Site Assessment and Installation - Small Wind Turbines: Analysis, Design, and Application - page 263

p

¼

p

f T ¼ 2

½ cos h =ðÞ sin h =ðÞ 21 sin h ð Þ

when b = 90. What are the maximum and minimum values of f T ?
6. If the pulley is at distance X from the tower hinge and b = 90, show that f T
becomes

p

L 2 þ X 2 2XL sin h

f T ¼ TL

mgl ¼ X

How can X be altered to reduce the foundation loads? Is this practicable?
7. If the tower centre of mass was above the tower when it is lying flat on the
ground, show that f T,max is unaltered but that f T is, in general, reduced.
8. If the mass of the gin pole is included in the analysis, show that f T,max is
increased if b \ 90.
9. The gin pole in Example 12.1 was made from 100 9 100 9 4 (all mm) steel
square hollow section of mass 11.6 kg/m length. Estimate the maximum gin
pole contribution to the cable tension and force on foundation during raising
or lowering.
10. The ASCE [ 12 ] guidelines state that Eqs. 10.11 and 10.12 also apply to
rectangular sections in compression. Determine whether the gin pole from
Exercise 12.9 will buckle during tower raising or lowering.
11. For the situation in Example 12.1, calculate the maximum pullout forces on
the cable pulley.

References

1. Kusiak A, Song Z (2010) Design of wind farm layout for maximum wind energy capture.
Renew Energy 35:685-694
2. Encraft (2009) The encraft warwick wind trials project. http://www.warwickwindtrials.
org.uk/2.html . (accessed 17 Mar 2010)
3. Serato AB, Victor R (2009) Effects of long-term dynamic loading and fluctuating water table
on helical anchor performance for small wind tower foundations. J Perform Construct Facil,
ASCE. doi: 10.1061/_ASCE_CF.1943-5509.0000013
4. Ziter BG, Lubitz WD (2010) Predicting hub-height wind speed for small wind turbine
performance evaluation using tower-mounted cup anemometers. Wind Eng 34:673-699
5. Istchenko R, Turner B (2008) Extrapolation of wind profiles using indirect measures of
stability. Wind Eng 32:433-438
6. Elmore AC, Gallagher R (2009) Using regional climate center data to predict small wind
turbine performance. Pract Period Hazardous Toxic Radioactive Waste Manage 13:14-19
7. Strack M, Riedel V (2004) State of the art in application of flow models for micrositing. German
Wind Energy Conf. http://www.dewi.de/dewi/fileadmin/pdf/publications/Publikations/s07_4_
strack.pdf . (accessed 30 Sept 2010)
8. Brunskill AW, Lubitz WD (2010) Development of an empirical obstacle wake model for
small wind turbine micrositing. AIAA Paper 2010-828
9. Lubitz WD (2009) Power law extrapolation of wind measurements for predicting wind
energy production. Wind Eng 33:259-271