be exploited, the cubic power of v demonstrates the advantage of deploying turbines in regions of strong ocean currents. As the density of water is approximately 850 times that of air, a marine turbine in an ocean current of 1 m/s can theoretically produce as much power as a wind turbine with the same swept area A in a wind with a wind speed of 9 m/s.2

Similarly, the drag on an ocean current device due to the higher water density is likely to result in forces on the marine turbine that are greater than that on a wind turbine. This can present significant engineering challenges. As mentioned in Chapters 2 and 7, problems with corrosion may also be significant for marine turbines, though this is also a consideration for offshore wind turbines. The reduction in turbine performance from biofouling of marine turbines may be more significant than the loss of performance caused by blade pitting due to dust particles and insects.

PROJECT DESCRIPTION

Based on presentations given by the ocean current resource assessment group,3,4,5 the ocean current energy assessment is being conducted using two different approaches: (1) estimation of the total ocean current technical resource around U.S. coastal waters from the Pk method, which used the predicted undisturbed flow field output from an ocean model (see Chapter 2, “Estimate of Available Tidal Power,” for more discussion on Pk), and (2) estimation of the total available power within the Gulf Stream by incorporating extra dissipation to represent energy extraction into theoretical models of the Gulf Stream western boundary current. Work using the first approach has been mostly completed,6 but investigation of the second approach was not complete when this report was written.

In the first approach, the theoretical resource (kinetic power density) and the technical resource (Pk) are calculated using velocity fields generated

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2 It should be noted that a wind turbine deployed in an area with 9 m/s wind speed is likely to sweep out a much larger area than 100 m2.

3 K. Haas, H.M. Fritz, Z. Defne, and X. Yang, Georgia Tech Savannah; S.P. French and X. Shi, Georgia Tech Atlanta; V.S. Neary, P. Schweizer, and B. Gunawan, Oak Ridge National Laboratory, “Assessment of energy production potential from ocean currents along the United States coastline,” Presentation to the committee on September 27, 2011.

4 K. Haas, H.M. Fritz, Z. Defne, and X. Yang, Georgia Tech Savannah; S.P. French and X. Shi, Georgia Tech Atlanta; V.S. Neary, P. Schweizer, and B. Gunawan, Oak Ridge National Laboratory, “Assessment of energy production potential from ocean currents along the United States coastline,” Presentation to the committee on December 12, 2011.

5 K. Haas, H.M. Fritz, Z. Defne, and X. Yang, Georgia Tech Savannah; S.P. French and X. Shi, Georgia Tech Atlanta; V.S. Neary, P. Schweizer, and B. Gunawan, Oak Ridge National Laboratory, “Assessment of energy production potential from ocean currents along the United States coastline,” Presentation to the committee on April 9, 2012.

6 See preceding footnote.



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