Marine Hydrokinetic Energy in the Gulf Stream Off North Carolina: An Assessment Using Observations and Ocean Circulation Models

Abstract

There has been global interest in renewable energy for meeting energy demands, and as these demands increase, it will become of greater importance to utilize low-carbon energy sources to mitigate anthropogenic impact on the environment. Onshore hydropower is responsible for half of the electricity generated by a renewable source in the USA. In the ocean, marine hydrokinetic (MHK) energy in western boundary currents (WBCs) can be considered for electricity generation by submarine turbines. WBCs are a continuous and sustainable source of energy that could be transmitted to shore to support coastal communities in future years. The Gulf Stream is the WBC of the North Atlantic subtropical gyre, and it flows for part of its course along the upper continental slope off the southeastern USA. This large-scale current has maximum flow speeds exceeding 2 m s−1, and this together with its proximity to the coastline distinguishes it as a potential source of MHK energy. Using current data from a moored acoustic Doppler current profiler (ADCP) and a regional ocean circulation model, MHK power densities offshore of North Carolina were found to average 798 W m−2 for the ADCP and 641 W m−2 for the model during a nine-month period at a potential turbine site, a difference of about 20%. The model was shown to have similar current speeds to the ADCP for slowly varying currents (fluctuations of weeks to months due to Gulf Stream path shifts), and lower speeds for higher frequency current variations (fluctuations of several days to a couple of weeks due to wavelike Gulf Stream meanders). This article considers the Gulf Stream as a prospective renewable energy source and assesses the power density of this WBC at multiple locations offshore of North Carolina. Understanding the Stream’s power density character, including its spatial and temporal variations along the North Carolina coast, is essential in considering the Gulf Stream as a future alternative energy resource.