An investigation of the impact of wind speed and turbulence on small wind turbine operation and fatigue loads

Abstract

This paper investigates the operation and loading of a 5 kW HAWT using the aeroelastic code FAST. Wind data from built environment site at Port Kennedy (PK) and from a flat terrain site in Östergarnsholm (OG), are analysed and compared with IEC 61400-2. The longitudinal turbulence intensity (TI u ) in the PK wind field was 22%; which was higher than the estimated value in IEC 61400-2 Normal Turbulence Model. The TI in the flat terrain (OG) was below 18% for all mean wind speeds. The selected wind conditions from the two locations were used as input in FAST simulation to investigate the performance and loading of the turbine. The elevated turbulence in PK wind fields increased the output rotor power which was more than that predicted by the standard. Similarly, PK wind field also showed higher blade root flapwise bending moment resulting into twice as much damage load on the turbine blades due to large short-term fluctuations in both wind speed and direction. This value for OG was below the standard's prediction. We observe that the current IEC standard seems inadequate for urban siting of SWTs and requires modification for more reliable deployment in turbulent sites.

An investigation of the impact of turbulence intermittency on the rotor loads of a small wind turbine

“…Such turbulent flow fields demonstrate highly intermittent statistics and has a higher probability of larger wind fluctuations and occurrence of more extreme events than that predicted by the current IEC 61400-2 Gaussian wind model [8,9]. This work is the continuation of the authors' previous study [10] on the impact of wind speed and turbulence on the performance and fatigue loads of a SWT. This study is motivated by the structural challenges faced by SWTs operating in built-up areas due to small-scale fluctuations or 'turbulence intermittency' happening within the wind field due to the influence of terrain.…”

“…Wind data sampled at 10 Hz for a period of 6 months are considered from both sites. Readers are directed to the author's previous work [10] for more information on the wind measurement campaigns in these locations and the obtained results with one-point statistics of averaged mean wind speeds and their standard deviations. The incremental PDF of their wind speeds and their shape parameter, 2 The data, at each selected bin as shown in Figure 1, contains only the ten-minute records in chronological order having the mean wind speed values that lie within the chosen bin.…”

“…Full description of this publically available FAST model and the methodology for the FAST simulations can be found in [38]. Methodology on preparing the input data sets in TurbSim and executing FAST simulations of the Aerogenesis turbine is detailed in the author's previous study in [10].…”

Technological and Operational Aspects That Limit Small Wind Turbines Performance

“…Urban environments have more turbulent intensity effects than open terrains. The impact of turbulence in the wind generation system is considered during the SWTs design process; if not, power generation estimation will not be correct and structural components may fail during the operation [63]. Some works that present cases in which the SWTs are evaluated under the cited standard are listed below.…”

“…Similarly, KC et al [63] compared the standard IEC with simulated behavior of HAWT operated in turbulent urban terrain and focused on the effects on the power output and fatigue loads. The wind profile was based on measurements in two different places, Port Kennedy (Australia) and an open area in Östergarnsholm (Sweden).…”