References of "Scholzen, Frank 50003040"
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See detailEnergy performance comparison of ventilation-based heating versus water-based heating systems in an efficient residential building
Shirani, Arsalan UL; Merzkirch, Alexander; Leyer, Stephan UL et al

in Fluid Dynamics & Material Processing (in press)

The application of air-based heating systems as a possible approach to reduce the construction costs in highly efficient residential buildings is becoming popular. Air-based heating systems have been well ... [more ▼]

The application of air-based heating systems as a possible approach to reduce the construction costs in highly efficient residential buildings is becoming popular. Air-based heating systems have been well-known for their usage in passive houses during the past three decades. Available studies on such systems tend mostly to focus only on comparing exhaust air heat pump technology with conventional systems in efficient buildings. Moreover, most of the existing studies ignore the usual presence of the electrical heaters as backup. Besides, a comprehensive study and comparison between different air-based heating system concepts is still missing. In this study, four different air-based heating system concepts separated by the type of heat source of heat pump for heating and domestic hot water are defined. These systems are compared to four conventional heating system, including floor heating and direct electrical system employing dynamic annual simulations. According to simulation results, the systems with floor heating have shown the best system efficiencies and the lowest energy demand in comparison to the other systems. The main reason for this was the lower supply temperatures of the floor heating systems. Between the air heating systems, the system equipped with an outdoor air heat pump showed a better energy performance than an exhaust air system. The main reason for this could be attributed to the power limitation of exhaust air heat pump systems. [less ▲]

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See detailComparison of high-performance and conventional internal insulation materials based on hygrothermal analysis using in situ measurements and simulation
Latz, Sebastian UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Bauphysik (2022), 1

Following the European directive to reduce CO2 emissions of existing buildings by improving energy efficiency, internal insulation systems play a central role in the renovation of historically valuable ... [more ▼]

Following the European directive to reduce CO2 emissions of existing buildings by improving energy efficiency, internal insulation systems play a central role in the renovation of historically valuable buildings which cannot be insulated from the outside for reasons of monumental protection, or in cases where no additional exterior space is available. However, besides the thermal property of insulation systems, there are other relevant properties to be considered before choosing an internal insulation system, such as the hygrothermal behavior which plays a particularly important role in diffusion-open interior insulation systems. As the internal insulation layer reduces the temperature of the existing wall during the heating season, its drying potential after rain events is considerably reduced. In addition to the effects of moisture from the outside (mainly wind driven rain), the entry of humidity from the inside through diffusion plays an important role. In the presented study, high performance insulation materials with nanostructure based on silicon dioxide and polyurethane are compared to conventional material based on wood fiber from a hygrothermal point of view by analyzing in situ measurements and simulations. [less ▲]

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See detailWärmemarktstudie für das Großherzogtum Luxemburg - Eine Analyse des Wärmemarktes im Kontext nationaler Rahmenbedingungen und energiepolitischer Zielsetzungen
Bechtel, Steffen UL; Scholzen, Frank UL

in Bauphysik (2021), 42(6),

In 2020 hat Luxemburg seinen Klimaplan für den Zeitraum 2021 bis 2030 beschlossen, welcher ehrgeizige Ziele für den Wärmesektor enthält. Die Datenlage im Wärmesektor, vor allem bei der ... [more ▼]

In 2020 hat Luxemburg seinen Klimaplan für den Zeitraum 2021 bis 2030 beschlossen, welcher ehrgeizige Ziele für den Wärmesektor enthält. Die Datenlage im Wärmesektor, vor allem bei der Schlüsseltechnologie Wärmepumpe, ist jedoch unzureichend, zum Nachteil aller beteiligten Akteure. Die Universität Luxemburg hat deshalb eine Wärmemarktstudie erstellt, die Verkaufszahlen nationaler Hersteller und Händler im Zeitraum von 2014 bis 2018 auswertet und auf diese Weise wesentliche Trends im Hinblick auf die Klimaziele aufzeigt. Die Auswertung zeigt signifikante Unterschiede zur bisherigen Datenlage bei Wärmepumpen, die sich aufgrund der Nichtinanspruchnahme der staatlichen Förderung ergeben. Insgesamt werden deutlich mehr Anlagen installiert als bisher angenommen Der Absatz fossiler Heizkessel ist konstant, wobei eine Verschiebung des Energieträgers von Öl zu Erdgas zu verzeichnen ist. Der allgemeine Trend bewegt sich in Richtung der gesteckten Ziele. Dennoch besteht signifikanter Handlungsbedarf, da zum Erreichen der nationalen Klimaziele u. a. ein jährliches Wachstum des Luxemburger Wärmepumpenmarktes von 16 % bis 2030 angenommen wurde. [less ▲]

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See detailField monitoring data on a residential exhaust air heat pump system (air-to-air heat pump)
Shirani, Arsalan UL; Merzkirch, Alexander; Roesler, Jennifer et al

in Data in Brief (2021)

This data article presents the raw data used in the article “Experimental and analytical evaluation of exhaust air heat pumps in ventilation-based heating systems” (in review). The data set contains ... [more ▼]

This data article presents the raw data used in the article “Experimental and analytical evaluation of exhaust air heat pumps in ventilation-based heating systems” (in review). The data set contains measurement results of a field monitoring on a residential exhaust air heat pump system (air-to-air heat pump) in Germany. This data could be used to investigate the dynamic behaviour and performance of the exhaust air heat pump systems. The data set contains air temperature and humidity of all four sides of the heat pump unit. Moreover, the electrical consumption of the unit and the dynamic pressure difference on the exhaust side (as indication of the air volume rate) could be also found in the data set. [less ▲]

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See detailExperimental and analytical evaluation of exhaust air heat pumps in ventilation-based heating systems
Shirani, Arsalan UL; Merzkirch, Alexander UL; Roesler, Jennifer et al

in Journal of Building Engineering (2021)

Due to the significant energy loss in the building sector, energy efficiency of the buildings and their heating systems is gaining interest especially in the last decades. Application of exhaust air heat ... [more ▼]

Due to the significant energy loss in the building sector, energy efficiency of the buildings and their heating systems is gaining interest especially in the last decades. Application of exhaust air heat pumps as an energy efficient heating technology to cover the heating and venting demand of the building is becoming conventional. The exhaust air heat pumps are attracting considerable interest due to their normally reasonable price and small footprint. This heat pump type is often installed as part of an air based heating system together with electrical heaters. These electrical heaters are installed to cover the residual heating demand and/or to insure thermal comfort. The technology of exhaust air heat pumps has been investigated in several studies. Available studies on exhaust air heat pumps have tended mostly to focus on comparison between different technologies utilized in efficient buildings. Almost all of the existing studies have ignored the actual application of this technology in air based heating systems together with electrical heaters. In this sense, there is still a need for discussion on the influence of different buildings’ standards and control strategies on the heating system performance. The present paper aims to call into question the energy efficiency of exhaust air heat pumps under different boundary conditions. In this study, the results of a long time field monitoring are utilized in order to model the dynamic behavior of an exhaust air heat pump in MATLAB/Simulink. The impact of different boundary conditions on the heat pump’s efficiency is studied and additionally compared to previous studies. The developed model is used for annual simulations of air based hybrid heating systems in three different building standards. Finally, the influence of control strategy on the system performance is investigated. It is shown that under certain boundary conditions and control strategy, the studied system could provide an efficient heating system with acceptable user comfort. Nevertheless, applying conventional heating control methods or installing the system in buildings with high heating energy demand could lead to high electrical energy consumption and/or undesirable thermal comfort. [less ▲]

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See detailDesigning of the module envelope of a hybrid modular building to meet the passive house standards in Luxembourg
Rakotonjanahary, Tahiana Roland Michaël UL; Scholzen, Frank UL; Ferreira Silva, Marielle UL et al

in IOP Conference Series: Earth and Environmental Science (2020, November 20), 588(5), 052026

To face the challenges of climate change, new buildings need to be further greener while being able to ensure a minimum comfort to the tenants. Nonetheless, extensibility and flexibility could be added to ... [more ▼]

To face the challenges of climate change, new buildings need to be further greener while being able to ensure a minimum comfort to the tenants. Nonetheless, extensibility and flexibility could be added to buildings. In this context, the architect jointly with the team of this research project have designed a hybrid modular construction called “slab building” which is composed of a permanent concrete structure and several removable wooden modules. A module offers 27m² of living space but larger housings can be realized by combining two up to four modules. The aim of this paper is to design the walls of the modules to meet the criteria of nZEB. The thicknesses of the studied thermal insulations, namely rock wool, wood wool, polyurethane and aerogel, have been determined in accordance with the passive house requirements in Luxembourg. The embodied energy of the building materials has also been considered in the designing of the modules. Steady state calculations revealed that a wall thickness of 40 cm, comprising 31cm of insulation is sufficient but according to the LCA outcomes, there is no environmental benefit in having the modules comply with the AAA energy class requirements at reasonable wall thicknesses. [less ▲]

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See detailSummertime Overheating Risk Assessment of a Flexible Plug-in Modular Unit in Luxembourg
Rakotonjanahary, Tahiana Roland Michaël UL; Scholzen, Frank UL; Waldmann, Daniele UL

in Sustainability (2020)

Modular buildings offer faster construction process, provide better construction quality, allow reducing construction waste and are potentially flexible. Frames of modular units can be made of metal ... [more ▼]

Modular buildings offer faster construction process, provide better construction quality, allow reducing construction waste and are potentially flexible. Frames of modular units can be made of metal, timber, concrete or mixed materials but lightweight structures do not always allow erecting high-rise buildings and generally present a higher risk of overheating and/or overcooling. To reconcile these pros and cons, a typology of modular building called Slab was designed by a group of architects. The building is composed on the one hand of a permanent concrete structure named shelf-structure and on the other hand of several flexible removable timber modular units, also known as modules. The shelf-structure will host the common utility rooms and will serve as docking infrastructure for the housing modules. To provide high flexibility, the Slab building was designed to adapt to any orientation and location in Luxembourg. An energy concept and a HVAC systems design has been developed for the Slab building. Furthermore, a two-fold sustainability analysis was carried out. The first part of the analysis regards the determination of the minimum required wall thicknesses of the modules in accordance with Luxembourgish regulatory requirements, although the current regulation does not yet consider the Slab building typology. The second part, which is the subject of this paper, is thermal comfort assessment, more precisely, summertime overheating risk assessment of these modules, in compliance with Luxembourgish standard. In this regard, dynamic thermal simulations have been realized on two module variants; the first fulfills the passive house requirements, and the second—the current requirements for building permit application, which in principle corresponds to low energy house requirements. Simulations showed that with adequate solar shading and reinforced natural ventilation by window opening, overheating risk could be avoided for the normal residential use scenario for both module variants. [less ▲]

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See detailEco-construction for sustainable development (Econ4SD) – Konzepte für Materialbanken
Zilian, Andreas UL; Waldmann, Daniele UL; Hertweck, Florian UL et al

in Kaliske, Michael (Ed.) 24. Dresdner Baustatik-Seminar: Reality - Modeling - Structural Design (2020, October)

This contribution presents the joint research project Econ4SD – Eco-construction for sustainable development which investigates at the University of Luxembourg various aspects of sustainable design ... [more ▼]

This contribution presents the joint research project Econ4SD – Eco-construction for sustainable development which investigates at the University of Luxembourg various aspects of sustainable design, construction and operation to support a resource-efficient circular economy in the construction sector. In this context the fundamental approach of Design for deconstruction assumes a central role and is being discussed together with the complementary concept of Material banks and their digital twinning at the level of components, buildings and markets. [less ▲]

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See detailInfluence of Thermal Energy Storage and Heat Pump Parametrization for Demand-Side-Management in a Nearly-Zero-Energy-Building using Model Predictive Control
Bechtel, Steffen UL; Rafii-Tabrizi, Sasan UL; Scholzen, Frank UL et al

in Energy and Buildings (2020), 226

The rollout of the supply dependent generators wind turbines and photovoltaics leads to a flexibility demand that can be adressed from the consumer side, via Demand-Side-Management, as well. In single ... [more ▼]

The rollout of the supply dependent generators wind turbines and photovoltaics leads to a flexibility demand that can be adressed from the consumer side, via Demand-Side-Management, as well. In single family houses, the heat pump, in combination with thermal energy storage, can shift their energy comsumption according to price signals in order to reduce consumer costs. This paper analyses the impact of different heat storage sizes and heat pump powers on cost savings and shifting potential, focussing on the Luxembourgish context, when variable electricity prices based on the electricity market are applied. A model predictive controller determines the cost-optimal operating cycles of the heat pump. The building’s heat demand is predicted with the help of a neural network. The results of the parametric study show significant differences in energy efficiency and cost savings. Furthermore limitations of taking advantage of variable electicity prices due to the price structure are disclosed. The cost savings however do not give a sufficient incentive for the consumer to invest in optimizing the heating system for Demand-Side-Management purposes. By consequence, the potential and the efficiency of Demand-Side-Management are limited and further incentives are necessary. [less ▲]

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See detailEvaluation von bauphysikalischen Vormessungen im Rahmen von komplexen Innendämmprojekten
Latz, Sebastian UL; Thewes, Andreas; Scholzen, Frank UL et al

in Vogel, Albert (Ed.) Bauphysiktage 2019 in Weimar - Bauphysik in Forschung und Praxis (2019, September 25)

The installation of internal insulation systems within the scope of refurbishment changes the hygrothermal behaviour of the existing masonry of a building in the long term. The internal insulation layer ... [more ▼]

The installation of internal insulation systems within the scope of refurbishment changes the hygrothermal behaviour of the existing masonry of a building in the long term. The internal insulation layer reduces the temperature of the masonry during the heating period and considerably reduces the drying potential. If the moisture content is too high due to the absorption of driving rain from the outside and moisture from the interior climate, the masonry may be permanently damaged and mould may form. The proof of function can be achieved by hygrothermal simulations. These simulations require the input of sensitive boundary conditions and different material parameters. In order to obtain precise simulation results, these input values should be validated by building physics measurements. In order to be able to better assess the simulation parameters, various physical measurements for the preparation of a field test for interior insulation systems in a conference room were carried out on behalf of the administration of the bâtiments publics at the University of Luxembourg as part of the research project "Possibilities and limitations of interior insulation in the renovation of public buildings in Luxembourg". [less ▲]

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See detailInbetriebnahme und Monitoring einer Feldtestfläche zur außenliegenden Lufttemperierung
Schmidt, Christoph Wilhelm UL; Altgeld, Horst; Groß, Bodo et al

in Völker, Conrad; Kornadt, Oliver; Jentsch, Mark (Eds.) et al Schriftenreihe der Professur Bauphysik, Bauphysiktage 2019 in Weimar - Bauphysik in Forschung und Praxis (2019, September 25)

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II ... [more ▼]

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II, Förderkennzeichen 0327370Y) zugeordnet. Im Rahmen des Pro-jektes wurde ein Großdemonstrator mit außenliegender Wand- und Lufttemperierung (kurz aWT & aLT) zusammen mit einem niederexergetischen Versorgungssystem, bestehend aus Eisspeicher, Wärmepumpe und PVT-Hybridkollektoren realisiert. Zur Heizperiode 2018/19 wurde die „Feldtestanlage“ in Betrieb genommen, sodass derzeit Messdaten generiert wer-den. In dem Forschungsprojekt wird der Demonstrator über eine Heizperiode und eine Kühl-periode messtechnisch begleitet und ausgewertet. Dabei wird der Großdemonstrator und alle Komponenten umfassend messtechnisch ausgewertet (~300 Messwerte). Ziel des Beitrags ist eine Darstellung der Grundlagen der außenliegenden Lufttemperierung, als niederexergetische und schnell regelbare Ergänzung zur außenliegenden Wandtemperie-rung. Bei der außenliegenden Lufttemperierung wird zwischen thermisch aktivierter Be-standswand und neuem Wärmedämm-Verbundsystem ein Luftspalt geschaffen, durch den Außenluft geführt und temperiert werden kann. Diese temperierte Außenluft wird dem dahin-terliegenden Raum (im Feldtest ein Büroraum mit rund 20 m² Grundfläche und zwei Arbeits-plätzen) als Frischluft zur Verfügung gestellt. Aufbauend auf den Grundlagen wird die Inbe-triebnahme der bereits umgesetzten Feldtestfläche mit möglichen Regelstrategien geschildert. Abschließend sollen erste Messergebnisse der Feldtestfläche dargestellt und diskutiert wer-den. Interessant sind hier vor allem (im Vergleich zur außenliegenden Wandtemperierung) die möglichen Zeitkonstanten und die erreichbaren Wärmeströme nach Innen (z.B. mögliche Wärmeübertragung als Kombination aus Konvektion im Luftspalt und Wärmeleitung durch die Bestandswand). Themengebiet: Energieeffiziente Gebäude & Bauphysik und Sanierung & Behaglichkeit und Raumklima [less ▲]

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See detailAuswertung eines Großdemonstrators mit außenliegender Wandtemperierung, Wärmepumpe, Eisspeicher und PTV-Hybridkollektoren
Schmidt, Christoph Wilhelm UL; Altgeld, Horst; Groß, Bodo et al

in Völker, Conrad; Kornadt, Oliver; Jentsch, Mark (Eds.) et al Schriftenreihe der Professur Bauphysik, Bauphysiktage 2019 in Weimar - Bauphysik in Forschung und Praxis (2019, September 25)

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II ... [more ▼]

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II, Förderkennzeichen 0327370Y) zugeordnet. Im Rahmen des Pro-jektes wurde ein Großdemonstrator mit außenliegender Wand- und Lufttemperierung (kurz aWT & aLT) zusammen mit einem niederexergetischen Versorgungssystem, bestehend aus Eisspeicher, Wärmepumpe und PVT-Hybridkollektoren realisiert. Zur Heizperiode 2018/19 wurde die „Feldtestanlage“ in Betrieb genommen, sodass derzeit Messdaten generiert wer-den. In dem Forschungsprojekt wird der Demonstrator über eine Heizperiode und eine Kühl-periode messtechnisch begleitet und ausgewertet. Dabei wird der Großdemonstrator und alle Komponenten umfassend messtechnisch ausgewertet (~300 Messwerte). Ziel des Beitrags ist eine Darstellung der messtechnischen Auswertung des Großdemonstra-tors über die aktuelle Heizperiode (2018/19) und die anstehende Kühlperiode (2019). Der Fo-kus der Auswertung liegt auf der Feldtestfassade der außenliegenden Wandtemperierung und adressiert die folgenden Fragestellungen: - Konnten die theoretischen Ergebnisse aus Berechnung und Simulation reproduziert werden? - Welche Heizleistungen sind über die außenliegende Wandtemperierung übertragbar? - Welches Fazit kann nach dem Betrieb der Anlage/Feldtestfläche über ca. ein Jahr ge-zogen werden? Je nach aktuellem Stand der begleitenden Simulations- und Potentialstudien können auch hier erste Ergebnisse präsentiert werden. Inhaltlich baut der Beitrag auf dem Beitrag „Außen-liegende Wand- und Lufttemperierung: Umsetzung eines Großdemonstrators“ von den Bau-physiktagen 2017 in Kaiserslautern auf. Im Anschluss an die dort beschriebene Umsetzung soll nun ein Fazit bzgl. Umsetzung, Monitoring und Simulation gezogen werden. [less ▲]

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See detailOptimal Operation of Nearly Zero Energy Buildings using Mixed Integer Linear Programming
Rafii-Tabrizi, Sasan UL; Hadji-Minaglou, Jean-Régis UL; Scholzen, Frank UL et al

Scientific Conference (2019, September 10)

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 ... [more ▼]

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. [less ▲]

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See detailDemand-Side-Management Potentials for Heat-Pumps in Residential Buildings
Bechtel, Steffen UL; Rafii-Tabrizi, Sasan UL; Scholzen, Frank UL et al

Scientific Conference (2019, September 02)

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 ... [more ▼]

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. [less ▲]

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See detailMixed Integer Linear Programming Model for the Optimal Operation of a Dual Source Heat Pump
Rafii-Tabrizi, Sasan UL; Hadji-Minaglou, Jean-Régis UL; Scholzen, Frank UL

Scientific Conference (2019, April 24)

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 ... [more ▼]

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. [less ▲]

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See detailModellierung und Validierung von Simulationsansätzen für die aussenliegende Lufttemperierung
Schmidt, Christoph Wilhelm; Scholzen, Frank UL; Maas, Stefan UL et al

in Tagungsband BauSim 2018 (2018, September)

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See detailLEXU II „Low Exergy Wall & Air Tempering for Building Refurbishment“
Schmidt, Christoph Wilhelm; Scholzen, Frank UL

Scientific Conference (2018, April 20)

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See detailImpact of the height imperfections of masonry blocks on the load bearing capacity of dry-stack masonry walls
Chewe Ngapeya, Gelen Gael UL; Waldmann, Danièle UL; Scholzen, Frank UL

in Journal of Construction and Building Materials (2018), 165

Dry-stacked masonry walls gives rise to geometric imperfections: the height variation of different masonry blocks ΔH and the roughness of the support area Δh. This paper studies the effect of ΔH on the ... [more ▼]

Dry-stacked masonry walls gives rise to geometric imperfections: the height variation of different masonry blocks ΔH and the roughness of the support area Δh. This paper studies the effect of ΔH on the structural response and the load bearing capacity of masonry walls by highlighting the load percolation. Furthermore, an algorithm was developed to define a stress multiplier coefficient respecting the imperfections ΔH. The algorithm allowed predicting 77% of the amplified stress compared to the FE analysis and showed that the geometric imperfections govern the load percolation in a wall as well as the cracking mode and the bearing capacity. [less ▲]

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