Extended Exergy Research Articles

Do the Different Exergy Accounting Methodologies Provide Consistent or Contradictory Results? A Case Study with the Portuguese Agricultural, Forestry and Fisheries Sector

Three exergy accounting approaches are used to evaluate exergy efficiency: the Energy Resources Exergy Accounting (EREA), the Natural Resources’ Exergy Accounting (NREA) and the Extended Exergy Accounting (EEA). To test the consistency of the results provided by these methodologies, we apply them to evaluate the Portuguese agricultural, forestry and fisheries (AFF) sector, from 2000 to 2012. EREA shows an increase of 30% in the efficiency of the Portuguese AFF sector, while NREA and EEA methodologies increases of 27% and 43%, respectively. Although the results are consistent for the AFF sector, the same does not happen in the fisheries subsector, whose exergetic efficiency increases 14% with the EREA but decreases 42% with the NREA approach. The ratio of output to useful exergy reveals that a better thermodynamic efficiency is not translated into a higher energy service efficiency because fishing vessels have to travel more to get the same fish. Thus, results provided by the EREA and NREA approaches are complementary and both are needed to provide a realistic picture of exergy efficiency. On the other hand, results obtained by the EEA approach are dominated by capital and environmental impacts, revealing the disproportionality between material and immaterial inputs in this methodology.

Spatial differences of exergy use of cement manufacturing industry in China based on extended exergy accounting method

Factory-level data from 23 provinces and some national statistical data in cement manufacturing industry and socio-economies in 2012 are used to analyze the spatial distribution of exergy use for China’s cement manufacturing industry by the Extended Exergy Accounting method. This method takes full account of the inclusion of energy and raw material supply and other external factors (capital, labor and environment) into a comprehensive resource cost assessment. The extended exergy consumption and its intensity quantitatively at the provincial levels of cement production were calculated and then the agglomeration level of exergy use at the regional level was also evaluated. Based on this analysis, their spatial difference in size and efficiency of exergy use at the provincial level were identified. Moreover, their regional characteristics were revealed. Some important results could be drawn as follows. First, the invisible social cost accounted for 1/10 of the total exergy use in cement manufacturing industry, while the energy element shared about 9/10. Second, the gross distribution of exergy use in China’s cement manufacturing industry was mainly concentrated in the eastern region like Anhui and Shandong provinces, and in the western region like Sichuan province. In terms of exergy use, the coal and electricity were the highest of energy costs in the eastern region, whereas the cost of capital, labor and external environmental factors highlighted the invisible social cost for cement production in the central and western regions to some extent. Third, the efficiency distribution of exergy use in China’s cement manufacturing industry illustrated an incremental feature from west to east, especially for the energy, labor and capital efficiencies. An evaluation on the environmental efficiency indicated that provinces or regions like Tibet, Xinjiang, Inner Mongolia and Shanxi have undertaken much higher environmental costs. Fourth, the 23 provinces could be classified into eight groups by the Euclidean distance model using the gross and efficiency results of exergy use. Fifth, the high industry concentration degree is the main driving factor of exergy efficiency improvement for cement manufacturing industry in China.

An exergy-based approach to the joint economic and environmental impact assessment of possible photovoltaic scenarios: A case study at a regional level in Italy

Most energy conversion systems, and especially electricity generation plants, do not operate at nominal conditions throughout their useful life: periodic, semi-periodic and stochastic changes in the availability of the resource affect solar (thermal and PV), wind, hydraulic, and geothermal plants, which in reality operate at off-design conditions for most of their life. To a smaller extent, fossil-fuelled plants may also be plagued by fuel availability problems and no longer easily predictable demand oscillation. In spite of the ever growing net connectivity, since the demand curve in even larger geographic regions displays a typical quasi-sinusoidal shape, fleet load modulation is unavoidable. Naturally, off-design operation and load cycling affect the cost of the generated kWh.This paper presents a general thermoeconomic method to evaluate the economic and environmental effects of energy system integration, taking into account life cycle concerns (supply chains) and the effect of inefficiencies due to off-design operation of the systems. The method here is applied to a realistic case study of an Italian regional utility: an analysis of the implications of the variation of the productive mix between a photovoltaic power plant (PV) and a standard commercial, non-cogenerating gas turbine plant (GT) on the final cost of the electrical kWh. The demand curve is prescribed, and the effect of different mixes is assessed, both on the monetary and on the exergy cost of the electricity.The economic cost assessment is performed by standard thermoeconomic techniques, whereas the exergy costs are evaluated using both the Extended Exergy Accounting (EEA) and the Thermo-Ecological Cost (TEC) methods. The results show that a purely monetary cash flow accounting and thermo-economics lead to contrasting results, and also that the EEA and TEC cost indicators generate different rankings among the studied alternative GT/PV mixes.

Ecological accounting based on extended exergy: a sustainability perspective.

The excessive energy consumption, environmental pollution, and ecological destruction problems have gradually become huge obstacles for the development of societal-economic-natural complex ecosystems. Regarding the national ecological-economic system, how to make explicit the resource accounting, diagnose the resource conversion, and measure the disturbance of environmental emissions to the systems are the fundamental basis of sustainable development and coordinated management. This paper presents an extended exergy (EE) accounting including the material exergy and exergy equivalent of externalities consideration in a systematic process from production to consumption, and China in 2010 is chosen as a case study to foster an in-depth understanding of the conflict between high-speed development and the available resources. The whole society is decomposed into seven sectors (i.e., Agriculture, Extraction, Conversion, Industry, Transportation, Tertiary, and Domestic sectors) according to their distinct characteristics. An adaptive EE accounting database, which incorporates traditional energy, renewable energy, mineral element, and other natural resources as well as resource-based secondary products, is constructed on the basis of the internal flows in the system. In addition, the environmental emission accounting has been adjusted to calculate the externalities-equivalent exergy. The results show that the EE value for the year 2010 in China was 1.80 × 10(14) MJ, which is greatly increased. Furthermore, an EE-based sustainability indices system has been established to provide an epitomized exploration for evaluating the performance of flows and storages with the system from a sustainability perspective. The value of the EE-based sustainability indicator was calculated to be 0.23, much lower than the critical value of 1, implying that China is still developing in the stages of high energy consumption and a low sustainability level.

The Economic Order Quantity model revisited: an Extended Exergy Accounting approach

The Economic Order Quantity, EOQ, model has been popular among academicians and practitioners for decades. Despite the many variants of the EOQ that have appeared in the literature to fine-tune it to reality, it still has limitations. A major one is that it does not take into account the hidden costs inherent in inventory systems. Some of these costs relate to sustainability issues including environmental, social labor, and economic effects.This paper considers some of these costs, referred to as the exergetic costs, and estimates them using the Extended Exergy Accounting, EEA, approach. Extended Exergy Accounting assigns equivalent exergetic values to capital, labor and environmental remediation costs of a system. The analysis combines the classical exergy analysis with the sustainability factors, which are the labor, capital and environment. The paper uses an exergetic model to determine the EOQ inventory policies for three firms operating in the USA, Germany and China. The results show that the EOQ is different for the three firms because the equivalent exergy of capital, labor and environment remediation costs is different in each country.

Advances in exergy analysis: a novel assessment of the Extended Exergy Accounting method

ObjectiveThis paper presents a theoretical reassessment of the Extended Exergy Accounting method (EEA in the following), a comprehensive exergy-based analytical paradigm for the evaluation of the total equivalent primary resource consumption in a generic system.Our intent in this paper was to rigorously review the EEA theory and to highlight its double “valence” as a resource quantifier and to clarify its operative potential. On the one side, EEA can be properly regarded as a general “costing” theory based on a proper knowledge of the cumulative exergy consumption of different supply chains, economic systems and labour market: it is indeed the only method that translates externalities (capital, labour and environmental remediation) into cumulative exergetic costs and thus allows for their rigorous inclusion in a comprehensive resource cost assessment. Indeed, the extended exergy cost eec reflects both the thermodynamic “efficiency” of the production chain and the “hidden” resource costs for the society as a whole.From another, perhaps even more innovative, perspective, EEA can be viewed as a space and time dependent methodology since economic and labour costs can only be included in the Extended Exergy balance via their exergy equivalents (via two rigorously defined postulates). Since the equivalent exergy cost of the externalities depends both on the type of society and on the time window of the analysis, the extended exergy cost eec reflects in a very real sense both the thermodynamic “efficiency” of the machinery and the “conversion efficiency” of the specific society within which the analysis is performed.We argue that these two intrinsic features of the EEA method provide both additional insight in and more relevant information for every comparative analysis of energy conversion systems, both at a global and a local level.In the paper, traditional and advanced exergy analysis methods are briefly discussed and EEA theoretical foundations and details for its application are described in detail. MethodsThe method converts not only material and energy flows, but externalities as well (labour, capital and environmental costs) into flows of equivalent primary exergy, so that all exchanges between the system and the environment can be completely accounted for on a rigorous thermodynamic basis.The current emphasis decision makers and by public opinion alike seem to be placing on sustainability generates the need for continue research in the field of systems analysis, and a preliminary review confirms that exergy may constitute a coherent and rational basis for developing global and local analysis methods. Moreover, extended exergy accounting possesses some specific and peculiar characteristics that make it more suitable for life-cycle and cradle-to-grave (or well-to-wheel) applications. ResultsTaxonomy for the classification of exergy-based methods is proposed.A novel assessment of the EEA method is provided, its advantages and drawbacks are discussed and areas in need of further theoretical investigation are identified. ConclusionsSince EEA is a life-cycle method, it is argued that it represents an improvement with regard to other current methods, in that it provides additional insight into the phenomenological aspects of any “energy conversion chain”. The paper demonstrates that the Extended Exergy cost function can be used within the traditional and very well formalized Thermoeconomic framework, replacing the economic cost function in order to evaluate and optimize the consumption of resources of a system in a more complete and rational way. Practical implicationsThis paper contains some specific proposals as to the further development of the EEA method, to increase its effectiveness and to improve its practical applicability for system analysis. Suggestions are made on how to include an EEA discussion in the current debate about sustainable development.

On the vorticity and energy budgets of the cold vortex in Northeast China: a case study

This study examines the vorticity budgets, turbulent extended exergy and kinetic energy evolution equations to investigate the major dynamical and energy conversion processes contributing to the initiation and intensification of the cold vortex over Northeast China that occurred during June 19–22, 2009. The results show that the cyclonic vorticity was initiated in the lower troposphere due to the intense convergence of horizontal winds. The growth of cyclonic vorticity in the middle troposphere is mainly due to the vertical transportation of the vorticity, yet the increase of cyclonic vorticity in the upper troposphere primarily results from the horizontal advection of vorticity. Of special interest in this study is the evaluation of the role of thermal advections in the baroclinic development of the cold vortex. The results indicate that the rising of the air over relatively warm areas and the sinking of the air in relatively cold regions are favorable for releasing turbulent extended exergy \( \left( {e_{\text{t}} } \right) \), which is later converted to turbulent kinetic energy \( \left( {k_{\text{t}} } \right) \), and this process occurs during the initiation and intensification of the cold vortex. In addition, barotropic energy conversion is another important process that contributes to the growth of kt, and it strengthens gradually after the initiation of the cold vortex. Other than frictional consumption, the flux of kt in the vertical direction also depletes some of kt. The fluxes of et, baroclinic energy conversions and diabatic generations are favorable factors for the growth of et, whereas it decreases with time as a result of a large amount of et that is released. Most of the energy conversion processes, including the baroclinic and the barotropic energy transformations and the energy conversions from et to kt, as well as the fluxes of et, are stronger in the lower troposphere than the other areas during the formation of the cold vortex. This accounts for the initiation of the cyclonic vorticity in the lower troposphere. Finally, the fact that the turbulent extended exergy releases primarily in the middle troposphere through the vertical thermal circulation is consistent with our understanding based on the vorticity budget analyses.

Extended exergy analysis of Turkish transportation sector

This work presents an analysis of the different modes of the Turkish transportation sector along the guidelines of the Extended Exergy Accounting (EEA) method. The results refer to year 2006 because that was the most complete and sufficiently disaggregated database available. The evaluation of the transportation sector leads to the calculation of its extended exergetic efficiency (EEAeff) and requires the inclusion of all commercial and private transportation services (passengers and goods) as well as of all services directly related to transportation (post, cargo, pipeline transport, etc.). The environmental remediation costs (EEEnv) of sectoral solid waste and gas emissions (direct and indirect) are obtained in accordance with the original calculation procedure, without recurring to the conversion of monetary into exergetic costs. The resulting EEAeff of the sector is 0.36, which is rather low (in the EE sense), because of the sector’s largely unsustainable structure: fossil-fuelled road transportation widely prevails, which not only destroys a very high percentage of the incoming exergy, but is also affected by quite large CO2-equivalent emissions that demand for a high EEEnv.

Extended exergy accounting applied to the flaring practice in oil fields

An original procedure based on the Extended Exergy Accounting method is described and implemented in this paper. The goal is the quantification of the environmental externality linked to the chemical pollutants released by an elevated flare stack (SOx and NOx). The extended exergy calculations provide a measure of both the exergy flux released into the environment by the stack and its 'cost' in primary resource equivalents. Idealised processes are assumed for the effluent treatment, but nevertheless, it is shown that the inclusion of the environmental externality bears a non–negligible influence on the final resource cost. As a further example of application, it is shown that both the environmental damage and the product costs can be reduced if hot gas recycling is enforced.

A revised calculation of the econometric factors α- and β for the Extended Exergy Accounting method

Extended Exergy Accounting (“EEA”) is a method to compute the space- and time integral of the primary exergy required to produce a good or a service: the extended exergy of a commodity measures its “embodied exergy”, including externalities (Labour, Capital and Environmental Costa). A crucial point of the method is the calculation of two econometric coefficients, commonly referred to as “ α” and “ β”,used to calculate the extended exergy equivalents of Labour and Capital respectively. In previous applications of the EEA method, these coefficients have been assigned approximate values estimated on the basis of global system considerations. In this paper, a novel procedure is described that leads to the calculation of “exact” values of both econometric coefficients, based on detailed exergy- and monetary balances of the Society to which the EEA is applied. It is shown that both α and β depend in a non-trivial way from the consumption patterns, the technological level and the life- and socio-economic standards of each Country. It is also shown that the values are substantially different for developed (OECD) and underdeveloped Countries, and representative samples of values are calculated and critically analysed. On the basis of these new model coefficients, the specific exergy equivalents of Labour (ee L) and of Capital (ee K) are calculated, and shown to differ from the values used in previous EEA calculations.

Correlations and complementarities in data and methods through Principal Components Analysis (PCA) applied to the results of the SPIn-Eco Project

This paper demonstrates how the results from different methods can be interpreted on the basis of a statistical approach that can help find new hints in the evaluation of sustainability at the territorial level. The SPIn-Eco Project for the Province of Siena (Italy) is an example of an environmental sustainability assessment of an area using methods that are suitable for a large system: Ecological Footprint, Greenhouse Gas Inventory, Extended Exergy Analysis, Emergy Evaluation, and Remote Sensing. The calculation of many indicators, derived from these methods, has prompted us to use a statistical method (Principal Components Analysis, PCA) to understand the degree of similarity/congruence of the indicators (here we have examined 26 of them) and the possibility of recognizing patterns or clusters in the description of the 36 municipalities that compose the Province of Siena. Among the results, unexpectedly, emergy flow and the Ecological Footprint resulted as being completely uncorrelated, apparently due to the importance that the non-renewable part of the emergy holds in the evaluation. The municipalities of the province are considerably spread out over the graphs, even though that of Siena is quite far from the rest along the first dimension. In addition, we were able to distinguish between more homogeneous districts (sets of municipalities), such as Val di Merse and Val d’Orcia, and very diverse ones, such as Val d’Elsa and Val di Chiana.

Integrating methods for the environmental sustainability: The SPIn-Eco Project in the Province of Siena (Italy)

This paper shows how different methods can be integrated in order to provide an organic evaluation of the environmental sustainability at the territorial level. A territory is a complex, dynamic and open system where a population develops, uses resources, produces goods and services, consumes, depletes and finally obtains economic results. All these elements characterise human behaviour, which can be monitored, measured and compared to the capacity of the environment to sustain it in the long run. The SPIn-Eco Project for the Province of Siena (Italy) is described as an example of an environmental sustainability assessment of an area, and its methods (Ecological Footprint, Greenhouse Gas Inventory, Extended Exergy Analysis, Emergy Evaluation, Life Cycle Assessment (LCA) and Remote Sensing) are briefly introduced. This Project has been proposed and funded by the most important provincial administrative and financial institutions in the territory (the Administration of the Province of Siena and the Monte dei Paschi Foundation, respectively), and was designed and realised in 4 years (2001–2004) by a research team coordinated by the University of Siena.

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.

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

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.

Local Energetics of an Idealized Baroclinic Wave Using Extended Exergy

The concept of local extended exergy is here applied to an idealized, dry, and reversible-adiabatic cyclone development. The extended exergy as well as the kinetic energy are decomposed into a mean part, defined by a zonal average, and into a perturbation from the mean. The resulting local energy evolution equations provide an extension of the well-known Lorenz-type available energy equations. A term in the baroclinic conversion rate, connected with static stability anomalies, which is not usually considered, is of significance even in this idealized case study and contributes significantly to the nonlinear equilibration of the baroclinic wave.

Use of extended exergy analysis to evaluate the environmental performance of machining processes

Traditional applications of exergy analysis have focused upon the optimization of energy use in thermal and chemical processes. This paper introduces a form of exergy analysis in which the methodology is extended to consider the characteristics of material flows in a process as well. This new form of analysis, termed extended exergy analysis (EEA), is shown to be particularly useful in valuating the environmental performance of industrial processes. EEA differs from traditional theory in its requirement that all ground states be defined such that they are en6ironmentally acceptable. Environmental acceptability can be determined using a number of health, occupational and ecological criteria. By integrating biological considerations into the existing physical definition, EEA provides manufacturers and regulators alike with relevant information regarding the costs of achieving environmentally benign production. These costs are valued consistently for both raw material and energy inputs and product and residual outputs, affording degrees of transparency and objectivity not present in other valuation methodologies. Application of the technique to a case study involving the machining of aluminium is developed.