• Energy Research
• 7. Clean energy close
• 16. Peace & justice close
• DepositOnce close

The assessment literature on climate change solutions to date has emphasized technologies and options based on cost-effectiveness analysis. However, many solutions to climate change mitigation misalign with such analytical frameworks. Here, we examine demand-side solutions, a crucial class of mitigation options that go beyond technological specification and cost-benefit analysis. To do so, we synthesize demand-side mitigation options in the urban, building, transport, and agricultural sectors. We also highlight the specific nature of demand-side solutions in the context of development. We then discuss key analytical considerations to integrate demand-side options into overarching assessments on mitigation. Such a framework would include infrastructure solutions that interact with endogenous preference formation. Both hard infrastructures, such as the built environment, and soft infrastructures, such as habits and norms, shape behavior and as a consequence offer significant potential for reducing overall energy demand and greenhouse gas emissions. We conclude that systemic infrastructural and behavioral change will likely be a necessary component of a transition to a low-carbon society.

In this paper we introduce a five-fold approach to open science comprised of open data, open-source software (that is, programming and modeling tools, model code, and numerical solvers), as well as open-access dissemination. The advantages of open energy models are being discussed. A fully open-source bottom-up electricity sector model with high spatial resolution using the Julia programming environment is then being developed, describing source code and a data set for Germany. This large-scale model of the electricity market includes both generation dispatch from thermal and renewable sources in the spot market as well as the physical transmission network, minimizing total system costs in a linear approach. It calculates the economic dispatch on an hourly basis for a full year, taking into account demand, infeed from renewables, storage, and exchanges with neighboring countries. Following the open approach, the model code and used data set are fully publicly accessible and we use open-source solvers like ECOS and CLP. The model is then being benchmarked regarding runtime of building and solving against a representation in GAMS as a commercial algebraic modeling language and against Gurobi, CPLEX, and Mosek as commercial solvers. With this paper we demonstrate in a proof-of-concept the power and abilities, as well as the beauty of open-source modeling systems. This openness has the potential to increase the transparency of policy advice and to empower stakeholders with fewer financial possibilities.

This paper presents an energy efficient power coupling steering system for dual motors drive high speed tracked vehicle. The system consists of a new type of center steering motor, two electromagnetic (EM) clutches, two planetary gear couplers, and two propulsion motors. The motor torque and power required by dynamic steering with different steering radiuses for dual motors drive high speed tracked vehicle were investigated. A motor-speed-based control strategy of dynamic steering is designed to achieve vehicle lateral stability enhancement. The model of the proposed control strategy in RecuDyn and Matlab/Simulink is given. The simulation results of dynamic steering with 0.5B and 2B radius show that understeer in small radius steering can be significantly improved.

Gas foil bearings are a smart green technology and suitable for the next generation of small turbo machinery e.g. turbochargers, micro gas turbines, range extenders and compressors of fuel cells. A combination of low power loss, high speed operation and the omission of an oil system are the major advantages. To enable access to this technology, it is essential to evaluate critical speeds and onset speeds of subharmonic vibration of the rotor system in the first design stage. Hence, robust and valid models are necessary, which correctly describe the fluid structure interaction between the lubrication film and the elastic bearing structure. In the past three decades several experimental and numerical investigations of bearing parameters have been published. But the number of sophisticated models is small and there is still a lack of validation towards experimental works. To make it easy for designers dealing with this issue, the bearing parameters are often linearised about certain operating points. In this paper a method for calculating linearised bearing parameters (stiffness and damping) of gas foil bearing is presented. Experimental data are used for validation of the model. The linearised stiffness and damping values are calculated using a perturbation method. The pressure field is coupled with a two-dimensional plate model, while the non-linear bump structure is simplified by a link-spring model. It includes Coulomb friction effects inside the elastic corrugated structure and captures the interaction between the single bumps. For solving the separated perturbed Reynolds equation a static stiffness is used for the 0. order equation (stationary case) and a dynamic stiffness is applied for 1. order equation (dynamic case). Therefore, an additional dynamic structural model is applied to calculate the dynamic stiffness. The results depend on the load level and friction state of each bump. Different case studies including the impact of clearance, frictional contacts and the comparison of a linear and non-linear structure are carried out for infinitesimal perturbations. The results show, that the linear structure underestimates main and cross-coupling effects. The impact of the clearance is notable, while the impact of the overall frictional contacts is small due to relatively small loadings. The infinitely small perturbation model is adapted to the experimental setup by using a superposition of two resulting bearing parameters identifications of two total loadings including shaker forces. Due to this adaptation a good correlation with the experimental results of the bearing parameters is achieved.

Wasser-Gesteins-Wechselwirkungen umfassen Sorptions-, Lösungs-, Fällungs- und Redox-Reaktionen zwischen Gesteinsmatrix und Wasser. In thermischen Aquiferspeichern (ATES: Aquifer Thermal Energy Storage) können bestimmte Wasser-Gesteins-Wechselwirkungen unerwünschte Folgen haben, etwa das Zusetzen von Gesteinsporen durch Ausfällungen oder die Freisetzung von Schadstoffen. Sie müssen daher als geochemische Risiken betrachtet werden. Ihre Prognose und Vermeidung erfordert standortspezifische Informationen über Wasser-Gesteins-Wechselwirkungen bei bestimmten Betriebsbedingungen. Die vorliegende Arbeit untersucht die Reaktivität von zwei pyritführenden siliziklastischen Gesteinen aus den unterjurassischen Stufen des Hettangium und des unteren Sinemurium. Sie bilden den Wärmespeicher des ATES-Systems der deutschen Parlamentsbauten in Berlin, gelegen im südöstlichen Teil des Nordostdeutschen Beckens. Die Arbeit stellt ein Verfahren dar, das (a) Mineralogie und Sorptionsreaktionen an der Gesteinsoberfläche beschreibt, (b) die maximal aus einem Gestein freisetzbare Menge an potentiell kritischen Elementen (Schadstoffe/Mineralbildner) quantifiziert, (c) ihre Phasenbindung und Freisetzungsmechanismen bestimmt und (d) die wichtigsten Kontrollparameter und Prozesswechselwirkungen bei der Wärmespeicherung identifiziert. Die Mineralogie wurde mit Hilfe von Röntgendiffraktometrie, Röntgenfluoreszenzanalyse und Rasterelektronenmikroskopie bestimmt. Potentiell kritische mobile Elemente und leichtlösliche kristalline und amorphe Festphasen, z.B. Hydroxide und Sulfide, wurden mit Hilfe einer speziell entwickelten sequentiellen Extraktion quantifiziert. Diese Methode ermöglicht die Unterscheidung mobiler Elemente anhand ihrer Assoziation mit bestimmten Gesteinsfraktionen mithilfe geeigneter Lösungsmittel. Diese Fraktionen sind (1) austauschbar, (2) mit säurelöslichen Phasen assoziiert (Karbonate), (3) mit reduzierbaren Phasen assoziiert (Oxide/Hydroxide), und (4) mit oxidierbaren Phasen assoziiert (Organik/Sulfide). Die Wärmespeicherung, definiert durch Temperaturen von bis zu 90 °C und möglichen Sauerstoffeintrag in das Grundwasser, wurde durch stationäre Laugungsversuche mit vereinfachtem synthetischen Grundwasser (0.42 M NaCl-Lösung) untersucht, indem die Kontrollparameter Temperatur (25, 50, 70, 90 °C), gelöster Sauerstoff (oxisch/anoxisch) und Extraktionsdauer (1, 2, 4, 7 Tage) variiert wurden. Der Einfluss verschiedener Kontrollparameter und Prozessinteraktionen wurde mithilfe numerischer Simulationen und statistischer Methoden bestimmt. Versuchsdaten wurden hierbei zur Parametrisierung und Validierung herangezogen. Die folgenden Resultate und Implikationen für den Speicherbetrieb in dem ursprünglich sauerstoffarmen Grundwasserleiter wurden für die potentiell kritischen mobilen Elemente (Schadstoffe/Mineralbildner) Al, As, Ba, Ca, Cu, Fe, Mn, Ni, Pb und Si bestimmt: Die insgesamt, d.h. aufsummiert über alle Schritte der sequentiellen Extraktion, aus dem Aquifersandstein extrahierbaren Mengen der einzelnen Elemente sind sehr niedrig (<0.1 mg/g), und liegen für den Siltstein des hangenden Geringleiters deutlich höher (bis zu ca. 4 mg/g für Ca). Das Eisensystem ist der Hauptrisikofaktor. Bei oxischen Bedingungen wird Pyrit (FeS2) gelöst. Liegt kein geeigneter Puffer in Lösung vor, sinkt der pH-Wert, was die Mobilisierung weiterer Elemente unterstützt. Bei anoxischen Bedingungen wird die Elementmobilisierung vorwiegend durch die Lösung von Eisenhydroxiden kontrolliert. Freigesetztes dreiwertiges Eisen neigt zu rascher Wiederausfällung, und stellt im untersuchten System den wichtigsten Mineralbildner dar. Calcium ist vorwiegend adsorbiert, und kann durch pH-Wert-Absenkung freigesetzt werden. Falls die Ca-Konzentration durch Mineralausfällungen sinkt, kann das thermodynamische Gleichgewicht zwischen Gestein und Grundwasser durch Desorption rasch wiederhergestellt werden. Kleine Mengen Aluminium und Silizium konnten in Laugungsversuchen über bis zu sieben Tage rasch aus amorphen (Hydr)oxiden mobilisiert werden. Die kinetisch langsamere Lösung kristalliner Silikatminerale spielt bei langfristigen Lösungsprozessen allerdings die wichtigere Rolle. Arsen kann aus dem Aquifersandstein kaum freigesetzt werden. Im Labor wurde eine Mobilisierung nur im Reduktionsschritt der sequentiellen Extraktion beobachtet (ca. 0.02 µg/g), sodass keine kritische Gefährdung befürchtet werden muss. Barium, Kupfer, Nickel und Blei zeigen keine eindeutige Fraktionierung. Sie liegen vermutlich vorwiegend als feste Lösung oder Kopräzipitat vor, und ihre Mobilität scheint hauptsächlich durch Lösung und Fällung von Eisenphasen bestimmt zu werden. Kupfer wurde in gediegener Form nachgewiesen. Für den untersuchten Wärmespeicher an den deutschen Parlamentsbauten wurden keine kritischen Risikofaktoren gefunden, die zu Grundwasserkontamination oder Porenraumverkleinerung in einem Umfang führen würden, der den Speicherbetrieb verhindert. Es muss allerdings eine durchgängige Stickstoffbeaufschlagung des Systems sichergestellt werden, um Sauerstoffintrusion mit folgender Pyritlösung, Grundwasserversauerung bei Überschreiten der Pufferkapazität und Freisetzung kritischer Elemente zu verhindern. Water-rock interactions are sorption-, dissolution-, precipitation-, and redox reactions at the interface between rock matrix and water. In aquifer thermal energy storage (ATES) systems, certain water-rock interactions can have undesired consequences, such as clogging of aquifer pores or contaminant release, and are therefore geochemical risks. Their prediction and prevention requires site-specific knowledge about water-rock interactions at specific operational conditions. This study investigates the reactivity of two pyrite-bearing siliciclastic rocks from the Hettangian and Lower Sinemurian stages of the Lower Jurassic. They are associated with the heat storage aquifer of the ATES system at the German parliament buildings in the city of Berlin, which is located in the south-eastern part of the Northeast German Basin. The study presents a workflow to (a) describe mineralogy and sorption reactions at the rock surface, (b) quantify the maximum of potentially critical (mineral-forming/contaminant) elements that can be released from the rocks, (c) determine their phase association and release mechanisms, and (d) identify the most important control parameters and process interactions during heat storage. The bulk mineralogy was identified by X-ray diffraction, X-ray fluorescence and scanning electron microscopy. Potentially critical mobile elements and easily soluble crystalline and amorphous solid phases, such as hydroxides and sulfides, were quantified with a specifically developed sequential extraction. This method allows the partition of mobile elements by association with specific rock fractions with the help of appropriate solvents. These fractions are (1) exchangeable (2) associated with acid-soluble phases (carbonates), (3) associated with reducible phases (oxides/hydroxides), and (4) associated with oxidizable phases (organic matter/sulfides). Heat storage, defined by temperatures of up to 90 °C and potential intrusion of oxygen into the aquifer, was investigated by steady-state leaching experiments with simplified synthetic groundwater (0.42 M NaCl solution) by varying the control parameters temperature (25, 50, 70, 90 °C), solute oxygen (oxic/anoxic) and leaching time (1, 2, 4, 7 days). The influence of different control parameters and process interactions was analyzed by numerical simulations and statistics, using experimental data for parameterization and validation. The following results and implications for ATES operation in the originally oxygen-depleted aquifer were found for the potentially critical (contaminant/mineral-forming) mobile elements Al, As, Ba, Ca, Cu, Fe, Mn, Ni, Pb, and Si: The total leachable quantity of each element, i.e. the leached sum over all sequential extraction steps, is very small in the aquifer sandstone (<0.1 mg/g), and significantly higher in the siltstone of the topset aquitard (up to ca. 4 mg/g for Ca). The iron system is the main risk factor. At oxic conditions, pyrite (FeS2) dissolves. If no suitable buffers are present, the solution is acidified, which facilitates the mobilization of several other elements. At anoxic conditions, the dissolution of iron hydroxides is the process mainly controlling element mobilization. Ferric iron re-precipitates readily, and is the main mineral-forming species in the investigated system. Calcium is predominantly adsorbed, and can be mobilized by pH reduction. In case the solute concentration decreases due to mineral precipitation, Ca can be desorbed quickly to regain thermodynamic equilibrium between rock matrix and groundwater. Small amounts of aluminum and silicon can be released rapidly from amorphous (hydr)oxides, which were their main source during leaching experiments of up to seven days. Kinetically slow dissolution of crystalline silicates prevails during longer leaching periods. Arsenic is nearly immobile in the aquifer sandstone. During the experiments, it was released only in the reduction step of the sequential extraction (ca. 0.02 µg/g), and represents no critical risk. Barium, copper, nickel, and lead have no single phase association. They are probably mainly present as solid solutions or co-precipitates, and their mobility seems to be primarily controlled by iron phase dissolution/precipitation. Copper was also found in elementary form. For the investigated heat storage at the German parliament buildings, these findings indicate no critical risk factors, which could lead to groundwater contamination or porosity reduction in dimensions that would prohibit ATES operation. However, constant nitrogen pressurization of the system is imperative to prevent oxygen intrusion, which could eventually lead to pyrite dissolution, groundwater acidification once its buffering capacity is exceeded, and critical element mobilization.

The purpose of this research is to evaluate a transcritical heat-driven compression refrigeration machine with CO2 as the working fluid from thermodynamic and economic viewpoints. Particular attention was paid to air-conditioning applications under hot climatic conditions. The system was simulated by Aspen HYSYS® (AspenTech, Bedford, MA, USA) and optimized by automation based on a genetic algorithm for achieving the highest exergetic efficiency. In the case of producing only refrigeration, the scenario with the ambient temperature of 35 °C and the evaporation temperature of 5 °C showed the best performance with 4.7% exergetic efficiency, while the exergetic efficiency can be improved to 22% by operating the system at the ambient temperature of 45 °C and the evaporation temperature of 5 °C if the available heating capacity within the gas cooler is utilized (cogeneration operation conditions). Besides, an economic analysis based on the total revenue requirement method was given in detail.

The slow pyrolysis behaviour of thermally thick wood particles is investigated at 5, 10 and 20 °C/min, combining an advanced single-particle experimental approach with a detailed numerical model. Infrared laser absorption spectroscopy (IRLAS) and laser-induced fluorescence spectroscopy (LIF) are used to characterize on-line and in-situ the evolution of the following volatile products in the close vicinity of the pyrolysing particle: CO2, CO, CH4, H2O, CH2O and fluorescence-emitting species with excitation wavelengths of 266 and 355 nm, such as polycyclic aromatic hydrocarbons (PAH). The numerical particle model is coupled with a detailed pyrolysis kinetic scheme, being able to predict with good accuracy mass loss, temperature evolution and online release of species such as H2O and CO. Model predictions are in some cases even better than for the medium heating rate conditions for which the model was initially tested, showing its wide applicability. Furthermore, the model can be improved including PAH release, for which experimental data is presented, and the delayed release of CH4, which is not correctly described by the model at low heating rates.