Andreas Witzig | Swiss Federal Institute of Technology (ETH) (original) (raw)
Papers by Andreas Witzig
Physics and Simulation of Optoelectronic Devices IX, 2001
In this work the optical cavity of a vertical-cavity surface-emitting laser (VCSEL) is analyzed w... more In this work the optical cavity of a vertical-cavity surface-emitting laser (VCSEL) is analyzed with the goal of performing a coupled electro-optical simulation of the device. For this simulation, the eigenmodes and the eigenvalues of the optical cavity have to be obtained. A common approach is to treat Maxwell's equations in the frequency domain and to solve the resulting algebraic eigenvalue equation. As an alternative, the electromagnetic problem is solved in time-domain. The response of the optical cavity is calculated by the finite-difference time-domain (FDTD) method. The optical wave propagation is modeled rigorously, including evanescent and propagating waves. From the FDTD simulation, a steady state optical intensity pattern is extracted. The eigenvalues of the dominant modes are determined using a Pade type approximation.
Proceedings of the EuroSun 2010 Conference, 2010
... Andreas Witzig1, Urs Stöckli1, Patrick Kistler1, Raffaele Bornatico2 and Michael Pfeiffer1, 2... more ... Andreas Witzig1, Urs Stöckli1, Patrick Kistler1, Raffaele Bornatico2 and Michael Pfeiffer1, 2 1 Vela Solaris AG, Stadthausstrasse 125, CH-8400 Winterthur, Switzerland 2 Institute for Dynamic Systems and Control, Swiss Federal Institute of Technology (ETH ... [17] J. Remund, et. al. ...
Seamless Learning
ZusammenfassungDas Projekt MoSeL des IBH-Labs Seamless Learning befasst sich mit dem Modellieren,... more ZusammenfassungDas Projekt MoSeL des IBH-Labs Seamless Learning befasst sich mit dem Modellieren, dem Visualisieren und der Simulation dynamischer Systeme als Seamless Learning. Die Ergebnisse der Arbeiten bieten Lösungsansätze für durchgängige Bildungs- und Arbeitsprozesse, welche zur Nutzung der Simulation dynamischer Systeme für eine (nachhaltige) Entscheidungsfindung befähigen. Hierzu gehört ein durchgängiger Kompetenzaufbau vom Modellieren zur Simulation dynamischer Systeme ebenso wie die Befähigung zur Kommunikation zwischen verschiedenen Berufs-und Arbeitsgruppen. Die Umsetzung der Lösungsansätze in der Praxis wird am Beispiel eines Mathematikmoduls in der Hochschullehre vorgestellt.
Seamless Learning
ZusammenfassungWellenphänomene werden in den Lehrplänen meist erst nach gründlicher Vorbereitung ... more ZusammenfassungWellenphänomene werden in den Lehrplänen meist erst nach gründlicher Vorbereitung der formalen Grundlagen eingeführt. Die Studierenden verfügen dann über ein mathematisches Rüstzeug, dass ihnen den Zugang über analytische Formeln erlaubt. Als Alternative zu diesem mathematiklastigen Weg möchten wir in diesem Projekt das Experimentieren mit Computersimulationen ins Zentrum stellen.
Numerous simulation tools are currently in use to investigate the solar systems on the one side, ... more Numerous simulation tools are currently in use to investigate the solar systems on the one side, and separate tools exist to design heat pump systems. It is in particular in the solar field that dynamic simulation with the use of statistical meteorological data has been established and proven to be capable for speeding up design and optimization of heating systems and for predicting the economic viability of the systems.
The International Energy Agency (IEA) is an autonomous body within the framework of the Organizat... more The International Energy Agency (IEA) is an autonomous body within the framework of the Organization for Economic Co-operation and Development (OECD) based in Paris. Established in 1974 after the first “oil shock, ” the IEA is committed to carrying out a comprehensive program of energy cooperation among its members and the Commission of the European Communities. The IEA provides a legal framework, through IEA Implementing Agreements such as the Solar Heating and Cooling Agreement, for international collaboration in energy technology research and development (R&D) and deployment. This IEA experience has proved that such collaboration contributes significantly to faster technological progress, while reducing costs; to eliminating technological risks and duplication of efforts; and to creating numerous other benefits, such as swifter expansion of the knowledge base and easier harmonization of standards. The Solar Heating and Cooling Programme was one of the first IEA Implementing Agree...
The computation of optical modes inside axisymmetric cavity resonators with a general spatial per... more The computation of optical modes inside axisymmetric cavity resonators with a general spatial permittivity profile is a formidable computational task. In order to avoid spurious modes the vector Helmholtz equations are discretised by a mixed finite element approach. We formulate the method for first and second order Nédélec edge and Lagrange nodal elements. We discuss how to accurately compute the element matrices and to solve the resulting large sparse complex symmetric eigenvalue problems. We validate our approach by three numerical examples that contain varying material parameters and absorbing boundary conditions (ABC).
This work reviews the physics-based dynamic simulation of solar cooling systems for planning and ... more This work reviews the physics-based dynamic simulation of solar cooling systems for planning and optimizing solar cooling systems. Heat assisted cooling, free cooling as well as cooling machines driven by photovoltaic electricity are covered. The study presents a comparison between the different techniques as well as a practical guide for using simulation for solar cooling applications. Simulation models are implemented into the commercial software tool Polysun which allows fast evaluation and usage of state-of-the-art graphical user interface and result representation. Adsorption and Absorption chillers have been introduced already some years ago [1] and validated against TRNSYS simulations and measurement [2] as well as used extensively in various application areas and different regions of the world [3,4]. With the rapid price decline of solar photovoltaic modules, solar cooling systems with traditional cooling devices in combination with photovoltaic installations have become an ...
Die Steuerung gebäudetechnischer Energiesysteme ist für die Maximierung des Solarertrags sowie fü... more Die Steuerung gebäudetechnischer Energiesysteme ist für die Maximierung des Solarertrags sowie für die Optimierung der Anlageneffizienz von grösster Bedeutung. In realen Projekten zeigt sich, dass die Programmierung der Steuerung in der Planung und Projektierung oft nicht mit der effektiv in der Realisierungsphase umgesetzten Steuerung übereinstimmt (siehe normierte Standardplanungsphasen in Figur 1). Das vorausgesagte gute Systemverhalten wird damit oft nicht erreicht.
Durch konsequenten Einsatz einer korrekten, thermohydraulischen Dimensionierung können die Anlage... more Durch konsequenten Einsatz einer korrekten, thermohydraulischen Dimensionierung können die Anlagenkosten minimiert sowie Betriebsstörungen und deren Fehlerkosten vermieden werden. Damit werden nicht nur die Voraussetzungen für die Wettbewerbsfähigkeit der Solarthermie und die Langlebigkeit der Anlagen erfüllt, sondern auch das Vertrauen der Planer, Installateure, Bauherrschaften und Investoren in diese Technologie gestärkt.
Renewable Energy and Sustainable Buildings
Globalization is not only affecting trade and commerce, but also education. An increasing number ... more Globalization is not only affecting trade and commerce, but also education. An increasing number of universities around the world offer Master courses for international students. Due to very different technical, cultural, and social backgrounds many challenges are encountered by students and teachers alike. Advanced didactics and innovative teaching tools are required to master these problems. In the field of renewable energies, dynamic simulation software can offer interesting solutions.
Proceedings of EuroSun2016, 2016
Experience in using simulation software for teaching solar energy and heat pump applications are ... more Experience in using simulation software for teaching solar energy and heat pump applications are presented and discussed in this publication. The authors present suitable didactic concepts specifically developed for teaching renewable energy and energy efficiency topics. Two main advantages of applying simulation software in solar education are identified: 1. simulation can provide an understanding of data that is otherwise not accessible (e.g. cumulated operating hours and number of starts of a heat pump depending on control strategy); 2. use of simulation software in teaching have a positive influence on the motivation and attitude of the students. These benefits typically come with costs of some additional effort in lecture preparation. Finally, different international teaching programs are discussed, in which simulation software currently plays a major role. It is analyzed how education programs might have to be adjusted for different cultures and industries.
Physics and Simulation of Optoelectronic Devices IX, 2001
In this work the optical cavity of a vertical-cavity surface-emitting laser (VCSEL) is analyzed w... more In this work the optical cavity of a vertical-cavity surface-emitting laser (VCSEL) is analyzed with the goal of performing a coupled electro-optical simulation of the device. For this simulation, the eigenmodes and the eigenvalues of the optical cavity have to be obtained. A common approach is to treat Maxwell's equations in the frequency domain and to solve the resulting algebraic eigenvalue equation. As an alternative, the electromagnetic problem is solved in time-domain. The response of the optical cavity is calculated by the finite-difference time-domain (FDTD) method. The optical wave propagation is modeled rigorously, including evanescent and propagating waves. From the FDTD simulation, a steady state optical intensity pattern is extracted. The eigenvalues of the dominant modes are determined using a Pade type approximation.
Proceedings of the EuroSun 2010 Conference, 2010
... Andreas Witzig1, Urs Stöckli1, Patrick Kistler1, Raffaele Bornatico2 and Michael Pfeiffer1, 2... more ... Andreas Witzig1, Urs Stöckli1, Patrick Kistler1, Raffaele Bornatico2 and Michael Pfeiffer1, 2 1 Vela Solaris AG, Stadthausstrasse 125, CH-8400 Winterthur, Switzerland 2 Institute for Dynamic Systems and Control, Swiss Federal Institute of Technology (ETH ... [17] J. Remund, et. al. ...
Seamless Learning
ZusammenfassungDas Projekt MoSeL des IBH-Labs Seamless Learning befasst sich mit dem Modellieren,... more ZusammenfassungDas Projekt MoSeL des IBH-Labs Seamless Learning befasst sich mit dem Modellieren, dem Visualisieren und der Simulation dynamischer Systeme als Seamless Learning. Die Ergebnisse der Arbeiten bieten Lösungsansätze für durchgängige Bildungs- und Arbeitsprozesse, welche zur Nutzung der Simulation dynamischer Systeme für eine (nachhaltige) Entscheidungsfindung befähigen. Hierzu gehört ein durchgängiger Kompetenzaufbau vom Modellieren zur Simulation dynamischer Systeme ebenso wie die Befähigung zur Kommunikation zwischen verschiedenen Berufs-und Arbeitsgruppen. Die Umsetzung der Lösungsansätze in der Praxis wird am Beispiel eines Mathematikmoduls in der Hochschullehre vorgestellt.
Seamless Learning
ZusammenfassungWellenphänomene werden in den Lehrplänen meist erst nach gründlicher Vorbereitung ... more ZusammenfassungWellenphänomene werden in den Lehrplänen meist erst nach gründlicher Vorbereitung der formalen Grundlagen eingeführt. Die Studierenden verfügen dann über ein mathematisches Rüstzeug, dass ihnen den Zugang über analytische Formeln erlaubt. Als Alternative zu diesem mathematiklastigen Weg möchten wir in diesem Projekt das Experimentieren mit Computersimulationen ins Zentrum stellen.
Numerous simulation tools are currently in use to investigate the solar systems on the one side, ... more Numerous simulation tools are currently in use to investigate the solar systems on the one side, and separate tools exist to design heat pump systems. It is in particular in the solar field that dynamic simulation with the use of statistical meteorological data has been established and proven to be capable for speeding up design and optimization of heating systems and for predicting the economic viability of the systems.
The International Energy Agency (IEA) is an autonomous body within the framework of the Organizat... more The International Energy Agency (IEA) is an autonomous body within the framework of the Organization for Economic Co-operation and Development (OECD) based in Paris. Established in 1974 after the first “oil shock, ” the IEA is committed to carrying out a comprehensive program of energy cooperation among its members and the Commission of the European Communities. The IEA provides a legal framework, through IEA Implementing Agreements such as the Solar Heating and Cooling Agreement, for international collaboration in energy technology research and development (R&D) and deployment. This IEA experience has proved that such collaboration contributes significantly to faster technological progress, while reducing costs; to eliminating technological risks and duplication of efforts; and to creating numerous other benefits, such as swifter expansion of the knowledge base and easier harmonization of standards. The Solar Heating and Cooling Programme was one of the first IEA Implementing Agree...
The computation of optical modes inside axisymmetric cavity resonators with a general spatial per... more The computation of optical modes inside axisymmetric cavity resonators with a general spatial permittivity profile is a formidable computational task. In order to avoid spurious modes the vector Helmholtz equations are discretised by a mixed finite element approach. We formulate the method for first and second order Nédélec edge and Lagrange nodal elements. We discuss how to accurately compute the element matrices and to solve the resulting large sparse complex symmetric eigenvalue problems. We validate our approach by three numerical examples that contain varying material parameters and absorbing boundary conditions (ABC).
This work reviews the physics-based dynamic simulation of solar cooling systems for planning and ... more This work reviews the physics-based dynamic simulation of solar cooling systems for planning and optimizing solar cooling systems. Heat assisted cooling, free cooling as well as cooling machines driven by photovoltaic electricity are covered. The study presents a comparison between the different techniques as well as a practical guide for using simulation for solar cooling applications. Simulation models are implemented into the commercial software tool Polysun which allows fast evaluation and usage of state-of-the-art graphical user interface and result representation. Adsorption and Absorption chillers have been introduced already some years ago [1] and validated against TRNSYS simulations and measurement [2] as well as used extensively in various application areas and different regions of the world [3,4]. With the rapid price decline of solar photovoltaic modules, solar cooling systems with traditional cooling devices in combination with photovoltaic installations have become an ...
Die Steuerung gebäudetechnischer Energiesysteme ist für die Maximierung des Solarertrags sowie fü... more Die Steuerung gebäudetechnischer Energiesysteme ist für die Maximierung des Solarertrags sowie für die Optimierung der Anlageneffizienz von grösster Bedeutung. In realen Projekten zeigt sich, dass die Programmierung der Steuerung in der Planung und Projektierung oft nicht mit der effektiv in der Realisierungsphase umgesetzten Steuerung übereinstimmt (siehe normierte Standardplanungsphasen in Figur 1). Das vorausgesagte gute Systemverhalten wird damit oft nicht erreicht.
Durch konsequenten Einsatz einer korrekten, thermohydraulischen Dimensionierung können die Anlage... more Durch konsequenten Einsatz einer korrekten, thermohydraulischen Dimensionierung können die Anlagenkosten minimiert sowie Betriebsstörungen und deren Fehlerkosten vermieden werden. Damit werden nicht nur die Voraussetzungen für die Wettbewerbsfähigkeit der Solarthermie und die Langlebigkeit der Anlagen erfüllt, sondern auch das Vertrauen der Planer, Installateure, Bauherrschaften und Investoren in diese Technologie gestärkt.
Renewable Energy and Sustainable Buildings
Globalization is not only affecting trade and commerce, but also education. An increasing number ... more Globalization is not only affecting trade and commerce, but also education. An increasing number of universities around the world offer Master courses for international students. Due to very different technical, cultural, and social backgrounds many challenges are encountered by students and teachers alike. Advanced didactics and innovative teaching tools are required to master these problems. In the field of renewable energies, dynamic simulation software can offer interesting solutions.
Proceedings of EuroSun2016, 2016
Experience in using simulation software for teaching solar energy and heat pump applications are ... more Experience in using simulation software for teaching solar energy and heat pump applications are presented and discussed in this publication. The authors present suitable didactic concepts specifically developed for teaching renewable energy and energy efficiency topics. Two main advantages of applying simulation software in solar education are identified: 1. simulation can provide an understanding of data that is otherwise not accessible (e.g. cumulated operating hours and number of starts of a heat pump depending on control strategy); 2. use of simulation software in teaching have a positive influence on the motivation and attitude of the students. These benefits typically come with costs of some additional effort in lecture preparation. Finally, different international teaching programs are discussed, in which simulation software currently plays a major role. It is analyzed how education programs might have to be adjusted for different cultures and industries.