6. Other Technologies

6.1. Ocean Current

In addition to the tidal currents, caused by the gravitational pull of the moon and sun, there are also ocean currents. Unlike tidal currents, these ocean currents flow in one direction only and are relatively constant. Ocean currents are massive and complex circulatory systems. Some of these currents operate on an ocean scale; others, such as the great ocean conveyor belt, flow around the world. They are driven by a number of factors including: the effect of wind on the surface of the water; the effects of the sun heating the water in equatorial regions; the effect of salinity and density variations; and the effect of the Earth’s rotation (the Coriolis effect). Examples of ocean currents include the North Atlantic drift, the gulf stream and the Florida Straits current.

It is possible, as with tidal stream energy, to extract the energy from these currents to drive underwater turbines and produce electricity. The energy density of the Florida Straits current for example is about 1 kW/m2  (1). The technology used to extract energy from ocean currents is likely to be similar to that currently under development for tidal stream energy.

As with any project, the environmental implication must be taken into account. On the local scale there may be impacts on the marine environment (e.g. impacts on marine mammals from turning turbine blades). On a  global scale, slowing these currents by extracting energy from them may have a greater effect since ocean currents affect the climate. The great ocean conveyor belt, which is a deep water current, bring nutrient-rich water from the deep ocean to the surface where they are important for sustaining the marine ecosystems which are responsible for approximately 50% of the world’s photosynthesis(2).

 

References

1. U.S. Department of the Interior (2006) Technology White Paper On Ocean Current Energy Potential on the U.S. Outer Continental Shelf
[online] http://ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Current.pdf.

2. Behrenfeld, MJ, Randerson, JT, McClain, CR, Feldman, GC, Los, SO, Tucker, CJ, Falkowski, PG, Field, CB, Frouin, R, Esaias, WE, Kolber, DD, Pollack, NH. Biospheric Primary Production during an ENSO Transition. Science 291: 2594-7 (30 March 2001).

 

Further Reading

http://www.oceanenergycouncil.com/index.php/Ocean-Currents/Ocean-Current-Energy-FAQ.html

http://ocsenergy.anl.gov/guide/current/index.cfm

llp logoThis project has been funded with support from the European Commission (EU Lifelong Learning Programme Agreement no LLP/LdV/TOI/2009/IRL – 515). This publication reflects the views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

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