Search Results (72)

The development of efficient and economically viable energy storage technologies is key to the integration of renewable energies. This study evaluates the thermo-economic performance of hydrocarbons as working fluids in PTES systems based on a simple Brayton cycle (SBC). Different hydrocarbon mixtures are analyzed to determine their impact on efficiency and costs, identifying optimal operating conditions and combinations that improve system performance and viability. The objective is to identify the optimal candidate and operating conditions for enhanced cost-effectiveness. A multivariable optimization was performed using a validated thermodynamic model, integrated with an economic evaluation framework. Key decision variables included pressure ratios, turbine inlet temperatures, and heat exchanger performance parameters, while several sCO_2–hydrocarbon mixtures were evaluated as working fluids. Energy and exergy analyses were coupled with component-level cost correlations to determine round-trip efficiency, specific investment cost, and levelized cost of storage. The findings indicate that the CO₂/C₂H₆ (60/40) mixture provides the best overall performance, achieving a round-trip efficiency of 54.38% and a levelized cost of storage of 137.1 $/MWh, outperforming pure CO₂. Fluid selection exerts a substantial influence on both thermodynamic and economic indicators, with performance exhibiting a pronounced dependency on critical temperature, molecular complexity, and operating pressure levels. Sensitivity analyses indicate that improvements in heat exchanger effectiveness and turbomachinery efficiency yield substantial reductions in total system cost. The findings indicate that the appropriate alignment of hydrocarbon properties with system design parameters can significantly enhance the feasibility of PTES, offering a technically viable and economically competitive pathway for large-scale energy storage applications. Full article

The efficient recovery of low-enthalpy geothermal resources $(T\le 150$ °C) faces significant thermodynamic limitations due to thermal mismatch in evaporators when pure fluids are utilized. This study investigates low-GWP zeotropic mixtures (Pentane/Isobutane), optimized using the NSGA-II algorithm, to enhance both the efficiency and operational resilience of Organic Rankine Cycles (ORCs). The isothermal behavior of conventional fluids limits exergy recovery and increases the Levelized Cost of Energy (LCOE). To address this, an advanced simulation tool, “ORC Master Suite”, was developed and validated against recent literature. Exergetic efficiency and LCOE were simultaneously optimized under strict Pinch Point constraints. Results show that the low-GWP zeotropic mixture of Pentane/Isobutane (70/30% w/w) achieves a 15–25% increase in exergetic efficiency compared to pure fluids, mainly due to the temperature glide, which reduces irreversibilities. Despite the increase in required heat transfer area and the strict capital expenditure penalties associated with ATEX safety protocols for highly flammable hydrocarbons, the LCOE remained competitive against the reference fluid. Overall, low-GWP zeotropic mixtures not only improve thermodynamic performance but also exhibit higher operational resilience to geothermal source fluctuations, making them a promising and sustainable alternative for future geothermal power plants. Full article

There are numerous operating parameters that affect the thermodynamic and thermoeconomic performance of gas turbine cycles, and many studies based on energy, exergy, and economic analyses have been conducted in the literature by considering these parameters. However, the order of importance and contribution ratios of key operating parameters such as ambient temperature, compressor pressure ratio, combustion efficiency, regenerator effectiveness, and compressor and turbine isentropic efficiencies with respect to thermal efficiency, exergy efficiency, and the levelized cost of electricity (LCOE) have not been sufficiently investigated using statistical methods. Accordingly, a thermodynamic model of a gas turbine cycle improved with intercooling, reheating, and regeneration processes was developed in the study, and thermal efficiency, exergy efficiency, and LCOE values were calculated under different parameter levels. Taguchi analysis was carried out by using the L27 orthogonal array, in which six operating parameters were evaluated at three levels, and optimum parameter levels were determined for each performance indicator. Next, the contribution ratios of the parameters to the objective functions were calculated using the ANOVA method. The results showed that turbine isentropic efficiency was the most influential parameter in terms of thermal and exergy efficiencies, while compressor pressure ratio played the dominant role in terms of LCOE. Additionally, to simultaneously achieve the goals of maximizing thermal and exergy efficiencies and minimizing the LCOE value, the grey relational analysis (GRA) method was applied as a multi-objective optimization approach, and the optimum operating conditions were determined based on a single performance indicator. According to the GRA results, under the optimum conditions, the thermal efficiency was calculated as 0.5533, its exergy efficiency was 0.5772, and the LCOE value was 0.01751 USD/kWh. Full article

Solar-aided power generation offers a pathway to reduce the carbon dioxide emissions from existing coal-fired plants. This study addresses the gap in comparing different solar integration modes by conducting a thermo-economic analysis of a 600 MW coal-fired system retrofitted with a solar tower. Four integration modes were designed and rigorously compared, encompassing series and parallel configurations at either the high-exergy reheater or the lower-exergy economizer. A detailed thermodynamic model was developed to simulate its off-design and annual performance. The results showed that integration at the primary reheater outperformed the economizer integration. Specifically, the parallel configuration at the primary reheater (Mode II) achieved the highest annual solar-to-electricity efficiency of 18.43% at a thermodynamically optimal heliostat field area of 125,025.6 m². Economic analysis revealed a trade-off, with the minimum levelized cost of energy (LCOE) of −0.00929 USD/kWh for Mode II occurring at the economically optimal area of 321,494 m² due to greater coal and emission savings. Sensitivity analysis across two other locations confirmed that the annual solar-to-electricity efficiency and LCOE are directly influenced by solar resource quality, but the thermodynamically optimal and economically optimal heliostat field area remain consistent. This work demonstrates that parallel integration with the primary reheater presents a favorable and practical configuration, balancing high solar-to-electricity conversion efficiency with favorable economics for hybrid solar–coal power plants. Full article

This study presents a comprehensive thermo-economic evaluation of a pumped thermal energy storage (PTES) system based on a supercritical carbon dioxide (s-CO₂) recompression Brayton cycle (RBC). A multiparametric analysis was conducted through systematic parameterization of key design variables, including mass fractions directed to the recompressor during charging and to the high-pressure turbine during discharging, as well as compressor inlet pressure and temperature and turbine inlet temperature. Performance optimization focused on two main indicators: round-trip efficiency (${\eta }_{RT}$) and levelized cost of storage (LCOS), enabling identification of trade-offs between thermodynamic and economic performance. Results show that minimizing LCOS yields 148.72 $/MWh with an ${\eta }_{RT}$ of 57.1%, whereas maximizing efficiency achieves 61.5% at an LCOS of 158.4 $/MWh. Exergy destruction analysis highlights the strategic role of the main compressor and thermal storage tanks in overall irreversibility distribution. These findings confirm the technical feasibility of the s-CO₂ recompression Brayton cycle as a competitive solution for long-duration thermal energy storage. Full article

Carnot Batteries with thermal integration stand as one of the most promising approaches to tackling contemporary global energy problems. Currently, research on Carnot Battery systems utilizing the ocean thermal gradient is still in its early stages. This paper establishes a holistic thermo-economic model to assess the system’s performance. Through working fluid screening and subsequent multi-objective optimization, this study identifies the optimal working fluid and clarifies the system’s thermal economy at the optimal design point. With round-trip efficiency and total cost as metrics, a sensitivity analysis identified key parameter effects on the system. This was followed by a multi-objective optimization, where the TOPSIS method selected the optimal solution. It was found that, when Ammonia and R1234yf were used as the working fluids in the RC and ORC sub-cycles, respectively, the system can achieve peak performances of 71.79% round-trip efficiency and 36.24% exergy efficiency. Moreover, the RC evaporation temperature exerts the most significant influence on the overall thermodynamic performance. Multi-objective optimization successfully identified a balanced thermo-economic design, yielding an optimal solution with a round-trip efficiency of 65.30% at a total cost of USD 65.90 M. These results offer critical insights for the design and optimization of this promising ocean thermal-powered Carnot Battery system. Full article

This study presents an integrated thermo-economic framework for evaluating the impact of daily overload on the aging and cost performance of oil-immersed distribution transformers. The methodology combines international transformer thermal aging models, widely accepted in transformer loading guides such as those established by IEEE and IEC, with an equivalent annual cost (EAC) model, enabling a unified assessment of insulation degradation and operational expenditures. Using a residential load profile with 15 min resolution and climate data from three Ecuadorian regions (Quito, Guayaquil, and the Amazon), we analyze the influence of varying overload levels, peak durations, cooling methods Oil Natural Air Natural (ONAN), Oil Natural Air Forced (ONAF), and Oil Forced Air Forced (OFAF), and installation environments (indoor/outdoor) on transformer lifetime and ownership costs. Parametric simulations reveal that ambient temperature is the dominant factor in thermal degradation, with Guayaquil showing service life reductions of up to 70% compared to Quito under identical loading conditions. While larger transformers with forced cooling exhibit enhanced thermal resilience, the economic performance deteriorates non-linearly beyond 120–130% loading due to compounding losses and replacement costs. The results demonstrate that (i) overload tolerance is climate dependent, (ii) indoor installations incur systematic thermal penalties, and (iii) the IEC and IEEE models yield similar outcomes under moderate conditions but diverge under severe stress. The proposed approach provides utilities with a robust decision-support tool to optimize transformer loading strategies, replacement planning, and cooling system upgrades in geographically diverse power systems. Full article

Geothermal energy has been recognized as a promising renewable resource for sustainable power generation; however, the efficiency of conventional geothermal power plants has remained relatively low, and high investment costs have limited their competitiveness with other renewable technologies. In this context, the present study introduced an innovative geothermal electricity generation system aimed at enhancing energy efficiency, cost-effectiveness, and sustainability. Unlike traditional configurations, the system raised the geothermal source temperature passively by employing advanced heat transfer mechanisms, eliminating the need for additional energy input. Comprehensive energy, exergy, and exergoeconomic analyses were carried out, revealing a net power output of 43,210 kW and an energy efficiency of 30.03%, notably surpassing the conventional Kalina cycle’s typical 10.30–19.48% range. The system’s annual electricity generation was 11,138.53 MWh, with an initial investment of USD 3.04 million and a short payback period of 3.20 years. A comparative assessment confirmed its superior thermoeconomic performance. In addition to its technoeconomic advantages, the environmental performance of the proposed configuration was quantified. A streamlined life cycle assessment (LCA) was performed with a functional unit of 1 MWh of net electricity. The proposed system exhibited a carbon footprint of 20–60 kg CO₂ eq MWh⁻¹ (baseline: 45 kg CO₂ eq MWh⁻¹), corresponding to annual emissions of 0.22–0.67 kt CO₂ eq for the simulated output of 11,138.53 MWh. Compared with coal- and gas-fired plants of the same capacity, avoided emissions of approximately 8.6 kt and 5.0 kt CO₂ eq per year were achieved. The water footprint was determined as ≈0.10 m³ MWh⁻¹ (≈1114 m³ yr⁻¹), which was substantially lower than the values reported for fossil technologies. These findings confirmed that the proposed system offered a sustainable alternative to conventional geothermal and fossil-based electricity generation. Multi-objective optimization using NSGA-II was carried out to maximize energy and exergy efficiencies while minimizing total cost. Key parameters such as turbine inlet temperature (459–460 K) and ammonia concentration were tuned for performance stability. A sensitivity analysis identified the heat exchanger, the first condenser (Condenser 1), and two separators (Separator 1, Separator 2) as influential on both performance and cost. The exergoeconomic results indicated Separator 1, Separator 2, and the turbine as primary locations of exergy destruction. With an LCOE of 0.026 USD/kWh, the system emerged as a cost-effective and scalable solution for sustainable geothermal power production without auxiliary energy demand. Full article

High peak-hour energy consumption from air conditioning in commercial buildings creates significant operational costs and grid instability. This study experimentally investigates the thermo-economic performance of a vapor compression refrigeration system (VCR) ice storage system to address this challenge through load shifting. The methodology involved operating a custom test rig, featuring an insulated test chamber and an ice tank with a novel spiral evaporator, under an improved 8 h night charging and 9 h day discharge strategy. Results show the system consumed 5.44 kWh of electricity to store 7.70 kWh of thermal energy, achieving a charging Coefficient of Performance (COP) of 1.42. A total of 5.195 kWh of cooling was delivered with a discharge efficiency of 67.5%. The experimental cost analysis confirmed an approximate 20% operating cost advantage over conventional direct cooling. A simple payback assessment indicates strong sensitivity to tariff structures and annual operating days. This study concludes that the optimized Ice Storage System (ISS) is a technically viable and economically advantageous solution for managing peak cooling loads, providing a validated reference model and dataset for future work. Full article

It is of particular interest to use eco-friendly working fluids in ocean thermal energy conversion (OTEC) systems. In response, this study develops a thermo-economic model to evaluate the feasibility of fourth-generation refrigerants, including R1234yf, R1234ze(Z), and R1336mzz(Z), as potential alternatives to ammonia. The analysis examines the effects of system scale and cold seawater pumping depth on capital investment distribution and key economic indicators, such as the levelized cost of energy (LCOE) and net present value (NPV). The findings highlight the viability of R1234ze(Z) as a substitute for ammonia, demonstrating a slightly lower LCOE and requiring 8.6% less installed capacity to achieve financial breakeven. Additionally, the economic impact of pumping depth varies with system scale: in small-scale OTEC systems, LCOE initially decreases with depth before rising beyond an optimal point, while in large-scale systems, it continuously declines and eventually stabilizes. Moreover, capital investment allocation shifts with system size, making pipeline optimization crucial for small-scale systems, whereas minimizing heat exchanger costs is key to enhancing the economic feasibility of large-scale OTEC plants. The results offer guidance for cost-effective OTEC deployment and refrigerant selection, supporting a sustainable energy supply for tropical islands. Full article

This theoretical research study proposes a novel hybrid algorithm that integrates an improved quasi-dynamical oppositional learning mutation scheme into the Mountain Gazelle Optimization method, augmented with chaotic sequences, for the thermal and economical design of a shell-and-tube heat exchanger operating with nanofluids. The Mountain Gazelle Optimizer is a recently developed metaheuristic algorithm that simulates the foraging behaviors of Mountain Gazelles. However, it suffers from premature convergence due to an imbalance between its exploration and exploitation mechanisms. A two-step improvement procedure is implemented to enhance the overall search efficiency of the original algorithm. The first step concerns substituting uniformly random numbers with chaotic numbers to refine the solution quality to better standards. The second step is to develop a novel manipulation equation that integrates different variants of quasi-dynamic oppositional learning search schemes, guided by a novel intelligently devised adaptive switch mechanism. The efficiency of the proposed algorithm is evaluated using the challenging benchmark functions from various CEC competitions. Finally, the thermo-economic design of a shell-and-tube heat exchanger operated with different nanoparticles is solved by the proposed improved metaheuristic algorithm to obtain the optimal design configuration. The predictive results indicate that using water + SiO₂ instead of ordinary water as the refrigerant on the tube side of the heat exchanger reduces the total cost by 16.3%, offering the most cost-effective design among the configurations compared. These findings align with the demonstration of how biologically inspired metaheuristic algorithms can be successfully applied to engineering design. Full article

This study focuses on the compression area of a cryogenic air separation unit (ASU). The mechanism of exergy consumption in the compressor was revealed. The influence of the compression ratio and of the isentropic efficiency per stage give arguments for proper choice of these decisional parameters. For the purchase cost of the compressor, an exergoeconomic correlation based on the exergetic product represented by the compression ratio and the isentropic efficiency as the Second Law coefficient of performance was used instead of the common thermo-economic one based only on the cost of materials. The impact of the suction temperature on the compressor operating performance is shown, making the gap between the compression stage and the associated intercooler. After optimization of the global system, a specific exergy destruction is assigned to each inter-stage compression cooler. To fit this optimum exergy consumption, a design procedure for the inter-stages and final coolers based on the number of heat transfer units (NTU-ε) method and the number of exergy units destroyed (NEUD) is shown. Graphs are provided that make the application of the method straightforward and much easier to use compared to the usual logarithmic mean temperature difference. A 25% increase in the compression ratio per stage leads to a decrease in the exergy efficiency of 3%, while the purchase cost of the compressor rises by 80%. An increase in the isentropic efficiency of the compressor from 0.7 to 0.85 leads to an increase in the exergetic performance coefficient of 21%, while the compressor purchase cost triples. Full article

To fully recover abundant waste heat and reduce the operation cost in liquid-cooled data centers, a Carnot battery consisting of a heat pump (HP) and organic Rankine cycle (ORC) is proposed. Due to the existence of different cycle states for HPs and ORCs, four different cycle combinations are considered. To evaluate and compare their performances, thermo-economic models are developed. Under the design conditions, the optimal working fluid combinations are first determined for each battery. On this basis, thermodynamic and economic performances of the four batteries are analyzed in detail. The results indicate that the system consisting of a subcritical HP/transcritical ORC achieves the highest round-trip efficiency at 76%. Notably, the round-trip efficiency of the system can exceed 100% at low ORC condensing temperatures. Additionally, the system cost is about 767–796 USD/kW∙h, depending on the cycle combinations. Furthermore, the effects of operating parameters on system performances are also investigated. Finally, with the objective of maximum round-trip efficiency, key parameters of four batteries are optimized. The results reveal that the system with a subcritical HP/subcritical ORC attains a maximum round-trip efficiency of 83% after optimization. These research results contribute to the development of green data centers and the reduction of power costs. Full article

Biomass is a viable and accessible source of energy that can help address the problem of energy shortages in rural and remote areas. Another important issue for societies today is the lack of clean water, especially in places with high populations and low rainfall. To address both of these concerns, a sustainable biomass-fueled power cycle integrated with a double-stage reverse osmosis water-desalination unit has been designed. The double-stage reverse osmosis system is provided by the 20% of generated power from the bottoming cycles and this allocation can be altered based on the needs for freshwater or power. This system is assessed from energy, exergy, thermoeconomic, and environmental perspectives, and two distinct multi-objective optimization scenarios are applied featuring various objective functions. The considered parameters for this assessment are gas turbine inlet temperature, compressor’s pressure ratio, and cold end temperature differences in heat exchangers 2 and 3. In the first optimization scenario, considering the pollution index, the total unit cost of exergy products, and exergy efficiency as objective functions, the optimal values are, respectively, identified as 0.7644 kg/kWh, 32.7 USD/GJ, and 44%. Conversely, in the second optimization scenario, featuring the emission index, total unit cost of exergy products, and output net power as objective functions, the optimal values are 0.7684 kg/kWh, 27.82 USD/GJ, and 2615.9 kW. Full article