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Abstract In this paper, the performance of a parallel two-stage compression (PTC) cycle on the domestic refrigerator-freezer in a laboratory according to the IEC 62552–2015 standard is investigated. The relatively large temperature difference between the fresh food compartment (FFC) and the refrigerant in the fresh food compartment evaporator (FFCE) leads to high compression and irreversible losses in the refrigeration circuit. To avoid the mentioned problems and reduce energy consumption, a PTC cycle is used. The innovation of this article is the 4E analyses (energy, exergy, exergoeconomic, exergoenvironmental) for the PTC cycle using the results obtained from the laboratory. Ultimately, the multi-objective optimization of the PTC cycle is conducted. For optimizing the PTC cycle, the total cost rate and the exergy efficiency are set as targets and the evaporator pressure and condenser pressure as variables. MATLAB and REFPROP 9.1 are used to model the system. Results showed that the highest exergy destruction rate is associated with the FFCE (0.349 kW) and compressor (0.183 kW). The highest exergy efficiency among the equipment is evaporators. The maximum exergoeconomic factor is related to the freezer compartment evaporator (FZCE) (98.70%) and then the compressor (98.62%). FZCE has the highest environmental impact (99.9%).

In recent years, there have been increasing concerns over the detrimental effects of irreversible linear patterns of material and energy consumption, which have led to an enormous generation of municipal solid waste (MSW). Concepts like waste-to-energy (WtE) and recycling have gained increasing recognition and support as responses to these challenges. This study assessed the exergetic potential of four WtE technologies (landfill gas-to-energy, anaerobic digestion, incineration, and plasma gasification) in the context of the MSW characteristics of Maiduguri, Borno State. The population of Maiduguri, waste generation rate, waste composition, and the ultimate and proximate analysis of the MSW were used for the assessment. Exergetic potential in the form of electrical energy generation and three exergy-based indicators (exergy efficiency, exergy defect, and improvement potential) were evaluated for each WtE option. The results reveal that anaerobic digestion and plasma gasification are viable options based on the exergetic potential and the measured exergy performance indicators. These findings offer valuable insights for policymakers and waste management authorities, facilitating informed decisions to address environmental concerns and promote resource-efficient urban development in Maiduguri and similar regions.

Synthetic refrigerants are being phased out gradually in accordance with international environmental protection protocols because of global warming and ozone layer depletion. Adopting R290/R600 refrigerant, an environmentally friendly refrigerant, to replace R134a, a high global warming potential refrigerant, provides one of the solutions. In this study, exergy analysis of R134a and TiO2 suspended with lubricant and R290/R600 with a composition of 60% R290 and 40% R600 (60:40) was investigated in vapour compression system (VCRS) using R290/ R600 in TiO2 nanomixture lubricant and compared with R134a and R290/ R600 in pure lubricant. At the inlets and outlets, the main components of the VCRS are connected to temperature and pressure sensors to measure the inlet and outlet temperatures and pressures. The results obtained were used to analyses the exergy losses at various VCRS components (compressor, condenser, evaporator, expansion valve) were investigated to determine the refrigerator’s total exergy destruction (E·xdest.Total) and efficiency (ηex). The E·xdest.Total of R290/R600 in pure lubricant and R290/R600 TiO2 nanomixture lubricant was reduced by 26.9% and 42.3%, respectively, and system ηex increased by 27.7% and 38.9% respectively when compared to R134a in the system. Hence, TiO2 suspended with R290/R600 is potential a substitute for R134a.

Background Heat induced by thermogenesis is an essential therapeutic intervention in medical practice. Moreover, thermogenesis improves the innate immune response. This study focuses on hand-clasping with a raised thumb (HCRT) as a thermogenic source and its effect on heart rate variability (HRV). Methods The study analyzed the ECG, thermal images of the upper body, axillary temperature, and breath exergy of 15 participants. The metabolic effect of thermogenesis is an important factor in type II diabetes mellitus (type II DM). Therefore, the clinical application included recording capillary blood glucose of 12 type-II DM subjects before and after the HCRT intervention. Results The mean axillary temperature slope increased by 11.5 %. The spatial change in temperature gradient (∇2T) at hot and cold spots also slightly increased by 3.42 % and 2.53 %, respectively. HRV improved as the VLFHF ratio decreased significantly (p < 0.05) by 52.62 %. The very low frequency (VLF) component of HRV has a relationship to thermoregulation, which is reflected through a significant increase (p < 0.05) of 41.7 % for the power under sub-VLF at 0.0327-0.04 Hz during HCRT. The spot width (SW), range, and norm of ∇2T reduces insignificantly during HCRT. There was a significant (p < 0.001) increase in the exhaled temperature by 0.5 ° C in both nostrils during 1st phase of HCRT. The standard deviation of exergy in the right nostril showed a significant increase (p < 0.05) of 72.72 % during HCRT. The Clinical tests showed a significant reduction (p < 0.001) of 24.14 % in capillary blood glucose (CBG) after HCRT. Conclusions HCRT aids in thermogenesis with higher exergy and HRV owing to a significant reduction in the VLFHF ratio.

The study involved the utilization of novel developed six distinct fuel, denoted as, PG5, PG10, PG15, PG20, PG25, and PG30 and G100 (pure gasoline). These fuels were derived from various blends of gasoline and phthalocyanines. Experimental investigations were conducted to assess the internal combustion engine's performance in terms of both energy and exergy. The mixtures underwent testing across a range of engine speeds, spanning from 1400 rpm to 3000 rpm. Notably, optimal performance across all fuels and engine speeds was consistently observed at 2600 rpm. In terms of energy and exergy efficiency assessments for all fuels and engine speeds, PG25 fuel demonstrated the highest efficiency levels, with 35% energy efficiency and 33% exergy efficiency at 2600 rpm. Conversely, G100 fuel exhibited the lowest energy and exergy efficiency at the same engine speed, registering values of 27% and 24%, respectively. Meanwhile, with regard to exhaust exergy, G100 fuel demonstrated the highest exhaust energy at 10.69 kW, occurring at 3000 rpm, whereas PG25 fuel exhibited the lowest exhaust exergy, measured at 3.09 kW. It has been observed that N2 gas, one of the exhaust components that affects the exergy of exhaust gases, affects the exhaust exergy to a large extent and this ratio is approximately 50%. In addition, the sustainability index value for all fuels was found to be at most 2600 rpm. It was calculated as 1.50 for PG25 fuel and 1.32 for G100 fuel. • The exergy of phthalocyanine as a fuel examined in internal combustion engines. • To increase efficiency of new fuels in the internal combustion engine. • The newly developed fuel has been shown to be more efficient than gasoline. [ABSTRACT FROM AUTHOR]

The process integration and electrification concept has significant potential to support the industrial transition to low- and net-zero-carbon process heating. This increasingly essential concept requires an expanded set of process analysis tools to fully comprehend the interplay of heat recovery and process electrification (e.g., heat pumping). In this paper, new Exergy Pinch Analysis tools and methods are proposed that can set lower bound work targets by acutely balancing process heat recovery and heat pumping. As part of the analysis, net energy and exergy load curves enable visualization of energy and exergy surpluses and deficits. As extensions to the grand composite curve in conventional Pinch Analysis, these curves enable examination of different pocket-cutting strategies, revealing their distinct impacts on heat, exergy, and work targets. Demonstrated via case studies on a spray dryer and an evaporator, the exergy analysis targets net shaft-work correctly. In the evaporator case study, the analysis points to the heat recovery pockets playing an essential role in reducing the work target by 25.7%. The findings offer substantial potential for improved industrial energy management, providing a robust framework for engineers to enhance industrial process and energy sustainability. [ABSTRACT FROM AUTHOR]

This paper presents the results of thermodynamic analysis applied to flat plate solar panels, incorporating both simulation studies and real system measurements in comparison. As solar thermal panels play a crucial role in sustainable energy solutions, analysis are essential for providing a detailed and accurate assessment of their performance. Thermodynamic tools like energy and exergy analyses can be used to evaluate and enhance the performance of solar thermal generation systems. Their usage can help identify the components and processes with the greatest potential for improvement, mainly in the design or exploitation phase. Exergetic analysis, in particular, reveals the true extent of losses, as demonstrated by energy and exergy analyses of various thermal power plants with different capacities. Exergy analysis provides a more accurate performance evaluation and is a valuable method for assessing and comparing potential configurations of these systems. [ABSTRACT FROM AUTHOR]

Recovering compression waste heat using latent thermal energy storage (LTES) is a promising method to enhance the round-trip efficiency of compressed air energy storage (CAES) systems. In this study, a systematic thermodynamic model coupled with a concentric diffusion heat transfer model of the cylindrical packed-bed LTES is established for a CAES system, and the numerical simulation model is validated by experimental data in the reference. Based on the numerical model, the charging–discharging performance of LTES and CAES systems is evaluated under different layouts of phase change materials (PCMs) in LTES, and the optimal layout of PCM is specified as a three-stage layout, since the exergy efficiency of LTES and round-trip efficiency are improved by 8.2% and 6.9% compared with a one-stage layout. Then, the proportion of three PCMs is optimized using response surface methods. The optimization results indicate that the exergy efficiency of LTES and round-trip efficiency of the CAES system are expected to be 80.9% and 73.3% under the PCM proportion of 0.48:0.3:0.22 for three stages, which are 7.0% and 13.1% higher than the original three-stage PCMs with equal proportions. [ABSTRACT FROM AUTHOR]

This study examines the thermodynamic and numerical analyses of a methane-fed solid oxide fuel cell (SOFC) over a temperature range varying between 873 K and 1273 K. These analyses were conducted to investigate and compare the performance of the SOFC under various operating conditions in detail. As part of the thermodynamic analysis, important parameters such as cell voltage, power density, exergy destruction, entropy generation, thermal efficiency, and exergy efficiency were calculated. These calculations were used to conduct energy and exergy analyses of the cell. According to the findings, an increase in operating temperature led to a significant improvement in performance. At the initial conditions where the SOFC operated at a temperature of 1073 K and a current density of 9000 A/m2, it was observed that when the temperature increased by 200 K while keeping the current density constant, the power density increased by a factor of 1.90 compared to the initial state, and the thermal efficiency increased by a factor of 1.45. Under a constant current density, the voltage and power density values were 1.0081 V, 1.0543 V, 2337.13 W/m2, and 2554.72 W/m2 at operating temperatures of 1073 K and 1273 K, respectively. Under a current density of 4500 A/m2, the entropy generation in the cell was determined to be 29.48 kW/K at 973 K and 23.68 kW/K at 1173 K operating temperatures. The maximum exergy efficiency of the SOFC was calculated to be 41.67% at a working temperature of 1273 K and a current density of 1500 A/m2. This study is anticipated to be highly significant, as it examines the impact of temperature variation on exergy analysis in SOFC, validating both numerical and theoretical results, thus providing a crucial roadmap for determining optimized operating conditions. [ABSTRACT FROM AUTHOR]

The use of agro-industrial and urban organic waste to produce energy seems to be one of the most attractive options for the future of energy supply. Anaerobic digestion is a promising process for treating organic waste and producing biogas. Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide, and hydrogen sulfide, that can be used for electrical and thermal energy generation or as fuel. However, it is still necessary to improve the technology associated with its production, adapting it to an efficient, safe, and competitive scale. Various methodologies are used to support the decision on process parameters and operating conditions to find the most effective and sustainable ones. In this study, an exergy analysis was performed to determine the exergetic efficiency and exergy destruction in the biogas process produced from the anaerobic digestion of vinasse. The analysis was performed through mass, energy, and exergy balances using literature data and computer simulation and considering the use of a continuous stirred tank reactor. The results show that the exergy destroyed in the CSTR biodigester was 1338.9 kW, accounting for 57.2% of the overall exergy destruction in the process. The heat exchanger showed the highest exergy efficiency (99.95%), with only 5.77 kW of exergy being destroyed. The authors suggest for future works that it would be interesting to perform a life cycle assessment (LCA) and exergoeconomic analysis to evaluate the environmental and economic impacts associated with biogas production from the anaerobic digestion of sugarcane vinasse. [ABSTRACT FROM AUTHOR]

This work focuses on the structure, working, and testing of a new mixed solar cooker using a linear Fresnel collector, evacuated tube and box‐type cooker. The low‐cost components used in the construction of this cooker can help it satisfy the needs of both urban and rural inhabitants who need steady cooking temperatures above 140°C. A family of five can prepare four meals using this modified solar cooker, which costs about $250. The designed solar cooker was tested by conducting no‐load and full‐load tests. For the no‐load test, the maximum temperature of the absorber plate and oil for the new mixed cooker was recorded as 160.26°C and 172.72°C, respectively. The absorber plate of the new mixed cooker and its oil both reached their highest temperatures during the full‐load test at 141.14°C and 157°C, respectively. The energy efficiency of the new cooker is 58.776%, while its exergy efficiency is 13%. The heat transfer coefficient increased to 100.16 W/m² °C. This cooker provides an additional time savings of 60 min. An improvement of 27.5% in the highest temperature reached was seen when the developed cooker's performance was compared with those reported in the literature. Additionally, the new cooker's heat‐storing capability enables up to 3 h of autonomy. The Levelized Cost of Cooking a Meal for the innovative mixed solar cooker is $0.034 per meal. [ABSTRACT FROM AUTHOR]

Al-Khirat gas power plant in Iraq experiences significant reductions in power output and efficiency during the hot and dry summer season as an effect of a decrease in air mass flow rate resulting from rising ambient temperatures. To address this issue, upstream cooling systems are implemented and their performance is evaluated through energy and exergy analysis. This study tends to do a comparative study of a gas turbine performance with and without upstream cooling systems with power output, thermal efficiency, exergy efficiency, specific fuel feeding, consumed fuel mass flow rate, and exergy destruction rates. The findings show that upstream cooling systems (UPCS) can effectively mitigate the negative effects of high ambient temperatures on gas turbine performance, especially in Iraq's hot, dry summers. Our study found that higher air temperatures led to a significant drop in gas turbine efficiency, with a 35 K increase in inlet air temperature reducing power production by 27.4%. However, implementing UPCS increased thermal efficiency by 11.5% and exergy efficiency by 11.2%. [ABSTRACT FROM AUTHOR]

In the present investigation, thermodynamic/eco/environmental analysis of the relationship between time-dependent particle deposition and thermal-based losses and incident solar radiation intensity on the PV front cover glass during the months with the least precipitation in the city of Samsun (Turkey) was performed. To evaluate the effect of dust accumulation, controlled experiments were carried out where the surface of one set of PV panels was periodically cleaned with water and the other one was left to natural contamination. The results showed that over three months, the difference in energy loss rates between cleaned and uncleaned PV arrays ranged from 2.53% to 8.1%, with the exergy efficiency difference measured at 1.3%–2.44%. According to the energy-based analyzes, August was the most effective month, with cleaned PV arrays reducing CO2 emissions by 401.5 kg and saving $6.02, compared to uncleaned PV arrays which reduced emissions by 362.21 kg and cost $5.43, respectively. Similarly, in the exergy-based evaluation, August was the most efficient month, with cleaned PV arrays decreasing CO2 emissions by 401.5 kg and saving $6.02, compared to uncleaned PV arrays, which dropped CO2 emissions by 362.21 kg and costing $5.43, respectively. While the cleaned surfaces were initially positive, a decrease was observed over time. However, the efficiency of PV decreased with increasing panel temperature. The study concludes that PV surfaces need to be cleaned at certain intervals, depending on the location's weather conditions. [ABSTRACT FROM AUTHOR]

To enhance the overall performance of recompression supercritical carbon dioxide- (sCO2-) based systems, two new double-effect absorption reheat power cycles (DARPC) were developed in this study. These methods are based on the typical absorption power cycle (APC). For the proposed sCO2/DARPC systems, a parametric analysis of the thermodynamic and economic performances, as well as additional parametric optimisations, were performed quantitatively. The results indicate that replacing the APC subsystem with DARPC subsystems can enhance the total function of the sCO2 system even further, owing to the increased H2O vapour created in the separator and the reheating process, which adds to the greater net power output. Furthermore, compared to the DARPC2 subsystem, the DARPC1 subsystem may produce more H2O vapour from the generator and separator, resulting in an increase in net output power. When compared to a single sCO2 power cycle, multiobjective optimisations showed that the sCO2/DARPC1 and sCO2/DARPC2 systems could increase the exergy efficiency by 12.95% and 11.51% and decrease the total product unit cost by 9.67% and 8.37%, respectively. Furthermore, the sCO2/DARPC1 and sCO2/DARPC2 systems can achieve improvements in exergy efficiency of 4.95% and 3.61% and a total product unit cost of 4.52% and 3.15%, respectively, compared with the sCO2/APC system. [ABSTRACT FROM AUTHOR]

In this article, the energy, exergy, and economic analysis of an organic Rankine cycle (ORC) system powered by biogas to provide electricity, heating, and cooling loads for a residential building in Munich city is investigated. Two methods have been proposed to meet the heating and cooling needs of the residential building. In the first method, heating and cooling needs are provided by a heat pump and mechanical refrigeration (System I), and in the second method, these needs are provided by a radiator and absorption refrigeration cycle (System II). In both modes of this system, the effects of battery energy storage (BES) have been analyzed for peak shaving. The working method of this research is that the residential building's electricity, heating, and cooling needs are calculated by Homer and Carrier software, respectively. Engineering equation solver software models the main local power generation system. A new method has been proposed to select the required number of units to meet the needs of the building with and without BES. The results showed that for System I with and without BES, 3 and 1 ORC units with a nominal power of 2 kW can meet all the needs of the building, respectively. In contrast, for System II, the number of 1 unit with 2 kW and 1 unit with 1 kW is needed to meet the energy needs of a residential building with and without BES. It can be concluded that heating and cooling the building with a radiator and absorption chiller cycle is more cost‐effective. The energy and exergy efficiency of ORC is reported as 11.3% and 65.7%, respectively, and the highest exergy destruction rate is related to the heater and boiler. From the economic point of view, the payback period of System II compared with System I is reduced from 18.4 to 5.66 years without using BES. With the use of BES, the payback period is reduced to 5.3 and 5.66 years, respectively. The lowest and highest electricity prices belong to System I with and without BES, which are 3.11 and 0.36 US$/kWh, respectively. [ABSTRACT FROM AUTHOR]

In this research, the simulation of an existing 31.5 MW steam power plant, providing both electricity for the national grid and hot utility for the related sugar factory, was performed by means of ProSimPlus® v. 3.7.6. The purpose of this study is to analyze the steam turbine operating parameters by means of the exergy concept with a pinch-based technique in order to assess the overall energy performance and losses that occur in the power plant. The combined pinch and exergy analysis (CPEA) initially focuses on the depiction of the hot and cold composite curves (HCCCs) of the steam cycle to evaluate the energy and exergy requirements. Based on the minimal approach temperature difference (∆Tlm) required for effective heat transfer, the exergy loss that raises the heat demand (heat duty) for power generation can be quantitatively assessed. The exergy composite curves focus on the potential for fuel saving throughout the cycle with respect to three possible operating modes and evaluates opportunities for heat pumping in the process. Well-established tools, such as balanced exergy composite curves, are used to visualize exergy losses in each process unit and utility heat exchangers. The outcome of the combined exergy–pinch analysis reveals that energy savings of up to 83.44 MW may be realized by lowering exergy destruction in the cogeneration plant according to the operating scenario. [ABSTRACT FROM AUTHOR]

The process of phasing out of medium and high global warming potential refrigerants is accelerating in all areas of refrigeration, particularly since the European F-Gas Regulation No. 517/2014 and the ensuing Kigali amendment went into effect. Hydrocarbon refrigerants are being considered as suitable alternatives due to their low global warming potential and excellent thermal properties, but due to their flammability, safety precautions must be followed. This theoretical study contributes to the evaluation of the thermal and environmental impact of hydrocarbon refrigerants as drop-in alternatives to R134a in domestic refrigerator. In order to conduct an analysis of energy, exergy, and environmental factors, R134a and all hydrocarbons refrigerants proposed by ASHRAE--R290, R600, R600a, R601, R601a, and R1270--were examined as operating fluids used in a domestic refrigerator with a cooling capacity of 157 W and constant condenser temperature of 40°C and variable evaporator temperature every 5°C between -5 and -30°C. The results revealed that all the alternative refrigerants except R601 and R601a have higher thermal and environmental performance than R134a and can be used after refrigerator compressor replacement. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the performance of a simple cycle gas turbine power plant by analysing the effect of different operating parameters. These operating parameters include compressor pressure ratio and compressor & turbine isentropic efficiencies. The study quantitatively assesses the exergetic efficiency and the exergy destruction of each unit in the cycle, as well as the power used or produced by the cycle. Any change in these parameters can significantly impact the power plant's overall performance through a specific unit in the cycle. For instance, increasing the compressor pressure ratio can reduce the temperature difference across the combustor, lessening the exergy destruction and improving the cycle’s overall performance. However, any decline in the compressor or the turbine isentropic efficiency results in an increase in the exergy destruction of the affected unit and can result in a decrease in the overall cycle performance. This is due to either an increase in power required by the compressor or a decrease in power produced by the turbine. The analysis suggests that the turbine isentropic efficiency has a greater impact on the net power generated than the compressor isentropic efficiency. Additionally, the turbine inlet temperature is a dependent variable as operating at different compressor pressure ratios and compressor isentropic efficiencies lead to varying turbine inlet temperatures. Therefore, increasing the turbine inlet temperature does not always lead to improved performance. [ABSTRACT FROM AUTHOR]

This study investigates the comparative effects of carboxyl-functionalized multi-walled carbon nanotube (MWCNT)/water nanofluids and titanium dioxide (TiO2) /water nanofluids in direct absorption parabolic solar collectors. To achieve this, a standard testing apparatus was constructed, and the thermal and exergy efficiencies of the collector were calculated using nanofluids at various concentrations. UV/Vis analysis was used to analyze the radiative properties of the nanofluids, and their thermal conductivity was also measured. Experiments were conducted under laminar flow conditions with flow rates of 20, 60, and 100 liters per hour and inlet temperatures of 20, 30, and 40 °C under real conditions with direct solar irradiation. The highest thermal efficiency recorded for the carbon-based nanofluid was 44.96%, while the titanium-based nanofluid achieved a thermal efficiency of 34.98%. Given the substantial improvement in efficiency compared to the base fluid (distilled water), the combined effect of using both nanofluids was also examined, resulting in a maximum thermal efficiency of 48.77%. The exergy efficiency at the highest flow rate and inlet temperature for the base fluid, TiO2 nanofluid, MWCNT nanofluid, and the hybrid nanofluid were 2.61%, 4.98%, 6.68%, and 7.26%, respectively. The pressure drop of all nanofluids in the absorber tube ranged from 5 to 39.6 Pascals. The studied nanofluids enhance the thermal performance of the system and create low pressure drop, indicating their high efficiency in direct absorption solar collectors. [ABSTRACT FROM AUTHOR]

Steam power generation is one of the most important energy productions in the world and needs to be improved to reduce the greenhouse effect while increasing electricity production. This paper deals with the energy, exergy, and exergoeconomic analysis of a steam-generating solar power plant. A general methodology is presented to define and calculate the exergy efficiency, exergy destruction, exergoeconomic factors, total costs, improvement potentials, and exergy costs in thermal systems. The methodology is based on a specific exergy cost approach and a sensitivity cost analysis. The thermodynamic properties of the working fluid are determined using THERMAX and MATLAB software packages. For the considered normal operating and economic conditions, the percentage of exergy destruction relative to the total exergy destruction and potential improvement of the boiler was found to be the highest at 86% and 85.3%, respectively. The exergoeconomic coefficient of the system is calculated with a value of 0.52. The total cost of exergy losses is $5939.6 per hour. Furthermore, the results of the solar direct evaporation analysis show that the behavior of the exergoeconomic coefficient in January and July was calculated with values of 0.64 and 0.34, respectively. The total costs are $3010.4 and $5480 per hour, respectively. Obtaining specific values and clear parameter influences is a valuable achievement and helps field engineers and operators effectively perform their individual tasks while taking into account the conflicts between energy consumption, exergy and costs. [ABSTRACT FROM AUTHOR]

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Internal combustion engine energy and exergy analysis is essential when choosing a biofuel that can be used as an alternative to conventional diesel, as these analyses provide concerns about the quantity and quality of available energy. In this study, the multiple injection strategies (MIS) in an improved common rail direct injection (CRDI) diesel engine running on 20% blend of Congress grass Tamarind shell co-pyrolysis oil (CGTSCPO20) and diesel is optimized and energy and exergy analysis has been made at optimized condition. The optimal result reveals that there was a slight improvement in brake thermal efficiency (BTE) and reduction in emissions. By increasing the IOP from 600 bar to 1100 bar with the same fuel IT of 10° bTDC, the performance is enhanced. Studies reveal that, apart from nitrogen oxides (NOx), emissions decrease under ideal circumstances of 80% load and 1000 bar pressure when brake thermal efficiency (BTE) increases. From the experimental results, it was observed that destruction of exergy for CGTSCPO20 and diesel were 59:24% and 50:17%, respectively. [ABSTRACT FROM AUTHOR]

In the industrial sector, efficient production and optimal use of thermal energy are primary concerns for managers and engineers. Considerable research has been devoted to improving and promoting thermal energy efficiency, especially energy recovery in the context of sustainability. Pinch analysis is one of the most powerful methods in this regard. To maximise the energy recovery (MER), the pinch method is well-established in designing an optimal heat exchange network (HEN). Exergy analysis is combined with the pinch method to minimise the work potential loss (exergy loss) while ensuring maximum heat recovery. This study presents a generic algorithm built using Python language to predict and quantify energy and exergy targets in industrial processes. It provides a framework to guide experts and planners in efficiently using the combined analysis tools. The generic algorithm is based on advanced numerical and graphical tools. It provides exergy problem table algorithm (Ex–PTA) and grand composite curve (EHR and HRP) tools. For Δ T min = 10°C, the generic algorithm is implemented in a building complex case study. The energy targets for heating and cooling requirements are 316.2625 kW and 0 kW, respectively. The obtained exergy targets are less attractive given an improvement from advanced utility integration; this is due to the treated system (medium-temperature system) and not to the reliability and efficiency of the generic algorithm. To evaluate the generic algorithm calculations, they are executed in a low-temperature process in which pinch exergy analysis (PExA) has already been performed. The simulated and generated results are identical, demonstrating the reliability and effectiveness of the developed generic algorithm. [ABSTRACT FROM AUTHOR]

Gas sweetening with an aqueous solution of diethanolamine is a crucial and common process in natural gas processing. However, the process, particularly in the solvent regeneration section, consumes a substantial amount of energy, significantly escalating the cost of gas. This paper presents a simulation and optimization of an existing natural gas refinery plant using a lean vapor compression method. The simulation results indicate that the current process requires 2.73 GJ/tacid gas for solvent regeneration, with exergy destruction of 14,120.59 kW in the solvent regeneration section. The total annualized cost for the current process is 11.68 M$. A modified scheme is proposed to address the issue of high energy consumption and the associated costs. The proposed scheme demonstrates significant improvements in the aforementioned parameters. Specifically, energy for solvent regeneration, exergy destruction in the solvent regeneration section, total annualized cost, and cost of gas are reduced by 16.12 %, 25.04 %, 20.97 %, and 20 % compared to the current process, respectively. These improvements enhance the thermoeconomic indexes, making the proposed scheme a viable and cost-effective alternative to the current process. [ABSTRACT FROM AUTHOR]

Qualtra, an innovative 10 MW geothermal power plant proposal, employs a closed-loop design to mitigate emissions, ensuring no direct release into the atmosphere. A thorough assessment utilizing energy and exergy analysis, life cycle assessment (LCA), exergo-economic analysis, and exergo environmental analysis (EevA) was conducted. The LCA results, utilizing the ReCiPe 2016 midpoint methodology, encompass all the spectrum of environmental indicators provided. The technology implemented makes it possible to avoid direct atmospheric emissions from the Qualtra plant, so the environmental impact is mainly due to indirect emissions over the life cycle. The result obtained for the global warming potential indicator is about 6.6 g CO2 eq/kWh, notably lower compared to other conventional systems. Contribution analysis reveals that the construction phase dominates, accounting for over 90% of the impact for almost all LCA midpoint categories, excluding stratospheric ozone depletion, which is dominated by the impact from the operation and maintenance phase, at about 87%. Endpoint indicators were assessed to estimate the single score value using normalization and weighting at the component level. The resulting single score is then used in an Exergo-Environmental Analysis (EEvA), highlighting the well system as the most impactful contributor, constituting approximately 45% of the total impact. Other substantial contributions to the environmental impact include the condenser (21%), the turbine (17%), and the HEGeo (14%). The exergo-economic analysis assesses cost distribution across major plant components, projecting an electricity cost of about 9.4 c€/kWh. [ABSTRACT FROM AUTHOR]

The utilization of waste heat from power plants, which is generally lost to the atmosphere, can reduce energy wastage significantly. Heat recovery systems are necessary for power plants to utilize the waste heat, which improves overall efficiency and reduces the need for additional fossil fuel consumption and its associated carbon emissions. This study uses the organic rankine cycle (ORC) to recover waste heat from the flue gas exhaust of an integrated gasification combined cycle (IGCC) power plant. A detailed thermodynamic analysis is conducted to study the outcomes from a 400 MWe IGCC plant and IGCC integrated with ORC. The IGCC plant is a reconfigured 400 MWe pressurized pulverized combined cycle power plant. The ORC uses R245fa as its working fluid, and high-ash Indian coal is used as a fuel input for the IGCC plant. The modelling and simulation of different plant configurations have been done using the software "Cycle-Tempo". The thermodynamic analysis reveals that the IGCC plant has energy and exergy efficiencies of 45.50% and 41.62%, respectively, and the IGCC-ORC plant has energy and exergy efficiencies of 45.84% and 41.92%, respectively. This study also shows that the combustion chamber and cooling water system in condenser experience maximum exergy and energy losses. Moreover, the ORC produces a net additional power output of 2.34 MWe with energy and exergy efficiencies of 12.48% and 42.54%, respectively. This additional power generation helps in avoiding around 51 tonnes/day of CO2 when similar amount of power is produced from a coal-based thermal power plant. [ABSTRACT FROM AUTHOR]

The hybrid energy storage system of wind power involves the deep coupling of heterogeneous energy such as electricity and heat. Exergy as a dual physical quantity that takes into account both 'quantity' and 'quality, plays an important guiding role in the unification of heterogeneous energy. In this paper, the operation characteristics of the system are related to the energy quality, and the operation strategy of the wind power hybrid energy storage system is proposed based on the exergoeconomics. First, the mathematical model of wind power hybrid energy storage system is established based on exergoeconomics. Then, wind power experiments of three forms of thermal-electric hybrid energy storage are carried out, and RSM is used to analyze the power quality and exergoeconomic characteristics of the system, and the optimal working conditions of the experiment are obtained. Finally, an optimization strategy is proposed by combining experiment and simulation. The system efficiency, unit exergy cost and current harmonic distortion rate are multi-objective optimization functions. The three algorithms evaluate the optimal solution based on standard deviation. The results show that the exergoeconomics can effectively judge the production-storage-use characteristics of the new system of ' wind power + energy storage'. The thermal-electric hybrid energy storage system can absorb the internal exergy loss of the battery, increase the exergy efficiency by 10%, reduce the unit exergy cost by 0.03 yuan/KJ, and reduce the current harmonic distortion rate by 8%. It provides guidance for improving the power quality of wind power system, improving the exergy efficiency of thermal-electric hybrid energy storage wind power system and reducing the unit cost. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a parallel two-stage compression (PTC) cycle on the domestic refrigerator-freezer in a laboratory according to the IEC 62552–2015 standard is investigated. The relatively large temperature difference between the fresh food compartment (FFC) and the refrigerant in the fresh food compartment evaporator (FFCE) leads to high compression and irreversible losses in the refrigeration circuit. To avoid the mentioned problems and reduce energy consumption, a PTC cycle is used. The innovation of this article is the 4E analyses (energy, exergy, exergoeconomic, exergoenvironmental) for the PTC cycle using the results obtained from the laboratory. Ultimately, the multi-objective optimization of the PTC cycle is conducted. For optimizing the PTC cycle, the total cost rate and the exergy efficiency are set as targets and the evaporator pressure and condenser pressure as variables. MATLAB and REFPROP 9.1 are used to model the system. Results showed that the highest exergy destruction rate is associated with the FFCE (0.349 kW) and compressor (0.183 kW). The highest exergy efficiency among the equipment is evaporators. The maximum exergoeconomic factor is related to the freezer compartment evaporator (FZCE) (98.70%) and then the compressor (98.62%). FZCE has the highest environmental impact (99.9%). [ABSTRACT FROM AUTHOR]

To assess the electricity cogeneration potential in the Minas Gerais cement industry with thermodynamic cycles is the main purpose of this study. The potential was estimated based on Minas Gerais cement sector data. The Kalina cycle, the organic Rankine cycle, and the conventional Rankine cycle were technically and economically assessed. The technical evaluation considered the thermodynamic modeling with optimization including the mass, energy, entropy, and exergy balances and the heat transfer calculations for heat exchangers. The economic evaluation considered the economic modeling including the calculation of electric power generated specific cost, the total investment, cash flow, and payback. The result shows that the greatest irreversibilities are concentrated in the turbines and evaporators. The Kalina cycle confirmed more generated power and exergetic efficiency, but in terms of thermal efficiency, the values were very similar between the cycles. The three cycles can cover more than 35% of the energy demand, which means a considerable reduction in cement manufacturing costs. All cycles reveal a payback value lower than 3 years, a considerable value of cash flow, and high competitiveness in the current tariff scenario. The electricity cogeneration potential in the Minas Gerais cement industry is near 100MW, and it is in the south-central region of Minas Gerais, where there is a greater population and energy demand concentration. This potential could save emissions of around 282,913 tCO2/year. [ABSTRACT FROM AUTHOR]

Present paper aims to investigate effects of nanoparticle addition to thermal oil of parabolic trough collectors which are integrated to Kalina cycle for electricity generation to run an alkaline electrolyzer for hydrogen production. Thermodynamic models for Kalina cycle, thermal model for parabolic collectors and electrochemical models for water electrolyzer are developed for overall plant modeling. Three types of nanoparticles including: copper oxide, alumina and titanium oxide are considered and overall plant performance is investigated using these nanoparticles and is compared with basefluid. The nanofluid thermophysical properties are evaluated as a function of nanoparticles' properties, volume fraction and the base fluid properties. The effects of key variables such as nanoparticle volume fraction, collector inlet temperature, evaporation pressure and ammonia concentration of Kalina system were evaluated on hydrogen production as well as exergetic efficiencies. Results revealed greater positive influence for CuO compared to TiO 2 and Al 2 O 3 on performance improvement for both hydrogen generation and its exergetic efficiency. Also, compared to basefluid (without nanoparticles) case, it was found that CuO particles result in a solar-to-H 2 exergy efficiency improvement by 4.7%. Using this nanofluid with a volume fraction of 5%, the H 2 production rate enhances from 0.633 kg / h to 0.664 kg / h , indicating 4.9 % improvement. • An alkaline electrolyzer-based hydrogen production plant powered by PTC is modeled. • Three types of nanoparticles are employed for hydrogen production enhancement. • Copper oxide nanoparticles are found to be better than titanium oxide and alumina. • Nanoparticles are applied to enhance the PTC thermal performance. • Hydrogen production rate can be enhanced by 4.9 % using CuO nanoparticles. [ABSTRACT FROM AUTHOR]

Effective decarbonization of the power generation sector requires a multi-pronged approach, including the implementation of CO2 capture and storage (CCS) technologies. The Graz cycle features oxy-combustion CO2 capture in a power production scheme which can result in higher thermal efficiencies than that of a combined cycle. However, the auxiliary consumption required by the air separation unit to provide pure O2 results in a significant energy penalty relative to an unabated plant. In order to mitigate this penalty, the present study explores the possibility of chemical looping combustion (CLC) as an alternative means to supply oxygen for conversion of the fuel. For a midscale power plant, despite reducing the levelized cost of electricity (LCOE) by approximately 12.6% at a CO2 tax of EUR 100/ton and a natural gas price of EUR 6.5/GJ and eliminating the energy penalty of CCS relative to an unabated combined cycle, the cost reductions of CLC in the Graz cycle were not compelling relative to commercially available post-combustion CO2 capture with amines. Although the central assumptions yielded a 3% lower cost for the Graz-CLC cycle, an uncertainty quantification study revealed an 85.3% overlap in the interquartile LCOE range with that of the amine benchmark, indicating that the potential economic benefit is small compared to the uncertainty of the assessment. Thus, this study indicates that the potential of CLC in gas-fired power production is limited, even when considering highly efficient advanced configurations like the Graz cycle. [ABSTRACT FROM AUTHOR]

The helium cryo-plant is an indispensable subsystem for the application of low temperature superconductors in large-scale scientific facilities. However, it is important to note that the cryo-plant requires stable operation and consumes a substantial amount of electrical power for its operation. Additionally, the construction of the cryo-plant incurs significant economic costs. To achieve the necessary cooling capacity while reducing power consumption and ensuring stability and economic feasibility, constrained multi-objective optimization is performed using the interior point method in this work. The Collins cycle, which uses liquid nitrogen precooling, is selected as the representative helium liquefaction cycle for optimization. The discharge pressure of the compressor, flow ratio of turbines, and effectiveness of heat exchangers are taken as decision parameters. Two objective parameters, cycle exergy efficiency, ηex,cycle, and liquefaction rate, ṁL, are chosen, and the wheel tip speed of turbines and UA of heat exchangers are selected as stability and economic cost constraints, respectively. The technique for order of preference by similarity to the ideal solution (TOPSIS) is utilized to select the final optimal solution from the Pareto frontier of constrained multi-objective optimization. Compared to the constrained optimization of ηex,cycle, the TOPSIS result increases the ṁL by 23.674%, but there is an 8.162% reduction in ηex,cycle. Similarly, compared to the constrained optimization of ṁL, the TOPSIS result increases the ηex,cycle by 57.333%, but a 10.821% reduction in ṁL is observed. This approach enables the design of helium cryo-plants with considerations for cooling capacity, exergy efficiency, economic cost, and stability. Furthermore, the wheel tip speed and UA of heat exchangers of the solutions in the Pareto frontier are also studied. [ABSTRACT FROM AUTHOR]

A new power and refrigeration cycle is examined in the present study. The system proposed is a combination of organic Rankine cycle (ORC) and an ejector refrigeration cycle (ERC). An ERC is introduced into the ORC to recover heat from partial expansion of the ORC fluid. The heat recovery is enhanced with the incorporation of recuperator, evaporator and superheater as heat exchangers. Among the various working fluids opted for, R245fa and R236ea have been considered in the present work. The properties of the combined cycle state points are evaluated through Engineering Equation Solver (EES) software. The impact of decision variables (such as hot source temperature, turbine expansion ratio, extraction ratio, and separator temperature) on performance parameters (such as exergy destruction, energy efficiency of power generation, exergy efficiency of power generation, energy efficiency of combined system, exergy efficiency of combined system, COP, and cooling power ratio) is examined and reported. The series heater configuration in ORC has improved system performance by recovering waste heat more effectively. At the same parametric conditions, the energy and exergy performances of R245fa are higher than those of R236ea. [ABSTRACT FROM AUTHOR]

The use of renewable energy sources to maintain appropriate thermal humidity and temperature conditions in food drying technologies, especially in humid climate zones, is a current area of research. In the Eastern Black Sea Region, the high relative and specific humidity of the atmospheric air lead to a low drying rate of the products. Therefore, in this study, to enhance the drying rate of the products, three models and their psychometric cycles were studied on decreasing the specific humidity of the drying air and increasing the moisture saturation degree of the drying air. The innovative hazelnut drying models proposed for the climatic conditions of the Eastern Black Sea region incorporate several components, including thermoelectric modules (TEM), photovoltaic thermal (PV/T) systems, desiccant wheels (DW), heat pipes (HP) and heat exchangers (HX). The thermodynamic analysis was conducted on the theoretical cycles belonging proposed models. Emphasis was given to the development of Model-C, taking into account the drying conditions specific to hazelnuts in the Eastern Black Sea region, among the cycles named Model-A, Model-B and Model-C. The energy efficiencies and SEMER values of Model-A, Model-B and Model-C were presented based on selected atmospheric conditions. Each model is valid under its characteristic operating conditions, and the energy efficiencies, SEMER values and the exergetic efficiencies for Model-A, Model-B and Model-C were determined as (4.66%-0.271 kg-H2O kWh−1–62%), (9.87%-0.1542 kg-H2O kWh−1–22%) and (9.13%-0.1381 kg-H2O kWh−1–10%), respectively. Also, presented models of hazelnut drying supported by renewable energy have achieved high sustainable index (SI) values. Consequently, these models ensure the sustainability of energy in the drying sector and facilitate the assessment of their environmental, economic and social impacts. The utilization of renewable energy in the models will lead to a reduction in CO2 emissions during the drying process. These results indicate that TEM systems are a viable option for food drying in the future. [ABSTRACT FROM AUTHOR]

Double-pipe helical heat exchangers (DPHHXs) are widely used for cooling and heating applications. In this study, a combination of two methods is used to enhance the performance of DPHHX. The thermal–hydraulic performance is investigated using a nanofluid of silicon dioxide and water (SiO2/water) as well as spring wire insert (SWI) experimentally and numerically. The numerical model is validated with the experimental results. The parameters such as Nusselt number, pressure drop, exergy efficiency, and thermal–hydraulic enhancement factor are investigated for Reynolds number range from 4500 to 7000. The results show the Nusselt number is enhanced with nanofluid employment and SWI. Nusselt number increases by 34% when 0.1% volume concentration of nanofluid is used and by 43.5% when spring wire is only used compared to base water. The configuration with a 0.3% volume concentration and SWI achieves the highest Nusselt number enhancement ratio, exhibiting a 174% increase compared to other configurations. In the same case, the pressure drop ratio reaches its peak at 157%. The exergy efficiency improves with an increase in nanoparticle volume concentration, with the 0.3% concentration with SWI showing the highest values, ranging from 54 to 65%. Among different concentrations, the SiO2/water nanofluid with a 0.2% volume concentration with SWI demonstrates the highest thermal–hydraulic enhancement factor, making it the optimal choice. The results prove that spring wire inert is more effective than nanofluid in the DPHHX. The contours, streamlines, and vectors of the temperature, velocity, and pressure distributions give more understanding for the heat transfer and fluid flow. [ABSTRACT FROM AUTHOR]

The decarbonization and decentralization of district heating networks lead to the shared use of on-site resources by multiple stakeholders. The optimal design of prospective equipment in such contexts should take into account the preferences and objectives of each stakeholder. This article focuses on the adaptation of a 4E multicriteria model (the criteria being energy, exergy, economic, and exergoeconomic) to include and compare the stakeholders' performance criteria around the technical design. In addition, two graphical supports are proposed that represent and cross-analyze the different stakeholders' preferred optima. A preliminary implementation of the methodology is illustrated through a study case in France, which features waste heat recovery for district heating utilization. After presenting the results, a discussion is offered on how to complete the methodology with an iterative negotiation procedure to determine the most suitable design. It was concluded, among other considerations, that the relaxation of the stakeholders' optimality requirements can greatly enable the project's feasibility. Such a relaxation could be implemented in the form of a joint consortium. In addition, the results showed that stakeholder relaxations of requirements can lead to new solutions that may outperform the best solutions pre-relaxation. Lastly, perspectives are suggested toward verifying whether relaxed requirements from upstream stakeholders might be more impactful than those of downstream stakeholders. [ABSTRACT FROM AUTHOR]

In recent years, there have been increasing concerns over the detrimental effects of irreversible linear patterns of material and energy consumption, which have led to an enormous generation of municipal solid waste (MSW). Concepts like waste-to-energy (WtE) and recycling have gained increasing recognition and support as responses to these challenges. This study assessed the exergetic potential of four WtE technologies (landfill gas-to-energy, anaerobic digestion, incineration, and plasma gasification) in the context of the MSW characteristics of Maiduguri, Borno State. The population of Maiduguri, waste generation rate, waste composition, and the ultimate and proximate analysis of the MSW were used for the assessment. Exergetic potential in the form of electrical energy generation and three exergy-based indicators (exergy efficiency, exergy defect, and improvement potential) were evaluated for each WtE option. The results reveal that anaerobic digestion and plasma gasification are viable options based on the exergetic potential and the measured exergy performance indicators. These findings offer valuable insights for policymakers and waste management authorities, facilitating informed decisions to address environmental concerns and promote resource-efficient urban development in Maiduguri and similar regions. [ABSTRACT FROM AUTHOR]