A successful roof-top wind power project?

Roof-top wind power projects have a well documented record of very poor performance. The primary objective of this project has been to provide advice in the planning phase of a roof-top wind project to ensure its success. As secondary objectives, this research has assessed the turbulence characteristics at a recommended site and evaluated the suitability of the small wind turbine design standard for roof-top installations. A monitoring mast was designed and installed on the roof-top of the Bunnings warehouse in Port Kennedy to measure the effect of turbine mounting height on average wind speed and wind turbulence intensity. As a consequence of this wind data analysis, planning applications were modified to increase the turbine height from 2m to 4m above the roof. This change is predicted to increase power output by a factor of four. The predicted capacity factor of approximately 9% at the site is low by commercial standards but compares favourably with published values for roof-top systems. The Class II Swift turbines proposed for the project are designed to withstand higher wind speeds than observed, but fatigue from high levels of turbulence (especially when the wind is from the southern sector) may reduce their safe operating life. At present, procedures for turbulence measurement and characterisation are not satisfactorily standardised in the small wind field. Various research groups apply a range of sampling rates and measurement intervals when calculating turbulence intensity, which can make comparison of results difficult. In the absence of a standard, a one-minute measurement interval is recommended and a method for calculating longer-interval turbulence intensity values from one-minute values is presented. An IEC task description (IEC TC88 MT2 Item 40) has also been proposed to help standardise the calculation of turbulence time-scales, length-scales, and power spectra. However, in its current form it does not provide sufficient detail to guarantee consistent and correct results