Tailoring surface capacitance of Ti3C2Tx-PANI@CNTs nanoarchitecture for tunable energy storage and high-performance micro-supercapacitor

Transition metal carbide or nitride (MXenes), as a novel family of two-dimensional materials, exhibit huge potential for electrochemical energy storage thanks to their excellent electrical conductivity, fast ion diffusion rate, high electrochemical activity and good hydrophilicity. However, the electrochemical properties of MXenes tend to be deteriorated due to the self-restacking phenomenon. Herein, by self-assembly, a unique three-dimensional (3D) Ti₃C₂T_x-PANI@CNTs (TPCs) nanoarchitecture was constructed. Through optimizing structures, the surface capacitance of TPCs can be tailored to tune energy storage. The optimal specific capacitance up to 431.9 F/g was achieved under 1 A/g. Further, the TPCs nanoarchitectures were prepared into self-standing films with excellent mechanical properties and micro-supercapacitors (MSCs) in various shapes were manufactured based on the film. The MSCs demonstrate competitive energy storage capacities, obtaining an areal capacitance of 78.2 mF/cm² and energy density of up to 2.72 μWh/cm², still maintain excellent performance under harsh bending. The strategy for constructing 3D nanoarchitectures and further manufacturing MSCs can inspire the design of novel electrode materials and devices to advance the development in the field of energy storage.     

Electromagnetic transients in the control system of output parameters of a solar power plant in Tajikistan Central Asia region

At present, as the demand for electricity increases in all sectors, there is an urgent need to introduce alternative renewable energy sources into modern energy systems. Renewable energy sources, which consist of solar (photovoltaic, PV), wind and hydro power, are key alternative sources of “green energy’’ energies, but it can also be used to produce “green” hydrogen. Thanks to scientific and technological progress, the cost of photovoltaic solar radiation converters is constantly decreasing at a high rate, which makes it possible to build solar power plants of sufficiently large capacity. In the coming decades, solar energy will become an incentive for the economic development of countries that have the maximum “solar” resource. The Republic of Tajikistan is one of these countries with a high potential for solar energy.The article presents an analysis of the resources and potential of solar energy in the Republic of Tajikistan. The study of electromagnetic transients in networks with photovoltaic solar power plants is performed. The main equations, simulation model and calculations of transients are presented, taking into account changes in voltage on DC buses. An algorithm for controlling the system of automatic control of output parameters is proposed. The analysis of dynamic and static modes in parallel operation of a solar power plant with the grid is carried out. A block diagram and computer model is constructed in the MATLAB package together with Simulink and Power System Blockset.     

Hydrogen supply scenarios for a climate neutral energy system in Germany

A climate neutral energy system in Germany will most likely require green hydrogen. Two important factors, that determine whether the hydrogen will be imported or produced locally from renewable energy are still uncertain though - the import price for green hydrogen and the upper limit for photovoltaic installations. To investigate the impact of these two factors, the authors calculate cost optimized climate neutral energy systems while varying the import price from 1.25 €/kg to 5 €/kg with unlimited import volume and the photovoltaic limit from 300 GW to unlimited. In all scenarios, hydrogen plays a significant role. At a medium import price of 3.75 €/kg and photovoltaic limits of 300–900 GW the hydrogen supply is around 1200 to 1300 TWh with import shares varying from 60 to 85%. In most scenarios the electrolysis profile is highly correlated with the photovoltaic power, which leads to full load hours of 1870 h–2770 h.     

Combining a new baseboard radiator with a fan coil system for improving heating performance and reduce energy consumption

In the present work, the heating performance of a new system combined with a new modified baseboard radiator and fan coil is investigated. Using longitudinal fins with special geometry and also forced airflow at the end of the system causes that at the lower inlet water temperature compared with the conventional models, higher heat output rate be obtained. The heat output rate of the new modified system is obtained by experimental metrology based on the European Standard No. EN-442. Temperature and velocity distribution in the room space is done by simulation of the modified system in the Flovent software. Computational fluid dynamics (CFD) results are validated against experimental results and there is a good agreement between them. Also, the energy consumption of the system during the winter season is calculated in TRANSYS software. Experimental results show that the heat output rate of a new modified heating system with inlet water temperature in the range of 45–55°C is on average 4.17 times higher compared with the conventional model. CFD simulation also showed that the combined system provides good thermal comfort conditions. Energy consumption of the new system reduced about 13% compared with conventional models.     

Effect of metal oxide nanofluids on the performance of passive solar still single slope for two different absorbent plates

This study aims to improve the performances of a solar still single slope using metal oxide nanofluid (Al₂O₃–water, Cu₂O–water, and TiO₂–water). The numerical study was carried out for the climatic conditions of Agadir, Morocco, with different concentrations of nanofluids inside a basin equipped with an absorber plate with two different absorptivities. The numerical study is based on thermal balance equations applied on different solar system components and solved using the Runge Kutta method. The numerical model is validated by comparing our results with the literature available data. A comparison study of the effect of these nanofluids on solar still productivity is done. The results show that the productivity of the solar still using nanoparticles Cu₂O, TiO₂, and Al₂O₃ are 7.38, 7.1, and 7.064 kg m⁻² day⁻¹, respectively. It is obtained that the maximum efficiency of the solar still is found to be 55.27% by using cuprous oxide nanoparticles. Furthermore, an enhancement in solar still productivity of 6.36%, 19.54%, and 33.25% is obtained by dispersing 1%, 3%, and 5% volume fraction of Cu₂O nanoparticles in pure water, respectively compared to the conventional solar. Moreover, the impact of the absorptivity of the absorber plate on the solar still effectiveness is investigated. Two types of coatings are considered to change the absorber plate absorptivity. The results indicate that the efficiencies of the solar system are 58.81% and 51.77% using an absorber plate with 0.95 and 0.85 of absorptivity, respectively.     

Facile self-assembly approach to construct a novel MXene-decorated nano-sized phase change material emulsion for thermal energy storage

In recent years, phase change material emulsions (PCMEs) with enhanced energy storage capacities and good flow characteristics have drawn significant attention. However, due to the thermodynamically unstable nature and tiny particle confinement, the nanomaterial modification strategies at PCM/water interface to improve stabilities and reduce supercooling of nano-sized PCMEs (NPCMEs) are very limited and challenging. Herein, we report a facile strategy for constructing MXene-decorated NPCME with good stability, little supercooling, and high thermal conductivity by self-assembly of MXene nanosheets at PCM/water interface. The concentrations of MXene have great influences on the average droplet diameters, stabilities, and thermophysical properties of the NPCMEs. The results show that the PCMs have been well dispersed into the water in the form of quasi-spherical droplets, with average droplet diameters of 242–805 nm. The thermal conductivity of 10 wt% n-tetradecane/water NPCME containing 9 mg ml^-1 MXene is 0.693 W m^-1·K^-1, achieving an enhancement by 15.5%, as compared to that of water. Besides, the MXene-decorated paraffin/water NPCMEs exhibit little supercooling and enhanced heat storage capacities. More importantly, this facile self-assembly strategy opens a new platform for preparing high-performance NPCMEs, which can be used as novel heat transfer fluids for thermal energy storage systems.     

Data requirements for improving the Quantitative Risk Assessment of liquid hydrogen storage systems

Quantitative Risk Assessment (QRA) supports the development of risk-informed safety codes and standards which are employed to enable the safe deployment of hydrogen technologies essential to decarbonize the transportation sector. System reliability data is a necessary input for rigorous QRA. The lack of reliability data for bulk liquid hydrogen (LH₂) storage systems located on site at fueling stations limits the use of QRAs. In turn, this hinders the ability to develop the necessary safety codes and standards that enable worldwide deployment of these stations. Through a QRA-based analysis of a LH₂ storage system, this work focuses on identifying relevant scenario and probability data currently available and ascertaining future data collection requirements regarding risks specific to liquid hydrogen releases. The work developed consists of the analysis of a general bulk LH₂ storage system design located at a hydrogen fueling station. Failure Mode and Effect Analysis (FMEA) and traditional QRA modeling tools such as Event Sequence Diagrams (ESD) and Fault Tree Analysis (FTA) are employed to identify, rank, and model risk scenarios related to the release of LH₂. Based on this analysis, scenario and reliability data needs to add LH₂-related components to QRA are identified with the purpose of improving the future safety and risk assessment of these systems.     

Li decorated heteroborospherene C4B32 as high capacity and reversible hydrogen storage media: A DFT study

In this work, adsorption of H₂ molecules on heteroborospherene C_2v C₄B₃₂ decorated by alkali atoms (Li) is studied by density functional theory calculations. The interaction between Li atoms and C₄B₃₂ is found to be strong, so that it prevents agglomeration of the former. An introduced hydrogen molecule tilts toward the Li atoms and is stably adsorbed on C₄B₃₂. It is obtained that Li₄C₄B₃₂ can store up to 12H₂ molecules with hydrogen uptake capacity of 5.425 wt% and average adsorption energy of ?0.240 eV per H₂. Dynamics simulation results show that 6H₂ molecules can be successfully released at 300 K. Obtained results demonstrate that Li decorated C₄B₃₂ is a promising material for reversible hydrogen storage.     

复杂环境下氧化铝储槽定向爆破拆除

在较为复杂的环境下,爆破拆除钢筋混凝土氧化铝储槽。该储槽自重大、呈圆形,内有4根立柱支撑下料漏斗。为使储槽顺利定向倒塌,通过爆破方案选择、参数确定,采取梯形切口和预处理以及安全防护和减振措施,使储槽爆破拆除获圆满成功。     

粉体含能材料生产与储运中的静电安全及防护

分析了静电产生的原因,阐述了粉体含能材料生产中的静电起电现象、静电的危害、静电安全性评估标准以及建立在此标准基础上的静电放电危险的评价办法,提出了粉体含能材料在生产、运输中所需要采取的静电防护措施。