Ocean current energy can be harnessed using underwater turbines, also known as tidal turbines, to generate power. This technology has potential in many regions around the world. However, projects are still in the experimental stages.
The Potential of Underwater Turbines
The movement of the oceans — partly caused by the tides — is a significant motive force. While the speed is relatively low (10 to 20 kilometers an hour), the key to recovering energy from currents is the flow and density of the moving water compared to the air.
Tapping one-thousandth of the Gulf Stream’s potential could in theory cover a third of Florida’s power needs.
In Europe, the potential of underwater turbines is estimated at 18 to 35 TWh per year, or about 8% of the annual energy consumption in French homes. The United Kingdom, France and Norway are the countries that are best placed to benefit from this potential.
Advantages and Disadvantages
Ocean current energy is steady and inexhaustible. Once the turbines have been installed, no direct greenhouse gas (ghg) Gas with physical properties that cause the Earth's atmosphere to warm up. There are a number of naturally occurring greenhouse gases... emissions are generated. However, it has several disadvantages:
- Equipment and suspensions corrosionThe gradual degradation of a material by a physical or physicochemical reaction... caused by seawater.
- Opposition from trawler fishermen, who claim that the turbines compete with their fishing areas.
- The extremely high cost of installing and maintaining underwater turbines.
Experiments are currently focusing on the use of underwater turbines, large propellers or turbines tethered in arrays to the seabed or floating mid-water. A direct current cable carries the electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... to an onshoreRefers to land-based oil exploration and production operations, as in "onshore seismic data acquisition" or "onshore drilling". transformer station connected to the powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... grid.
Demonstration models are currently being developed, including in Norway, Scotland and Northern Ireland.
- In Norway, the Hammerfest Strom device has been operational in Kvalund since September 2003. It is installed at a depth of 50 meters, with currents of 1.8 meters per second (6.5 kilometers per hour). The turbine measures 20 meters in diameter and has a capacity of 300 kW.
- In France, Paimpol-Bréhat2 was chosen as the site for a tidal farm in 2008. It has a potential installed capacityThe power generation capacity of a particular plant. It is usually expressed in megawatts (or sometimes even gigawatts)... of 1.5 to 2 MW and expected output of 3 GWh per year. After a series of onsite surveys, a second pilot farm is scheduled to be commissioned in summer 2015, with two turbines built in Cherbourg and Brest.
- In Florida, after a number of aborted projects, including one that began in the 1980s, a research center3 was set up in 2006. It is currently developing a tidal turbineA tidal turbine is a hydraulic turbine that is powered by natural ocean, tidal or river currents... farm using 20 kW turbines. Each turbine has a propeller with three blades, measuring 3 meters in diameter, connected to a large floating barge anchored with a cable. Eight kilometers off the Florida coast, the Gulf StreamA powerful, swift ocean current that originates in the Gulf of Mexico... flows at 30 million to 130 million cubic meters per second and its speed reaches 1.5 meters per second, or 5.4 kilometers per hour. Using just one-thousandth of this potential would cover 35% of Florida’s power needs.
(1) Inter-Mines Study - p51 (french only)
(2) Paimpol-Bréhat Project - EDF (french only)