Regional-scale quasi-periodic and random fluctuations of projected offshore wind energy in East Asia

Abstract

Developing offshore wind energy is an effective measure to mitigate the impact of human activities on climate change, in turn, offshore wind resources may be altered by climate change. This study investigates fluctuations of future offshore wind power density (WPD) in East Asia under typical emission scenarios. The spatial modes of WPD with random and quasi-periodic fluctuations are discussed using the regional windspeed dataset from 2010 to 2099. It shows that WPD would decrease amplitude and increase fluctuation intensity simultaneously. The amplitude of the highest energetic mode M1 with random fluctuation would decrease by 2.5% and the standard deviation of fluctuation intensity would increase by 13.5%. The spatial pattern of the annual fluctuating mode M2 reveals an opposite fluctuation phase between the regions located north and south of 30^° N, which is likely relevant to the large-scale atmospheric circulations. This suggests that offshore wind farm placements should be evenly distributed on both sides to mitigate the overall fluctuation in offshore wind power from the perspective of the entire nation of China. A novel fluctuation index serving as an indicator to consider the impact of regular periodic fluctuations of wind power density is further proposed. The distribution of the fluctuation index indicates that, under the high emission scenario Representative Concentration Pathways (RCP) 8.5, the high-fluctuation region expands, whereas the low-fluctuation region contracts, compared to the low-emission scenario RCP 2.6.