129 research outputs found

    Hybridization of a RoR HPP with a BESS—The XFLEX HYDRO Vogelgrun Demonstrator

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    In the XFLEX HYDRO Vogelgrun demonstrator, a run-of-river hydropower plant, the hybridization of one turbine-generator unit with a battery energy storage system is being investigated. This paper describes the integration methodology of the hybrid control algorithm without replacing the existing speed governor of the unit. Furthermore, the comparison of the performances of a non-hybrid and hybrid unit is discussed, and first experiences gained during the operation and monitoring of the hybrid operating mode are presented.This work has been realized with the participation of INES.2S. David ValentĂ­n and Alexandre Presas acknowledge the Serra HĂşnter program. The corresponding author would like to express his gratitude to Nicolas Ruchonnet for his contributions during the revision.Postprint (published version

    Water saving options in hydropower by means of variable speed operation: a prototype study in a mid-head Francis turbine

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    Nowadays, in order to mitigate the global warming effects, there is a need of renewable energy generation for the objective of carbon neutrality. In this context, hydropower plays a key role not only because the amount of renewable energy generated but also because it is a fundamental player to ensure the stability of the electrical grid, as one of the main dispatchable sources. Nevertheless, hydropower is facing nowadays with the climatological problem of the extreme droughts, that are expected to be more common in the upcoming years. Therefore, it has become more important than ever to use the water flowing through the rivers properly. In this paper, the potentiality of using variable speed operation with the aim of increasing the overall efficiency of Francis turbines, which are the most widely used hydro turbines worldwide, is numerically explored. This implies to use less water to produce the same amount of electrical power. The study is based on an accurate modelling with real prototype data which has been made available for this study. It is shown that variable speed could improve the overall efficiency of the unit with respect to the constant speed generator, typically used in hydropower. While this idea has been mentioned in some previous studies, in this paper we also consider the electrical efficiency decrease of the variable speed technologies and restrictions of the unit regarding the electrical power generated. Results show that when the unit operates at some specific operating conditions, namely low heads at part load operations and high heads at maximum power, variable speed technologies could be used to save more than 2% of water with respect to the fixed speed unit. Main results and models of this paper can be used as a reference for future studies with similar type of units.First of all, Authors would like to acknowledge XFLEX Hydro [20]. This study is a direct output of the technologies being studied in this project. The Hydropower Extending Power System Flexibility (XFLEX HYDRO) project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 857832. Alexandre Presas would like to acknowledge, Nicolas Hugo from ALPIQ, Thomas Hildinger from VOITH and Josep Bordonau from UPC for his expertise and valuable comments regarding the FSFC and DFIG models and also Jo˜ao Delgado for his valuable contributions and ideas during part of this project. Alexandre Presas and David Valentín acknowledge the Serra Húnter program of Generalitat de Catalunya.Postprint (published version

    Diagnostics of a hydraulic turbine failure

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    This paper presents the failure analysis and diagnostic of a hydraulic turbine. Shortly after a maintenance revision the thrust bearing of the turbine was destroyed when the turbine was put into operation. The damaged bearing was examined and the possible causes discussed. To identify the problem that led to the failure of the thrust bearing, a comprehensive on-site measurement campaign was done. Vibrations, pressures, temperatures and operating parameters were acquired at different operating conditions of the turbine. The analysis of the data allowed to determine the source of the problem and to implement a solution.The authors would like to thank the company Endesa GeneraciĂłn and the XFLEX HYDRO 2020 research and innovation program under grant agreement No 857832FLEX.Peer ReviewedPostprint (published version

    Analysis of the mode shapes of Kaplan runners

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    To prevent lifetime shortening and premature failure in turbine runners, it is of paramount importance to analyse and understand its dynamic response and determine the factors that affect it. In this paper, the dynamic response of a Kaplan runner is analysed in air by numerical and experimental methods. First, to start the analysis of Kaplan runner mode shapes, its geometry is simplified and modelled as a bladed disk. Bladed disks with different blade numbers are investigated, by numerical simulation, in order to understand the influence of this parameter on its modal characteristics. Then, mode shapes extracted are characterized and a classification is proposed. Second, an existing Kaplan runner is simulated by Finite Elements Method (FEM) and its mode shapes are extracted. The obtained results are contrasted with the bladed disks mode shapes, in order to validate the classification proposed. The simulated Kaplan runner is also experimentally studied. A numerical modal analysis is carried out in the real runner. Different, global and local, mode shapes are identified. The global mode shapes extracted by numerical and experimental modal analysis are compared and discussed. Finally, the local mode shapes identified are commented and explained by means of numerical simulation.Peer ReviewedPostprint (published version

    Benefits of battery hybridization in hydraulic turbines. Wear and tear evaluation in a Kaplan prototype

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    Kaplan turbines are nowadays used to provide Frequency Containment Reserve (FCR) to the grid due to their fast capacity to regulate their power maintaining high efficiency. However, this continuous power regulation increases the wear and tear of the regulation system considerably. To reduce the amount of movements in the regulation servomotors, and thus their wear and tear, a new technology is being investigated within the frame of the European project XFLEX Hydro. This new technology is based on hybridizing the hydro unit with a small size battery in parallel, this one being in charge of compensating the small frequency fluctuations in the grid by providing or absorbing power. In this paper, the benefits of the implementation of this new technology are evaluated. A Kaplan turbine prototype located in Vogelgrun, France, has been hybridized and different parameters have been monitored while the unit was working in hybrid mode and in normal standalone hydro mode. Wear and tear of the regulation system have been compared for both hybrid and standalone hydro modes. A reduction of about 25% in servomotors mileage and of 50% in fatigue damage have been obtained by hybridizing the unit.Peer ReviewedPostprint (published version

    Hybridization in Kaplan turbines. Wear and tear assessment

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    In the current energy market, hydraulic turbines are increasingly demanded to work in Frequency containment reserve (FCR) mode to compensate the constant frequency fluctuations in the electrical grid. To do so, hydraulic turbines change their generating power continuously which implies to regulate the flow rate. Kaplan turbines are double regulated machines that change the position of both guide vanes and runner blades to regulate the flow rate maximizing their efficiency. Therefore, guide vanes and runner blades are continuously moving when they provide FCR, leading to high wear and tear of the regulation system components. Within the frame of the European project XFLEX Hydro, a new technology to reduce the wear and tear of the regulation system in FRC have been implemented. This technology consists in the hybridization of the unit with a battery system. In that way, the battery is the one in charge of providing part of the power fluctuations to the grid, reducing the movements of guide vanes and runner blades of the turbine. The battery system was successfully installed in August 2021 in one unit of the Vogelgrun powerplant, in France. Since that moment, the unit has been working in hybrid mode. A monitoring system was installed in the power plant in two different units, the one hybridized and another without hybrid system. Several sensors were installed and different parameters were measured simultaneously to calculate the wear and tear of the different components. In this paper, a comparison between the hybrid mode and the standard mode (non-hybrid) is performed in terms of mileage and wear and tear of the guide vanes and runner blades servomotors.The authors would like to acknowledge the XFLEX project and the partners involved in WP9. Special thanks to EDF for their implication during the installation of the monitoring system and the tests. David ValentĂ­n and Alexandre Presas would like to acknowledge the Serra HĂşnter program too.Peer ReviewedPostprint (published version

    Failure investigation of a solar tracker due to wind-induced torsional galloping

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    Solar power installations are increasing every year due to the decarbonization policy established around the world. Photovoltaic (PV) systems and specifically one-axis solar trackers are the most used type of installations in solar power plants. Those solar trackers are slender structures installed in open-air areas sometimes subjected to high speed winds. During the last years, failures in these structures are starting to appear, and most of them are related to a dynamic phenomenon called torsional galloping. The torsional galloping is an aeroelastic instability that presents very high deformation amplitudes and can be triggered at certain wind speeds and tilt angles of the solar tracker. In this paper, a failure investigation of a solar tracker due to torsional galloping is carried out. The broken structure has been analyzed in the field and a numerical model of the structure has been built up. The numerical model is used to identify the natural frequencies of the structure as well as the maximum stresses in the different pieces of the solar tracker. The numerical investigation confirmed that the cause of the failure was torsional galloping occurring for high speed winds and with a tilt angle of the solar tracker of 0 degrees.Postprint (updated version

    Determination of the natural frequencies of a prototype Kaplan turbine

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    The natural frequencies of a turbine can be calculated from numerical methods. By comparing these natural frequencies with excitation sources, one can know the danger of a resonance and a possible failure in a component of the turbine. Therefore, it is often very important to have an accurate numerical model of the turbine to determine these natural frequencies. There are not many publications on the determination of the natural frequencies of reduced-scale models of Kaplan turbines. More papers exist for pump turbines or Francis turbines. For real Kaplan turbines, very few experiments can be found to determine mode shapes and natural frequencies. In this paper a Kaplan turbine of 37MW (maximum power), 12.5m (maximum head) and 50 m3 /s (maximum flowrate) was tested. The turbine was equipped to determine the natural frequencies of the runner in air. For this purpose, one accelerometer in each blade of the runner was installed and a total of 16 impacts were done in each blade. Frequencies and mode shapes were obtained. In parallel, a numerical model was obtained. Numerical and experimental results were compared and an accurate numerical model is presented. With this numerical model the natural frequencies of the runner in water were calculated.This research activity is framed within the context of the XFLEX HYDRO project. The project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 857832. No. 857832).Peer ReviewedPostprint (published version

    On the use of vibrational hill charts for improved condition monitoring and diagnosis of hydraulic turbines

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    To cope with the intermittent power supply of the new renewable energies and demand fluctuations, Francis turbines are required to operate more and more in an extended operating range, far away from the design point. With this operating behavior, it is very complex to interpret the trend of vibration parameters typically used in Condition Monitoring and to define reasonable alarm and trip levels valid for all the operating range of the unit working in steady conditions. As in the efficiency curves of Francis turbines represented as a function of net head and load (Hill Chart), in this paper we propose to represent the most relevant vibration parameters in surfaces, called Vibrational Hill Charts, which allow a more accurate evaluation of the indicators and their trends and a better classification of abnormal values. To show the potential of Vibrational Hill Charts, a complete database obtained after 2 years of monitoring a large Francis Unit (444 MW rated power) has been used. The mapping of the relevant vibration parameters has been performed by means of Artificial Neural Networks. It is shown that by setting the action levels based on the resulting maps, rather than a constant value, a better diagnosis capacity is achieved as the Receiver Operating Characteristic will be improved. Furthermore, phenomena such as erosive cavitation, which is hard to be detected, could be also assessed with the use of multidimensional analysis based on the Vibrational Hill Chart. As a conclusion, with the Vibrational Hill Chart, the condition monitoring and diagnosis of hydraulic turbines could be improved.Postprint (author's final draft

    Natural frequencies of rotating disk-like structures submerged viewed from the stationary frame

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    To understand the effect of rotation in the dynamic response of pump-turbine runners, simplified models such as disk-like structures can be used. In previous researches the natural frequencies and mode shapes of rotating disk-like structures submerged and confined have been analysed from the rotating frame. Nevertheless to measure these parameters experimentally from the rotating point of view can be a difficult task, since sensors have to withstand with large forces and dynamic loads. In this paper the dynamic response of rotating disk-like structures is analysed from the stationary frame. For this purpose an experimental test rig has been used. It consists on a disk confined that rotates inside a tank. The disk is excited with a PZT attached on it and the response is measured from both rotating frame (with miniature accelerometers) and from the stationary frame (with a Laser Doppler Vibrometer). In this way the natural frequencies and mode shapes of the rotating structure can be determined from the stationary reference frame. The transmission from the rotating to the stationary frame is compared for the case that the rotating structure rotates in a low density medium (air) and in a high density medium (water).Peer ReviewedPostprint (author's final draft
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