Thursday, September 1, 2011

Tidal-power engineering

Electricité de France (EDF), the national French electricity authority, has purchased a series of four giant tidal-energy turbines, which will be towed out into the sea off Brittany, to the north of Paimpol and the Ile-de-Bréhat, and lowered onto the sea floor.

These huge turbines are manufactured by an Irish company in Dublin named OpenHydro.

[Click the image to access their website]

Each circular turbine has a diameter of 16 meters, and will be installed on a tripod posed on the sea floor. The combined weight of a turbine and its base is 850 tons, which means that the structure is unlikely to move around.

For the moment, tidal turbines of this kind remain an experimental technology. On the other hand, France was a world pioneer in a related domain: the installation of tidal turbines in a barrier across the mouth of an estuary.

Opened in November 1966, the Rance tidal-power station in Brittany was the first such system in the world. Today, the station is still perfectly operational, and it produces electricity at three-quarters the cost of nuclear energy.

Obviously, to exploit this source of energy, you need to be located in a part of the world with a powerful tidal system. This is the case in Brittany and Normandy… where there's a well-known local saying about the tide going out "at the speed of a galloping horse". Personally, before becoming acquainted with the coasts of these two French provinces, I had never encountered the phenomenon of ports that simply lose all their water when the tide is out. I was amazed to discover vast beaches of dry sand covered in boats propped up on their sides with wooden poles.

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