Extended Exergy Accounting Research Articles

Extended Exergy Accounting as a general method for assessing the primary resource consumption of social and industrial systems

The method of Extended Exergy Accounting (EEA) is proposed as a paradigm for the evaluation of the equivalent primary resource consumption of 'Energy Systems'. In a 'system's approach', an energy system is an assembly of components that feed on primary energy sources to produce material or immaterial commodities.

Exergy and extended exergy accounting of very large complex systems with an application to the province of Siena, Italy

This paper describes the application of exergy and extended exergy analyses to large complex systems. The system to be analysed is assumed to be at steady state, and the input and output fluxes of matter and energy are expressed in units of exergy. Human societies of any reasonable extent are indeed Very Large Complex Systems and can be represented as interconnected networks of N elementary “components”, their Subsystems; the detail of the disaggregation depends on the type and quality of the available data. The structural connectivity of the “model” of the System must correctly describe the interactions of each mass or energy flow with each sector of the society: since it is seldom the case that all of these fluxes are available in detail, some preliminary mass- and energy balances must be completed and constitute in fact a part of the initial assumptions. Exergy accounting converts the total amount of resources inflow into their equivalent exergetic form with the help of a table of “raw exergy data” available in the literature. The quantification of each flow on a homogeneous exergetic basis paves the way to the evaluation of the efficiency of each energy and mass transfer between the N sectors and makes it possible to quantify the irreversible losses and identify their sources. The advantage of the EEA, compared to a classical exergy accounting, is the inclusion in the system balance of the exergetic equivalents of three additional “Production Factors”: human Labour, Capital and Environmental Remediation costs. EEA has an additional advantage: it allows for the calculation of the efficiency of the domestic sector (impossible to evaluate with any other energy- or exergy-based method) by considering the working hours as its product. As implied in the title, an application of the method was made to a model of the province of Siena (on a year 2000 database): the results show that the sectors of this Province have values of efficiency close to the Italian average, with the exception of the commercial and energy conversion sectors that are more efficient, in agreement with the rather peculiar socio-economic situation of the Province. The largest inefficiency is found to be in the transportation sector, which has an efficiency lower then 30% in EEA and lower than 10% in classical exergy accounting.

Performance of the Dutch Energy Sector based on energy, exergy and Extended Exergy Accounting

The performance of the Dutch Energy Sector is analyzed using the Standard Exergy Analysis as well as Extended Exergy Accounting (EEA) method. Performance indicators based on energy, exergy and cumulative exergy consumption (CExC) are evaluated for three subsectors: exploitation, transformation, and distribution of energy. It is shown that performance indicators based on CExC are much lower than those based on energy and exergy concepts. The EEA method is applied for analysis of four branches: cokeries and refineries, refineries, central electricity production, and distribution and decentral electricity production. The EEA method originally proposed by Sciubba is modified by evaluating the cost-to-exergy conversion factor from the monetary value and CExC of the feedstock. It was found that the monetary equivalent of extended exergy is higher than the respective product sales. Finally, it is shown that performance indicators of selected energy branches based on extended exergy are much lower than those based on the CExC.

Exergo-economics: thermodynamic foundation for a more rational resource use

This is a broad and comprehensive review of the development of the concept of exergy and of its application to the analysis and optimization of energy conversion systems. After a brief recapitulation of the basic concepts and a short historical outline, Second-Law Analysis, Thermo-Economics and Exergo-Economics are discussed. In conclusion, an original method developed by the author (Extended Exergy Accounting) is presented and discussed. Copyright © 2005 John Wiley & Sons, Ltd.

Emergy and exergy analyses: Complementary methods or irreducible ideological options?

The paper discusses the similarities and the incompatibilities between two forms of Energy Analysis (exergy and emergy, ‘EXA’ and ‘EMA’ in the following), both of which try to represent the behavior of physical systems by means of cumulative energy input/output methods that result in a double integration over space and time domains. Theoretical background, definitions and balance algebra are discussed first, in a ‘statement–counterstatement’ format that helps pinpointing differences and similarities. A significant, albeit simplified, benchmark case (ethanol production from corn) is used to compare the results and analytically assess the merits of each approach as well as possible synergic aspects. Corn production, transport and industrial conversion to ethanol are included in the analysis. First, mass balance and energy accounting are performed in each step of the process, then, exergy and emergy evaluations are carried out separately to lead to a set of performance indicators, the meaning of which is discussed with reference to their proper scale of application. The Authors underline that each method has its own preferred field of application and conclude that the two approaches appear to be characterized not much as different (and therefore competing) tools, but as different paradigms, whose meta-levels (their ‘philosophies’) substantially differ. In particular, EXA is found to provide the most correct and insightful assessment of thermodynamic features of any process and to offer a clear quantitative indication of both the irreversibilities and the degree of matching between the used resources and the end-use material or energy flows. EXA combined with costing considerations results in Thermo-Economics (TE), presently the best engineering method for System optimization. One of EXA recent extensions, Extended Exergy Accounting (EEA) includes all externalities in the exergy resource accounting, thus providing a more complete picture of how a process is interacting with its socio-economical environment and with the Biosphere. EMA further expands the evaluation to the larger scale of the Biosphere and properly accounts for the globality of the energy and resource flows supporting complex living systems. Although some conceptual assumptions and methodological differences appear irreconcilable, important similarities are also found that may lead to further methodological and practical convergences. Note: Although a significant confrontation and debate accompanied the development of this paper, contrasting opinions about important features of the two approaches still exist. Therefore, SU takes full responsibility of statements in Sections 2, 4.1, 6.2, 7.1 while ES takes full responsibility of statements in Sections 3, 4.2, 6.1, 7.2. All remaining Sections reflect points of view agreed upon by both Authors.

From Engineering Economics to Extended Exergy Accounting: A Possible Path from Monetary to Resource‐Based Costing

The article describes the extended exergy accounting technique (EEA), a novel method for computing the cost of a commodity based on its resource‐base equivalent value (as opposed to its monetary cost) that enables the analyst to perform more complete and meaningful assessments of a complex system. The claim made here is that the novelty, as well as the decisive advantage, of EEA consists in its being entirely and uniformly resource based, thanks to the inclusion in the system balance of exergetic fluxes equivalent to labor, capital, and environmental remediation costs. In this respect, EEA owes some of its structural formalism to Sraffa's network representation of the economic production of commodities by means of other commodities, which it extends by accounting for the unavoidable energy dissipation in the productive chain (whose economic implications were first discussed by Georgescu‐Roegen), to Daly's pioneering work in resource‐oriented economics, and to Szargut's cumulative exergy consumption method.The representation of a process by means of its extended exergy flow diagram is discussed in this article, and it is argued that some of the issues that are difficult to address with a purely monetary approach can be properly resolved by EEA. The main shortcomings of EEA are its intrinsic locality in time and space: They are demonstrated to be necessary and not casual consequences of its very definition and of the nonuniformity of societal conditions. In the conclusions, some indications are given as to the possibility of using this new technique to complement (and extend) other current tools, such as life‐cycle assessment or environmental footprint analysis.

Energy, exergy, and extended-exergy analysis of the Norwegian society 2000

The extraction, conversion, and use of energy carriers and materials in the Norwegian society in 2000 were investigated by Sciubba's method of extended-exergy accounting (EEA). In this method, extended-exergy (EE) values are assigned to labor and capital fluxes in addition to thermomechanical and chemical exergy values. The interchange of resources and products was quantified in terms of energy and exergy between seven sectors of the society and between the sectors and other countries. The extraction of resources from the environment and the discharge and deposit of waste were also included in the analysis. In the extraction sector, the exergy and EE conversion efficiencies both were 95%, and in the conversion sector both were approximately 76%. These two sectors are, respectively, dominated by oil and gas extraction and hydropower conversion. The third sector—agriculture, forestry, the fisheries, and food industry—had a lower exergy output to input ratio, 45%, whereas the EE conversion efficiency was 62%. A fourth sector, manufacturing industry, was dominated by paper, metal, and also chemical industry, and the efficiencies were 50 and 69%, respectively. In the transportation and service sectors, the labor and capital fluxes dominated the EEA, giving EE efficiencies of 63 and 75%, respectively, whereas the exergy efficiencies were 19 and 26%, respectively. In the seventh sector, the domestic sector (i.e. households), there was a close to zero energy and exergy output in this approach, since no products or resources were transferred to the other sectors except waste for re-circulation. However, the EE output of this sector was greater than the input, since labor is supplied from this sector to the other sectors.

Exergy-based lumped simulation of complex systems: An interactive analysis tool

The paper describes an application of a computational tool developed for the extended exergy accounting (EEA) of complex systems. The application is presented in an interactive graphic form to enhance its impact on the user. The computational part is based on a modular process simulator, originally devised to compute the mass- and energy balances and the exergy accounting of energy conversion systems: the modularity of the code suggested its extension to the analysis of complex energy systems. The main characteristics of the package are its extensive modularity and its ability to handle a wide spectrum of system configurations. The code identifies a system by means of an interconnection matrix, which represents the structural connectivity of the society under examination (i.e. which describes in a synthetic way the interactions of each mass- or energy flux with each sector of that society), and assembles the system of balance equations according to an original protocol. In steady-state simulations, as the one presented here, the code is capable of assembling the proper balance equations starting from the information about an ‘initial state’ of the system, specified by the user together with all necessary constraints. The extension to unsteady operation is not foreseen at the moment. The level of aggregation, the relevant input data and boundary conditions must be assigned by the user, and are scrutinised by the code for internal consistence. Except for this preliminary check, and for the mass- and energy balances at ‘run’ time, the procedure is entirely acritical about the input data, thus allowing a very broad range of sensitivity studies. The total amount of the resources entering the control volume must be assigned, either directly in exergetic form, or otherwise by means of mass- and specific energy flow rate values: the code executes a simple screening on the input data and computes the exergetic value of the incoming flows with the help of a table of ‘raw exergy data’ available in one of its libraries. Energy- and exergy balances are performed independently: the package generates energy-, exergy- and extended exergy ‘balances’. Irreversible losses are computed separately for each component of the system. The advantage of EEA consists in the inclusion in the system balance of the exergetic equivalent of human work (labour), of capital and of environmental remediation costs. As an application, a series of simulations have been performed on the ‘System Italy’ (on a 1996 database).

04/01156 Extended exergy accounting applied to energy recovery from waste: The concept of total recycling: Sciubba, E. Energy, 2003, 28, (13), 1315–1334

04/01156 Extended exergy accounting applied to energy recovery from waste: The concept of total recycling: Sciubba, E. Energy, 2003, 28, (13), 1315–1334

Extended exergy accounting applied to energy recovery from waste: The concept of total recycling

A novel systematic approach to the evaluation of energy conversion processes and systems, based on an extended representation of their exergy flow diagram is presented and discussed in this article. The method constitutes a substantial generalisation of Szargut’s cumulative exergy consumption procedure, and provides a coherent and consistent framework for including non-energetic quantities like capital, labour and environmental impact into an engineering optimisation procedure (the apposition ‘extended’ refers to these enhanced capabilities). It is argued that some of the issues that are difficult to address with a purely monetary or even with a thermo-economic approach can be resolved in a straightforward manner by extended exergy accounting (‘EEA’ in this article). As an indication of the potential of the method, a general, qualitative example is offered of the application of EEA to the evaluation of a technical alternative between a non-integrated waste recycling and an integrated waste recycling and incineration facility.

Cost analysis of energy conversion systems via a novel resource-based quantifier

The paper presents a new formalism for the costing of production chains, with special emphasis on energy conversion systems. From a mathematical point of view, this method can be described as a standard Leontiev-type input-output technique, in the formulation commonly adopted by most costing theories, including Thermoeconomics. Any complex production chain can be decomposed into modules, to each one of which mass and energy balances are applied. The resulting flow diagram is then examined from an exergetic point of view, and a cost analysis is performed. The costing paradigm is the novel feature here: rather than monetary units, a resource-based quantifier, called “extended exergy”, is employed. It is argued that both labour and financial costs can be properly linked to an equivalent resource consumption through a back-to-resource accounting procedure that expresses the total exergy consumption required to “generate” one man-hour of work or one monetary unit of currency circulation. Environmental remediation costs are similarly taken into account by computing the equivalent cumulative exergy expenditures required to achieve zero impact. It is argued, and discussed on the basis of an example of application to a cogeneration plant, that the new technique, called Extended Exergy Accounting (EEA), is a substantial improvement with respect to current engineering economic techniques, including Thermoeconomics. It is shown that EEA calculates the real, resource-based “value” of a commodity (which is not necessarily equal to its monetary cost) thus enabling Analysts and Energy Planners to perform a more complete and meaningful assessment of an Engineering Complex System. The decisive advantage of EEA consists in its being entirely and uniformly resource-based: in this respect, it owes some of its structural formalism both to the economic theory of production of commodities, which it extends by accounting for the unavoidable energy dissipation in the productive chain, and to resource-oriented economics. It must be acknowledged as well that EEA follows a path originally proposed by Szargut in his “Cumulative Exergy Consumption” method, which it extends by providing a rational and uniform treatment for all non-externalities.

Beyond thermoeconomics? The concept of Extended Exergy Accounting and its application to the analysis and design of thermal systems

This paper presents a novel approach to the evaluation of energy conversion processes and systems, based on an extended representation of their exergy flow diagram. This approach is a systematic attempt to integrate into a unified coherent formalism both Cumulative Exergy Consumption and Thermo-economic methods, and constitutes a generalisation of both, in that its framework allows for a direct quantitative comparison of non-energetic quantities like labour and environmental impact (hence the apposition ‘Extended’). A critical examination of the existing state-of-the-art of energy- and exergy analysis methods and paradigms indicates that an extension of the existing ‘Design and Optimisation’ procedures to include explicitly ‘non-energetic externalities’ is indeed feasible. It appears that it can indeed be successfully argued that some of the issues that are difficult to address with a purely monetary theory of value can be resolved by Extended Exergy Accounting (‘EEA’ in the following) methods without introducing arbitrary assumptions external to the theory. In this respect, EEA can be regarded as a natural development of the economic theory of production of commodities, which it extends by properly accounting for the unavoidable energy dissipation in the productive chain. While a systematic description of the EEA theory is discussed in previous work by the same author, the present paper aims at a more specific target, and presents a formal representation of the application of EEA to a cogenerating plant based on a gas turbine process. It is shown that the solution indeed leads to an ‘optimal’ design, and that its formalism embeds even extended Thermo-economic formulations.