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Novel methods of increasing the storage volume at Pumped Storage Power plants
Pal-Tore Storli 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.3
The paper presents two novel concepts of increasing the energy storage capacity at pumped storage power plants, both existing and new projects. The concepts utilize compressed air as a working medium to displace water from a volume originally not available for storage. The concepts are likely to give additional storage volume at a low cost, however, much development and many investigations are needed before the concepts can be shown to be technical and economical feasible solutions for energy storage. The concepts are disclosed so that researchers and utilities can start those investigations, hopefully helping the green transition by providing highly valuable energy storage for a future renewable energy having a much higher share of renewable energies than the current systems.
Novel methods of increasing the storage volume at Pumped Storage Power plants
Storli, Pal-Tore Korean Society for Fluid machinery 2017 International journal of fluid machinery and syste Vol.10 No.3
The paper presents two novel concepts of increasing the energy storage capacity at pumped storage power plants, both existing and new projects. The concepts utilize compressed air as a working medium to displace water from a volume originally not available for storage. The concepts are likely to give additional storage volume at a low cost, however, much development and many investigations are needed before the concepts can be shown to be technical and economical feasible solutions for energy storage. The concepts are disclosed so that researchers and utilities can start those investigations, hopefully helping the green transition by providing highly valuable energy storage for a future renewable energy having a much higher share of renewable energies than the current systems.
Numerical Generation of Hill-Diagrams; Validation on the Francis99 Model Turbine
Erik Tengs,Pal-Tore Storli,Martin Aasved Holst 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.3
This article compares a numerically simulated, and an experimentally obtained Hill-Diagram. The Francis99 model turbine was used in the validation. By using steady-state simulations and passage modeling in ANSYS CFX, the simulation time is in the order of minutes for each operating point. Except for the smallest guide vane opening, the error in hydraulic efficiency is less than 2.5% for all flow configurations. The individual error in head and torque follow clear, almost identical trends. The error along a line of small incidence losses indicate less than 0.5% error in the efficiency in almost the complete simulated range. The results in this article may be used in future optimization design processes using Hill-Diagrams.
Ellingsen, Rakel,Storli, Pal-Tore Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.2
In the Nordic grid, a trend observed the recent years is the increase in grid frequency variations, which means the frequency is outside the normal range (49.9-50.1 Hz) more often. Variations in the grid frequency leads to changes in the speed of rotation of all the turbines connected to the grid, since the speed of rotation is closely related to the grid frequency for synchronous generators. When the speed of rotation changes, this implies that the net torque acting on the rotating masses are changed, and the material of the turbine runners must withstand these changes in torque. Frequency variations thus leads to torque oscillations in the turbine, which become dynamical loads that the runner must be able to withstand. Several new Francis runners have recently experienced cracks in the runner blades due to fatigue, obviously due to the runner design not taking into account the actual loads on the runner. In this paper, the torque oscillations and dynamic loads due to the variations in grid frequency are simulated in a 1D MATLAB program, and measured grid frequency is used as input to the simulation program. The maximum increase and decrease in the grid frequency over a 440 seconds interval have been investigated, in addition to an extreme event where the frequency decreased far below the normal range within a few seconds. The dynamic loading originating from grid frequency variations is qualitatively found by a constructed variable $T_{stress}$, and for the simulations presented here the variations in $T_{stress}$ are found to be around 3 % of the mean value, which is a relatively small dynamic load. The important thing to remember is that these dynamic loads come in addition to all other dynamic loads, like rotor-stator interaction and draft tube surges, and should be included in the design process, if not found to be negligible.
The Rotor-Stator Interaction Onboard A Low Specific Speed Francis Turbine.
Einar Agnalt,Bjørn Winther Solemslie,Pal-Tore Selbo Storli,Ole Gunnar Dahlhaug 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2
Over the last years, several breakdowns in hydropower plants with low specific speed Francis runners have been reported. One of the main excitation forces in such runners is the pressure fluctuations originating from the rotor stator interaction. In this paper, the rotor-stator interaction has been analyzed utilizing pressure sensors onboard the runner. The pressure sensors were flush mounted in the hub of the runner and the signals were transmitted through a slip-ring system. The measurements have been analyzed relative to the runner angular position by utilizing an angular position sensor mounted to the shaft end. Measurements with different guide vane angle have been compared in order to study the potential flow interaction and the viscous wake effects for the pressure inside the runner. The results from the onboard pressure measurements found that the phase of the guide vane passing pressure seen by the onboard pressure sensors was independent of the guide vane opening. Hence, the potential flow interaction was found to be the dominant effect and no evidence from the viscous wake effect was found on the onboard pressure.