Wind turbine performance in high-alpine terrain as influenced by temperature, snow cover and turbulence

Analyses of wind turbine performance from high-alpine installations are scarce. We present characteristics of the power curve of one small wind turbine installed on a mountain shoulder near Lukmanier Pass and five large wind turbines located along the Gotthard Pass. On-site measurements are combined with LiDAR data to analyse the influence of turbulence intensity, temperature and snow cover on wind turbine performance. These conditions are known to vary strongly in alpine environments and to differ from typical installations at low elevations. Based on observational data, we aim to explain the seasonal characteristics and to verify the viability of mountainous regions for wind energy production. We find a small positive influence of highly turbulent winds at low wind speeds and show that the effect becomes negative at high wind speeds. At low wind speeds, very high turbulence intensity (>0.35) can partly counterbalance the effects of reduced air density. In this regime, small wind turbines profit most, as near-surface winds are typically more turbulent due to terrain-induced effects. In contrast, at high wind speeds, very low turbulence intensity (