 14. 00 January 12. 00 February March 10. 00 April May 8. 00 June July 6. 00 August September 4. 00 October November 2. 00 0. 00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Source: West Texas A &M University http: //www. windenergy. org/datasites/1405 -olfen/index. html

Statutory goal adopted in 1999, revised in 2005 Year 2003 2005 2007 Today 2015 Goal 400 850 1400 5880 Actual 990 1190 3100 6450 Non. Wind 45 45 77 136 33 mw biomass; 69 mw landfill gas; 33 mw hydro; 1 mw solar 24 October 15, 2008 GOAL FOR RENEWABLE ENERGY

October 15, 2008 CREZ SCENARIOS Capacity of New CREZ Wind by Scenario (MW) Wind Zone Scen. 1 2 3 Scen. 4 Panhandle 1, 422 A 3, 191 4, 960 6, 660 Panhandle 1, 067 B 2, 393 3, 720 0 Mc. Camey 829 1, 859 2, 890 3, 190 Central 1, 358 3, 047 4, 735 5, 615 Central West 474 1, 063 1, 651 2, 051 Total* 12, 053 18, 456 24, 859 24, 419 25 * Assumes 6, 903 MW of existing wind capacity

• 1, 705 miles of new 345 -k. V October 15, 2008 SCENARIO 2 TRANSMISSION PLAN double circuits • 453 miles of new 345 -k. V single circuit • 371 miles of 345 -k. V rebuild & upgrade $4. 9 billion cost, not including interconnection facilities 26

September 10, 2008 WHAT’S AHEAD FOR ERCOT WIND DEVELOPMENT n Concern about over-development of West Texas wind ¨ Development beyond CREZ plan could reduce market value of all West Texas wind production n In next few years, congestion between West Texas and population centers will be significant n ERCOT transition to nodal market has been delayed n Concerns about reliability with high levels of wind ¨ Forecasting wind, adequate thermal generation to match swings in load and wind generation, cost of load-following 27 services