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Using optimization to design a renewable energy system has become a computationally demanding task as the high temporal fluctuations of demand and supply arise within the considered time series. The aggregation of typical operation periods has become a popular method to reduce effort. These operation periods are modelled independently and cannot interact in most cases. Consequently, seasonal storage is not reproducible. This inability can lead to a significant error, especially for energy systems with a high share of fluctuating renewable energy. The previous paper, “Time series aggregation for energy system design: Modeling seasonal storage”, has developed a seasonal storage model to address this issue. Simultaneously, the paper “Optimal design of multi-energy systems with seasonal storage” has developed a different approach. This paper aims to review these models and extend the first model. The extension is a mathematical reformulation to decrease the number of variables and constraints. Furthermore, it aims to reduce the calculation time while achieving the same results.
This study focuses on thermoelectric elements (TEE) as an alternative for room temperature control. TEE are semi-conductor devices that can provide heating and cooling via a heat pump effect without direct noise emissions and no refrigerant use. An efficiency evaluation of the optimal operating mode is carried out for different numbers of TEE, ambient temperatures, and heating loads. The influence of an additional heat recovery unit on system efficiency and an unevenly distributed heating demand are examined. The results show that TEE can provide heat at a coefficient of performance (COP) greater than one especially for small heating demands and high ambient temperatures. The efficiency increases with the number of elements in the system and is subject to economies of scale. The best COP exceeds six at optimal operating conditions. An additional heat recovery unit proves beneficial for low ambient temperatures and systems with few TEE. It makes COPs above one possible at ambient temperatures below 0 ∘C. The effect increases efficiency by maximal 0.81 (from 1.90 to 2.71) at ambient temperature 5 K below room temperature and heating demand Q˙h=100W but is subject to diseconomies of scale. Thermoelectric technology is a valuable option for electricity-based heat supply and can provide cooling and ventilation functions. A careful system design as well as an additional heat recovery unit significantly benefits the performance. This makes TEE superior to direct current heating systems and competitive to heat pumps for small scale applications with focus on avoiding noise and harmful refrigerants.
Das Forschungsvorhaben Optiox beschäftigt sich mit der Optimierung eines Belüftungsbeckens zur Rauchgasentschwefelung fossil befeuerter Kraftwerke mittels Seewasser. Unter Neutralisierung der entstehenden Hydroniumionen (H3O+) durch die natürliche Alkalität des Seewassers dissoziiert Schwefeldioxid aus dem Rauchgase im vorgeschalteten Absorber beim Phasenübergang von der Gas- in die Flüssigphase zu Sulfiten. Im Belüftungsbecken werden diese Sulfite mittels eingeblasener Luft zu Sulfaten oxidiert, was zu einer geringen Erhöhung der Sulfatfracht vor Einleitung ins Meer führt, die unterhalb der natürlichen Schwankungen liegt. Daneben dient das Belüftungsbecken der Konditionierung des Seewassers hinsichtlich pH-Wert und Sauerstoffgehalt und ist mit hoch effizienten Belüftern ausgestattet, deren Spezifikation den jeweiligen Randbedingungen, wie Abscheideleistung des Absorbers, Beckengeometrie sowie lokalen Gegebenheiten angepasst wird.
Even though BIM (Building Information Modelling) is successfully implemented in most of the world, it is still in the early stages in Germany, since the stakeholders are sceptical of its reliability and efficiency. The purpose of this paper is to analyse the opportunities and obstacles to implementing BIM for prefabrication. Among all other advantages of BIM, prefabrication is chosen for this paper because it plays a vital role in creating an impact on the time and cost factors of a construction project. The project stakeholders and participants can explicitly observe the positive impact of prefabrication, which enables the breakthrough of the scepticism factor among the small-scale construction companies. The analysis consists of the development of a process workflow for implementing prefabrication in building construction followed by a practical approach, which was executed with two case studies. It was planned in such a way that, the first case study gives a first-hand experience for the workers at the site on the BIM model so that they can make much use of the created BIM model, which is a better representation compared to the traditional 2D plan. The main aim of the first case study is to create a belief in the implementation of BIM Models, which was succeeded by the execution of offshore prefabrication in the second case study. Based on the case studies, the time analysis was made and it is inferred that the implementation of BIM for prefabrication can reduce construction time, ensures minimal wastes, better accuracy, less problem-solving at the construction site. It was observed that this process requires more planning time, better communication between different disciplines, which was the major obstacle for successful implementation. This paper was carried out from the perspective of small and medium-sized mechanical contracting companies for the private building sector in Germany.
We present first results from a newly developed monitoring station for a closed loop geothermal heat pump test installation at our campus, consisting of helix coils and plate heat exchangers, as well as an ice-store system. There are more than 40 temperature sensors and several soil moisture content sensors distributed around the system, allowing a detailed monitoring under different operating conditions.In the view of the modern development of renewable energies along with the newly concepts known as Internet of Things and Industry 4.0 (high-tech strategy from the German government), we created a user-friendly web application, which will connect the things (sensors) with the open network (www). Besides other advantages, this allows a continuous remote monitoring of the data from the numerous sensors at an arbitrary sampling rate.Based on the recorded data, we will also present first results from numerical simulations, taking into account all relevant heat transport processes.The aim is to improve the understanding of these processes and their influence on the thermal behavior of shallow geothermal systems in the unsaturated zone. This will in turn facilitate the prediction of the performance of these systems and therefore yield an improvement in their dimensioning when designing a specific shallow geothermal installation.
Die bei Kohlekraftwerksprozessen entstehenden Rauchgase enthalten einen nicht unerheblichen Teil an Schadgaskomponenten (z.B. Stickoxide), die aus dem Gasstrom entfernt werden müssen. Im Rahmen von Forschungsvorhaben des BMBF und verschiedener Industriepartner betreibt der Lehrstuhl für Wärmeübertragung und Klimatechnik der RWTH Aachen Pilotanlagen und Prüfstände für Untersuchungen auf dem Gebiet der homogenen und heterogen-katalytischen Schadstoffreduktion heißer Rauchgase bei Temperaturen bis zu 900 °C. Für die Erforschung der Minderungspotentiale geeigneter, auf Distickstoffoxid reduzierend wirkender Additive, wie Wasserstoffperoxid, oder auch Katalysatoren, befindet sich ein Reaktor in Betrieb, der eine Untersuchung der Reaktionskinetik bei der Entfernung von Schadgaskomponenten aus einem lnertgasstrom ermöglicht. Wesentlich für den Erfolg der Forschungsarbeit ist eine auf das spezielle Projekt genau abgestimmte Meß- und Regelungstechnik. Neben der Auswahl geeigneter Hardwarekomponenten ist auch die Softwareentwicklung unter einer leistungsstarken und zuverlässigen Programmierumgebung von großer Bedeutung. Hierbei dient die unter LabVIEW 5.01 entwickelte Datenerfassung- und Auswertesoftware zum einen der Messung, Visualisierung und Regelung der relevanten Temperaturen, Drücke, Konzentrationen und Volumenströme einzelner Gaskomponenten. Zum anderen ermöglicht sie parallel eine numerische Simulation der Vorgänge innerhalb des Reaktors zur Anpassung reaktionskinetischer Parameter aus den sich ergebenden Versuchsdaten durch Lösung eindimensionaler, stationärer Erhaltungsgleichungen.