Latest ArticlesAs an important path for the combination of renewable energy and hydrogen energy, the technology coupling wind solar power with hydrogen production and storage through water electrolysis has shown great potential in energy transformation. However, large-scale grid-connected hydrogen production stations have problems such as uneven power distribution and insufficient consideration of the differences in response characteristics between alkaline and proton exchange membrane (PEM) electrolyzers. Therefore, this paper proposes an optimized scheduling strategy for the double-layer array of wind-solar hydrogen production hybrid electrolyzers. Firstly, with the goal of maximizing the net income of the system, a multi-time-scale optimization strategy is adopted to allocate the power of the wind and solar hydrogen production system. Secondly, considering the differences in hydrogen production efficiency and dynamic response characteristics between the alkaline and the PEM electrolyzers, optimal scheduling is performed for the array of alkaline and PEM hybrid electrolyzers. As a result, based on the two-layer optimization strategy, the ratio of the on-grid electricity generation to the power generation of the grid-connected wind and solar hydrogen production and storage system is infinitely close to the set value of 40%, and the comprehensive power curtailment rate is 1.89%, which greatly reduces the curtailment rate of wind and solar power in the system. The operational characteristics of the alkaline and PEM electrolyzers are fully utilized to achieve the full utilization of fluctuating renewable energy and enhance the stability and safety of the hydrogen production system operation.
To address the challenges of flow regulation and pressure mismatch in conventional solid-gas coupled hydrogen storage reactors, this study proposes a novel reactor configuration incorporating the Venturi entrainment effect. A multi-physics coupled numerical model is developed to investigate the influence of nozzle structural parameters and key operating conditions on hydrogen release performance, and comparative analyses are conducted against single-mode hydrogen storage systems. The results demonstrate that nozzle geometry has a significant nonlinear effect on entrainment performance. Specifically, a nozzle with a length of 9~13 mm and diameter of approximately 0.4 mm achieves an optimal balance between system stability and entrainment efficiency. Increasing the high-pressure hydrogen inlet pressure enhances the instantaneous flow rate but reduces the entrainment ratio. Higher outlet backpressure improves the entrainment ratio but suppresses the jet strength and dynamic response. Elevating the thermal management temperature of the solid-state hydrogen storage unit accelerates the initial hydrogen release rate, but its influence on the later stages is limited. With a solid-to-gas ratio of 1:1, the coupled hydrogen storage scheme reduces the volume by approximately 34.4% and the compression energy consumption by about 41.7% compared to a 20 MPa gaseous hydrogen storage scheme. Compared to the single-mode solid-state storage scheme, thermal management energy consumption of this coupled scheme reduces by nearly 50.0%, demonstrating a significant advantage in energy efficiency synergy. This study provides a theoretical foundation and engineering guidance for the structural optimization and operational strategy development of solid-gas coupled hydrogen storage reactors.
To enhance the heat exchanger efficiency in a carbon dioxide energy storage system, a printed circuit heat exchanger (PCHE) was employed as the core heat transfer component, with binary nitrate molten salt (solar salt) serving as the cold-side fluid and supercritical carbon dioxide (S-CO2) as the hot-side fluid. This study aims to investigate the key factors influencing the internal heat transfer process in PCHE and optimize the dominant structural parameters governing its thermal performance, thereby addressing the performance bottlenecks of heat exchangers in such energy storage systems.
Three key structural parameters of the Zigzag PCHE, such as channel diameter, turning angle, and number of turning cycles, were selected as independent variables. The overall heat transfer coefficient K (a core indicator of heat transfer capacity) and the ratio of the overall heat transfer coefficient to pressure drop K/ΔP (a key metric for evaluating the trade-off between heat transfer and flow resistance) were designated as response variables. A three-factor, three-level response surface methodology (RSM) was established to quantitatively analyze the effects of the three structural parameters and their pairwise interactions on the response variables. Parameter optimization of the heat exchange channels was subsequently performed based on the analytical results.
Within the specified parameter ranges (channel diameter: 1.0~2.0 mm, turning angle: 5°~30°, number of turning cycles: 6~10), the results indicate that reducing the channel diameter, increasing the turning angle, or increasing the number of turning cycles can effectively improve the heat transfer efficiency of the Zigzag PCHE. Statistical analysis shows that the channel diameter has a highly significant impact on both K and K/ΔP, and the interaction between the channel diameter and the number of turning cycles also significantly influences these two response variables. The optimal parameter set for achieving the maximum K value (1 313 W/(m2·K)) was determined to be a channel diameter of 1.003 mm, a turning angle of 29.71°, and 9.935 turning cycles. Furthermore, the optimal combination for the comprehensive performance factor K/ΔP was found to be a channel diameter of 2.0 mm, a turning angle of 9.407°, and 6 turning cycles, yielding a K/ΔP value of 0.453 7 W/(m2·K·Pa) and a corresponding K value of 801.7 W/(m2·K). A comparative analysis reveals that the optimized PCHE volume is reduced by approximately one-tenth compared to conventional shell-and-tube heat exchangers.
This study confirms that variations in the channel diameter, turning angle, and number of turning cycles significantly affect the thermal performance of zigzag PCHEs. The response surface methodology proves effective in optimizing the channel structural parameters to enhance heat transfer performance. Moreover, PCHEs demonstrate remarkable compactness advantages in CO2 energy storage systems, making them well-suited for space-constrained operational environments. The findings provide reliable theoretical and data-driven support for the rational selection and engineering design of heat exchangers in related fields.
Ammonia-coal co-firing mode for power generation can significantly reduce the carbon emission level of the unit. But when the ammonia blending ratio is too high, the ammonia blending/pure ammonia burner is not properly arranged, and the ammonia-coal co-combustion effect is not good, the escaped ammonia will react with SO2/SO3 at low temperature, increasing the risk of corrosion and fouling on low temperature heating surfaces. To solve this problem, 168-hours continuous corrosion experiments of No.20 and ND steel specimens in an oxidizing atmosphere of NH3-SO2-O2-CO2-H2O(g)-N2 at 250 ℃ and 150 ℃ were carried out. The effects of temperature, NH3 volume fraction and fly ash coating on the corrosion rate of metal specimens were mainly investigated, and the corroded metal specimens and ash samples were analyzed in terms of micro-morphology and mineral phase. The experimental results showed that the average corrosion rate of ND steel specimens decreased by 58% when the volume fraction of ammonia was increased from 0.002 5% to 0.005 0%. The corrosion rate of No.20 steel coated with fly ash was significantly accelerated in the atmosphere of NH3 with volume fraction of 0.005%, and the average corrosion rate reached 0.003 6 mg/(cm2·h). Elevating temperature significantly accelerated the corrosion rate. ND steel coated with fly ash showed the fastest average corrosion rate at 250 ℃ (0.011 2 mg/(cm2·h)). At 250 ℃, CaSO3 was newly generated and it was detected in the ND steel-coated ash samples, which may have promoted adhesion among ash particles. After the corrosion of No.20 steel coated with fly ash at 150 ℃, the ash sample had a serious agglomeration effect, which is mainly due to the newly generated NH4HSO4 and (NH4)2SO3 promoting the agglomeration effect among ash particles. In the future, when a large proportion of ammonia is mixed with coal-fired units, especially when medium and high sulfur coal is used, special attention should be paid to the change of fly ash characteristics and the risk of fouling and corrosion on low temperature heating surfaces.
In-factory testing of chloride ions in urea for urea-to-ammonia hydrolysis systems in power plants is a crucial task, and how to quickly and accurately detect chloride ions content remains an urgent problem to be solved. This study has proposed a new method for determining the mass concentration of chlorides in urea using silver chloride spectrophotometry. This method is simple and fast, capable of detecting the chloride content in a set of urea samples in about 20 minutes, with a detection range of 0.07 mg/L to 2.00 mg/L and a detection limit of 0.02 mg/L. Eighteen repeated tests were conducted on a 10% urea solution with a chloride ion mass concentration of approximately 0.05 mg/L. The results indicated a relative standard deviation of 8.30%. The recovery rate of spiked tests in the 10% urea solution ranged from 86% to 110%. Both the accuracy and sensitivity of this method meet the quality requirements for urea used in the urea-to-ammonia hydrolysis systems in thermal power plants, making it a suitable method for determining chlorides in urea.
To solve the two core problems of solar-coal hybrid power generation, namely the high cost of solar collectors and the low solar conversion efficiency, a novel low-cost and efficient solar-coal hybrid power generation system was proposed.
In this new system, by using low-temperature evacuated tube solar energy to drive the waste heat recovery, the cost of solar collectors can be reduced significantly and solar amplified utilization is achieved. The performance of the new system was revealed by simulation, thermodynamic analysis, and economic analysis.
Based on a typical 600 MW unit, the new system exhibited a solar-to-electricity efficiency of 32.68% via the novel mode of evacuated tube solar-driven waste heat recovery. The cost of solar collecting devices in the proposed system was reduced to 34.9% of that in the conventional system. The cost of solar-generated electricity was kept at 0.440 yuan/(kW·h). [Conclusions] The thermal and economic performance of the proposed system was significantly improved compared with that of the conventional one, and the key problems in the field of solar-coal hybrid power generation have been solved.
To address the reduction in power generation efficiency caused by dust accumulation on PV modules, this study proposes a seasonally optimal cleaning strategy that overcomes the limitations of conventional fixed-interval and dynamic cleaning methods which often neglect seasonal variability.
Based on historical meteorological and PV generation data, time-varying predictive models of the performance ratio (PR) and dust accumulation are established for spring, autumn, and winter. An improved multi-objective particle swarm optimization (IMOPSO) algorithm is developed, incorporating a differential evolution mutation strategy and a fitness value caching mechanism to enhance optimization performance. Taking both power output and cleaning cost as objective functions, the seasonal cleaning intervals are optimized.
Using a PV power station in Changzhou, Jiangsu Province as a case study, the optimized cleaning intervals are determined to be 25 days in spring, 28 days in autumn, and 20 days in winter. Compared to the uncleaned condition, the optimized strategy leads to increases in power generation of 1.83%, 2.01%, and 3.52% for spring, autumn, and winter, respectively.
The IMOPSO algorithm boasts fast convergence speed and uniform solution set distribution. The proposed seasonal cleaning strategy fully accounts for the impact of seasons on dust accumulation, enabling it to increase power generation while controlling cleaning costs. This provides a scientific basis for the formulation of cleaning schemes for photovoltaic power stations.
To fully dig the enormous potential of carbide slag and corn cob in resource utilization, thus to meet the demands of colid waste recycling and low-carbon energy storage.
A novel composite phasechange thermal energy storage material was prepared using industrial solid waste carbide slag and agricultural solid waste carbonized corn fiber as the binary skeleton material, and with paraffin as the phase-change medium. The composites were synthesized via vacuum impregnation, and process parameters were optimized.
The results showed that the material exhibited optimal encapsulation performance at a carbide slag-to-carbonized corn fiber mass ratio of 5:5, maintaining structural stability after 600 thermal cycles. The optimal sample SC-5 achieved melting and solidification latent heats of 34.90 and 36.35 J/g, respectively, with a thermal conductivity of 0.484 W/(m·K), indicating good thermal stability and chemical compatibility. Microstructural analysis revealed that the skeleton materials formed a dense microporous structure, effectively mitigating paraffin leakage. Post-cycling material analysis indicated no new chemical bonds and maintained elemental homogeneity.
This work provides a novel pathway for synergistic valorization of industrial and agricultural solid wastes, demonstrating significant application potential in building energy conservation, industrial waste heat recovery, and thermal management of electronics.
Using energy analysis and exergy analysis methods, and considering the irreversible losses in the compression, expansion, and heat-exchange processes comprehensively, the performance indicators and irreversible loss distribution characteristics between a basic PTES (BC-PTES) system and an electric heater-integrated PTES (EH-PTES) system under defined operational conditions are compared, and the influence of key parameters on the EH-PTES system’s performance is investigated. The results indicate that both the BC-PTES and EH-PTES systems generate large exergy losses in the turbine during the discharge, with values of 456 kW and 455 kW respectively. The EH-PTES system demonstrates higher round-trip efficiency (41.50%) and energy storage density (54.1 kW·h/m³), with the exergy efficiency of the electric heater at 63%. Parameter analysis reveals that there exists an optimal discharge-phase compressor outlet pressure which can minimize the exergy loss and maximize system round-trip efficiency. For the EH-PTES system, at the optimal discharge pressure, the round-trip efficiency of the EH-PTES system initially decreases and then increases with the rising electric heater outlet temperature, and it increases with the compressor outlet temperature. For example, when the compressor outlet temperature is 550 ℃ and the electric heater outlet temperature increases from 600 ℃ to 1 000 ℃, the EH-PTES system round-trip efficiency decreases from 45.03% to 44.81% at first, and subsequently increases to 45.75%. When the electric heater outlet temperature is 850 ℃ and the compressor outlet temperature increases from 400 ℃ to 550 ℃, the system round-trip efficiency increases from 39.17% to 45.14%. Notably, the round-trip efficiency is less sensitive to the electric heater outlet temperature than to the compressor outlet temperature. By integrating electric heaters, the energy storage density can be substantially enhanced, reaching 113.9 kW·h/m³ at an electric heater outlet temperature of 1 000 ℃. These findings provide critical insights for optimizing the PTES system design.
A Carnot battery system based on coal-fired power units can efficiently absorb curtailed power of new energy while utilizing the existing infrastructure of coal-fired plants for energy release, thereby addressing the challenges posed by high-penetration renewable energy on the power supply-side flexibility. A novel supercritical carbon dioxide reverse Brayton-Rankine cycle Carnot battery system is proposed based on the concept of split-flow expansion, and a comprehensive investigation is conducted through thermodynamic modeling in EBSILON Professional, parameter sensitivity analysis, and multi-objective optimization using genetic algorithms. The results indicate that under design conditions, the turbine power output and waste heat recovery of the novel system are improved by 59.84% and 43.23%, respectively, compared to the reference system. The energy storage cycle achieves a coefficient of performance (COP) of 1.32 and a round-trip efficiency (RTE) of 57.68%, representing an increase of 0.10 in COP and 4.37 percentage points in RTE over the reference system. Both COP and RTE increase with higher pressure ratios, higher flow split ratios, and lower top-end temperature differences in recuperator 2. When the flow split ratio is 0.23, the pressure ratio is 3.09, and the top-end temperature difference in recuperator 2 is 12.60 ℃, the COP of the Carnot battery storage cycle reaches a maximum of 1.37, with a corresponding RTE of 59.87%. The study provides a technical reference for enhancing the operational flexibility of coal-fired power plants and optimizing renewable energy integration through advanced thermal storage technologies.
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