Anchor selection study for ocean current turbines

Abstract

This paper compares anchoring systems suitable for ocean current turbines, specifically those proposed to be installed off the coast of Southeast Florida near latitude 26° 5’ N. This location boasts one of the most energy dense ocean current resources, with a mean kinetic energy flux of approximately 2.34 kW/m2. Seafloor types ranging from unconstrained sediment to high relief ledges were observed during regional benthic surveys for which applicable anchor types would include deadweight, plate, pile, and drag embedment. Numerical simulations of single point moored marine hydrokinetic devices were used to extract anchor loading at a likely deployment location for mooring scopes from 1.25 to 2.0 and turbine rotor diameters between 3–50m. These anchor loading data were used for preliminary sizing of deadweight and driven plate anchors on both cohesionless and cohesive soils. Finally, the capabilities of drag embedment and pile anchors relevant to ocean current turbines are discussed. Multiple types of drag embedment anchors can support all of the predicted loads if adequate sediment exists and the loading is horizontal, while pile and H-type anchors can support all of the evaluated loading scenarios and chain-in-hole anchors can support turbines with rotor diameters up to 30m.