Marine Hydrokinetic Energy from Western Boundary Currents

Abstract

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.

Assessing Hydrokinetic Energy in the Mexican Caribbean: A Case Study in the Cozumel Channel

“…Equation (3), presented by [60], was reformulated and then applied to obtain the energy generated by the turbines in specified operational site conditions. This type of calculation, applied to marine turbines, is described by [9], who considers it necessary to have the following data:…”

“…In 2014, the time series of the current velocity in the Gulf Stream-Cape Hatteras region, at a depth of 75 m, were recorded, giving an annual average power of 1000 W/m 2 (8.76 MWh/m 2 -year) [9]. In this paper, the authors then compared their data with numerical results obtained with HYCOM, finding that the average HYCOM speed was 3% greater than the field measurements.…”

“…There are eight main regions with an average kinetic energy flux of over 0.5 kW/m 2 , (HYCOM [8] data, 2009-2012, at a depth of 20 m); the South African coast (Agulhas Current), the southeast U.S. and Mexican coasts (Gulf Stream-Cape Hatteras, Florida current-Florida Straits and Yucatan current in Cozumel), Japan (Kuroshio current), Indonesia, Somalia, Brazil (Brazil Coastal Current), Madagascar (Madagascar Currents), and Australia (South West Rocks). At four of these sites, the direction of the current is persistent and there are no reverse flows: north of Madagascar, off part of the Brazilian coast, and Florida current and Yucatan current [9].…”

Marine Renewable Energy

“…A recent review by Bane et al (2016) characterized ocean western boundary currents with a particular focus on the Gulf Stream on the South Atlantic Bight where it passes relatively close to shore near Cape Hatteras, NC. Using a combination of observations from a moored acoustic Doppler current profiler (ADCP) and numerical simulations using ROMS, they estimated the mean current to be on the order of 1 m/s.…”

“…A worldwide survey of ocean currents using Hybrid Coordinate Ocean Model (HYCOM) simulations shows that the western boundary currents (WBCs) in the wind-driven subtropical gyres are essentially the only large-scale currents with flow speeds sufficiently fast to be considered for commercial installation of electricity-generating turbines Bane et al 2017). Almost all MHK energy is in ocean surface waves, tidal motions, and large-scale (non-tidal) currents.…”