Identification of Climatological Representative Days in the Mid-Atlantic for High-Fidelity Offshore Wind Energy Modeling

The goal of reaching 30 GW of offshore wind energy by 2030 becomes more realistic with the continued approval of offshore wind energy areas by the Biden Administration. In the Mid-Atlantic, where wind energy projects are in the most advanced stages of development, there is increased research focus on the eventual interaction of these wind farms. These interactions, in the form of wakes and cluster wakes, or wakes from multiple wind farms, could have detrimental effects on power production and forecastability for downwind wind farms (Pryor et al. 2022, Golbazi et al. 2022, Rosencrans et al. 2023).

To help alleviate these issues, numerical simulations in the form of numerical weather prediction (NWP) and large eddy simulations (LES) can provide insight into when cluster wake situations may occur, but running such simulations can be expensive and difficult to run for multiple years. In this study, we leverage and build upon existing techniques in the literature (Fischereit et al. 2022) to identify climatologically representative days for wind energy areas in the Mid-Atlantic where conditions would promote cluster wake situations. We select meteorological variables (wind speed, wind direction, atmospheric stability, boundary-layer height, TKE) critical to understanding wind energy production and wake propagation. We then consider two different NWP datasets of varying spatial and temporal resolution: ERA5 provides data at hourly intervals from 1940 to present at 0.25 deg (31 km) spatial resolution (Hersbach et al. 2020), and the NOW-23 dataset provides data at 5-minute resolution for 21 years at 2-km spatial resolution (Bodini et al. 2020). Our first step is to compare these two datasets for an overlapping 21-year time period.

Initial results show that the required number of days to represent the long-term climate increases with each additional variable considered. In their study of the German Bight, Fischereit et al. (2022) found that they could represent the long-term wind and wave climate in a “near-perfect” way with ~ 180 days, by reaching a Perkins Skill Score (PSS) of 0.9; our investigation of the mid-Atlantic wind resource region with ERA5 and NOW-23 data suggests that we will need ~100 days to reach a PSS of 0.9 (Figure 1). As we expand our parameter space to include multiple variables, the number of required days will likely grow. These results will ultimately be used to select case studies to best represent cluster wake conditions that apply to this region for the lifetime of likely wind farms in this mid-Atlantic region.

Figure 1: Histograms of randomly selected day pairs (N) from the 21-year ERA5 record (2000-2020) for 100 m wind speed over the Vineyard Wind 1 wind energy area. The Perkins Skill Score (PSS) represents the agreement between the histograms of N and the climatology, where 0 is no agreement and 1 is perfect agreement.

References:

Bodini, N., M. Optis, M. Rossol, A. Rybchuk, and S. Redfern, 2020: US Offshore Wind Resource data for 2000-2020. https://doi.org/10.25984/1821404.

Fischereit, J., X. G. Larsén, and A. N. Hahmann, 2022: Climatic Impacts of Wind-Wave-Wake Interactions in Offshore Wind Farms. Frontiers in Energy Research, 10, 881459, https://doi.org/10.3389/fenrg.2022.881459.

Golbazi, M., C. L. Archer, and S. Alessandrini, 2022: Surface impacts of large offshore wind farms. Environmental Research Letters, 17, 064021, https://doi.org/10.1088/1748-9326/ac6e49.

Hersbach, H., and Coauthors, 2020: The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146, 1999–2049, https://doi.org/10.1002/qj.3803.

Pryor, S. C., R. J. Barthelmie, and T. J. Shepherd, 2021: Wind power production from very large offshore wind farms. Joule, 5, 2663–2686, https://doi.org/10.1016/j.joule.2021.09.002.

Rosencrans, D., J. K. Lundquist, M. Optis, A. Rybchuk, N. Bodini, and M. Rossol, 2023: Annual Variability of Wake Impacts on Mid-Atlantic Offshore Wind Plant Deployments. Wind Energy Science Discussions, 2023, 1–39, https://doi.org/10.5194/wes-2023-38.