Enhanced resource assessment and atmospheric monitoring of the research wind farm WiValdi

Abstract

Prior to the installation of wind turbines at the Krummendeich research wind farm (referred to as WiValdi) which is developed by the German Aerospace Center (DLR), we conducted measurements with a Doppler wind lidar (DWL) and a microwave radiometer (MWR) for 16 months, starting in November 2020. The remote sensing data was validated against radiosonde measurements in a short-term campaign in September 2021. We present a statistical analysis of wind speed, direction, shear and veer as derived from the DWL as well as static stability from temperature retrievals of the MWR in comparison to model results of the New European Wind Atlas (NEWA). The observational data from 2021 shows a higher occurence rate of winds from northwest in comparison to the longer-term statistics of NEWA (2011-2018). From the overall statistics, cases with the occurence of low-level jets (LLJ) are detected and separated. The LLJs appear in 49% of the observed nights and predominantly in conditions with seaward wind direction. The LLJ increases shear and veer in the rotor swept area and thus the potential loads significantly. Future research at WiValdi will allow to analyse the effects of such load cases on the wind turbines in detail.

Characteristics of the low‐level jets observed over Dunkerque (North Sea French coast) using 4 years of wind lidar data

“…The core speed distribution retrieved over Dunkerque (Figure 2) is very similar to the ones presented for the two inland sites that are located not too far from the North Sea; that is, Cabauw (Baas et al ., 2009) and WiValdi (Wildmann et al ., 2022): they all showed the same asymmetric shape, with peak values around 8 m·s −1 , though the inland speed distributions extended up to higher wind speeds. On the IJmuiden offshore platform, the core wind frequencies also peaked around 8 m·s −1 , but the shape of the distribution was different, with a larger number of strong wind values in the 10–20 m·s −1 range and the distribution's right wing extending up to 25 m·s −1 (Kalverla et al ., 2019).…”

“…In this section, we compare our results mainly with other studies performed in the North Sea area: on the inland sites of Cabauw (Baas et al ., 2009), WiValdi (Wildmann et al ., 2022) and Braunschweig (Ziemann et al ., 2020), on the offshore platforms of IJmuiden (Duncan, 2018; Kalverla et al ., 2017; Kalverla et al ., 2019) and FINO1 (Wagn er et al ., 2019a). Cabauw is located ∼50 km from the sea and ∼205 km to the eastnortheast from Dunkerque (Figure 1a); for wind profiling, the site was equipped with a 200 m meteorological tower and a radio‐acoustic sounding system; the LLJ climatology in Cabauw is very robust, as it relies on 7 years of wind profiles (Baas et al ., 2009).…”

“…Cabauw is located ∼50 km from the sea and ∼205 km to the eastnortheast from Dunkerque (Figure 1a); for wind profiling, the site was equipped with a 200 m meteorological tower and a radio‐acoustic sounding system; the LLJ climatology in Cabauw is very robust, as it relies on 7 years of wind profiles (Baas et al ., 2009). The WiValdi site is located ∼40 km inland and ∼560 km northeast from Dunkerque; a wind lidar covering the whole boundary layer was deployed there and 16 months of data were used to produce a first climatology of the jets (Wildmann et al ., 2022). The Braunschweig site is located way farther inland (∼170 km) also ∼560 km from Dunkerque but to the eastnortheast; it was equipped with a Doppler lidar reaching up to 500 m AGL; however, only observations from the three summer months were published (Ziemann et al ., 2020).…”

“…(2009) showed that southwesterly jets included the largest number of strong winds and that strong winds were associated with more elevated jets, so that we can suppose that southwesterly jets were generally more elevated in Cabauw too. Aside from the southwesterly mode, the jet core peaked respectively in the eastsoutheasterly and southeasterly directions at the WiValdi inland site (Wildmann et al ., 2022) and at the FINO1 offshore platform (Wagner et al ., 2019a), corresponding to cross‐coast offshore jets like the eastsoutheasterly and southerly modes in Dunkerque. This would correspond to eastsoutheasterly to southeasterly jets in IJmuiden, a direction that was actually rare in the jet core rose (Duncan, 2018).…”

“…In the North Sea region, previous LLJ studies were based on anemometer and Doppler lidar data from offshore platforms located about 40–90 km from the Dutch or German coast (Kettle, 2014; Kalverla et al ., 2017; Duncan, 2018; Wagn er et al ., 2019a; Møller et al ., 2020) or from inland sites located about 40–50 km from the Dutch coast (Baas et al ., 2009) or from the German coast (Wildmann et al ., 2022), or even farther inland in northern Germany (Ziemann et al ., 2020; Weide Luiz and Fiedler, 2022). This work aims at completing the knowledge of LLJs in the North Sea area by documenting their characteristics in a coastal area and at a site located at the southern edge of the North Sea, close to the entrance of the English Channel.…”