Energie · Gebäude · Umwelt (EGU)
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The energy demand of the residential sector contributed to about 29 % of Germany’s final energy consumption in 2020. For the planning and optimization of energy systems, an understanding of the temporal energy consumption is necessary. This paper discusses tools for estimating these load profiles. Load profiles for electricity, space heating and domestic hot water (DHW) are investigated. A total of ten tools were applied. It turns out that the selected load profiles are dependent on the field of application. Load profiles influence the results of energy system modeling and therefore it is important to differentiate load profile tools. Standardized load profiles are well suited when a large number of buildings are considered. Stochastic load profiles, behavioral load profiles and the reference load profiles are well suited for building-specific simulations. Physical load pro- files are well suited for single building models, but as soon as several buildings are considered, the input effort for a sufficient accuracy is high.
Programmierung von Open Source Software in der Energiewirtschaft nimmt seit Beginn der 2000er stetig zu. Dies gilt sowohl für den Bereich der Forschung und Entwicklung, als auch für die Industrie und Wirtschaft. So werden beispielsweise Modelle zur Planung und Optimierung von Energiesystemen umgesetzt. Eine Open Source Veröffentlichung ist in diesem Forschungsfeld besonders wichtig, um die Überprüfbarkeit von Modellannahmen sowie der Vergleichbarkeit verschiedener Modellansätze zu garantieren. Einer Open-Source Veröffentlichung stehen jedoch häufig die Hürden von hohem Fristendruck, fehlender Finanzierung und fehlendem Detailwissen der Publizierenden entgegen. Deshalb bleiben diese Softwareprodukte meist im Entwurfsstadium und sind daher schwierig wieder zu verwenden.
Mithilfe des neu erarbeiteten Schritt-für-Schritt Leitfadens zur standardisierten Implementierung einer Open Source Software, wird die Hürde und der zeitliche Aufwand zur Standardisierung von Open Source Repositories weitestgehend reduziert. Hierbei wird für jedem Bestandteil des zu standardisierenden Repositorys eine umfassende Erklärung der üblichen Standards sowie eine Empfehlung für unterstützende Softwarelösungen ausgesprochen.
Der Leitfaden orientiert sich an den aus der ISO 12207 resultierenden Phasen des Softwarelebenszyklus und ermöglicht einen Einstieg zu jedem Entwicklungsstand der Software. Seine grafische Aufbereitung in Form eines Prozessablaufplans erleichtert die Einschätzung des individuellen Status der Standardisierung eines vorliegenden Open Source Projektes. Als Treiber der Standardisierung eines Open Source Projektes sind insbesondere die bessere Lesbarkeit, Wartbarkeit und Testbarkeit der standardisierten Open Source Software wichtig.
Bei der Anwendung auf das bereits bestehende Open Source Projekt des Spreadsheet Energy System Model Genarators fiel auf, dass ein verspäteter Einstieg in ein systematisches Vorgehen (wie er mit dem Leitfaden dieser Arbeit gegeben wird) zu erheblichen Mehraufwand bei der Standardisierung führen kann. Dennoch konnten im Zuge der Umsetzung des erarbeiteten Leitfadens weitreichende Verbesserungen des Projektes vor dem Hintergrund der Standardisierung erreicht werden (z. B. Versionierung & Wartbarkeit).
Insgesamt lässt sich festhalten, dass eine frühestmögliche Standardisierung der Open Source Repositories durchgeführt werden sollte, um spätere Mehrarbeit zu vermeiden und die frühstmögliche Wiederverwendbarkeit für Dritte zu gewährleisten.
Mechanical ventilation of buildings is generally based on steadily operating systems. This field is well known and established. But, an approach based on time-varied supply flow rates might improve indoor air quality, comfort, and energy consumption. Typical time-scales of the variation are in the order of seconds or minutes. Until now, the effects of unsteady ventilation scenarios are not fully described and so, reliable dimensioning rules are missing. Hence, with a better understanding of the flow in unsteady ventilation, systems can be calculated and optimised. To understand the effective mechanisms and derive functional relations between the flow field and variation parameters, full-field optical flow measurements are executed with a particle image velocimetry (PIV) system. Experiments are conducted under isothermal conditions in water in a small-scale room model (1.00 m × 0.67 m × 0.46 m) with two swirl ceiling diffusers, Reynolds-scaling assures similarity. In a series of experiments, the effects of different unsteady ventilation strategies on the flow fields are investigated and compared to steady conditions with the same mean exchange rate. Mean exchange rates, signal types, periods, and amplitudes are varied. Time-averaged normalised velocity fields already indicate notable differences between steady and unsteady cases especially for lower exchange rates: the distribution is more homogeneous in unsteady scenarios compared to steady conditions, and low-velocity areas are reduced while the mean velocity of the room increases. So, unsteady ventilation might be beneficial in terms of improved ventilation and energy savings in partial-load operation. Fast Fourier Transformation (FFT) analyses of the mean velocity for each field over the whole series detect the main frequency of the volume flow variation. By dividing the velocity field into smaller areas, this main frequency is still detected especially in the upper part of the room, but side frequencies play a role in the room as well.
In Germany, the current sectoral urban planning often leads to inefficient use of resources, partly because municipalities lack integrated planning instruments and argumentation strength toward politics, investors, or citizens. The paper develops the ResourcePlan as (i) legal and (ii) a planning instrument to support the efficient use of resources in urban neighborhoods. The integrative, multi-methodological approach addresses the use of natural resources in the building and infrastructural sectors of (i) water (storm- and wastewater) management, (ii) construction and maintenance of buildings and infrastructure, (iii) urban energy system planning, and (iv) land-use planning. First, the development as legal instrument is carried out, providing (i) premises for integrating resource protection at all legal levels and (ii) options for implementing the ResourcePlan within German municipal structures. Second, the evaluation framework for resource efficiency of the urban neighborhoods is set up for usage as a planning instrument. The framework provides a two-stage process that runs through the phases of setting up and implementing the ResourcePlan. (Eco)system services are evaluated as well as life cycle assessment and economic aspects. As a legal instrument, the ResourcePlan integrates resource protection into municipal planning and decision-making processes. The multi-methodological evaluation framework helps to assess inter-disciplinary resource efficiency, supports the spatial identification of synergies and conflicting goals, and contributes to transparent, resource-optimized planning decisions.
Indicators for the optimization of sustainable urban energy systems based on energy system modeling
(2022)
Background: Urban energy systems are responsible for 75 % of the world's energy consumption and for 70 % of the worldwide greenhouse gas emissions. Energy system models are used to optimize, benchmark and compare such energy systems with the help of energy sustainability indicators. We discuss several indicators for their basic suitability and their response to changing boundary conditions, system structures and reference values. The most suitable parameters are applied to four different supply scenarios of a real-world urban energy system.
Results: There is a number of energy sustainability indicators, but not all of them are suitable for the use in urban energy system optimization models. Shortcomings originate from the omission of upstream energy supply chains (secondary energy efficiency), from limited capabilities to compare small energy systems (energy productivity), from excessive accounting expense (regeneration rate), from unsuitable accounting methods (primary energy efficiency), from a questionable impact of some indicators on the overall system sustainability (self-sufficiency), from the lack of detailed information content (share of renewables), and more. On the other hand, indicators of absolute greenhouse gas emissions, energy costs, and final energy demand are well suitable for the use in optimization models. However, each of these indicators only represents partial aspects of energy sustainability; the use of only one indicator in the optimization process increases the risk that other important aspects will deteriorate significantly, eventually leading to suboptimal or even unrealistic scenarios in practice. Therefore, multi-criteria approaches should be used to enable a more holistic optimization and planning of sustainable urban energy systems.
Conclusion: We recommend multi-criteria optimization approaches using the indicators of absolute greenhouse gas emissions, absolute energy costs, and absolute energy demand. For benchmarking and comparison purposes, specific indicators should be used and therefore related to the final energy demand, respectively the number of inhabitants. Our example scenarios demonstrate modeling strategies to optimize sustainability of urban energy systems.