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Mit wenigen Ausnahmen wird im elektrischen Versorgungssystem die Pumpspeichertechnik zur Pufferung größerer Abweichungen zwischen momentanem Stromverbrauch und -erzeugung und zur zeitlichen Verschiebung von Lasten eingesetzt. Erste großtechnische Anlagen wurden bereits Ende der zwanziger Jahre des letzten Jahrhunderts in Deutschland gebaut, um die Auslastung thermischer Kraftwerke gleichmäßiger zu ermöglichen. Pumpspeicherwerke bieten sich somit als Referenztechnologie an, mit der sich neue Entwicklungen messen müssen. Ein Überblick.
Die Transformation der Energiesysteme im Rahmen der Energiewende macht diese durch zusätzliche Komponenten und Wechselwirkungen immer komplexer. Das ökonomische und ökologische Potenzial, dass sich aus der Nutzung der Synergien dieser Komponenten ergeben kann, erfordert eine gemeinsame Betrachtung des gesamten Energiesystems hinsichtlich sämtlicher Energie- und Verbrauchssektoren.
Die Energiesystemmodellierung stellt eine geeignete Methode zur Modellierung und Optimierung dieser urbanen Energiesysteme dar. Mit dem „Spreadsheet Energy System Model Generator“ (SESMG) hat die FH Münster ein Open Source Tool entwickelt, das die Betrachtung urbaner Quartiere ermöglicht. Diese können hinsichtlich verschiedener Zielkriterien wie z. B. monetären Kosten und THG-Emissionen optimiert werden. Die tabellenbasierte Eingabe erfordert keine Programmierkenntnisse. Das implementierte Urban District Upscaling Tool erleichtert die effektive Modellierung auch größerer Systeme. Die automatisierte Ergebnisaufbereitung ermöglicht eine schnelle Analyse der Ergebnisse.
Der Spreadsheet Energy System Model Generator (SESMG) ist ein Werkzeug zur Modellierung und Optimierung von (urbanen) Energiesystemen. Der SESMG hat eine browserbasierte grafische Benutzeroberfläche, eine tabellenbasierte Dateneingabe und eine ausführliche Dokumentation, was einen einfachen Einstieg ermöglicht. Zudem erfordern die Installation und Anwendung keine Programmierkenntnisse. Im SESMG sind verschiedene Modellierungsmethoden implementiert, wie z. B. die Anwendung des Multi-Energie-System-Ansatzes, die multikriteriale Optimierung, modellbasierte Methoden zur Reduktion des Rechenaufwands sowie die automatisierte Erstellung von räumlich hoch aufgelösten Energiesystemmodellen. Somit können urbane Energiesysteme mithilfe des SESMGs mit vergleichsweise geringem Aufwand, aber unter Berücksichtigung einer Vielzahl von Parametern und Randbedingungen, modelliert und optimiert werden.
(1) The use of renewable energy for power and heat supply is one of the strategies to reduce greenhouse gas emissions. As only 14% of German households are supplied with renewable energy, a shift is necessary. This shift should be realized with the lowest possible environmental impact. This paper assesses the environmental impacts of changes in energy generation and distribution, by integrating the life cycle assessment (LCA) method into energy system models (ESM). (2) The integrated LCA is applied to a case study of the German neighborhood of Herne, (i) to optimize the energy supply, considering different technologies, and (ii) to determine the environmental impacts of the base case (status quo), a cost-optimized scenario, and a CO2-optimized scenario. (3) The use of gas boilers in the base case is substituted with CHPs, surface water heat pumps and PV-systems in the CO2-optimized scenario, and five ground-coupled heat pumps and PV-systems for the cost-optimized scenario. This technology shift led to a reduction in greenhouse gas emissions of almost 40% in the cost-optimized, and more than 50% in the CO2-optimized, scenario. However, technology shifts, e.g., due to oversized battery storage, risk higher impacts in other categories, such as terrestrial eco toxicity, by around 22%. Thus, it can be recommended to use smaller battery storage systems. (4) By combining ESM and LCA, additional environmental impacts beyond GHG emissions can be quantified, and therefore trade-offs between environmental impacts can be identified. Furthermore, only applying ESM leads to an underestimation of greenhouse gas emissions of around 10%. However, combining ESM and LCA required significant effort and is not yet possible using an integrated software.
Unsteady ventilation is being discussed to improve indoor air quality and comfort by simultaneously reducing the energy consumption. But until now, neither any standard system has been established nor are there any design parameters and clear specifications in standards. One reason for this lack of standardisation might be the ver-satile approaches for creating unsteady room airflows: sinusoidal variations, intermittent flow rates, and simu-lated natural wind or temperature variations in forced convection and the use of chaotic structures in free convection. Thus, this article gives an overview of systems available in Germany/Europe, international research and unresolved issues. It allows a clear focus for future investigations to be developed so that unsteady venti-lation concepts will be successfully utilised in practice. Experiments showed positive effects on indoor air quality (IAQ), comfort and energy consumption. However, two main questions have not been answered, yet: what are the fluid mechanical reasons for the observed effects and what are the best parameters to create unsteady room airflows?
The effects of different unsteady ventilation strategies on flow-structures in a room are investigated and compared to steady ventilation with the same mean exchange rate. For this, whole-field optical flow measurements were executed by means of a particle image velocimetry system (PIV) in a Reynolds-scaled room model in water. In a first series of experiments, sinusoidal varied supply flows with different frequencies were analysed; two equally supplied simple nozzles in the ceiling were used as inlets. The setup was validated by comparing jet velocities with literature values.
Typically, room airflows are investigated with punctual measurement techniques (e.g.
anemometers), which have an impact on the flow field, or with smoke gas experiments. By using PIV, the flow can be analysed without any influence of sensors or stands/traverses and whole-field measurement data with high spatial resolution and detailed information on the flow field can be collected.
Local and time-averaged velocities and standard deviations were calculated for all scenarios. Unsteady conditions were created by a sinusoidal variation of the supply flow rate with frequencies between 0.025 1/s and 0.050 1/s, an offset of about 1.1 m3/h and an amplitude of about ±1.0 m3/h, which leads to a mean exchange rate of 3.5 1/h. Although averaged velocity fields only show slight differences between steady and unsteady conditions, single pictures vary widely. First effects of unsteady ventilation on flow structures can be recognized. Steady structures are destroyed, and velocities change rapidly.
The inlets will be changed to small-scale ceiling-diffusors in future experiments to create more realistic room ventilation conditions. Other types of unsteady supply flows will be implemented, and parameters will be varied. The results of the PIV-measurements can be used to validate CFD simulations and to derive dimensioning rules and application recommendations.