Ocean Current Dynamics and Renewable Energy from the Agulhas Current

The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa. This analysis assesses its characteristics and suitability to generate power as a source of clean renewable energy. On a section of coastline some 400 km long, over a period spanning more than 5 years an extensive set of current measurements was obtained. These data confirmed that south-westward currents with a speed greater than 1.2 m s–1 occurred over more than 60% of the recorded time; such ocean current speeds compare very favourably to winds required for energy generation. These currents occurred at the continental shelf break in water depths around 100 m, in the upper 50 m of the water column. Occasional current slowdowns and reversals did occur, with the major influence coming from ‘Natal Pulses’, which are large-scale meanders in the Current that temporarily reversed the currents at the measurement sites. However, because of the surface temperature structure of the relevant water masses, such meanders can be identified in satellite imagery giving a few days advance warning of such current reversals. The characteristics of western boundary currents have been known for many years, but at Present, there is no operational system where this source of power is being utilised. It has tremendous potential for renewable energy generation, but is symptomatic of the many engineering challenges that still have to be solved to make such generation economically viable.