http://hdl.handle.net/10993/87 Search this channel search http://orbilu.uni.lu/simple-search http://hdl.handle.net/10993/41980 Title: A DEM modeling of biomass fast pyrolysis in a double auger reactor <br/> <br/>Author, co-author: Qi, Fenglei; Wright, Mark <br/> <br/>Abstract: Thermochemical conversion of biomass via fast pyrolysis is a proven pathway to product low-carbon crude bio-oils. In this research, an extended discrete element method (DEM) is proposed for simulating biomass fast pyrolysis reacting granular flows in a double auger reactor, in which particle hydrodynamics and interparticle heat transfer processes are involved and coupled with chemical reactions in solid particles. An adaptive time step algorithm is proposed to achieve a stable coupling between the integration of reaction ordinary differential equations and the DEM solver, and the algorithm is proven computationally efficient. A multi-component fast pyrolysis kinetics is adopted and its modeling accuracy is assessed by carrying out simulations of benchmark biomass pyrolysis experiments and comparing the prediction results with experimental data. The predicted product yields of bio-oil, char and non-condensable gas from the simulation of the biomass fast pyrolysis in the auger reactor are in satisfactory agreement with experimental measurements. The decomposition rates of biomass components in the reactor are revealed from the simulation and the pyrolysis number Py is calculated from the decomposition rate of biomass and the heat transfer coefficient. The Py number illustrates that the biomass fast pyrolysis process is limited by the heat transfer process at particle size of 2 mm. http://hdl.handle.net/10993/41741 Title: Optimal Operation of Nearly Zero Energy Buildings using Mixed Integer Linear Programming <br/> <br/>Author, co-author: Rafii-Tabrizi, Sasan; Hadji-Minaglou, Jean-Régis; Scholzen, Frank; Capitanescu, Florin <br/> <br/>Abstract: This paper proposes a deterministic mixed integer linear programming model for the optimal operation of an energy system providing thermal and electrical energy for a residential and commercial nearly zero energy building. The space heating and space cooling demand of the buildings is simulated using a resistive-capacitive model within a quadratic program respectively. Thermal energy for space heating, space cooling and domestic hot water is buffered in thermal energy storage systems. A dual source heat pump provides thermal energy for space heating and domestic hot water, whereas space cooling is covered by an underground ice storage. The environmental energy sources of the heat pump are ice storage or wind infrared sensitive collectors. The collectors are further used to regenerate the ice storage. Further space heating demands are covered by a combined heat and power unit, which also produces electricity. Photovoltaic panels produce electrical energy which can be stored in a battery storage system. The electrical energy system is capable of selling and buying electricity from the public power grid. A mixed integer linear programming model is developed to minimise the operation cost of the combined commercial and residential nearly zero energy building over a scheduling horizon of 24h. The developed model is tested on two typical days, which are representative for the summer and winter season. Furthermore, it is investigated how external incentives such as varying electricity prices impact the optimal scheduling of the energy system. http://hdl.handle.net/10993/41739 Title: Mixed Integer Linear Programming Model for the Optimal Operation of a Dual Source Heat Pump <br/> <br/>Author, co-author: Rafii-Tabrizi, Sasan; Hadji-Minaglou, Jean-Régis; Scholzen, Frank <br/> <br/>Abstract: This paper presents a mixed integer linear programming (MILP) model to optimally operate a dual source heat pump (DSHP). The DSHP draws environmental energy from an underground ice storage tank (IST) or wind infrared sensitive collectors (WISC). WISC is further used to regenerate the IST. The thermal output of the DSHP is stored in a thermal energy storage (TES). A single-objective optimization approach is applied to minimize the operational cost of the DSHP over a scheduling horizon of 24h. The developed framework is tested on various days, which are representative for each season of the year. Furthermore, it is investigated how variable electricity price market data influence the dynamic behaviour of the DSHP. http://hdl.handle.net/10993/41733 Title: Demand-Side-Management Potentials for Heat-Pumps in Residential Buildings <br/> <br/>Author, co-author: Bechtel, Steffen; Rafii-Tabrizi, Sasan; Scholzen, Frank; Hadji-Minaglou, Jean-Régis <br/> <br/>Abstract: The rollout of volatile renewable energies, within the European Union creates a need for flexibility, which in turn can be solved with Demand-Side-Management. Heat pumps in single-family houses can contribute by adapting their consumption towards price signals, boosting the integration of renewable energies at the same time. Studies so far only focus on Nearly-Zero-Energy-Buildings neglecting the potential of buildings with lower energy standard. This paper illustrates the load shifting potential of two reference-building types by the means of thermal simulation. Therefore, a designed control unit adapts the operation times of the heat pump according to spot market price signals while simultaneously sustaining indoor comfort. The results show remarkable cost reductions achieved by load shifting for both cases. In addition, the approach of this study facilitates the projection of Demand-Side-Management potentials of whole regions. http://hdl.handle.net/10993/41292 Title: Flexibler nachfrageorientierter Betrieb von Biogasanlagen durch 2-stufiges Verfahrenskonzept <br/> <br/>Author, co-author: Greger, Manfred <br/> <br/>Abstract: Der steigende Anteil von erneuerbarer Energie im Mix der Stromerzeugung mit den erheblichen bekannten Fluktuationen bei Wind- und Photovoltaikanlagen führt zu einer steigenden Diskrepanz zwischen der Stromerzeugung und seiner Nachfrage. Bisher wird die Stromerzeugung aus Biogasanlagen mehr oder weniger konstant gefahren. Allerdings könnte dies in Zukunft mehr zum Ausgleich der Stromerzeugung und Nachfrage genutzt werden wozu jedoch größere Puffervolumina erforderlich sind. Hierzu könnte eine interessante Variante des Zwei-Stufen-Prozesses verwendet werden. Die erste Stufe wird dabei mit höherer Belastung und kurzer Verweilzeit bei relativ niedrigen pH-Werten betrieben und es entstehen im Wesentlichen flüssige Zwischenprodukte (und nur wenig Gas). Der Ablauf der ersten Stufe kann dann in relativ kleinen Flüssigkeitsbehältern zwischengelagert werden und bei Bedarf der zweiten Stufe zugeführt werden, in der die Weiterreaktion zum Biogas stattfindet. Die vorgestellte Variante hat gegenüber der Zwischen-Speicherung von Biogas den Vorteil, dass die erforderlichen Speicher-Volumina deutlich kleiner ausfallen. http://hdl.handle.net/10993/40765 Title: Energy efficiency and indoor aire quality os seminar rooms in older buildings with and without mechanical ventilation <br/> <br/>Author, co-author: Maas, Stefan; da Cruz Antunes, Joël; Steffgen, Georges <br/> <br/>Abstract: The present paper reports on an experimental study performed in a seminar room of the University of Luxembourg in a building of the 1970ies without a major renovation. This lecture room is typical for this building period and has a capacity of 60 seats. It is equipped with a mechanical ventilation system that is normally in operation on workdays for 11 hours a day in semester periods (8:00-19:00h), while windows can be opened manually. A Blower-Door-Test revealed that the room is not airtight. During a year, the ventilation system was shut “on” and “off” in periods of some weeks and the consumed final-energy was measured, as well as the indoor climate assessed by physical and psychological measurements. For instance, the measured CO2 concentrations are marginally better with the ventilation system "on", which was not perceived in any way by the occupants during the investigations. It was not possible to properly identify the impact of ventilation on the consumed heat-energy, as the room could not be thermally separated from the rest of the building. But with the system “on” there was a clear increase in consumed primary energy due to the electric consumption of the fans. No relationship between the perceived percentage of dissatisfied and perceived climate could be observed. It is concluded that the typical normal operation modus is questionable for seminar rooms in older buildings with variable occupancy and that a simple shut down or semi-automatic user controlled modus by low-cost retrofit seems advantageous. <br/> <br/>Commentary: - http://hdl.handle.net/10993/40728 Title: Entwicklung und Modellierung eines Hybrid-Solarmodulkollektor-basierten Wärmepumpensystems auf der Basis von CO2 Direktverdampfung in Mikrokanälen <br/> <br/>Author, co-author: Rullof, Johannes <br/> <br/>Abstract: As early as the end of the 1970s, heat pumps in combination with glycol-based large-area combined radiation environmental heat absorbers were developed as evaporators which, in comparison to forced convection-based air heat pumps, not only used ambient energy but also solar energy as an energy source. However, due to the falling oil prices after the oil crisis, this technology, which was for the most part not yet economical and moreover required large absorber surfaces, could not prevail. Due to the significant re-duction in the heating requirement of new buildings, nowadays much smaller absorber surfaces are needed in combination with a heat pump, which leads to a renewed interest in the combination of heat pumps and absorbers. Above all, the combination of thermal absorber, based on free convection and radiation, and photovoltaic (PV) in one module (PVT module), may be an alternative to forced convection-based air heat pumps. The use of solar energy as the heat source of the heat pump leads one to expect higher coef-ficients of performance by achieving higher evaporation temperatures than conventional forced convection-based air heat pumps. Numerous publications describe the market potential of solar hybrid modules with di-rect evaporation (PVT-direct module), and several theoretical studies describe con-structive approaches and related calculations. However, to date, there is still no practi-cal implementation of a PVT hybrid module in combination with a module-integrated direct evaporation of the natural refrigerant CO2 in microchannels. So far, no experi-mental studies on CO2-PVT-based heat pump systems with direct evaporation have been carried out by research institutions. Thus, the proof of the constructive and func-tional feasibility of a CO2-based PVT-direct module as well as the energetic feasibility of the PVT-based CO2 heat pump system is still a desideratum. The three objectives of this work can be summarized as follows: 1. Development and production of the PVT-direct module for the analysis of the constructional feasibility of the PVT-direct module 2. Experimental investigation of the PVT-direct module for the analysis of both the thermal and electrical functional feasibility of the PVT-direct module 3. Analysis of the energetic feasibility of the PVT-based CO2 heat pump system http://hdl.handle.net/10993/38927 Title: Energy policies for eco-friendly households in Luxembourg—a study based on the LuxHEI model <br/> <br/>Author, co-author: Poncin, Stéphane Louis Maxim <br/> <br/>Abstract: In the Grand Duchy of Luxembourg, the residential building sector is a major energy consumer and greenhouse gases emitter that is considered key in achieving the country's climate goals. The purpose of this paper is to assess the effectiveness of the most important policy instruments in achieving savings in the final energy consumption and direct CO2 emissions of Luxembourgish households. Our study is based on the LuxHEI model, which is an enhanced and upgraded version of the well-known French simulation model Res-IRF. This variant has been adjusted to the particular problems of a small country with growing economy and a quickly increasing population. The LuxHEI model goes beyond standard energy-economy models by incorporating global warming as a decision-making factor. The model outcomes reveal that total environmental and economic effectiveness increases if energy policy tools are applied concurrently. In 2060, and compared to the no-policy baseline scenario, the most aspirational policy mix enables energy savings of 42% and an emission mitigation of 60%. From our results we can draw the following policy implications: for a significant improvement of the sector's energy efficiency and sufficiency, (1) the implementation of a remediation duty for existing buildings and (2) the tightening of the performance standards for new constructions, (3) combined with a national carbon tax, are crucial. http://hdl.handle.net/10993/38700 Title: Hybrid-Solarmodulkollektor auf der Basis von CO2 Direktverdampfung in Mikrokanälen - PVT-direkt <br/> <br/>Author, co-author: Rullof, Johannes http://hdl.handle.net/10993/38699 Title: Modellierung eines PVT-basierten Wärmepumpensystems auf der Basis von CO2 Direktverdampfung <br/> <br/>Author, co-author: Rullof, Johannes; Lambers, Klaus Jürgen; Blieske, Ulf; Künkel, Felix; Hadji-Minaglou, Jean-Régis; Scholzen, Frank <br/> <br/>Abstract: Die Systemkombination aus Wärmepumpe und solarthermischen Absorber, basierend auf freier Konvektion und Strahlung, und Photovoltaik (PV) in einem Modul (PVT-Modul) kann aufgrund der Reduzierung des Heizwärmebedarfs von Gebäuden und des verstärkten Betriebs von Wärmepumpen während der Niedrigstrompreiszeiten am Tage und dem damit verbundenen höheren Strahlungsanteil der Umweltwärme zukünftig eine Alternative zu zwangskonvektions-basierten Luft-Wärmepumpen sein. Der Beitrag beschäftigt sich mit einem CO2-Wärmepumpensystem, bestehend aus einem neuartigen Solar-Hybridmodul, welches einen mikrokanal-basierten Verdampfer einer CO2-Wärmepumpe mit einem PV-Modul vereint (PVT-direkt). Um die Machbarkeit des neuartigen PVT-direkt-Wärmepumpensystems zu demonstrieren, wird im Rahmen eines Forschungsprojekts ein funktionsfähiges PVT-direkt-Modul konstruiert und schließlich als Teil eines CO2-Wärmepumpensystems getestet und modelliert. Die Besonderheit der Kombination eines thermischen Absorbers mit einer Wärmepumpe liegt in der Erschließung der Solarenergie und Umgebungsenergie als Energiequelle. Hierbei ist die Kenntnis über die thermische Leistung des PVT-Moduls unter anderem durch den konvektiven Wärmeübergang zwischen dem PVT-Modul und der Umgebung relevant. Sowohl der Modulneigungswinkel (Anströmwinkel) und die Windrichtung (Azimutwinkel) haben einen nicht zu vernachlässigenden Einfluss auf den resultierenden Wärmeübergangskoeffi-zienten der erzwungenen Konvektion. Da im Rahmen einer Literaturrecherche keine für das PVT-Modul direkt zu übertragenden experimentelle Untersuchungen und Berechnungsgrundlagen zur Bestimmung des konvektiven Wärmeübergangs gefunden werden konnten, wurde mit Hilfe der Software ANSYS Fluent eine CFD-Simulation zum konvektiven Wärmeübergang am PVT-Modul durchgeführt, deren Ergebnisse in dieser Arbeit präsentiert werden. http://hdl.handle.net/10993/38698 Title: Development of a Control Strategy for a PVT-based CO2 Heat Pump <br/> <br/>Author, co-author: Rullof, Johannes; Lambers, Klaus Jürgen; Blieske, Ulf; Hadji-Minaglou, Jean-Régis; Scholzen, Frank <br/> <br/>Abstract: In recent years, the possibility of combining photovoltaics (PV) and solar thermal collectors into one solar hybrid module (PVT-module) has been increasingly investigated. PVT-modules produce thermal and electrical energy at the same time. Since the efficiency of a photovoltaic module decreases with increasing temperature, the temperature of the heat transfer media is often limited to about 30 °C and the PVT-module is combined with a heat pump, which increases the temperature on the “warm side”. A common approach is to integrate the PVT-module directly as an evaporator in a heat pump system (PVT-direct). This paper presents the development of a control strategy for a PVT-based CO2 heat pump that takes into account solar radiation, ambient temperature, wind speed, evaporator temperature and compressor power. The developed control strategy provides different operating modes depending on the solar radiation supply as well as the ambient temperature. http://hdl.handle.net/10993/38697 Title: Entwicklung eines PV/Thermie-basierten Wärmepumpensystems auf der Basis von CO2 Direktverdampfung <br/> <br/>Author, co-author: Rullof, Johannes; Lambers, Klaus Jürgen; Blieske, Ulf; Hadji-Minaglou, Jean-Régis; Scholzen, Frank http://hdl.handle.net/10993/37262 Title: A data-driven methodology to support pump performance analysis and energy effiency optimization in wastewater treatment plants <br/> <br/>Author, co-author: Torregrossa, Dario; Hansen, Joachim; Hernandez-Sancho, Francesc; Cornelissen, Alex; Schutz, Georges; Leopold, Ulrich <br/> <br/>Abstract: Studies and publications from the past ten years demonstrate that generally the energy efficiency of Waste Water Treatment Plants (WWTPs) is unsatisfactory. In this domain, efficient pump energy management can generate economic and environmental benefits. Although the availability of on-line sensors can provide high-frequency information about pump systems, at best, energy assessment is carried out a few times a year using aggregated data. Consequently, pump inefficiencies are normally detected late and the comprehension of pump system dynamics is often not satisfactory. In this paper, a data-driven methodology to support the daily energy decision-making is presented. This innovative approach, based on fuzzy logic, supports plant managers with detailed information about pump performance, and provides case-based suggestions to reduce the pump system energy consumption and extend pump life spans. A case study, performed on a WWTP in Germany, shows that it is possible to identify energy inefficiencies and case-based solutions to reduce the pump energy consumption by 18.5%. http://hdl.handle.net/10993/36963 Title: Presentation: "Mesophilic and Thermophilic Anaerobic Digestion of Model Kitchen Waste with Variation of Fat Content" <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus http://hdl.handle.net/10993/36962 Title: Mesophilic and Thermophilic Anaerobic Digestion of Model Kitchen Waste with Variation of Fat Content <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus <br/> <br/>Abstract: Synthetic kitchen waste, produced on basis of a real kitchen waste, and two of its variations are studied. Previous study showed that the fermentation of kitchen waste was similar to the degradation of synthetic kitchen waste, further called model kitchen waste (MKW) with the same amounts of carbohydrates, fats and proteins. In this study the anaerobic degradation of this MKW (named MKW1; 23 % rapeseed oil) was investigated under mesophilic and thermophilic conditions at 2 different loadings. Additional experiments were performed with lower (MKW2; 14.7 %) and higher (MKW3; 27.2 %) rapeseed oil content at the expense of starch. An organic loading of 5 gVS/l leads to a fast and undisturbed degradation under mesophilic conditions. The volatile fatty acids (mainly acetic acid) appeared only during the first 3 days. Finally the amount of biogas been produced is weakly correlated with the oil content. Under thermophilic conditions the biogas production was retarded and the concentrations of the volatile fatty acids were generally higher whereas acetic acid was present for a period of 10 days. The final biogas amount was higher than compared to mesophilc conditions. At a higher loading of 25 gVS/l a strong retardation of biogas production was observed which correlates with very high concentrations of volatile fatty acids over the whole runtime period of 50 days. http://hdl.handle.net/10993/36723 Title: Two-Stage Process - a More Flexible Power Production of Biogas <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Benito Martin, Patricia Cristina; Greger, Manfred; Schlienz, Markus http://hdl.handle.net/10993/36722 Title: Vergleich der anaeroben Vergärung von realem und synthetischem Küchenabfall in Batchversuchen unterschiedlicher Beladung <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus <br/> <br/>Abstract: In the following article comparison between real kitchen waste and a synthetic kitchen waste is made. In total four experiments are discussed, all of them were conducted in batch mode at two different loadings: 25 and 5 goDM/l and two different temperatures: mesophilic and thermophilic. http://hdl.handle.net/10993/36652 Title: Präsentation: Vergleich der anaeroben Vergärung von realem und synthetischem Küchenabfall in Batchversuchen unterschiedlicher Beladung <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus http://hdl.handle.net/10993/36602 Title: EU Energy Law Vol. III,Renewable Energy in the member states of the EU, Chapter 17 Luxemburg <br/> <br/>Author, co-author: Greger, Manfred; Benito, Patricia <br/> <br/>Abstract: Description of the main policy instruments and the legislative framework in the field of renewable energies in Luxemburg http://hdl.handle.net/10993/36125 Title: Development of a Data-Driven Approach based on Kalman filtering for CFD Reactor Analysis <br/> <br/>Author, co-author: Introini, Carolina; Cammi, Antonio; Lorenzi, Stefano; Baroli, Davide; Peters, Bernhard <br/> <br/>Abstract: In the last several years, computer-based simulation has become an important analysis and design tool in many engineering fields. The common practice involves the use of low-fidelity models, which in most cases are able to provide fairly accurate results while maintaining a low computational cost. However, for complex systems such as nuclear reactors, more detailed models are required for the in-depth analysis of the problem at hand, due for example to the complex geometries of the physical domain. Nevertheless, such models are affected by potentially critical uncertainties and inaccuracies. In this context, the use of data assimilation methods such as the Kalman filter to integrate local experimental data witihin the numerical model looks very promising as a high-fidelity analysis tool. In this work, the focus is the application of such methods to the problem of fluid-dynamics analysis of the reactor. Indeed, in terms of nuclear reactor investigation, a detailed characterization of the coolant behaviour within the reactor core is of manda- tory importance in order to understand, among others, the operating conditions of the system, and the potential occurrence of accident scenarios. In this context, the use of data assimilation methods allows the extraction of information of the thermo-dynamics state of the system in a benchmarked transitory in order to increase the fidelity of the com- putational model. Conversely to the current application of control-oriented black-box in the nuclear energy community, in this work the integration of the data-driven paradigm into the numerical formulation of the CFD problem is proposed. In particular, the al- gorithm outlined embeds the Kalman filter into a segregated predictor-corrector formu- lation, commonly adopted for CFD analysis. Due to the construction of the developed method, one of the main challenges achieved is the preservation of mass-conservation for the thermo-dynamics state during each time instant. As a preliminary verification, the proposed methodology is validated on a benchmark of the lid-driven cavity. The obtained results highlight the efficiency of the proposed method with respect to the state-of-art low fidelity approach.