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Bad Essen, Germany

Roger S.,RWE Innogy GmbH | Dewals B.,University of Liege | Schuttrumpf H.,RWTH Aachen
WasserWirtschaft | Year: 2012

Experimental model data and numerical computations of dike-break induced flows complement one another within a hybrid approach. Characteristic flow field quantities are recorded with sophisticated measurement techniques during extensive model tests taking into account the specific boundary conditions of a dike break. The corresponding numerical computations are performed by two university codes, namely DGFlow and WOLF 2D, solving the two-dimensional depth-averaged shallow water equations as well as a commercial code STAR-CD based on the Reynolds-averaged Navier-Stokes-equations.

In the summer 2011 the German Government launched the so-called "Energiewende" which determines for the first time a long-term roadmap for the conversion of the German energy landscape until 2050. The shape of the German electricity market will change drastically due to an increasing focus on energy efficiency, ongoing support for renewable generation capacity and increasing electricity imports. Hydro power generation plays a minor role in these scenarios and is restricted mainly to additional capacity of pump storage power plants in Germany and adjacent countries. The role of these pump storages is to provide balancing energy to manage the increasing volatile generation from wind and solar power.

Operating wells are often influenced by performance losses which increase over time. These losses can be caused by clogging of system elements due to oxidation and precipitation of diluted Fe(II)- and Mn(II)-ions to Fe(III)- and Mn(IV)-hydroxides. The influence of iron clogging on the conductivity of the gravel pack-in particular on the hydraulic gradient in the gravel pack-is analyzed with a combined hydraulic and hydrogeochemical model of a vertical well in which the clogging process is accelerated by hydrochemical modifications. Over 295 h, the iron concentration in the filter gravel increased up to 15 g Fe per kg gravel. According to the preliminary findings, these incrustations induce an increase of the pressure loss in the filter gravel pack of nearly 30 %. After defining a test termination criterion, the model will be used for tests concerning different well material (screen and gravel pack) and methods for reduction of the incrustation (operation and regeneration) as well as for parametric studies. © 2012 Springer-Verlag.

Feltes C.,University of Duisburg - Essen | Van De Sandt R.,University of Duisburg - Essen | Koch F.,RWE Innogy GmbH | Shewarega F.,University of Duisburg - Essen | Erlich I.,University of Duisburg - Essen
2011 IEEE/PES Power Systems Conference and Exposition, PSCE 2011 | Year: 2011

The choice of the optimum neutral grounding option for a given network always involves a trade-off between the level of permissible short-circuit current on the one hand and tolerable voltage stress at the healthy phases following a single line to ground fault on the other. Effective grounding leads to high fault currents but the concomitant voltage stress is limited. The high fault current makes the fault detection and clearance easy. For conventional power transmission and distribution networks the available options are clear, and utilities have established grounding practices. But with increasing wind energy, it is necessary to take unique features of wind farms into consideration in choosing the most suitable neutral grounding option, at least for the wind farm grids. Based on EMT type simulation using a representative 144-MW wind farm grid, the paper provides an in-depth discussion of the pros and cons of the alternative grounding strategies vis-à-vis the relevant operational requirements within a large offshore wind farm, mainly focusing on the aspects of selectivity and voltage limitation. The level of over-voltages after tripping of the affected line for the feasible grounding options will be compared and contrasted with one another. Additionally, the effects of different voltage control strategies in the wind turbines on the over-voltages will be discussed and illustrated. © 2011 IEEE.

Beer S.,RWE Innogy GmbH | Gomez T.,Comillas Pontifical University | Gomez T.,Lawrence Berkeley National Laboratory | Dallinger D.,Fraunhofer Institute for Systems and Innovation Research | And 5 more authors.
IEEE Transactions on Smart Grid | Year: 2012

Current policies in the U.S. and other countries are trying to stimulate electric transportation deployment. Consequently, plug-in electric vehicle (PEV) adoption will presumably spread among vehicle users. With the increased diffusion of PEVs, lithium-ion batteries will also enter the market on a broad scale. However, their costs are still high and ways are needed to optimally deploy vehicle batteries in order to account for the higher initial outlay. This study analyzed the possibility of extending the lifecycle of PEV batteries to a secondary, stationary application. Battery usage can be optimized by installing used battery packs in buildings' microgrids. Employed as decentralized storage, batteries can be used for a microgrid's power supply and provide ancillary services (A/S). This scenario has been modeled with the Distributed Energy Resources Customer Adoption Model (DER-CAM), which identifies optimal equipment combinations to meet microgrid requirements at minimum cost, carbon footprint, or other criteria. Results show that used PEV batteries can create significant monetary value if subsequently used for stationary applications. © 2011 IEEE.

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