Currents- a Driving Underwater Force to Harness

Like the wind, sea currents provide a huge source of power. Underwater turbines can generate electricity. This technology is currently being tested in many regions of the world.

Underwater turbines
© Idé

Potential that is Still Being Investigated

The movement of the oceans - partly caused by the tides - is a significant driving force.

While speed is low (10-20 kph), the key to recovering energy from waves is the flow and density of the moving water (compared to air). Underwater turbines recover energy.




Underwater turbines are large helixes tethered in rows to the seabed or floating mid-water. A direct current cable conveys output to a land-based electricity transformer station connected to the power grid.

The movement of the oceans is a significant driving force.

The energy produced is a natural, inexhaustible source of energy with no greenhouse gas emissions; and its flow can be quite steady if it is harnessed in the right location.  That said, other than construction difficulties there are a number of drawbacks. They are as follows:

   • Building the facility and maintaining the underwater turbines is extremely expensive

   • Seawater-related corrosion to equipment and suspensions

  • Trawler fishermen are against them- they claim that the turbines compete with their fishing areas

   • Environmental constraints

   • The need to access the facility for maintenance operations and for connection to the grid.

To date, there are no industrial-scale facilities. However, a number of demonstration models are currently being developed.

In Europe, the potential of underwater turbines is estimated at 18-35 TWh per year¹ (about 8% of annual energy consumption in French homes). The United Kingdom, France, and Norway are the best placed countries to benefit from these currents. A number of projects are underway in Norway, Scotland, and Northern Ireland.

In Norway², the Hammerfest strait facility has been operational since September 2003. It has the following features:

   • Current speed: 1.8 m/s (6.5 kph)
   • Depth: 50 m
   • Capacity: 300 kW
   • Turbine diameter: 20 m
   • Height of system: 30 m

In France, the Paimpol-Brehat site was chosen in 2008. It has potential installed capacity of 1.5-2 MW and expected output of 3GWh per year. It will become operational in 2012.

Florida could cover 35% of its electricity needs with marine currents

True. 8km off the Florida coast, the flow of the current is 30-130 Mm³⁵ per second and its speed is 1.5 m/s or 5.4 kph. Using just one thousandth of this potential would cover 35% of Florida's electricity needs (200 TWh per year) - 5% of total US needs!
After a number of aborted projects, one of which dates back to the 1980s⁶, Florida Atlantic University's Centre of Excellence in Ocean Energy Technology was established in 2006⁷. It is currently developing an underwater turbine farm using 20 kW turbines. Each turbine has a helix with three blades measuring
3 meters in diameter, connected to a floating barge anchored with a cable.

[1] http://www.nanodata.com/sdn76/epr3/doc/analyse-energie-des-mers.pdf p.6
[2] http://www.inter-mines.org/docs/0904140804PR_090319_DeLaleu.pdf p.30
[3] http://www.inter-mines.org/docs/0904140804PR_090319_DeLaleu.pdf p.14
[4] http://www.wind-eole.com/fileadmin/user_upload/Downloads/Offshore/Rencontres_du_Havre/session7/Cyrille_Abonnel.pdf
[5] Millions of cubic meters
[6] http://www.inter-mines.org/docs/0904140804PR_090319_DeLaleu.pdf p.52
[7] http://www.inter-mines.org/docs/0904140804PR_090319_DeLaleu.pdf p.53