Evaluating the gravity wave energy potential off the Brazilian coast

Abstract The wave energy potential on the Brazilian coast is estimated using in-situ buoy data and model data. The results present a greater potential on the southern-southeastern coast than on the northeastern coast, but the variance is also larger. These seem to be associated with the different atmospheric regimes. While in the northeastern portion the trade winds determine the wave regime, in the south the passage of cold front systems plays a major role. For almost all regions and throughout the year, the energy potential oscillates between 10 and 30 kW/m, the most efficient range to implement wave energy converters. The occurrence of sea states is also assessed, showing that the passage of cold front systems also creates different sea states in the S-SW area. Finally, the most common sea states and energy flux are estimated, showing a shift towards longer periods and higher waves for the latter. On the S-SW coast, although the most frequent sea states have waves with periods around 8 s, the energy flux has a more balanced distribution between these and the waves with periods around 11s, the common period for waves generated by cold front systems. This result shows that the most common sea state is not necessarily the one that should be considered when planning wave energy converters for the region.

摘要 本研究利用原位浮标数据（in-situ buoy data）与数值模式数据（model data），估算了巴西沿岸的波浪能资源潜力（wave energy potential）。结果显示，南东南部沿海的波浪能资源潜力高于东北部沿海，但能流变异程度也更大。上述现象与两类迥异的大气环流型（atmospheric regimes）密切相关：东北部海域的波浪场受信风（trade winds）主导，而南部海域则以冷锋系统（cold front systems）过境为核心影响因素。几乎所有区域全年的波浪能资源潜力均在10~30 kW/m区间内波动，该区间正是部署波浪能转换器（wave energy converters）的最优效率范围。本研究同时评估了海况（sea states）的发生频次，结果表明冷锋系统过境同样会在南西南（S-SW）海域引发差异化海况。最终，本研究估算了最频发海况与能流（energy flux）特征，发现能流的主导周期向更长周期偏移，且对应波浪更高。在南西南沿海区域，尽管最频发海况的波浪周期约为8秒，但能流在该周期与约11秒的波浪（冷锋系统催生的典型波浪周期）间分布更为均衡。该结果表明，在为该区域规划波浪能转换器时，不应仅以最频发海况作为参考依据。