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Retrofit of a combined heat and power plant with gas and steam turbines to hydrogen with special consideration of the balance of plant

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International Journal of Hydrogen Energy 2025年

作者： Schiffer, Barbara Pfennig, Malte Clees, Tanja Grantham-Allee 20 Sankt Augustin53757 Germany Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven Sankt Augustin53757 Germany

In 2020, around 44% of natural gas in Germany was used in combined heat and power as well as in combined cycle gas turbines plants. As district heating will play an important role in future heating planning, the retrofit of these plants to hydrogen is a viable option. This paper analyzes a typical combined cycle power plant, including its balance of plant under consideration of different hydrogen blends. We show that retrofits are limited by the gas turbines in many cases. For instance, the preheater in the fuel gas system must be dimensioned higher than with natural gas. While pressure losses are very low, materials could be a problem due to higher volume flows. Additionally, the higher combustion temperatures in the gas turbine can compensate for possible efficiency losses in the Heat Recovery System Generator (HRSG) and steam turbine making this a suitable approach for electricity-led plants. However, for heat-led plants this leads to a reduction in the district heating output. Therefore, the performance of the HRSG must be considered as a limiting factor for heat-driven plants and the change in flue gas must be analyzed. Currently, hydrogen blends of 20–40 vol.-% appear feasible without major adjustments. The water content in the exhaust gas can also lead to problems in the HRSG and flue gas aftertreatment due to changes in the dew point. For higher hydrogen blends, a plant specific analysis is recommended. © 2025 The Authors

关键词： Steam turbines

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Application of a Regional Data Set of the Housing Sector for Hydrogen Storage-Supported Energy System Planning

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Energy Engineering 2025年第5期122卷 1755-1770页

作者： Steffen Schedler Michael Bareev-Rudy Stefanie Meilinger Tanja Clees Department of Engineering and Communication(IWK) Institute for TechnologyResource and Energy-efficient Engineering(TREE)Hochschule Bonn-Rhein-SiegUniversity of Applied ScienceSankt Augustin53757Germany International Centre for Sustainable Development(IZNE) Hochschule Bonn-Rhein-SiegUniversity of Applied ScienceSankt Augustin53757Germany Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss BirlinghovenSankt Augustin53754Germany

Germany aims to achieve a national climate-neutral energy system by *** residential sector still accounts for 29%of end energy consumption,with 74%attributed to the direct use of fossil fuels for heating and hot *** order to reduce fossil energy use in the household sector,great efforts are being made to design new energy concepts that expand the use of renewable energies to supply electricity *** is toconvertparts of the natural gas grid to a hydrogen-based gas grid to deliver and store energy for urban quarters of buildings,especially with older building stock where electrification of heat via heat pumps is difficult due to technical,acoustical,and economic reasons.A comprehensive dataset was generated by a bottom-up analysis with open governmental and statistical data to determine regional building types regarding energy demand,solar potential,and existing grid *** buildings’connections to the electricity,gas,and district heating networks are *** this,a representative sample dataset was chosen as input for a newly developed energy system model based on energy flow *** model simulates the interaction of hydrogen generation(HG)(from excess solar energy by electrolysis),storage in a metal-hydride storage(MHS)tank,and hydrogen use in a connected fuel cell(FC),forming a local PVPtGtHP(Photovoltaic Power-to-Gas-to-Heat-and-Power)*** to the seasonal hydrogen storage path(HSP),a battery will complete the system to forma hybrid energy storage system(HESS).Paired with seasonal time series for PV power,electricity and heat demand,and a model for connection to grid infrastructure,the simulation of different hydrogen applications and MHS placements aims to analyze operating times and energy share of the systems’equipment and existing *** method to obtain the data set together with the simulationmodel presented can be used by energy planners for cities,communities,and building developers

关键词： Hydrogen storage hybrid energy storage system simulation housing sector energy share

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Sizing optimization of hybrid hydrogen energy storage systems: A metamodel-based approach

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International Journal of Hydrogen Energy 2025年

作者： Bareev-Rudy, Michael Schedler, Steffen Clees, Tanja Grantham-Allee 20 Sankt Augustin53757 Germany Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven Sankt Augustin53757 Germany

Hybrid energy storage systems (HESS), consisting of a battery, hydrogen storage, electrolyzer and fuel cell, have received increasing attention from the scientific community in recent years as they can help increase the use of renewable energy. In this paper, a novel metamodel-based sizing optimization workflow is developed. The workflow is demonstrated on residential building scenarios with real solar power data. Sobol sequences are utilized to vary the component size in simulation, while radial basis functions are employed to approximate simulation results, which are then used for the optimization. The utilization of waste heat from Power-to-Gas and Gas-to-Power processes is evaluated using thermal equations by extending an existing coupled electrochemical and thermodynamic HESS model built in the multiphysical energy system simulator MEgy. The results show a functional workflow that optimizes sizing for a given scenario and outputs the component's daily energy balance and state of charge. © 2025 The Authors

关键词： Waste heat utilization

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PERTURBATIONS OF EMBEDDED EIGENVALUES OF ASYMPTOTICALLY PERIODIC MAGNETIC SCHRÖDINGER OPERATORS ON A CYLINDER

arXiv

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arXiv 2025年

作者： Jansen, Jonas Sasane, Sara Maad Treschow, Wilhelm Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven Sankt Augustin53757 Germany Centre for Mathematical Sciences Lund University P.O. Box 118 Lund221 00 Sweden

We investigate the persistence of embedded eigenvalues for a class of magnetic Laplacians on an infinite cylindrical domain. The magnetic potential is assumed to be C2 and asymptotically periodic along the unbounded direction, with an algebraic decay rate towards a periodic background potential. Under the condition that the embedded eigenvalue of the unperturbed operator lies away from the thresholds of the continuous spectrum, we show that the set of nearby potentials for which the embedded eigenvalue persists forms a smooth manifold of finite and even codimension. The proof employs tools from Floquet theory, exponential dichotomies, and Lyapunov–Schmidt reduction. Additionally, we give an example of a potential which satisfies the assumptions of our main *** Codes 35P05, 47A55, 81Q15, 35B20, 35J10, 35J15, 81Q10 Copyright © 2025, The Authors. All rights reserved.

关键词： Eigenvalues and eigenfunctions

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Preconditioning for Efficiently Applying Algebraic Multigrid in Fully Implicit Reservoir Simulations

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SPE JOURNAL 2014年第4期19卷 726-736页

作者： Gries, Sebastian Stueben, Klaus Brown, Geoffrey L. Chen, Dingjun Collins, David A. Fraunhofer Institute for Algorithms and Scientific Computing Computer Modelling Group Limited

Fully implicit black-oil simulations result in huge, often very-ill-conditioned, linear systems of equations for different unknowns (e.g., pressure and saturations). It is well-known that the underlying Jacobian matrices contain both hyperbolic and nearly elliptic subsystems (corresponding to saturations and pressure, respectively). Because a reservoir simulation is typically driven by the behavior of the pressure, constrained-pressure-residual (CPR)-type two-stage preconditioning methods to solve the coupled linear systems are a natural choice and still belong to the most popular approaches. After a suitable extraction and decoupling, the computationally most costly step in such two-stage methods consists in solving the elliptic subsystems accurately enough. Algebraic multigrid (AMG) provides a technique to solve elliptic linear equations very efficiently. Hence, in recent years, corresponding CPR-AMG approaches have been extensively used in practice. Unfortunately, if applied in a straightforward manner, CPR-AMG does not always work as expected. In this paper, we discuss the reasons for the lack of robustness observed in practice, and present remedies. More precisely, we will propose a preconditioning strategy (based on a suitable combination of left and right preconditioning of the Jacobian matrix) that aims at a compromise between the solvability of the pressure subproblem by AMG and the needs of the outer CPR process. The robustness of this new preconditioning strategy will be demonstrated for several industrial test cases, some of which are very ill-conditioned. Furthermore, we will demonstrate that CPR-AMG can be interpreted in a natural way as a special AMG process applied directly to the coupled Jacobian systems.

关键词： preconditioning decoupling dynamic rowsumming Constrained Pressure residual Algebraic Multigrid

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A landscape analysis of standardisation in the field of artificial intelligence

Journal of ICT Standardization

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Journal of ICT Standardization 2020年第2期8卷 151-184页

作者： Ziegler, Wolfgang Fraunhofer Institute for Algorithms and Scientific Computing SCAI Sankt Augustin Germany

While projects, developments and applications addressing and using artificial intelligence (AI) are rather multifaceted and their number is constantly increasing, the standardisation activities in the field of artificial intelligence are limited, their number is significantly lower and does not increase at the same pace. The European funded project *** aims at supporting European experts' presence in and contributions to international standardisation activities in ICT. The focus of the project is on the 5 priority domains identified by the European Commission (Cloud computing, IoT, Big Data, Cyber Security, 5G) and on Artificial Intelligence while being open for other relevant topics defined in the annual European Rolling Plan for ICT Standardisation. The project has two main outcomes: (i) increased contribution of European experts in international standardisation through support by providing grants for planned contributions of successful applications of experts, and (ii) an online observatory of published standards and ongoing standardisation activities in the areas mentioned before. This observatory (called Standards Watch) is accessible through the project's web site and open for contributions and comments from registered users. As part of the effort for the Standards Watch the projects has prepared a comprehensive analysis of the international standardisation landscape in the AI field, that comprises a description of the ICT standards and ongoing work at international level in the field of AI across the standardisation organisations already active in the field. In this article we will present results of our work where we have analysed the work of the 5 international and European Standards Development Organisations (SDOs) IEEE,1 ISO/IEC,2 ITU-T,3 ETSI4 and CEN-CENELEC5 developing standards in the field of AI. The first 4 bodies have already been active several years in AI standardisation at the time of writing this article. CEN-CENELEC has launched a focu

关键词： Watches

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algorithms in the Orchard: An Embedding-Based Expert Answering System for Apple Rust

SSRN

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SSRN 2025年

作者： Anand, Astha Shen, Jian Cremers, Armin Bernd Jacobs, Marc Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven 1 North Rhine-Westphalia Sankt Augustin53757 Germany RPU Rhenish Plant Power Envirotech Co. Ltd. Bonn-Aachen International Center for Information Technology Friedrich-Hirzebruch-Allee 5 North Rhine-Westphalia Bonn53115 Germany

As sustainable agricultural practices gain importance, the need for intelligent pest control decision-making has grown. This paper introduces SEEDS: Similarity-based Expert Embedding Decision System, a Retrieval-Augmented Generation (RAG) based agricultural question-answering (QA) system. It is built upon a domain-specific knowledge graph (KG), representing Cedar Apple Rust disease, its host and causative agents, plant defense molecules against apple rust infection, and various pesticides. Utilizing the OpenAI embedding model, the system generates embeddings for user queries and KG data, employing similarity metrics to rank KG entries, facilitating accurate and relevant pest control recommendations. SEEDS is a promising niche AI tool in plant protection, setting the stage for scalable, extensible QA frameworks in precision agriculture. The results signify not only a step forward in agricultural expert systems but also highlight the potential for expanding this approach to other crops and pests, marking a substantial advancement in the use of AI for agricultural pest control. © 2025, The Authors. All rights reserved.

关键词： Fruits

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Sparse grids and applications : Munich 2012 /

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2014年

作者： SGA2012 (Conference)

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Loewy Decomposition of Linear Differential Equations 1

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丛书名： Texts & Monographs in Symbolic Computation

2012年

作者： Fritz Schwarz

ISBN: (数字)9783709112861

ISBN: (纸本)3709112850

The central subject of the book is the generalization of Loewy's decomposition - originally introduced by him for linear ordinary differential equations - to linear partial differential equations. Equations for a single function in two independent variables of order two or three are comprehensively discussed. A complete list of possible solution types is given. Various ad hoc results available in the literature are obtained algorithmically. The border of decidability for generating a Loewy decomposition are explicitly stated. The methods applied may be generalized in an obvious way to equations of higher order, in more variables or systems of such equations.

关键词： Symbolic and Algebraic Manipulation Differential Equations Mathematical and Computational Engineering Applications

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Adaptive parallel multigrid solution of 2D incompressible Navier-Stokes equations

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS 1997年第9期24卷 875-892页

作者： Wu, J Ritzdorf, H Oosterlee, K Steckel, B Schuller, A Institute of Algorithms and Scientific Computing GMD—German Research Centre for Information Technology Schloss Birlinghoven D-53754 Sankt Augustin Germany [*]Institute of Algorithms and Scientific Computing German Research Centre for Information Technology Schloss Birlinghoven D-53754 Sankt Augustin Germany

In this paper an adaptive parallel multigrid method and an application example for the 2D incompressible Navier-Stokes equations are described. The strategy of the adaptivity in the sense of local grid refinement in the multigrid context is the multilevel adaptive technique (MLAT) suggested by Brandt. The parallelization of this method on scalable parallel systems is based on the portable communication library CLIC and the message-passing standards: PARMACS, PVM and MPI. The specific problem considered in this work is a two-dimensional hole pressure problem in which a Poiseuille channel flow is disturbed by a cavity on one side of the channel. Near geometric singularities a very fine grid is needed for obtaining an accurate solution of the pressure value. Two important issues of the efficiency of adaptive parallel multigrid algorithms, namely the data redistribution strategy and the refinement criterion, are discussed here. For approximate dynamic load balancing, new data in the adaptive steps are redistributed into distributed memories in different processors of the parallel system by block remapping. Among several refinement criteria tested in this work, the most suitable one for the specific problem is that based on finite-element residuals from the point of view of self-adaptivity and computational efficiency, since it is a kind of error indicator and can stop refinement algorithms in a natural way for a given tolerance. Comparisons between different global grids without and with local refinement have shown the advantages of the self-adaptive technique, as this can save computer memory and speed up the computing time several times without impairing the numerical accuracy. (C) 1997 By John Wiley & Sons, Ltd.

关键词： adaptive parallel multigrid method local refinement criteria incompressible Navier-Stokes equations hole pressure problem

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