A modeling assessment of nearshore wave resource of Hawaii, USA

Ocean waves represent a great amount of clean renewable energy that could be harvested to power systems from a commercial grid scale to small stand-alone applications such as enhancing the coastal resilience of remote communities. This study presents a modeling assessment of the wave resource around Hawaii based on a 32-year wave hindcast covering 1979-2010. These long-term wave hindcasts were generated using the unstructured version of SWAN, nested in a multi-resolution Wavewatch III model at regional to global scales. The unstructured mesh developed for this study has a spatial resolution of 300 m at the coastline and is relaxed to 5 km in deep water, across a domain that covers the full exclusive economic zone (EEZ). Wind forcing was obtained from ~5 km resolution WRF model simulations nested into NOAA’s CFSR hindcast. Model validation was performed for in-situ buoy measurements and an altimeter derived dataset. Typical linear correlation coefficient for significant wave height at the buoys exceed 0.9 and biases are within 20 cm. Extensive sensitivity analyses were conducted during model setup to evaluate the effect of mesh resolution and the tradeoff between model iterations and time step, along with implications on wave propagation speed and the garden sprinkler effect. Detailed wave energy assessment is performed for the nearshore regions and sites of interest such as the Wave Energy Test Site in Oahu, closely following the IEC standards. In addition, wave climate characteristics are discussed around the islands in the context of large-scale climate variability. Finally, inter-annual and seasonal variations of the wave characteristics are presented.