Wind Turbines - Wind Energy: Renewable Energy and the Environment - page 97

8. Calculate the power from Figure 5.13 at 20 m/s for the VAWT for the following condi-
tions. Remember, rpm has to be converted to rad/s.
a. Wind turbine is operating at 160 rpm (line A).
b. Wind turbine is operating at maximum power coefficient (line B).
c. Wind turbine is operating at constant torque (line C) of 6,000 Nm.
9. From Figure 5.13, the design wind speed is 12.5 m/s (where lines A, B, and C cross).
What is the torque? What is the rpm? What is the power?
10. Calculate the wind speed frequency distribution for the data in Table 5.1 .
11. Calculate the annual energy production for a mean wind speed of 8.2 m/s, average air
density 1.1 kg/m 3 . Use the Rayleigh distribution to obtain a wind speed histogram. Use
the power curve from Table 5.1.
12. Refer to Figure 5.15 . What is the cut-in and rated wind speed for the 1,000 kW unit?
13. Refer to Figure 5.15. What is the cut-in and rated wind speed for the 400 kW unit?
14. For large wind turbines, what is the primary method of control for power output?
15. For large wind turbines, what is the primary method of control for shutdown for high
winds?
16. For loss of load, fault on the utility line, how much time is available for shutdown of the
wind turbine?
17. Are there any wind hybrid systems for village power in your country? If yes, select one
project; briefly describe location, project power rating, main components (wind, PV, die-
sel, batteries), and approximate output, kWh/day.
18. Under innovative wind turbines, what would be two or three major problems with a teth-
ered wind turbine?