Recommendation: DOE should ensure that spatial data resulting from the MHK resource assessments are readily and publicly available for use in siting and permitting decisions (Chapter 7).

DOE has already made progress by making data on the spatial distribution of the theoretical energy resources readily available and should continue to play an active role in the characterization of the resource base and in developing decision support tools that can help guide considerations toward areas that could be the most productive and feasible for development. An accessible spatial database of theoretical and technological MHK resources would provide substantial information on the location of high-priority sites.

LIMITATIONS ON COMPARISON OF EXTRACTABLE MHK RESOUSCES

DOE requests for proposals did not offer a unified framework for the efforts, nor was there a requirement that the contractors coordinate their methodologies. The differing approaches taken by the resource assessment groups left the committee unable to provide the defensible comparison of potential extractable energy from each of the resource types as called for in the study task statement. To do so would require not only an assessment of the practical resource base discussed by the committee earlier but also an understanding of the relative performance of the technologies that would be used to extract electricity from each resource type. Simply comparing the individual theoretical or technical MHK resources to each other does not aid in making such a comparison since the resource with the largest theoretical resource base may not necessarily have the largest practical resource base. However, some qualitative comparisons can be made, especially with regard to the geographic extent and predictability of the various MHK resources. Both the ocean current and OTEC resource bases are confined to narrow geographic regions in the United States, whereas the resource assessments for waves, tides, and in-stream show a much greater number of locations with a large resource base. As for predictability, while there is multi-day predictability for wave and in-stream systems, especially in settings where the wave spectrum is dominated by swells or in large hydrologic basins, the predictability is notably poorer than for tidal, where the timing and magnitude of events are known precisely years into the future. The OTEC resource in the United States has little day-to-day variability but, like in-stream, is seasonally dependent. However, location and variability are but two of the many factors that will determine what MHK



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