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This study presents and analyses three plant configurations of the Ocean Thermal Energy Conversion (OTEC) technology. All the solutions are based on using the OTEC system to obtain hydrogen through an electrolyzer. The hydrogen is then compressed and stored. In the first and second layouts, a Rankine cycle with ammonia and a mixture of water and ethanol is utilised respectively; in the third layout, a Kalina cycle is considered. In each configuration, the OTEC cycle is coupled with a polymer electrolyte membrane (PEM) electrolyzer and the compression and storage system. The water entering the electrolyzer is pre-heated to 80 °C by a solar collector. Energy, exergy, and exergo-economic studies were conducted to evaluate the cost of producing, compressing, and storing hydrogen. A parametric analysis examining the main design constraints was performed based on the temperature range of the condenser, the mass flow ratio of hot and cold resource flows, and the mass fraction. The maximum value of the overall exergy efficiency calculated is equal to 93.5% for the Kalina cycle, and 0.524 €/kWh is the minimum cost of hydrogen production achieved. The results were compared with typical data from other hydrogen production systems. [Display omitted] • An OTEC based offshore hydrogen production system is analysed by exergo-economics. • Three different OTEC cycles are compared: two Rankine and Kalina. • System includes OTEC, electrolyzer, H 2 compression, water desalination and heating. • Kalina cycle is the best performing, with 93.5 %, 83–87% for Rankine. • The cost of H 2 from Kalina OTEC is estimated at 17.3 €/kg (0.52 €/kWh). [ABSTRACT FROM AUTHOR]

Energy efficiency strategies in industrial breweries examine the inefficiency of thermal systems from a thermodynamic perspective. However, understanding the costs of inefficiencies in systems, including non-thermodynamic costs, requires exergoeconomics. This study examined wort production in a standard Tier-1 brewery from the tripod of energy, exergy, and exergoeconomics analyses to assess the performance of brewing sections and to pinpoint components that contributed the most to exergy destruction and product cost rate. The energy analyses for the production system showed that the total specific energy for processing 10.05 tons of brew grains to 346.98 hL high-gravity wort was (86 ± 1) MJ/hL at an operational energy efficiency of 30.35%. The exergetic analyses showed that the cumulative exergetic destruction was 3.2737 MW, with the brewhouse section contributing 89.25% of the system's inefficiencies. Also, the analyses showed that the wort kettle (42.7911%), mash tun (10.8086%), preheater (10.0683%), whirlpool (8.3522%), and adjunct kettle (6.2705%) are the top five components with the highest rates of cumulative exergy destruction. The exergoeconomic analyses revealed that the cost rate of processing chilled wort was estimated to be 0.0681 USD/s per overall exergetic efficiency of 6.61%. The five most significant components are the wort kettle (53.70%), whirlpool (16.42%), mash filter (10.44%), mash tun (6.875%), and adjunct kettle (3.31%) based on the relative total cost increases for the production processes. Additionally, wet steam throttling resulted in a 2.51% increase in exergetic efficiency, a 1.60% drop in exergetic destruction rate, and a decrease in cost rates to 0.0675 USD/s. [ABSTRACT FROM AUTHOR]

This paper investigates energy and exergy analyses of 660 MW capacity supercritical coal power plant with single reheat and regenerative. The fuel utilized in the plant is a combination of sub‐bituminous and lignite coal. It is found that the turbine section of the system exhibits the highest energy efficiency (around 94.17%) and exergy efficiency (around 90.73%). Also, 82.07% of the total exergy destruction is found for the boiler, and the remaining 17.93% of the irreversibility is determined for the turbine, condenser, and other components. The overall cycle energy efficiency at maximum load is computed as 40.77%, while the overall cycle exergy efficiency at maximum load is found to be 39.69%. These findings provide valuable insights into the performance of the power plant and suggest the improvements needed in performance enhancement of the boiler. [ABSTRACT FROM AUTHOR]

To meet the strict requirement on whole chain of vaccine production, storage, transportation, and distribution, most researches have been done on cascade refrigeration systems to achieve high operation performance, while a research gap on the performance exploration of eco‐friendly refrigeration systems still exists. In this paper, a comprehensive thermodynamic model was established to analyze the operation performance of a pre‐cooled cascade refrigeration system with eco‐friendly refrigerants propane (R290) and ethane (R170). Based on the present thermodynamic model, the performance optimization on the R290‐R170 cascade refrigerator was made with considerations of degree of subcooling, degree of superheat, evaporation temperature, condensation temperature, cascade condensation temperature, and cascade temperature difference. Variations of the coefficient of performance, exergy destruction, and total exergy efficiency of the refrigeration cycle were analyzed. Two mathematical correlations yielding the optimal cascade condensation temperature and maximized coefficient of performance were developed by multilinear regression analysis. When the evaporation temperature is − 60°C, the maximized coefficient of performance and total exergy efficiency are 1.276 and 49.51%. This paper demonstrates the potential for improving the R290‐R170 cascade refrigeration system and furnishes the basis for further exploration on ultra‐low‐temperature refrigerators. [ABSTRACT FROM AUTHOR]

The energy consumption of hydrogen liquefaction is often quantified as being approximately 40 % of hydrogen's lower heating value (LHV), making hydrogen liquefaction energy-intensive. Boundary conditions for energy consumption values in the literature are, however, often unclear, rendering these values questionable. Two methods can nevertheless significantly decrease energy consumption: (1) implementing improved liquefiers; and (2) utilising liquid hydrogen exergy – the reversible liquefaction work – stored in the liquid. Liquid hydrogen exergy equals 11.5 % LHV. And in comparison: per energy content, liquid hydrogen exergy is 5.5 times liquefied natural gas exergy. To estimate the energy savings potential of combining liquefier improvements and exergy utilisation, the exergy efficiency of improved liquefiers is calculated (44 %) and used as a quality measure. The same efficiency is assumed for exergy utilisation processes. The net energy consumption for the liquefaction - regasification chain is thereby reduced to 13-26 % LHV, depending on boundary conditions. • The H 2 liquefaction-regasification chain is evaluated by exergy analyses. • LH 2 exergy is 11.5 % of H 2 's lower heating value (LHV H 2 ), LNG exergy is 2.1 % of LHV CH 4 . • Improved H 2 liquefiers achieve 44 % exergy efficiency. • LH 2 exergy recovery during regasification estimated with liquefier exergy efficiency. • Energy consumption of H 2 liquefaction-regasification chain reducible to 13-26 % LHV H 2 . [ABSTRACT FROM AUTHOR]

• Energy, exergy, environment analyses and multi-objective optimization are performed for vortex tube coupled with transcritical refrigeration cycle (TVTC). • The parametric investigation is done to assess the thermodynamic performance of TVTC. • The cooling capacity of TVTC is found to be 10.1 % to 21.1 % higher than that of TVCR. • The maximum COP and exergetic efficiency of TVTC are higher than those of TVCR. • The evaporator temperature is the most influential input parameter in multi-objective optimization. The present study deals with the thermodynamic investigation of vortex tube coupled with trans-critical vapour compression refrigeration cycle (TVTC), followed by environmental analysis and multi-objective optimization. In this research, effect of various operating and design parameters is studied on the performance of TVTC. Furthermore, a comparison is made between the outcomes of TVTC and simple trans-critical vapour compression refrigeration cycle (TVCR). Results show that the optimum gascooler pressure for TVTC is observed to be lower than that of TVCR. Also, the cooling capacity and COP of TVTC are observed to be 10.1 % to 21.1 % and 2.3 % to 11.3 %, respectively, greater than those of TVCR. Moreover, the exergetic efficiency of TVTC is 2.3 % to 11.3 % higher than that of TVCR for the investigated range of evaporator and gascooler exit temperatures. The environmental penalty cost (per unit cooling capacity) of TVTC is 3.5 % to 12.2 % lower than that of TVCR. Furthermore, the coefficient of structural bond is calculated in order to choose the most sensitive parameters for system's performance. Additionally, genetic algorithm-based multi-objective optimization has been performed, with the evaporator temperature serving as the primary determining factor in establishing the optimal solution. This finding can guide the development of TVTC-based systems for a wide range of applications. [ABSTRACT FROM AUTHOR]

The combination of renewable energy and liquefied natural gas (LNG) cold energy can effectively improve energy utilization efficiency and achieve the goal of energy conservation and emission reduction, which is one of the important directions of future development. This work proposed a cascade organic Rankine cycle (ORC) driven by a geothermal heat source and an LNG heat sink. Seven organic fluids are chosen as candidates to form different working fluid pairs. The effects of the main design parameters on system performance are carried out through the thermodynamic analysis. Then, the optimal design conditions and fluid selection schemes are searched based on the single-objective optimization results. Finally, the exergy destruction study is conducted under the optimal design conditions and working fluid pair. Results showed that the cascade ORC system using the working fluid pair of R601/R290 had the highest exergy efficiency, which could reach 20.02%. At the same time, under the optimal design conditions, the secondary cycle condenser and LNG direct expansion brought high exergy destruction, which was respectively 29.3% and 25.8%, and followed by the two turbines in the cascade ORC system, which were 16.1%, 11.2% and 7.7%. [ABSTRACT FROM AUTHOR]

The present work focuses on the impact of combustion phase shifting from CDC (conventional diesel combustion) to RCCI (reactivity controlled compression ignition) mode of operation under various premixed ratios of hydrogen on the combustion, performance and exhaust emissions of a partially modified CI (compression ignition) engine. The hydrogen premix ratios are varied from 10% to 60% with 10% increment and the engine is tested at 0.9 kW, 1.8 kW, and 2.7 kW. The experimental results have shown that the hydrogen participation up to 40% premixed ratio improves the homogeneousness and stability of the combustion, resulting in 8.19% increase in cylinder pressure and 27.81% increase in heat release rate (HRR) at 2.7 kW brake power. It is also observed that the premix phase of combustion is faster with up to 40% hydrogen participation as the 50% mass burn is found to shift towards TDC. At the same operating point, the combustion is also found to be more stable with 72% reduction in COVIMEP. The brake thermal efficiency (BTE) increases by 10.07% when operating at 2.7 kW brake power with a 40% premix ratio, compared to diesel CDC operation. The unburned hydrocarbon (UHC), carbon monoxide (CO), and PM emissions are reduced by 9.17%, 21.68%, and 9.51%, respectively, for the hydrogen premixed ratio of 40%, with a marginal increase in the oxide of nitrogen (NOX) emissions. [ABSTRACT FROM AUTHOR]

The development of sustainable bioenergy technologies is positioned as a fundamental pillar for the development of local economies and a promising solution for the energy sector decarbonization. In the aim to contribute to these efforts, the present research considers a comprehensive process evaluation for a sustainable fuel production. Furthermore, chicken fat waste is considered as feedstock for the production of biodiesel with two glycerol valorization roots: The first configuration suggests a glycerol—biodiesel blend combustion for energy supply to the transesterification process, while the second process propose hydrogen production through in-site glycerol reforming. These two configurations were simulated using Aspen Plus software. Then, in order to select the optimal process configuration, multiple decision criteria including fundamental process engineering assessment tools such as energetic, exergetic, environmental and economic assessments were performed. Results revealed that hydrogen case presents a better thermal efficiency with 79.34% compared to 70.33% in the heat integrated configuration. The exergetic efficiency of the two configurations are 76% and 65% in hydrogen case and heat integrated case respectively. Environmental results indicate that 1 GJ of energy produced from chicken fat generates approximately 13.63 kg CO2-eq via hydrogen case and 26.75 kg CO2-eq by Heat integrated cases. From an economic point of view the hydrogen case is found more profitable. [ABSTRACT FROM AUTHOR]

This study concerns the development and experimental investigation of Direct Urea-Hydrogen Peroxide Fuel Cells (DUHPFC), with a particular emphasis on electrode preparation using nickel zinc iron oxide coated on stainless steel foil via the electrochemical deposition method, and the performance evaluation of single cells under varying operational conditions is also performed. This electrochemical deposition helps achieve a uniform and stable anode coating, which exhibits the high catalytic activity and stability, resulted in significantly enhanced urea oxidation reaction. The research further identifies an optimal performance for a single cell at 25 °C with 9 M KOH and 0.5 M urea, achieving a peak power density of 46.38 mW/cm2. The single cell demonstrates an open circuit voltage (OCV) of 0.72 V. Both energy and exergy efficiencies are further investigated for the cell performance and found to be 58% and 24%, respectively, at 5 M KOH. The electrochemical impedance spectroscopy (EIS) results reveal a significant reduction in impedance, from 30-Ωcm2 at 25 °C to 15-Ωcm2 at 65 °C, indicating an enhanced ionic conductivity and a reduced resistance. The present study results suggest that optimizing the electrode composition and operational parameters significantly improves the DUHPFC's performance, offering valuable insights for future fuel cell development. [Display omitted] • Urea and H₂O₂ enhance electrochemical reactions in DUHPFC systems. • Nickel zinc iron oxide catalyst boosts urea oxidation and cell efficiency. • Optimizing electrode composition and conditions improves DUHPFC performance. • Temperature and KOH concentration affect urea oxidation and cell efficiency. • Testing confirms the stability and durability of the developed anode. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising zero-carbon fuel, and its application in the micro-combustor can promote carbon reduction. The structural design of micro-combustors is crucial for combustion characteristics and thermal performance improvement. This study investigates the premixed combustion characteristics of hydrogen/air in a micro-cylindrical combustor with double ribs, using an orthogonal design method to assess the impact of various geometric parameters on thermal performance. The results indicate that the impact of rib height, rib position, and inclined angle is greater than rib width and their interactions, while their influence decreases in that order. Increased rib height improves mean wall temperature and exergy efficiency due to an expanded recirculation region and increased flame–wall contact, but negatively affects temperature uniformity and combustion efficiency. Although double ribs enhance performance, placing them too close may reduce heat transfer due to the low-temperature region between the ribs. When the double ribs are positioned at the axial third equinoxes of the micro-combustor, the highest mean wall temperature is achieved. Meanwhile, with a rib height of 0.3 and an inclined angle of 45°, the micro-combustor achieves optimal thermal performance, with the mean wall temperature increasing by 61.32 K. [ABSTRACT FROM AUTHOR]

This paper presents an analysis and optimization of a polygeneration power-production system that integrates a concentrating solar tower, a supercritical CO2 Brayton cycle, a double-flash geothermal Rankine cycle, and an internal combustion engine. The concentrating solar tower is analyzed under the weather conditions of the Mexicali Valley, Mexico, optimizing the incident radiation on the receiver and its size, the tower height, and the number of heliostats and their distribution. The integrated polygeneration system is studied by first and second law analyses, and its optimization is also developed. Results show that the optimal parameters for the solar field are a solar flux of 549.2 kW/m2, a height tower of 73.71 m, an external receiver of 1.86 m height with a 6.91 m diameter, and a total of 1116 heliostats of 6 m × 6 m. For the integrated polygeneration system, the optimal values of the variables considered are 1437 kPa and 351.2 kPa for the separation pressures of both flash chambers, 753 °C for the gasification temperature, 741.1 °C for the inlet temperature to the turbine, 2.5 and 1.503 for the turbine pressure ratios, 0.5964 for the air–biomass equivalence ratio, and 0.5881 for the CO2 mass flow splitting fraction. Finally, for the optimal system, the thermal efficiency is 38.8%, and the exergetic efficiency is 30.9%. [ABSTRACT FROM AUTHOR]

Improving the efficiency of solid oxide fuel cells (SOFCs) is critical for advancing clean energy solutions on a global scale. One major challenge in enhancing SOFC efficiency is reducing anode diffusion polarization, which can significantly hinder performance. This study addresses this issue by investigating the effects of anode tortuosity and porosity on the exergy efficiency of SOFCs. The novelty of this research lies in its comprehensive numerical model, which uniquely incorporates detailed material properties and their impact on SOFC performance—specifically focusing on anode tortuosity and porosity. Using advanced Multiphysics software, we developed a model that solves mass, electron transfer, and energy equations discretized via the finite differences method. The study meticulously examines how variations in these parameters influence SOFC efficiency, providing new insights into optimal anode design. Our methodology involves simulating different anode configurations to pinpoint the key parameters that affect exergy efficiency, thereby minimizing the experimental costs and time associated with traditional approaches. The quantitative results of this study are significant. We found that an anode tortuosity of 5.5 and a porosity range of 0.05–0.1 optimize exergy efficiency, achieving a 15% improvement compared to conventional designs. Additionally, a mean pore radius between 15 and 20 µm was identified as optimal for enhancing cell voltage. These findings elucidate the critical relationship between anode material properties and SOFC performance, offering a practical pathway to improving efficiency. This research provides a novel numerical approach to understanding and optimizing anode characteristics in SOFCs. By highlighting the importance of specific material properties, such as tortuosity and porosity, and demonstrating their impact on exergy efficiency, this study offers valuable guidance for future SOFC design and development. [ABSTRACT FROM AUTHOR]

In this study, the performance of a micro-combustor with an exhaust gas recirculation (EGR) channel was analyzed based on the second law of thermodynamics. Effects of the inlet velocity (V in), equivalence ratio (ϕ), separating wall length (L 1) and nozzle diameter (d in) on entropy generation and exergy efficiency of the micro-combustor were investigated. In general, chemical reaction contributes most to the total exergy destruction (>60%), followed by heat conduction, mass diffusion, and viscous dissipation. Meanwhile, all parts of the entropy generation rate increase with the increase of V in and ϕ. However, the entropy generation rates caused by chemical reaction and heat conduction decrease with the increase of L 1. The entropy generation rates due to chemical reaction and heat conduction show opposite variation trends respect to d in. An increase of V in and ϕ results in higher exergy destruction and exergy loss of the micro-combustor, the largest exergy destruction and exergy loss are 3.06 W and 5.94 W under V in = 200 m/s and ϕ = 1.0, respectively. While a longer separating plate length leads to a decrease in the exergy destruction and exergy loss. Exergy destruction and exergy loss change a little with d in and their values are around 1.6 W and 3.4 W, respectively. Exergy efficiency of the micro-combustor increases with the increase of V in and L 1 , but exhibits a non-monotonic variation with ϕ. A maximum exergy efficiency of 51.3% is achieved at V in = 200 m/s under ϕ = 1.0, d in = 0.20 mm and L 1 = 4 mm. In addition, the exergy efficiency decreases from 38.5% to 37.5% as d in increases from 0.20 mm to 0.30 mm under the same mass flow rate. [Display omitted] • The primary contributor to combustion irreversibility is chemical reaction. • Entropy generation by reaction rises with V in and ϕ , but reduces with L 1 and d in. • Entropy generation by heat conduction rises with V in and d in , but reduces with L 1. • Exergy loss from outer walls surpasses exergy destruction in the micro-combustor. • Exergy efficiency varies non-monotonically with equivalence ratio. [ABSTRACT FROM AUTHOR]

Combining finite time thermodynamics and exergetic analysis, analogous to the definition of ecological efficient power for heat engines, this paper proposes a unified performance indicator for various cycles, exergy-based efficient ecological function (E ɛ ) which is defined as product of exergy-based ecological function and coefficient of performance, and introduces it into performance optimization of endoreversible simple air refrigerator cycle coupled to constant-temperature heat reservoirs. Relations among E ɛ , pressure ratio (π) and heat conductance distribution ratio (u) are derived by using numerical method. The cycle performance indicators which include cooling load (R), coefficient of performance (ɛ), and exergetic loss rate (E out/T 0) under the different maximum objective criteria are compared. Taking π as optimal variable, and taking R, ɛ, cooling load density (r), E ɛ and their combinations as optimization objectives, multi-objective optimizations, totally 15 optimization combinations, are performed by using NASG-II algorithm. The results demonstrate that, the maximum E ɛ criteria can better reflect the compromise among R, ɛ and E out/T 0. The Pareto solution sets are majorly distributed in 2.5–20 when quadru-objective optimizations are performed. The option selected by LINMAP decision-making method is closer to ideal solution when bi-objective optimization of ɛ and r is carried out. [ABSTRACT FROM AUTHOR]

Dual-shell reactors using hydrothermal flames as internal heat source were proposed for supercritical water gasification (SCWG) and oxidation (SCWO) of oily sludge to achieve fast preheating and avoid corrosion, salt plugging, and overheating. The SCWG and SCWO systems with hydrogen-rich syngas and electricity outputs, respectively, were established and simulated using Aspen Plus 11. Simulation models were validated by comparing with experimental products and temperature profiles. The maximum exergy destruction coefficients of 28.01% and 24.31% appear in the combustion reactor for both the SCWG and SCWO systems, respectively, indicating the indirect preheating method with hydrothermal flame is critical to the energy efficiency. The increase of reaction temperature promotes hydrogen but inhibits methane formation in the SCWG, and more steam but less syngas is output at higher reaction temperatures. Although more steam and electricity outputs are present at higher reaction temperatures for the SCWO, more fuel input is required. Lower exergy efficiencies are obtained at higher reaction temperatures in both the SCWG and SCWO systems for more energy is output as low grade steam. Less fuel input is required for both the SCWG and SCWO systems at higher feed concentrations, and higher exergy efficiencies can be obtained. The net treatment cost for the SCWG and SCWO systems are 119.19 and 215.47 USD/t, respectively, indicating the SCWG is more economically competitive compared with the SCWO. • Reactors with hydrothermal flames were proposed for SCWG and SCWO of oily sludge. • SCWG and SCWO systems with energy output were built and simulated by Aspen Plus. • The maximum exergy destruction appears in the combustion reactor for SCWG and SCWO. • Lower exergy efficiencies appear at higher temperatuers for more steam output. • The SCWG has certain economic superiority compared with the SCWO. [ABSTRACT FROM AUTHOR]

This study presents an exergetic examination of a vapour compression refrigeration system. The exergetic balance conditions have been defined. Experimental work depending on the change of the capillary tube length (800, 1000, and 1200) mm with refrigerant mass flow rate changes from (10.3 to 21.3) kg/hr has been done to represent the different exergy flow occurring in the system components. The results were compared for each condenser temperature, evaporator temperature, coefficient of performance, exergy losses, exergy efficiency, efficiency defects, and rational efficiency. Results have been presented graphically. The finding indicated that the coefficient of performance decreased by 7% as the capillary length increased from 800 to 1200 mm. Also, the total exergy increases by 2.3% with increasing mass flow rates. [ABSTRACT FROM AUTHOR]

Heat energy conservation is essential in all aspects. Various sectors, such as HVAC (Heating, Ventilation, and Climate control), Chemical treatment, Thermoelectric plants, and Chilling units face challenges in utilizing effects, reusing heat, and preserving resources. Caloric can be recovered using a heat exchanger. Thermal exchangers necessitate substantial Monetary investment in favor of various Funds and operational costs. Therefore, it is essential to develop HE. That are more energy-intensive, costly, and resource-efficient. The approach to enhance heat transfer is nanofluid inserts with tape insertion. Through this research, we consolidated the parameters influencing the nanofluid's operation to improve the heat tray. A study has been carried out on advancing heat transmission using twisted taut. [ABSTRACT FROM AUTHOR]

Hydrogen liquefaction is essential for the efficient storage and transportation of hydrogen. In the liquefaction process, catalytic ortho‐para conversion is crucial to achieve a product with at least 95 % para‐hydrogen to reduce boil‐off losses. The proposed hydrogen liquefaction process using a catalyst‐filled heat exchanger for continuous ortho‐para conversion is modeled through steady‐state thermal simulations in Aspen HYSYS. Additionally, an ejector is integrated to reliquefy boil‐off gas. The proposed design achieves a specific energy consumption (SEC) of 10.50 kWh (kgLH2${\mathrm{kg}}_{{\mathrm{LH}}_2}$)−1 and an exergy efficiency (EXE) of 30.1 %, which is 18 % lower in SEC compared to processes with separate converters. The integrated approach enhances energy utilization and offers references for future hydrogen liquefiers. [ABSTRACT FROM AUTHOR]

Recent advancements in cryogenic etching, characterized by high aspect ratios and etching rates, address the growing demand for enhanced performance and reduced power consumption in electronics. To precisely maintain the temperature under high loads, the cascade mixed-refrigerant cycle (CMRC) is predominantly used. However, most refrigerants currently used in semiconductor cryogenic etching have high global warming potential (GWP). This study introduces a −100 °C chiller using a mixed refrigerant (MR) with a GWP of 150 or less, aiming to comply with stricter environmental standards and contribute to environmental preservation. The optimal configuration for the CMRC was determined based on a previously established methodology for selecting the best MR configuration. Comprehensive analyses—energy, exergy, environmental, and exergoeconomic—were conducted on the data obtained using Matlab simulations to evaluate the feasibility of replacing conventional refrigerants. The results reveal that using eco-friendly MRs increases the coefficient of performance by 52%, enabling a reduction in compressor size due to significantly decreased discharge volumes. The exergy analysis indicated a 16.41% improvement in efficiency and a substantial decrease in exergy destruction. The environmental analysis demonstrated that eco-friendly MRs could reduce carbon emissions by 60%. Economically, the evaporator and condenser accounted for over 70% of the total exergy costs in all cases, with a 52.44% reduction in exergy costs when using eco-friendly MRs. This study highlights the potential for eco-friendly refrigerants to be integrated into semiconductor cryogenic etching processes, responding effectively to environmental regulations in the cryogenic sector. [ABSTRACT FROM AUTHOR]

The accurate optimisation of absorption chillers is often impeded by idealised models that overlook system interactions and machine complexities. This study introduces a validated mathematical description for predicting the primary indicators of non-idealised absorption chillers, accounting for factors such as the electrical work of the Solution Circulation Pump, entropy changes within the refrigerant cycle, and exergy losses. Validation against 13 years of data (2008–2021) from the University of Debrecen's absorption chiller indicated close agreement, with deviations within acceptable limits. The use of a solution heat exchanger shifted cooling indicators towards their minima. Sensitivity analyses indicated that a 2.5% reduction in condenser temperature increased COP by 41.3% and Cooling Exergetic Efficiency by 15.5%, while a 2.5% reduction in the Heat Fraction Factor improved both by 34%. Adjusting absorber temperature and Heat Fraction Factor down by 2.5%, alongside a 2.5% rise in generator temperature, resulted in a 100.8% increase in COP and a 52.8% boost in Cooling Exergetic Efficiency. These insights provide a solid foundation for future optimisation strategies in real-life absorption chiller systems. [ABSTRACT FROM AUTHOR]

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Relying solely on electrical energy storage for energy regulation makes it difficult to provide a stable and efficient energy supply for microgrid systems currently. Additionally, the economic cost of microgrids and the rate of energy use present a challenge that must be addressed. A strategy for allocating capacity for multi-energy microgrids that takes energy efficiency and hydrogen energy into account is offered as a solution to the aforementioned issues. Initially, the construction of the multi-energy microgrid system takes into account the thermoelectric coupling properties of hydrogen energy devices. Second, the system's energy utilization level is measured using the exergy efficiency analysis. Next, the multi-objective capacity optimization allocation model of the multi-energy microgrid system is established, with the exergy efficiency and system economic cost serving as the objective functions. Lastly, the multi-objective model is solved using the ε -constraint approach to find the Pareto frontier, and Technique for Order Preference by Similarity to an Ideal Solution is employed for decision-making. The example results demonstrate that, when compared to a traditional microgrid using electric energy storage, the proposed model can effectively lower the system's economic cost and improve exergy efficiency. Additionally, multi-objective capacity optimization can be used to strike a balance between exergy efficiency and the system's economic cost. For relevant studies on the capacity allocation of multi-energy microgrids, this work can be a helpful resource. [ABSTRACT FROM AUTHOR]

Refrigeration plays a significant role across various aspects of human life and consumes substantial amounts of electrical energy. The rapid advancement of green cooling technology presents numerous solar-powered refrigeration systems as viable alternatives to traditional refrigeration equipment. Exergy analysis is a key in identifying actual thermodynamic losses and improving the environmental and economic efficiency of refrigeration systems. In this study exergy analyze has been conducted for a solar-powered vapor compression refrigeration (SP-VCR) system in the region of Ghardaïa (Southern Algeria) utilizing R1234ze(E) fluid as an eco-friendly substitute for R134a refrigerant. A MATLAB-based numerical model was developed to evaluate losses in different system components and the exergy efficiency of the SP-VCR system. Furthermore, a parametric study was carried-out to analyze the impact of various operating conditions on the system's exergy destruction and efficiency. The obtained results revealed that, for both refrigerants, the compressor exhibited the highest exergy destruction, followed by the condenser, expansion valve, and evaporator. However, the system using R1234ze(E) demonstrated lower irreversibility compared to that using R134a refrigerant. The improvements made with R1234ze are 71.95% for the compressor, 39.13% for the condenser, 15.38% for the expansion valve, 5% for the evaporator, and 54.76% for the overall system, which confirm the potential of R1234ze(E) as a promising alternative to R134a for cooling applications. [ABSTRACT FROM AUTHOR]

Considering environmental challenges and the diminishing share of energy expenses in the final product cost, evaluating energy‐intensive systems is crucial. This study examines the drying process of wet glass containers in a honey processing plant using a continuous convection dryer through energy and exergy analyses. Mass, energy, and exergy balances were performed using EES software. The energetic performance indicators revealed a heat loss rate of 3.33 kW, energy efficiency of 20.45%, and specific energy consumption of 11711.25 kJ kg‐1H₂O. Exergetic performance indicators included an exergy destruction rate of 24.05 kW, improvement potential rate of 20.79 kW, total exergy efficiency of 14.14%, exergy efficiency of 11.14%, specific exergy consumption of 2763.92 kJ kg‐1H₂O, and a sustainability index of 1.16. Results indicated that 60.12% of exergy destruction is related to air heating, with exhaust air losing 200.54 kW, equivalent to 89.84% of total input energy, suggesting exhaust air recirculation to reduce losses. Practical applications: The wet container dryer in a honey processing plant, as the most energy‐intensive component, was chosen for thermodynamic analysis. Mass, energy, and exergy balances were conducted to evaluate the system's thermodynamic performance. The exhaust air dryer lost 200.54 kW, equivalent to 89.84% of the total input energy, without utilization. Additionally, the results showed that 60.12% of the total exergy destruction in the convective drying process was related to air heating. Therefore, recirculating the exhaust air from the dryer moves the system toward an ideal thermodynamic state. [ABSTRACT FROM AUTHOR]

This study provides a comprehensive analysis of the thermal and exergy characteristics of a dairy plant that produces yoghurt. This study aims to perform a comprehensive analysis of the thermal and exergy aspects of a dairy facility that produces yoghurt. This study also seeks to improve the accuracy of the results by evaluating the reliability of the energy and production data. A comprehensive analysis of energy and exergy is utilized to enhance the yoghurt production process. Moreover, the Grassmann-Sankey diagram is employed to produce a map of energy density. The process's energy and exergy efficiencies were assessed by taking into account the enhancements and alterations made in addition to the existing implementations. Analysis of the yoghurt production process revealed that the total energy input was 113.9 [kW], the total energy output was 72.05 kW as well and the energy efficiency was 63.3%. The exergy input and output for the yoghurt production process were calculated to be 48.95 [kW] and 29.77 [kW], and the exergy efficiency was determined to be 60.8%. This study is expected to promote the growth of livestock and agriculture in the energy sector, and is forecasted to act as a catalyst for future research. This study, which is the first of its kind in the region and is expected to stimulate further research, reveals that improving energy efficiency and conservation in the production of yoghurt products enhances the factory's overall energy efficiency. [ABSTRACT FROM AUTHOR]

Advanced airborne power generation technology represents one of the most effective solutions for meeting the electricity requirements of hypersonic vehicles during long-endurance flights. This paper proposes a power generation system that integrates a high-temperature fuel cell to tackle the challenges associated with power generation in the hypersonic field, utilizing techniques such as inlet pressurization, autothermal reforming, and anode recirculation. Firstly, the power generation system is modeled modularly. Secondly, the influence of key parameters on the system's performance is analyzed. Thirdly, the performance of the power generation system under the design conditions is simulated and evaluated. Finally, the weight distribution and exergy loss of the system's components under the design conditions are calculated. The results indicate that the system's electrical efficiency increases with fuel utilization, decreases with rising current density and steam-to-carbon ratio (SCR), and initially increases before declining with increasing fuel cell operating temperature. Under the design conditions, the system's power output is 48.08 kW, with an electrical efficiency of 51.77%. The total weight of the power generation system is 77.09 kg, with the fuel cell comprising 69.60% of this weight, resulting in a power density of 0.62 kW/kg. The exergy efficiency of the system is 55.86%, with the solid oxide fuel cell (SOFC) exhibiting the highest exergy loss, while the mixer demonstrates the greatest exergy efficiency. This study supports the application of high-temperature fuel cells in the hypersonic field. [ABSTRACT FROM AUTHOR]

Plastic waste can exist naturally for hundreds of thousands of years and harm humans, animals, and the environment. In this study, the energy and exergy performances (absorbed energy, energy efficiency, absorbed exergy, and exergy efficiency) of LDPE (low-density polyethylene) plastic particles assisted by microwave heating based on the experimental data as affected by microwave power, feeding load, and chamber volume were evaluated and analyzed. The results showed that as the microwave power raised from 500 to 900 W, the feeding load changed from 10 to 30 g, and the chamber volume decreased from 200 to 100 ml, (a) the absorbed energy at the heating time of 60 min increased from 19.73 kJ, 5.84 kJ, and 22.71 kJ to 37.69 kJ; (b) the energy efficiency for the whole heating process increased from 1.10%, 0.32%, and 1.26% to 2.09%; (c) the absorbed exergy at the heating time of 60 min increased from 0.308, 0.091, and 0.091 to 0.724 kJ; and (d) the exergy efficiency for the whole heating process increased from 0.017, 0.005, and 0.023 to 0.040%, respectively. [ABSTRACT FROM AUTHOR]

Freeze desalination is a promising technique for wastewater treatment and zero/minimum liquid discharge systems, often requiring multiple stages to produce potable water. This research focuses on developing a Multiple Effect Freeze Desalination (MEFD) system based on experimental data for Single-Stage Desalination Efficiency (SSDE) and Single-Stage Recovery Rate (SSRR). The study analyzes various MEFD setups, calculating cooling energy consumption and correlating it with electrical usage through the coefficient of performance (COP). Comparisons with Reverse Osmosis (RO), Multi Effect Evaporation (MEE), and Multi-Stage Flashing (MSF) suggest that MEFDs may face challenges in matching RO efficiency but can compete with MEE and MSF within specific operational ranges. Exergy assessments indicate difficulties against even 10-stage MSF systems. Achieving SSDE and SSRR levels above 65% enables MEFDs to rival 10-stage MSF plants in terms of energy efficiency, surpassing MEE and MSF at over 85% efficiency. Despite these challenges, MEFDs offer benefits for treating high salt concentrations and resisting corrosion. [ABSTRACT FROM AUTHOR]

The cascade refrigeration systems (CRS) used in hypermarkets and supermarkets, which are used by many people, have been employing R744 for the low-temperature cycle (LTC) and R404A for the high-temperature cycle (HTC) due to environmental and public safety issues. However, the use of R404A is limited due to its high GWP, and therefore research on alternative refrigerants is necessary. Nevertheless, there is no detailed study in the literature that compares and analyzes the three refrigerants for practical design by applying R744 for LTC and R404A, R448A, and R449A for HTC in CRS. Therefore, this study aims to provide data for the practical detailed design of an alternative system to R744/R404A CRS. Under standard conditions, we analyzed how the exergy destruction rate (EDR) and exergy efficiency (EE) of the system and the EDR of each component change when the important factors affecting CRS (degree of superheating (DSH), degree of subcooling (DSC), and internal heat exchanger (IHX) efficiency of HTC, DSH of LTC, condensation temperature (CT), evaporation temperature (ET), cascade evaporation temperature (CET), and temperature difference of CHX) are varied over a wide range. The main conclusions are as follows. (1) Under the given constant conditions, the smallest change in system EDR based on R448A is DSH of HTC (decreased by 0.07–0.1 kW), followed by IHX of HTC (decreased by 0.12–0.3 kW), DSH of LTC (increased by 0.19–0.25 kW), DSC of HTC (decreased by 0.59–0.69 kW), temperature difference of CHX (increased by 1.57–1.83 kW), CET (decreased and then increased by 0.67–4.43 kW), CT (increased by 1.49–3.9 kW), ET (decreased by 2.39–4.61 kW). (2) The highest change rate of system EE based on R448A is CET (increased and then decreased by 1.38–8.28%), followed by temperature difference of CHX (decreased by 2.96–3.16%), ET (increased and then decreased by 0.63–2.75%), DSC of HTC (increased by 1.26–1.34%), CT (increased and then decreased by 0.24–1.12%), IHX of HTC (increased by 0.11–1.02%), DSH of LTC (decreased by 0.35–0.49%), and DSH of HTC (increased by 0.14–0.19%). [ABSTRACT FROM AUTHOR]

Compressed air energy storage systems offer an effective solution to the intermittency and fluctuation challenges associated with renewable energy grid integration. A significant challenge in current compressed air energy storage systems is the substantial energy loss incurred during the discharge due to throttling processes, which is crucial for improving round-trip efficiency. Therefore, an ejector-enhanced compressed air energy storage system (EA-CAES system) is proposed in this study, characterized by the employment of ejector to reduce the pressure loss caused by the throttling process. The performance of the system is analyzed from both sensitivity analysis and multi-objective optimization. Conventional exergy analysis is used to estimate the locations and magnitudes of exergy destruction within the system, and advanced exergy analysis is applied to determine the interactions among components and to identify the potential for system performance improvement. The results showed that, compared to the advanced adiabatic compressed air energy storage system, the round-trip efficiency of the proposed system increased by 3.07%, and the total exergy destruction during the pressure reduction process was reduced by 401.9 kW. As for the sensitivity for components in the EA-CAES system, the avoidable exergy destruction of the ejector is the most sensitive to changes in all parameters, followed by the unavoidable exergy destruction of the heat exchangers in the charging and discharging processes influenced by the air storage pressure and throttling pressure, respectively. Finally, based on the best trade-off solution among multi-objective optimization, the ejector, turbine, and compressor should be paid special attention to the system improvement according to the advanced exergy analysis. [ABSTRACT FROM AUTHOR]

Energy and Exergy based performetric analysis integrated with deep learning assisted energy modelling for grid connected solar PV system, tested to non-trained location is proposed. The first objective is to perform an energy and exergy based performetric analysis for a realistic 380 kWp grid connected roof-top PV system whose performance parameter is used for testing the proposed energy prediction models. The second objective is to formulate a simple and an improved energy estimation method applicable for 34 locations in South India, without change in model-coefficients. So, a long-term annual performance analysis of a 380 kWp PV based distributed generator situated at 12.97°N and 77.59°E is performed which estimates the characteristic performance indicators like energy efficiency, exergy efficiency, performance ratio and capacity factor amounting to 8.49%, 1.03%, 37%, and 8.03% respectively. The performance ratio of the plant is less as evident from the least exergy efficiency. The annual average losses in the system like thermal capture loss, array capture loss, system loss and miscellaneous loss amount to 0.46 (h/d), 2.51(h/d), 0.71 (h/d) and 2.97(h/d) respectively. The annual average energy generation of 380 kWp is 732.84 kWh/year. Furthermore, for realizing the second objective, a total of four models are proposed namely linear, exponential, non-linear and deep learning based neural network model resulting in R of 0.933, 0.9071, 0.9386, and 0.9603 respectively is formulated. The proposed models are tested for non-trained locations where the R value justifying the closeness between the actual and the predicted value is as high as 0.8. The proposed models are then compared upon their performances and benchmarked against the reported models. [ABSTRACT FROM AUTHOR]

Water energy is one of the potential renewable energy, the problem so far has a low efficiency of the blade Pelton shape. So it takes a series of tools to know characteristics and performance of the Pelton turbine as a hydroelectric power plant in this research. Pelton turbines work by utilizing the potential energy of water stored at a certain head, which flows through a penstock/pipe that is equipped with a nozzle at the end. The high head causes the water to be under high pressure when it reaches the nozzle. The water coming out of the nozzle becomes kinetic energy in the form of a pressurized water jet, which is used to rotate the runner of the Pelton turbine. In this study, the effect of the number of nozzles used to rotate the Pelton turbine was analyzed, with the result that the number of nozzles is directly proportional to the efficiency of the Pelton turbine. Where the highest efficiency value is obtained by using 3 nozzles with a maximum efficiency value of 13.7 %, at 2 nozzles of 12.209 % and at 1 nozzle of 8.82 %. [ABSTRACT FROM AUTHOR]

In order to fully apply liquefied natural gas (LNG) cold energy to the refrigeration system, four different types of CO2 multiphase refrigeration systems using LNG cold energy are designed. In this paper, (1) CO2 single-stage compressed solid and gas phase refrigeration cycle (SSCC1), (2) CO2 single-stage compressed solid and solid phase refrigeration cycle (SSCC2), (3) CO2 double-stage compressed solid and gas phase refrigeration cycle (DSCC1), and (4) CO2 double-stage compressed solid and solid phase refrigeration cycle (DSCC2) are combined with CO2 liquid phase secondary refrigerant cycle (RC), respectively, to effectively use LNG cold energy. The performance analysis, exergy analysis, economic analysis, and CO2 emission analysis of the proposed systems are carried out by establishing the mathematical models. The results show that the intermediate pressure of DSCC1-RC and DSCC2-RC reaches the best performance at 0.3 MPa, and the system performance decreases with the increase in intermediate temperature. The refrigerating capacity of the CO2 liquid phase secondary refrigerant cycle, the COP, and the exergy efficiency of four kinds of CO2 multiphase refrigeration systems decrease with the increase in the refrigerating capacity of the CO2 refrigeration cycle, while the power consumption of SSCC2-RC and DSCC2-RC decreases, SSCC1-RC and DSCC1-RC increased. The system with the shortest exergy loss is DSCC2-RC at 654.01 kW, while the system with the shortest payback period is SSCC2-RC at 0.88 years, and DSCC2-RC has the smallest CO2 emission. Four CO2 multiphase refrigeration systems and the ammonia combined refrigeration system with the same total refrigerating capacity are compared and analyzed, respectively; the results show that the performance, economy, and CO2 emission of CO2 multiphase refrigeration system are better than those of ammonia combined refrigeration system; and the exergy loss of CO2 multiphase refrigeration system is generally larger than that of ammonia combined refrigeration system because of the large temperature difference in heat transfer. [ABSTRACT FROM AUTHOR]

Highly integrated energy systems are on the rise due to increasing global demand. To capture the underlying physics of such interdisciplinary systems, we need a modern framework that unifies all forms of energy. Here, we apply modified Lagrangian mechanics to the description of multi-energy systems. Based on the minimum entropy production principle, we revisit fluid mechanics in the presence of both mechanical and thermal dissipations and propose using exergy flow as the unifying Lagrangian across different forms of energy. We illustrate our theoretical framework by modeling a one-dimensional system with coupled electricity and heat. We map the exergy loss rate in real space and obtain the total exergy changes. Under steady-state conditions, our theory agrees with the traditional formula but incorporates more physical considerations such as viscous dissipation. The integral form of our theory also allows us to go beyond steady-state calculations and visualize the local, time-dependent exergy flow density everywhere in the system. Expandable to a wide range of applications, our theoretical framework provides the basis for developing versatile models in integrated energy systems. [ABSTRACT FROM AUTHOR]

This study delves into the comprehensive analysis of four conventional mixed refrigerant liquefaction processes, namely C3MR-Linde, C3MR-APCI, SMR-Linde, and SMR-APCI, emphasizing energy and exergy perspectives. According to the energy analysis, C3MR-Linde demonstrates a lower energy consumption than the other systems, at 0.271 kWh kg−1 liquefied natural gas, while SMR-Air Products achieves the highest coefficient of performance (COP) at 2.67 kWh kg−1. The exergy analysis provides insights into the exergy efficiency and destruction of components, highlighting the C3MR-Linde process as the most exergy-efficient process, attaining 47.55%. Notably, compressors are identified as the primary sources of exergy destruction, accounting for 52.11%, 52.51%, and 45.39% of the overall cycle exergy destruction in the C3MR-APCI, C3MR-Linde, and SMR-APCI cycles, respectively. Furthermore, this study investigates how certain operational factors affect the COP, specific energy consumption (SEC), and exergy indices. It is observed that each cycle exhibits an optimal pressure drop in the expansion valves, with deviations resulting in a decreased COP and increased SEC. Additionally, changes in the refrigerant molar flow rates demonstrate an inverse relationship between the exergy efficiency and COP, with the SEC being notably more sensitive to such variations than the COP within the studied parameters. [ABSTRACT FROM AUTHOR]

The cooling system of an electric vehicle can be affected in various ways by vibrations, potentially impacting its performance and reliability. This encompasses damage to the components, potential leaks, noise, and discomfort, which may impact the performance. The impact of vibrations on electric vehicle cooling systems utilizing nanofluids as their primary working fluids remains insufficiently explored. Ongoing research aims to elucidate the specific influence of vibrations on these cooling systems implemented in such vehicles. The study of vibrations with amplitudes of up to 5 mm and frequencies of up to 25 Hz has been conducted. In the numerical model, a 2% volume concentration Al2O3 solution was utilized as the working fluid, with water serving as the base fluid, and Reynolds numbers ranging from 10,000 to 20,000 in the turbulent regime. The present study is focused on performing exergy and entropy analysis utilizing the second law. On inducing vibration onto the system, the Nusselt number rises to a maximum of 170% compared to the static tube. Entropy generation increases with increasing intensity of vibration. A similar trend is observed for second law efficiency which reaches a maximum of 60.81% at 5 mm amplitude and 25 Hz frequency at 20,000 Reynolds number. But with increasing intensity of vibration, dimensionless number of irreversibility (ϕ ) shows a negative trend with a minimum of 0.715 at 25 Hz frequency and 5 mm amplitude of vibration. Introducing controlled vibrations can significantly enhance system availability and efficiency, leading to considerable improvements in energy usage and cost-effectiveness. [ABSTRACT FROM AUTHOR]

An energy and exergy analysis of an experimental air-conditioning absorption system operating with the ammonia-lithium nitrate mixture has been performed. The system was operated under controlled and steady-state conditions. The main operating parameters, such as flow ratio, coefficient of performance, exergy coefficient of performance, and exergy destruction in each one of the main components, were determined at different heat sources and condensing temperatures. The coefficients of performance varied between 0.5 and 0.65, while the exergy coefficients of performance varied between 0.1 and 0.2. Clear trends were found for the coefficient of performance and flow ratio as a function of the generator and condenser temperatures; however, no trends were found in the exergy coefficients of performance due to the high variability of the ambient temperature. The highest values of the exergy destruction occurred in the generator, followed by the condenser and the evaporator, while the lowest values were obtained in the absorber and the economizer. [ABSTRACT FROM AUTHOR]

This study compares the exergy of an ejector‐based two evaporator cycle (EB‐TEC) with a conventional two evaporator cycle (C‐TEC). The analysis utilizes a modified Gouy–Stodola equation, which provides a more accurate insight of the system irreversibility compared to the standard Gouy–Stodola formulation. Furthermore, the comparison includes three working fluids, that is, R134a, R1234ze, and R600 in both the cycles. The study examines the effects of varying evaporators and condenser temperatures and the dryness fraction at the exit of Evaporator 1. The data is analyzed using an Engineering Equation Solver. The findings indicate that increasing the temperature of the low‐temperature evaporator leads to a drop in exergy losses and enhancement in exergy efficiency in both the cycles. When the temperature of Evaporator 1 is increased, the total exergy of the EB‐TEC is decreased but for the C‐TEC, it is increased. Furthermore, increasing the condenser temperature results in higher exergy destruction in both EB‐TEC and C‐TEC. Notably, the maximum exergy destruction is 49.44 kW for R600, whereas the minimum exergy destruction is 14.42 kW for R1234ze in the EB‐TEC. [ABSTRACT FROM AUTHOR]

In the present study, the energy, exergy, environmental, and economic (4-E) analyses of Rajai's combined cycle power plant with applying environmentally friendly technologies have been performed. To this end, three scenarios have been considered: (1) without auxiliary systems; (2) with modified guide vane system; (3) integrated guide vane system and inlet air fogging. The angle was increased from 84 $$^\circ $$ ∘ to 86 $$^\circ $$ ∘ to modify the guide vane opening angle of the compressor. Besides, inlet air fogging is used to reduce the compressor's inlet temperature. The results show that the highest exergy destruction ($$\~34\% $$ \~ 34 %) occurred in the combustion chamber. The corresponding values for HRSG and gas turbine are 21% and 26%, respectively. With a modified guide vane system, scenario 2, the cycle's first law efficiency is enhanced by 0.56% compared to scenario 1. In addition, in scenario 3, the second law efficiency increased by 0.67%, and the exergy destruction decreased by 0.85%. By using the proposed system, an increased income of $${h_i}$$ h i .85 per megawatt-hour was gained. Regarding the $$C{O_2}$$ C O 2 emission and fuel consumption, a reduction of 1.65% and 1150 $${m^3}/h$$ m 3 / h was observed. [ABSTRACT FROM AUTHOR]

The present work provides Potential Energy Curves (PECs) of both cyano radical CN and cyanide anion ${\rm CN}^{-}$ CN − up to the third asymptote of dissociation out of ab initio calculations. The [MRCI+Q] method is the level of theory used here and we have associated it with the Dunning basis set AV6Z (Augmented correlation-consistent polarised Valence sextet Zeta) for geometry optimisation of our systems. Electronic configurations of the states of the two species were explored and based on these configurations and the relative positions of the PECs of ${\rm CN}^{-}$ CN − against those of the neutral radical CN, stable and metastable states have been found and exhibited. The calculated electron affinity here that proves itself to be positive and the position of the ${\rm X}^{1}\Sigma ^+$ X 1 Σ + state against its corresponding neutral parent state (${\rm X}^{2}\Sigma ^+$ X 2 Σ + ) from which it derives led to confirm that this state is a long-lived and stable ground state of the cyanide anion ${\rm CN}^{-}$ CN − . Spectroscopic constants of both ground and low-lying excited states are calculated and exhibited in this work. [ABSTRACT FROM AUTHOR]

Energy demand is a critical contemporary concern, with significant implications for the future. While exploring renewable or sustainable energy sources offers potential solutions, optimizing energy consumption in existing power generation systems is also key. Aviation accounts for a substantial portion of energy demand, underscoring the importance of energy efficiency in this sector. Conventional energy analyses may be misleading; hence, employing exergy-based analyses provides a clearer understanding of energy consumption. Also, most of these analyses do not include the effect of the turbine blade's cooling in calculations. In the present study, exergy analyses have been conducted on a helicopter turboshaft engine with turbine-blades cooling, focusing on design parameters such as ambient temperature, compressor pressure ratio, and turbine inlet temperature. Thermodynamic optimizations are conducted using a genetic algorithm. Results show that increasing pressure ratio and turbine inlet temperature boost performance, yet technical restrictions on compressor and turbine size, and metallurgical constraints on turbine blades' material limit these gains. Sea level scenario prioritizes ambient temperature-drop for enhancing net-work and efficiency, while altitude-gain boosts turboshaft performance. Combustion chambers incur the highest exergy destruction of 74-80%, followed by 16-20% and 4-6%exergy destructions in the turbine and compressor, respectively. Lower air temperatures and higher flight altitudes demand larger fuel consumption for equivalent turbine inlet temperature, albeit enhancing cooling capacity and reducing required cooling air fraction for turbine blades. [ABSTRACT FROM AUTHOR]

Solar energy, which is a clean, unlimited, and environmentally friendly energy source, has critical importance in sustainable energy management. The usable potential of energy is expressed in terms of exergy, and the determination of the exergy potential of solar energy ensures the correct utilization of this potential. Turkey has a very high solar energy potential, and this potential should be utilized in the most efficient way possible to achieve sustainable energy targets. The tilt angle of solar panels has a significant effect on efficiency. Efficient operation of solar panels can be achieved by determining the optimum tilt angle. In this study, Turkey's solar exergy potential was calculated for the horizontal plane and five different tilt angles (21°, 30°, 39°, 48°, and 57°). Thus, it was tried to determine the appropriate panel angle to get the highest efficiency from solar panels that can be used in different regions of Turkey. The calculations are based on 22-year average solar energy potential data obtained from NASA. The exergy potential was determined for the coordinates where Turkey is located, and the potential for the regions between the coordinates was determined by the interpolation method. With the interpolation method used, an approximate estimation for the areas where there is no measurement is also provided, and it is aimed at saving the time and cost required for long-term measurements. Among the tilt angles analyzed, the optimum angle for the whole year was determined to be 30 degrees. The exergy potential for 30° inclined surfaces in all coordinates of Turkey is given as a seasonal map. With the use of the maps, it is thought that the optimum angle and exergy potential for different regions and seasons of Turkey will be predicted, and thus it will be easier for new investors to determine the high-potential regions of Turkey. [ABSTRACT FROM AUTHOR]

Regenerative design is being increasingly explored in urban environments to counteract and adapt to the changing climate and degradation of ecosystems. A critical success factor for the implementation of regenerative design is the evaluation of urban and building systems in relation to ecological performance and benefits. In biological ecosystems, the availability of high-quality energy, called exergy, and structural order can be used as indicators of the efficiency of on-going ecological processes. Structural order refers to the organization and systematic arrangements of biotic and abiotic elements within an ecosystem based on the available space and interactions with the goal to form a functional system. Ecological processes use the available exergy and generate ecosystem services (ESs) upon which human survival and that of other living organisms depend. In this article, structural order and ESs generation are proposed as indicators for exergy efficiency and accumulation in building systems, respectively, which can evaluate to what extent they are ecologically functional and regenerative. Based on this insight, design strategies are derived from the functioning of ecosystems that describe how buildings could become habitats that host living, non-living, and hybrid systems with optimized thermodynamic efficiency and that can generate ESs. This research suggests that when buildings improve structural order (an ecological concept) and implement ESs generating processes similar to biological ecosystems, they can facilitate regenerative processes more effectively that consume and generate resources and, with this, destroy but also accumulate exergy. [ABSTRACT FROM AUTHOR]

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Industrial buildings have numerous kinds of energy-losing equipment, such as engines, ovens, boilers and heat exchangers. Energy losses are related to inefficient energy use and lousy work conditions for the people inside the buildings. This work is devoted to the recovery of lost energy from industrial buildings. Firstly, the residual energy of the building is extracted to be used to warm water. Consequently, the work conditions of the people inside industrial buildings can be improved by maintaining the adequate temperature. The recovery of the energy is performed by a multipurpose heat pump system (HP system). The working fluid used in the HP system is R134a, which is a traditional and cheap working fluid. The thermophysical properties of R134a are obtained through the PC-SAFT equation of state. This work presents a performance mapping based on the intercepted areas framework to evaluate which working conditions are the optimal operating variables. The latter depends on several key parameters, such as compressor work, heat delivery, heat absorbed and exergetic efficiency. The results show that the optimal work conditions are found at different condenser and evaporator temperatures, and these may be limited by what the designer considers a sound performance of the heat pump system. [ABSTRACT FROM AUTHOR]

The present study adopted the thermodynamic technique to model a membrane energy exchanger (MEE) used for proton exchange membrane fuel cell (PEMFC) application. Governing equations, including a system of three nonlinear coupled equations and several dependent equations, are solved. The present numerical results were compared and validated by an experimental study, indicating a suitable match with a reasonable error. A comprehensive parametric study and sensitivity analysis were conducted in this study based on four efficiency evaluation criteria, including effectiveness, water recovery ratio (WRR), entropy generation, and exergy efficiency. The exergy efficiency comprises the thermodynamic exergy, chemical exergy, and mechanical exergy. The analyzed parameters included temperature at the wet and dry channel entry, pressure at the wet and dry channel entry, and relative humidity (RH) at the wet and dry channel entry. A to D ratings were assigned to these parameters. When three criteria show positive results by enhancing each parameter, the A rating is assigned to that parameter, representing the optimal efficiency. For example, enhancing the dry channel entry temperature from 306 to 318 K leads to a 30.5% enhancement in WRR, a decrease in DPAT, an 11% improvement in exergy efficiency, and a reduction in entropy generation. Since all four criteria were desirable, enhancing the dry channel entry temperature was rated A and is highly recommended. [ABSTRACT FROM AUTHOR]

Despite being stored at 113 K and at atmospheric pressure, LNG cold potential is not exploited to reduce green ships' energy needs. An innovative system based on three organic Rankine cycles integrated into the regasification equipment is proposed to produce additional power and recover cooling energy from condensers. A first-law analysis identified ethylene and ethane as suitable working fluids for the first and the second ORC, making freshwater and ice available. Propane, ammonia and propylene could be arbitrarily employed in the third ORC for air conditioning. An environmental analysis that combines exergy efficiency, ecological indices and hazard aspects for the marine environment and ship passengers indicated propylene as safer and more environmentally friendly. Exergy analysis confirmed that more than 20% of the LNG potential can be recovered from every cycle to produce a net clean power of 76 kW, whereas 270 kW can be saved by recovering condensers' cooling power to satisfy some ship needs. Assuming the sailing mode, a limitation of 162 kg in LNG consumptions was determined, avoiding the emission of 1584 kg of CO2 per day. Marine thermal pollution is reduced by 3.5 times by recovering the working fluids' condensation heat for the LNG pre-heating. [ABSTRACT FROM AUTHOR]

The present work provides Potential Energy Curves (PECs) of both cyano radical CN and cyanide anion ${\rm CN}^{-}$ CN − up to the third asymptote of dissociation out of ab initio calculations. The [MRCI+Q] method is the level of theory used here and we have associated it with the Dunning basis set AV6Z (Augmented correlation-consistent polarised Valence sextet Zeta) for geometry optimisation of our systems. Electronic configurations of the states of the two species were explored and based on these configurations and the relative positions of the PECs of ${\rm CN}^{-}$ CN − against those of the neutral radical CN, stable and metastable states have been found and exhibited. The calculated electron affinity here that proves itself to be positive and the position of the ${\rm X}^{1}\Sigma ^+$ X 1 Σ + state against its corresponding neutral parent state (${\rm X}^{2}\Sigma ^+$ X 2 Σ + ) from which it derives led to confirm that this state is a long-lived and stable ground state of the cyanide anion ${\rm CN}^{-}$ CN − . Spectroscopic constants of both ground and low-lying excited states are calculated and exhibited in this work. [ABSTRACT FROM AUTHOR]