of awareness of some of the physics driving their resource assessments, which led to simplistic and often flawed approaches. The committee was further concerned about a lack of rigorous statistics, which are essential when a project involves intensive data analysis.

A coordinated approach to validation would have provided a mechanism to address some of the methodological differences between the groups as well as a consistent point of reference. However, each validation group (chosen by individual assessment groups) determined its own method, which led to results that were not easily comparable. In some instances, the committee noted a lack of sufficient data and/or analysis to be considered a true validation. The weakness of the validations included an insufficiency of observational data, the inability to capture extreme events, inappropriate calculations for the type of data used, and a focus on validating technical specifications rather than underlying observational data. The lack of consistent, effective validation is especially problematic given the large uncertainties described in assessment results.

All five MHK resource assessments lacked sufficient quantification of their uncertainties. There are many sources of uncertainty in each of the assessments, including the models, data, and methods used to generate the resource estimates and maps. Propagation of these uncertainties into confidence intervals for the final GIS products would provide users with an appropriate range of values instead of the implied precision of a specific value, thus better representing the approximate nature of the actual results.

The GIS database products themselves also reflect an apparent lack of coordination in their development, which led to duplication of effort and additional time needed to integrate the final products. At the time of this writing, the wave and OTEC databases are the only MHK resource assessments integrated into the National Renewable Energy Laboratory’s (NREL’s) MHK Atlas; the in-stream resource assessment is hosted separately in the NREL River Atlas. The tidal resource database is currently hosted by the tidal resource assessment group and will be integrated with other NREL products; however, the visualization and analysis tools developed by the assessment group will not be implemented in the MHK Atlas. Given that one of DOE’s objectives is to compare the various MHK resources with one another and with other renewable energy resources, stronger initial coordination among the assessment groups could have led to products developed in a common format.

LIMITATIONS ON COMPARISON OF EXTRACTABLE MHK RESOURCES

The different approaches taken by the resource assessment groups left the committee unable to provide the defensible comparison of potential



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