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Wind Power: Design and Performance of a HAWT

This article explores the design procedures and performance of Horizontal Axis Wind Turbines (HAWT). It covers topics such as the annual wind energy available, lifting devices, wind turbine theory, tip-speed ratio, solidity, generators, power output, and forces on turbines. The conclusion highlights wind power as a dilute form of energy and its limitations.

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Wind Power: Design and Performance of a HAWT

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  1. WIND POWER • POWER AVAILABLE FROM THE WIND • PERFORMANCE OF A HAWT • DESIGN PROCEDURES

  2. ANNUAL WIND ENERGY AVAILABLE AT 50m, IN MWh/m2

  3. LIFTING DEVICE LIKE AN AIRCRAFT WING OR HELIPCOPTER ROTOR. PRESSURE DIFFERENCE PRODUCES A FORCE A COMPONENT OF THE FORCE ACTS TO PRODUCE ROTATION AND THE OTHER COMPONENT ACTS ON THE TOWER.

  4. SIMPLE WIND TURBINE THEORY • POWER COMES FROM KE OF WIND • THERE IS AN OPTIMUM POWER EXTRACTION RATE • CAN ESTIMATE FROM APPLICATION OF CONSERVATION PRINCIPLES • FORCE-MOMENTUM & BERNOULLI

  5. CONTROL VOLUME FOR SIMPLE ANALYSIS OF WIND TURBINE PERFORMANCE

  6. ACTUAL PERFORMANCE • CANNOT TAKE ALL POWER OUT OF WIND SINCE THIS WOULD SHROUD THE TURBINE IN STILL AIR • THEORETICAL MAX POWER IS 59% • PRACTICAL VALUE IS 45% • eg V = 10m/s, (Force 5) • Power = 270 W/m2

  7. EFFECT OF TIP-SPEED RATIO • OPTIMUM T/S DEPENDS ON WIDTH & NUMBER OF BLADES – SOLIDITY • BLADES NEED TO INTERACT WITH AS MUCH AIR AS POSSIBLE & FILL UP THE SWEPT AREA • MANY BLADES – HIGH SOLIDITY – LOW TIP SPEED • FEW BLADES – LOW SOLIDITY – HIGH TIP SPEED • UPPER LIMIT OF TIP SPEED -COMPRESSIBILTY

  8. TIP-SPEED RATIO • TOO LOW A SPEED - WIND GETS THROUGH WITH NO CONTACT • TOO HIGH A SPEED – BLADES OFFER TOO MUCH RESISTANCE – WIND GOES ROUND THE TURBINE • Eg 2 BLADED ROTOR HAS T/S 1/3rd HIGHER THAN A 3 BLADED ROTOR • OPTIMUM T/S BETWEEN 6 & 20

  9. BLADES • TOO MANY BLADES – INTERFERENCE- SO HIGH SOLIDITY TURBINES LESS EFFICIENT • 3 BLADES TEND TO BE BEST • GENERATORS RUN AT HIGH SPEED SO NEED A GEARBOX • SO LOW SOLIDITY GOOD BECAUSE THEY RUN AT HIGH SPEED

  10. RPM • MUST BE CONSTANT WHATEVER V • DEPENDS ON NUMBER OF POLES IN ELECTROMAGNET • N = CONSTANT = 6000/POLES • POLES = 6, 8 ETC • TURBINE MAY HAVE 2 OPERATING VALUES OF N, DEPENDING ON V

  11. POWER OUTPUT FROM A HAWT • SEE “WINDTURB” IN RESOURCE FILE • POWER IN WIND VS WINDSPEED • WINDSPEED FREQUENCY DISTRIBUTION • POWER CURVE OF TURBINE • ANNUAL POWER OUTPUT • EFFICIENCY VS WINDSPEED

  12. POWER OUTPUT CURVE FOR A TURBINE 6.5 m/s = 15mph = Force 4 A moderate wind

  13. RAYLEIGH FREQUENCY DISTBN MEAN WIND SPEED F IS THE FRACTION OF 8760 HOURS WHEN THE WIND IS AT SPEED V. MEAN WIND SPEED IS 5 m/s.

  14. EFFECT OF Vm ON RAYLEIGH DISTRBN

  15. EFFICIENCY = POWER OUTPUT/POWER IN WIND

  16. FORCES ON TURBINES • VERTICAL WIND SHEAR • HORIZONTAL WIND SHEAR • WIND GUSTS • GRAVITY • TOWER SHADOW

  17. CONCLUSIONS • A DILUTE FORM OF ENERGY • NEED TO PROCESS LARGE VOLUMES • NOT ECONOMIC UNLESS USE NFFO • NOT THE ANSWER TO GROWING ENERGY CRISIS • NEEDS ENERGY STORAGE SYSTEM • CAN DISPLACE UP TO 10% OF ELECTRICAL SUPPLIES

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