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Exergy Analysis and Optimization of Energy Systems and Processes

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J: Thermal Management".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 31161

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Prof. Dr. Michel Feidt

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Laboratory of Energetics and Theoretical and Applied Mechanics, University of Lorraine, 2 av. de la Forêt de Haye, CEDEX, 54504 Vandoeuvre, France
Interests: thermodynamics; energy; transfers; conversion
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Special Issue Information

Dear Colleagues,

This Special Issue is concerned with exergy concept and uses. Exergy (availability) is an old concept that was proposed a long time ago by Gouy in 1889, and was developed after by Stodola, Rant, and more recently, by Szargut. Actually, this scientific field is mature from an engineering point of view, and we note every year that between 1000 and 1500 publications are relevant to the subject. Some scientific journals are particularly involved in exergy analysis (energies too).

The objective of this Special Issue is to reinforce the uses of the concept in new domains (life sciences, societal aspects, nano and mini scales, and megascale systems). Progresses in chemical and mechanical engineering remain of interest, but with a focus on integration and hybridization. The combination of exergy analysis and optimization with environmental or economic objectives (or constraints) are important too, particularly exergo–economic consideration.

From a fundamental point of view, the relation of exergy analysis to efficiency, environmental impact, and renewability remains to be developed. Emergy compared to exergy is also of interest. Lastly, the exergy of the systems far from equilibrium, and with non stationary references, constitute a coming field of research improving the exergy method.

You are welcomed to contribute to the fundamental and applied aspects of the exergy concept, which is now mature, and to migrate in various new scientific specialities.

Prof. Dr. Michel Feidt
Guest Editor

Manuscript Submission Information

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Keywords

exergy, energy conversion, and emergy
exergy costing
renewability
exergo-economy
efficiency
waste heat
living systems
fundamentals

Published Papers (10 papers)

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Research

16 pages, 2889 KiB

Open AccessArticle

Comparative Exergy Analysis of Units for the Porous Ammonium Nitrate Granulation

by Dmytro Levchenko, Andrii Manzharov, Artem Artyukhov, Nadiya Artyukhova and Jan Krmela

Energies 2021, 14(2), 280; https://doi.org/10.3390/en14020280 - 06 Jan 2021

Viewed by 1990

Abstract

The article deals with the study on the efficiency of units for porous ammonium nitrate production. The ways which increase the effective implementation of energy resources are determined by including the ejector recycling module, heat and mass exchangers that utilize principles of regenerative indirect evaporative cooling, and the sub-atmospheric inverse Brayton cycle. Mixed exergy analysis evaluates all flows of the system contour as those of the same value. The target parameter for determining the efficiency of both systems is the ratio of the unit’s productivity to the exergy expenditures to produce the unit mass of the product. As a result, it is found that the mentioned devices and units enable to increase the efficiency of the basic scheme by 87%. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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20 pages, 2842 KiB

Open AccessArticle

Evaluation of Two-Column Air Separation Processes Based on Exergy Analysis

by Muhammad Haris Hamayun, Naveed Ramzan, Murid Hussain and Muhammad Faheem

Energies 2020, 13(23), 6361; https://doi.org/10.3390/en13236361 - 02 Dec 2020

Cited by 20 | Viewed by 5202

Abstract

Cryogenic air separation processes are widely used for the large-scale production of nitrogen and oxygen. The most widely used design for this process involves two distillation columns operating at different pressures. This work focuses on the selection of suitable cryogenic air separation process by evaluating seven alternative designs of the two-column air separation process based on detailed exergy analysis. The feed conditions (500 tons/h, and 50% relative humidity of air), product purities (99 mole% for both nitrogen and oxygen), and operational conditions (pressures of both distillation columns) are kept same in all designs. The two cryogenic distillation columns in each configuration are heat-integrated to eliminate the need for external utilities. Steady-state simulation results are used to calculate the exergy efficiency (%) of each equipment as well as its contribution toward the overall exergy destruction rate (kW) of the process. The results show that the compression section is a major source of exergy destruction, followed by the low-pressure column, and the multi-stream heat exchanger. A Petlyuk-like configuration, labeled as C1, provides the lowest exergy destruction rate. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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23 pages, 1609 KiB

Open AccessArticle

Modelling Grid Constraints in a Multi-Energy Municipal Energy System Using Cumulative Exergy Consumption Minimisation

by Lukas Kriechbaum, Philipp Gradl, Romeo Reichenhauser and Thomas Kienberger

Energies 2020, 13(15), 3900; https://doi.org/10.3390/en13153900 - 30 Jul 2020

Cited by 2 | Viewed by 2277

Abstract

Efficiency measures and the integration of renewable energy sources are key to achieving a sustainable society. The cumulative exergy consumption describes the resource consumption of a product from the raw material to the final utilisation. It includes the exergy expenses for energy infrastructure as well as the imported energy. Since consumers and renewable potentials are usually in different locations, grid restrictions and energy flows have a significant impact on the optimal energy system design. In this paper we will use cumulative exergy minimisation together with load flow calculations to determine the optimal system design of a multi-cell municipal energy system. Two different load flow representations are compared. The network flow model uses transmission efficiencies for heat, gas and electricity flows. The power flow representation uses a linear DC approximated load flow for electricity flows and a MILP (mixed integer linear programming) representation for heat and gas flows to account for the nonlinear pressure loss relation. Although both representations provide comparable overall results, the installed capacities in the individual cells differ significantly. The differences are greatest in well meshed cells, while they are small in stub lines. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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27 pages, 5160 KiB

Open AccessArticle

Performance Enhancement of Nitrogen Dual Expander and Single Mixed Refrigerant LNG Processes Using Jaya Optimization Approach

by Ali Rehman, Muhammad Abdul Qyyum, Ashfaq Ahmad, Saad Nawaz, Moonyong Lee and Li Wang

Energies 2020, 13(12), 3278; https://doi.org/10.3390/en13123278 - 25 Jun 2020

Cited by 12 | Viewed by 2851

Abstract

The nitrogen (N₂) expander and single mixed refrigerant (SMR) liquefaction processes are recognized as the most favorable options to produce liquefied natural gas (LNG) at small-scale and offshore sites. These processes have a simple and compact design that make them efficient with respect to their capital costs. Nevertheless, huge operating costs, mainly due to their lower energy efficiency, remains an ongoing issue. Utilization of design variables having non-optimal values is the primary cause for the lower energy efficiency; which, in turn, leads to exergy destruction (i.e., entropy generation), and ultimately the overall energy consumption is increased. The optimal execution of the design variables of LNG processes can be obtained through effective design optimization. However, the complex and highly non-linear interactions between design variables (refrigerant flowrates and operating pressures) and objective function (overall energy consumption) make the design optimization a difficult and challenging task. In this context, this study examines a new optimization algorithm, named “Jaya”, to reduce the operating costs of nitrogen dual expander and SMR LNG processes. The Jaya approach is an algorithm-specific parameter-less optimization methodology. It was found that by using the Jaya algorithm, the energy efficiency of the SMR process and nitrogen dual expander natural gas (NG) liquefaction process can be enhanced up to 14.3% and 11.6%, respectively, as compared to their respective base cases. Using the Jaya approach, significant improved results were observed even compared to other previously used optimization approaches for design optimization. Results of conventional exergy analysis revealed that the exergy destruction of SMR and N₂ dual expander process can be reduced by 17.4% and 14%, respectively. Moreover, economic analysis identified the 13.3% and 11.6% relative operating costs savings for SMR and N₂ dual expander LNG processes, respectively. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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14 pages, 5377 KiB

Open AccessArticle

Heating Performance Characteristics of an Electric Vehicle Heat Pump Air Conditioning System Based on Exergy Analysis

by Xingwang Tang, Qin Guo, Ming Li and Mingzhe Jiang

Energies 2020, 13(11), 2868; https://doi.org/10.3390/en13112868 - 04 Jun 2020

Cited by 7 | Viewed by 3808

Abstract

In this paper, a heat pump air conditioning system (HPACS) with refrigerant R134a based on the functional requirements of battery electric vehicle is designed and tested. Experiments were conducted to evaluate the effects of different ambient temperature, air flow rate of internal condenser, expansion valve (EXV) opening and compressor speed. The results demonstrate that air flow rate of internal condenser, EXV opening and compressor speed have important impact on heating capacity, compressor power consumption and coefficient of performance (COP) under several ambient temperatures. To verify the HPACS can also provide the heating capacity required by the battery electric vehicle cabin in cold climate, the system was also tested under a −5 °C ambient temperature, it was found that the heating capacity is 3.6 kW and the COP is 3.2, demonstrating that the system has high energy efficiency. In addition, heating process analysis of the HPACS under lower temperature is studied by exergy principle. The results indicate that compressor is the highest exergy destruction in all components, accounting for 55%. The percentage of exergy destruction in other components is about 28%, 12% and 5% for the expansive valve, condenser, and evaporator. Furthermore, air flow rate of internal condenser, ambient temperature and expansion valve opening have important impact on exergy destruction and exergy efficiency of the HPACS. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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21 pages, 354 KiB

Open AccessArticle

Relative Free Energy Function and Structural Theory of Thermoeconomics

by Antonio Valero and César Torres

Energies 2020, 13(8), 2024; https://doi.org/10.3390/en13082024 - 18 Apr 2020

Cited by 4 | Viewed by 1871

Abstract

This paper explores the advantages of using relative free energy instead of exergy to build a mathematical theory of thermodynamic costs to diagnose malfunctions in thermal systems. This theory is based on the definition of a linearized characteristic equation that represents the physical behavior of each component. The physical structure of the system described by its energy interrelationships is called “primal”, and its derivatives are the costs and consumptions. The obtained costing structure is the mathematical “dual” of its primal. The theory explains why the F and P cost assessment rules and any other suggestion may (or may not be) rational under a given disaggregation scheme. A result of the theory is a new thermodynamic function, called the relative free energy, and a new parameter called deterioration temperature due to a component’s deterioration cause, characterized by a h-s thermodynamic trajectory describing the effects on the exiting stream. The relative free energy function allows for an exact relationship between the amount of used resources and the increase in entropy generation caused by the deterioration path of the component. This function allows the obtaining of, for the first time, an appropriate characteristic equation for a turbine and a new definition of efficiency that does not depend on the environment temperature but on its deterioration temperature. Also, costing with relative free energy instead of exergy may open a new path for more precise and straightforward assessments of component deteriorations. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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15 pages, 2304 KiB

Open AccessArticle

New Criteria to Characterize the Waste Heat Recovery

by Michel Feidt, Monica Costea, Renaud Feidt, Quentin Danel and Christelle Périlhon

Energies 2020, 13(4), 789; https://doi.org/10.3390/en13040789 - 11 Feb 2020

Cited by 12 | Viewed by 2234

Abstract

Waste heat recovery is an actual goal. The best way to valorize waste heat is to use it directly with the appropriate level of temperature. If the temperature level is insufficient, many reverse machine configurations are available in order to obtain the appropriate conditions (the most known are heat pumps and heat transformers). Finally, the remaining unused heat could be converted to any noble form of energy (mechanical, electrical essentially). We propose here to examine, with a new point of view, the thermomechanical conversion limit of waste heat. This limit corresponds to adiabatic conversion for an endo-reversible Carnot engine, with a perfect thermal contact at the atmospheric sink (supposed infinite). The Carnot–Chambadal model version is applied to latent and sensible heat recovery cases. The results associated with these two cases differ fundamentally. Comments are provided on the two studied cases, and new criteria to characterize the corresponding waste heat recovery are proposed. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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19 pages, 1560 KiB

Open AccessArticle

Exergy Analysis and Process Optimization with Variable Environment Temperature

by Michel Pons

Energies 2019, 12(24), 4655; https://doi.org/10.3390/en12244655 - 07 Dec 2019

Cited by 4 | Viewed by 2021

Abstract

In its usual definition, exergy cancels out at the ambient temperature which is thus taken both as a constant and as a reference. When the fluctuations of the ambient temperature, obviously real, are considered, the temperature where exergy cancels out can be equated, either to the current ambient temperature (thus variable), or to a constant reference temperature. Thermodynamic consequences of both approaches are mathematically derived. Only the second approach insures that minimizing the exergy loss maximizes performance in terms of energy. Moreover, it extends the notion of reversibility to the presence of an ideal heat storage. When the heat storage is real (non-ideal), the total exergy loss includes a component specifically related to the heat exchanges with variable ambient air. The design of the heat storage can then be incorporated into an optimization procedure for the whole process. That second approach with a constant reference is exemplified in the case study of heat pumping for heating a building in wintertime. The results show that the so-obtained total exergy loss is the lost mechanical energy, a property that is not verified when exergy analysis is conducted following the first approach. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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34 pages, 7633 KiB

Open AccessArticle

Hybrid Optimization Methodology (Exergy/Pinch) and Application on a Simple Process

by Christelle Bou Malham, Assaad Zoughaib, Rodrigo Rivera Tinoco and Thierry Schuhler

Energies 2019, 12(17), 3324; https://doi.org/10.3390/en12173324 - 28 Aug 2019

Cited by 7 | Viewed by 2685

Abstract

In the light of the alarming impending energy scene, energy efficiency and exergy efficiency are unmistakably gathering momentum. Among efficient process design methodologies, literature suggests pinch analysis and exergy analysis as two powerful thermodynamic methods, each showing certain drawbacks, however. In this perspective, this article puts forward a methodology that couples pinch and exergy analysis in a way to surpass their individual limitations in the aim of generating optimal operating conditions and topology for industrial processes. Using new optimizing exergy-based criteria, exergy analysis is used not only to assess the exergy but also to guide the potential improvements in industrial processes structure and operating conditions. And while pinch analysis considers only heat integration to satisfy existent needs, the proposed methodology allows including other forms of recoverable exergy and explores new synergy pathways through conversion systems. A simple case study is proposed to demonstrate the applicability and efficiency of the proposed method. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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27 pages, 7985 KiB

Open AccessArticle

Numerical Calculation Method of Model Predictive Control for Integrated Vehicle Thermal Management Based on Underhood Coupling Thermal Transmission

by Pengyu Lu, Qing Gao, Liang Lv, Xiaoye Xue and Yan Wang

Energies 2019, 12(2), 259; https://doi.org/10.3390/en12020259 - 15 Jan 2019

Cited by 16 | Viewed by 4877

Abstract

The nonlinear model predictive control (NMPC) controller is designed for an engine cooling system and aims to control the pump speed and fan speed according to the thermal load, vehicle speed, and ambient temperature in real time with respect to the coolant temperature and comprehensive energy consumption of the system, which serve as the targets. The system control model is connected to the underhood computational fluid dynamics (CFD) model by the coupling thermal transmission equation. For the intricate thermal management process predictive control and system control performance analysis, a coupling multi-thermodynamic system nonlinear model for integrated vehicle thermal management was established. The concept of coupling factor was proposed to provide the boundary conditions considering the thermal transmission interaction of multiple heat exchangers for the radiator module. Using the coupling factor, the thermal flow influence of the structural characteristics in the engine compartment was described with the lumped parameter method, thereby simplifying the space geometric feature numerical calculation. In this way, the coupling between the multiple thermodynamic systems mathematical model and multidimensional nonlinear CFD model was realized, thereby achieving the simulation and analysis of the integrated thermal management multilevel cooperative control process based on the underhood structure design. The research results indicated an excellent capability of the method for integrated control analysis, which contributed to solving the design, analysis, and optimization problems for vehicle thermal management. Compared to the traditional engine cooling mode, the NMPC thermal management scheme clearly behaved the better temperature controlling effects and the lower system energy consumption. The controller could further improve efficiency with reasonable coordination of the convective thermal transfer intensity between the liquid and air sides. In addition, the thermal transfer structures in the engine compartment could also be optimized. Full article

(This article belongs to the Special Issue Exergy Analysis and Optimization of Energy Systems and Processes)

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