Configuring hydrogen energy storage and waste heat recovery in data centers directly powered by green electricity constitutes an effective approach to mitigate renewable energy intermittency and improve overall energy efficiency. This study aims to verify the technical and economic feasibility of this strategy in enhancing the operational performance of data center energy systems and reducing operating costs.

Accordingly, a heat pump-assisted organic Rankine cycle is proposed to recover data center waste heat for power generation. At the same time, hydrogen energy storage is used to maintain power supply-demand balance amid fluctuations in renewable energy. Subsequently, an integrated energy-exergy-economic model is developed, and system performance is evaluated at monthly and annual time scales using 2023 meteorological data from Guiyang, China. Furthermore, a sensitivity analysis is conducted to investigate the impacts of varying server utilization rates and six low global warming potential (GWP) working fluids on overall system performance.

The results demonstrate that the system achieves energy and exergy efficiencies of 57.12% and 55.36%, respectively, with a data center energy usage effectiveness of 1.3 and an energy reuse effectiveness of 0.74. Economic analysis indicates a dynamic payback period of 6 years and a net present value of 1.749 6 million yuan. Notably, at a server utilization rate of 90%, the low-GWP R161/Pentane working fluid pair outperforms the high-GWP R134a/R245fa combination.

The synergistic integration of waste heat recovery and hydrogen energy storage effectively improves techno-economic performance, providing a viable technical pathway for data center operators to invest in and deploy supporting energy systems for direct green electricity supply.

To address the issues of insufficient renewable energy integration into the power grid and the high exhaust steam loss in coal-fired power units, a novel Carnot Battery system integrated with a steam ejector is proposed to provide a technical solution for the flexibility transformation of coal-fired units.

This study designed two new systems, System Ⅰ and Ⅱ, utilizing turbine exhaust steam and extraction steam as low-temperature heat sources. System Ⅱ introduces a steam ejector, which uses exhaust from the intermediate-pressure turbine to entrain the exhaust steam, thereby increasing the cold source temperature of the heat storage cycle. Based on the EBSILON Professional, thermodynamic modeling was conducted to compare the coefficient of performance (C_COP), round-trip efficiency (η_RTE), and exergy loss of each system, followed by a techno-economic assessment.

Thermodynamic analysis indicates that the exhaust steam losses of System Ⅰ and Ⅱ are reduced by 38.19 MW and 39.62 MW, respectively, compared to the reference system. Benefiting from the elevated cold source temperature, the C_COP of both systems increased to 1.36 and 1.42. Sensitivity analysis shows that System Ⅱ achieves an optimal round-trip efficiency of 61.51% at a cold source outlet temperature of 55 ℃, an improvement of 2.11 percentage points over the reference system. In terms of techno-economic performance, System Ⅱ performs best, with a dynamic payback period of 9.44 years and a levelized cost of storage as low as 2 094.59 yuan/(MW·h).

The novel System Ⅱ not only effectively reduces energy consumption and improves energy storage efficiency but also demonstrates significant economic competitiveness, which is of great importance for promoting the low-carbon transition of China’s energy industry.

With the popularization of co-combustion of high-alkali coal in Xinjiang, systematic studies on the difference and mechanism of alkali metal poisoning resistance between honeycomb and plate SCR catalysts remain insufficient. Most existing researches are based on the simulation of single alkali metal salts in the laboratory, whereas actual fly ash constitutes a complex mixture. The significant discrepancy between simulated conditions and real flue gas from high-alkali coal combustion results in limited engineering guidance value of relevant research findings.

In this work, actual fly ash from power plants was adopted, and typical flue gas conditions were simulated in a laboratory fixed-bed reactor. The physical and chemical property changes of fresh and aged honeycomb and plate SCR catalysts were compared. Combined with specific surface area measurement, NH₃-TPD analysis of surface acidity, XPS characterization of vanadium valence states and other techniques, the deactivation behaviors of the two catalysts upon alkali metal poisoning were systematically investigated.

Although plate catalysts are more susceptible to sintering deactivation under extreme high-alkali conditions, and bulk diffusion deactivation is difficult to recover via physical or mild chemical regeneration, their denitrification efficiency decays more slowly than that of honeycomb catalysts. At the same alkali loading, the denitrification activity of honeycomb catalysts decreased by 29.5% within 4 800 hours, while that of plate catalysts only dropped by 24.6%. The vanadium valence cycle of honeycomb catalysts is more easily interrupted by alkali metals, which suppresses the “fast SCR pathway” relying on NO→NO₂ conversion. Moreover, their Brønsted acid sites are more prone to neutralization by alkali metals.

Therefore, plate catalysts are the preferred choice for long-term denitrification in industrial scenarios involving co-combustion of high-alkali coal.

This article aims to improve the corrosion resistance of 304 stainless steel in high-temperature chloride molten salts, clarify the application effect and corrosion inhibition mechanism of aluminum powder as a corrosion inhibitor, and provide a practical reference for the material protection of solar thermal storage molten salt systems.

The high-temperature electrochemical corrosion behavior of 304 stainless steel was investigated in a ternary chloride molten salt (NaCl-KCl-MgCl₂) at 700 ℃ with the addition of aluminum powder at mass fractions of 0, 1%, 2%, and 5% respectively. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were employed to evaluate the corrosion kinetics and interfacial characteristics. The surface and cross-sectional morphologies, elemental distribution, and phase composition of corrosion products were analyzed using scanning electron microscopy combined with energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD).

The addition of aluminum powder significantly suppressed the corrosion of 304 stainless steel. With 5% aluminum powder addition, the corrosion current density decreased from 299.98 mA/cm² (without addition) to 31.673 mA/cm², representing a reduction of 89.4%. The polarization resistance increased markedly from 0.348 Ω (without aluminum) to 2.974 Ω (with 5% aluminum), indicating enhanced resistance to corrosion reactions. Electrochemical impedance spectroscopy (EIS) analysis revealed that the addition of aluminum altered the corrosion control mechanism from diffusion-controlled (without aluminum) to a dual-layer synergistic protection system at higher aluminum contents. After 100 h of corrosion，the thickness of the internal diffusion layer was significantly reduced from 150 μm (without aluminum) to 36 μm (with 5% aluminum powder addition). XRD and SEM/EDS analysis showed that at aluminum additions of 2% and 5%，a continuous and dense Al₂O₃ layer formed on the surface，while aluminum diffused inward to form an aluminum-rich layer and intermetallic AlNi₃ phase within the alloy subsurface. This dual-layer structure effectively suppressed the outward diffusion of Cr and Fe，thereby mitigating corrosion.

The corrosion inhibition mechanism of aluminum powder involves a synergistic protective process. Aluminum preferentially reacts with oxidizing impurities (e.g., moisture and oxygen) in the molten salt, forming a stable Al₂O₃ film on the alloy surface. Simultaneously, a portion of aluminum diffuses inward, creating an aluminum-rich layer and precipitating AlNi₃ phases, which together act as an internal diffusion barrier. This combined surface film and internal diffusion barrier system effectively blocks the outward migration of Cr and Fe, substantially reducing the corrosion rate. The results demonstrate that adding aluminum powder to chloride molten salts is a simple and effective strategy to enhance the corrosion resistance of 304 stainless steel. Future work should focus on the evaluation of the long-term durability and erosion resistance of this protective system under dynamic flow conditions, to facilitate its practical applications in concentrating solar power systems.

With the rapid growth of renewable energy under the goals of carbon peaking and carbon neutrality, power systems face increasing demand for long-duration energy storage and flexible peak regulation. Electrically heated solid particle thermal energy storage (TES) is a promising option because it offers high operating temperature, wide storage temperature range, low-cost storage media, good thermal stability, clean electric-to-thermal conversion, and strong potential for integration with renewable energy systems and coal-fired power plants. This paper aims to clarify the research progress, major bottlenecks, and future directions of this technology.

This paper reviews electrically heated solid particle TES from the perspectives of heating principles, representative devices, application scenarios, and key scientific and engineering issues. Two major routes, resistance heating and induction heating, are discussed in detail. For resistance heating, both indirect and direct modes are considered. Indirect resistance heating transfers heat from electric heating elements to particles through conduction, convection, and radiation. It has advantages such as simple structure, mature equipment, and good controllability, but it also suffers from additional thermal resistance and heat loss. Direct resistance heating allows conductive particles or conductive particle networks to generate Joule heat directly, which improves heating compactness and electric-to-thermal efficiency, while also introducing challenges related to conductivity stability, local overheating, oxidation resistance, and the formation of reliable conductive paths. Induction heating provides non-contact heating and rapid thermal response, and is attractive for high-temperature applications. However, its performance depends strongly on frequency, magnetic field intensity, coil design, particle size, electrical conductivity, magnetic permeability, and temperature-dependent material properties. In addition, induction heating systems often face higher equipment cost, cooling demand, and lower overall efficiency in practical applications. Representative devices for solid particle heating, including tubular heaters, plate heaters, fluidized-bed heaters, and moving-bed heaters, are also summarized. Tubular and plate heaters are relatively mature and suitable for small- and medium-scale systems, whereas fluidized-bed and moving-bed configurations show better heat transfer performance and greater potential for high-power and continuous operation. At the same time, they involve more complex issues such as particle flow stability, pressure drop, abrasion, temperature uniformity, and model accuracy. This paper further discusses key challenges, including high-temperature particle flow and heat transfer mechanisms, optimization of electric heating efficiency, durability of particle materials under thermal cycling, cost control, and coordinated operation with coal-fired power plants.

Electrically heated solid particle TES is a promising technical route for renewable energy integration, long-duration energy storage, and flexible operation of coal-fired power plants. Resistance heating is currently more mature and economically competitive, while induction heating has advantages in non-contact heating, rapid response, and high-temperature adaptability, but still requires progress in efficiency improvement, cost reduction, and particle material matching. Future research should focus on multi-field coupled particle flow and heat transfer, low-cost and high-performance particle materials, modular electric heating devices, heat loss control, and coordinated control strategies, so as to promote the scale-up, industrialization, and commercialization of this technology.

This study aims to enrich the experimental study of the ORC using mixture working fluids and analyze its transient and steady-state operating characteristics.

A 4-kW organic Rankine cycle (ORC) prototype using R236fa/R123 was tested to obtain the transient and steady-state operating data.

The results of the ORC system at different mixture concentrations reveal that the operation characteristics of the ORC with mixed working fluids are consistent with those using a pure working fluid. The adjustment of the working fluid mass flow rate significantly affects the system output power, while it has a limited impact on the thermal efficiency. The ORC system operates relatively stable with the variation in the mixture concentration, as it has a minimal effect on both the output power and thermal efficiency. With the increase in the R236fa mass fraction, the expander inlet pressure is stable while its outlet pressure gradually increases, resulting in high pressure ratios. This phenomenon indicates that adopting the expander with a larger internal volume ratio can optimize the ORC performance. The trade-off between the exergy destructions of the evaporator and condenser at different mixture concentrations is the main factor determining the system performance. The temperature glide caused by the condenser pressure drop limits the attribution of the mixture working fluid to optimize the system performance.

In the design and operation of mixed-working-fluid ORC systems, it is crucial to consider the matching of the condenser pressure drop and the working fluid inherent properties.

The carbon capture pretreatment system faces challenges such as high energy consumption, unstable purification efficiency, and significant fluctuations in SO₂ absorption efficiency due to variations in pH value of washing solution. This study proposes a hybrid modeling method combining mechanism models with data-driven by taking the carbon capture pretreatment system in a power plant as the research object.

By integrating chemical reaction kinetics and decision tree algorithms, the model is implemented in Python to predict key parameters accurately, including the pH value of the washing solution and the SO₂ mass concentration at the system outlet.

The model yields a correlation coefficient of 0.85 and 0.80 for the pH value of the washing solution and the SO₂ mass concentration at the system outlet, respectively. The values fall within an acceptable error band, indicating the proposed model has good simulation performance. Moreover, a sensitivity analysis driven by baseline plant data further reveals that the model faithfully reproduces the system response to perturbations in inlet flue-gas temperature, liquid-to-gas ratio, and alkali feed rate.

These outcomes furnish a quantitative foundation for subsequent optimization of the CO₂-capture pretreatment system, offering clear avenues for energy minimization and robust steady-state operation.

In practical energy and chemical engineering systems, pipeline layouts often exhibit complex multi-directional configurations due to equipment arrangement, spatial constraints, and process requirements, rather than simple straight horizontal or vertical sections. This is particularly evident in applications such as compact heat exchangers for supercritical carbon dioxide (S-CO₂) Brayton cycles, nuclear reactor cooling circuits, and chemical transport pipelines, where the working fluid frequently undergoes abrupt changes in flow direction. Among these configurations, the L-shaped bend, a classic directional-changing structure that connects horizontal and vertical pipe sections, is especially common and plays a crucial role in achieving spatial redirection of the working fluid. Therefore, investigating the heat transfer characteristics of S-CO₂ in L-shaped bends is of significant importance. This study aims to investigate the effect of buoyancy-induced density stratification in a heated horizontal section on the subsequent heat transfer in a vertical upward flow under different experimental parameters.

An experimental system with high expandability was established, featuring a single-cycle S-CO₂ heat transfer test platform utilizing stainless steel circular pipes with adjustable lengths and bend angles. Experiments were conducted to study the flow and heat transfer characteristics of S-CO₂ inside a horizontal-to-vertical L-shaped turning pipe.

The experimental results reveal two distinct types of “asymmetric heat transfer deterioration” in the turning pipe: one characterized by asymmetry in the severity of deterioration, and the other by asymmetry in its location. When the wall heat flux is increased, wall temperature peaks indicating heat transfer deterioration appear in the vertical section, with unequal peak values on the two sides, representing asymmetry in severity. A further increase in wall heat flux shifts the deterioration position toward the inlet, while the enthalpy at which deterioration initiates remains unchanged, indicating that the wall heat flux does not affect the onset enthalpy of deterioration. When the heat flux is raised sufficiently for the deterioration to advance to the inlet of the vertical section, the wall temperature peak on the inner side occurs earlier than that on the outer side, demonstrating asymmetry in the location of deterioration.

The study demonstrates that asymmetry in severity originates from non-uniform cross-sectional mass flow distribution caused by temperature stratification extending from the horizontal section. In contrast, asymmetry in location occurs under high-temperature and high-heat-flux conditions due to the earlier fulfillment of deterioration criteria within the inner-side boundary layer. This research elucidates the coupling effect between buoyancy and flow redirection in L-shaped pipes, providing an experimental basis for the design of related heat exchange equipment.

Temperature fluctuations within the underground cavern have a significant effect on the efficiency of compressed air energy storage power stations and the structural safety of the cavern. Installing the heat exchanger inside the cavern is one of the effective methods to suppress air temperature fluctuations.

A compressed air thermodynamic model that takes into account the heat transfer of internal heat exchangers is established to investigate the effects of different cold and hot water configuration strategies on air temperature and pressure changes inside the cavern.

The results show that by using low-temperature water during the charging phase and high-temperature water during the discharging phase, the internal heat exchanger can effectively suppress the compression heat effect and expansion cooling effect of the air, thereby reducing the range of air temperature fluctuations. Specifically, when cold water (33 ℃) and hot water (90 ℃) are introduced into the heat exchanger during the charging and discharging, respectively, the temperature difference of air can be reduced from 43.9 ℃ without using heat exchangers to below 15.0 ℃. Further analysis indicates that adjusting the cold water utilization period to the latter half of the charging phase and concentrating the hot water utilization time towards the end of the discharging phase can effectively increase the heat transfer temperature difference between the heat exchanger and the air, further reducing the air temperature difference at the end of charging and discharging.

In summary, the reasonable configuration of the operating strategy of the internal heat exchanger, especially the optimization of cold and hot water utilization times, can effectively improve the energy storage capacity and power generation capacity of compressed air energy storage systems.

Against the backdrop of global efforts to address climate change and actively promote the strategic goals of “carbon peak and carbon neutrality”, the clean and low-carbon transformation of the energy system has become a core issue for national development. Accelerating the low-carbon transformation of the coal-fired power industry and precisely reducing carbon emission intensity are key challenges in achieving climate goals. However, there are significant differences in the carbon emission characteristics of different types of coal-fired units, and their carbon emission levels and the emission reduction effects of coupling carbon capture technology have not been clearly compared. To reveal and compare the carbon emission intensities of different types of coalfired units, a carbon emission intensity calculation model applicable to different types of coal-fired units coupled with carbon capture and storage (CCS) systems was constructed.

The carbon emission intensities of typical coal-fired units such as 300 MW, 600 MW, 1 000 MW, double-reheat and IGCC at different load rates, as well as the carbon emission intensities after coupling with CCS systems, were compared and analyzed.

The research results show that at higher load rates, IGCC units have a lower carbon emission intensity, reaching 703 g/(kW·h) at 100% load rate, while the 300 MW unit has the highest carbon emission intensity, reaching 812 g/(kW·h). When the load rate decreases, the carbon emission intensity of the IGCC unit increases rapidly, reaching 948 g/(kW·h) at 50% load rate. The double-reheat unit has the lowest carbon emission intensity at 50% load rate, which is 781 g/(kW·h). CCS technology has a strong carbon emission reduction capacity and is an important means for the low-carbon transformation of coal-fired power. At 100% load rate, a 50% carbon capture rate can reduce the carbon emission intensities of 1 000 MW units, double-reheat units and IGCC units by 334, 329 and 295 g/(kW·h) respectively. Similarly, at a 50% load rate, a 50% carbon capture rate can respectively reduce the carbon emission intensity of 1 000 MW units, double-reheat units and IGCC units by 352, 358 and 379 g/(kW·h).

This study, through the construction of analytical models and systematic comparisons, quantitatively reveals the compound influence mechanism of the technical route of coal-fired units, operating load rate, and CCS coupling strategy on carbon emission intensity. In future power systems with a high proportion of renewable energy, coal-fired units will undertake more peak shaving and frequency regulation tasks. Quantifying the carbon emission differences of coal-fired units not only helps optimize the development path of low-carbon transformation in coalfired power, but also provides solid theoretical support and a decision-making basis for achieving the “dual carbon” goals.