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Abstract Solar energy, as main energy supply that sustains life on Earth, is also an unavoidable component of the complex strategy in achieving a clean and fair energy transition and goals for sustainable development by 2030. The present work studies the potential of installing Photovoltaic Distributed Generation at Universidad Politecnica de Madrid – Ciudad Universitaria campus. To this end, the study focuses on the electricity generation, carbon reduction and economic feasibility of solar photovoltaic systems installation using and comparing two different approaches based on data input with different time resolution, simulation software and level of details. Results show that the optimal photovoltaic power that maximizes emissions savings also ensures the best economic return, and in addition coincides with the maximum solar potential of the Campus, which is about 3.3 MW. At campus level, approximately 77% of the photovoltaic electricity production would be consumed locally, which would suppose a coverage of about 40% of the total electricity consumption. Emissions savings could reach 30% and an in-depth economic analysis indicates that the project is highly profitable. These results and methodology could be used to assess the feasibility of photovoltaic systems at other universities and help entities study the solar potential of their buildings.

Die Doktorarbeit studiert unendliche Ensembles gewöhnlicher Differentialgleichungen mit gemeinsamen Monotonieeigenschaften, wie sie in der Nachhaltigkeitsforschung auftreten. Es werden neue Verfahren zur Behandlung von solchen Ensembles entwickelt und zur modellgestützen analyse verschiedener Problemen des nachhaltigen Umgangs mit natürlichen Ressourcen erprobt. Qualitative Differentialgleichungen (QDEs) und Differentialinklusionen werden in den neu formalisierten Rahmen der Modellensembles eingebettet. Darunter versteht man eine Menge von Funktionen auf einem Zustandsraum, die Anfangswertprobleme definieren. Für eine QDE schreibt man eine Matrix von Vorzeichen vor und erhält als Modellensemble die Menge aller Funktionen, bei denen die Einträge der Jacobimatrix dem Vorzeichen nach der vorgeschriebenen Matrix entsprechen. Angewendet werden die neuen Methoden auf die Armuts- Degradations-Spirale in Entwicklungsländern, Fischereimanagement (insbesondere industrialisierte Hochseefischerei und partizipatorische Managementansätze), sowie Wassermanagement zur Vermeidung von Eutrophierung. Derartige Anwendung stellen besondere anforderungen an die Modellierung, insbesondere Unsicherheiten im Wissen und der Bedarf nach verallgemeinerbaren Resultaten. Es wird gezeigt, dass Modellensembles hierfür geeignet sind. Basierend auf der neu eingeführten graphentheoretischen Formulierung von QDEs werden vier innovative Verfahren zum Umgang mit großen QDEs entwickelt. Hierbei wird die Viabilitätstheorie begrifflich wie methodisch für Abstraktions- und Restriktionsverfahren eingesetzt. (i) Die graphentheoretische Fassung viabler Mengen führt zur No-return Abstraktion, die einen engen Bezug zu starken Zusammenhangskomponenten aufweist. Damit lassen sich Zustandsgraphen aggregiert darstellen und bezüglich Nachhaltigkeitsfragen evaluieren. (ii) Die Restriktion der zulässigen Lösungen erlaubt es, Kanten von untergeordneter Bedeutung aus dem Zustandsgraphen zu eliminieren. (iii) Die Restriktion auf Systeme, bei denen die Einträge der Jacobimatrix eine vorgegebene partielle Ordnung aufweisen, ermöglicht die Elimination weiterer Pfade. (iv) Zuletzt werden Intervallschranken für die Einträge der Jacobimatrix berücksichtigt. Die Anwendungen zeigen, dass mit diesen Methoden neue und robuste Eigenschaften auch sehr allgemeiner Modelle zum Management natürlicher Ressourcen gewonnen werden können. Ihre Stärken für den Entwurf alternativen Politikoptionen werden deutlich. The thesis studies infinite ensembles of ordinary differential equations with common monotonicity properties as they typically appear in sustainability research. New methods to process such ensembles are developed and applied for the model-based analysis of different sustainable resource use problems. Qualitative differential equations (QDEs) and differential inclusions are embedded into the new formal framework of model ensembles. A model ensemble is defined as a set of functions on a state space which specify initial value problems. For a QDE a matrix of signs is prescribed, and the model ensemble is the set of all functions where the coefficients of the Jacobian have the same signs as the coefficients of the prescribed matrix. The new methods are applied to the impoverishment-degradation spiral in developing countries, to fisheries management (in particular industrialised deep-sea fishery and participatory management), and to water management to avoid eutrophication. These applications pose special challenges for modelling, in particular knowledge uncertainties and the demand for generalisable results. It is shown that model ensembles are adequate for these challenges. Based on a new graph theoretical formulation of QDEs, four innovative techniques for the analysis of large QDEs are developed. For that, viability theory is used conceptually and methodologically for abstraction and restriction techniques. (i) The graph theoretical formulation of viable sets leads to the no-return abstraction, which is closely related to strongly connected components. This makes it possible to display large state-transition graphs in an aggregated way and to evaluate them with respect to sustainability criteria. (ii) By restricting the set of admissible solutions, edges with limited relevance can be eliminated from the state-transition graph. (iii) By restricting the model ensemble to systems where the coefficients of the Jacobian have a prescribed partial order, further paths can be eliminated. (iv) Finally, interval bounds for the coefficients of the Jacobian are considered. The applications show that the new methods strongly improve the identification of new and robust properties of very general models about the management of natural resources. Their advantages for the design of alternative policy options become clear. Front Matter: Title page, Preface, Contents, Notations and Concepts 1\. Introduction 2\. Qualitative Reasoning with Model Ensembles 2.1 Model Ensembles and Set-Valued Solution Operators 2.2 Qualitative Differential Equations 2.3 Differential Inclusions 2.4 Viability Theory 3\. Abstraction and Restriction Techniques 3.1 No-Return Abstraction 3.2 Marginal Edges 3.3 Ordinal Assumptions 3.4 Quantitative Bounds 4\. Management of Natural Resources 4.1 Land-Use Changes in Developing Countries 4.2 Capital Accumulation in Unregulated Fisheries 4.3 Participatory Fishery Management 4.4 Lake Management 5\. Conclusions Annex: Model Code Back Matter: Bibliography, Lebenslauf, Zusammenfassung

AbstractOwing to the increasing challenges of climate change and limited resources, a bundle of requirements for bioenergy are given, such as securing the energy supply, linking with the material use of biomass, or producing negative emissions. Smart bioenergy generation and utilization can fulfil those requirements by the sustainable, efficient, and flexible provision of renewable energy. This study aims to thoroughly define and structure all contributions bioenergy can make to the energy system, in the form of a comprehensive multilevel goal and indicator system. The built system includes several levels of subgoals associated with biomass, with technology, and its integration. The goal system was verified by research project leaders and further experts and can be applied to any bioenergy concept worldwide.

Abstract The paper investigates the technical feasibility of an air gasification process of a Solid Recovered Fuel (SRF) obtained from municipal solid waste. A pilot scale bubbling fluidized bed gasifier, having a feedstock capacity of about 70 kg/h and a maximum thermal output of about 400 kW, provided the experimental data: the complete composition of the syngas (including the tar, particulate and acid/basic gas contents), the chemical and physical characterization of the bed material and that of entrained fines collected at the cyclone. The experimental runs were carried out by reaching a condition of thermal and chemical steady state under values of equivalence ratio ranging from 0.25 to 0.33. The results indicate that the selected SRF can be conveniently gasified, yielding a syngas of valuable quality for energy applications. The rather high content of tar in the syngas indicates that the more appropriate plant configuration should be that of a “thermal gasifier”, with the direct combustion of the syngas in a burner ad hoc designed, coupled with an adequate energy-conversion device.

Lacking recyclability of multilayer packaging can be overcome by using a thermoreversible crosslinking adhesive consisting of maleimide- and furan-functionalized polyurethane-(PU-)prepolymers, reacting in a Diels–Alder-reaction. Here, the furan-functionalized PU-prepolymer carries furan-side-chains to avoid the usage of an additional crosslinking agent. Thus, N‑(2‑hydroxyethyl)maleimide and furfurylamine are the only two chemicals contained in the adhesive that are not listed in the appendix of EU Regulation 10/2011. Using migration modelling, it could be shown that, at 23 °C, both chemicals have lag-times of only a few minutes if 45 µm PE is used as a barrier. However, if the residual content is below 30 mg/kg, the legally specified maximum amount of 0.01 mg/kg food is not reached. After determining the diffusion coefficients and the activation energy of diffusion through ethylene-vinyl alcohol copolymer (EVOH), it could be determined that the lag-time of the migrants can be extended to at least 9 years by the use of 3 µm EVOH. From a food law point of view, the use of the described adhesive is possible if the above‑mentioned measures are complied.

Recently, the European Commission identified the goal to achieve a double transition—ecological and digital—as one of the greatest challenges on the areas of the planet across various sectors of the society [...]

This paper presents an assessment and evaluation of the costs of operation and maintenance (O&M) in a real PV rural electrification (PVRE) programme, with the aim of characterizing its costs structure. Based on the extracted data of the 5-years operational costs of a private operator, the programme has been analyzed to take out the most relevant costs involved in the O&M phase as well as the comparative appraisal between the 3 main activities: installation, O&M and management. Through this study we try to answer to the new challenge of decentralized rural electrification based on larger programmes (with tens of thousands of SHSs) and longer maintenance and operation periods (at least 10 years).

The campus of the Karlsruhe Institute of Technology (KIT) contains several waste heat streams. In an effort to reduce greenhouse gas emissions by optimizing thermal power consumption on the campus, researchers at the KIT are proposing a ‘DeepStor’ project, which will sequester waste heat from these streams in an underground reservoir during the summer months, when the heat is not required. The stored heat will then be reproduced in the winter, when the campus’s thermal power demand is much higher. This paper contains a preliminary geochemical risk assessment for the operation of this subsurface, seasonal geothermal energy storage system. We used equilibrium thermodynamics to determine the potential phases and extent of mineral scale formation in the plant’s surface infrastructure, and to identify possible precipitation, dissolution, and ion exchange reactions that may lead to formation damage in the reservoir. The reservoir in question is the Meletta Beds of the Upper Rhein Graben’s Froidefontaine Formation. We modeled scale- and formation damage-causing reactions during six months of injecting 140 °C fluid into the reservoir during the summer thermal storage season and six months of injecting 80 °C fluid during the winter thermal consumption season. Overall, we ran the models for 5 years. Anhydrite and calcite are expected mineral scales during the thermal storage season (summer). Quartz is the predicted scale-forming mineral during the thermal consumption period (winter). Within ~20 m of the wellbores, magnesium and iron are leached from biotite; calcium and magnesium are leached from dolomite; and sodium, aluminum, and silica are leached from albite. These reactions lead to a net increase in both porosity and permeability in the wellbore adjacent region. At a distance of ~20–75 m from the wellbores, the leached ions recombine with the reservoir rocks to form a variety of clays, i.e., saponite, minnesotaite, and daphnite. These alteration products lead to a net loss in porosity and permeability in this zone. After each thermal storage and production cycle, the reservoir shows a net retention of heat, suggesting that the operation of the proposed DeepStor project could successfully store heat, if the geochemical risks described in this paper can managed.