fetch to replenish the resource. This shadowing effect implies that one cannot estimate the theoretical resource as the sum of the wave power density over an area as one might do for solar energy. Note that the magnitude of this shadowing effect is likely to be highly dependent on the specific characteristics of the device (e.g., size, efficiency). Although there are some initial publications with rigorous analytical approaches for quantifying the effect of an arbitrary array of point absorber devices (e.g., Garnaud and Mei, 2010), shadowing effects due to actual devices are a topic of active research. The planning of any large-scale deployment of wave energy devices would require sophisticated, site-specific field and modeling analysis of the wave field and the devices’ interactions with the wave field. This step is essential to refine any estimate of theoretical wave resource into an estimate of the technical wave resource.
The wave resource assessment group from the Electric Power Research Institute (EPRI) and Virginia Tech was tasked by DOE with producing estimates of the potential wave resource in U.S. coastal waters. To estimate the theoretical wave resource, the assessment group utilized a hindcast of wave conditions that was assembled by the National Oceanic and Atmospheric Administration’s (NOAA’s) National Center for Environmental Prediction using WAVEWATCH III, a state-of-the-art global wave generation and propagation model. Although the model was recently expanded to introduce physical processes specific to intermediate and shallow water (dispersion and refraction), the version available at the time of the assessment was the deepwater version, restricting its validity in intermediate and shallow water. The accuracy of WAVEWATCH III predictions is relatively well outlined in the scientific literature; in particular, WAVEWATCH III is known to reproduce wave height quite well (Chawla et al., 2009). However, it was unclear to the committee how well the reconstructed spectra represented the observed spectra, especially because the spectral reconstruction was optimized only at deepwater stations. Model accuracy is questionable in water depth shallower than about 50 m.
The assessment group first addressed several potential issues related to the available hindcast (e.g., a data record of only 51 months and the lack of full spectral information at all grid points) and then generated parametric fits of wave frequency spectra for all points of interest. To produce maps of wave power density, it computed a sum of the power density associated with all spectral components at a given location, regardless of wave direction. This is equivalent to considering the wave energy flux (i.e., power density) impinging on a cylinder of unit diameter that extends over the entire water column. The total theoretical resource