International Journal of Exergy (13 papers in press)

Regular Issues

• Extreme Lean Hydrogen Combustion in SI Engines: NOX Emissions and Exergy Destruction Analysis  
  by Yasin Karagöz, Saban Pusat, Emre Teksan, Erdal Tunçer, Tugba Tetik 
  Abstract: This study examines the effects of excess air coefficient (?) and late ignition timing on NOx emissions and exergy destruction in a hydrogen-fueled internal combustion engine converted from a conventional diesel engine. Experiments are conducted at 1500 rpm and 3.5 kW using two ignition timings (10
  Keywords: Hydrogen; Extreme Lean Combustion; Cold Combustion; Exergy.
  DOI: 10.1504/IJEX.2026.10078328
   
  
• A Thermodynamic Evaluation of Carbon Capture and Storage with Exergy Aspects: A Critical Review  
  by Lekan Popoola, Festus Adeniyi Adeyemo, Lukumon Salami, Sunday Adekunle Adebanjo, Usman Taura, Yuli Panca Asmara, Kabir Adeola Aminu 
  Abstract: As part of the United Nation Sustainable Development Goals to attain low-carbon society, studies on ways of offsetting carbon are still imperative. This paper reviews the thermodynamics of carbon capture and storage (CCS) systems to understand the importance of CCS as a climate mitigation strategy and also explore the energy/ exergy requirements of the systems. Synergy between kinetic models and thermodynamic principles was explored to understand the mechanistic behavior of CO? transport and transformation in sorbent and storage media. Isotherm models, thermodynamic adsorption parameters, and implications for CO? sorbent design and regeneration efficiency were presented.
  Keywords: Low-carbon society; Environmental pollution; Greenhouse; Hazardous waste; Carbon offsetting.
  DOI: 10.1504/IJEX.2026.10078597
   
  
• Exergoeconomic assessment of coal-fired power plants.  
  by Murat Kaya 
  Abstract: Abstract. In this study, an exergoeconomic cost analysis was performed on a coal-fired power plant. The total capital investment cost of the plant comprises the fuel boiler boiler (?A), turbine (?B), electricity generator (?C) and condensation unit (?D). The unit energy costs of these systems were examined under varying parameters, specifically economic service life (ny), the annual electricity production period (t), and interest rate (IR). The boiler unit cost (c_2^?), as well as the turbine output and generator unit costs (c_3^?), were analyzed. The unit costs per unit of energy were calculated using the equality method (c_?feq^?, c_eleq^?) and the extraction method (c_?fex^?, c_elex^? ). The results indicate that per-unit costs decrease as the economic life (ny) and the annual electricity production period (t) increase. Conversely, per-unit costs increase as the interest rate (IR) rises. Predicting system costs in advance is crucial for designing more economical facilities and increasing efficiency
  Keywords: Exergy analysis; rancine cycle; steam power plant; exergoeconom?c.
  DOI: 10.1504/IJEX.2026.10079119
   
  
• Energy and Exergy Analysis for a Euro 6 class Diesel Engine under various Speeds and Loads  
  by Erman Aslan, Ak?m Hüseyin Yazan, Cengizhan Cengiz, Elif Ezgi Aytimur, ?eref Soylu 
  Abstract: This study investigates the thermal performance of a modern 2.0-L high-speed Euro 6 diesel engine widely used in passenger and light commercial vehicles. Experiments were conducted at engine speeds ranging from 1000 to 4500 rpm with 500 rpm increments and at three load conditions (60 Nm, 180 Nm, and 270 Nm), focusing on energy and exergy analyses. The results show that thermal efficiency exceeds 40% at 270 Nm within the 1500-2000 rpm range. Energy losses through exhaust and cooling systems account for approximately 2030%. Exergy analysis reveals that cooling-related losses remain below 2%, whereas exhaust exergy losses vary between 14% and 44%.
  Keywords: Diesel Engine; Energy; Exergy; Exhaust Losses; Cooling Losses.
  DOI: 10.1504/IJEX.2026.10079169
   
  
• Performance and sustainability assessment of a geothermal district heating and cooling system through energy and exergy analyses  
  by Ebru Hanc?o?lu, Arif Hepbasli 
  Abstract: A comprehensive thermodynamic analysis of a geothermal energy-supported heating and cooling system for a model building was presented in this study, employing energy, exergy, and sustainability evaluation methods. The heating and cooling systems achieved energy efficiencies of 0.81 and 0.47, respectively, while their corresponding exergy efficiencies were determined as 0.52 and 0.11. The coefficient of performance (COP) of the cooling system was calculated as 0.56. The results indicate that, in cooling mode, the condenser and absorber exhibit the greatest potential for performance and environmental improvement, whereas in heating mode, the heat exchanger (HE1) represents the principal component for enhancement.
  Keywords: geothermal district; geothermal cooling; energy analysis; exergy analysis; sustainability analysis.
  DOI: 10.1504/IJEX.2026.10079337
   
  
• Combustion-Zone Driven Irreversibility in a Heavy-Duty Diesel Engine under Injection Timing Variations  
  by Eihab A. Raouf 
  Abstract: The effect of injection timing on combustion-zone and thermodynamic irreversibility in a heavy-duty diesel engine was analysed. Simulations at 2,000 rpm across different loads showed that advancing injection shifted combustion toward top dead centre and increased the in-cylinder pressure rise rate. Peak cylinder pressure increased from about 58 to 62 bar at 25% load and from 105 to 114 bar at full load. The maximum pressure rise rate increased from 1.3 to 4.4 bar per crank-angle degree at low load and from 2.4 to 6.7 bar per degree at full load. Exergy analysis showed that 8-12 degrees before top dead centre (BTDC) provided the optimal balance between useful work and thermodynamic irreversibility. Injection timing shifts the combustion zone relative to top dead centre. Combustion-zone width varies strongly with engine load and injection timing. Advanced injection intensifies pressure development and heat transfer to cylinder walls. Exergy redistribution identifies an optimal injection range near SOI = 812 degrees BTDC. Combustion-zone evolution governs thermodynamic irreversibility in diesel engines.812
  Keywords: diesel engines; injection timing; combustion zone; exergy destruction; second law analysis.
  DOI: 10.1504/IJEX.2026.10079411
   
  
• Exergy-Based Four-Dimensional Sustainability Assessment of Energy Systems Integrating Entropy, Economy, and Environment: A Case Study of T  
  by Mert Ökten 
  Abstract: This study introduces the E4S index, a four-dimensional framework integrating exergy, entropy, economy and environment into a single dimensionless sustainability score (01). Applied to 14 energy technologies in Turkiye across four policy scenarios, the index employs Dirichlet-based Monte Carlo simulations to account for weighting uncertainty. Hydroelectric power achieves the highest score (E4S > 0.90) across all scenarios. The Environment First scenario yields the strongest alignment with UN sustainable development goals (R = 0.92), while the Economy First scenario diverges markedly (R = 0.18), demonstrating that cost-centric planning undermines long-term sustainability.
  Keywords: Energy Sustainability; E4S Index; UN SDG Validation; Monte Carlo Simulation; Energy Policy; Sustainable Development.
  DOI: 10.1504/IJEX.2026.10079731
   
  
• Exergy analysis of a Fresnel Lens integrated Flat Plate Collector  
  by Sunil Kumar, G.N. Tiwari, Madhu Sudan 
  Abstract: The primary goal is to enhance beam radiation with a top-mounted Fresnel lens, thereby improving energy and exergy performance. The energy balance for each component of the proposed system was derived in accordance with the first law of thermodynamics, forming the fundamental basis of the analysis. The impact of mass flow rate (m ?_f) and concentration ratio (C) on the rate of thermal, electrical, and overall energy and exergy produced by FLi-FPC-TEC has been evaluated. The proposed system achieved a maximum thermal gain of 1004 W and a peak electrical power output of 201 W under the operating conditions at (m ?_f=0.025kg/s, C=8, packing factor =1).
  Keywords: Flat plate collector (FPC); thermoelectric cooler; Fresnel lens; solar energy and Exergy.
  DOI: 10.1504/IJEX.2026.10079766
   
  
• Tray-by-Tray Exergy Analysis of the Stripper Column of the Catalytic-Conversion Unit of Abadan Refinery  
  by Morteza Yaghoobi, Ali Saeedi, Fatemeh Deymeh, Kazem Mokaffa 
  Abstract: Distillation columns are among the most energy-intensive units in refineries. This study presents a tray-by-tray exergy analysis of the catalytic-reforming stripper column at Abadan Oil Refinery under steady-state conditions using Aspen Plus v12. The feed tray, condenser, and reboiler were identified as the main sources of exergy destruction, accounting for 28%, 20-28%, and 15% of total losses, respectively. Sensitivity analysis showed that feed temperature and reflux flow have the greatest influence on exergy efficiency. Their simultaneous optimization reduced total exergy destruction by up to 34% and improved exergy efficiency by approximately 8.5%.
  Keywords: Exergy analysis; Stripper Column; Catalytic Reforming Unit; Aspen Plus; Exergy Destruction.
  DOI: 10.1504/IJEX.2026.10080065
   
  
• Metaheuristic Modelling of Exergy and Sustainability Parameters in High-Bypass Turbofan Engines: A Comparative Study of Cuckoo Search, PSO, and GA  
  by Ridvan Oruc 
  Abstract: This paper presents a comprehensive modeling approach to predict the exergy and sustainability parameters of high-bypass turbofan engines using the Cuckoo Search Algorithm (CSA), Particle Swarm Optimization (PSO), and Genetic Algorithm (GA). Engine data were obtained from the ICAO emissions databank. Exergy efficiency, wasted exergy ratio and environmental effect factor are modeled as functions of design variables such as bypass ratio and overall pressure ratio. The results show that all metaheuristic models provide satisfactory prediction accuracy, with the CSA-based model slightly superior in most cases. R? value greater than 0.92 for all methods indicates the robustness of the developed models.
  Keywords: Cuckoo search algorithm; particle swarm optimization; genetic algorithm; turbofan; exergy.
  DOI: 10.1504/IJEX.2026.10080109
   
  
• Exergy and Thermoeconomic Assessment of a Multifuel Engine-Driven ORC?VCR?District Water Heating System  
  by D. Manivannan, Shankar Ganesh Narayanan, A. R. Pradeep Kumar, T. Srinivas 
  Abstract: An integrated Organic Rankine Cycle?Vapor Compression Refrigeration?District Water Heating (ORC?VCR?DWH) system driven by a multifuel engine is analyzed using exergy and thermoeconomic methods. O-xylene, M-xylene, and ethylbenzene are evaluated under diesel, petrol, and biofuel operation at varying loads and compression ratios. O-xylene with biofuel achieves the highest ORC exergetic efficiency of 48.34% at 80% load, while the combined ORC?VCR efficiency reaches 44.7% at 150 ?C heat-source temperature. The turbine and high-temperature heat exchanger account for 50?55% of total exergy destruction. The evaporator exhibits the highest relative cost difference (~20%), indicating priority for thermoeconomic improvement.
  Keywords: Combined cycle; organic Rankine cycle; Vapor compression refrigeration; Energy and Exergy.
  DOI: 10.1504/IJEX.2026.10080139
   
  
• Exergy Analysis and Predictive Modelling of a Hybrid Solar Photovoltaic Thermoelectric Collector for Refrigeration Application  
  by Abhishek Tiwari, Shruti Agarwal 
  Abstract: This study investigates a hybrid solar collector integrating a semi-transparent photovoltaic (SPV) module and thermoelectric generator (TEG) coupled with a vapour absorption refrigeration (VAR) system. Five photovoltaic technologies, namely amorphous silicon (a-Si), polycrystalline silicon (poly-Si), monocrystalline silicon (mono-Si), cadmium telluride (CdTe), and copper indium gallium selenide (CIGS), were evaluated using a MATLAB-based simulation framework. System performance was analysed in terms of overall exergy output, overall exergy efficiency, and refrigeration coefficient of performance (COP). An equivalent multilayer perceptron artificial neural network (MLP-ANN) model achieved high predictive accuracy (mean squared error (MSE) = 0.088, correlation coefficient (R) = 0.999, mean bias error (MBE) = 0.2363, mean absolute percentage error (MAPE) = 1.89%). Poly-Si yielded the highest COP (0.92), while mono-Si achieved the maximum overall exergy efficiency (32.09%).
  Keywords: Artificial Neural Network; Hybrid System; Vapor Absorption Refrigeration System; Mean Squared Error; Thermal Modelling; Exergy Analysis.
  DOI: 10.1504/IJEX.2026.10080179
   
  
• Energy and Exergy Assessment of a Natural Gas-Fired Fire Tube Boiler with Humidity-Induced Heat Loss Identification  
  by Hablinur Al Kindi, Yogi Sirodz Gaoz, Qowiyu Haryo Bimoseno, Edi Sutoyo, Budi Hartnono 
  Abstract: This study evaluates the energy and exergy performance of a 4,000 kg/h natural gas-fired firetube boiler under real tropical industrial conditions in Bogor, Indonesia. Using the indirect heat-loss method, thermal efficiency was determined to be 88.97%, with total heat losses of 11.03% comprising ambient humidity-induced loss (4.83%), moisture from hydrogen combustion (4.03%), and dry flue gas loss (2.17%). Exergy analysis yielded an efficiency of 43.4%, with 56.6% of available work potential irreversibly destroyed through combustion and heat transfer processes. A component-level exergy destruction breakdown revealed that ambient humidity constitutes the dominant recoverable loss source ? a finding particularly significant in tropical operating environments. Improvement strategies including flue gas heat recovery, combustion air preheating, and inlet air dehumidification are recommended. This work addresses a gap in prior literature by systematically quantifying humidity-induced losses within a unified energy?exergy framework for natural gas fire-tube boilers.
  Keywords: fire tube boiler; exergy; energy efficiency; heat loss; combustion.
  DOI: 10.1504/IJEX.2026.10080256