To achieve the goal of sustainable development, the building energy system was evaluated from both the first and second law of thermodynamics point of view. The relationship between exergy destruction and sustainable development were discussed at first, followed by the description of the resource abundance model, the life cycle analysis model and the economic investment effectiveness model. By combining the forgoing models, a new sustainable index was proposed. Several green building case studies in U.S. and China were presented. The influences of building function, geographic location, climate pattern, the regional energy structure, and the technology improvement potential of renewable energy in the future were discussed. The building’s envelope, HVAC system, on-site renewable energy system life cycle analysis from energy, exergy, environmental and economic perspective were compared. It was found that climate pattern had a dramatic influence on the life cycle investment effectiveness of the building envelope. The building HVAC system energy performance was much better than its exergy performance. To further increase the exergy efficiency, renewable energy rather than fossil fuel should be used as the primary energy. A building life cycle cost and exergy consumption regression model was set up. The optimal building insulation level could be affected by either cost minimization or exergy consumption minimization approach. The exergy approach would cause better insulation than cost approach. The influence of energy price on the system selection strategy was discussed. Two photovoltaics (PV) systems – stand alone and grid tied system were compared by the life cycle assessment method. The superiority of the latter one was quite obvious. The analysis also showed that during its life span PV technology was less attractive economically because the electricity price in U.S. and China did not fully reflect the environmental burden associated with it. However if future energy price surges and PV system cost reductions were considered, the technology could be very promising for sustainable buildings in the future.

In this work several decomposition strategies for the synthesis / design optimization of highly coupled, highly dynamic energy systems are formally presented and their implementation illustrated. The methods are based on the autonomous optimization of the individual units (components, sub-systems or disciplines), while maintaining energy and cost links between all units, which make up the overall system. All of the approaches are designed to enhance current engineering synthesis / design practices in that: they support the analysis of systems and optimization in a modular way, the results at every step are feasible and constitute an improvement over the initial design state, the groups in charge of the different unit designs are allowed to work concurrently, and permit any level of complexity as to the modeling and optimization of the units. All of the decomposition methods use the Optimum Response Surface (ORS) of the problem as a basis for analysis. The ORS is a representation of the optimum objective function for various values of the functions that couple the system units1. The complete ORS or an approximation thereof can be used in ways, which lead to different methods. The first decomposition method called the Local Global Optimization (LGO) method requires the creation of the entire ORS by carrying out multiple unit optimizations for various combinations of values of the coupling functions. The creation of the ORS is followed by a system-level optimization in which the best combination of values for the coupling functions is sought The second decomposition method is called the Iterative Local Global Optimization (ILGO) scheme. In the ILGO method an initial point on the ORS is found, i.e. the unit optimizations are performed for initial arbitrary values of the coupling functions. A linear approximation of the ORS about that initial point is then used to guide the selection of new values for the coupling functions that guarantee an improvement upon the initial design. The process is repeated until no further improvement is achieved. The mathematical properties of the methods depend on the convexity of the ORS, which in turn is affected by the choice of thermodynamic properties used to charecterize the couplings. Examples in the aircraft industry are used to illustrate the application and properties of the methods. / Ph. D.

The objective of this thesis is to establish the utility and limitations of using exergy (a thermodynamic measure of energy quality, or ability to perform work) as a resource consumption metric, and to investigate what role exergy may play in resource consumption decision-making. To do so, this thesis assessed three exergy-based resource consumption methodologies: the Exergy Replacement Cost; Eco-exergy; and Emergy. Furthermore, fundamental properties of exergy were revisited, including the exergy reference state, and the derivations of both concentration and non-flow exergy. The results of the analysis indicate three significant problem areas with applying exergy toward resource valuation. First, the exergy derivation level conflicts with the resource valuation level regarding important requirements and assumptions: the exergy reference environment is modelled as an infinitely large system in internal chemical equilibrium, and this is in incomparable to the real world; and, the derivation of non-flow exergy values items based solely upon chemical concentrations, whereas at the resource consumption level, work producing items are valuable based primarily upon chemical reactivity. Second, exergy proponents have not adequately addressed the many different and critical perspectives of exergy, including exergy as: harmful or helpful; organizing or disorganizing; a restricted or unrestricted measure of potential useful work; and applied to value systems or specific items. Third, none of the resource consumption methodologies properly apply exergy: the Exergy Replacement Cost primarily focuses on mineral upgrading; Eco-exergy is improperly derived from exergy; and Emergy has switched from being energy-based to exergy-based without any reformulation of the methodology. For the reasons provided above, among others, this author concludes there is currently no justified theoretical connection between exergy and resource value, and that there is a disjunction between how exergy is derived and how it is applied. Non exergy-based applications for the three resource consumption methodologies are proposed.

The objective of this thesis is to establish the utility and limitations of using exergy (a thermodynamic measure of energy quality, or ability to perform work) as a resource consumption metric, and to investigate what role exergy may play in resource consumption decision-making. To do so, this thesis assessed three exergy-based resource consumption methodologies: the Exergy Replacement Cost; Eco-exergy; and Emergy. Furthermore, fundamental properties of exergy were revisited, including the exergy reference state, and the derivations of both concentration and non-flow exergy. The results of the analysis indicate three significant problem areas with applying exergy toward resource valuation. First, the exergy derivation level conflicts with the resource valuation level regarding important requirements and assumptions: the exergy reference environment is modelled as an infinitely large system in internal chemical equilibrium, and this is in incomparable to the real world; and, the derivation of non-flow exergy values items based solely upon chemical concentrations, whereas at the resource consumption level, work producing items are valuable based primarily upon chemical reactivity. Second, exergy proponents have not adequately addressed the many different and critical perspectives of exergy, including exergy as: harmful or helpful; organizing or disorganizing; a restricted or unrestricted measure of potential useful work; and applied to value systems or specific items. Third, none of the resource consumption methodologies properly apply exergy: the Exergy Replacement Cost primarily focuses on mineral upgrading; Eco-exergy is improperly derived from exergy; and Emergy has switched from being energy-based to exergy-based without any reformulation of the methodology. For the reasons provided above, among others, this author concludes there is currently no justified theoretical connection between exergy and resource value, and that there is a disjunction between how exergy is derived and how it is applied. Non exergy-based applications for the three resource consumption methodologies are proposed.

<p>Though mandatory to be pursued, improved energy efficiency is not the only target to reach. The quality of energy has to be assessed as well. Most of the overall energy use in residential building is for low temperature heat, i.e. temperatures relatively close to the outdoor conditions. From a thermodynamic point of view, this is a degraded form of energy with low potential to be converted into work. On the other hand energy demand is mostly met with high quality energy, such as electricity and natural gas. There is a mismatch between supply and demand, which is not clearly shown by the sole energy analysis. Target of this thesis is to analyze the energy use in buildings from the point of view of its quality, to provide effective theoretical and calculation tools to investigate this mismatch, to assess its magnitudo and to propose improvements aiming at a more rational use of the energy. The idea behind the quality is clarified with the concept of exergy.</p><p>The potential for improvement in space heating is shown. In no heating system the overall exergy efficiency is above 20%, with fossil fuels. Using direct electricity heating results in exergy efficiency below 7%. Most of the household appliances processes have low-exergy factors but still are supplied with electricity. This results in poor exergy efficiencies and large exergy losses.</p><p>Systems are poorly performing because little consideration is explicitly given to energy quality. Policies to lower the energy demand, though vital as first step towards an improved use of energy, should not neglect the exergy content.</p><p>The problem is then shifted to find suitable supplies. Electricity can be exploited with low exergy losses with high-COP heat pumps. Use of fossil fuels for heating purposes should be avoided. District heating from cogeneration and geothermal proves to be a suitable solution at the building level. The issues connected to its exploitation forces to shift the boundary layers of the analysis from the building level to the community level. A rational use of energy should address the community level. The system boundaries have to be enlarged to a dimension where both the energy conversion and use take place with reduced energy transportation losses. This is a cost-effective way to avoid the waste of the exergy potential of the sources with exergy cascade and to make it possible the integration of with renewable sources. Exergy efficiency of the buildings is a prerequisite for a better of energy in this field.</p> / IEA ECBCS Annex 49: Low Exergy Systems for High Performance Buildings and Communities / ESF Cost C24: Analysis and Design of Innovative Systems for Low-EXergy in the Built Environment: COSTeXergy

O presente trabalho procura estudar e compreender os processos reativos de chama, tentando identificá-los através de uma abordagem químico termodinâmica, em contraposição às análises clássicas, puramente cinético-químicas. Estas são justificadas por se considerar este tipo de fenômeno como existindo em condições distantes da condição de equilíbrio termodinâmico e não passíveis de análise termodinâmica, coisa que, através desta investigação, pretende-se questionar. Neste estudo, considerou-se a chama como ocorrendo em um escoamento unidimensional ideal, em regime permanente, em fluido perfeito, i.e. não há viscosidade e dividiu-se a chama em fatias, em que a exergia química era transformada em exergia térmica, em se adaptando \"o problema do tijolo aquecido\" (ou \"hot brick problem\"). O processo reativo global de chama adiabática foi, por evidência experimental, considerado como sendo bi-variante i.e. completamente determinado com a definição da pressão e da temperatura dos reagentes, conhecidos a priori, em espécie e em quantidade. O teorema de Duhem1 nos garante, portanto, que caso se estabeleça o equilíbrio, este estaria determinado. Aqui se procurou reunir subsídios para sua identificação. Investigaram-se a modelagem de chamas adiabáticas e reversíveis de duas fatias, consideradas como meio efetivo, em se igualando a exergia química à exergia térmica, bem como o que se considerou como sendo chamas adiabáticas de duas fatias de máxima irreversibilidade interna. Para a chama adiabática irreversível obteve-se temperaturas de ignição próximas à temperatura de autoignição para 4 de 6 combustíveis. Por fim, conclui-se que a chama contínua não é o limite da chama irreversível de infinitas fatias. Enquanto que aquela tem irreversibilidade máxima, segundo o modelo apresentado, a irreversibilidade desta é um máximo relativo. / The present study attempts at an understanding of the reactive processes within a flame. A chemical thermodynamics approach is employed in juxtaposition to the classical analysis which are purely chemical kinetic. These are justified because this phenomenum is considered to take place far from equilibrium conditions and not subject to thermodynamic analysis. This fact will be questioned in this study. A one-dimensional, ideal and steady flow flame was considered. The reactive process of an adiabatic flame was, by experimental evidence, considered to possess two degrees of freedom, i.e it would be completely determined by defining the reactants\' pressure and temperature, whose species and quantities were a priori known. Duhem\'s theorem2 tells us that if equilibrium is estabilished, it would be fully determined. An adiabatic and reversible two-sliced flame (the effective medium) was determined by equating the chemical exergy of the flame to the physical exergy of the two slices relative to the ignition point. Also, the constrained extremum of the difference between the chemical and physical exergies allowed the relative maximum of an internally irreversible adiabatic flame to be determined. For the irreversible flame, close simulation of the autoignition temperature for 4 of 6 fuels was obtained. Finally, the conclusion that a continuous flame is not the limit of an irreversible flame with infinite slices is demonstrated. Whilst that flame is the flame with maximum irreversibility, this flame has a relative maximum of internal irreversibility.

The primary objective of this work is to determine the Kalina cycle's suitability for thermal power conversion from a pressurized water reactor. Several previous papers have examined this application, but these either lack proof of concept or make unfeasible assumptions. This work expands current knowledge by simulating the Kalina cycle and comparing it to current pressurized water reactor Rankine cycles in order to identify which is more efficient. Prerequisite to the modeling is a simulation tool capable of modeling the thermodynamics of ammonia/water mixtures. Instead of using an existing program, a new one called Clearwater is used. This tool is based on a preexisting Gibbs free energy "super" equation of state. Algorithms for vapor-liquid equilibrium calculations and phase identification are presented. Clearwater will be distributed online as open-source code to aid future developers of ammonia/water power and refrigeration cycles. A comparison of single-stage Kalina and Rankine cycles driven by heat from PWR core coolant suggests that the Kalina cycle is not well suited to the application. Any benefit from the Kalina cycle's ability to match temperature profiles in the boiling region of the steam generator is outweighed by other drawbacks. These include the cycle's 1) increased turbine exhaust pressure and 2) lower average heat absorption temperature caused by its working fluid's relatively high liquid heat capacity, both of which lower efficiency. Having concluded this, an attempt is made to quantify the conditions under which the Kalina cycle produces more power than the Rankine cycle. Both cycles are optimized for a range of heat source inlet and outlet temperatures between 350 ℃ and 525 ℃. When both cycles absorb the same amount of heat from the source"”i.e., when source outlet temperature is constrained"” the Kalina cycle is less effective for small source temperature drops. When outlet temperature is unconstrained, the Kalina cycle outperforms the Rankine cycle for all but the lowest inlet temperature. This is due to the Kalina cycle's non-isothermal boiling profile, which allows it to absorb low temperature heat at relatively high pressure. Because of its isothermal boiling profile, the Rankine cycle cannot capture low temperature heat as effectively, so it performs worse over large, unconstrained source temperature drops.

An exergy analysis on gasification and oxyburn processes has been conducted. Equilibrium modeling in Aspen Plus© was used to develop a methodology for evaluating different fuels for gasification based on exergy analysis. The exergetic efficiency of gasifying a fuel strongly depended on the carbon boundary point, which is the equivalence ratio limit at which all carbon is converted to gaseous products in an adiabatic system. When evaluating a fuel for gasification, it is important to consider if the temperature of the carbon boundary point falls below 1050 K, which is also the temperature that the water-gas shift reaction begins to favor CO2 and H2. It was found that the rational efficiency, a common exergetic efficiency used in the literature, remained relatively unchanged at equivalence ratios past the carbon boundary point. A different exergetic efficiency, termed the gas efficiency, was proposed that showed better variance to the equivalence ratio and related better to the desired operation of the gasifier. It is shown that an oxyburn process can be used to decrease the energy requirement of capturing CO2 if it is run closer to stoichiometric. Flue gas recirculation was investigated as a means to improve gasification efficiency, lower the reactor temperature of coal gasification, and capture CO2. It was found that a higher percentage of flue gas must be recirculated back to the gasifier if flue gas from combustion with pure O2 is used instead of air. Using flue gas recirculation allowed the gasifier equivalence ratio to be increased without solid carbon in the products. Increasing the equivalence ratio also resulted in a slight increase in the maximum achievable exergetic efficiency of the gasifier. Finally, an internal combustion engine model was developed based on closed-system thermodynamics and successfully integrated with the open-system realm of Aspen Plus©.

Biomass co-firing with coal exhibits great potential for large scale utilization of biomass energy in the near future. In the present work, energy and exergy analyses are carried out for a co-firing based power generation system to investigate the impacts of biomass cofiring on system performance and gaseous emissions of CO2, NOx, and SOx. The power generation system considered is a typical pulverized coal-fired steam cycle system, while four biomass fuels (rice husk, pine sawdust, chicken litter, and refuse derived fuel) and two coals (bituminous coal and lignite) are chosen for the analysis. System performance is evaluated in terms of important performance parameters for different combinations of fuel at different co-firing conditions and for the two cases considered. The results indicate that plant energy and exergy efficiencies decrease with increase of biomass proportion in the fuel mixture. The extent of decrease in energy and exergy efficiencies depends on specific properties of the chosen biomass types. The results also show that the increased fraction of biomass significantly reduces the net CO2 emissions for all types of selected biomass. However, gross CO2 emissions increase for all blends except bituminous coal/refuse derived fuel blend, lignite/chicken litter blend and lignite/refuse derived fuel blend. The reduction in NOx emissions depends on the nitrogen content of the biomass fuel. Likewise, the decrease in SOx emissions depends on the sulphur content of the biomass fuel. The most appropriate biomass in terms of NOx and SOx reduction is sawdust because of its negligible nitrogen and sulphur contents. / UOIT

Biomass cogeneration systems can generate power and process heat simultaneously from a single energy resource efficiently. In this thesis, three biomass cogeneration systems are examined. Parametric analysis of back pressure steam turbine cogeneration system, condensing steam turbine cogeneration system and double back pressure steam turbine cogeneration system is conducted. Energy and exergy analyses are performed for three biomass based cogeneration configurations. The parametric analysis demonstrates the effects of varying operating conditions (temperature: 340 oCto 520 oCand pressure: 21bar to 81bar). A higher steam inlet temperature and pressure to the turbine yields better energy and exergy efficiencies and performance. Steam inlet conditions to the turbines and process heater requirements influence the power output and cogeneration system efficiencies. Greenhouse gases reduction is achieved by cooperating cogeneration systems with biomass to reduce CO2 emissions and global warming potential in the power industrial sectors. / UOIT