The environmentally friendly concept in terms of water quality represents a condition for developing hydropower plants all around the world. Since 2017, hydropower has represented more than 70% of all renewable energy production and it is essential for the integration of the other renewable sources of energy and for regulation of the grid. To maintain the “green” label concerning the dissolved oxygen level (6 mg DO/L), the energy suppliers should respond to environmental concerns about the operation of hydropower plants. In the context of sustainable development, the ecological degradation of rivers is unacceptable due to the implementation of a hydropower plant on the watercourse. For deep reservoirs or tropical regions, the oxygen level in the water downstream of the hydropower plants may be low and affect the aquatic life for many kilometers downstream. This paper presents a new aeration system for discharged water from hydropower plants that provides water aeration with minimum energy consumption. The influence of the aeration process on the turbine operation and efficiency is analyzed. Experimental measurements are carried out on site on a small Francis turbine. The influence of the aeration process on the turbine mechanical performances (vibration level and relative displacement) and hydraulic performances (turbine efficiency, power output, and pressure fluctuation) is analyzed. The results showed that the impact of the aeration device implementation and operation over the energetic characteristics of the turbine is in the efficiency measurements accuracy range. The aeration through this device did not influence the turbine operation (vibration, level, or pressure fluctuations).

A complex hydraulic facility is modelled in EPANET. The system consists in an underground high head Hydro Power Plant (HPP) and a Pumping Station (PS), operating in a pumped-storage hydropower scheme with three reservoirs. The complexity of the system is due to its unusual configuration, where the PS discharges the water directly into the HPP penstock. The PS is equipped with 2 × 10 MW pumps. The HPP is equipped with 2 × 75 MW Francis turbines. The simulations allow assessing the energy production and/or consumption in various scenarios, offering a tool to decision makers, to wittingly choose the operation mode of the facility.

Nowadays, hydraulic turbines are more often operated under off-design conditions due to the increase in intermittent energy production (wind and solar). In these operating conditions, dynamic phenomena in hydraulic circuit are observed, such as flow instabilities, secondary flows, vortex rope developed in the draft tube etc. These phenomena can lead to pressure pulsations and structural vibrations of the hydraulic turbine structure, that affect the hydraulic turbine performance and its lifespan. In the present paper a wall model, developed by Manhart et al. (2008), is used with the k-ω SST turbulence model to study numerically the pulsating flows which can occur in a hydraulic turbine during part load operation. The Manhart wall model considers the adverse pressure gradient and has the advantage of being used on a coarser mesh (dimensionless distance, y+, can result in values up to 5), leading to smaller simulation time and computational demands when compared to the general approaches. The numerical analysis is carried on using the open-source software, Code_Saturne, and considers a geometry that is similar to the draft tube of a hydraulic turbine.