A utilização racional e otimização de recursos energéticos é tema cada vez mais presente na indústria, e busca atender a critérios normativos e aspectos econômicos. Entre os métodos de análise utilizados para verificação e melhoria de eficiência energética, nas últimas décadas a Exergia vem se destacando como a ferramenta mais indicada para esse tipo de avaliação. Esse estudo realiza análise exergética em uma planta de processamento típica de uma plataforma do tipo FPSO operando em águas do litoral brasileiro. Atenção especial é dispensada à planta de compressão de gás, que possui sistema de remoção de CO2 do gás através de membranas. Conforme composição dos poços e/ou restrições operacionais, o fluxo de gás pode ser desviado do sistema de remoção de CO2, criando modos de operação. No modo de operação A todo gás do sistema de remoção de CO2 é desviado, de forma que seja possível apenas a injeção desse gás. O modo B utiliza plenamente o sistema de remoção de forma a permitir exportação máxima de gás. Já o modo de operação C trata parcialmente o gás através desse sistema, de forma a permitir exportação e injeção parciais de gás. Além dos modos de operação, são estudados também os efeitos da variação da vazão de gás exportado e da composição do petróleo (teor de CO2 e BS&W) no balanço exergético da plataforma. A combinação dessas três variáveis (modos de operação, vazão de gás exportado e composição do petróleo) representa 177 cenários de produção. O estudo desses cenários de produção por meio de determinados parâmetros (eficiência exergética, consumo específico de exergia, emissões de CO2, emissões específicas de CO2 e índice de renovabilidade exergética) permite verificar a influência de cada variável na performance da planta. / The rational use of energy resources is a theme increasingly discussed at the Industry, and the energetic optimization of processes is necessary in order to fulfill normative, as well as economic criteria. Among the analysis methods in use for verifying and improving the energetic efficiency, during last decades the Exergy has been highlighted as the most appropriated tool for these evaluations. This study performs exergetic analysis in a typical process plant in a FPSO operating in the brazilian shore waters. Special attention is given to the gas compression process plant, which has a CO2 membranes gas removal system. According to composition of well and/or operational restrictions, the gas flow can be deviated from the CO2 gas removal system, creating the operational modes. The operational mode A deviates all the gas from the CO2 gas removal system, allowing just its injection into the reservoir. The mode B uses entirely the CO2 removal system in a way that a maximum of gas exportation is possible. And the operational mode C treats partially the gas through the system, allowing partial exportation and re-injection of the gas. Besides the operational modes, the influence of export gas flow and well fluid composition (CO2 and BS&W content) in the exergy balance are also evaluated. The combination of these three variables (operational modes, export gas flow rate and well fluids composition) represents 177 production scenarios. The evaluation of these production scenarios affecting specific parameters (exergy efficiency, specific exergetic consumption, CO2 emissions, CO2 specific emissions and exergetic renewability index) allows to identify the importance of each variable in process plant performance.

Biomass is an attractive renewable energy resource for electricity generation, which has the potential to protect air quality, reduce dependence on fossil fuel, and improve forest health. Biomass gasification is a technology that transfers solid or liquid biomass into gaseous energy carrier (syngas) to increase the efficiency of electricity generation. The objective of this thesis is to supply a detailed feasibility study and provide a state-of-the-art economical pathway on biomass gasification application. The work of this dissertation can be separated into two parts: commercial-scale biomass integrated gasification combined cycle (BIGCC) power plants comparison and other biomass gasification system design. The first part compares eight BIGCC systems with three groups of technology variations of gasification agent, syngas combustion method, and CO2 capture and storage. By comparing on performance, economic, and environmental indicators of these systems, it is found that BIGCC systems have higher exergy efficiency and lower emissions than biomass combustion electricity production system and electricity grid. However, its levelized cost of electricity is around 27% higher than the average electricity market price. To reduce the BIGCC system’s cost, in the second part of this thesis, the potential for waste material gasification has been discussed. This part discussed the tire gasification and the gasification technology application for avian influenza poultry management. Results showed that tire gasification has a lower cost than natural gas which has the potential to reduce the BIGCC system’s cost. Moreover, gasification is an effective and economical available approach for avian influenza poultry management.

A poly-generation system can be defined as the simultaneous and collocated generation of two or more energy supply types, aimed to maximize the utilization of the thermodynamic potential (efficiency) of the consumed energy resources. A Polygeneration system may involve co-generation (power and heat) or tri-generation (power, heat, and cold) processes and may also be connected to a district energy system. A poly-generation plant reclaims heat in a useful form that would be wasted otherwise in separate electricity and heat (and chilled water in some cases) generating systems. By this way a poly-generation plant provides a variety of benefits including improved efficiency and fuel savings, reduction of the primary energy demand total cost of utility service and unit fuel cost, independency for energy and protection of environment. With the overall efficiencies in the range of 70-90%, poly-generation systems are gaining popularity all around the world. including Turkey. In spite of all their potential benefits and increasing interest for poly-generation systems, there is not yet any rating, testing, metrication and classification guidelines and standards. It is indeed very important to rate the performance and energy savings potential, determine the heat and power outputs, estimate the system efficiency and the ratio of the split of the power produced between thermal and electric. These are the information which are hard to determine since there are not enough common test standards, rating standards and nor consensus-based terminology for combined heat and power systems in the world literature. Even the classification of the cogeneration systems is hardly globalized. Aim of this study is to develop a common procedure with respect to the above shortcomings for testing and rating poly-generation systems under realistic operating conditions with accurate formulae which will help to contribute energy and exergy economy by establishing a robust metrication standard based on new evaluation parameters. This study aims to find a procedure to evaluate a poly-generation system by establishing standard test methods and evaluation tools in terms of parameters like energy and exergy characteristics of thermal and electric loads, temperature demand and power split for determining operational characteristics of the system. This may be achieved by revising and expanding DIRECTIVE 2004/8/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL. A case study is expected to be based on a trigeneration power plant to be received within the framework of the EU FP6 HEGEL Poly-generation project, to be tested at METU, which has a capacity of 145 kW electric and 160 kW useful heat.

Engineering for sustainable development requires prudent utilization of resources under economic, environmental and societal constraints. Resource utilization must follow a holistic approach. This brings in a need for comprehensive metrics which are simple, standard and universal. Thermodynamics may offer a metric that focuses on both quality and quantity of energy resources which may carry information to be combined with other metrics. This metric may be a thermodynamic property called exergy or available energy, which provides a better insight into resource use in both energy and non-energy producing systems. This thesis is devoted to a study of the exergy concept in manufacturing. A high volume PCB assembly, manufactured in a state of the art soldering facility is chosen for the study. Various mass and energy resources flowing through the production line were quantified in terms of exergy. On the basis of exergy content and exergy utilization in the production process, the sustainability in terms of resources use is discussed. An early version of this approach was presented at the International Symposium on Sustainable Systems and Technologies, IEEE, Washington DC, in May 2010.

The approach advocated in this work implements energy/exergy analysis and indirectly an irreversibility evaluation to a continuous manufacturing process involving discrete net shape production of compact heat exchangers through a complex controlled atmosphere brazing (CAB) process. The system under consideration involves fifteen cells of a continuous ramp-up heating, melting, reactive flow, isothermal dwell, and rapid quench solidification processing sequence during a controlled atmosphere brazing of aluminum compact heat exchangers. Detailed mass, energy, and exergy balances were performed. The irreversibility sources were identified and the quality of energy utilization at different processing steps determined. It is demonstrated that advanced thermodynamics metrics based on entropy generation may indicate the level of sustainable energy utilization of transient open systems, such as in manufacturing. This indicator may be related to particular property uniformity during materials processing. In such a case, the property uniformity would indicate systems distance from equilibrium, i.e., from the process sustainable energy utilization level. This idea is applied to net shape manufacturing process considered. A metric based on exergy destruction is devised to relate the heat exchanger temperature uniformity and the quality. The idea advocated in this thesis will represent the coherent framework for developing energy efficient, economically affordable and environmentally friendly manufacturing technology.

Global warming is an unequivocal fact proved by the persistent rise of the average temperature of the earth. IPCC reported that scientists were more than 90 % certain that most of the global warming was caused by increasing concentrations of greenhouse gases (GHG) produced by human activities. One alternative to combat the GHG is to explore technologies for utilizing CO2 already generated by current energy systems and develop methods to convert CO2 into useful combustible gases. Two-step conversion of CO2 with catalysts is one of the most promising methods. Ceria (CeO2) is chosen as the main catalyst for this conversion in the thesis. It releases O2 when it is reduced in a heating process, and then absorbs O2 from CO2 to produce CO when it is re-oxidized in a cooling process. To make the conversion economic, solar power is employed to drive the conversion system. In this thesis, a flexible system with fluidized bed reactors (FBRs) is introduced. The thermogravimetric analysis (TGA) was carried out to examine the performance of ceria during its reduction and oxidation. Subsequently, the exergy analysis was used to evaluate the system’s capability on exporting work. The theoretical fuel to chemical efficiency varied from 4.85 % to 43.2 % for CO2 conversions. To investigate the operation mechanism of the system, a mathematical model was built up for the dynamic simulation of the system. Variables such as temperatures and efficiencies were calculated and recorded for different cases. The optimum working condition was found out to be at 1300 ⁰C for the commercial type of ceria. Finally, an experimental system was set up. The hydrodynamics and heat transfer in the fluidized bed reactor were studied. A CFD model was built up and validated with the experimental trials around 120 ⁰C. The model was then used as a reliable tool for the optimization of the reactor. The entire work in the thesis follows the procedure of developing an engineering system. It forms a solid basis for further improvements of the system to recycle CO2. / <p>QC 20141006</p>

Neste trabalho, o conceito de exergia é utilizado na proposição de um indicador de idade exergética que permita observar alterações da expectativa de vida de um indivíduo a partir da exergia destruída durante seu ciclo de vida. Para tal, a análise exergética é aplicada ao corpo humano e a volumes de controle menores dentro do corpo para diferentes cenários nos quais ocorram alterações nas reações metabólicas, a fim de determinar a taxa de exergia destruída em função da idade cronológica. Com essa informação, é calculado o indicador de idade exergética, podendo comparar a taxa de progressão da vida do indivíduo nas diferentes condições avaliadas com base na ideia de que há um valor máximo de exergia destruída acumulada durante a vida. Os efeitos do tabagismo e da obesidade são avaliados, e observa-se uma redução de aproximadamente 15 anos na expectativa de vida de fumantes, enquanto, para os obesos, o indicador mostra um aumento. Portanto, a identificação da obesidade como um fator de risco se deve ao desenvolvimento de patologias associadas à obesidade, e não ao aumento do metabolismo e à presença de gordura corporal subcutânea. Uma vez que maior parte das patologias relacionadas à obesidade está associada ao sistema cardiovascular, é proposto um modelo exergético do coração. Observa-se um aumento da taxa de exergia destruída na presença de hipertensão, que leva a uma redução de cerca de quatro anos na expectativa de vida. Por fim, é proposto um modelo do metabolismo de uma célula de câncer que leva em conta as alterações das rotas metabólicas, a partir do qual é possível observar um aumento de quase três vezes no metabolismo exergético de uma célula de câncer em comparação com uma célula saudável. A análise da progressão de um tumor indica que, na ausência de tratamento, a redução da expectativa de vida é de 27 anos. Além disso, no caso de tratamento, cada seis meses na presença da doença reduz a expectativa de vida em cerca de quatro anos. / In the present work, the concept of exergy is applied in order to propose an index of exergetic age that allows observing changes in life expectancy of a subject based on the exergy destruction throughout the life cycle. To do so, exergy analysis is applied to the human body and smaller internal control volumes for different scenarios where changes in metabolic reactions take place, aiming at determining the destroyed exergy rate as a function of chronological age. From this data, exergetic age index is calculated, enabling to compare the rate of life progression of the subject under different circumstances, based on the idea that there is a maximum value of cumulative destroyed exergy throughout life. The effects of smoking and obesity are evaluated and a reduction of approximately 15 years is observed for smokers, while, for obese people, the index shows an increase. Thus, the identification of obesity as a risk factor is more associated to the development of obesity-related diseases than to the metabolic rate increase and the presence of a thicker layer of subcutaneous fat. Since most of the obesity-related diseases are associated to the cardiovascular system, an exergy model of the human heart is proposed. The model reports an increase of the exergy destruction in case of hypertension that causes a reduction of about four years in life expectancy. Finally, a model of the metabolism of a cancer cell is proposed taking into account the changes in the metabolic paths, from which it is possible to observe a threefold increase of the exergy metabolism of a cancer cell, in comparison to a healthy one. The analysis of tumor progression indicates that, in the absence of treatment, the reduction of life expectancy is about 27 years. Furthermore, in case of treatment, each six months living with the disease causes a reduction of almost four years in life expectancy.

A análise exergética é aplicada ao ser humano para avaliar a qualidade dos processos de conversão de energia no corpo e seus sistemas, assim como nos processos bioquímicos do metabolismo. Sabe-se que a vida tem um início, um desenvolvimento e um fim, ou seja, um típico exemplo de processo irreversível. Como tanto a idade cronológica como a entropia gerada são grandezas positivas (caminham no mesmo sentido), esta última passa a ser denominada de flecha do tempo (arrow of time). Assim, a partir da aplicação da Segunda Lei da Termodinâmica, torna-se possível desenvolver e aplicar índices baseados no conceito de exergia destruída/entropia gerada e rendimento exergético para diferentes áreas do conhecimento como medicina (comparação de técnicas de hipotermia), esportes (teste ergoespirométrico) e engenharia (conforto térmico). Para tal, propõe-se um modelo do corpo humano que leva em conta a transferência de exergia para o ambiente, a qual é causada pela radiação, convecção, vaporização e respiração. O metabolismo exergético é calculado com base na variação da exergia de três reações de oxidação: carboidratos, lipídeos e aminoácidos. Para condições ambientais transientes, calcula-se a variação temporal da exergia do corpo, e ainda, o máximo trabalho que o corpo pode executar a partir da hidrólise do ATP (adenosina trifosfato). O corpo humano aproveita aproximadamente 60% da exergia dos macronutrientes ingeridos na forma de ATP, 5% é dissipada na forma de calor e o restante destruída. Se o indivíduo estiver em repouso, toda a exergia da molécula de ATP é destruída ou dissipada na forma de calor. A exergia destruída tende a diminuir em função da idade tanto para condição basal como também para atividades físicas. Calculou-se que a exergia destruída durante uma vida equivale a 3091MJ/kg (ou entropia gerada de 10,2MJ/kgK). O rendimento exergético, no entanto, diminui em decorrência da idade para condição basal, porém aumenta durante atividades físicas. Pode-se ainda afirmar que o corpo destrói menos exergia e é mais eficiente quando submetido a condições de alta temperatura operativa e baixa umidade relativa. A análise exergética acarretou em interpretações complementares ao balanço de energia, pois, a partir de sua aplicação, foi possível distinguir corredores de acordo com o nível de atividade física, ou seja, corredores mais bem treinados podem realizar mais trabalho para o mesmo valor de exergia destruída. Finalmente, foi possível identificar diferentes técnicas de hipotermia tomando por base a comparação das eficiências exergéticas. / Exergy analysis is applied to the human being aiming to assess the quality of the energy conversion processes that take place in the body, its several of systems and in biochemical reactions involved in these processes. It is known that life has a beginning, a development and an end, therefore, it is a typical example if irreversible process. As the chronological age and entropic generation are positive quantities (increases in the same direction), this last one is named arrow of time. Hence, it becomes possible to obtain indices based on the concept of destroyed exergy and exergy efficiency for different areas of knowledge such as: medicine (different techniques of hypothermia), sports (ergoespirometric test) and mechanical engineer (thermal comfort). To this end, it is proposed a model of the human body which takes into account the exergy transfer rates to the environment associated with radiation, convection, vaporization and respiration. The metabolism exergy basis is calculated based on the exergy variation of the reactions of oxidation of three reference substances: carbohydrates, lipids and amino acids. For transient environmental conditions it is calculated the exergy variation of the body over time. Moreover, it is possible to calculate the maximum work that can be obtained from the hydrolysis of ATP (adenosine triphosphate). This procedure was applied to a thermodynamic model of human body for basal conditions and to experimental results of runners during different level of physical activities. The human body uses about 60% of the exergy of nutrients to obtain ATP, the rest is destroyed or dissipated as heat. Destroyed exergy rate tends to decrease as a function of lifespan (for basal conditions and during physical activities). The destroyed exergy during lifespan was calculated as 3091MJ/kg (or entropy production of 10.2MJ/kgK). The exergy efficiency decreases as a function of age in basal condition, but it increases during physical activities. The destroyed exergy rate is smaller and the exergy efficiency is greater for high operative temperatures and low relative humidities. The exergy analysis led to additional information regarding the First Law of Thermodynamics, because from its application it was possible to differentiate runners according to their training level, for the same destroyed exergy better trained subjects could perform more work. Finally it was possible to distinguish different techniques of hypothermia from the concept of exergy efficiency.

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.

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.