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[en] Prediction models, based on ultimate analysis of biomass on dry basis (db) which is leveraged to predict chemical exergy, were proposed in this study. A new concept — chemical exergy per equivalent of available electrons transferred to oxygen (reductance degree) of model 1 was established. The result shows that chemical exergy per reductance degree of model 1 is relatively constant for the values of most biomass (db) beyond the±1% relative error range. A modified reductance degree of biomass was presented, whereas oxygen (O) content was neglected due to its inaccurate value and the high p-value for the coefficient of O variable. Chemical exergy per modified reductance degree of models 2 and 3 was approximated to be nearly a constant. Thus, two theoretical prediction models (model 2 and model 3) for the biomass (db) with and without sulfate (920.08(C/3 + H + S/8), 920.72(C/3 + H)) were established, respectively. The coefficients of the two models are of almost the same value, which indicates that the S content has also a negligible effect on chemical exergy. Model 3 (920.72(C/3 + H)) is also herein proposed for prediction of exergy of biomass. The average relative errors of model 1, model 2 and model 3 are 2.882%, 0.643% and 0.634%, respectively. - Highlights: • A new concept — chemical exergy per (modified) reductance degree is established. • Chemical exergy per modified reductance degree is approximately constant. • Estimation model of chemical exergy based on new concept provides higher accuracy. • Chemical exergy of biomass (db) can be easily estimated by simply using C and H.
[en] The processes of power production and low temperature heat are analyzed on the basis of exergic energy production. The efficiency of exergic electric power varies as a function of the applied technology from 40 to 55 percent while the efficiency of combustion and heat transfer is as low as 22 percent. Higher efficiencies are obtained by heat power coupling and heat pumps. (A.S.)
[en] The concept of sustainability was developed from thermodynamic properties applied to complex adaptive systems. The origins of the perception about sustainable development and limitation in its application to analyze the interaction between a system and its surroundings were described. The properties of a complex adaptive system were taken as basis to determine how a system can to be affected by the resources restriction and irreversibility of the processes. The complex adaptive system was understood using the first and second law of thermodynamics, generating a conceptual framework to define the sustainability of a system. The contributions developed by exergy were shown to analyze the sustainability of systems in an economic, social and environmental context
[es]El concepto de sustentabilidad fue desarrollado a partir de propiedades termodinamicas aplicadas a sistemas adaptativos complejos. Los origenes de la percepcion sobre el desarrollo sustentable y la limitacion en su aplicacion para analizar la interaccion entre un sistema y su entorno fueron descritas. Las propiedades de un sistema adaptativo complejo fueron tomadas como base para determinar como un sistema puede ser afectado por la restriccion de recursos e irreversibilidad de los procesos. El sistema adaptativo complejo fue comprendido utilizando la primera y segunda ley de la termodinamica, generando un marco conceptual para definir la sustentabilidad de un sistema. Los aportes desarrollados por la exergia fueron mostrados para analizar la sustentabilidad de sistemas en un contexto economico, social y ambiental
[en] Highlights: • The overall energy and exergy efficiencies of the plant is found to be 59.37% and 38.99% respectively. • Performance assessment of a cement plant indicates that the calcination process involves the highest portion of energy losses. • The specific exergetic cost cement produced by the cement plant is calculated to be 180.5 USD/GJ. • The specific cement manufacturing cost is found to be 41.84 USD/ton. - Abstract: This paper is Part 2 of the study on the thermodynamic and exergoeconomic analysis of a cement plant. In Part 1, thermodynamic and exergoeconomic formulations and procedure for such a comprehensive analysis are provided while this paper provides an application of the developed formulation that considers an actual cement plant located in Gaziantep, Turkey. The overall energy and exergy efficiencies of the plant is found to be 59.37% and 38.99% respectively. The exergy destructions, exergetic cost allocations, and various exergoeconomic performance parameters are determined by using the exergoeconomic analysis based on specific exergy costing method (SPECO) for the entire plant and its components. The specific unit exergetic cost of the farine, clinker and cement produced by the cement plant are calculated to be 43.77 USD/GJ, 133.72 USD/GJ and 180.5 USD/GJ respectively. The specific manufacturing costs of farine, clinker and cement are found to be 3.8 USD/ton, 33.11 USD/ton and 41.84 USD/ton respectively
[en] Splitting the exergy destruction into endogenous/exogenous and unavoidable/avoidable parts represents a new development in the exergy analysis of energy conversion systems. This splitting improves the accuracy of exergy analysis, improves our understanding of the thermodynamic inefficiencies and facilitates the improvement of a system. An absorption refrigeration machine is used here as an application example. This refrigeration machine represents the most complex type of a refrigeration machine, in which the sum of physical and chemical exergy is used for each material stream
[en] An indivisible relation between exergy of labour as well as of the energy resources and real economics are theoretically shown. In discussions on historical changes of productive activities of human beings from agriculture to industries, the proof of the theory of labour and the existence of an upper ceiling on Gross National Product (GNP) are given. The essential role of exergy in the market economy system in terms of productivities of goods, as well as their exchange are discussed. (Author)
[en] The technologies developed from 1973 on rational use, conservation and efficiency in the use of energy updated in a framework of sustain ability energetic and environment protection, it has not taken into account the concepts of quality of energy within of any energetic system (Source - Technology - Final Use), neither the favorable economic and technical implications of adopting the concepts of the Exergy and of exegetic efficiency, derivatives from the Second Law of the Thermodynamic, those which should be included as methods in the environmental and economic technical evaluations of an energetic system. This article presents the basic development of the concepts referenced from the Zero Law of the Thermodynamic, illustrating with examples the advantages to incorporate them as valuation and comparison parameters
[en] This work investigates the techniques used in evaluating distillation structures from lean manufacturing point of view. Oil and gas industry has already started adopting lean manufacturing principles in different types of processes from information flow to processing technologies. Generally, energy costs are the most important factors in processing hydrocarbons. Introducing flexibility desired by lean principles to the system may conflict energy efficiency of the system. However, this does not mean that the economic optimum is the energetic optimum. Therefore all possible changes due to temporarily stopped or not fully utilised plants have to be investigated, resulting in a large amount of cases that have to be evaluated. For evaluation exergy analysis can be used as it involves all energy types, and evaluation is straightforward. In this paper plain distillation structures are investigated, and the boundaries of the systems are set up according to the status of the site. Four component case studies are presented that show that the very same distillation structure can be more or less efficient depending on the status of the industrial site. It is also shown that exergy analysis used with different boundaries on the same system can show flexibility of the system and reveals potentials. - Highlights: • The article focuses on the flexibility aspect of lean manufacturing. • Exergy analysis of distillation scheme alternatives, energy efficiency. • Different boundaries define different scenarios of the same system is investigated. • The energy efficiency of distillation schemes also depends on their operating mode. • The exergy reserves of a distillation system can be revealed with exergy analysis
[en] The purpose of this work is to apply the useful energy and exergy analysis models for different modes of transport in Malaysia and to compare the result with a few countries. In this paper, energy and exergy efficiencies of the various sub-sectors are presented by considering the energy and exergy flows from 1995 to 2003. Respective flow diagrams to find the overall energy and exergy efficiencies of Malaysian transportation sector are also presented. The estimated overall energy efficiency ranges from 22.74% (1999) to 22.98% (1998) with a mean of 22.82+/-0.06% and that of overall exergy efficiency ranges from 22.44% (2000) to 22.82% (1998) with a mean of 22.55+/-0.12%. The results are compared with respect to present energy and exergy efficiencies in each sub-sector. The transportation sector used about 40% of the total energy consumed in 2002. Therefore, it is important to identify the energy and exergy flows and the pertinent losses. The road sub-sector has appeared to be the most efficient one compared to the air and marine sub-sectors. Also found that the energy and exergy efficiencies of Malaysian transportation sector are lower than that of Turkey but higher than Norway
[en] This paper presents an energy and exergy analysis of a domestic refrigeration system using R1234yf as a drop-in replacement for R134a. We base our analysis on a series of independent tests using two refrigerants, namely R1234yf and R134a. The test equipment consists of a fully instrumented domestic refrigeration system. A computational model is developed to work out the thermodynamic parameters such as coefficient of performance, exergy destruction ratio, exergy-based rational efficiency, component efficiency defect as well as the dimensionless exergy balance for both refrigerants. The parameters varied in the analysis were the evaporator and condenser temperatures as well as the amount of refrigerant used in the system. The results indicate that irreversibilities are mainly concentrated in the compressor, this is the case both for R1234yf and R134a. This exergy analysis proposed for evaluation of refrigerants in domestic refrigerators permitted to determine that R1234yf may not be a likely alternative to R134a. - Highlights: • An energy and exergy study of R1234yf as a drop-in replacement for R134a is presented. • A domestic refrigerator was fully instrumented. • The analysis takes into account the variation of charge of R1234yf compared with R134a. • The condenser temperature has a greater effect on the performance of refrigerator. • R1234yf is not a better alternative to R134a under the conditions assumed in this work.