The impact of sea breezes on offshore wind energy resources in Australia

The amount of offshore wind capacity has been growing rapidly on the global scale. In Australia, there is currently no installed offshore wind capacity, but this is projected to change over the coming decades following government targets. Therefore, it is important to assess how wind energy availability varies in coastal areas, to understand potential opportunities and risks of offshore wind in the context of the broader energy system.

A key mode of local wind variability in coastal areas is the sea breeze, associated with daytime differential surface heating of the land and ocean, and the resulting thermal circulation with onshore flow near the surface. Although the sea breeze has been characterised by previous studies at individual coastal sites, there has yet to be a robust assessment of occurrences across the broader region of Australia, due to a lack of observational data and generalisable identification methods. As a result, several aspects of the sea breeze and associated wind variations have remained unexplored, including in regions relevant for future wind energy generation.

Here, we use a km-scale atmospheric reanalysis to characterise sea breeze occurrences over Australia. We investigate the spatial and temporal variability in their occurrences, as well as potential impacts on offshore wind energy. This includes the development and application of a new method for defining sea breezes as objects from reanalysis output, using a diagnostic of atmospheric fronts.

We find that there is more wind energy available during the afternoon over offshore wind areas on days with a sea breeze identified, compared to other days during the summer. Sea breeze days also tend to have higher average regional energy demand compared with other days, likely due to warmer surface air temperatures over the land that provide sea breeze forcing and lead to enhanced electricity demand from cooling. However, the amount of offshore wind energy also tends to be lower in the morning on sea breeze days relative to other days, likely due to weak prevailing winds that are then opposed by the formation of the sea breeze. Finally, due to the role of the prevailing wind direction in sea breeze formation, there is an anti-correlation in occurrences between opposite-facing coastlines.

These spatial and temporal variations in offshore winds associated with the sea breeze suggests a potentially important source of renewable energy. The sea breeze is shown here to drive local winds during the late afternoon in the summer, when demand is often high, and solar resources are reduced, representing large potentially value in the energy system. In addition, anti-correlation in occurrences between opposite-facing coastlines suggests that a diversity of offshore wind farm locations could be beneficial for energy reliability.