The energy sector has been undergoing profound changes for several years. This development is expected to continue to meet growing needs while ensuring that the environmental impact is reduced. Many solutions are part of a policy of sustainable development and so-called “clean” energy. Among the promising alternatives, we find the river tidal turbine. What does it consist of? What are the advantages of this innovative concept
The operation of a river turbine is based on a principle similar to wind turbines. Where the latter capture the kinetic energy of the wind, tidal turbines use the same process to exploit the kinetic energy of the tides or, in the case of rivers, sea currents. Systems can stay afloat with an anchor point, or be placed below the surface. The turbine is at the origin of a mechanical movement which is converted into electrical energy. This then passes through the connection of a given electrical network. Depending on the needs and installation capacities, it is possible to adapt the size of the tidal turbines. These can be microgenerators for small rivers, or even generators capable of producing several megawatts for sites where the current is particularly important.
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Investments that enable the development of clean technologies
The principle has existed for several years, and was notably inspired by other hydraulic systems, such as dams or tidal power stations. However, the idea of adapting these devices to river networks came late. It was not until the mid-2000s that the first initiatives came to fruition. This renewable energy solution appeals to investors from both the private and public sectors. More than fifty concepts have emerged, even if these are mainly dedicated to seas and oceans. River turbines nevertheless tend to improve on various technical aspects:
- the consequences due to submerged or semi-submerged exposure;
- concepts of energy production;
- the use of composite materials resistant to marine environments, such as fiberglass;
- the resistance of mechanisms and systems taking into account high stress and cyclical movements.
Some sites are used to test different prototypes, particularly with regard to their performance, yield and economic viability. Environmental impact is also a notable evaluation factor.
Some examples of “life-size” tests for river tidal turbines
In France, there are several initiatives to try to democratize river tidal turbines. With this in mind, Hydroquest is initiating the Hydrofluv project. Along the Loire, Orléans is the base for carrying out a two-year trial. The system is installed on a floating barge in order to avoid heavy work. The estimated production would be 30 to 50 kWh depending on the current. On the Bordeaux side, the National Estuarine Experimental Site for the testing and optimization of tidal turbines (SEEENEOH) is located in areas of the Garonne closed to navigation. This project makes it possible to test river and maritime tidal turbines, in particular using currents between 1 m and 3.5 m per second, depending on a normal flow or a flood period. On the other hand, it is to be regretted the abandonment of the project born from the partnership between the Compagnie nationale du Rhône, Hydroquest and Constructions Mécaniques de Normandie. During 2019, the various service providers planned to install a pilot farm which would have accommodated nearly 39 tidal turbines. One of the main causes put forward is too great an operating loss for the Génissiat dam. Note that the region is planning the development of four tidal turbines near Caluire-et-Cuire.
What future for river tidal turbines considering its advantages?
The outlook for river turbines remains promising in the medium term. Some adjustments are to be expected in terms of layout and choice of sites in order to optimize the coordination of production of the different infrastructures. Technologies continue to evolve, offering ever more efficient systems. As it currently stands, the foundations have been laid, because this renewable energy solution uses non-polluting processes, and does not generate any waste in its operating phase. Additionally, the natural resource at the origin of the concept remains clean and abundant. We can also mention other advantages:
- the density of water makes it possible to set up smaller installations than wind farms to have equivalent power;
- development work linked to civil engineering is reduced;
- the visual impact is minimal, or even zero, if the tidal turbine is underwater;
- the predictability of ocean currents makes it possible to anticipate electricity production in the short term.
Globally, the river turbine sector would be able to produce 3,000 megawatts of electricity in the space of a year. This represents approximately a potential market of almost 10 billion euros. There is no doubt that this type of renewable energy is part of the solutions of the future to meet the growing consumption of countries. Given its numerous initiatives, France could act as a pioneer in terms of tidal turbine installations.
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