assumptions about the plant model design and a limited temperature data set impair the utility of the assessment. In addition, the committee considers the use of deep, cold water for air conditioning to be a potential use of this resource.

Recommendation: Any future studies of the U.S. OTEC resource should focus on Hawaii and Puerto Rico, where there is both a potential thermal resource and a demand for electricity (Chapter 5).

Recommendation: The OTEC GIS should be modified to display monthly resolution over a longer time period (at least a decade) to allow for evaluation of the thermal resource for the full seasonal cycle as well as for special periods such as El Niño and La Niña. Isotherm depths (at 1°C intervals) should be included in the database so other pipe lengths can be evaluated for OTEC and seawater air conditioning (Chapter 5).

Rivers and Streams

The theoretical resource estimate from the in-stream assessment group is based upon a reasonable approach and provides an upper bound to the available resource; however, the estimate of technical resources is flawed by the assessment group’s recovery factor approach (the ratio of technical to theoretical resource) and the omission of other important factors, most importantly the omission of statistical variation of stream discharge. Further work is required with respect to the approach to estimate the technically recoverable resource before it will have value as an estimate to guide in-stream hydrokinetic development.

Recommendation: Future work on the in-stream resource should focus on a more defensible estimate of the recovery factor, including directly calculating the technically recoverable resource by (1) developing an estimate of channel shape for each stream segment and (2) using flow statistics for each segment and an assumed array deployment. The five hydrologic regions that comprise the bulk of the identified in-stream resource should be tested further to assure the validity of the assessment methodologies. In addition, a two- or three-dimensional computational model should be used to evaluate the flow resistance effects of the turbine on the flow (Chapter 6).

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