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AbstractChemical looping combustion is a highly efficient CO2 separation technology without direct contact between combustion air and fuel. A metal oxide is used as an oxygen carrier in dual fluidized beds to generate clean CO2. The use of biomass is the focus of current research because of the possibility of negative CO2 emissions and the utilization of biogenic carbon. The most commonly proposed OC are natural ores and residues, but complete combustion has not yet been achieved. In this work, the direct utilization of CLC exhaust gas for methane synthesis as an alternative route was investigated, where the gas components CO, CH4 and H2 are not disadvantageous but benefit the reactions in a methanation step. The whole process chain, the coupling of an 80 kWth pilot plant with gas cleaning and a 10 kW fluidized bed methanation unit were for this purpose established. As OC, ilmenite enhanced with limestone was used, combusting bark pellets in autothermal operation at over 1000 °C reaching high combustion efficiencies of up to 91.7%. The fuel reactor exhaust gas was mixed with hydrogen in the methanation reactor at 360 °C and converted with a methane yield of up to 97.3%. The study showed especially high carbon utilization efficiencies of 97% compared to competitor technologies. Based on the experimental results, a scale-up concept study showed the high potential of the combination of the technologies concerning the total efficiency and the adaptability to grid injection. Graphical Abstract

Solar power appears to be one of the most promising resources to meet the medium and long term renewable energy targets. The integration of large amounts of photovoltaic (PV) generation into distribution networks faces some limitations due to the network constraints. The PV community became well aware of these limitations in the last years. While first solutions have been pointed out mainly for large installations connected to the medium voltage network, the specificities of low voltage networks are still not fully understood. This paper aims at explaining the challenges associated to the planning and operation of low voltage network with high PV penetration. The actual impact of PV infeed is quantified on the basis of real and accurate network, load and generation data. Results from unsymmetrical load-flow computations are presented and the implementation of reactive power-based voltage control is shortly discussed. 26th European Photovoltaic Solar Energy Conference and Exhibition; 4469-4478

Photovoltaic (PV) technology allows large-scale investments in a renewable power-generating system at a competitive levelized cost of electricity (LCOE) and with a low environmental impact. Large-scale PV installations operate in a highly competitive market environment where even small performance losses have a high impact on profit margins. Therefore, operation at maximum performance is the key for long-term profitability. This can be achieved by advanced performance monitoring and instant or gradual failure detection methodologies. We present in this paper a combined approach on model-based fault detection by means of physical and statistical models and failure diagnosis based on physics of failure. Both approaches contribute to optimized PV plant operation and maintenance based on typically available supervisory control and data acquisition (SCADA) data. The failure detection and diagnosis capabilities were demonstrated in a case study based on six years of SCADA data from a PV plant in Slovenia. In this case study, underperforming values of the inverters of the PV plant were reliably detected and possible root causes were identified. Our work has led us to conclude that the combined approach can contribute to an efficient and long-term operation of photovoltaic power plants with a maximum energy yield and can be applied to the monitoring of photovoltaic plants.

Adsorption refrigeration, as a renewable cooling method, has received more attention in the last few years. The interest in this technology comes especially from developing and tropical countries, where the demand for cooling increases every year due to economy and population growth. Based on this scenario, this work aims to develop a numerical model of an adsorption chiller driven with solar energy, which can be used to optimize the cooling system operation of the building where the device is situated and compare it with the current cooling methods in use. The numerical study here presented was created using Matlab/Simulink™, it is based on a lumped parameter model that relies on physical properties and represents a cooling system using a pair of silica gel-water in a two-bed chiller. In this study, the authors proposed a simplified version of the system and the numerical model, which aims to reduce the simulation time and provide faster results. Besides the temperatures in the system, which range from 52 °C to 72 °C in the hot cycle and 12 °C to 23 °C in the chilled water cycle, the results also include the variation of water uptake in the two adsorbent beds. In general, the simulated temperature, cooling and heating power and coefficient of performance (COP) are in fair agreement with the literature data, nevertheless, the final results show that improvements still have to be performed.

This paper is devoted to study the electrochemical behavior of Pt catalyst in a polymer electrolyte fuel cell at various operating conditions and at different electric potential difference (also known as voltage) cycling applied in accelerated stress tests. The degradation of platinum is considered with respect to the Pt ion dissolution and the Pt oxide coverage of catalyst described by a one-dimensional model. In the model, degradation rate increases with temperature and decreasing particle diameter of Pt nano-particles. The theoretical study of the underlying diffusion system with the nonlinear reactions is presented by analytical methods and gives explicit solutions through a first integral of the ODE system. Numerical tests are obtained using a second order implicit-explicit scheme. The computer simulation shows that the lifetime of the catalyst depends on the voltage profile and the upper potential level. By this Pt mass loss is more significant at the membrane surface than at the gas diffusion layer.

Ziel der Diplomarbeit ist es, sich kritisch mit dem Thema Sanierung im Bestand und der Revitalisierung der Plattenbausiedlungen in den neuen Europ��ischen L��ndern, auseinanderzusetzen. Dies ist wichtig, weil das Sanierungsproblem nicht nur im Mittelosteurop��ischen Raum (MOE) gegenw��rtig ist, sondern auch in vielen westeurop��ischen Industriel��ndern ein zentrales Thema geworden ist. Im Zuge der Ausarbeitung wird in Bezug auf Deutschland ein geschichtlicher R��ckblick gemacht warum diese Siedlungen entstanden, wie viele Plattenbauten im MOE Raum zu finden sind und welche Geb��udetypologien in Deutschland am meisten zur Anwendung kamen. Diese Arbeit gibt einen ��berblick ��ber den Stand der Wissenschaft, welche Sanierungskonzepte bereits existieren, inwieweit sie praktisch umgesetzt sind und welche Verbesserungsm��glichkeiten bestehen. Untersucht wird, ob es neue innovativere L��sungsans��tze f��r die Sanierung im Bestand gibt und wie diese bereits umgesetzt sind oder aussehen k��nnten. Untersucht wird hierzu ein g��ngiger Geb��udetypus aus Deutschland - jener, der am h��ufigsten zur Anwendung kam. Es handelt sich hier um ein reines Gedankenexperiment wie man mit innovativen Systemen schaffen k��nnte, den Energieverbrauch wesentlich zu reduzieren. Bedenkt man die Gesamtfl��che der noch zu sanierenden Geb��ude, findet man auch aus marktpolitischer Sicht ein enormes Entwicklungspotential, da die Erhaltung der Bausubstanz notwendig ist und ein Abriss unm��glich. Es soll mit dieser Diplomarbeit gezeigt werden, dass es sinnvoll ist sich auch an der Fakult��t f��r Architektur mit der Forschung zu besch��ftigen, um neue und sinnvolle Methoden zur Geb��udesanierung zu entwickeln. Es wird bereits an der TU Wien mit dem Modul Experimenteller Hochbau ein Schritt in diese Richtung erm��glicht, den es gilt weiter auszubauen! Aim of the thesis is to deal critically with the issue of renovation and revitalization of prefabricated housing estates in the new European countries. This is important because this issue is present not only in the Middle East European Space (MEO), but also has become a key issue in many Western European industrial countries. Initially a historical review is made referring to Germany why these settlements have been built, how many panel buildings can be found in the CEE region and the building typologies which are the most applied in Germany. This work gives an overview of the state of scientific knowledge, which remedial concepts already exist, how they are implemented in practice and what are the opportunities for improvement. It will be investigated whether there are new innovative solutions for the renovation of existing panel buildings and how these have already been implemented or how they could look like. A common type of building in Germany - the one which most often was used - is examined as an example. We are discussing a pure thought experiment how one might manage to reduce the energy consumption significantly with the help of innovative systems. Considering the total area of the yet to be rehabilitated buildings this is quite a market perspective and an enormous development potential, the preservation of the panel buildings is the better alternative to demolition. It will be shown in this thesis that it is useful even at the Faculty of Architecture to do some research for finding new and useful methods to develop building renovation. The combination of the classic art of construction with experimental science, is able to create new technologies, appliances and additives which is already done in the module Experimental construction at the Vienna University of Technology.

This paper presents the goals and components of a quantitative energy balance assessment framework to define PEDs flexibly in three important contexts: the context of the district's density and RES potential, the context of a district's location, induced mobility and the context of the dis-trict's future environment and its decarbonized energy demand or supply. It starts by introducing the practical goals of this definition approach: achievable, yet sufficiently ambitious to be inline with Paris 2050 for most urban and rural Austrian district typologies. It goes on to identify the main design parts of the definition: system boundaries, balancing weights and balance targets and argue how they can be linked to the definition goals in detail. In particular we specify three levels of system boundaries and argue their individual necessity: operation, including everyday mobili-ty, including embodied energy and emissions. It argues that all three pillars of PEDs, energy effi-ciency, onsite renewables and energy flexibility can be assessed with the single metric of a prima-ry energy balance when using carefully designed, time-dependent conversion factors. Finally, it is discussed how balance targets can be interpreted as information and requirements from the sur-rounding energy system, which we identify as a "context factor". Three examples of such context factors, each corresponding to the balance target of one of the previously defined system bounda-ries operation, mobility and embodied emissions are presented: Density (as a context of opera-tion), sectoral energy balances and location (as a context for mobility) and an outlook of a person-al emission budgets (as a context for embodied emissions). Finally, the proposed definition framework is applied to seven distinct district typologies in Austria and discussed in terms of its design goals.

Abstract This study utilizes a panel data set from 14 European countries over the period 1990–2004 to estimate a dynamic model specification for gasoline demand. Previous studies estimating gasoline consumption per total passenger cars ignore the recent increase in the number of diesel cars in most European countries leading to biased elasticity estimates. We apply several common dynamic panel estimators to our small sample. Results show that specifications neglecting the share of diesel cars overestimate short-run income, price and car ownership elasticities. It appears that the results of standard pooled estimators are more reliable than common IV/GMM estimators applied to our small data set.