Search Results (316)

The nutritional composition of insect-derived meals is strongly influenced by insect diet, while defatting can further modulate nutritional quality. However, some defatting methods, such as supercritical CO₂ extraction, depend on sample properties, including density and macromolecule distribution. Therefore, diet-induced changes may affect lipid extraction efficiency and kinetics, a relationship that remains unexplored. This study evaluated the impact of feeding Hermetia illucens larvae with by-products from olive oil industry (olive leaves, OL, at 15, 30 or 50%; dry full-fat olive pomace, OP, at 30, 50, 70, 90%) or quinoa processing (husk, QH, at 15, 30 or 50%) on supercritical CO₂ defatting performance, meal composition, amino acid profile and digestibility. Despite diet-induced variations in lipid accumulation, defatted kinetics mainly depended on the content and solubility of extractable material, while differences in packed bed microstructure had a minor effect. Protein-rich meals were obtained (25–35%), although most diets reduced protein content, except OP50. QH15 and OP30 worsened essential amino acids in meals, whereas OP50 improved them. Chitin content increased, especially for OP-based meals. Digestibility slightly improved with OP30, OP70, QH15, and QH50. These results show the potential of olive oil and quinoa by-products to be up-cycled by H. illucens into high-value insect meals, without compromising the processing by supercritical CO₂ defatting, supporting sustainable insect-based food and feed production. Full article

Refuse-derived fuel (RDF) presents a viable strategy to concurrently address the challenges of municipal solid waste management and the need for alternative energy. In this context, the present review systematically synthesizes recent advances in RDF preparation, combustion behavior, and efficient utilization technologies. The study examines the full chain of RDF production—including waste selection, mechanical/optical/magnetic sorting, granulation, briquetting, and chemical modification—highlighting how pretreatment technologies influence fuel homogeneity, calorific value, and emissions. The thermochemical conversion characteristics of RDF are systematically analyzed, covering the mechanism differences among slow pyrolysis, fast pyrolysis, flash pyrolysis, pyrolysis mechanisms, catalytic pyrolysis, fragmentation behavior, volatile release patterns, and kinetic modeling using Arrhenius and model-free isoconversional methods (e.g., FWO). Special attention is given to co-firing and high-efficiency combustion technologies, including ultra-supercritical boilers, circulating fluidized beds, and rotary kilns, where fuel quality, ash fusion behavior, slagging, bed agglomeration, and particulate emissions determine operational compatibility. Integrating recent findings, this review identifies the key technical bottlenecks—feedstock variability, chlorine/sulfur release, heavy-metal contaminants, ash-related issues, and the need for standardized RDF quality control. Emerging solutions such as AI-assisted sorting, catalytic upgrading, optimized co-firing strategies, and advanced thermal conversion systems (oxy-fuel, chemical looping, supercritical steam cycles) are discussed within the broader context of carbon reduction and circular economy transitions. Overall, RDF represents a scalable, flexible, and high-value waste-to-energy pathway, and the review provides insights into future research directions, system optimization, and policy frameworks required to support its industrial deployment. Full article

Supercritical carbon dioxide (SC-CO₂) power cycles offer a promising solution for offshore platforms’ gas turbine waste heat recovery due to their compact design and high thermal efficiency. This study proposes a novel parallel-preheating recuperated Brayton cycle (PBC) using SC-CO₂ for waste heat recovery on offshore gas turbines. An integrated energy, exergy, and economic (3E) model was developed and showed good predictive accuracy (deviations < 3%). The comparative analysis indicates that the PBC significantly outperforms the simple recuperated Brayton cycle (SBC). Under 100% load conditions, the PBC achieves a net power output of 4.55 MW, while the SBC reaches 3.28 MW, representing a power output increase of approximately 27.9%. In terms of thermal efficiency, the PBC reaches 36.7%, compared to 21.5% for the SBC, marking an improvement of about 41.4%. Additionally, the electricity generation cost of the PBC is 0.391 CNY/kWh, whereas that of the SBC is 0.43 CNY/kWh, corresponding to a cost reduction of approximately 21.23%. Even at 30% gas turbine load, the PBC maintains high thermoelectric and exergy efficiencies of 30.54% and 35.43%, respectively, despite a 50.8% reduction in net power from full load. The results demonstrate that the integrated preheater effectively recovers residual flue gas heat, enhancing overall performance. To meet the spatial constraints of offshore platforms, we maintained a pinch-point temperature difference of approximately 20 K in both the preheater and heater by adjusting the flow split ratio. This approach ensures a compact system layout while balancing cycle thermal efficiency with economic viability. This study offers valuable insights into the PBC’s variable-load performance and provides theoretical guidance for its practical optimization in engineering applications. Full article

This study investigates the thermodynamic performance of two power-generation systems driven by a geothermal heat resource. The first configuration is an organic Rankine cycle (ORC) employing cyclopentane, R152a, and R1233zd as working fluids, while the second utilizes a supercritical carbon dioxide (s-CO₂) Rankine cycle. Detailed energy and exergy analyses for each working fluid were carried out using the EBSILON^® Professional simulation. Among the ORC fluids, cyclopentane demonstrated the most favorable performance. In the ORC system, thermal and exergy efficiencies reached up to 29.58% and 70.51%, respectively. However, in the s-CO₂ Rankine cycle, thermal and exergy efficiencies were found to be 20.29% and 47.77%, respectively. Also, it was determined that the ORC and s-CO₂ Rankine were economically viable for investment, with payback periods of 4.2 years and 2.26 years, respectively. Full article

Against the backdrop of global energy transition and increasingly severe environmental conditions, developing clean and efficient energy systems has become crucial. This study aims to investigate a solar tower receiver tri-generation (STRT) system combining supercritical CO₂ (S-CO₂) Brayton cycle and organic Rankine cycle (ORC), with the objective of achieving the production of electricity, hydrogen, and oxygen. The modeling of the STRT system is completed by using Ebsilon, and the performance of the STRT system is analyzed. The results show that the output power and efficiency of the S-CO₂ Brayton cycle are 62.29 MW and 48.3%, respectively. The net power and efficiency of ORC are 8.02 MW and 16.35%. The hydrogen and oxygen production rates of the STRT system are 183.8 kg·h⁻¹ and 1470.4 kg·h⁻¹, respectively. The STRT system shows stable and effective operation performance throughout the year. Through the exergy analysis, the exergy losses and exergy efficiencies of different components of the STRT system are obtained. The solar tower has the largest exergy loss (218.85 MW) and the lowest exergy efficiency (63%). The levelized electricity cost and the levelized hydrogen cost of the STRT system are 0.0788 USD·kWh⁻¹ and 2.97 USD·kg⁻¹ with a recovery period of 8.05 years, which reveal the economic competitiveness of the STRT system. Full article

The paper presents a comparative economic and environmental assessment of high-temperature steam turbine technologies (subcritical, supercritical, ultra-supercritical, and advanced ultra-supercritical cycles) within the energy transition. The research employs a model-based analysis to evaluate the cost of electricity production across countries with divergent environmental, social and governance (ESG) strategies, reflected in their carbon pricing mechanisms. The developed model estimates the economic feasibility and optimal timing for the transition to high-efficiency technologies, based on the projected fuel cost dynamics. Within the framework of the model, the optimal energy transition timings for implementing advanced ultra-supercritical steam turbine technologies were established: 2031 for the energy transition model in the Russian Federation (a country with developing ESG principles) and 2018 for the model in the Czech Republic (a country with an emerging ESG strategy). The results indicate that while carbon pricing mechanisms influence economic feasibility, hydrocarbon fuel costs remain the predominant factor. The study concludes that the enhancement of conventional generation technologies aligns with all three pillars of the ESG framework and facilitates the transition to a sustainable development model for the energy sector and the national economy. Full article

This study investigates the effect of Reynolds number on unsteady buffet characteristics of the OAT15A supercritical airfoil under transonic conditions (Ma = 0.73, AOA = 3.5°) using DDES based on the SST k-ω turbulence model coupled with the γ-Reθ transition model. Results show that, compared with fully turbulent conditions, the free-transition cases exhibit a more downstream shock position and higher lift. Under fully turbulent conditions, higher Reynolds numbers drive the shock downstream and enhance its stability. Under free-transition conditions, the shock moves downstream at low Reynolds numbers but shifts upstream at high Reynolds numbers due to changes in the transition location. During the unsteady buffet cycle at low Reynolds numbers, the lift increases as the shock moves downstream and the separation region shrinks. The lift reaches its maximum when the separation is minimal, corresponding to a quiet flow state with weak acoustic emission. As the lift decreases, a large separation region forms behind the shock, forcing the shock upstream and reducing the lift to its minimum. At high Reynolds numbers, the buffet cycle changes: the shock becomes more stable; trailing-edge vortex shedding intensifies; lift oscillation amplitude decreases; and buffet frequency increases. 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

In the context of the zero-carbon transition, this article provides a comprehensive review of Organic Rankine Cycle (ORC) technologies for low-grade heat recovery and conversion to power. It surveys a wide range of renewable and waste heat sources—including geothermal, solar thermal, biomass, internal combustion engine exhaust, and industrial process heat—and discusses the integration of ORC systems to enhance energy recovery and thermal efficiency. The analysis examines various configurations, from basic and regenerative cycles to advanced transcritical and supercritical designs, cascaded systems, and multi-source integration, evaluating their thermodynamic performance for different heat source profiles. A critical focus is placed on working fluid selection, where the landscape is being reshaped by stringent regulatory frameworks such as the EU F-Gas regulation, driving a shift towards low-GWP hydrofluoroolefins, natural refrigerants, and tailored zeotropic mixtures. The review benchmarks ORC against competing technologies such as the Kalina cycle, Stirling engines, and thermoelectric generators, highlighting relative performance characteristics. Furthermore, it identifies key trends, including the move beyond single-source applications toward integrated hybrid systems and the use of multi-objective optimization to balance thermodynamic, economic, and environmental criteria, despite persistent challenges related to computational cost and real-time control. Key findings confirm that ORC systems significantly improve low-grade heat utilization and overall thermal efficiency, positioning them as vital components for integrated zero-carbon power plants. The study concludes that synergistically optimizing ORC design, refrigerant choice in line with regulations, and system integration strategies is crucial for maximizing energy recovery and supporting the broader zero-carbon energy transition. Full article

This study presents the first comprehensive investigation of direct supercritical water oxidation (SCWO) of microalgae biomass integrated with photobioreactor oxygen recovery for sustainable energy production. Laboratory-scale experiments were conducted on Nannochloropsis gaditana at optimized conditions (650 °C, 24 MPa, 1 min residence time), achieving extraordinary conversion efficiency of 99.99% at biomass concentrations as low as 0.5 wt%. Process simulation using Aspen Plus demonstrated that this integrated photobioreactor-SCWO system can recover oxygen produced during photosynthesis, reducing compressor energy demands by 10–15% compared to conventional air-fed systems. The coupled system achieved net thermal power outputs of 47–66 kW from a 1 kg/min microalgae feed at 5–10 wt% biomass concentration, corresponding to an overall system thermal efficiency of approximately 18%. CO₂ recovery via mono-ethanolamine absorption enabled 70–80% carbon cycle closure, while simultaneous nutrient recycling through the aqueous phase supports sustainable circular economy principles. This coupled photobioreactor-SCWO process represents an efficient pathway for energy recovery from wet microalgae biomass, eliminating the energy-intensive drying requirement (typically 60–70% of conventional processing energy) and achieving complete mineralization of organic compounds. The system demonstrates technical and energetic viability for scaling to pilot demonstration scale. Full article

Rice bran, a rice milling by-product, is a rich source of bioactives such as tocopherols and γ-oryzanol, with promising antioxidant properties. This study compared three extraction techniques—Soxhlet, maceration, and supercritical CO₂ (SC-CO₂)—to identify the method offering the best balance of rice bran oil (RBO) recovery, composition, and sustainability. Although all methods yielded similar oil quantities (~9.5–10.8%), SC-CO₂ extraction achieved superior preservation of bioactives, with the highest tocopherol (116.9 µg/g) and γ-oryzanol (13.2 mg/g) levels. Antioxidant capacity, assessed via FRAP, ABTS, and DPPH assays, was consistently higher in SC-CO₂-extracted oil. The fatty acid profile further confirmed the advantages of SC-CO₂ extraction, with the oil showing a high proportion of unsaturated fatty acids (86.3%) and low saturated content (13.6%). In contrast, Soxhlet- and maceration-extracted oils contained higher saturated fractions (56.5% and 60.1%, respectively) and lower unsaturated content, reflecting the impact of thermal and solvent exposure on the lipid composition. Environmental impacts were quantified through cradle-to-gate life cycle assessment (LCA), showing that SC-CO₂ extraction led to the lowest ecological burden due to its solvent-free process and lower energy demand. Normalizing impacts on both oil yield and bioactive content further highlighted its advantages. These findings place SC-CO₂ extraction as a green, efficient alternative for valorizing rice bran, yielding a high-quality, antioxidant-rich oil suitable for food and cosmetic applications. The integrated chemical and environmental evaluation underscores the potential for a sustainable bioeconomy, effectively turning agricultural residue into functional ingredients. Full article

This paper presents a novel, integrated supercritical CO₂ system for shale gas development, comprising a supercritical CO₂ shale gas extraction system, a gas turbine system, a supercritical CO₂ power generation system, and a transcritical CO₂ refrigeration system. A comprehensive thermodynamic and economic analysis is conducted for this integrated energy development system. To enhance system performance across multiple dimensions, three objective functions are proposed for optimization: exergy efficiency, levelized energy cost (LEC), and heat transfer area per unit power output (APR). First, the effects of key operating parameters—including the gas turbine pressure ratio, gas turbine inlet temperature, supercritical CO₂ pressure ratio, the temperature difference between flue gas and the supercritical CO₂ top cycle, and the temperature difference between flue gas and the supercritical CO₂ bottom cycle—on system performance were analyzed through parametric studies. Next, the optimal system parameters were determined using a multi-objective optimization method based on a genetic algorithm. The optimization results reveal that, when exergy efficiency and LEC are used as dual-objective functions, the system achieves an optimal exergy efficiency of 60.5% and an LEC of 6.3 cents/(kW·h). Furthermore, when exergy efficiency, APR, and LEC are considered as objective functions, the system attains an optimal exergy efficiency of 59.5%, an APR of 0.21 m²/kW, and an LEC of 6.3 cents/(kW·h). The compound shale gas development system proposed in this paper demonstrates excellent economic viability, environmental sustainability and operational efficiency. The research outcomes offer an innovative solution for the development of shale gas and contribute to the advancement of research on new energy systems. Full article

Agri-food residues have accumulated globally at unprecedented scales, generating environmental pressures and resource inefficiencies, a core problem addressed in this review, while simultaneously representing rich, underutilized reservoirs of health-promoting phytochemicals. This review synthesizes recent advances (2016–2025) in the green extraction, characterization, and biological validation of phytochemicals from plant-based residues, including polyphenols, flavonoids, carotenoids, alkaloids, and dietary fibers from key sources such as grape pomace, citrus peels, coffee silverskin, pomegranate peel, cereal brans, and tropical fruit by-products. Emphasis is placed on sustainable extraction methods: ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), pressurized liquid extraction (PLE), supercritical CO₂ extraction (SFE), and natural deep eutectic solvents (NADES), which enable efficient recovery while minimizing environmental impact. In vitro, in vivo, and clinical studies demonstrate that residue-derived compounds exert antioxidant, anti-inflammatory, metabolic-regulating, and prebiotic effects, contributing to health in general and gut microbiota modulation. Integrating these bioactives into functional foods and nutraceuticals supports sustainable nutrition and circular bioeconomy goals by reducing food waste and promoting health-oriented valorization. Regulatory advances, including approvals from the European Food Safety Authority (EFSA) and the U.S. Food and Drug Administration (FDA) for ingredients such as olive phenolics, citrus flavanones, and coffee cascara, further illustrate increasing translational readiness. The convergence of green chemistry, biorefinery design, and nutritional science positions agri-food residues as pivotal resources for future health-promoting and environmentally responsible diets. Remaining challenges include scaling cost-effective green processes, harmonizing life cycle assessment protocols, expanding toxicological datasets, and conducting longer-term clinical trials to support safe and evidence-based commercialization. Full article

Heat exchangers are key components of advanced waste-heat recovery energy systems that operate on low-boiling working fluids. The efficiency and cost of power plants depend directly on their design characteristics. Increasing the heat-transfer surface area, on the one hand, reduces temperature differences and improves cycle efficiency, but on the other hand increases material consumption and equipment cost. For given fluid parameters and heat-exchanger duty, the required surface area is determined by the type of heat exchanger, the choice of device, the shape of the enhanced heating surface, and the methods of heat-transfer intensification. This paper provides a comprehensive analysis of the current state of heat exchangers for low-boiling working fluids and discusses their areas of application. A methodology has been developed for optimizing the main design characteristics of heat exchangers, including a search algorithm aimed at minimizing the total costs of equipment production and operation. Using this methodology, computational studies were carried out for advanced energy cycles with low-boiling working fluids (organic Rankine cycles, recompression supercritical CO₂ (s-CO₂) Brayton cycle). The relationships of weight, size, and cost parameters of heat exchangers for waste-heat recovery cycles using low-boiling fluids to exhaust-gas temperatures and external economic factors were obtained. Optimal channel geometric parameters and heat-exchanger design types were identified that ensure minimal material consumption and cost while delivering the required heat-transfer performance. Recommendations are formulated for selecting and designing heat exchangers for waste-heat recovery power plants using low-boiling working fluids, the implementation of which will improve their efficiency and reduce costs. Full article

This paper innovatively presents an integrated nuclear-powered supercritical carbon dioxide (S-CO₂) system for aircraft carriers, replacing the conventional secondary-loop steam Rankine cycle with a regenerative S-CO₂ power cycle. The system comprises two modules: a nuclear reactor module and a S-CO₂ power module. Comprehensive thermodynamic, economic, and compactness analyses were conducted, using exergy efficiency, levelized energy cost (LEC), and heat transfer area per unit power output (APR) as objective functions for optimization. Parameter analysis revealed the influence of key operating parameters on system performance, and a multi-objective optimization approach based on genetic algorithms was employed to determine optimal system parameters. The results indicate that the system achieves an exergy efficiency of 45%, an APR of 0.168 m² kW⁻¹, and an LEC of 2.1 cents/(kW·h). This high compactness, combined with superior thermodynamic and economic performance, underscores the feasibility of the S-CO₂ system for integration into nuclear-powered aircraft carriers, offering significant potential to enhance their overall performance and operational efficiency. Full article