Date of Award

Summer 2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Ocean and Earth Sciences

Committee Director

John Klink

Committee Member

Chester E. Grosch

Committee Member

Malcolm Scully

Call Number for Print

Special Collections LD4331.O35 K35 2011

Abstract

The effect of arrays of wind turbines on circulation in the coastal ocean is analyzed with a coastal numerical model applied to a shallow coastal area like the Mid Atlantic Bight (MAB). A simplified model domain is specified with a linearly deepening shelf along a straight coastline. The initial density structure is a quasi-two layer situation with a sharp thermocline. Wind stress in most of the cases is either upwelling or downwelling favorable with constant amplitude continuing after a smooth start. There are two cases where oscillating wind forcing is used. Simulations consider wind arrays having different widths, different locations offshore, different alongshore extents and different efficiencies of extracting wind energy.

Reduced wind stress within the turbine array creates changes in the surface Ekman transport which drives secondary circulation due to Ekman convergence or divergence at the edges of the array. The location of the array relative to the normal location of the wind driven alongshore jet affects the ocean response. An array that is well offshore of the wind driven jet has an initially weak but continually growing effect. A near-front boundary array has a peak disturbance after 2-4 days which decays to a weaker response. An offshore array affects the depth of the thermocline through vertical motion at the array boundaries. An array in the wind-driven jet affects the speed of the jet and its location (to a lesser extent). Turbine arrays larger than the internal radius of deformation produce a larger effect (by a factor of 3) compared to smaller arrays. More efficient turbines produce a larger reduction in wind stress within the array and thereby a stronger ocean response. Finally, turbine arrays that have reduced alongshore extent have a much smaller response compared to a long strip of turbines.

Upwelling and downwelling favorable winds have opposite water column temperature response due to the original circulation in each case which affects the inner shelf stratification. During upwelling a weak stratification is maintained in the inner shelf and consequently the closer the array is to the coast the larger the temperature change. The opposite occurs in case of downwelling favorable wind because the inner shelf is unstratified.

The ocean responses to the offshore array may be beneficial if the secondary circulation increases transport of nutrients to the surface, acts to collect and hold larvae, and accumulates sediment due to the reduced flow and turbulence within the array. These various effects are projected to occur based on the simulations presented here.

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DOI

10.25777/fe89-vx14

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