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Abstract: Abstract Due to increasingly stringent fuel consumption and emission regulation, improving thermal efficiency and reducing particulate matter emissions are two main issues for next generation gasoline engine. Lean burn mode could greatly reduce pumping loss and decrease the fuel consumption of gasoline engines, although the burning rate is decreased by higher diluted intake air. In this study, dual injection stratified combustion mode is used to accelerate the burning rate of lean burn by increasing the fuel concentration near the spark plug. The effects of engine control parameters such as the excess air coefficient (Lambda), direct injection (DI) ratio, spark interval with DI, and DI timing on combustion, fuel consumption, gaseous emissions, and particulate emissions of a dual injection gasoline engine are studied. It is shown that the lean burn limit can be extended to Lambda = 1.8 with a low compression ratio of 10, while the fuel consumption can be obviously improved at Lambda = 1.4. There exists a spark window for dual injection stratified lean burn mode, in which the spark timing has a weak effect on combustion. With optimization of the control parameters, the brake specific fuel consumption (BSFC) decreases 9.05% more than that of original stoichiometric combustion with DI as 2 bar brake mean effective pressure (BMEP) at a 2000 r/min engine speed. The NOx emissions before three-way catalyst (TWC) are 71.31% lower than that of the original engine while the particle number (PN) is 81.45% lower than the original engine. The dual injection stratified lean burn has a wide range of applications which can effectively reduce fuel consumption and particulate emissions. The BSFC reduction rate is higher than 5% and the PN reduction rate is more than 50% with the speed lower than 2400 r/min and the load lower than 5 bar. PubDate: 2022-12-31 DOI: 10.1007/s11708-021-0812-6
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Abstract: Abstract In this paper, a novel liquid metal-based minichannel heat dissipation method was developed for cooling electric devices with high heat flux. A high-performance electromagnetic induction pump driven by rotating permanent magnets is designed to achieve a pressure head of 160 kPa and a flow rate of 3.24 L/min, which could enable the liquid metal to remove the waste heat quickly. The liquid metal-based minichannel thermal management system was established and tested experimentally to investigate the pumping capacity and cooling performance. The results show that the liquid metal cooling system can dissipate heat flux up to 242 W/cm2 with keeping the temperature rise of the heat source below 50°C. It could remarkably enhance the cooling performance by increasing the rotating speed of permanent magnets. Moreover, thermal contact resistance has a critical importance for the heat dissipation capacity. The liquid metal thermal grease is introduced to efficiently reduce the thermal contact resistance (a decrease of about 7.77 × 10−3 °C/W). This paper provides a powerful cooling strategy for thermal management of electric devices with large heat power and high heat flux. PubDate: 2022-04-25
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Abstract: Abstract CO2 in natural gas (NG) is prone to condense directly from gas to solid or solidify from liquid to solid at low temperatures due to its high triple point and boiling temperature, which can cause a block of equipment. Meanwhile, CO2 will also affect the calorific value of NG. Based on the above reasons, CO2 must be removed during the NG liquefaction process. Compared with conventional methods, cryogenic technologies for CO2 removal from NG have attracted wide attention due to their non-polluting and low-cost advantages. Its integration with NG liquefaction can make rational use of the cold energy and realize the purification of NG and the production of by-product liquid CO2. In this paper, the phase behavior of the CH4-CO2 binary mixture is summarized, which provides a basis for the process design of cryogenic CO2 removal from NG. Then, the detailed techniques of design and optimization for cryogenic CO2 removal in recent years are summarized, including the gas-liquid phase change technique and the gas-solid phase change technique. Finally, several improvements for further development of the cryogenic CO2 removal process are proposed. The removal process in combination with the phase change and the traditional techniques with renewable energy will be the broad prospect for future development. PubDate: 2022-03-25
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Abstract: Abstract Co-gasification of industrial sludge (IS) and coal was an effective approach to achieve harmless and sustainable utilization of IS. The long-term and stable operation of a co-gasification largely depends on fluidity of coal-ash slag. Herein, the effects of IS addition on the crystallization and viscosity of Shuangmazao (SMZ) coal were investigated by means of high temperature stage coupled with an optical microscope (HTSOM), a scanning electron microscopy coupled with an energy dispersive X-ray spectrometry (SEM-EDS), X-ray diffraction (XRD), a Fourier transform infrared spectrometer (FTIR), and FactSage software. The results showed that when the proportion of IS was less than 60%, with the addition of IS, the slag existed in an amorphous form. This was due to the high content of SiO2 and Al2O3 in SMZ ash and blended ash, which had a high glass-forming ability (GFA). The slag formed at a high temperature had a higher polymerization degree and viscosity, which led to a decrease in the migration ability between ions, and ultimately made the slag difficult to crystallize during the cooling. When the proportion of IS was higher than 60%, the addition of IS increased the CaO and FeO content in the system. As network modifiers, CaO and FeO could provide O2− at a high temperature, which reacted with silicate network structure and continuously destroyed the complexity of network structure, thus reducing the polymerization degree and viscosity of slag. At this time, the migration ability between ions was enhanced, and needle-shaped/rod-shaped crystals were precipitated during the cooling process. Finally, the viscosity calculated by simulation and Einstein-Roscoe empirical formula demonstrated that the addition of IS could significantly improve the fluidity of coal ash and meet the requirements of the liquid slag-tapping gasifier. The purpose of this work was to provide theoretical support for slag flow mechanisms during the gasifier slagging-tapping process and the resource treatment of industrial solid waste. PubDate: 2022-03-20
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Abstract: Abstract Metal, as the indispensable material, is functioning the society from technology to the environment. Niobium (Nb) is considered a unique earth metal as it is related to many emerging technologies. The increasing economic growth exerts an increasing pressure on supply, which leads to its significance in the economic sector. However, few papers have addressed Nb sustainability, which forms the scope of this paper in order to start the process of Nb market forecasting based on some previous data and some assumptions. Therefore, this paper will discuss different thoughts in material substitution and the substance flow of Nb throughout a static flow using Nb global data to have a better understanding of the process of Nb from production to end of life. This shall lead to the identification of the market needs to determine its growth which is around 2.5% to 3.0%. Moreover, due to China’s huge Nb consumption which comes from the continuous development that is happening over the years, it will also briefly mention the Nb situation as well as its growth which according to statistics will grow steadily till 2030 by a rate of 4.0% to 6.0%. The results show that there should be some enhancement to Nb recycling potentials out of steel scrap. In addition, there should be more involvement of Nb in different industries as this would lead to less-used materials which can be translated to less environmental impact. PubDate: 2022-03-20
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Abstract: Abstract China’s aluminum (Al) production has released a huge amount of greenhouse gas (GHG) emissions. As one of the biggest country of primary Al production, China must mitigate its overall GHG emission from its Al industry so that the national carbon neutrality target can be achieved. Under such a background, the study described in this paper conducts a dynamic material flow analysis to reveal the spatiotemporal evolution features of Al flows in China from 2000 to 2020. Decomposition analysis is also performed to uncover the driving factors of GHG emission generated from the Al industry. The major findings include the fact that China’s primary Al production center has transferred to the western region; the primary Al smelting and carbon anode consumption are the most carbonintensive processes in the Al life cycle; the accumulative GHG emission from electricity accounts for 78.14% of the total GHG emission generated from the Al industry; China’s current Al recycling ratio is low although the corresponding GHG emission can be reduced by 93.73% if all the primary Al can be replaced by secondary Al; and the total GHG emission can be reduced by 88.58% if major primary Al manufacturing firms are transferred from Inner Mongolia to Yunnan. Based upon these findings and considering regional disparity, several policy implications are proposed, including promotion of secondary Al production, support of clean electricity penetration, and relocation of the Al industry. PubDate: 2022-03-10
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Abstract: Abstract The structure of a power energy system is becoming more distributed than before. It becomes challenging to manage such a system in a centralized way, because a central authority may not exist or may not be trusted by all parties. Blockchain is a promising tool to address this challenge, by enabling trusted collaboration in the absence of a trusted central authority. Its use in the energy sector has been pioneered by several pilot projects. However, to date the energy sector has not seen large-scale deployment of blockchain, partly because the founders of those pilot projects, the public, and utilities have not reached consensus on the values and limitations of blockchain in energy. This perspective aims to bridge this gap. First, the philosophy and unique values of blockchain are discussed. Second, some promising blockchain-based applications in energy systems are presented. Third, some common misunderstandings of blockchain in energy are discussed. Last, some frequently-asked questions from utilities are discussed. Hopefully this perspective can help advance large-scale deployment of blockchain in energy systems. PubDate: 2022-03-10
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Abstract: Abstract Nonintrusive load monitoring (NILM) is crucial for extracting patterns of electricity consumption of household appliance that can guide users’ behavior in using electricity while their privacy is respected. This study proposes an online method based on the transient behavior of individual appliances as well as system steady-state characteristics to estimate the operating states of the appliances. It determines the number of states for each appliance using the density-based spatial clustering of applications with noise (DBSCAN) method and models the transition relationship among different states. The states of the working appliances are identified from aggregated power signals using the Kalman filtering method in the factorial hidden Markov model (FHMM). Thereafter, the identified states are confirmed by the verification of system states, which are the combination of the working states of individual appliances. The verification step involves comparing the total measured power consumption with the total estimated power consumption. The use of transient features can achieve fast state inference and it is suitable for online load disaggregation. The proposed method was tested on a high-resolution data set such as Labeled hIgh-Frequency daTaset for Electricity Disaggregation (LIFTED) and it outperformed other related methods in the literature. PubDate: 2022-03-10
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Abstract: Abstract Solar energy-driven photocatalytic water splitting has been investigated for decades to produce clean and renewable green hydrogen. In this paper, the cutting-edge research within the overall water splitting system is summarized from the one-step photocatalytic overall water splitting (POWS) system to the two-step system and the cocatalysts research in this field. In addition, the photocatalytic reaction engineering study is also reviewed which is crucial for future scale-up. This mini-review provides a picture of survey of recent progress of relevant overall water splitting system, with particular attention paid to material system and mechanistic breakthroughs, and highlights the challenge and opportunity of the current system. PubDate: 2022-03-10
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Abstract: Abstract As a form of hybrid multi-energy systems, the integrated energy system contains different forms of energy such as power, thermal, and gas which meet the load of various energy forms. Focusing mainly on model building and optimal operation of the integrated energy system, in this paper, the dist-flow method is applied to quickly calculate the power flow and the gas system model is built by the analogy of the power system model. In addition, the piecewise linearization method is applied to solve the quadratic Weymouth gas flow equation, and the alternating direction method of multipliers (ADMM) method is applied to narrow the optimal results of each subsystem at the coupling point. The entire system reaches its optimal operation through multiple iterations. The power-thermal-gas integrated energy system used in the case study includes an IEEE-33 bus power system, a Belgian 20 node natural gas system, and a six node thermal system. Simulation-based calculations and comparison of the results under different scenarios prove that the power-thermal-gas integrated energy system enhances the flexibility and stability of the system as well as reducing system operating costs to some extent. PubDate: 2022-02-28 DOI: 10.1007/s11708-022-0814-z
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Abstract: Abstract Recent years have witnessed a rapid development of deformable devices and epidermal electronics that are in urgent request for flexible batteries. The intrinsically soft and ductile conductive electrode materials can offer pivotal hints in extending the lifespan of devices under frequent deformation. Featuring inherent liquidity, metallicity, and biocompatibility, Ga-based room-temperature liquid metals (GBRTLMs) are potential candidates to fulfill the requirement of soft batteries. Herein, to illustrate the glamour of liquid components, high-temperature liquid metal batteries (HTLMBs) are briefly summarized from the aspects of principle, application, advantages, and drawbacks. Then, Ga-based liquid metals as main working electrodes in primary and secondary batteries are reviewed in terms of battery configurations, working mechanisms, and functions. Next, Ga-based liquid metals as auxiliary working electrodes in lithium and nonlithium batteries are also discussed, which work as functional self-healing additives to alleviate the degradation and enhance the durability and capacity of the battery system. After that, Ga-based liquid metals as interconnecting electrodes in multi-scenarios including photovoltaics solar cells, generators and supercapacitors (SCs) are interpreted, respectively. The summary and perspective of Ga-based liquid metals as diverse battery materials are also focused on. Finally, it was suggested that tremendous endeavors are yet to be made in exploring the innovative battery chemistry, inherent reaction mechanism, and multifunctional integration of Ga-based liquid metal battery systems in the coming future. PubDate: 2022-02-28 DOI: 10.1007/s11708-022-0815-y
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Abstract: Abstract Since the catalytic activity of present nickel-based synthetic selenide is still to be improved, MoSe2-Ni3Se2 was synthesized on nickel foam (NF) (MoSe2-Ni3Se2/NF) by introducing a molybdenum source. After the molybdenum source was introduced, the surface of the catalyst changed from a single-phase structure to a multiphase structure. The catalyst surface with enriched active sites and the synergistic effect of MoSe2 and Ni3Se2 together enhance the hydrogen evolution reactions (HER), the oxygen evolution reactions (OER), and electrocatalytic total water splitting activity of the catalyst. The overpotential of the MoSe2-Ni3Se2/NF electrocatalyst is only 259 mV and 395 mV at a current density of 100 mA/cm2 for HER and OER, respectively. MoSe2-Ni3Se2/NF with a two-electrode system attains a current density of 10 mA/cm2 at 1.60 V. In addition, the overpotential of HER and OER of MoSe2-Ni3Se2/NF within 80000 s and the decomposition voltage of electrocatalytic total water decomposition hardly changed, showing an extremely strong stability. The improvement of MoSe2-Ni3Se2/NF catalytic activity is attributed to the establishment of the multi-phase structure and the optimized inoculation of the multi-component and multi-interface. PubDate: 2022-02-25 DOI: 10.1007/s11708-022-0813-0
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Abstract: Abstract More flexibility is desirable with the proliferation of variable renewable resources for balancing supply and demand in power systems. Thermostatically controlled loads (TCLs) attract tremendous attentions because of their specific thermal inertia capability in demand response (DR) programs. To effectively manage numerous and distributed TCLs, intermediate coordinators, e.g., aggregators, as a bridge between end users and dispatch operators are required to model and control TCLs for serving the grid. Specifically, intermediate coordinators get the access to fundamental models and response modes of TCLs, make control strategies, and distribute control signals to TCLs according the requirements of dispatch operators. On the other hand, intermediate coordinators also provide dispatch models that characterize the external characteristics of TCLs to dispatch operators for scheduling different resources. In this paper, the bottom-up key technologies of TCLs in DR programs based on the current research have been reviewed and compared, including fundamental models, response modes, control strategies, dispatch models and dispatch strategies of TCLs, as well as challenges and opportunities in future work. PubDate: 2022-02-01
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Abstract: Abstract With the continuous development of the spot market, in the multi-stage power market environment with the day-ahead market and right market, the study associated with the portfolio of energy storage devices requires that attention should be paid to transmission congestion and power congestion. To maximize the profit of energy storage and avoid the imbalance of power supply and consumption and the risk of node price fluctuation caused by transmission congestion, this paper presents a portfolio strategy of energy storage devices with financial/physical contracts. First, the concepts of financial/physical transmission rights and financial/physical storage rights are proposed. Then, the portfolio models of financial contract and physical contract are established with the conditional value-at-risk to measure the risks. Finally, the portfolio models are verified through the test data of the Pennsylvania-New Jersey-Maryland (PJM) electric power spot market, and the comparison between the risk aversion of portfolios based on financial/physical contract with the portfolio of the market without rights. The simulation results show that the portfolio models proposed in this paper can effectively avoid the risk of market price fluctuations. PubDate: 2022-02-01
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Abstract: Abstract This paper proposes a data-driven topology identification method for distribution systems with distributed energy resources (DERs). First, a neural network is trained to depict the relationship between nodal power injections and voltage magnitude measurements, and then it is used to generate synthetic measurements under independent nodal power injections, thus eliminating the influence of correlated nodal power injections on topology identification. Second, a maximal information coefficient-based maximum spanning tree algorithm is developed to obtain the network topology by evaluating the dependence among the synthetic measurements. The proposed method is tested on different distribution networks and the simulation results are compared with those of other methods to validate the effectiveness of the proposed method. PubDate: 2022-02-01
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Abstract: Abstract This paper attempts to resolve the reported contradiction in the literature about the characteristics of high-performance/cost-effective fenestration of residential buildings, particularly in hot climates. The considered issues are the window glazing property (ten commercial glazing types), facade orientation (four main orientations), window-to-wall ratio (WWR) (0.2–0.8), and solar shading overhangs and side-fins (nine shading conditions). The results of the simulated runs reveal that the glazing quality has a superior effect over the other fenestration parameters and controls their effect on the energy consumption of residential buildings. Thus, using low-performance windows on buildings yields larger effects of WWR, facade orientation, and solar shading than high-performance windows. As the WWR increases from 0.2 to 0.8, the building energy consumption using the low-performance window increases 6.46 times than that using the highperformance window. The best facade orientation is changed from north to south according to the glazing properties. In addition, the solar shading need is correlated as a function of a window-glazing property and WWR. The cost analysis shows that the high-performance windows without solar shading are cost-effective as they have the largest net present cost compared to low-performance windows with or without solar shading. Accordingly, replacing low-performance windows with high-performance ones, in an existing residential building, saves about 12.7 MWh of electricity and 11.05 tons of CO2 annually. PubDate: 2022-01-10 DOI: 10.1007/s11708-021-0799-z
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Abstract: Abstract Fuel starvation can occur and cause damage to the cell when proton exchange membrane fuel cells operate under complex working conditions. In this case, carbon corrosion occurs. Oxygen evolution reaction (OER) catalysts can alleviate carbon corrosion by introducing water electrolysis at a lower potential at the anode in fuel shortage. The mixture of hydrogen oxidation reaction (HOR) and unsupported OER catalyst not only reduces the electrolysis efficiency, but also influences the initial performance of the fuel cell. Herein, Ti4O7 supported IrOx is synthesized by utilizing the surfactant-assistant method and serves as reversal tolerant components in the anode. When the cell reverse time is less than 100 min, the cell voltage of the MEA added with IrOx/Ti4O7 has almost no attenuation. Besides, the MEA has a longer reversal time (530 min) than IrOx (75 min), showing an excellent reversal tolerance. The results of electron microscopy spectroscopy show that IrOx particles have a good dispersity on the surface of Ti4O7 and IrOx/Ti4O7 particles are uniformly dispersed on the anode catalytic layer. After the stability test, the Ti4O7 support has little decay, demonstrating a high electrochemical stability. IrOx/Ti4O7 with a high dispersity has a great potential to the application on the reversal tolerance anode of the fuel cell. PubDate: 2022-01-10 DOI: 10.1007/s11708-021-0811-7
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Abstract: Abstract Smart buildings have been proven to be a kind of flexible demand response resources in the power system. To maximize the utilization of the demand response resources, such as the heating, ventilating and air-conditioning (HVAC), the energy storage systems (ESSs), the plug-in electric vehicles (PEVs), and the photovoltaic systems (PVs), their controlling, operation and information communication technologies have been widely studied. Involving human behaviors and cyber space, a traditional power system evolves into a cyber-physical-social system (CPSS). Lots of new operation frameworks, controlling methods and potential resources integration techniques will be introduced. Conversely, these new techniques urge the reforming requirement of the techniques on the modeling, structure, and integration techniques of smart buildings. In this paper, a brief comprehensive survey of the modeling, controlling, and operation of smart buildings is provided. Besides, a novel CPSS-based smart building operation structure is proposed, and the integration techniques for the group of smart buildings are discussed. Moreover, available business models for aggregating the smart buildings are discussed. Furthermore, the required advanced technologies for well-developed smart buildings are outlined. PubDate: 2022-01-01 DOI: 10.1007/s11708-021-0792-6
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