SCHOOL OF ENGINEERING AND SCHOOL PH/EE/MM 301: Energy S

SCHOOL OF ENGINEERING AND SCHOOL PH/EE/MM 301: Energy Supplies Tutorial 1 Wind 1. Describe a Horizontal Axis Wind Turbine (HAWT) and discuss its principle of operation. List the advantages of HAWT to that of vertical axis. Define capacity factor and availability factor of a wind turbine. 2. By considering the ratios of A0 and A1 of the figure below show that the optimum power extraction (according to linear momentum theory) per unit area A0 is 8/9 of the incident power in the wind. 3. A number of designs of wind turbine pass the output wind from on set of blades immediately on to a second identical set (e.g. two contrary rotating blades set on the same horizontal axis). By considering two actuator disks in series and using linear momentum theory show that the combined maximum power coefficient Cp equals 0.64. Note: This is only slightly larger than the maximum of 16/27 = 0.59 for a single pass of the wind through one set of blades. Thus in a tandem horizontal axis machine of identical blade sets and indeed in a vertical axis turbine little extra power is gained by the airstream passing a second set of blades at such close proximity. 4. a) A wind turbine maintains a tip-speed ratio of 8 at all wind speeds. At which wind speed will the blade tip exceed the speed of sound? b) A large wind turbine has a blade diameter of 100 m. At what rotor speed (i.e. frequency) will the tip-speed exceed the speed of sound? 5. a) Calculate the possible maximum axial thrust per unit area of rotor for a wind turbine in a 20 m s-1 wind. b) The Danish standard for axial thrust design is 300 N m-2 of rotor area. What is the minimum possible wind speed that this corresponds to? Dr. Ajal Kumar
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