Abstract

Lithium-ion batteries serve as crucial energy storage carriers due to their numerous superior properties. However, metal impurities introduced during the manufacturing process can affect battery performance. The intrinsic impacts of these impurities have not yet been fully elucidated. In this study, pouch cells containing copper particle impurities are investigated. The results show that cells with impurities not only experienced micro-short circuits but also exhibited higher polarization compared to normal cells. Various material characterization techniques reveal that the increase in impedance is due to factors such as cracking of the anode graphite layer and localized lithium plating on the anode. Furthermore, the experiments reveal that the aluminum current collector in the short-circuit area dissolves and diffuses to the anode surface, forming deposits, while deposits also form around the impurity particles in the cathode. These phenomena can further degrade battery performance. The findings of this study enhance the understanding of the deep-seated effects of impurities in lithium-ion cells and provide theoretical insights for the manufacturing and detection methods of internal impurities in lithium-ion cells.

Abstract

The study of methane hydrate formation kinetics in various ionic solution systems helps to understand the hydrate formation characteristics in deep-sea cold seep environments, providing insights into methane conversion. The ionic composition and ratio in seawater play an important role in the nucleation and growth of methane hydrate. In this study, we investigated the formation behaviors of methane hydrate in varied ionic solutions and in-situ seawater. It was found that, compared with in pure water system, the inhibition of hydrate formation in the solutions was in the following order: NaCl ＞ seawater ＞ MgCl2 ＞ CaCl2 ＞ SrCl2. The experimental results of this study can provide a reference for further exploration of methane hydrate formation in cold seep environments, and can also contribute to an effective response to the challenge of climate change and the goal of carbon neutrality.

Abstract

Marine microorganisms play a vital role in the ocean’s cycling of organic matter and nutrients. Here, we conducted a 150-day simulation experiment to investigate cold seep sedimentary microbial diversity under different pressure conditions (0.1-14 MPa) and the roles of various influencing factors. The results showed that the level of pressure affected the reaction rates of metabolic processes, especially those involved in the carbon cycle. The microbial diversity tended to decrease and then increase with increasing pressure. An environmental pressure of 7 MPa was the dividing line between stochastic and deterministic processes. The microbial community diversity was primarily influenced by sulfate ion (SO₄²⁻), total organic carbon (TOC), and total inorganic carbon (TIC).

Abstract

The reformer is a key component in MRFC for on-site H2 production and operation of HT-PEMFC. In this study, a segmented reformer was designed using heat transfer structure optimization to control the temperature segmentation of the reaction zone, achieving high conversion rate and low CO outlet molar fraction. The multi-objective optimization of methanol conversion rate and CO output molar fraction was conducted to determine the optimal structures with the NSGA-II optimization algorithm. Under the optimal structure, the methanol conversion rate of the segmented reformer reaches 99.6%, with a CO outlet mole fraction of 1.3%. For the output power, the MRFC with the segmented reformer can generate output power of 302 W, which provides reference significance for the commercialization of MRFC.

Abstract

The recent transition in the power system brings challenges like load and demand imbalance, intermittent renewable energy recourses, and the risk of lumping load from power-to-X applications. The battery energy storage system (BESS) is a viable solution for short-term and long-term balancing. Combined with the upcoming major load type of the electrolyzer, we propose the lab-field multi-energy system platform for validating a demonstration of a virtual power plant for grid-connection synergies. Based on the field tests, we summarize the characteristics of the redox flow BESS, lithium-ion BESS, and electrolyzer. The response time of these components varies from one second for the redox flow BESS to a few hours for the electrolyzer. As these components have different response times, efficiency, and capacity, our work provides a reference for the hardware performance and lays the foundation for further implementation and optimization.

Abstract

The bio-natural gas (BNG) industry, which utilizes organic waste to produce biogas and purify it into BNG, has gained rapid development because it is in line with global carbon neutrality targets and sustainable development strategies. However, the difficulty in utilizing the carbon dioxide separated by the purification system restricts the green development of the BNG industry. Liquid CO2 is easier to store and transport compared to gaseous state, but liquefaction not only consumes power but also requires a high-grade cold source. In this research, based on a BNG station with a daily production of 5000 m3, a novel CO2 resource utilization system is proposed, which combines the waste heat recovery of CO2 compression heat with the utilization of cold energy from liquid natural gas (LNG) gasification to achieve energy saving and consumption reduction. The system consists of a two-stage CO2 cascade compression system, an organic Rankine cycle system and an LNG gasification system. A thermodynamic analysis was conducted on the system, and the results show that the ORC system effectively recover the waste heat of the CO2 cascade compression system, reducing the power output by 12.8%. When the evaporation and condensation temperatures of the ORC system are 368.15 K and 303.15 K, respectively, the cold energy recovery rate of LNG gasification reaches 62.6%. The pressurization ratio of the CO2 cascade compression system and the evaporation temperature of the ORC system have a large impact on the combined system, and the exergy analysis and parameter optimization design will be carried out subsequently. This study will provide theoretical guidance for CO2 resource utilization in BNG industry.

Abstract

As urbanization progresses, global building energy consumption is on the rise, emphasizing the need for a dependable energy consumption prediction model. This study presents a multi-stage machine learning approach comprising a clustering decomposition model (GMM), a prediction model (XGBoost), and an optimization model (PSO). Prior to clustering, the RF model evaluates the significance of various features influencing building energy consumption. GMM partitions the data into distinct clusters, while the PSO model fine-tunes the initial parameters of XGBoost. Validation is conducted using a dataset comprising 458,836 hourly records spanning three years from 20 office buildings in Shanghai, China. The average hourly energy consumption for all buildings is 79.2 kWh, but there is significant variation, with a standard deviation of 126.3 kWh. The prediction results indicate that the proposed model consistently achieves an R² exceeding 0.85 across diverse test sets, demonstrating robust accuracy and generalization capabilities. These findings offer valuable insights for future building design and energy management strategies.

Abstract

A virtual power plant (VPP) plays a key role in integrating renewable energy and responding grid frequency fluctuations caused by the variable output of renewable sources. However, correcting frequency deviations doesn’t represent maintain the power balance. VPPs must maintain stability through tertiary frequency regulation (TFR), often relying on power trading with the grid due to limited internal resources. To reduce this grid dependency, a coordinated control strategy is proposed to optimize the use of internal energy storage. It includes three methods: time-sharing to handle fluctuation timing uncertainty, demand analysis to address fluctuation power uncertainty, and resources selection to identify VPP resources for TFR participation. Simulations show that during the “longest duration of fluctuation”, the strategy effectively stabilized the VPP and reduced power trading, decreasing the grid power from 32.5 MW to 3.8 MW through coordinated control of plan adjustments, over-limit power regulation. In the “highest power deviation of fluctuation” coordinated control of plan adjustments and over-limit power regulation reduce power trading from 43 MW to 9.7 MW and energy traded from 215 MWh to 48.5 MWh – a 77.44% reduction.

Abstract

In the present era, electric vehicles are progressively gaining popularity on a global scale. The objective of using a battery thermal management system (BTMS) is to ensure that the power battery pack maintains a controlled temperature range during both charging and discharging processes. This paper aims to enhance the performance of the BTMS by incorporating topologically optimized fins into the composite phase-change material (PCM) and liquid cooling coupling BTMS. Specifically, paraffin with expanded graphite (EG) and foam aluminum nitride as composite phase-change materials were selected. Utilizing COMSOL Multiphysics software, topology optimization was employed to determine the material distribution within the design domain. Subsequently, a 3D model was constructed and the performances of three systems — without fins, with rectangular fins, and with topology-optimized fins — were compared. The results show that after 720 s of discharging at a 5C charge/discharge rate, the average temperature of the battery with the topology optimized fin system is 15.16 °C lower than that of the battery without fins and 1.32 °C lower than that of the battery with rectangular fins. This indicates that the system with topology optimized fins has better heat transfer efficiency

Abstract

The Building Integrated Photovoltaic Thermal (BIPVT) module is a composite module that combines a photovoltaic module and a solar thermal collector module and has the advantage of producing power and heat at the same time. BIPVT module is affected by electric generation performance by heat collection performance. It is important to know the correlation between changes in power generation performance according to temperature changes of the BIPVT module. This study conducted a comparative experiment on temperature and power characteristics between different types of BIPVT modules without a glass cover. Three BIPVT modules with different thermal collection methods were installed in the mock-up facility at a vertical angle of 90° vertically facing to the south. As the experimental result, the total efficiency of BIPVT module was highest in Case (1) at 34.8%, followed by Case (2) at 19.8%, Case (3) at 17.2%, and Reference at 10.9%.