Search Results (129)

This investigation introduces a conceptual configuration for an innovative combined cooling and power (CCP) arrangement that harnesses waste thermal energy from a supercritical carbon dioxide (sCO₂) power loop through integration with a cascading transcritical CO₂ cycle coupled with a lithium bromide–water vapor absorption chiller (tCO₂/LiBr-H₂O VAR). A systematic comparative assessment of thermodynamic behavior and exergoeconomic characteristics was executed across three configurations: the newly proposed CCP scheme, a hybrid sCO₂/tCO₂ power system, and a conventional standalone sCO₂ engine. Parametric sensitivity analyses were conducted to evaluate how various operating parameters influence overall system effectiveness, while particle swarm optimization (PSO) was employed to determine the optimal exergetic efficiency peaks and minimum unit product costs for each architecture. Findings demonstrate that the proposed CCP topology delivers exergy efficiency enhancements of 8.46% and 1.65% relative to the standalone sCO₂ configuration and the combined sCO₂/tCO₂ arrangement, respectively. Correspondingly, reductions in total product unit costs reach 2.80% and 0.80% for the same comparisons. These outcomes confirm that employing a cascading tCO₂/LiBr-H₂O VAR subsystem as the bottoming cycle represents a compelling solution for cooling and power production. Full article

The rapid expansion of artificial intelligence (AI) has significantly increased the power demand of high-performance data centers. This study constructs an integrated energy system based on Small Modular Reactors (SMRs). The system adopts a supercritical carbon dioxide (S-CO₂) Brayton cycle that directly supplies power for data centers. This work outlines the deep coupling of three core modules: power generation, S-CO₂ energy storage, and waste heat absorption refrigeration driven by residual heat. The design enables coordinated optimization and cascaded utilization of nuclear multi-energy flows. We first build a full thermodynamic model for the whole system, and then formulate dynamic operation scheduling strategies. A 24 h full-condition simulation is carried out. The simulation object is a 125 MW SMR with a 100 MW data center in an off-grid island operation mode. Simulation results for the key performance indicators are as follows: The system cycle thermoelectric conversion efficiency reaches 45.00%. Compared with equal-capacity SMR units equipped with traditional steam cycles, the efficiency rises by 12.5 percentage points. The overall comprehensive energy efficiency hits 82.21%, and the system exergy efficiency is 74.30%. The system achieves a completely self-sufficient power supply without grid support. Its load power deficit rate is only 1.73%. Two operation modes dominate daily system operation: surplus power charging for peak shaving accounts for 60.6% of total runtime, while energy discharging to fill power deficits equates to 38.4%. Waste heat refrigeration requires roughly 93% of the data center’s total cooling demand. This research provides a new technical framework for low-carbon and sustainable construction of next-generation high-performance data centers. The integrated system we propose provides a replicable zero-carbon off-grid energy technical route. It can serve large computing hubs constructed under China’s national “East Data, West Computing” strategy. Full article

Traditional fossil-fuel-based industries, including electric power generation and petrochemical production, are plagued by their inherent carbon dioxide emissions. Current efforts to minimize CO₂ discharge tend to focus on costly capture and sequestration rather than utilizing the process energy and products to produce profitable chemicals. This work describes a concept and design strategy for a comprehensive facility to convert natural gas and air to carbon monoxide, which could be further used to synthesize desirable compounds and fuels. The basic components of the process are an improved supercritical carbon dioxide (sCO₂) electric power plant for driving solid-oxide electrolysis cell (SOEC) reduction in CO₂ to CO. This study examines opportunities for integrating a sCO₂ process with an associated air separation unit (ASU) and an SOEC, including material recycling and heat integration. A Life Cycle Assessment (LCA) is expected to show more positive results than for separate processes. Preliminary economic evaluations provide a profitable process and product route for the combined process, suggesting that carbon emission reduction could be good business. Full article

A design for a small chloride salt fast reactor (sm-MCFR) is presented through the integration of molten salt reactor and small reactor technologies, targeting efficient transmutation of transuranic (TRU) elements in spent nuclear fuel and rapid reactor deployment. The feasibility exploration and research on the design boundaries of sm-MCFR will be conducted in this article. The core adopts a dual-fluid configuration, in which the fuel salt and coolant circulate independently. Chloride salt is selected as the fuel carrier due to its high solubility for heavy metal nuclides and the low neutron absorption cross-section of chlorine, which help to form a hard fast-neutron spectrum and thereby enhance transmutation efficiency. The cooling system employs a direct supercritical carbon dioxide (s-CO₂) cycle, simplifying the overall layout. For the neutronics design, simulations were carried out using the TMCBurnup (TRITON MODEC Coupled Burnup Code). By adjusting the core geometry, fuel salt composition, and reprocessing strategy, the sm-MCFR achieves a hard fast-neutron spectrum but also demonstrates good potential for fuel utilization. In terms of thermal–hydraulic design, the heat exchange effect of the reactor core can be improved by adjusting the proportion of the coolant and the flow direction. The sm-MCFR is expected to become a promising candidate for advanced small reactors that have potential applications in nuclear waste transmutation and distributed energy generation. Full article

To evaluate the techno-economic performance of supercritical carbon dioxide (sCO2) power cycles in particle-based solar tower systems, thermodynamic and techno-economic models were established for four configurations: RC-ORC, RC, RE-ORC, and RE. A one-dimensional design method was used for key printed circuit heat exchangers, and multiple cost correlations with a trimmed-mean treatment were adopted to reduce the influence of extreme cost estimates. The results show that the primary heat exchanger (PHX) dominates system investment, accounting for more than 50% of total cost in all configurations. After screening 48 pure ORC working fluids, Cyclopropane and Trans-butene were identified as the economically preferable fluids for RC-ORC and RE-ORC, respectively. ORC working-fluid selection should therefore consider not only net power output, but also the effect of heat transfer and flow characteristics on intermediate heat exchanger cost. Scale analysis shows that the specific investment cost decreases rapidly over 50–300 MW, while the reduction becomes much smaller above 300 MW. At large scales, RC-ORC and RE-ORC gradually approach 1756.64 $/kW. These results highlight the importance of PHX cost reduction, heat-exchanger-oriented ORC fluid selection, and appropriate system scaling. Full article

Renewable energy sources, such as solar and biomass, represent sustainable alternatives to meet the growing energy demands of the residential sector. This study evaluated the energy, exergy, and environmental performance of two Brayton configurations using supercritical carbon dioxide: a recompression cycle (SRC) and a recompression cycle with intercooling in the main compression (SMC), both coupled to a dual-loop organic Rankine cycle (DORC) and powered by a hybrid solar-biomass thermal system. Mass, energy, and exergy balances were developed, and a life cycle assessment was performed to quantify the environmental impact. The systems were designed to cover a cooling load of 130 kW corresponding to 200 dwellings constructed with Asbestos cement in the Colombian Caribbean region. The results show that both configurations meet the required demand; the SMC-DORC cycle operates at 650 °C, while the SRC-DORC requires 750 °C. The SRC-DORC exhibits higher thermal efficiency (53.24%), while the SMC-DORC achieves a slightly higher exergy efficiency (28.15%). Environmental analysis shows that the construction phase accounts for the majority of the total impact, exceeding 95% of emissions. Overall, both configurations are technically feasible, with the SRC-DORC standing out for its balance between efficiency and environmental impact. Full article

Supercritical carbon dioxide (CO₂) is a promising working fluid for advanced power cycles. However, under high heat flux and low mass flux, its heat transfer performance can deteriorate severely, posing significant risks to system safety and efficiency. Inserting obstacles into flow channels is an effective way to suppress such heat transfer deterioration (HTD). In this study, the body-centered cubic (BCC) lattice structure is taken as an example to investigate the effects of the number and arrangement of BCC units on the flow and heat transfer of supercritical CO₂ using numerical simulation, deep learning, and genetic algorithms. The results show that placing a BCC lattice structure upstream of the HTD temperature peak effectively improves local heat transfer, and the deterioration zone is shifted downstream. For a fixed number of BCC units, different spatial arrangements have little impact on pressure drop and only a limited effect on heat transfer enhancement. However, their influence on the suppression of HTD is very significant. Based on the analysis of the optimal arrangement, an approximate optimal method is obtained, in which BCC structures are inserted sequentially at locations 0.5 to 2 tube diameters (D) upstream of each wall temperature peak. A simplified yet effective design strategy is also proposed: the first BCC structure is placed 0.5 to 2 D upstream of the smooth tube’s temperature peak, and the remaining BCC units are then distributed uniformly along the subsequent flow length. In this way, effective suppression of heat transfer deterioration is achieved. Full article

Supercritical carbon dioxide (sCO₂) is characterized by low viscosity and a peak in specific heat capacity near the pseudo-critical point, making it a promising coolant for microelectronics. However, most existing sCO₂ test rigs are designed for large-scale thermodynamic cycle studies and lack the capability for controlled, localized heat transfer measurements in small channels. This work presents CO₂-SASS (Scientific Assessment of heat transfer in the Supercritical State), a modular, high-pressure test rig designed to measure local heat transfer coefficients and pressure drops in stainless-steel tubes with diameters on the order of 1–3 mm. The system provides independent control of pressure, mass flow and heating, with direct local wall and fluid temperature as well as precise absolute and differential pressure measurements. Particular emphasis is placed on high-accuracy temperature acquisition, including individual thermocouple calibration and cold-junction bias correction. A detailed uncertainty analysis highlights the dominant role of temperature measurement accuracy, especially for small wall–fluid temperature differences near the pseudo-critical point. Full article

The supercritical carbon dioxide (SCO₂) Brayton cycle presents a promising alternative to the traditional steam Rankine cycle, owing to its superior thermal efficiency, high power density, and compact design. As a key component governing system performance, the heat exchanger requires a highly compact and efficient design. This study proposes a novel additively manufactured (AM) wavy microchannel heat exchanger that achieves a compactness of 1670 m²/m³. The design incorporates adaptive flow channels to accommodate SCO₂’s density variation, along with wavy patterns and ribs to enhance thermal performance. A comprehensive fluid–thermal–mechanical coupling numerical analysis was conducted to evaluate its thermal–hydraulic and mechanical performance. Within the Reynolds number range of about 900–6000, the wavy structures improve the heat transfer rate by 21–58%, compared with the straight channel. The maximum effectiveness (ε = 0.66) occurs at a Reynolds number of 900. Compared with other heat exchangers used in the SCO₂ cycle, the overall performance of the hot and cold channels has improved by 12–44% and 3–89%, respectively. Structural analysis confirms that the average total stress under operating conditions remains below the yield strength of the Inconel 617 material, with thermal stress being the dominant contributor. This work underscores the potential of the proposed AM heat exchanger to deliver a superior combination of compactness, thermal–hydraulic performance, and structural integrity for advanced SCO₂ power cycles. 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

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

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

The supercritical carbon dioxide (sCO₂) Brayton cycle has advantages such as a compact system and high energy density. Axial turbines, the key component of the cycle, have lower rotational speeds, pressure ratios and engineering difficulties compared to radial turbines. This study focuses on the initial design parameters and the complete design process of a small-scale axial turbine based on nuclear power and utilizing supercritical carbon dioxide. The design objective of this study is a 150 kW single-stage axial turbine. AXIAL software is used for batch calculations in the preliminary turbine design to determine the most reasonable initial design parameters, including back pressure, rotational speed, average radius, and mass flow rate. These initial parameters serve as the starting point for the overall turbine design process. The one-dimensional design results of the turbine show an isentropic efficiency of 77.15%, and numerical simulations validate the accuracy of this efficiency. Full article

This study reviews the integration of Brayton Cycle (BC) systems in nuclear power generation, emphasizing their potential to enhance thermal efficiency and operational flexibility over traditional Rankine Cycle (RC) systems. Key working fluids, such as helium (He), supercritical carbon dioxide (sCO₂), nitrogen (N₂), and air, are evaluated for their performance, efficiency, and compatibility with nuclear systems. He is recognized for its high thermal conductivity and inertness at elevated temperatures, while sCO₂ demonstrates advantages in compactness and efficiency in midrange temperatures. This article also highlights the importance of compressor designs in optimizing BC performance and reviews, available compressor technologies. Axial and centrifugal compressor designs enable efficient gas compression while managing the thermal and mechanical stresses associated with high-pressure operations in nuclear systems. Combined with variable geometry components and advanced materials, these technologies address the challenges posed by varying load conditions. Despite the promising features of BC systems, several challenges persist, including high leakage rates and material degradation under extreme conditions, which necessitate robust sealing technologies and thorough testing. The insights gained from operational experiences at facilities, such as the Oberhausen II plant and the High-Temperature He Test Facility (HHV), underscore the complexities involved in designing high-temperature gas turbines for nuclear applications. This review concludes that as the nuclear industry evolves, BC systems hold significant promise for contributing to a sustainable energy future, particularly in the context of small modular reactors (SMRs) and microreactors. Further exploration of combined cycle configurations that combine BCs with RCs may enhance overall efficiency and flexibility in power generation. Full article