Exergetic Model Research Articles

Metaheuristic-driven extended exergy accounting for sustainable closed-loop food supply chain management

In this research, an exergetic mathematical model is proposed for closed-loop food supply chain network design considering economic, environmental, and social aspects. The studded closed-loop food supply chain consists of six echelons, four echelons for forwarding the products (suppliers, factory, distribution centers, and customers), and two echelons for returning the products (collecting centers and disposal centers). The exergetic model is based on the extended exergy accounting method, which calculates the consumed exergy in all six echelons by considering the equivalents of labor and capital exergy. This model aims to minimize both the economic and exergetic costs associated with the food supply chain. To solve the proposed mathematical model, an ensemble global–local search metaheuristic algorithm utilizing a combined whale optimization algorithm (WOA) and simulated annealing (SA), called CWOASA, is proposed. In the CWOASA algorithm, first, WOA is used to search the entire search space. Next, SA is applied to further improve the best solution obtained by WOA. A real dataset of a dairy supply chain is used to evaluate the efficiency of the proposed metaheuristic-driven exergy analysis model and claim its benefits over the existing methods. Simulation results revealed that the proposed method leads to a 6.74% reduction in the total exergy consumption of the supply chain. The proposed methodology offers valuable insights, shedding light on the prospective gains in terms of mitigated environmental impact for each incremental economic expenditure, thus laying the foundation for promising avenues of future research.

Exergy Management Strategies for Hybrid Electric Ground Vehicles: A Dynamic Programming Solution

Abstract In this work, exergy management strategies (ExMSs) for hybrid electric ground vehicles (HEVs) are developed. The main advantage of using the exergetic framework is the possibility of pursuing unconventional optimization goals that are inaccessible to the standard energy management strategy (EMS). For instance, in military applications, the critical goal of preventing thermal imaging detection from adversary units does not seem achievable with the conventional EMS. On the other hand, the exergy-based framework can be adopted to reduce the vehicle thermal emissions through the minimization of exergy terms related to heat exchange. Moreover, the overall efficiency of the vehicle can be increased through the minimization of the exergy destruction, a quantity that is not quantifiable by energy-based methods. In this paper, the exergetic model of a series hybrid electric military truck and the exergetic model of the electric induction generator are developed and used to formulate and solve two novel exergy management strategies aiming to minimize genset exergy destruction and thermal emissions, respectively. The optimal solutions to the EMS and ExMSs control problems are obtained through Dynamic Programming over two driving missions. The results show that ExMS for the minimization of exergy destruction achieves similar results to the standard EMS, while the ExMS for the minimization of thermal emissions obtains significantly lower thermal emissions compared to the EMS, effectively reducing the thermal imaging detection risk.

Comparison of various dual-temperature zones space heating systems based on energy cascade utilization principle

The high efficiency heating system is crucial in ensuring both residents and buildings remain comfortably warm during cold seasons, providing not only a comfortable living environment but also contributing to health, productivity, and overall well-being. Based on the energy cascade utilization principle, three multi-temperature zone space heating systems were introduced firstly, namely warm air (WA), radiator combined with fresh air (RA + FA), and floor combined with fresh air (FL + FA) in this research. The detailed energetic and exergetic models of these space heating systems were developed to investigate and compare the system performance under various operated conditions, including the fresh air, supply air, radiator, and floor temperatures. The results showed that the energy efficiency ratio (EER) value increased first and then decreased with the supply air temperature increasing for the WA, while the EER of the RA + FA and FL + FA decreased with the floor and radiator temperatures increasing. The maximal EER for the WA, FL + FA, and RA + FA system were 2.96, 3.52, and 3.43 under selected conditions. Besides, the WA system outperformed the RA + FA system in terms of exergy efficiency, and the WA system exergy efficiency ranged from 22 to 28% under selected conditions. Lastly, for the FL + FA system, the system exergy loss increased by approximately 0.016–0.018 kW/°C for the floor temperature, and the values were 0.024 kW/°C for fresh air temperature.

4E Assessment of an Organic Rankine Cycle (ORC) Activated with Waste Heat of a Flash-Binary Geothermal Power Plant.

In this paper, the 4E assessment (Energetic, Exergetic, Exergoeconomic and Exergoenvironmental) of a low-temperature ORC activated by two different alternatives is presented. The first alternative (S1) contemplates the activation of the ORC through the recovery of waste heat from a flash-binary geothermal power plant. The second alternative (S2) contemplates the activation of the ORC using direct heat from a geothermal well. For both alternatives, the energetic and exergetic models were established. At the same time, the economic and environmental impact models were developed. Finally, based on the combination of the exergy concepts and the economic and ecological indicators, the exergoeconomic and exergoenvironmental performances of the ORC were obtained. The results show higher economic, exergoeconomic and exergoenvironmental profitability for S1. Besides, for the alternative S1, the ORC cycle has an acceptable economic profitability for a net power of 358.4 kW at a temperature of 110 °C, while for S2, this profitability starts being attractive for a power 2.65 times greater than S1 and with a temperature higher than 135 °C. In conclusion, the above represents an area of opportunity and a considerable advantage for the implementation of the ORC in the recovery of waste heat from flash-binary geothermal power plants.

Evaluating and modelling of thermodynamic and environmental parameters of a gas turbine engine and its components

Nowadays, aero-engines have been opted more due to their important benefits for powering unmanned aerial vehicles or producing electricity or pneumatic powers for aircraft engines. In this study, a small gas turbine engine (S-GTE) used in aviation applications was dealt with using thermodynamic and environmental methods at ten different power settings (PSs) as well as different design variables involving turbine inlet temperature (TIT) ranging 1350 K and 1550 K and pressure ratio of compressor ranging 10 and 16. Thus, both effects of design variables and power settings on thermo-environmental metrics were investigated under different cases. Additionally, several parameters of the engine were modelled according to power settings which the engine operate. When considering performance findings, specific fuel consumption increases from 0.3262 kg/kWh to 1.2341 kg/kWh as shaft power decreases from 415 kW to 41.6 kW. According to thermodynamics computations, exergy efficiency of the combustor diminishes from 83.52% to 74.92% at baseline. Moreover, the higher TIT leads this metric to increase from 83.52% to 87.17%, whereas effect of CPR is not observed as important as the impact off TIT. However, exergy efficiency of the whole engine changes from 24.15% to 6.38% due to decrement in the PS. Moreover, the higher TIT and CPR of the engine favorably affect this metric. On the other hand, enviroeconomic cost factor (ECF) of the engine drops from 39.65 billion Euro/year to 14.98 billion Euro/year, but environmental effect factor increases 2.62 to 9.29 due to decreasing PS. Lastly, there is non-linear relationship between exergy efficiency and power setting, whereas enviroeconomic factor of the engine linearly changes with PSs. Namely, exergetic model is obtained with high accuracy as R2 of 0.995 at three-degree function while enviroeconomic cost factor model is achieved with high correctness as R2 of 0.9972 at first-degree function. These results show that modelling of thermodynamic metrics helps in understanding how extent these indicators pertinent to the engine are affected from power settings. Thus, optimum power setting without penalty on the engine performance could be discovered.

Exergetic model of a small-scale, biomass-based CCHP/HP system for historic building structures

• Methodology for exergy analysis of bio-solar CCHP/HP systems. • Transient and dynamic model for optimal sizing of gasifier and other components. • Optimal sizing can significantly reduce irreversibility losses. • Biomass types have marginal effect on system exergy efficiency. Biomass-based, small-scale Combined Cooling, Heating and Power (CCHP) systems can increase the energy autonomy of building complexes while reducing their Greenhouse Gases (GHG) emissions. In combination with air-to-water Heat Pumps (HP), highly efficient energy systems can be designed, which allow for high flexibility in serving thermal and electric demands. This study presents an exergy evaluation of such a small-scale CCHP/HP system using a dynamic modelling approach based on gasification of various types of woody biomass. The transient model takes into account the effects of the biomass chemical composition as well as of ambient temperatures on the exergy performance of all key components for various CCHP system sizes supporting an HP system. The model has been applied in a case study for a historic building complex, where the CCHP sub-system would support an HP-subsystem allowing for downsizing the latter. The results show that smaller CCHP systems operate with higher exergy efficiency, because for larger systems the heat transfer from the engine and the operation of the absorption chiller are less exergy efficient. The electric load-following CCHP subsystem reaches exergy efficiencies of up to 13.3%, indicating huge improvement potential for system and sub-system design. It was also found that the biomass composition heavily influences the exergy efficiency of the gasifier and in turn changes the exergy efficiency of the syngas engine and the entire CCHP sub-system.

An Exergetic Model for the Ambient Air Temperature Impacts on the Combined Power Plants and its Management Using the Genetic Algorithm

4E analysis is used on a Brayton–Rankine combined cycle power plant (CCPP) with a dual pressure heat recovery steam generation (HRSG) system. A multi-objective genetic-based evolutionary optimization has been used to estimate the most optimal exergy efficiency status, exergy cost reduction, carbon emission reduction, and NOx emission reduction. For the validation of the data, the simulation results are compared with the plant’s data. This study investigates the effect of every decisive parameter on the objective performance parameters of the CCPP. The primary estimated results are the emission rates, efficiencies, and the exergoeconomic cost of the system. At the optimum operational state, the exergy efficiency may increase by 10%, while the total emissions may decrease by 14.6%. The conventional technical measures’ effectiveness to improve the combined cycle power plant’s energy performance is applied to the simulated case study. Results have shown that the main source of the exergy destruction in this system is the HRSG and the combustion chamber, and also the overall performance of the plant shows great sensitivity to the ambient air temperature. This fact has shown that climate change and global warming are effective in thermal power plants’ performance. Therefore, the effect of the climate change on the ambient air temperature impact on the power plant and the 4E performance of the simulated combined cycle power plant is also studied. The results show that, due to the global warming effect, the exergy efficiency of the CCPP unit is decreased by over 0.2% in the last two decades, which can be generalized to all thermal electricity generation units throughout the world based on the mean global temperature rise in the last decades.

Energy and exergy analysis of a ground source heat pump system with a slinky ground heat exchanger supported by nanofluid

This work contains the experimental analysis results in real environment conditions of the use of $$\hbox{Al}_2\hbox{O}_3$$ -based nanofluid (NF) at different concentration ratios (0.1% and 0.2%) in a ground source heat pump (GSHP) system with a slinky ground heat exchanger (GHE). The energetic and exergic efficiencies of the system were investigated with the data obtained from the experimental results of base fluid (ethylene glycol (EG)-water) (EG volumetric ratio 25%) and NF with $$\hbox{Al}_2\hbox{O}_3$$ concentration ratios of 0.1% and 0.2%. The exergetic model is obtained by applying energy and exergy equations for each system component. Exergetic efficiencies of the system components are evaluated separately and their potential for improvement is presented. According to the results of the energetic analysis, the overall system’s coefficient of performance (COP) values for the base fluid and NF with concentration ratios of 0.1% and 0.2% were 4.30, 4.38 and 4.34, respectively. These results show that NF contributes to system performance. However, an increase in system performance was not achieved due to the increase in NF concentration; on the contrary, a decrease in performance was observed. Exergetic efficiencies of the system for base fluid and NF with concentration ratios of 0.1% and 0.2% were 88.3%, 89.7% and 89.0%, respectively, for the heat pump unit, while these values were 78.7%, 79.3% and 79.0% for the entire system, respectively. The results show that the usage of NF with low concentration ratios increases the energetic and exergic efficiency of the system.

Exergetic Modeling of an IGCC Plant

Exergetic Modeling of an IGCC Plant

Solar still desalination system equipped with paraffin as phase change material: exergoeconomic analysis and multi-objective optimization.

The current work is about analysis and multi-objective optimization (MOO) of weir-type solar still systems equipped with phase change material (PCM) regarding the exergetic and economic performance. To do so, the energetic and exergetic modeling of the suggested system is conducted then the substantial economic factors is applied to obtain the total cost rate of the considered SSDS. The total exergetic efficiency and total annual cost (TAC) is considered objective functions. Four parameters include mass of the PCM (mPCM), inlet brine water flow rate ([Formula: see text]), gap distance (d), and insulation width (xins) is chosen as decision variables. Moreover, a genetic algorithm-based MOO was applied to find the optimum states of evaluated solar still unit. The outputs represented that increasing the brine feed water mass flow rate does not affect the TAC while decreasing distilled water production rate. The scattered distribution of optimum states infers that the optimum value of PCM mass is about 1 kg. In addition, applied MOO reveals that with optimization of the studied system, the exergy efficiency increases about 1.47% and the annual distilled water increases 4.35% compared with the non-optimized system. The suggested system is capable to produce fresh water in remote areas without any pollution as well as in a low cost rate.

Thermo-Economic Optimization of a Cogeneration System Fueled by Syngas Produced from Gasification of Palm Biomass

This study presents the economic and the thematic optimization of a cogeneration system using syngas as fuel from palm biomass gasification. An energetic, exergetic, and thermo-economical model of each one of the components of the system is proposed to study the energetic and exergetic performance of the system. In addition, the unit costs of the products of the system are determined to calculate thermo-economic indicators, and thus to propose a multivariable optimization of the system in order to minimize the costs and to maximize the generated power. The results show that the most significant losses per destroyed exergy are found in the combustion chamber, reaching almost seventy percent of the total operating with Syngas, with higher destroyed exergy costs. The multi-objective optimization has allowed obtaining both the higher energy power and the generation cost. In addition, the compressor inlet air temperature increases, causing a decrease in the energy generated by the cogeneration system using syngas as fuel. It has been verified that when operating with syngas, there is a reduction in energy and exergy efficiency of the system.

Availability analysis of two dimensional nucleation on cylindrical substrates

Within the framework of the classical availability of heterogeneous nucleation, a scaled exergetic model has been developed to elucidate the two-dimensionality effects on the potency factor which is an explicit dimensionless scaled parameter for the nucleation barrier height. The effects of system geometry and substrate wettability on the thermodynamics of heterogeneous nucleation on a two-dimensional curved substrate are studied. The difference in the potency factor between two-dimensional nucleation on a convex and a flat substrate is always positive and has a maximum value for a given size factor. The regime of the associated contact angle related to maxima are in the cluster-phase-philic regime irrespective of the substrate size or the three phases associated with heterogeneous nucleation. On the other hand, the difference in the potency factor between heterogeneous nucleation on a concave and a planar substrate is always negative and has a minimum value for a given size factor. In this case, the regime of the associated contact angle related to maxima are in the cluster-phase-phobic regime irrespective of the substrate size or the three phases associated with heterogeneous nucleation. The potency factor has lower values in case of concave substrate and has higher values in case of convex substrate and heterogeneous nucleation on a flat substrate is always in between that of the convex substrate and the concave substrate.

Exergy Analysis and Optimization of a Combined Heat and Power Geothermal Plant

This paper presents the optimization of parallel distribution between electricity and heat production for a geothermal plant. The geothermal fluid is split into two streams, one used for an Organic Rankine Cycle (ORC) system, and the other for a District Heating Network (DHN). The superstructure to be used for the optimization problem includes the ORC components and the DHN topology constituted by a definite consumer and optional consumers. A Mixed Integer Non-Linear Programming (MINLP) optimization problem is formulated and solved using the GAMS software. This paper is focused on exergetic aspect. The main lines for formulation of the problem are reminded, yet the exergetic model is fully described. Exergy analysis is performed for two optimal solutions (economic and exergetic objective functions). Results for both optimizations are first compared. The analysis of exergetic efficiency of the ORC and the DHN may suggest that exergetic optimization privileges the system with the highest efficiency: the ORC. The DHN configuration is then the smallest as possible. Finally, a sensitive analysis is performed for the exergetic optimization. This analysis reveals our previous conclusion is not necessarily true. Taller configuration can exist even if ORC efficiency is higher than DHN efficiency. These results highlight the relevance of using an optimization approach for a Combined Heat and Power (CHP) plant.

The integration of exergy criterion in energy planning analysis for 100% renewable system

This paper presents a new methodology that allows to define a 100% renewable smart energy system in a sustainable manner. The authors integrate the EnergyPlan with a mathematical model that analyzes the energy system from an exergetic point of view taking into account the exergy of the whole energy system and its components. Once multiple scenarios are obtained by EnergyPLAN, the exergetic model identifies the scenario characterized by the highest exergetic efficiency and the lowest energy wasting. This approach is a novelty since the “exergetic” optimization criterion coupled with EnergyPLAN software has never been utilized. Since the best energy system could not be economically attractive, this methodology might support Municipalities in setting up focused incentives to make the sustainable solutions the most cost effective too.The authors present a case study by applying the new methodology to the city of Pompeii. The results show that the best solution provides 21.0 MWe capacity of PV plant, integrated to 8.10 MWe of CHP plant. Due to a high value of critical excess electricity production, 10 MWe heat pumps must be installed. Finally, a solar thermal plant is installed. The proposed system could be only realized if new incentives are provided.

Energetic and exergetic investigations of an innovative heat recovery exhaust system using a double acting type Stirling engine based on theoretical analysis

This study aims to predict the feasibility and the performances of an innovative recovery system. It couples a double acting Stirling engine to the exhaust hot gas of internal combustion engines drive shaft. The behaviour of a micro-cogeneration system using Stirling engine is investigated. Referring to previous energetic analyses, exergetic model is set up in order to quantify the exergy destruction and efficiencies in each part of the recovery exhaust system. The repartition of the exergy fluxes in each part are determined and represented in Grassmann diagram. Possible solutions to improve the overall exergy efficiency of the micro-cogeneration unit were proposed. The performance of the Stirling engine was evaluated under different operating conditions. Effects of certain parameters including charge pressure, rotational speed, hot exhaust gas temperature and cooling water temperature are systematically studied. The effect of hot-side and cold-side exchange surfaces on the power and efficiency of the Stirling engine as well as on the efficiency of the global micro-cogeneration unit is investigated. The performance of the Stirling engine using three different working fluids: nitrogen N2, helium He and hydrogen H2 is estimated. Results can be useful for scientists and engineers to design an appropriate and efficient micro-cogeneration unit.

Energetic and exergetic investigations of an innovative heat recovery exhaust system using a double acting type Stirling engine based on theoretical analysis

This study aims to predict the feasibility and the performances of an innovative recovery system. It couples a double acting Stirling engine to the exhaust hot gas of internal combustion engines drive shaft. The behaviour of a micro-cogeneration system using Stirling engine is investigated. Referring to previous energetic analyses, exergetic model is set up in order to quantify the exergy destruction and efficiencies in each part of the recovery exhaust system. The repartition of the exergy fluxes in each part are determined and represented in Grassmann diagram. Possible solutions to improve the overall exergy efficiency of the micro-cogeneration unit were proposed. The performance of the Stirling engine was evaluated under different operating conditions. Effects of certain parameters including charge pressure, rotational speed, hot exhaust gas temperature and cooling water temperature are systematically studied. The effect of hot-side and cold-side exchange surfaces on the power and efficiency of the Stirling engine as well as on the efficiency of the global micro-cogeneration unit is investigated. The performance of the Stirling engine using three different working fluids: nitrogen N2, helium He and hydrogen H2 is estimated. Results can be useful for scientists and engineers to design an appropriate and efficient micro-cogeneration unit.

Exergetic Model as a Guideline for Implementing the Smart-factory Paradigm in Small Medium Enterprises: The Brovedani Case

The development and implementation of the smart factory paradigm seems to be a must almost widespread all over the Western manufacturing companies so far. This article explores the application of exergetic analysis models as a feasible approach to customize such an announced paradigm shift: the implementation criteria as well as the true expected benefits are, in fact, far to be clearly understood or even perceived.An Italian medium enterprise located in the south of Italy operating in the automotive sector is adopted as a test bench. The standard use of exergetic model was adopted to assess and improve the sustainability of the manufacturing processes performed by the company, namely: turning, milling, grinding, plating and dehydrogenation.This thermodynamic view of the processes, on the other hand, represented a guideline to design a smart factory solution, and thus to structure the critical variables and the paths to digitalize processes for the intelligent control of the core production processes.

Improving supply chain sustainability using exergy analysis

Sustainable supply chain management is the improved level of management through the integration of environmental and social issues in parallel to the economic issues. It has emerged as a growing subject that now receives increasing interest from practitioners and academicians. Limited attempts have been made to take a broader look at the overall issues that form the core topics of this type of supply chain. In fact, there have been many exclusive studies that investigated the impact of inadvertent or unavoidable costs of supply chain processes. Exergy analysis is a powerful thermodynamic tool that may be employed to analyze and identify the inefficiencies in a process or a system. It has also been extended to efficiently evaluate how sustainable an industrial system, process or product is. This paper introduces exergetic models that compute and compare the consumed exergy for two coordination policies. It, also, evaluates the consumed exergy when producing/ordering locally versus globally. It recognizes the importance of financial, social and environmental aspects of choosing the more sustainable destination to produce and distribute a product. Numerical examples are presented and discussed to provide some insights for managers and decision-makers to select between domestic policies based on the consumed exergy and the monetary cost. Results show that societies can gain more from less consumed exergy and firms can save on some costs when producing/ordering domestically. This paper recommends to governments and other stakeholders to take actions that are effective in making societies consume resources wisely.

Deriving an exergetic economic production quantity model for better sustainability

Businesses strive to be sustainable because of internal and external pressures. To examine sustainability, firms may use different methods of analysis. Extended Exergy Accounting (EEA) - a resource based evaluation method - is such a tool used to examine environmental, social, and economic sustainability. This paper re-examines the economic production quantity (EPQ) model, in an attempt to reflect the needs of sustainability. The paper uses EEA and the laws of thermodynamics to measure the sustainability of a production-inventory system and finds that in some situations sustainability can be profitable. EEA measures the value of a commodity, based on the consumption of the natural and physical resources as opposed to the classical EPQ model, which uses monetary cost. Measuring the exergy consumed during the production of a commodity shows that the exergetic model developed can deliver better sustainability and profitability than the classical EPQ. This should further encourage companies to move towards sustainable strategies. The results suggest that governments, individuals and other organizations should encourage companies to move towards sustainable strategies.

Comparison Based on Exergetic Analyses of Two Hot Air Engines: A Gamma Type Stirling Engine and an Open Joule Cycle Ericsson Engine

In this paper, a comparison of exergetic models between two hot air engines (a Gamma type Stirling prototype having a maximum output mechanical power of 500 W and an Ericsson hot air engine with a maximum power of 300 W) is made. Referring to previous energetic analyses, exergetic models are set up in order to quantify the exergy destruction and efficiencies in each type of engine. The repartition of the exergy fluxes in each part of the two engines are determined and represented in Sankey diagrams, using dimensionless exergy fluxes. The results show a similar proportion in both engines of destroyed exergy compared to the exergy flux from the hot source. The compression cylinders generate the highest exergy destruction, whereas the expansion cylinders generate the lowest one. The regenerator of the Stirling engine increases the exergy resource at the inlet of the expansion cylinder, which might be also set up in the Ericsson engine, using a preheater between the exhaust air and the compressed air transferred to the hot heat exchanger.