methods and level of detail in the resource assessment studies do not constitute a defensible estimate of the practical resource that might be available from each of the resource types.

While the Department of Energy (DOE) may want an aggregated value for internal research and/or investment purposes, such as comparing the relative sizes of individual MHK resources or comparing the MHK resource base with other renewable resources, a single-number estimate of each theoretical or technical MHK resource is of limited value for understanding the potential extractable energy that each resource might contribute to U.S. electricity generation.

DOE contracted for assessments of extractable MHK resource levels. The five resource assessments focused mainly on the national level and did not reach the point of estimating the practically extractable resource in regions of high interest. Both the theoretical and technical resource bases are developed by summing all the energy available over large tracts of ocean or long river stretches. However, attempts to tap wide swaths of ocean or coastal straits and embayments for harvesting energy will run into challenging social or economic barriers (e.g., entrenched uses such as fisheries and shipping lanes or environmentally sensitive areas) as well as technology, materials, and engineering issues (e.g., proximity to utility infrastructure, survivability). The tidal assessment group’s identification of relevant socioeconomic factors is a good beginning for this type of analysis.

Recommendation: Should DOE (or any other federal agency or regional/local decision-making body) decide to assess or support decisions on the potential practical MHK resource for specific regions of high potential MHK opportunity, it should include the best available socioeconomic and environmental filters for that region.

Inevitably, some of these theoretical and technical resource estimates include large areas where the energy density is so low that energy development would be impractical. Such practical limits will undoubtedly affect the power available from all MHK resources, but some resources may be more significantly reduced than others, and the resource with the largest theoretical resource base may not necessarily have the largest practical resource base. Thus, it is not apparent that comparing the theoretical or technical resources of the various MHK types is of any real value for determining the potential extractable energy from MHK. Rather, it is the practical resource that will ultimately contribute to U.S. electricity generation. To ascertain the practical MHK resource, site-specific analysis is necessary. Because the assessment groups were tasked by DOE to



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