DecoWind: Development of low-noise and cost-effective wind farm control technology

Abstract

DecoWind is a 3-year Danish research project whose goal is to devise advanced control strategies for wind turbines and farms for minimizing their acoustic impact. Noise propagation models (Nord2000 and WindStar) are verified through dedicated measurement campaigns onshore. Long-range offshore measurements are also conducted to understand these specific conditions. A Parabolic Equation method for noise propagation, which have mostly been restricted to academic use in the past, is integrated into an engineering context for wind farm control. This framework can be used to define a wind farm optimal control strategy. The energy production is maximized while limiting the noise impact at dwellings, depending on the considered site, by operating the turbines using their different noise operational modes. This framework is demonstrated through numerical test-cases. In addition, a public survey is conducted to assess the socio-acoustical impact of wind turbine noise, looking at several factors. The ultimate goal is to produce a set of recommendations regarding wind turbine noise regulations that would connect the new engineering design capabilities and the findings regarding public annoyance. The project is a collaboration between DTU, Siemens-Gamesa Renewable Energy, FORCE Technology, and EMD International. In this contribution, the main achievements of the project are summarized.

Physics-based scintillations for outdoor sound auralization

“…For example, Daigle et al (1983) reports a maximum value of the saturated standard deviation of no more than 6 dB, corresponding to r 2 v;sat % 0:48. This value agrees quite well with the theoretical result p 2 =24, obtained for optics (Hill and Clifford, 1981), but it is rather far from the value (approximately 0.8) found by the recent measurements made by Bertagnolio et al (2020).…”

“…However, for longer paths, the wavefront has been already randomly distorted and, thus, the variation of the refractive index is less effective in producing the log-amplitude fluctuations. Wenzel (1975) formulated a model for the prediction of the saturation distance which showed a rough agreement with measurements (Bertagnolio et al, 2020;Daigle et al, 1983). We found discrepancies in existing literature regarding the saturated value for the variance, r 2 v;sat .…”

“…( 7) with f ¼ 0 and limiting its value to r 2 v;sat ¼ 0:8. The height of the source is set to 109 m to replicate the measurements of Bertagnolio et al (2020). Considering the uncertainties related to the atmospheric conditions, a good agreement can be observed between Fig.…”

“…However, it is necessary to limit the value of the correlation function to avoid nonphysical log-amplitude fluctuations. We suggest limiting the value of the variance to r 2 v;sat ¼ 0:8, following the experimental results of Bertagnolio et al (2020). It should be noted that more measurements are necessary to confirm this value and obtain a more precise estimate.…”

Wind farm noise prediction and auralization

“…Regarding noise emission, the optimization process would significantly benefit from simulation tools that can precisely predict noise levels emitted by wind turbines under specific circumstances. Consequently, extensive research has been conducted in recent years to create and enhance these simulation tools [2][3][4][5][6][7][8]. Additionally, there has been a growing need to auralize wind turbine noise to facilitate the exploration and comprehension of noise annoyance mechanisms.…”