A Multi-Point Meso–Micro Downscaling Method Including Atmospheric Stratification

• Published in: Energies (Basel) Vol. 14; no. 4; p. 1191
• Main Authors: Buhr, Renko, Kassem, Hassan, Steinfeld, Gerald, Alletto, Michael, Witha, Björn, Dörenkämper, Martin
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2021
• Subjects: Atmospheric stratification; Climate; Climate models; complex terrain; Computational fluid dynamics; Computer applications; Critical flow; downscaling; Energy; Fluid dynamics; Hydrodynamics; Mesoscale phenomena; Methods; micro-scale simulations; Regions; Scale models; Simulation; Time series; Velocity distribution; wind energy site assessment; Wind farms; Wind power; Wind shear
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en14041191

In wind energy site assessment, one major challenge is to represent both the local characteristics as well as general representation of the wind climate on site. Micro-scale models (e.g., Reynolds-Averaged-Navier-Stokes (RANS)) excel in the former, while meso-scale models (e.g., Weather Research and Forecasting (WRF)) in the latter. This paper presents a fast approach for meso–micro downscaling to an industry-applicable computational fluid dynamics (CFD) modeling framework. The model independent postprocessing tool chain is applied using the New European Wind Atlas (NEWA) on the meso-scale and THETA on the micro-scale side. We adapt on a previously developed methodology and extend it using a micro-scale model including stratification. We compare a single- and multi-point downscaling in critical flow situations and proof the concept on long-term mast data at Rödeser Berg in central Germany. In the longterm analysis, in respect to the pure meso-scale results, the statistical bias can be reduced up to 45% with a single-point downscaling and up to 107% (overcorrection of 7%) with a multi-point downscaling. We conclude that single-point downscaling is vital to combine meso-scale wind climate and micro-scale accuracy. The multi-point downscaling is further capable to include wind shear or veer from the meso-scale model into the downscaled velocity field. This adds both, accuracy and robustness, by minimal computational cost. The new introduction of stratification in the micro-scale model provides a marginal difference for the selected stability conditions, but gives a prospect on handling stratification in wind energy site assessment for future applications.