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A study of the impact of terrain and turbulence on the performance and fatigue loading of small wind turbines

KC, AnupORCID: 0000-0001-7546-4350 (2020) A study of the impact of terrain and turbulence on the performance and fatigue loading of small wind turbines. PhD thesis, Murdoch University.

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Small wind turbines (SWT) are designed according to the international standard IEC 61400-2, which assumes the SWT experiences a set of standard wind conditions, developed through assumptions of flat terrain and normal turbulence models. In practice, other wind conditions can exist at SWT sites including winds, influenced by terrain, that feature speed and turbulence behaviour outside the set of standard conditions. This results in the turbines suffering operationally and structurally when operated in such terrains. In this study, wind conditions at two contrasting locations; one from built environment (Port Kennedy) and another from open terrain (Östergarnsholm), are analysed and benchmarked against the standard for comparison. The findings show that the longitudinal turbulence intensity (TIu) at Port Kennedy is higher than value estimated in the standard while the TIu at Östergarnsholm is within the standard’s estimate. These wind fields are used as inputs in the aeroelastic code, FAST, to investigate performance and loading of a 5 kW horizontal axis wind turbine. The findings suggest that elevated turbulence in Port Kennedy wind increases the output rotor power while the Port Kennedy wind also doubles the fatigue load on the turbine blades. The probability density function (PDF) of the wind speed increments reveal that the Port Kennedy wind shows the highest intermittency of turbulence at small timescales and this appears to manifest as higher intermittency of the rotor dynamic loads. The PDFs of rotor torque, thrust and blade flapwise bending moment all show increased likelihood of extreme events for the turbine operating in the built environment with reduced fatigue life than the same turbine operated in the open terrain. The conclusions are that the standard appears inadequate for SWTs sited in complex sites with non-standard wind conditions and requires modification to make it more inclusive of turbulent sites to assure their reliable deployment.

Keyword: small wind turbine, terrain, turbulence, intermittency, fatigue loading, FAST

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Engineering and Energy
Supervisor(s): Whale, Jonathan and Urmee, Tania
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