81. Atmospheric Stability Effects on Small Wind Turbine Power Collection in a Complex Terrain

The power performance assessment of a small wind turbine (SWT) based on atmospheric stability is reported herein. An experimental setup was used to study a 2.1 kW SWT in a suburban environment, where 1 Hz power collection data and 20 Hz turbulent flux measurements were obtained. The dataset consists of 4287 h of raw data covering a 6-month period. The measured International Electrotechnical Commission-based (IEC) power curve shows an average performance 30 % above the manufacturer’s curve, but with decreasing power output close to the rated wind speed. Values relating power collection increase at low wind speeds with high turbulence levels concur with previous studies. The Obukhov length was used as a stability parameter, and stability-dependent power curves were compared with the measured average. Above 8 m/s, unstable conditions were predominant and evidenced the decreasing power tendency, where turbulence intensity (TI) was unable to give consistent results. The results reported in this chapter validate an approach suitable for SWT assessment using a physical parameter as a classification criterion, which better explains the power collection behaviour close to rated conditions.