Résumé

The need to decarbonize our energy production push us toward the use of renewable sources such as solar, wind and hydraulic energies. These renewable energies often suffer from intermittences which requires flexibility from the dispatchable energy producers to respond to power changes and to ensure a stable electrical grid. For this specific purpose, the European project XFLEX HYDRO is focusing on the hydropower sector, with seven demonstrators in three different countries to determine the advantages of variable- and fixed-speed turbine, smart control, and hybrid batteryturbine systems. Among these seven demonstrators, the hydropower plant of Caniçada operated by EDP consists of two fixed-speed vertical Francis turbines with a medium head of approximately 100 meters and a total installed power of 70 MW. The objective of this demonstrator is to assess the potential of a variable speed technology to increase the lifetime of the turbine. For this purpose, we investigated here in a first time the hydraulic behaviour of the machine when operated at part load conditions with a fixed runner speed to find the operating condition generating the maximum pressure fluctuations. In a second time, we analysed the advantages of variable-speed capabilities regarding this operating condition. The study is carried out with CFD analysis using ANSYS CFX and the SST turbulence model. The results show a clear amelioration of the pressure fluctuations on the runner with variable speed however mitigated with a lowering of efficiency for this operating point.

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