To assist in the development of mooring and foundation solutions for ocean current based electricity production, an overview of the resource and seafloor characteristics in three potential power production regions are presented. These regions are offshore Florida USA, North Carolina USA, and South Africa. Maximum measured flow speed off both the USA and South Africa were around 3.0 m/s and maximum temporally averaged energy densities were between 2.0 - 3.0 kW/m2. Water depths at considered locations range from 60-400 m, and bottom type varies greatly. Most evaluated locations contain occasional flow reversals and occasions when current speed approached 0.0 m/s (only locations near the core of the Gulfstream off SE Florida did not measure either event). While low current events are undesirable from energy production and mooring design perspectives, they might provide unique opportunities to install or maintain equipment.
The kinetic energy in ocean currents, or marine hydrokinetic (MHK) energy, is a renewable energy resource that can help meet global energy requirements. An ocean circulation model-based census shows that subtropical surface western boundary currents (WBCs) are the only nearshore, large-scale currents swift enough to drive large electricity-generating ocean turbines envisioned for future use. We review several WBCs in the context of kinetic energy extraction. The power density in the Gulf Stream off North Carolina at times reaches several thousand watts per square meter at 75 m below the surface, and the annual average power is approximately 500-1,000 W m −2 . Significant fluctuations occur with periods of 3-20 days (Gulf Stream meanders) and weeks to months (Gulf Stream path shifts). Interannual variations in annual average power occur because of year-to-year changes in these WBC motions. No large-scale turbines presently exist, and the road to establishing MHK facilities in WBCs will encounter challenges that are similar in many aspects to those associated with the development of offshore wind power.
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