WIND POWER POWER AVAILABLE FROM THE WIND PERFORMANCE OF A HAWT DESIGN PROCEDURES

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

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.

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

CONTROL VOLUME FOR SIMPLE ANALYSIS OF WIND TURBINE PERFORMANCE

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

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

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 1/3 rd HIGHER THAN A 3 BLADED ROTOR OPTIMUM T/S BETWEEN 6 & 20

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

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

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

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

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.

EFFECT OF Vm ON RAYLEIGH DISTRBN

EFFICIENCY = POWER OUTPUT/POWER IN WIND

FORCES ON TURBINES VERTICAL WIND SHEAR HORIZONTAL WIND SHEAR WIND GUSTS GRAVITY TOWER SHADOW

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