In the current global climate of declining fossil fuel reserves and due to the impact of industry on the natural environment, industrial sustainability is becoming ever more important. However, sustainability is quite a vague concept for many, and there are a range of interpretations of the word. If the resource efficiency of a factory is taken as a measure of its sustainability, then the concept becomes better defined and quantifiable. In order to analyse the resource efficiency of a factory and suggest improvements, all flows through the manufacturing system need to be modelled. However the factory is a complex environment, there is a wide variation in the quality levels of energy as well as the composition of material flows in the system. The research presented in this thesis shows how the thermodynamics-based concept of ‘exergy’ can be used to quantify the resource efficiency of a factory. The factory is considered an ‘integrated system’, meaning it is composed of the building and the production processes, both interacting with each other. This is supported by three case studies in different industries that demonstrate the practical application of the approach. A review of literature identified that it was appropriate to develop a novel approach that combined exergy analysis with the integrated view of the factory. Such an approach would allow a ‘holistic’ assessment of resource efficiency for different technology options possibly employable. The development of the approach and its illustration through practical case studies is the main contribution of the work presented. Three case studies, when viewed together, illustrate all aspects of the novel exergy based resource accounting approach. The first case study is that of an engine production line, in which the resource efficiency of this part of the factory is analysed for different energy system options relating to heating ventilation and air conditioning. Firstly, the baseline is compared with the use of a solar photovoltaic array to generate electricity, and then a heat recovery unit is considered. Finally, both of these options were used together, and here it is found that the non-renewable exergy supply and exergy destruction are reduced by 51.6% and 49.2% respectively. The second case study is that of a jaggery (a sugar substitute) production line. The exergy efficiency of the process is calculated based on varying the operating temperature of the jaggery furnace. The case study describes the modelling of al flows through the jaggery process in terms of exergy. Since this is the first example of an exergy analysis of a jaggery process, it can be considered a minor contribution of the work. An imaginary secondary process that could utilize the waste heat from the jaggery process is considered in order to illustrate the application of the approach to industrial symbiosis. The non-renewable exergy supply and exergy destruction are determined for the baseline and the alternative option. The goal of this case study is not to present a thermally optimized design; rather it illustrates how the exergy concept can be used to assess the impact of changes to individual process operations on the overall efficiency in industrial symbiosis. When considering natural resource consumption in manufacturing, accounting for clean water consumption is increasingly important. Therefore, a holistic methodology for resource accounting in factories must be able to account for water efficiency as well. The third case study is that of a food production facility where the water supply and effluent are modelled in terms of exergy. A review of relevant literature shows that previously, the exergy content of only natural water bodies and urban wastewater had been quantified. To the author’s knowledge, this is the first example of applying this methodology of modelling water flows in a manufacturing context. The results show that due to a high amount of organic content in food process effluent, there is significant recoverable exergy in it. Therefore, a hypothetical water treatment process was assumed to estimate the possible savings in exergy consumption. The results show that at least a net 4.1% savings in terms of exergy could be possible if anaerobic digestion water treatment was employed. This result can be significant for the UK since the food sector forms a significant portion of the industry in the country. Towards the end of the thesis, a qualitative study is also presented that aims to evaluate the practical utility of the approach for the industry. A mixed method approach was used to acquire data from experts in the field and analyse their responses. The exergy based resource accounting method developed in this thesis was first presented to them before acquiring the responses. A unanimous view emerged that the developed exergy based factory resource accounting methodology has good potential to benefit industrial sustainability. However, they also agreed that exergy was too complex a concept to be currently widely applied in practice. To this effect, measures that could help overcome this barrier to its practical application were presented which form part of future work.

Master of Science / Department of Mechanical and Nuclear Engineering / Hitesh Bindra / Storing excess thermal energy in a storage media that can later be extracted during peak-load times is one of the better economical options for nuclear power in future. Thermal energy storage integration with light water-cooled and advanced nuclear power plants is analyzed to assess technical feasibility of different storage media options. Various choices are considered in this study; molten salts, synthetic heat transfer fluids, and packed beds of solid rocks or ceramics. In-depth quantitative assessment of these integration possibilities are then analyzed using exergy analysis and energy density models. The exergy efficiency of thermal energy storage systems is quantified based on second law thermodynamics. The packed bed of solid rocks is identified as one of the only options which can be integrated with upcoming small modular reactors. Directly storing thermal energy from saturated steam into packed bed of rocks is a very complex physical process due to phase transformation, two phase flow in irregular geometries and percolating irregular condensate flow. In order to examine the integrated physical aspects of this process, the energy transport during direct steam injection and condensation in the dry cold randomly packed bed of spherical alumina particles was experimentally and theoretically studied. This experimental setup ensures controlled condensation process without introducing significant changes in the thermal state or material characteristics of heat sink. Steam fronts at different flow rates were introduced in a cylindrical packed bed and thermal response of the media was observed. The governing heat transfer modes in the media are completely dependent upon the rate of steam injection into the system. A distinct differentiation between the effects of heat conduction and advection in the bed were observed with slower steam injection rates. A phenomenological semi-analytical model is developed for predicting quantitative thermal behavior of the packed bed and understanding physics. The semi-analytical model results are compared with the experimental data for the validation purposes. The steam condensation process in packed beds is very stable under all circumstances and there is no effect of flow fluctuations on thermal stratification in packed beds. With these experimental and analytical studies, it can be concluded that packed beds have potential for thermal storage applications with steam as heat transfer fluid. The stable stratification and condensation process in packed beds led to design of a novel passive safety heat removal system for advanced boiling water reactors.

En 1987, la commission sur l'environnement et le développement des Nations-Unies définissait le développement soutenable/durable par ‘‘un développement qui répond aux besoins actuels sans compromettre les capacités des générations futures à répondre au leur’’. Cette définition vise à améliorer/maintenir la qualité de vie de l'humanité avec le temps en perspective. Le développement durable met en exergue trois actions : la diminution des besoins, l'utilisation d'énergies propres et renouvelables et le recyclage. Cette thèse vise à proposer des éléments de réponses à trois questions scientifiques : RQ1 : Comment évaluer l'impact environnemental résultant de l'exploitation des ressources minérales, en tenant en compte de leur abondance, de leur composition chimique, de leurs propriétés physiques et des effets de leur extraction?RQ2 : Comment évaluer la performance du recyclage, en prenant en compte les différentes pertes (de quantité et de qualité)?RQ3 : Substituer de l'énergie fossile par de la biomasse s'inscrit-il toujours dans le cadre du développement durable?La méthode émergétique est principalement utilisée pour cette recherche. Elle est complétée par l'exergético-écologie, l'empreinte carbone ou l'analyse exergétique du cycle de vie.L'émergie spécifique initiale (avant exploitation) des 42 minéraux les plus utilisés dans l'industrie est proposée, tout en respectant le principe de hiérarchisation des matériaux formulé par Odum. La performance environnementale du recyclage métallurgique a été étudiée tout en tenant compte des pertes de matière et de qualité. Une transformité moyenne et trois ratios sont proposés, permettant de quantifier une solution qualifiable de ‘‘éco-conception’’. Finalement, l'intérêt d'une substitution d'un combustible fossile par de la biomasse a été analysé à l’aide de deux exemples concrets. / In 1987, the United Nations World Commission on Environment and Development defined sustainable development as ‘‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs’’. The aim is to continuously improve the quality of life for both current and future generation without increasing the use of natural resources beyond the Earth's carrying capacity. The entire life-cycle of natural resources, from their extraction to their final disposal as waste, engenders negative environmental impacts. Waste recycling and the substitutionof excessively polluting resources with alternatives are considered as the key components of sustainable resource management. The flow of the thesis is formalized in the following three research questions:RQ1: Is it possible, and if so how, to assess the environmental impacts resulting from the exploitation of mineral resources, taking into account their abundance, their chemical and physical properties and the effects of their extraction?RQ2: Is it possible, and if so how, to evaluate the environmental performance of recycling, taking into account the chemical, physical and thermodynamic limits of the process?RQ3: To which extent a partial or complete substitution of fossil fuels with biomass is an environmentally friendly solution?The work is essentially based on the emergy approach, but also other environmental assessment tools has been used such as the exergoecology approach, the exergetic life cycle assessment and the carbon footprint. The specific emergy of about 42 main commercially used minerals has been calculated, respecting the material hierarchy developed by Odum. The environmental performance of metallurgical recycling has been studied, taking into account for the material and quality losses during the process. The use of an average transformity is proposed and three sustainability ratios have been defined to assess the benefits and limits of recycling processes. Finally, in order to determine the environmental impact of using biomass as substitute for fossil fuels, two concrete examples has been studied.

Orientador: Caio Glauco Sánchez / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T18:09:54Z (GMT). No. of bitstreams: 1 Bobroff-Maluf_Aristides_D.pdf: 7073975 bytes, checksum: aab700c765075939bd627ac33e00588a (MD5) Previous issue date: 2014 / Resumo: Neste trabalho é desenvolvida uma metodologia para a avaliação termoeconômica da cogeração no setor sucroenergético, com geração na entressafra. São feitos balanços de massa, energia e exergia das plantas, usando o simulador Cycle-Tempo. Em seguida é elaborada uma folha de balanço de energia (FBE) para fornecer a energia elétrica consumida e a exportada pela planta. O fluxo de caixa indica a viabilidade econômica ou não da planta, e o estudo da sensibilidade mostra a variação do custo específico da bioenergia produzida, devido às incertezas. Os biocombustíveis empregados são: bagaço, palha e biogás de vinhaça. O trabalho também simulou cenários para a queima da palha da cana. Elementos como potássio, sódio e cloro encontrados em maior quantidade na palha quando comparada ao bagaço, têm causado problemas de incrustação (depósito), fuligem e corrosão nas caldeiras (baixo ponto de fusão das cinzas). A melhor solução, apresentada neste trabalho, é o tratamento da palha através da trituração, lixiviação e secagem, antes da queima nas caldeiras. Com este tratamento, a palha se torna semelhante ao bagaço, minimizando os efeitos nocivos da queima. Com a diminuição das queimadas nos canaviais, tem-se aumentado a quantidade de palha disponível na indústria. Esse biocombustível é usado para aumentar a exportação da energia elétrica excedente. Como conclusões mais importantes, durante a safra, é a utilização conjunta do bagaço, 50% da palha (triturada, lixiviada e seca) produzida no campo e o biogás produzido pela biodigestão anaeróbica da vinhaça. Na entressafra, utilizando os equipamentos que ficariam ociosos, é produzido energia elétrica para exportação. O melhor biocombustível para este período é o eucalipto. A análise exergética e a otimização exergoeconômica serviram para complementar o trabalho / Abstract: In this work a metodology is developped for the thermoeconomic assessment of the cogeneration in the sugar mills, with generation in the off-season. Mass, energy and exergy balance were elaborated, using the software Cycle-Tempo. After that an energy balance sheet (FBE) was elaborated to establish the exported and consumed electric energy by the plant. The cash flow indicates the economic feasibility or not of the plant, and the sensibility study shows the variation of the specific cost of the produced bioenergy, due to the incertainties. The biofuels used are: bagasse, straw and vinasse biogas. This work also simulated scenarios for the burning of cane-straw. Elements like potassium, sodium and chlorine found in great quantities in the straw when compared to the bagasse, has caused problems of slagging, fouling and corrosion in the boilers (low melting point of the ashes). The best solution, as shown in this work, is the treatment of the cane straw through trituration, leaching and drying, before burning the material in the boilers. With that treatment, the straw becomes similar to the bagasse, minimizing the harmful efects of the burning. With the decreasing of the burnings in the sugar-cane plantations, the quantity of straw available in the industry has grown. This biofuel could be used to increase the exportation of surplus electricity. As more important conclusions, during the season, it is the joint utilization of bagasse, 50% of straw (triturated, leached and dried) produced in the fields and of the biogas produced by the anaerobic biodigestion of the vinasse. During the off-season, using the facilities that would otherwise stay idle, electricity for exportation should be produced. The best biofuel for that period is the eucalyptus. The exergetic analysis and optimization were useful to complete this work / Doutorado / Engenharia Mecanica / Doutor em Engenharia Mecânica

A broad scope analysis of waterjet cutting systems has been developed using thermodynamics, life cycle analysis, and biological system comparison. The typical assessments associated with mechanical design include measures for performance and thermodynamic efficiency. Further analysis has been conducted using exergy, which is not typically incorporated into design practices. Exergy measures the effectiveness of a process with respect to a base state, usually that of the systems surroundings. Comparing Gibbs free energy of biological processes to exergy efficiency has served to illustrate the need for various levels of comparison. Each biological process used in this comparison correlates to a different type of mechanical process and level of complexity. Overall, biological processes display similar properties to mechanical systems in that simpler systems are more energy efficient. In order to determine accurate efficiency and effectiveness values for a mechanical process, in this case waterjet cutting, a set of thermodynamic models was established to account for energy uses. Various output force and velocity models have been developed and are used here for comparison to assess output efficiencies with "no loss" models used as a lossless base. Experimental testing was then conducted using a simple nozzle and a pressure washer with 2 other diameter nozzles. The most energy efficient system used a turbojet nozzle. It was also the most efficient sustained system with energy inputs. However, it had a much lower exergy efficiency compared to the other systems. This implies that it could be significantly improved by more adequately utilizing the energy provided. An effort to assess the green nature of pressurized water systems was done through use of an Economic Input/Output Life Cycle Analysis (EIO-LCA). The EIO-LCA is designed to assess processes for greenhouse gas emissions and total power consumption across the life of a system. Calculations showed that increases in power consumption result in much higher greenhouse gas emissions per unit time than increases in water consumption. Financial cost however showed an opposite trend due to the much greater cost of water with regard to consumption rates in each system. The most "green" system used only a nozzle with no power consumption.

Non-equilibrium thermodynamics, which serves as a framework for formulating evolution equations of macroscopic and mesoscopic systems, is briefly reviewed and further developed in this work. For example, the relation between the General Equation for the Nonequilibrium Reversible- Irreversible Coupling (GENERIC) and (ir)reversibility is elucidated, and Onsager-Casimir reciprocal relations are shown to be an implication of GENERIC. Non-equilibrium thermodynamics is then applied to describe fuel cells and related devices, and theoretical conclusions are compared to experimental data. Moreover, a generalization of standard exergy analysis is developed bringing a new method for revealing a map of useful work losses in electricity producing devices. This method requires a non-equilibrium thermodynamic model, and so the general theory of non- equilibrium thermodynamics and optimization of real power generating devices stand side by side.

Today the selection of drive technology for realizing of moving tasks is made by comparing of investment and energy costs in general. Pneumatic drives are characterized by their low purchase price, but at the same time they show high energy consumption in a comparison with electric drives. This general evaluation leads to the point, that in many cases the optimum drive structure for a certain handling task can’t be found regarding functionality and efficiency. To reach that goal, the dynamic, energy and costs characteristics of the actuator have to be observed and summarized. In this paper the EXonomy analysis is presented as a base for the inter-domain comparison of electric and pneumatic drives. Developed EXonomy approach enables the objective analysis and comparison of electric and pneumatic systems within 3 steps.

<div>Designing configurations for multicomponent distillation, a ubiquitous process in chemical and petrochemical industries, is often challenging. This is because, as the number of components increases, the number of admissible distillation configurations grows rapidly and these configurations vary substantially in their energy needs. Consequently, if a method could identify a few energy-efficient choices from this large set of alternatives, it would be extremely attractive to process designers. Towards this, we develop the first mixed-integer nonlinear programming (MINLP) based solution approach that successfully identifies the most energy-efficient distillation configuration for a given separation. Current sequence design strategies are largely heuristic. The rigorous approach presented here can help reduce the significant energy consumption and consequent greenhouse gas emissions by separation processes. </div><div> </div><div>In addition to the combinatorial complexity, the challenge in solving this problem arises from the nonconvex fractional terms contained in the governing equations. We make several advances to enable solution of these problems.</div><div><br></div><div>(1). We propose a novel search space formulation by embedding convex hulls of various important substructures. We prove that the resulting formulation dominates all the prior formulations in the literature.</div><div><br></div><div>(2). We derive valid cuts to the problem by exploiting the monotonic nature of the governing equations. </div><div><br></div><div>(3). We adapt the classical Reformulation-Linearization Technique (RLT) for fractional terms. Our RLT variant exploits the underlying mathematical structure of the governing equation, and yields a provably tighter convex relaxation.</div><div><br></div><div>(4). We construct the simultaneous hull of multiple nonlinear terms that are constrained over a polytope obtained by intersecting a hypercube with mass balance constraints. This yields a tighter convex relaxation than the conventional approach where the nonlinear terms are convexified individually over a box.</div><div><br></div><div>(5). A key challenge in constructing a valid convex relaxation has been that the denominator of certain fractions in the governing equation can approach arbitrarily close to zero. Using our RLT variant, we construct the first valid relaxation. </div><div><br></div><div>(6). We leverage powerful mixed-integer programming (MIP) solvers by implementing a discretization-based solution procedure with an adaptive partitioning scheme.</div><div><br></div><div>With extensive computational experiments, we demonstrate that the proposed approach outperforms the state-of-the-art in the literature. The formulation can be tailored to other objectives by appending the relevant constraints. Here, we present an extension that identifies the distillation configuration that has the highest thermodynamic efficiency. Finally, we illustrate the practicality of the developed approaches with case studies on crude fractionation and natural gas liquid recovery. </div>

Hydrogen is considered to become a main energy vector in sustainable energy systems to store large amounts of intermittent wind and solar power. In this work, exergy efficiency and cost analyses are conducted to compare pathways of hydrogen generation (PEM, alkaline or solid oxide electrolysis), storage (compression, liquefaction or methanation), transportation (trailer or pipeline) and utilization (PEMFC, SOFC or combined cycle gas turbine). All processes are simulated with respect to their full and part-load efficiencies and resulting costs. Furthermore, load profiles are estimated to simulate a whole year of operation at varying loads. The results show power-to-power exergy efficiencies varying between about 17.5 and 43 %. The main losses occur at utilization and generation. Methanation features both lower efficiency and higher costs than compressed hydrogen pathways. While gas turbines show very high efficiency at full load, their efficiency drops significantly during load-following operation , while fuel cells (especially solid oxide) can maintain their efficiency and exceed the combined cycle gas turbine full-load efficiency. Overall specific costs between 245 €/MWh and 646 €/MWh are resulting from the simulation. Lower costs are commonly reached in chains with higher overall efficiencies. Installation costs are identified as predominant because of the low amount of full-load hours. To decrease the energy storage overall costs of the process chains, the options to use revenue generated by by-products such as oxygen and heat as well as changing the system application scenario are investigated. While the effect of the oxygen sale is negligible, the revenue generated by heat can significantly decrease overall costs. An increase of full-load by accounting for an electrolysis base-load to provide hydrogen for vehicles also shows a significant decreases in costs per stored energy down to 151 €/MWh at 2337 h/a full-load hours. The optimization of the exergy efficiency is performed by analysing physical and heat exergy recovery options such as expansion machines in the gas grid, the use of additional thermodynamic cycles (both Joule and Clausius-Rankine), as well as providing heat for steam electrolysis from compression inter-cooling, methanation or stored heat from a solid oxide fuel cell. The analysis shows that at full-load, process chains using solid oxide electrolysis, compressed hydrogen and a combined cycle gas turbine or a solid oxide fuel cells with a heat exergy recovery cycle can reach exergy efficiencies of 47 % and 45.5 %, respectively. A reversible solid oxide cell systems with metal-hydride heat and hydrogen storage can also reach 46.5 % exergy efficiency. The energy storage costs for these processes can be as low as 35 to 40 €/MWh at full-load. At load-following operation the efficiency of the fuel cell systems is expected to increase.:1 Introduction 22 2 Objective and Structure 24 3 Hydrogen as an Energy Vector 25 3.1 Mobile application focus 25 3.2 Stationary application focus 28 3.3 Studies on energy systems 32 3.4 Conclusion 36 4 Hydrogen Technology Overview 37 4.1 Hydrogen production 37 4.1.1 Electro-chemical hydrogen production 37 4.1.2 Thermo-chemical hydrogen production 42 4.1.3 Biological hydrogen production 46 4.1.4 Other hydrogen production processes 46 4.1.5 Gas cleaning 47 4.2 Hydrogen storage 49 4.2.1 Chemical compounds 49 4.2.2 Metal hydride 50 4.2.3 Physical storage 52 4.3 Hydrogen transport 54 4.3.1 Gas grid 54 4.3.2 Trailer 56 4.4 Hydrogen utilization 56 4.4.1 Thermochemical utilization 56 4.4.2 Electrochemical utilization 59 4.5 Investigated energy conversion processes 69 5 Model Description 72 5.1 Components 72 5.1.1 Electrochemical cells 72 5.1.2 Rectifier and inverter 77 5.1.3 Metal hydride storage 78 5.1.4 Liquid hydrogen storage 78 5.1.5 Chemical reactors 78 5.1.6 Catalytic burner 81 5.1.7 Blower 81 5.1.8 Compressor 82 5.1.9 Turbine 82 5.1.10 Electrical engine and generator 82 5.1.11 Heat exchanger 83 5.1.12 Mixer and splitter 84 5.1.13 Sources and sinks 85 5.2 Combined cycle gas turbine 85 5.3 Electricity grid 85 5.4 The exergy method 85 5.5 Property data 88 5.6 Cost model 88 5.7 Load profiles 90 6 Process Analysis 92 6.1 Production 92 6.1.1 Alkaline electrolysis 92 6.1.2 Proton exchange membrane electrolysis 95 6.1.3 Solid oxide electrolysis 96 6.2 Storage 100 6.2.1 Methanation 100 6.2.2 Compression 101 6.2.3 Liquefaction 101 6.3 Transport 101 6.3.1 Gas grid 101 6.3.2 Trailer 101 6.4 Utilization 102 6.4.1 Combined cycle gas turbine 102 6.4.2 Proton exchange membrane fuel cell 104 6.4.3 Solid oxide fuel cell 109 7 Process Chain Analysis 118 7.1 Exergy Efficiency 118 7.1.1 Exergy analysis for full load operation 120 7.1.2 Exergy analysis for load following operation 124 7.2 Overall Costs 125 7.2.1 Cost analysis for full load operation 125 7.2.2 Cost analysis for load following operation 129 8 Waste exergy recovery overview 135 8.1 Waste heat exergy recovery 136 8.1.1 Solid oxide electrolysis 136 8.1.2 Clausius Rankine Cycles 137 8.1.3 Joule Cycles 138 8.1.4 Combination of Joule and Clausius Rankine cycles 139 8.2 Physical exergy recovery 140 8.3 Cryo-exergy recovery 140 9 Process Optimization 141 9.1 Physical exergy recovery 141 9.2 Waste heat exergy recovery 142 9.2.1 Solid oxide electrolysis 142 9.2.2 High Temperature PEM fuel cell 143 9.2.3 Solid oxide fuel cell 144 9.2.4 Reversible solid oxide cell system 149 10 Process Chain Optimization 154 10.1 Economic optimization 154 10.1.1 Costs for by-products 154 10.1.2 Application scenario 156 10.2 Comparison of optimized process designs in process chains 156 10.2.1 Physical exergy recovery 160 10.2.2 Heat exergy recovery 160 10.2.3 Combination of physical and heat exergy recovery 165 11 Conclusion 170 12 Outlook 174 / Wasserstoff wird als einer der wichtigsten Energieträger zur Speicherung von fluktuierender Wind- und Solarenergie in einem nachhaltigen Energiesystem betrachtet. In dieser Arbeit werden Exergieeffizienz und Kostenanalysen durchgeführt, um verschiedene Pfade von Wasserstoffherstellung (PEM, alkalische oder Festoxidelektrolyse), -speicherung (Verdichtung, Verflüssigung oder Methanisierung), -transport (Trailer oder Pipeline) und -rückverstromung (PEM-, Festoxidbrennstoffzellen oder Gas- und Dampfkraftwerke (GuD)) zu vergleichen. Alle Prozessketten werden für Voll- und Teillast simuliert und ihrWirkungsgrad sowie die Kosten berechnet. Weiterhin werden Lastprofile abgeschätzt, um ein gesamtes Betriebsjahr unter schwankender Last zu simulieren. Die Ergebnisse zeigen exergetische Strom-zu-Strom-Wirkungsgrade von etwa 17.5 % bis 43 %. Die größten Verluste treten bei der Rückverstromung und bei der Herstellung von Wasserstoff auf. Methanisierung zeigt sowohl niedrigere Wirkungsgrade als auch höhere Kosten als Pfade mit reinem Wasserstoff. Während GuD-Kraftwerke sehr hohe Wirkungsgrade bei Volllast aufweisen, zeigen Brennstoffzellen im Lastfolgebetrieb über ein Gesamtjahr höhere Wirkungsgrade. Spezifische Gesamtkosten zwischen 245 e/MWh und 646 e/MWh werden durch die Simulation berechnet. Niedrigere Prozesskettengesamtkosten sind gemeinhin mit einem hohem Wirkungsgrad verbunden. Installationskosten sind auf Grund der niedrigen Volllaststundenzahl der hauptsächliche Treiber der Gesamtkosten. Um die Energiespeicherkosten der Prozessketten zu verringern, werden die Kostenreduktion durch den Verkauf von Nebenprodukten wie Sauerstoff und Wärme, sowie die Erweiterung der Anwendung untersucht. Während der Effekt des Erlöses durch den Verkauf von Sauerstoff gering ist, kann der von Wärme die Gesamtkosten signifikant verringern. Eine Erhöhung der Volllaststudenzahl durch das Einbeziehen einer Elektrolyse-Grundlast für die Bereitstellung von Wasserstoff für die mobile Anwendung zeigt auch eine deutliche Verringerung der Gesamtkosten auf bis zu 151 €/MWh bei 2337 h/a Volllaststunden. Die Optimierung des Wirkungsgrades wird durch die Analyse von physischer sowie Wärmeexergierückgewinnung durchgeführt. Dafür wird die Nutzung von Expansionsmaschinen im Gasnetz, der Einsatz von zusätzlichen Joule- und Clausius-Rankine-Prozessen, wie auch die Bereitstellung von Wärme für die Dampfelektrolyse aus der Methanisierung, der Kühlung zwischen Verdichtungsstufen und der Speicherung von Wärme analysiert. Die Berechnung zeigt, dass bei Volllast Prozessketten, die Wasserstoff mit Hilfe von Festoxidelektrolyse herstellen und diesen dann in einem GuD-Kraftwerk oder einer Festoxidbrennstoffzelle mit Clausius-Rankine- Prozess rückverstromen, exergetischeWirkungsgrade von 47 % bzw. 45.5 % erreicht werden können. Eine reversible Festoxidbrennstoffzelle, die Wärme und Wasserstoff in einem Metallhydrid speichert, kann exergetische Wirkungsgrade von 46.5 % erreichen. Die Energiespeicherkosten für diese Systeme können bei Volllast 35 bis 40 €/MWh betragen. Es kann angenommen werden, dass über ein Betriebsjahr der Wirkungsgrad steigen wird.:1 Introduction 22 2 Objective and Structure 24 3 Hydrogen as an Energy Vector 25 3.1 Mobile application focus 25 3.2 Stationary application focus 28 3.3 Studies on energy systems 32 3.4 Conclusion 36 4 Hydrogen Technology Overview 37 4.1 Hydrogen production 37 4.1.1 Electro-chemical hydrogen production 37 4.1.2 Thermo-chemical hydrogen production 42 4.1.3 Biological hydrogen production 46 4.1.4 Other hydrogen production processes 46 4.1.5 Gas cleaning 47 4.2 Hydrogen storage 49 4.2.1 Chemical compounds 49 4.2.2 Metal hydride 50 4.2.3 Physical storage 52 4.3 Hydrogen transport 54 4.3.1 Gas grid 54 4.3.2 Trailer 56 4.4 Hydrogen utilization 56 4.4.1 Thermochemical utilization 56 4.4.2 Electrochemical utilization 59 4.5 Investigated energy conversion processes 69 5 Model Description 72 5.1 Components 72 5.1.1 Electrochemical cells 72 5.1.2 Rectifier and inverter 77 5.1.3 Metal hydride storage 78 5.1.4 Liquid hydrogen storage 78 5.1.5 Chemical reactors 78 5.1.6 Catalytic burner 81 5.1.7 Blower 81 5.1.8 Compressor 82 5.1.9 Turbine 82 5.1.10 Electrical engine and generator 82 5.1.11 Heat exchanger 83 5.1.12 Mixer and splitter 84 5.1.13 Sources and sinks 85 5.2 Combined cycle gas turbine 85 5.3 Electricity grid 85 5.4 The exergy method 85 5.5 Property data 88 5.6 Cost model 88 5.7 Load profiles 90 6 Process Analysis 92 6.1 Production 92 6.1.1 Alkaline electrolysis 92 6.1.2 Proton exchange membrane electrolysis 95 6.1.3 Solid oxide electrolysis 96 6.2 Storage 100 6.2.1 Methanation 100 6.2.2 Compression 101 6.2.3 Liquefaction 101 6.3 Transport 101 6.3.1 Gas grid 101 6.3.2 Trailer 101 6.4 Utilization 102 6.4.1 Combined cycle gas turbine 102 6.4.2 Proton exchange membrane fuel cell 104 6.4.3 Solid oxide fuel cell 109 7 Process Chain Analysis 118 7.1 Exergy Efficiency 118 7.1.1 Exergy analysis for full load operation 120 7.1.2 Exergy analysis for load following operation 124 7.2 Overall Costs 125 7.2.1 Cost analysis for full load operation 125 7.2.2 Cost analysis for load following operation 129 8 Waste exergy recovery overview 135 8.1 Waste heat exergy recovery 136 8.1.1 Solid oxide electrolysis 136 8.1.2 Clausius Rankine Cycles 137 8.1.3 Joule Cycles 138 8.1.4 Combination of Joule and Clausius Rankine cycles 139 8.2 Physical exergy recovery 140 8.3 Cryo-exergy recovery 140 9 Process Optimization 141 9.1 Physical exergy recovery 141 9.2 Waste heat exergy recovery 142 9.2.1 Solid oxide electrolysis 142 9.2.2 High Temperature PEM fuel cell 143 9.2.3 Solid oxide fuel cell 144 9.2.4 Reversible solid oxide cell system 149 10 Process Chain Optimization 154 10.1 Economic optimization 154 10.1.1 Costs for by-products 154 10.1.2 Application scenario 156 10.2 Comparison of optimized process designs in process chains 156 10.2.1 Physical exergy recovery 160 10.2.2 Heat exergy recovery 160 10.2.3 Combination of physical and heat exergy recovery 165 11 Conclusion 170 12 Outlook 174

With an increasing awareness of energy consumption and CO 2emission in the population, several initiatives to reduce CO2emissions have been presented all around the world. The main part of these initiatives is a reduction of the energy consumption for existing buildings, while the others concern the building of eco-districts with low-energy infrastructures and even zero-energy infrastructures. In this idea of reducing the energy consumption and of developing new clean areas, this master thesis will deal with the high energy quality services for new urban districts. In the scope of this master thesis project, the new concept of sustainable cities and of clusters of buildings will be approached in order to clearly understand the future challenges that the world’s population is going to face during this century. Indeed, due to the current alarming environmental crisis, the need to reduce human impacts on the environment is growing more and more and is becoming inescapable. We will present a way to react to the current situation and to counteract it thanks to new clean technologies and to new analysis approaches, like the exergy concept. Through this report, we are going to analyze the concepts of sustainable cities and clusters of buildings as systems, and focus on their energy aspects in order to set indoor climate parameters and energy supply parameters to ensure high energy quality services supplies to high performance buildings. Thanks to the approach of the exergy concept, passive and active systems such as nocturnal ventilation or floor heating and cooling systems have been highlighted in order to realize the ‘energy saving’ opportunities that our close environment offers. This work will be summarized in a methodology that will present a way to optimize the energy use of all services aspects in a building and the environmental friendly characteristics of the energy resources mix, which will supply the buildings’ low energy demands.