Variabilidade sazonal e interanual dos ventos sobre o atlântico tropical sul e o potencial para energia eólica offshore na região Nordeste do Brasil

Abstract

The general objective of this work was to assess the seasonal and interannual variability of wind over the South Tropical Atlantic Ocean (ATS) and the offshore wind energy potential along the coastal region of Northeast Brazil (NEB) from 1988 to 2018, as well as to investigate how these variabilities affect energy generation. The quality of potential reference data for wind speed and significant wave height was also evaluated to assist in the implementation of offshore wind farms. Given the existing wind resources in NEB, analyzing variabilities and the quality of reference datasets is crucial, as it can provide valuable information for decision-makers during the planning of offshore wind energy projects. Data from the Copernicus Marine Service (CMEMS) reanalysis were used to assess the seasonal and interannual wind variation and estimate offshore wind potential, along with data from three metocean buoys to validate the CMEMS data. To analyze the effects of seasonal and interannual variability, the spatial distribution of average wind speed was performed using boxplot techniques. The relationship between wind speed and El Niño-Southern Oscillation (ENSO) events was also investigated, along with wind trend analyses using the Mann-Kendall test. For resource estimates, the density and capacity of offshore wind energy production were calculated, in addition to identifying exploitable areas and the impact of ENSO on the energy generation of an offshore wind farm undergoing environmental licensing. The quality control results for CMEMS data on wind speed and significant wave height showed correlations above 0.80 for wind speed, particularly in Porto Seguro, and above 0.91 for significant wave height, especially in Recife. Additionally, RMSE values reached a maximum of 1.37 m/s for wind speed and 0.16 cm for significant wave height. Variability analyses showed that the wind speed estimated at 100 m height in the ATS presents high seasonal and monthly variability, with higher speeds during JJA and SON, especially in coastal areas. During La Niña and El Niño events, wind anomalies ranged between -5 m/s and 5 m/s. Boxplot analyses revealed high wind variability, particularly along the northern coast of Northeast Brazil, while more eastern areas exhibited more stable speeds. Trend analyses showed statistically significant variations (p < 0.0001), mainly in the DJF, JJA, and SON quarters. In identifying exploitable areas for generation, approximately 71% of the total area had an energy density between 400 and 700 W/m², classified as "Very Good." In a case study for an offshore wind farm, the calculated energy density showed consistent values with other studies, estimating 420 W/m² and 497 W/m² from reanalysis and buoy data, respectively. The impact of ENSO on generation revealed a reduction of up to 50% during La Niña and an increase of 48% during El Niño. The results indicate that reanalysis data can be applicable in studies focused on offshore wind potential. Moreover, the analysis revealed significant seasonal and monthly variability in wind speed along the northeast coast of Brazil, with high potential from June to October. El Niño tends to increase wind speed, while La Niña reduces it. There was also a significant trend of increasing wind speeds between 1992 and 2020, suggesting the influence of climate change. The study emphasizes the importance of integrating these variations into the planning and operation of offshore wind farms.