Interest in converting the kinetic energy of ocean current and tidal flow into electrical power has increased in recent years. This report focuses on the ocean current resource in Hawaii, which includes tidal flows as well as uni-directional oceanic current flows around the main Hawaiian Islands, with the exception of Kauai, from the shoreline to approximately the 2000-m depth contour.
The study's objectives were to evaluate ocean current resources around the main Hawaiian Islands, assess the present state of underwater turbine development, and determine the potential applicability of that technology to the resource in Hawaii. Preliminary literature reviews indicated that technology presently under development would probably not be applicable to Hawaii due to insufficient current flow speeds. Consequently, particular care was taken to identify technologies that might be applicable to relatively low current speeds.
The project team's assessment of the ocean current resource includes a discussion of the driving forces for currents in the Hawaiian Islands and the factors that result in localized variations in the currents. A state of the art circulation model developed by the University of Hawaii that simulates tide-driven currents around the Hawaiian Islands was used to develop contour plots of the ocean current resource. Available information from past current studies was used to validate the model results.
Underwater turbine technology was evaluated based on an extensive literature search that included both written reports and Internet sources. This search was supplemented by follow-on contact with technology developers identified in the search. A primary objective of the literature search was to find evidence of promising technologies that might make generation of electrical power by underwater turbines feasible in Hawaii.
The report introduces the topic of ocean current resources in Hawaii with a review of available information from past studies. Because there are large sectors where no circulation information is available and a more comprehensive assessment of tidal current resources is needed, a numerical model was applied to the Hawaiian Islands and validated using existing available current data. The report details the tidal results from this model for potential ocean current power generation. Complementing this resource evaluation, the report describes the present state of underwater turbine technology and discusses the applicability of TISEC (Tidal In-Stream Energy Conversion) technology to Hawaii.
Application, Value and Use
Many firms have plans for relatively ambitious future tidal power projects. Although the number of these projects indicates a high degree of interest in tidal power, commercial application of underwater turbine technology is still in the development stage.
A comparison of the required speeds for efficient turbine operation with the available resource in Hawaii leads to the conclusion that, given the present technology, generation of electrical power with underwater turbines is not feasible at the present time. A significant, and at this point unforeseen, technological advance will be necessary to make the generation of electrical power by underwater turbines feasible in Hawaii.