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The rapid development of advanced metering infrastructure provides a new data source—building electrical load profiles with high temporal resolution. Electric load profile characterization can generate useful information to enhance building energy modeling and provide metrics to represent patterns and variability of load profiles. Such characterizations can be used to identify changes to building electricity demand due to operations or faulty equipment and controls. In this study, we proposed a two-path approach to analyze high temporal resolution building electrical load profiles: (1) time-domain analysis and (2) frequency-domain analysis. The commonly adopted time-domain analysis can extract and quantify the distribution of key parameters characterizing load shape such as peak-base load ratio and morning rise time, while a frequency-domain analysis can identify major periodic fluctuations and quantify load variability. We implemented and evaluated both paths using whole-year 15-minute interval smart meter data of 188 commercial office building in Northern California. The results from these two paths are consistent with each other and complementary to represent full dynamics of load profiles. The time- and frequency-domain analyses can be used to enhance building energy modeling by: (1) providing more realistic assumptions about building operation schedules, and (2) validating the simulated electric load profiles using the developed variability metrics against the real building load data.

Abstract The prime purpose of this work is to prepare a novel kind of Pickering interfacial solid catalysts for biodiesel production to meet the requirements of highly efficiency and environmental benign. To achieve this goal, the core–shell P[xSPA-yDABCO]@SiO2@Fe3O4 composite materials with a shell of photo-responsive and base catalytic sites were manufactured by means of layer-by-layer fabrication method. The modified materials, entirely characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectra, X-ray powder diffraction (XRD) and magnetization versus magnetic (VSM) techniques, demonstrated sufficient catalytic active sites and photo-responsive sites. Among all the so-prepared catalysts, P[3SPA-2DABCO]@SiO2@Fe3O4 performs extremely well and can stabilize soybean oil-in-methanol Pickering emulsion for 24 h, achieving a biodiesel yield up to 98.2% at a catalyst dosage of 5 wt% after the reaction time of 5 h at 60 °C. Furthermore, the double responsive solid catalyst can be readily separated from the mixture of reaction by an external magnet and UV irradiation, and still presented superior catalytic activity after 6 cycles.

The electro-hydraulic servo pump control system (EHSPCS) is a volume control system that uses a permanent magnet synchronous motor (PMSM) with a fixed displacement pump to directly drive and control the hydraulic cylinder. The energy transmission law of the system is very complicated due to the transformation of electrical, mechanical and hydraulic energy as well as other energy fields, and qualitative analysis of the energy transfer efficiency is difficult. Energy transfer analysis of the EHSPCS under different working conditions and loads is proposed in this paper. First, the energy flow transfer mechanism was analyzed, and the mathematical and energy transfer models of the key components of the system were established to explore the energy characteristic state transition rule. Second, a power bond diagram model was built, its state equation and state matrix were deduced, and a system simulation model was built. Finally, combined with the EHSPCS experimental platform, simulation experiments were carried out on the dynamic position following and steady-state position holding conditions of the system, and the variation rules of the power of each energy characteristic state and the system energy transfer efficiency under different loads were obtained. The research results provide a foundation for the study of power matching and energy-saving mechanism of the EHSPCS.

AbstractRevolutionary changes in energy storage technology have put forward higher requirements on next‐generation anode materials for lithium‐ion battery. Recently, a new class of materials with complex stoichiometric ratios, high‐entropy oxide (HEO), has gradually emerging into sight and embracing the prosperity. The ideal elemental adjustability and attractive synergistic effect make HEO promising to break through the integrated performance bottleneck of conventional anodes and provide new impetus for the design and development of electrochemical energy storage materials. Here, the research progress of HEO anodes is comprehensively reviewed. The driving force behind phase stability, the role of individual cations, potential mechanisms for controlling properties, as well as state‐of‐the‐art synthetic strategies and modification approaches are critically evaluated. Finally, we envision the future prospects and related challenges in this field, which will bring some enlightening guidance and criteria for researchers to further unlock the mysteries of HEO anodes.image

In the water-rich karst regions, high water and mud outbursts are common geological disasters in tunnel construction. To ensure the safe and smooth construction of tunnel projects, it is necessary to consider anti-water pressure, water inrush prevention and geological disasters during the design of tunnels. Based on the Yongfutun Tunnel Project, this paper studies the application and effect of radial grouting and curtain grouting, which involves those in high-water-pressure tunnels under double-layer support conditions. To obtain the effects and parameters of radial grouting and curtain grouting, the influences of different grouting ranges on the tunnel’s surrounding rocks and supporting structures were analyzed and the finite difference method was adopted. The results show that the radial grouting of the surrounding rock can notably improve the initial support of the tunnel, but the impact is less obvious when the grouting range exceeds 4 m. The design of radial grouting is recommended to be 4.0 m to 4.5 m. Curtain grouting can effectively reduce the external water pressure of the tunnel lining. The external water pressure of the grouting area is 23% greater than that without curtain grouting. Curtain grouting can slow down the infiltration of external water pressure. This is beneficial to the stress of the tunnel lining structure, but the improvement in initial support force is slight. Moreover, curtain grouting improves the safety reserve of the secondary lining by strengthening the self-stability ability of the surrounding rock. Meanwhile, the double-layer primary support can effectively share the external water pressure and surrounding rock pressure. This study provides a certain reference for the lining design of high-water-pressure tunnels.

Abstract This paper presented a novel method of dissipating solar photovoltaic heat based on the technology of micro-heat-pipe array and the utilization of photovoltaic-cell waste heat. This novel technology solved the problems of low PV electrical efficiency and thermal failure caused by high cell temperature, greatly increased the comprehensive utilization efficiency of solar energy, and extended the service life of photovoltaic modules. One-year experiments were conducted to investigate the electrical and thermal performance of a forced-circulation, household-type photovoltaic/thermal system based on micro-heat-pipe array in Beijing, China. Test results showed that on the four typical days in different seasons, the average electrical efficiencies were 13.76%, 11.92%, 13.71%, and 14.65%; the average thermal efficiencies were 31.62%, 33.07%, 24.99%, and 17.24%; and the average total efficiencies were 45.38%, 44.99%, 38.70%, 31.89%, respectively. The system met the demand of power supply on sunny days and the demand of hot water between March and November, except in cloudy days. These experimental results can provide basis and reference for practical applications of the system.

Abstract In a passive nuclear plant, the main control room must provide self-support functions for 72 h after an accident occurs. In this isolation mode, the heat generated by indoor occupants and equipment should be removed by using concrete walls that are 610 mm thick, and the finned ceiling made of concrete should maintain thermal habitability. However, the finned ceiling design has not been studied in normal buildings, and the cooling storage effect of plate-shaped fins is usually ignored during the design phase. In this study, a novel parametric resistance–capacitance thermal network is proposed to simulate the thermal performance of different fin-plate layout forms in the case of an accident. An experiment was conducted on a 1200 mm × 1200 mm × 610 mm fin-concrete module for 72 h to validate the model under constant air temperature conditions. Based on the model, multi-objective optimization was conducted to obtain optimal solution sets by using a radial basis function approximation model. The results show that the optimal performance indicators can be classified into unsteady and quasi-steady states, in which the dominant factors for heat transfer include the heat transfer area and the thickness of the finned plate, respectively. Further, the optimal solution sets for different convection and heating conditions obtained through an optimization process are used to design a fin layout based on actual temperature control demands and cooling storage.

In grounding fault of DC system, overvoltage will appear on equipment nodes in converter station. Due to different operation mode and equipment type, it is very different from overvoltage in AC system. Based on Shanghaimiao–Linyi​ ±800kV Ultra High Voltage Direct Current (UHVDC) transmission project, this paper studies the converter station overvoltage characteristics under the conditions of DC pole line grounding, DC bus grounding and converter transformer valve side grounding fault, then analyzes the influence of smoothing reactor, filter capacitor and grounding pole line on overvoltage. In grounding fault at DC pole line near the converter station, the maximum overvoltage occurs on the inductance of DC filter, which is 592.75kV; In grounding fault at the top of the high voltage converter valve, the maximum overvoltage occurs on the neutral bus, which is 272.17kV. Increasing the inductance or capacitance of the smoothing reactor and filter capacitor, shortening the length of grounding electrode wire can significantly reduce the amplitude and steepness of overvoltage. The calculation results provide a reference for the internal overvoltage suppression of DC converter station with layered access at the inverter side.