Horizontally Oscillating Hydrofoil-River-Turbine with Variable Immersion Depth

Motivated by the unused hydrokinetic potential of smaller European rivers and creeks we develop a horizontally oscillating hydrofoil turbine to exploit those resources. Based on the work of T. Kinsey and Prof. G. Dumas of the Laval University, Canada, on vertically oscillating hydrofoils we adapt and improve the technology to the resources especially given in the country of Luxembourg in inner Europe. Currently, the energy of rivers is mainly harnessed and transformed in electricity by the well-known barrage type of hydropower plants. This type of hydropower plant becomes harder to implement, since the protection of the natural river flow and the protection of fishes and other animals becomes more important in Europe (see also Recovery of the European Eel Stock). The passage through an ordinary barrage turbine can lead to “very high mortality, notably on migrating silver eels”. Therefore other technologies have to be used to harness the still available rivers energy, namely hydrokinetic turbines. The field of hydrokinetic river turbines is in the beginning to evolve and first projects were implemented in the United States and Europe, harnessing large rivers and tidal currents. But there are fewer approaches available for smaller rivers with varying flow conditions, since the current propeller based concepts need a certain river depths and speed to generate electricity. Furthermore, it could be useful to implement controllable turbines, so that they serve the consumers need but do not lead to peaks in an energy systems balance, which have to be damped with other technologies, for example storages or throttle processes in thermal power plants. The hydrokinetic turbine, presented in this paper is fully controllable; its angle of incidence and its oscillation frequency can be controlled. The advantage of the full control of the motion of the moving hydrofoil is an improved efficiency of the power extraction from the seasonal but also daily varying flow conditions of smaller creeks. Furthermore we can answer with a varying power output to the altering consumers need. We can generate the power needed, once the dependence between oscillation frequencies, variation of the angle of incidence and the power output is derived. Operating the system, fixed to a raft, hold at a position floating on a river, we can also answer to the varying depth of the hydro resource. A simple mechanism can vary the immersion depth of the hydrofoil and adapt the harnessed flow cross-section to the current river conditions. This mechanism enables the new turbine concept to harness currently not useable hydro resources, which were limited by their minimum water depth. Furthermore the system can be protected from dangerous flood conditions with this lifting and lowering mechanism. We expect that we can contribute with this horizontally oscillating hydrofoil-river turbine to a higher share of hydropower generation in the field of micro generation. We are aiming on a concept which is modular (consisting of low kW range single modules) and can be adapted to the rivers size and the consumers’ needs. We will present the specifications of our idea which is currently on the way to be setup in our lab, to prove the controllability and want to present the physical restrictions and potentials for several flow conditions.

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