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.

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.

Simulations of the Dynamic Load in a Francis Runner based on measurements of Grid Frequency Variations

Pål-Tore Storli,Rakel Ellingsen 한국유체기계학회 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 Tstress, and for the simulations presented here the variations in Tstress 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.

Simulations of the Dynamic Load in a Francis Runner based on measurements of Grid Frequency Variations

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.

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.

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.

동통에 대한 사정

Frances Storlie, R.N 이화여자대학교 간호과학대학 1978 이화간호학회지 Vol.- No.12

동통을 정확히 사정하기 위해서는 몇가지 논리적인 단계가 필요하다. 우리들은 일상생활을 해 나가는데 있어 기둥에 엄지 발가락을 채였다거나. 요리할 때 손가락을 베는 등 흔한 동통을 경험해 보았을 것이다. 또한 질병에 동반되는 관절이나 근육의 통증. 허리의 불편감 같은 확실하게 표현하기 어려웠던 경험도 기억할 것이다. 동통을 지각하는데는 상해나 질병의 종류에 따라 차이가 난다. 피부나 표면에서 생기는 것은 예리하고 뜨끔하며 주의를 집중시키고 그 부위를 쉽게 지적해 낼 수 있고 재빨리 반응하게 만든다. 예를 들어 담낭 절제술을 한 환자가 잠을 자다 옆으로 돌아 눕다가 복부 봉합 부위의 긴장으로 인해 갑자기 소리를 지르게 된다. 환자는 절개부위를 보존하기 위해 손이 저절로 봉합 부위로 가게 된다.

Bioaccumulation and Bioavailability of Copper and Zinc on Mineral-Enriched Mycelium of Grifola frondosa

Débora Figlas,Micaela Oddera,Ne´stor Curvetto 한국식품영양과학회 2010 Journal of medicinal food Vol.13 No.2

Grifola frondosa is an edible and medicinal mushroom. The bioaccumulation and potential biovailability of Cu and Zn were studied to obtain mycelium with potential properties as a food dietary supplement. Mycelia grown in the presence of nonmycotoxic concentrations of 100 and 200ppm of Cu or 25 and 50ppm of Zn accumulated 200–322ppm and 267–510ppm of Cu or Zn, respectively. When these enriched metal mycelia were subjected in vitro to a simulated gastrointestinal digestion, the solubility in these digestive fluids was 642–669ppm and 102–530ppm, which represent 32–33% and 0.7–3.5% of the recommended daily intake (RDI) for Cu and Zn, respectively, in 1g of mycelium. These results are discussed in relation to the RDI values exhibited by two commercial supplements, and arguments are given on the potential use of these mineral-enriched mycelia in capsules (in the case of Cu-enriched mycelia), in food preparations, and also as a component of cosmetic mixtures.

Optimization of a telescope movable support structure by means of Volumetric Displacements

Néstor F. Ortega,Sandra I. Robles 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.4

The Purpose of this paper is to show the applicability of a methodology, developed by the authors, with which to perform the mechanical optimization of space truss structures strongly restricted. This methodology use a parameter call “Volumetric Displacement”, as the Objective Function of the optimization process. This parameter considers altogether the structure weight and deformation whose effects are opposed. The Finite Element Method is employed to calculate the stress/strain state and the natural frequency of the structure through a structural linear static and natural frequency analysis. In order to show the potentially of this simple methodology, its application on a large diameter telescope structure (10 m) considering the strongly restriction that became of its use, is presented. This methodology, applied in previous works on continuous structures, such as shell roof and fluid storage vessels, is applied in this case to a space truss structure, with the purpose of generalize its applicability to different structural topology. This technique could be useful in the morphology design of deployable and retractable roof structures, whose use has extensively spread in the last years.

Theoretical model to determine bond loss in prestressed concrete with reinforcement corrosion

Néstor F. Ortega,Juan M. Moro,Romina S. Meneses 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.1

This paper reviews the mechanical effects produced by reinforcement corrosion of prestressed concrete beams. Specifically, modifications in the bonding of the tendon to the concrete that reduce service life and load bearing capacity are studied. Experimental information gathered from previous works has been used for the theoretical analysis. Relationships between bond stress loss and reinforcement penetration in the concrete, and concrete external cracking were established. Also, it was analysed the influence that has the location of the area affected by corrosion on the loss magnitude of the initial prestress.