ENERGIE NAVY. The exploitation of the power of the tidal currents takes various forms. The one chosen by the Eel Energy is biomimetic : this is drawn from the energy of the undulation of a membrane immersed in a flow in a submarine. In full phase of experimentation, the startup was selected to join the 3Dexperience Lab, Dassault systèmes. Grégoire de Laval, the director of Development, tells us more.
All of the turbines are not large propellers submerged under the surface. The startup French Eel Energy has devised an alternative solution based on the movements undulating membrane in hi-tech. “The adventure started at the end of 2011, born of the work of Jean-Baptiste Drevet, who is a specialist in fluid-structure interactions“, reveals Grégoire de Laval, the director of Development. The machine therefore presents itself in the form of a succession of strips of carbon fiber and fiberglass, both sturdy, and flexible, coated with an elastomer, and that forms this membrane is attached to a tripod, which allows him to move only against the current. The vertical movements of the various elements under pressure of the moving fluid are then exploited to produce electricity. “The mechanical energy is recovered in three dimensions throughout the membrane, “he continued.
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Efficiency and lightness
A lot of time was initially spent in theoretical calculations and simulations. “But soon enough, there were prototypes of small dimensions tested in a bath tub !“, plays the director of development. “The advances that have been made by logical iteration : between 2013 and 2014, the work was done at the scale 1/20th, and then in 2015-2016 on a prototype at 1/6th, which is still 2.5 metres from the side and 10 kW of power“, reveals the specialist. This version of the water rippling is currently being tested at Ifremer, partner of Eel Energy, in its basin of Boulogne-sur-Mer. “We are testing this prototype with a team on-site. The tests are held approximately every two months, and then there are operations to improve on the design, the materials, the control command or the string converter, “says Gregory of Laval. “The performance is interesting, but, for the moment, we are limited to low currents, of the order of 1.5 meter per second. However, the power depends on the speed of the water“. The current measures focus on the bottom of the power curve. And the engineers are pleased to note that the tidal turbine delivers watts from the first movement of 0.4 m/sec.,”The results are encouraging, “quietly congratulates the director of Development.
Tidal membrane © Eel Energy
The machine at a scale of 1 to reach 15 meters long and wide, for a power to be expected of 1 MW in the middle of an ocean current of 3 m/sec (a little less than 11 km/h). The membrane and the converter will acknowledge a weight of 34 tons on the scale, to which must be added to the 200 tonnes of support that will serve as the foundation by gravity, preventing the force of the current causes the device. “The equipment is lighter than other tidal turbines tested“, note the director of Development of the Eel Energy. The models of Sabella or DCNS weigh between 450 and 900 tons, which complicates their handling. But the startup’s French is not yet at this stage of its development : “The next step will be to move technology from the lab, by the end of the year. It will be tested at sea. But there will not be a machine-size real before 2020“. The water could then be deployed, probably in Scotland, on an experimental site dedicated to the marine renewable energy that brings together a dedicated infrastructure, divers with specific skills and specialized vessels handling. The French site SEM-REV would not be the marine current suitable for the operation of the machine.
Still a lot of work of numerical simulation to conduct
By then, the work of 3D modeling and simulation will continue, with the help of Dassault systèmes, who will host the Eel Energy in its 3Dexperience Lab. A recognition that will “accelerate the design and testing of our prototypes, “and that will allow the company to “share her experiences in modeling with other startups, “says Gregory of Laval. Annular, helical, planing or undulating, tidal turbines do not have a finished floor engineers. The estimated potential energy generation from tidal currents amounted to 450 TWh/year in the world, of which 10 TWh/year in France. Their advantage is to be predictable, localized, and regular, unlike the resources of wind, to achieve a load factor of 50 % against 25 % for wind turbines.
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