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A heat exchanger was integrated to increase the efficiency of a geothermal double flash cycle and decrease the liquid content at a low-pressure turbine outlet. The liquid cooling (LC) and liquid splitting technologies have three different configurations: i.) steam superheating (SH), ii.) steam reheating (RH) and iii.) mixture heating (MH) was implemented. An exergoeconomic analysis was applied to the systems and analyzed using geothermal power plant operation parameters. An increase in the net power of the double flash cycle of 418.6 kW was achieved with LC-SH configuration, 5008.6 kW with LC-RH, 5248.6 kW with LC-MH, 3758.61 kW with LS-RH and 3958.61 with LS-MH. The power of the low-pressure turbine also increased compared to the double flash design in a 0.5236% (SH), 5.48%(RH), and 5.72%(MH), and the produced electricity cost were 5.9963 $ USD/GJ, 5.9976 $ USD/GJ, 6.0089 $ USD/GJ, 6.0086 $ USD/GJ, 5.9336 $ USD/GJ, 5.9482 $ USD/GJ and 5.9481 $ USD/GJ for the double flash, DF-LC-SH, DF-LC-RH, DF-LC-MH, DF-LS-SH, DF-LS-RH, and DF-LS-MH designs, respectively. The DF-LS-SH design is the most feasible because the cost of electricity produced is reduced while the steam quality of the low-pressure turbine and the net power of the geothermal plant increases. • Six modifications to a double flash cycle were analyzed from an exergoeconomic point of view. • The design of liquid splitting and superheating reduced the exergy cost to 5.9336 $ USD/GJ compared to the double-flash base case. • The liquid cooling technology with mixture heating improved the net power by 5331.61 kW. • The liquid content at the outlet of the low-pressure turbine was reduced by 5.54%. [ABSTRACT FROM AUTHOR]

Exergoeconomics has played an important role in the study of new energy systems in the last decades. The use of exergy as a "carrier of value" has made it possible to define an unambiguous criterion for allocating costs among energy systems products. The paper shows how exergoecomic procedures of analytical optimization and design improvement on heuristic basis have been progressively replaced by more efficient procedures aimed at minimizing an objective cost function, leaving exergoecomic cost evaluation as the final step. It also highlights how growing concerns about climate change and the continued growth of inequalities in energy availability have broadened the set of objectives in the search for the optimal integration of the design and operation of energy conversion units and network with intelligent methodologies to reduce energy demands. The objective of the article is twofold: i) present the evolution of the main Exergoeconomic methods and show how they have paved the way for Thermo-X Optimization methods; and ii) outline the path for developing a general model of society's entire energy system that includes a broader set of objectives and constraints in addition to economic ones to help build the energy system of the future with a more sustainable perspective. • It is shown how Exergoeconomic procedures paved the way to Thermo-X Optimizations. • The paper outlines the path towards a general model of society's entire energy system. • The need to avoid wastes to reduce energy demand in wealthier nations is stressed. [ABSTRACT FROM AUTHOR]

Exergy-based methods consist of at least an exergetic analysis, which can be combined with an economic analysis and a life cycle assessment in order to evaluate and improve energy-intensive processes. The author coined the term exergoeconomics in 1984 to replace the term thermoeconomics when exergy costing is used in the combination of an exergetic analysis with a cost analysis and to emphasize the role of exergy in the efforts to reduce the product cost. He also developed a general exergoeconomic methodology based on exergy-based variables and on appropriate definitions of the "product" and "fuel" for each component of an energy conversion system. These definitions and the application of exergoeconomics were generalized by A. Lazzaretto and the author in 2006 in an approach based on specific costs (SPECO approach). L. Meyer and the author coined the term exergoenvironmental analysis in 2009 for the combination of an exergy analysis with a life-cycle analysis when exergy is used to assign environmental impacts to streams. An exergoenvironmental analysis uses the methodological background of exergoeconomic methods. Starting in 2002, to reduce the limitations of the conventional exergy-based methods, and to facilitate system optimization, the author, and later in cooperation with T. Morosuk and co-workers at TU Berlin, developed the advanced exergy-based methods, which are based on the notion that the inefficiencies (exergy destruction and exergy loss), the costs, and the environmental impacts can be split into avoidable/unavoidable and endogenous/exogenous parts, to improve understanding of the formation process of inefficiencies, costs and environmental impacts within an energy conversion system. As often happens, after their introduction, all the above terms and methods have been misused and misinterpreted by some other authors. This paper briefly reviews past contributions by the author and some other exergy practitioners and discusses future developments. It concludes, that the advanced exergy-based methods need further development to be generalized, and integrated and to reduce their subjectivity in addition to the efforts and time required for their application. Development of appropriate software and shortcut methods will facilitate their use by researchers and engineers in industry and the application of exergy-based methods in energy-intensive industrial processes for multiobjective optimization purposes. • The most promising exergy-based methods are briefly reviewed. • Expected future developments are discussed. • More industrial applications are needed. • Misinterpretations and misuses of the methods limit their development. • The methods can be used to fairly apportion pollutants among countries. [ABSTRACT FROM AUTHOR]

Researchers have constantly been looking for renewable alternative fuels due to high fuel price volatility, energy security concerns, and produced harmful emissions. One of the promising alternatives is to produce biodiesel from waste economical feedstock such as chicken fat. Esterification and transesterification are used to create methyl ester from chicken fat. Then, 25%, 50%, 75%, and 100% of chicken oil biodiesel are volumetrically blended with diesel fuel. Diesel engine is loaded between 0% and 100% at 3000 rpm rated speed. Exergetic and exergoeconomic assessments of diesel engine fuelling with blends of chicken biodiesel were conducted in the present study. Diesel oil performed most efficiently in terms of exergy. For B100, the worst exergetic results are attained. The exergy efficiency of test engine at 75% engine load was 33.25% for the D100 and 27.85% for the B100. D100 produced the best exergoeconomic findings, while adding biodiesel to D100 made the exergoeconomic parameters worse. Crankshaft work had a particular exergy cost of 110.02 $/GJ for D100 and 194.37 $/GJ for B100 at 75% of engine output power. In the conclusion, it is noted that the waste chicken fat methyl ester can be used at low fractions as a substitute for traditional diesel fuel without modifying the engine, and this is a promising solution for waste management, turning waste products into an energy source, and dwindling fossil fuel reserves. • Biodiesel was produced with the following of esterification and transesterification methods. • Chicken fat biodiesel blends were tested in terms of exergy and exergoeconomics. • Theory of Exergetic Cost (TEC) was applied to discuss the performance comparison of the test fuels. • Chicken oil biodiesel fuels presented very competitive results in terms of performance indicators. • Exergy costs for crankshaft work for D100 and B100 were 110.02 and 197.37 $/GJ, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates different configurations of organic Rankine flash cycles combined with a Brayton cycle by performing thermodynamic, exergy, and exergoeconomic analyses. The thermal energy of the cycle is produced through burning gaseous methane generated via gasification of biomass. A systematic analysis of these configurations is conducted to enhance the exergy efficiency of the cycles. Additionally, the reutilization of the thermal energy that would otherwise be wasted in the Brayton cycle contributes to a notable enhancement in the overall thermal efficiency of the combined cycle. A range of working fluids, namely m-Xylene, o-Xylene, p-Xylene, toluene, and ethylbenzene are analyzed for the organic Rankine cycle. Predictions using an artificial neural network (radial base function) are also carried out. The results indicate that the p-Xylene increases exergy efficiency more than other working fluids. Further, the improved organic Rankine cycle mitigates exergy destruction by 10 %. Although applying double flash evaporators improves the exergy efficiency by 3 %, it increases the unit cost of power generated by more than 10 %. The application of a data-driven model to predict various configurations of combined organic Rankin cycle with a Brayton cycle fed by biomass has rarely been investigated. • The p-Xylene decreases the exergy destruction, considerably. • The ODFRC contained a higher unit cost of power produced. • In terms of higher investment cost, the cycles are ranked as ODFRC, SOFRC, and IOFRC. • Having higher thermal efficiency, the cycles are ranked as IOFRC, ODFRC, and SOFRC. • The precision of RBF-ANN for predictions of the studied cycles is confirmed. [ABSTRACT FROM AUTHOR]

Multi-Objective optimization of propane pre-cooled mixed refrigerant (C3MR) LNG process is performed with two objective functions: (a) maximizing the exergy efficiency and (b) minimizing the total cost of the product. The process simulation is developed using Aspen Plus, while the feasible solutions are produced using non-dominated sorting genetic algorithm II (NSGA-II). The results from exergy-based analysis revealed that when the exergetic efficiency is maximized, the total cost of product has increased from 5047$/h to 52776 $/h, with 71% of the investment costs come from precooling heat exchangers and main cryogenic heat exchangers. On the contrary, when the total cost of product is minimized, the total investment cost is reduced by 18% at the expense of exergetic efficiency. At the lowest cost of product, the total exergy destruction has increased to 111.4 MW or 38% higher compared with the case of maximization of exergetic efficiency. The optimization shows the range of Pareto feasible solutions are between 0.557 and 0.613 for exergetic efficiency and between 45600 and 52776 $/h for the total cost of product. This study demonstrates the approach to solve a multi-objective problem and to find Pareto front for an LNG process without imposing any weighted preferences to the objective functions. • Propane pre-cooled mixed refrigerant process are analyzed using exergy-based methods and optimized with genetic algorithm. • Multi-objective optimization is the combination of the exergy-based methods and non-dominated sorting genetic algorithm II. • Over 70% of the investment costs associated with pre-cooling heat exchangers and main cryogenic heat exchanger. • The total product cost minimization: the total investment cost is reduced by 18% while the exergetic efficiency decreased. • Pareto front for the two objective functions is shown at 100th generations. [ABSTRACT FROM AUTHOR]

Abstract Exergy-based methods are powerful tools for developing, evaluating, understanding, and improving energy conversion systems. This paper deals with integrated advanced exergy-based evaluations. In addition to conventional methods, advanced exergy-based analyses consider (a) the interactions among components of the overall system, and (b) the real potential for improving each important system component. The main role of an advanced analysis is to provide energy conversion system designers and operators with information useful for improving the design and operation of such systems. Splitting the exergy destruction, the capital investment cost, and the component-related environmental impact associated with each single component of an energy conversion system into endogenous/exogenous and avoidable/unavoidable parts and using a further splitting of the exogenous exergy destruction improves (a) our understanding of the processes that take place, and (b) the quality of the conclusions for improvement obtained from the analysis. This paper discusses the main features and some recent developments in the area of advanced exergy-based methods. Application of the method to a simple air refrigeration machine confirms the correctness of the approach. [ABSTRACT FROM AUTHOR]

Population explosion, depletion of fossil fuel and environmental regulations related to emission from power utilities has been challenging the utility developers to promote cost effective, fuel efficient and clean energy. This article focuses on comparative exergoeconomic study of gas turbine power utility and a combined cycle utility. By its very nature combined cycle includes more number of cycle components as compare to the basic gas turbine cycle and hence the investment cost for the combined cycle power plants is higher in terms of total cost rate. The present work also focuses on the advantages of developing combined cycle based power utility in comparison to gas turbine based utility in terms of its exergoeconomics. Exergoeconomic analysis of utilities based on each of these cycles has been carried out keeping the operating parameters constant i. e. (r pc = 10, TIT = 1500 K, η AC = 88% and η GT = 90%). Results obtained highlights that with 4.47% higher total cost rate, combined cycle develop 21% higher power output equivalent to 48.71 MW. Combined cycle based utility exhibits higher exergy efficiency in comparison to basic gas turbine based utility, with combined cycle delivering 21.16% higher exergy efficiency when the cost of electricity (3.32 cents/kWh) is marginally higher by 13.3%. [ABSTRACT FROM AUTHOR]

In power plant industry, it is always desirable that the performance of the plant should be as high as possible with the lowest possible investment. In this regard exergoeconomic analysis is a tool which combines thermodynamic analysis and economic principles to provide information that is helpful to predict thermodynamic performance and total cost of the plant. In this work an exergoeconomic approach is applied to the gas turbine based power plant cycles. In present work comparative exergoeconomic analysis of basic and reheat air-film blade cooled gas turbine cycles have been performed with exergy analysis as the basis. Average cost theory of exergoeconomic analysis has been carried out, in order to estimate the thermodynamic performance, thermoeconomics and electricity cost for power utility based on the cycle. Present work also represents the behavior of key parameters with cycle operating parameters (compressor pressure ratio and turbine inlet temperature) of proposed cycle. The comparative analysis result for base case (TIT = 1500 K, r pc = 26, η AC = 88 % , η GT = 90 % ) being total cost rate = 20.172 $/h and 29.156 $/h, plant specific work = 422.49 kJ/kg and 576.40 kJ/kg and cost of electricity = 3.31 cents/kWh and 3.45 cents/kWh for basic and reheat gas turbine cycle based power utility respectively. [ABSTRACT FROM AUTHOR]

Gas turbines usually suffer from remarkable drop in power and excessive increase in fuel consumption when running under part load or high ambient temperatures. The two deficiencies are overcome by cogeneration and inlet air cooling respectively. Energy analysis was previously carried out for this innovative system. In this work, a thermoeconomic analysis is further done using specific exergy costing method by combining the energy and the exergy analysis with the economic analysis to evaluate the total operating cost of the system over a wide range of operating variables, namely: Expander 1, Turbine inlet temperatures, pressure ratios of gas turbine, upper and lower propane cycles. Beside the total operating cost of CWHRS as the main performance variable, total generated power, thermal and exergy efficiency are considered in the analysis. The results at the design point are: C ˙ T o t a l = 2.69 (USUS$/s), P ˙ Net = 48.46 MW, η Thermal = 30.38% and η 11 = 37.23%. Optimization, by using the direct search method and the EES Software resulted in a final value of C ˙ T o t a l = 1.715 (USUS$/s), P ˙ Net = 27135 (kW) and η Thermal = 28.34%. Furthermore, sensitivity study is carried out showing the drop of 10% of the operating variables and its effect on the total operating cost. [ABSTRACT FROM AUTHOR]

This study presents a comparison of the optimisation of building energy retrofit strategies from two different perspectives: an energy/economic-based analysis and an exergy/exergoeconomic-based analysis. A recently retrofitted community centre is used as a case study. ExRET-Opt, a novel building energy/exergy simulation tool with multi-objective optimisation capabilities based on NSGA-II is used to run both analysis. The first analysis, based on the 1st Law only, simultaneously optimises building energy use and design's Net Present Value (NPV). The second analysis, based on the 1st and the 2nd Laws, simultaneously optimises exergy destructions and the exergoeconomic cost-benefit index. Occupant thermal comfort is considered as a common objective function for both approaches. The aim is to assess the difference between the methods and calculate the performance among main indicators, considering the same decision variables and constraints. Outputs show that the inclusion of exergy/exergoeconomics as objective functions into the optimisation procedure has resulted in similar 1st Law and thermal comfort outputs, while providing solutions with less environmental impact under similar capital investments. This outputs demonstrate how the 1st Law is only a necessary calculation while the utilisation of the 1st and 2nd Laws becomes a sufficient condition for the analysis and design of low carbon buildings. [ABSTRACT FROM AUTHOR]

Advanced exergoeconomic analysis, the so-called new exergetic approach combined with the economic analysis, is applied to a ground-source heap pump (GSHP) drying system in this study. The thermodynamic inefficiencies and cost performance of the system components are evaluated in parts. Moreover, the results of the advanced exergoeconomic analysis are compared to those of the conventional exergoeconomic analysis. The results show that total costs in the overall system are 4.008 $/h whereas 2.569 $/h of the total costs are avoidable. The avoidable investment costs are significantly lower than avoidable destruction costs. Advanced exergoeconomic analysis indicates that the most important system components are the drying duct and the condenser with respect to reducing the costs. It is possible to reduce 34.6% of the total costs by developing improvement strategies focused on the drying duct and the condenser. It may be concluded that the conventional exergoeconomic analysis is an effective approach to specify the components, in which costs are accumulated while the advanced exergoeconomic approach is essential to determine the cost sources and to develop cost effective improving strategies. [ABSTRACT FROM AUTHOR]

The reliability and availability considerations are introduced in the exergoeconomic investigation of a combined cycle power plant in which an organic Rankine cycle is employed to recover the waste heat from a GT-MHR (Gas Turbine Modular Helium Reactor) power plant. The SPECO (specific exergy costing) theory is employed to investigate the exergoeconomic performance of the system and assess the specific cost of the output power. For the reliability analysis, however, the SSM (state-space method) along with the probabilistic analysis of Markov processes is employed. After conducting a parametric analysis, the performance of the cycle is optimized with respect to the specific cost of output power, with and without reliability considerations. The effects of the system failure and repair rates are examined on the cost of power and availability of the combined cycle by the sensitivity analysis. The optimization results show that, the specific cost of output power for the combined cycle is around 12% lower than that for the stand alone GT-MHR. However, availability of the combined cycle is lower than that of the GT-MHR as the former has more components and a complicated system. [ABSTRACT FROM AUTHOR]

A new cogeneration system consisting of a hydrogen-fed SOFC (solid oxide fuel cell), a GT (gas turbine) and a GAX (generator-absorber-heat exchange) absorption refrigeration cycle is proposed and analyzed in detail. The electrochemical equations for the fuel cell and thermodynamic and exergoeconomic relations for the system components are solved simultaneously with EES (Engineering Equation Solver) software. Through a parametric study, the influences of such decision parameters as current density, fuel utilization factor, pressure ratio and air utilization factor on the performance of the system are studied. In addition, using a genetic algorithm, the system performance is optimized for maximum exergy efficiency or minimum SUCP (sum of the unit costs of products). The results show that, the exergy efficiency of the proposed system is 6.5% higher than that of the stand-alone SOFC. It is also observed that the fuel cell stack contributes most to the total irreversibility. The exergoeconomic factor, the capital cost rate and the exergy destruction cost rate for the overall system are observed to be 27.3%, 10.63 $/h and 28.3 $/h, respectively. It is observed that for each 6 $/GJ increase in the hydrogen unit cost, the optimum sum of the unit costs of products is increased by around 62.5 $/GJ. [ABSTRACT FROM AUTHOR]

A great interest has recently arisen for the sustainable supply of energy and fresh water, due to the growing demand from developing countries. Facing this demand by traditional technologies implies evident risks related with the high cost of fossil fuels and their environmental impact. Then, alternative solutions based on the use of renewable sources and innovative technologies must be considered. In this paper a renewable polygeneration system is examined, which includes a solar field based on parabolic trough photovoltaic/thermal collectors, a biomass heater, an absorption chiller and a Multiple Effect Distillation desalination unit. Plant operation under dynamic conditions has been analysed in previous papers; in this paper an exergetic and exergoeconomic analysis is carried out. The exergetic analysis is intended to identify the steps that mostly affect the overall plant exergy efficiency, so as to propose possible improvements. The exergoeconomic cost accounting is aimed at assigning a monetary value to each energy or material flow, thus providing a rational basis for price assignment. Both the exergetic and exergoeconomic analyses are applied to integral values of energy flows, comparing the results obtained in the summer and winter season. Finally, economic viability of the system in different context scenarios is discussed. [ABSTRACT FROM AUTHOR]

A comparative exergoeconomic assessment is reported for Ammonia-Water Rankine (AWR) and Ammonia-Water Recuperative Rankine (AWRR) bottoming power cycles. Through investigating temperature distributions of hot and cold fluids and pinch point location in heat exchangers, first energy and exergy analysis is performed and then cost balances and appropriate auxiliary equations are developed for components, so exergoeconomic variables are quantified. A parametric study is also performed to examine the effects on exergoeconomic performance of the cycles, of turbine inlet pressure and ammonia mass fraction in the working fluid. As a result, unit cost of electricity produced by turbine is determined to be 11.87 and 13.85 cent/kWh for the AWR and AWRR systems, respectively. Based on these values it is interesting to note that, unlike the energy and exergy analysis, the exergoeconomic viewpoint prefers the AWR system to AWRR. Also parametric study revealed that ammonia concentration has a great effect on exergoeconomic performance of the both systems. Increasing ammonia mass fraction increases total exergy destruction cost rate as well as unit cost of electricity produced by turbine in the both AWR and AWRR systems. This shows the advantage of using a binary mixture such as ammonia–water as a working fluid in these cycles. [ABSTRACT FROM AUTHOR]

In this paper we perform an exergoeconomic analysis to a PEM (proton exchange membrane) vehicular fuel cell system used in the latest generation of environmentally friendly cars. Two alternative configurations of a fuel cell system are considered (with and without an expander), and two alternative design concepts for each configuration: BoL (Begin of Life) and EoL (End of Life). The system including an expander generates additional power from the exhaust gases leaving the fuel cell stack, which might increase the system efficiency. However the total investment costs for this case are higher than for the other system configuration without an expander, due to the investment costs associated with the expander and its accessories. The fuel cell stack area in the EoL-sized systems is larger than in the BoL-sized systems. A larger stack area on one hand raises the investment costs, but on the other hand decreases the fuel consumption due to a higher cell efficiency. In this paper, exergoeconomic analyses have been implemented to consider a trade-off between positive and negative effects of using an expander in the system and to select the proper design concept. The results from the exergoeconomic analysis show that (a) an EoL-sized system with an expander is the most cost effective system, (b) the compression and humidification of air are very expensive processes, (c) the stack is by far the most important component from the economic viewpoint, and (d) the thermodynamic efficiency of almost all components must be improved to increase the cost effectiveness of the overall system. [ABSTRACT FROM AUTHOR]

This paper presents the findings from a multi-objective genetic algorithm optimization study on the design parameters of an underwater compressed air energy storage system (UWCAES). A 4 MWh UWCAES system was numerically simulated and its energy, exergy, and exergoeconomics were analysed. Optimal system configurations were determined that maximized the UWCAES system round-trip efficiency and operating profit, and minimized the cost rate of exergy destruction and capital expenditures. The optimal solutions obtained from the multi-objective optimization model formed a Pareto-optimal front, and a single preferred solution was selected using the pseudo-weight vector multi-criteria decision making approach. A sensitivity analysis was performed on interest rates to gauge its impact on preferred system designs. Results showed similar preferred system designs for all interest rates in the studied range. The round-trip efficiency and operating profit of the preferred system designs were approximately 68.5% and $53.5/cycle, respectively. The cost rate of the system increased with interest rates. [ABSTRACT FROM AUTHOR]

Abstract: An exergoeconomic analysis is reported for a combined system with a net electrical output of 299 MW in which waste heat from a Gas Turbine-Modular Helium Reactor (GT-MHR) is utilized by two Organic Rankine Cycles (ORCs). A parametric study is also done to reveal the effects on the exergoeconomic performance of the combined system of such significant parameters as compressor pressure ratio, turbine inlet temperature, temperatures of evaporators, pinch point temperature difference in the evaporators and degree of superheat at the ORC (Organic Rankine Cycle) turbines inlet. Finally the combined cycle performance is optimized from the viewpoint of exergoeconomics. The results show that the precooler, the intercooler and the ORC condensers exhibit the worst exergoeconomic performance. For the overall system, the exergoeconomic factor, the capital cost rate and the exergy destruction cost rate are determined to be 37.95%, 6876 $/h and 11,242 $/h, respectively. Also, it is observed that the unit cost of electricity produced by the GT-MHR turbine increases with increasing GT-MHR turbine inlet temperature but decreases as the other above mentioned parameters increase. [Copyright &y& Elsevier]

Abstract: This paper investigates the performance of a RO (reverse osmosis) desalination plant at different seawater salinity values. An energy recovery Pelton turbine is integrated with the desalination plant. Thermodynamic analysis, based on the first and second laws of thermodynamics, as well as a thermo-based economic analysis is performed for the proposed system. The effects of the system components irreversibilities on the economics and cost of product water are parametrically studied through the thermoeconomic analysis. The exergy analysis shows that large irreversibilities occur in the high pressure pump and in the RO module. Both thermodynamic and thermoeconomic performances of the overall system are investigated under different operating parameters. For the base case; the system achieves an exergy efficiency of 5.82%. The product cost is estimated to be 2.451 $/m3 and 54.2 $/MJ when source water with salinity of 35,000 ppm is fed to the system. [Copyright &y& Elsevier]

Abstract: A detailed exergoeconomic analysis is performed for a combined cycle in which the waste heat from the Gas Turbine-Modular Helium Reactor (GT-MHR) is recovered by an ammonia–water power/cooling cogeneration system. Parametric investigations are conducted to evaluate the effects of decision variables on the performances of the GT-MHR and combined cycles. The performances of these cycles are then optimized from the viewpoints of first law, second law and exergoeconomics. It is found that, combining the GT-MHR with ammonia–water cycle not only enhances the first and second law efficiencies of the GT-MHR, but also it improves the cycle performance from the exergoeconomic perspective. The results show that, when the optimization is based on the exergoeconomics, the unit cost of products is reduced by 5.4% in combining the two mentioned cycles. This is achieved with a just about 1% increase in total investment cost rate since the helium mass flow in the combined cycle is lower than that in the GT-MHR alone. [Copyright &y& Elsevier]

Abstract: CCGT (Combined-cycle gas turbines) are gaining an increasingly important role in power generation thanks to their high thermal efficiency, low installed cost and ready availability. Increasing natural gas prices, the optimization of CCGT operating parameters is becoming a topic of growing interest. In this paper two different methodologies for optimizing CCGTs are compared. The first aims to minimize the cost per unit of electricity generated, the second to minimize an objective function based on exergoeconomic principles accounting for the costs related with thermodynamic inefficiencies. Optimization results have been obtained considering different CCGT configurations, with single or multi-pressure HRSG (heat recovery steam generators), and varying the gas turbine technology, fuel price and plant capacity factor. A modular approach has been adopted to design a highly effective and flexible HRSG layout, in terms of number of pressure levels and arrangement of heat exchange sections along the flue gas path, together with the corresponding energy, exergy and cost balances, using an “interaction matrix”, with nodes between elementary components and towards the surrounding environment. [Copyright &y& Elsevier]

Abstract: Cogeneration involves the production of both electricity and thermal energy generally in the form of steam or hot water, and it has a great potential of saving primary energy in comparison to separate generation technologies. The use of cogeneration provides high energy conversion efficiency, and it also lowers the emissions released to the environment. Exergy analysis is an effective tool which provides insights into the performance of energy conversion systems, and highlights the possible improvements. On the basis of exergy concept and economics, an exergoeconomic analysis provides useful information to understand the behaviour of an energy conversion system from the cost viewpoint. This study presents the exergoeconomic analysis of a cogeneration plant at ERDEMIR, TURKEY. The mass, energy and exergy balances were done, and the exergoeconomic analysis of the plant with a 39.5 MW electricity and 80 ton/h steam production capacity, was performed. [Copyright &y& Elsevier]

Abstract: Energy, exergy and exergoeconomic analysis are often used for assessing large energy conversion systems. However exergy and exergoeconomic analysis are rarely used when small or medium scale energy generation systems, such as community CHP/CCHP plants or microcogeneration systems are evaluated. In this study energy, exergy and exergoeconomic analysis of four Community Energy Supply (CES) systems has been carried out. Biomass Steam Turbine CHP (BST), Gas Turbine CHP (GT), Biomass Integrated Gasification Gas Turbine CHP (BIGGT) and Biomass Integrated Gasification Combined Cycle CHP (BIGCC) systems have been modelled. Modelling and energy/exergy analysis have been conducted using the computer programme Cycle-Tempo. Exergoeconomic evaluation of CESS has been performed using the Specific Exergy Costing (SPECO) approach. Exergy costs of the main products: heat and electricity, have been calculated. The analysis shows that gasification of biomass reduces overall system efficiency due to the exergy destruction in the thermo-chemical conversion process when air is used as an oxidizer. A GT using natural gas as a fuel and BIGCC are the most exergy efficient systems in this study with the lowest exergy cost of electricity and heat produced. The exergy cost of electricity generated in BST is the highest. [Copyright &y& Elsevier]

Abstract: In this study, a modified exergoeconomic model is proposed for geothermal power plants using exergy and cost accounting analyses, and a case study is in this regard presented for the Tuzla geothermal power plant system (Tuzla GPPS) in Turkey to illustrate an application of the currently modified exergoeconomic model. Tuzla GPPS has a total installed capacity of 7.5 MW and was recently put into operation. Electricity is generated using a binary cycle. In the analysis, the actual system data are used to assess the power plant system performance through both energy and exergy efficiencies, exergy losses and loss cost rates. Exergy efficiency values vary between 35% and 49% with an average exergy efficiency of 45.2%. The relations between the capital costs and the exergetic loss/destruction for the system components are studied. Six new exergetic cost parameters, e.g., the component annualized cost rate, exergy balance cost, overall unavoidable system exergy destruction/loss cost rate, overall unavoidable system exergy destruction/loss cost rate, overall unavoidable system exergy production cost rate and the overall unavoidable system exergy production cost rate are studied to provide a more comprehensive evaluation of the system. [Copyright &y& Elsevier]

Abstract: A comprehensive exergy, exergoeconomic and environmental impact analysis and optimization is reported of several combined cycle power plants (CCPPs). In the first part, thermodynamic analyses based on energy and exergy of the CCPPs are performed, and the effect of supplementary firing on the natural gas-fired CCPP is investigated. The latter step includes the effect of supplementary firing on the performance of bottoming cycle and CO2 emissions, and utilizes the first and second laws of thermodynamics. In the second part, a multi-objective optimization is performed to determine the “best” design parameters, accounting for exergetic, economic and environmental factors. The optimization considers three objective functions: CCPP exergy efficiency, total cost rate of the system products and CO2 emissions of the overall plant. The environmental impact in terms of CO2 emissions is integrated with the exergoeconomic objective function as a new objective function. The results of both exergy and exergoeconomic analyses show that the largest exergy destructions occur in the CCPP combustion chamber, and that increasing the gas turbine inlet temperature decreases the CCPP cost of exergy destruction. The optimization results demonstrates that CO2 emissions are reduced by selecting the best components and using a low fuel injection rate into the combustion chamber. [Copyright &y& Elsevier]

Abstract: Multi-objective optimization for design of a benchmark cogeneration system namely as the CGAM cogeneration system is performed. In optimization approach, Exergetic, Exergoeconomic and Environmental objectives are considered, simultaneously. In this regard, the set of Pareto optimal solutions known as the Pareto frontier is obtained using the MOPSO (multi-objective particle swarm optimizer). The exergetic efficiency as an exergetic objective is maximized while the unit cost of the system product and the cost of the environmental impact respectively as exergoeconomic and environmental objectives are minimized. Economic model which is utilized in the exergoeconomic analysis is built based on both simple model (used in original researches of the CGAM system) and the comprehensive modeling namely as TTR (total revenue requirement) method (used in sophisticated exergoeconomic analysis). Finally, a final optimal solution from optimal set of the Pareto frontier is selected using a fuzzy decision-making process based on the Bellman–Zadeh approach and results are compared with corresponding results obtained in a traditional decision-making process. Further, results are compared with the corresponding performance of the base case CGAM system and optimal designs of previous works and discussed. [Copyright &y& Elsevier]

Abstract: A typical 1000 MW Pressurized Water Reactor (PWR) nuclear power plant and two similar hybrid 1000 MW PWR plants operate with natural gas and coal fired fossil fuel superheater-economizers (Hybrid PWR-Fossil fuel plants) are compared exergetically and economically. Comparison is performed based on energetic and economic features of three systems. In order to compare system at their optimum operating point, three workable base case systems including the conventional PWR, and gas and coal fired hybrid PWR-Fossil fuel power plants considered and optimized in exergetic and exergoeconomic optimization scenarios, separately. The thermodynamic modeling of three systems is performed based on energy and exergy analyses, while an economic model is developed according to the exergoeconomic analysis and Total Revenue Requirement (TRR) method. The objective functions based on exergetic and exergoeconomic analyses are developed. The exergetic and exergoeconomic optimizations are performed using the Genetic Algorithm (GA). Energetic and economic features of exergetic and exergoeconomic optimized conventional PWR and gas and coal fired Hybrid PWR-Fossil fuel power plants are compared and discussed comprehensively. [Copyright &y& Elsevier]

Abstract: Energy conservation is a central concern of the current industrial world, where increasing efficient energy usage is the only way of reducing a high energy demand. In the present study the optimization of a pulp and paper mill with a cogeneration plant has been carried out. The optimization was realized with a methodology which includes exergy, exergoeconomics, thermoeconomics and pinch analysis. The proposed methodology was useful in determining not only the best plant operating conditions but also establishing the components or subsystems with the highest irreversibilities. As a result of the study, operation changes in the recovery boiler, the turbogenerator, the thermal treatment and the deaerator were realized. Due to the higher irreversibility in the actual evaporator line, a new line of evaporators was proposed. Also, an innovative heat recycling technology as to the use of heat transformers was proposed in order to reduce waste heat discharged to the atmosphere. The results obtained with the proposed methodology, which integrates the different optimization methods, allowed reaching higher efficiencies and lower operational costs than those obtained with the optimization methods working separately. [Copyright &y& Elsevier]

Abstract: Thermoeconomics, or exergoeconomics, can be classified into the three fields: cost allocation, cost optimization, and cost analysis. In this study, a new thermoeconomic methodology for energy systems is proposed in the three fields. The proposed methodology is very simple and clear. That is, the number of the proposed equation is only one in each field, and it is developed with a wonergy newly introduced in this paper. The wonergy is defined as an energy that can equally evaluate the worth of each product. Any energy, including enthalpy or exergy, can be applied to the wonergy and be evaluated by this equation. In order to confirm its validity, the CGAM problem and various cogenerations were analyzed. Seven sorts of energy, including enthalpy and exergy, were applied for cost allocation. Enthalpy, exergy, and profit were applied for cost optimization. Enthalpy and exergy were applied for cost analysis. Exergy is generally recognized as the most reasonable criterion in exergoeconomics. By the proposed methodology, however, exergy is the most reasonable in cost allocation and cost analysis, and all of exergy, enthalpy, and profit are reasonable in cost optimization. Therefore, we conclude that various forms of wonergy should be applied to the analysis of thermoeconomics. [Copyright &y& Elsevier]

Abstract: This paper presents the definitions of some terms used in exergy analysis and exergy costing, discusses options for the symbols to be used for exergy and some exergoeconomic variables, and presents the nomenclature for the remaining terms. [Copyright &y& Elsevier]

Abstract: Thermoeconomics allows the specific costs (the costs per unit exergy) associated with exergy streams to be determined within, and at the boundaries of, energy systems. These costs are determined through the simultaneous solution of monetary balances and auxiliary equations, with the values of the primary fuel and capital costs known. The methodology for determining the auxiliary equations, when product costs are to be calculated from known fuel and capital costs, has been formulated by Lazzaretto and Tsatsaronis. These costs and other thermoeconomic variables have been shown to have utility in the optimization of energy systems. In most applications, this has been applied to systems with a specified output and variable fuel input. The goal in the optimization of these systems is to minimize product costs; for a given output with given product price(s), this is equivalent to maximizing profit. However, some practical systems, such as a combined-cycle power plant, have an essentially fixed fuel input. In these cases, capital cost is traded against power output, and profit is maximized by taking the difference of the products times their prices and the capital costs. With a known price of the product, a value fundamentally different than a specific cost is calculated. In this paper, these values are called “specific revenues”. Owing to their difference in nature from specific costs, specific revenues require different auxiliary equations. Here, the differences between revenues and costs are explained, principles are given for writing the proper governing equations and both revenues and costs are given for a simple example system. Additionally, some suggestions as to how these specific revenues may aid in system optimization are given. [Copyright &y& Elsevier]

Comprehensive exergetic and exergoeconomic analyses of a single-cylinder, four-stroke, naturally aspirated compression ignition (CI) diesel engine were conducted in the present paper. Exergy-based sustainability indicators were also determined in the study. The test engine was fueled with diesel fuel (D100), %90 diesel+10% waste cooking oil methyl ester blend (D90B10), D90B10 with Al 2 O 3 nanoparticle of 100 ppm (D90B10Al 2 O 3), D90B10 with TiO 2 nanoparticle of 100 ppm (D90B10TiO 2), and D90B10 with SiO 2 nanoparticle of 100 ppm (D90B10SiO 2) nanofuels, separately. The tests were performed at a constant engine speed of 2000 rpm and at varying engine loads from 2.5 to 10 Nm with an increment of 2.5 Nm. As a result, the exergy efficiencies of the test engine for D90B10 and D90B10Al 2 O 3 were determined to be 25.57% and 28.12%, respectively. The lowest cost flow rate of crankshaft work was found to be 0.4247 US$/h at 2.5 Nm, 0.5154 US$/h at 5 Nm for D90B10Al 2 O 3, and 0.6029 US$/h at 7.5 Nm, 0.7253 US$/h at 10 Nm for D90B10SiO 2. At 10 Nm, the highest and lowest sustainability index values were determined to be 1.391 for D90B10Al 2 O 3 and 1.344 for D90B10, respectively. From the perspective of exergy and sustainability, D90B10Al 2 O 3 had the best results. Besides, from the perspective of exergoeconomics, D90B10Al 2 O 3 had the best results at lower engine loads. As a conclusion, it can be said that nanofuels showed better performances compared to neat diesel fuel and diesel-biodiesel blend in the terms of in terms of exergy, exergoeconomics, and sustainability analyzes. Considering all analyses together, it is noticed that Al 2 O 3 -doped nanofuel is the best test fuel for this study, and then it is followed by SiO 2 and TiO 2 -doped nanofuels, respectively. Image 1 • Comprehensive exergetic, exergoeconomic and sustainability analyses of nanoparticle-doped diesel-biodiesel blends. • Detailed comparison of Al 2 O 3 , SiO 2 , and TiO 2 nanoparticles at the same fraction. • Better results with the doping of nanoparticles into neat diesel fuel or diesel-biodiesel blend in all cases. • Observed the worst results with TiO 2 -doped test fuel among nanofuels. • Al 2 O 3 -doped test fuel is the best exergetically-sustainable fuel among all test fuels. [ABSTRACT FROM AUTHOR]

Sabalan geothermal field is one of the most important geothermal fields in Iran. In this study, four novel configurations namely Single Flash-ORC (SF-ORC), Double Flash 1-ORC (DF1-ORC), Double Flash 2-ORC (DF2-ORC) and Triple Flash-ORC (TF-ORC) are proposed to produce power from two wells of the field. The configurations are assessed by thermodynamic and exergoeconomic viewpoints. The exergy and SPECO based exergoeconomic equations are developed for the components of the proposed cycles and thermodynamic as well as exergoeconomic performance parameters are calculated for the components and the cycles. A comprehensive parametric study is also carried out for the proposed configurations considering various working fluids in the ORCs. Moreover, an optimization is performed to maximize the produced power from the wells. The results depicted that the DF1-ORC produces 4.03%, 1.32% and 1.2% more power than the SF-ORC, DF2-ORC and TF-ORC, respectively, in the optimum condition. It can be concluded from the exergoeconomic analysis that the SF-ORC with R123 working fluid has the best exergoeconomic performance with the power specific cost of 3.62 $/GJ. The thermodynamic and exergoeconomic performance of the DF1-ORC is compared with previous similar studies which shows the superiority of the proposed cycle. • Four novel flash-binary based cycles are proposed for Sabalan geothermal field. • The proposed cycles utilize the energy of two wells simultaneously. • Thermodynamic and exergoeconomic analyses are performed for the cycles. • A parametric study and a thermodynamic optimization are carried out. • Single Flash-ORC with R123 working fluid has the best exergoeconomic performance. [ABSTRACT FROM AUTHOR]

In this work, an exergoeconomic analysis is applied to the power cycle of a concentrated solar plant for its design improvement. A supercritical CO2 cycle connected with the exothermic reactor of a thermochemical storage unit is considered. The analysis is conducted with the goal of highlighting the advantages of exergoeconomic analysis while suggesting changes to both the design parameters and the system configuration. Starting from the plant configuration which guarantees the maximum efficiency, the exergoeconomic analysis is iteratively applied with the goal of reducing the unit cost of electricity. The analysis is conducted in a way that cost functions of the components can be substituted with the cost analysis of specific designs. This is a big advantage of this procedure, which is suitable for applications in which economic analysis requires a detailed knowledge of the system characteristics. The procedure is then validated comparing the results with those obtained through mathematical optimization. [ABSTRACT FROM AUTHOR]

Municipal Solid Waste disposal is still a crucial issue, which is influenced by heterogeneous factors (political, social, economic and technological). The Mechanical Biological Treatment (MBT) plant is an important element of an Integrated Solid Waste Management system. These plants are aimed at separating the light and dry fraction of the Unsorted Waste from the wet one, producing the Refused Derived Fuel and recovering the metal parts. In the present work, an Exergoeconomic analysis is performed on two MBT plant structures in order to assess the unit exergy-based cost of products and allocate the irreversibility associated to each equipment. A linear variation of degree of Selective Collection (SC) of single materials (±30% respect to the base case) shows that the major influence on production costs is associated to the SC of plastic. A Monte Carlo simulation is then carried out by sampling from distributions of external (waste composition) and internal (energy consumption) uncertain variables. The resulted mean values (μ) and standard deviations (RStD) can be useful at the time of designing a new plant. The influence of the internal variable is definitely lower than the external one, with values of RStD more than 90% lower. • Two Mechanical Biological Treatment structures are analysed. • Monte Carlo simulation is performed for uncertainty analysis. • Results show the primary importance of external variables over internal ones. • Material losses are the primary cause of irreversibility in MBT plant. • The structure of MBT plant tends to absorb and uniform the input fluctuations. [ABSTRACT FROM AUTHOR]

In the current context of global energy transition, the coupling of methanol production with offshore oil & gas operations appears to be a promising option to share infrastructures and convert renewable energy into valuable fuel. However, renewable methanol synthesis has not yet reached the commercial stage. Moreover, there is no evidence on studies integrating offshore multiple resources into methanol process. The novelty of this paper is a performance analysis of emerging routes for methanol production driven by offshore wind-solar energies through exergy and exergoeconomic techniques. Two production schemes (catalytic hydrogenation of carbon dioxide and direct radical oxidation of methane) are properly designed to produce a fixed methanol rate driven by offshore wind farm and solar-thermal plants at a given oil & gas rig. The results demonstrate that carbon dioxide-based route shows the lowest exergy destruction rate (66 MW) and total cost rate (1000 $/h) compared to other option. In conjunction with this, the methane-based route gives a satisfactory exergy efficiency of 87% against a mere 2% of other pathway, as well as higher potential to increase cost savings due to lower exergoeconomic factor. Furthermore, influences of varying some key variables on the proposed parameters of the two options are investigated. • Exergy and exergoeconomic performance of novel CH 3 OH processes are investigated. • Offshore solar-wind energy is integrated into CO 2 hydrogenation and CH 4 oxidation. • Wind-diesel power plants show the worst exergy performance in both schemes. • CH 3 OH synthesis gives the highest share to total costs in CH 4 oxidation option. • Use of oil&gas sources in the process improves exergy efficiency and cost savings. [ABSTRACT FROM AUTHOR]