Unlocking wind potential from the sea using remote sensing

Dr Merete Badger gave an insightful presentation on the use of satellite imagery in the mapping of offshore wind speeds and creating wind potential maps as part of the e-shape project. Understanding the wind potential at different sites is crucial for planning and development of offshore wind farms. Wind speed maps also aid in planning the installation of measurement stations, facilitates the analysis of wind farm operations, and supports decision-making for offshore wind farm planning. Using this data, Europe aims to install 450 GW of offshore wind turbines by 2050.

Using the Sentinel and ACAT satellite systems they provide an alternative approach by using synthetic aperture radar (SARS) and scatterometer to provide data on wind speeds and wind potential over a large area but less regularly. SAR and scatterometer data help map wind potential by analyzing sea surface roughness and scattering patterns. The traditional methods like metrological masts and laser instruments provide more regular data but for a much smaller geographic area. This requires the data to be modelled to provide sufficient coverage. These systems are also significantly more costly compared to the use of satellite imagery.

A comparison of the wind speed and potential data from satellite imagery with the more traditional methods shows that SAR and scatterometer data provides more detailed and higher resolution data than traditional measurements. This is achieved by calibrating the data from satellite imagery with ocean buoy observations to remove biases and improve the data quality. Although the wind speed data from satellite imagery is registered only within 10 metres above the sea level, using temperature data allows the imputation of the data to 100 metres above sea level

The advantage of the using satellite imagery is that wind speed maps can be generated within a few hours of accessing the data. The validation of the study with stakeholders showed the need for broader coverage of the seas, resulting in the expansion of the project to include data being acquired for the East Coast of the United States, the south China sea and the coastline of South Africa. The focus on South Africa highlighted the complexity of the wind climate in the country that is influenced by factors such as strong ocean currents, upwelling of cold water, and its unique topography. Using the SAR and scatterometer data, wind patterns and wind speed maps for the region were developed. In the case of Cape Town, is was observed that the wind is forced around the peninsula, resulting in speed-up effects that contributes to higher mean wind power density in certain areas.

Other factors, such as ships near the harbour and the presence of offshore wind farms, can also introduce artifacts in the wind speed measurements. The data shows that wind speeds offshore in South Africa are significantly higher compared to the land, emphasizing the potential for harnessing offshore wind energy in the region. Through ongoing projects and collaborations, efforts are being made to develop human capacity and use wind data to support the planning and implementation of wind farms in South Africa, thus contributing to the growth of renewable energy sources in the country.

Presently, the majority of South Africa’s wind energy capacity comes from onshore wind farms. Offshore wind projects are still in the early stages, with limited (or no) installed capacity. However, it’s important to note that the renewable energy landscape can evolve rapidly, and there may have be developments of offshore wind energy in South Africa in the near future. According to the South African Wind Energy Association (SAWEA), by the end of 2020, South Africa had a total installed capacity of approximately 2.5 gigawatts (GW) of wind power, none of which comes from offshore wind farms. 

To facilitate access the wind data and promote its usability, a dedicated portal was developed as part of the e-shape project. The portal serves as a user-friendly interface where stakeholders can easily access the wind data and associated products. Users can navigate the portal to explore wind speed maps, wind power density information, and other relevant parameters for specific regions of interest. The portal offers interactive features that allow users to select different levels, customize settings, and explore wind speeds at various heights.

In addition to the wind data itself, the portal also provides extensive documentation and demonstration videos to enhance user’s understanding and confidence in interpreting the wind maps. These resources help users gain insights into the wind climate of different areas and supporting them in decision-making processes related to wind farm development. By providing a comprehensive and accessible platform, the portal contributes to the dissemination of wind data and promotes the use of satellite-based and numerically modelled data for renewable energy planning and research purposes. 

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