The effect of wind direction shear on turbine performance in a wind farm in central Iowa

Abstract

Abstract. Numerous studies have shown that atmospheric conditions affect wind turbine performance; however, some findings have exposed conflicting results for different locations and diverse analysis methodologies. In this study, we explore how the change in wind direction with height (direction wind shear), a site-differing factor between conflicting studies, and speed shear affect wind turbine performance. We utilized lidar and turbine data collected from the 2013 Crop Wind Energy eXperiment (CWEX) project between June and September in a wind farm in north-central Iowa. Wind direction and speed shear were found to follow a diurnal cycle; however, they evolved differently with increasing wind speeds. Using a combination of speed and direction shear values, we found large direction and small speed shear to result in underperformance. We further analyzed the effects of wind veering on turbine performance for specific values of speed shear and found detrimental conditions on the order of 10 % for wind speed regimes predominantly located in the middle of the power curve. Focusing on a time period of ramping electricity demand (06:00–09:00 LT – local time) exposed the fact that large direction shear occurred during this time and undermined turbine performance by more than 10 %. A predominance of clockwise direction shear (wind veering) cases compared to counterclockwise (wind backing) was also observed throughout the campaign. Moreover, large veering was found to have greater detrimental effects on turbine performance compared to small backing values. This study shows that changes in wind direction with height should be considered when analyzing turbine performance.

Does the rotational direction of a wind turbine impact the wake in a stably stratified atmospheric boundary layer?

“…The rotational direction of a wind turbine rotor in an EBL without wind veer only exerts a minor influence on the wake behaviour, which is limited to the near wake. This minor impact is consistent with previous investigations by Vermeer et al (2003), Shen et al (2007), Sanderse (2009), Kumar et al (2013), Hu et al (2013), Yuan et al (2014), and Mühle et al (2017).…”

“…of the wind turbine blades, the flow moves the blades in one direction and is deflected away from them in the opposite direction. Studies investigating the effect of wind turbine rotors rotating in opposite directions, especially for wind farm optimization, show that the rotational direction has an impact on the wake structure of a wind turbine and therefore on the performance of a downwind turbine (Vermeer et al, 2003;Shen et al, 2007;Sanderse, 2009;Kumar et al, 2013;Hu et al, 2013;Yuan et al, 2014;Mühle et al, 2017). Further, in simulations, representing an array of wind turbines with a second row rotating opposite to the rotation of the first row, an increase in productivity was found in comparison to the co-rotating pair of turbines.…”

Changing the rotational direction of a wind turbine under veering inflow: a parameter study

“…Veer occurs on many nights both onshore (Walter et al, 2009;Rhodes and Lundquist, 2013;Sanchez Gomez and Lundquist, 2020) and offshore (Bodini et al, 2020(Bodini et al, , 2019. According to 2 years of meteorological tower measurements in Lubbock (Texas; Walter et al, 2009) and 3 months of lidar observations in north-central Iowa (Sanchez Gomez and Lundquist, 2020), veer occurs in well over 70 % of those stable boundary layer (SBL) occurrences (≈ 76 % in Walter et al, 2009, and≈ 78 % in Sanchez Gomez and. In the remaining 22 % (Sanchez Gomez and Lundquist, 2020) to 24 % (Walter et al, 2009), a backing wind occurs.…”

American WAKE experimeNt (AWAKEN)

“…More high-fidelity observations with direct measurement of wakes using remote sensing are now being used to augment data taken from wind farm SCADA systems. Remote-sensing measurements made in land-based wind farms have provided direct observation of wakes (e.g., Barthelmie et al 2006;Krishnamurthy et al 2017, and similar validation studies were also done for land-based scale turbines (Machefaux et al 2016), including the DOE Crop Wind Energy Experiment campaign, as published in Rajewski et al 2013;Rajewski et al 2014;Bodini, Zardi, and Lundquist 2017;Lee and Lundquist 2017;Muñoz-Esparza et al 2017;Sanchez Gomez and Lundquist 2020. Researchers have also found value in airborne and unmanned aerial vehicle observations that can be used to augment remote sensing (Kocer et al 2011;Reuder and Jonassen 2012;Wildmann et al 2014;Lundquist and Bariteau 2015).…”