The importance of local winds in wave energy resource assessment

Levi Kilcher1, Zhaoqing Yang2, Gabriel García-Medina2 and Aidan Bharath3, (1)National Renewable Energy Laboratory, Golden, CO, United States, (2)Pacific Northwest National Laboratory, Richland, WA, United States, (3)National Renewable Energy Lab, Golden, CO, United States
Theoretical resource assessments provide an estimate of the total energy available for conversion to perform useful work, and are a critical first step in understanding the value proposition of a type of renewable energy. Theoretical wave energy resource assessment at regional and national scales has traditionally involved a line-integral of the wave energy flux that arrives at the coastline of interest. While this approach has been widely accepted and adopted by the international community, it has generated questions regarding the amount of energy that is added to the wave field inshore of the chosen line (i.e., a hypothetical wave energy array). In this work we introduce a method for addressing this question by adding a ‘local’ resource component to the ‘remote’ resource (i.e., the traditional line-integral of wave flux). The local resource is calculated as an area integral of all wave energy source and sink terms from Wavewatch III’s ST4 package, except for the losses associated with wave-breaking and bottom friction at the coastline. When this approach is applied to small areas, the local component makes a small contribution to the total resource. However, when applied to large areas such as the entire U.S. Exclusive Economic Zone — as we do in this work — the local component is similar magnitude to the remote, and results in a 30% increase in the nation’s wave energy resource compared to previous estimates. In this presentation we provide an overview of the approach, a summary of the details of minimizing double-counting between the two components, a regional breakdown of the results, and a brief summary of the frequency dependence of the components.