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Manderla M.,Voith Hydro Ocean Current Technologies | Kiniger K.,Voith Hydro Ocean Current Technologies | Koutnik J.,Voith Hydro Ocean Current Technologies
IOP Conference Series: Earth and Environmental Science | Year: 2014

Water hammer phenomena are important issues for high head hydro power plants. Especially, if several reversible pump-turbines are connected to the same waterways there may be strong interactions between the hydraulic machines. The prediction and coverage of all relevant load cases is challenging and difficult using classical simulation models. On the basis of a recent pump-storage project, dynamic measurements motivate an improved modeling approach making use of the Thoma number dependency of the actual turbine behaviour. The proposed approach is validated for several transient scenarios and turns out to increase correlation between measurement and simulation results significantly. By applying a fully automated simulation procedure broad operating ranges can be covered which provides a consistent insight into critical load case scenarios. This finally allows the optimization of the closing strategy and hence the overall power plant performance.

Saltara F.,University of Sao Paulo | Neto A.D.,Voith Hydro Ocean Current Technologies | Lopez J.I.H.,Mackenzie Presbyterian University
International Journal of Offshore and Polar Engineering | Year: 2011

The 3D flow around a circular cylinder free to oscillate transversely to the free stream was simulated using ComputationalFluid Dynamics (CFD) and the Spalart-Allmaras Detached Eddy Simulation (DES) turbulence model for a Reynolds numberReD10 4. Simulations were carried out for a small mass-damping parameter m *ζ=0000858, where m *=3.3 and ζ=000026.We found good agreement between the numerical results and experimental data. The simulations predicted the high observedamplitudes of the upper branch of vortex-induced vibrations for low mass-damping parameters. © by The International Society of Offshore and Polar Engineers.

Arnold M.,University of Stuttgart | Kretschmer M.,University of Stuttgart | Koch J.,University of Stuttgart | Cheng P.W.,University of Stuttgart | Biskup F.,Voith Hydro Ocean Current Technologies
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

Prior to using any simulation method for load simulations, it is required to verify and validate it. However, it is not only enough to find a discrepancy between the model and the reference data, but it is also required to identify the section within the code responsible for any bugs. Therefore the aim of this paper is to present a set of basic validation cases to be used in Fluid-Structure-Interaction (FSI) simulations. By splitting the FSI method up into its key functionalities of forces, torques, translations, rotations, etc., each part of the coupling can be validated by itself with a specific case. Each of the cases consists of a free decay pendulum in water. To gain experimental reference data, the cases are set up in a water basin and the motion over time is recorded by an optical measurement system. In a second step the validation cases are set up in a Fluid-Multibody FSI code and simulated. The motions from numerical simulation and experiment are compared and used to draw a conclusion on the integrity of the experimental data presented and the validity of the tested FSI code. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).

Starzmann R.,University of Siegen | Carolus T.H.,University of Siegen | Tease K.,Voith Hydro Wavegen Ltd | Arlitt R.,Voith Hydro Ocean Current Technologies
9th European Conference on Turbomachinery: Fluid Dynamics and Thermodynamics, ETC 2011 - Conference Proceedings | Year: 2011

In an oscillating water column (OWC) power plant the Wells turbine is operated along its complete characteristic curve from no load to overload and back. However, the 'design' point as a distinct point of operation may serve to assess the influence of primary design parameters on the turbine's overall performance more clearly. The design method employed here is based on an analytical free vortex and blade element theory. For a given load, hub solidity and hub-tip ratio the model yields a set of dimensionless performance coefficients at design point as well as the blade geometry. In a second step the performance of several turbine rotor designs are predicted by a 3D numerical RANS method. Selected rotors were manufactured and the measured and predicted performance compared. The results indicate how the turbine's performance characteristics are affected by the choice of hub-tip ratio and solidity. This will identify candidates for optimal turbine designs for a given OWC system.

Mendes V.F.,Federal University of Itajubá | Mendes V.F.,Federal University of Minas Gerais | De Sousa C.V.,Federal University of Itajubá | De Sousa C.V.,Federal University of Minas Gerais | And 3 more authors.
IEEE Transactions on Energy Conversion | Year: 2011

Modern grid codes determine that wind generation plants must not be disconnected from the grid during some levels of voltage sags and contribute to network stabilization. Wind energy conversion systems equipped with the doubly fed induction generator (DFIG) are one of the most frequently used topologies, but they are sensitive to grid disturbances due to the stator direct connection to the grid. Therefore, many efforts have been done in the last few years in order to improve their low-voltage ride-through capability. This paper analyzes the behavior of the DFIG during symmetrical voltage sags using models in the frequency domain. A new strategy, the machine magnetizing current control, is proposed in order to enhance the system response during balanced dips. The method is derived on a theoretical basis and numerically investigated by means of simulation. Experimental results are presented and validate the proposed strategy. Finally, the practical aspects of the use of this strategy are discussed. © 2011 IEEE.

Ruopp A.,University of Stuttgart | Daus P.,Voith Hydro Ocean Current Technologies | Biskup F.,Voith Hydro Ocean Current Technologies | Riedelbauch S.,University of Stuttgart
Journal of Renewable and Sustainable Energy | Year: 2015

The magnitude of energy, which can be extracted by tidal energy converter devices, has a significant impact on the commercial viability of a project. Therefore, a quantitative characterization of the tidal current at the location of interest and subsequently a reliable prediction of the productivity of a tidal energy converter prior to installation is of high interest. This paper presents the successful deployment of a unique and novel fully symmetric tidal in-stream current energy converter HyTide 110-5.3 in Jindo, South Korea, and a methodology to predict the productivity of a single device based on simulation. The simulation combines a 2D shallow water equation model with turbine performance curves and is validated using real performance data from the prototype under real conditions. In addition, the predicted productivity is compared with actual field measurements during the operation of the Voith demonstrator using two Acoustic Doppler Current Profilers according to the IEC specifications for the performance assessment of Tidal Energy Converters, which is novel at that time. The simulation results show that the productivity of a single device can be predicted accurately and furthermore serves as a proof of concept for the symmetrical turbine layout. The 2D shallow water equation solver based on OpenFOAM® (tidalFoam) captures the rough conditions at the turbine site accurately, where the turbine is facing flood tides with a mean inclined inflow angle of 30°. In addition, the zero-equation turbulence model is shown to successfully capture the influence of a Kármán Vortex street on the turbine unit. High-resolution data of bathymetry, shorelines, and tidal elevations are used to set up the open boundaries of the unstructured mesh used in the model. The sea ground friction as an additional source term in the model is used to calibrate the simulation against Acoustic Doppler Current Profiler measurements on site. The simulation results are shown to be reliable, yielding highly accurate productivity predictions of a single tidal turbine. This is an important step towards a robust commercial evaluation of tidal energy projects prior to installation. Based on the single turbine model, simulations of three tidal current turbine farms as well as the available theoretical and technical power output of the region around Jindo during an entire moon cycle were performed. Possible impacts on average volumetric flow rate changes for neighbouring channels are presented. © 2015 AIP Publishing LLC.

Mota D.D.S.,Voith Hydro Ocean Current Technologies | Goldemberg C.,University of Sao Paulo
IEEE Latin America Transactions | Year: 2010

This paper compares the behaviour of two different control structures of automatic voltage regulators of synchronous machines equipped with static excitation systems. These systems have a fully controlled thyristor bridge that supplies DC current to the rotor winding. The rectifier bridge is fed by the stator terminals through a step-down transformer. The first control structure, named "Direct Control", has a single proportional-integral (PI) regulator that compares stator voltage setpoint with measured voltage and acts directly on the thyristor bridges firing angle. This control structure is usually employed in commercial excitation systems for hydrogenerators. The second structure, named "Cascade Control", was inspired on control loops of commercial DC motor drives. Such drives employ two PIs in a cascade arrangement, the external PI deals with the motor speed while the internal one regulates the armature current. In the adaptation proposed, the external PI compares setpoint with the actual stator voltage and produces the setpoint to the internal PI-loop which controls the field current. © 2005 IEEE.

Main directions and velocity distributions over time are essential for evaluation of economic efficiency of tidal current turbines. In addition, numerical analyses help finding suitable spots and can identify and locate eddies or unfavorable flow patterns. This can support the preselection of measurement campaigns. For this, an in-house code is utilized. A description about the preprocessing methods, the simulation and the data assessment of a high resolution ocean modeling case is given.

News Article | June 20, 2015
Site: www.marine-renewables-news.com

Innogy Venture Capital, the corporate venture capital unit of Germany-based renewables developer RWE Innogy, has sold its 20% stake in Germany-based tidal turbine manufacturer Voith Hydro Ocean Current Technologies to majority shareholder Voith Hydro, it said on Friday. Innogy VC has held a 20% stake in Voith Hydro Ocean Current Technologies since 2009, with the other 80% held by Voith Hydro, a hydropower equipment subsidiary of German mechanical engineering firm Voith GmbH. The precise details of the transaction were not revealed but Innogy VC said it was based on a medium two-digit valuation for the unit. “The Voith turbine technology with its concept based on robustness and longevity is optimally positioned for the future market of ocean current turbines. We are very pleased that Innogy Venture Capital could help in the past few years to realise this technology”, said Innogy Venture Capital Managing Director Crispin Leick. Leick told Clean Energy Pipeline in June that Innogy VC was in the process of exiting investments involving strenuous technology challenges. Voith Hydro Ocean Current Technologies’ turbines have been successfully tested in pilot schemes in the UK, Canada and South Korea but have not yet become commercially successful.

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