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When solving eddy-current problems containing topologically non-trivial conductors with formulations using the magnetic scalar potential in the insulators, cohomology generators are necessary to obtain a well-defined problem. The Dłotko–Specogna (DS) algorithm is a simple and efficient tool to compute the lazy generators of the first cohomology group of the insulator that can be used in such potential design. This paper introduces an upgrade in the DS algorithm that speeds up the execution for very complicated geometries. Moreover, this paper provides, for the first time, a detailed comparison of computational resources needed for the topological pre-processing by our toolbox and by the tool to compute a standard cohomology basis available in the mesh generator GMSH. In addition, we make our implementation of DS algorithm available for download on request for non-profit use as a Topoprocessor package. [ABSTRACT FROM AUTHOR]

The increasing prevalence of technologies such as advanced metering and controls and continuously variable power electronic devices are enabling a radical shift in the way frequency regulation is performed in the bulk power system. This is a welcome development in light of the increase of unpredictable and variable generation. The idea of active participation of loads in frequency markets is not new, but the rapidly changing landscape of the power grid requires new techniques for successful integration of new types of resources; this paper works towards that end. Previously, it has been shown that residential HVAC systems can be aggregated and used to provide frequency regulation by utilizing their thermal energy capacity and flexibility of energy consumption. The virtual battery model—a first-order linear dynamical model—was analytically shown to be an accurate and simple model to capture the flexibility of residential HVAC systems. This paper presents a technique for creating the same battery-type models for many other types of systems, which can be much more complex. Our technique is based on stress testing detailed software models of physical systems. A realistic case study involving the terminal building of a small airport is presented as evidence of the effectiveness of the proposed techniques. [ABSTRACT FROM PUBLISHER]

Gravity currents contribute to the transport of heat and mass in atmospheric and aquatic environments. In aquatic systems subject to daily surface cooling, gravity currents propagate through turbulent convective surroundings. Yet, the effects of thermal convection on aquatic gravity currents remain to be quantified. This paper demonstrates how the interaction between penetrative convection and downslope gravity currents impacts the fluid dynamics and transport across littoral aquatic systems. We performed field experiments in a wind‐sheltered lake experiencing differential cooling to resolve the dynamics of thermally driven gravity currents in convective environments. Our in situ observations reveal that convective plumes penetrate gravity currents, generating large vertical fluctuations that foster the erosion of the stratified layer. This enhanced vertical mixing destroys the stratified downslope flow and limits the basin‐scale transport. Our results demonstrate that the interaction between penetrative convection and downslope gravity currents controls the littoral‐pelagic connectivity in aquatic ecosystems. Plain Language Summary: Horizontal differences in fluid density generate flows called gravity currents. These currents transport heat and mass across environmental systems. The dynamics of gravity current and the resulting transport are well understood when the surroundings are quiescent, which is rarely the case in nature. In aquatic systems, turbulent processes such as convection energize the ambient water. Cooling‐driven convection occurs when the surface of aquatic systems loses heat to the atmosphere, which generates sinking thermal plumes. In this paper, we used a lake experiencing differential cooling as an ideal field‐scale laboratory to investigate the effects of convection on the dynamics of gravity currents. Our in situ observations reveal that convective plumes distort the upper interface of gravity currents and limit the flow intensity. These results demonstrate that convection constrains the horizontal transport induced by gravity currents in natural systems. Key Points: Convective plumes penetrate downslope gravity currents and generate vertical interface fluctuationsVertical convective mixing erodes the stratified downslope flow and limits lateral transportThe time of maximal lateral transport is delayed to the relaxation phase once penetrative convection weakens [ABSTRACT FROM AUTHOR]

In this paper, based on the multi-scale multi-domain (MSMD) battery modeling approach, the NTGK model was used to model the 18650 cylindrical lithium-ion single battery on the electrochemical sub-scale. The model was successful, as it was able to fit the experimental voltage and temperature of the battery at different temperatures. Lithium-ion battery discharge capacity and energy output can be improved during cold starting by preheating and insulation, as demonstrated by a comparison of the impacts of heat transfer coefficient and preheating duration at −20 °C ambient temperature. For the traditional heating method, the heating model of heating film (HF) and liquid-cooled plate (LCP) is constructed in this paper, and the heating performance of both is compared by Fluent. Analysis of the energy balance of Li-ion battery at low temperatures has been presented, showing that Li-ion battery requires a suitable start-up temperature to maximize energy output. Taking care of the problem of excessive temperature difference inside the battery due to excessive heating power, we investigated the effects of axial thermal conductivity, heating power, and heating area on the heating uniformity of the battery in this paper. Finally, a multi-stage stepped power (MSP) heating method was proposed to improve the temperature control accuracy of HF. A level orthogonal test L16(43) without interaction was designed to determine the degree of influence of each parameter on the temperature control performance and the optimal level combination, revealing that the optimized maximum temperature and temperature control rate were reduced by 4.09% and 40.53%, respectively, when compared to direct heating. [ABSTRACT FROM AUTHOR]

As a kind of clean and renewable energy, shallow geothermal energy has the characteristics of wide distribution and huge reserves. The use of pile foundation heat exchange for building heating is a new technology to realize the effective utilization of geothermal energy. Improving the mechanical properties of the pile body material and improving the heat exchange efficiency of the pile foundation concrete will effectively promote the application of concrete in building structures. In this paper, the effect of steel fiber content on the thermal conductivity and mechanical strength of concrete is discussed by carrying out physical and mechanical properties test of concrete material of pile body. It is proposed to incorporate steel fibers into the concrete of the pile body to improve its thermal conductivity, thereby improving its heat transfer efficiency per unit time. At the same time, the role of steel fiber in enhancing heat transfer performance in pile material is analyzed from the microscopic mechanism, which provides theoretical support for the optimization process of concrete ratio of pile foundation in practical engineering. [ABSTRACT FROM AUTHOR]

This paper concerns a new method for projectile disposal by emptying the explosives in projectiles with electromagnetic heating. It explains the basic principles of the emptying technology via electromagnetic heating. A multiphysical analysis model coupled with an electromagnetic, thermal, fluid and phase transition model is established, and the explosive melting simulation is conducted based on this model. The dynamic phase transition process of the explosive from solid to liquid is simulated, and the electric field, magnetic field and thermal field distribution characteristics during the process are analyzed. Furthermore, the effect of excitation current characteristics on the phase transition of the explosive is given, which shows that the explosive melting process is controllable by setting the excitation current amplitude or frequency. This paper provides a new method for the disposal of end-of-life projectiles, which is more controllable, safe and environmentally friendly. [ABSTRACT FROM AUTHOR]

The energy efficiency of a system and the performance level of its equipment and installations are the two key elements based on which the investment decision in its modernization is made. They are also very important for setting up optimal operation strategies. The energy audit is a well-known and worldwide recognized tool for calculating energy performance indicators and developing improvement measures. This paper is a synthesis of the energy audit results performed for a district heating network that uses geothermal energy as its primary source of energy. The location of the heating system is inside a university campus. The first part explains the necessity of a comprehensive study on district heating networks and introduces the defining elements that characterize the analyzed equipment and installations. The complex energy balance methodology that has been developed and applied to this district heating system is presented in the second part of the paper. Next, the methodology for collecting the input data for the energy and mass balance is explained. In the final part, the numerical values of the performance indicators and the technical measures that must be applied to improve energy efficiency are shown, and conclusions are drawn. [ABSTRACT FROM AUTHOR]

Low-power-consumption optical devices are crucial for large-scale photonic integrated circuits (PICs). In this paper, a three-dimensional (3D) polymer variable optical attenuator (VOA) is proposed. For monolithic integration of silica and polymer-based planar lightwave circuits (PLCs), the vertical VOA is inserted between silica-based waveguides. Optical and thermal analyses are performed through the beam propagation method (BPM) and finite-element method (FEM), respectively. A compact size of 3092 μm × 4 μm × 7 μm is achieved with a vertical multimode interference (MMI) structure. The proposed VOA shows an insertion loss (IL) of 0.58 dB and an extinction ratio (ER) of 21.18 dB. Replacing the graphene heater with an aluminum (Al) electrode, the power consumption is decreased from 29.90 mW to 21.25 mW. The rise and fall time are improved to 353.85 μs and 192.87 μs, respectively. The compact and high-performance VOA shows great potential for a variety of applications, including optical communications, integrated optics, and optical interconnections. [ABSTRACT FROM AUTHOR]

The work is devoted to study of thermal efficiency of heating convectors with aluminum ribbing to ensure comfortable indoor conditions. The purpose of this paper is to evaluate theoretically and experimentally the thermal efficiency of convector-type heaters with aluminum ribbing, to implement numerical simulation and to obtain dependencies for determination of thermal characteristics of convector-type heaters with aluminum ribbing, ensuring of a proper both indoor climate in the premise and energy saving. A nomogram of interdependence between heat amount, heat carrying medium flow rate, the initial and final temperatures was created. Heat quantity increases with increasing heat carrying medium flow rate, the inlet temperature and decreases with increasing of the exit temperature. [ABSTRACT FROM AUTHOR]

Waste heat dissipated in the exhaust system of a combustion engine represents a major source of energy to be recovered and converted into useful work. The Waste Heat Recovery System (WHRS) based in an Organic Rankine Cycle (ORC) is an approach for recovering energy from heat sources, achieving a significant reduction in fuel consumption and, as a result, exhaust emissions. This paper studies pressure drop in an ORC shell-and-tubes boiler for a WHRS implementation experimentally and with computational simulations based on a 1-dimensional heat transfer model coupled with 3D calculations. An experimental database is developed, using ethanol in a pressure range of 10–15 absolute bar as working fluid, with mass fluxes inside the tubes in the range of 349.31 kg/s-m2 and 523.97 kg/s-m2, and inlet temperatures in the range of 60 °C and 80 °C. Thus, the friction factor of different regions of the boiler were estimated using both CFD simulations, experimental data, and bibliographic correlations. Simulations of operating points and the results of the experimental test bench showed good agreement in pressure drop results, with a mean absolute error of 15.47%, without a significant increment in the computational cost. [ABSTRACT FROM AUTHOR]

In this paper, the thermal management of missile-borne components in a flight state is studied. Avoiding excessive component temperatures under the high-temperature circumstances brought by aerodynamic heat is a requirement to guarantee the equipment's safe and reliable operation. In this work, we designed four finned shell constructions for a phase change module using the phase change temperature control method and then studied their effects on the module's ability to dissipate heat using an experimental approach. Three sizes of 30 mm, 40 mm, and 50 mm heating pads were used to replicate heat sources with various heat flux densities and heat dissipation regions, with reference to the heating characteristics of various chips. The results demonstrated that the square-shaped fin had the best heat dissipation effect after operating for 10 min under the power of 10 W and 20 W, while the strip-shaped fins exhibited the highest performance under the power of 30 W. The square-shaped fins had the best heat dissipation effect when reducing working time to 5 min. This paper proposes the optimal fin scheme under different power densities, as well as an enhanced heat dissipation idea for the melting process of the phase change materials based on the test results. [ABSTRACT FROM AUTHOR]

Heating, ventilation, and air-conditioning (HVAC) systems are large-scale distributed systems that can be subject to multiple faults affecting the electronics, sensors, and actuators, potentially causing high energy consumption, occupant discomfort, degraded indoor air quality and risk to critical infrastructure. Fault injection (FI) is an effective experimental method for the validation and dependability evaluation of such HVAC systems. Today's FI frameworks for HVAC systems are still based on a single fault hypothesis and do not provide insights into dependability in the case of multiple faults. Therefore, this paper presents modeling patterns of numerous faults in HVAC systems based on data from field failure rates and maintenance records. The extended FI framework supports the injection of multiple faults with exact control of the timing, locality, and values in fault-injection vectors. A multi-dimensional fault model is defined, including the probability of the occurrence of different sensor and actuator faults. Comprehensive experimental results provide insights into the system's behavior for concrete example scenarios using patterns of multiple faults. The experimental results serve as a quantitative evaluation of key performance indicators (KPI) such as energy efficiency, air quality, and thermal comfort. For example, combining a CO2 sensor fault with a heater actuator fault increased energy consumption by more than 70%. [ABSTRACT FROM AUTHOR]

Buildings are significant energy consumers and provide a notable potential to reduce primary energy consumption and increase energy efficiency. Cost-effectiveness of energy efficiency projects is of crucial importance for their implementation. Cost-optimality of different packages of energy retrofit measures is studied across the EU, but Serbia mostly lacks such information. This paper analyzes cost-optimal solutions for Serbian residential buildings connected to district heating systems, considering three different scenarios related to the economic input parameters. Additionally, it considers the potential for primary energy savings beyond cost-optimality and associated costs. The optimal solutions, that correspond to minimal global cost or minimal primary energy consumption, are determined as the results of the combinatorial optimization problems. These problems are solved using the genetic algorithm and local search. The results are compared against the ones obtained with the sensitivity analysis. The global cost can be reduced by 8-43% in the cases of cost-optimal solutions, simultaneously saving 30-76% of primary energy. The potential to save primary energy is higher - it exceeds 70% in all the analyzed cases, but also requires higher global cost, sometimes larger than in the absence of the retrofit. The paper also emphasizes high dependencies of the results on very uncertain economic inputs. [ABSTRACT FROM AUTHOR]

This paper considers the cost-driven optimal energy management strategy under a complex environment, multimicrogrids system. To provide the flexibility of load in depth, the heating, ventilating, and air conditioning (HVAC) load is investigated and explicitly formulated incorporated with indoor temperature dynamic function. The operation cost of wind generation includes the basic cost and additional cost to deal with the uncertainty of wind generation, which provides the tradeoff between optimality and possibility. Furthermore, the energy management problem of multimicrogrid is presented according to different characteristics of generation devices, storage devices, and load. A distributed neurodynamic algorithm is presented to solve the nonsmooth optimization of energy management of multimicrogrids system. By this method, the only information exchanged among microgrids is the intermediate variable when computing. The simulation results validate the effectiveness of the proposed cost-driven energy management strategy. [ABSTRACT FROM AUTHOR]

This paper assesses the performance of waste heat recovery from commercial kitchen wastewater in practice. A pilot study of heat recovery from the kitchen at Penrhyn Castle, a tourist attraction in North Wales (UK), is outlined. The pilot heat recovery site was designed and installed, comprising a heat exchanger, recirculation pumps, buffer tank and an extensive temperature/flow monitoring system for performance monitoring of the waste heat recovery system. Continuous monitoring was conducted for a period of 8 months, covering the 2022 tourist season. The recovered heat from the kitchen wastewater preheats the incoming cold freshwater supply and consequently reduces the amount of energy consumed for subsequent water heating. Retrofitting the pilot heat recovery system to the kitchen drains resulted in a heat saving of 240 kWh per month on average, a reduction of 928.8 kg CO2e per year, and a payback period for the investment costs of approximately two years, depending on the cost of energy supply. The presented results illustrate the potential of this form of renewable heat in reducing the carbon footprint of water heating activities in buildings and the hospitality sector. [ABSTRACT FROM AUTHOR]

Heating, Ventilating, and Air Conditioning (HVAC) systems often suffer from unscheduled maintenance or abnormal shutdown due to the fault of their interior sensor system. Traditional fault diagnosis methods for HVAC sensor systems primarily focus on sensor fault diagnosis and isolation, lacking fault accommodation. Therefore, to realize effective sensor fault detection, identification, and accommodation (SFDIA), a method for HVAC SFDIA based on the soft sensor is proposed. First, a diagnosis soft sensor with multi-variable input is constructed to estimate the output of the physical sensor being diagnosed. The residual between the estimated value of the diagnosis soft sensor and the measurement of the physical sensor is used as an indicator of the sensor's condition. If the residual exceeds the fault threshold, the sensor is diagnosed to be faulty. In order to maintain valid sensor output, an accommodation soft sensor is constructed using the historical normal value. The erroneous output of the faulty sensor is substituted by the estimated value from the accommodation soft sensor, thereby realizing sensor fault tolerance control. Experimental results demonstrate that the average false alarm rate for sensor fault diagnosis is 1.57% and the average fault diagnosis rate is 96.51%. The predictive mean absolute error (MAE) and root-mean-square error (RMSE) of the recovered soft sensors are 0.0525 and 0.0738, respectively. Thus, the soft sensors developed in this paper exhibit satisfying ability in HVAC SFDIA. [ABSTRACT FROM AUTHOR]

This paper utilizes a life cycle assessment (LCA) to evaluate three heating systems' energy resources and environmental impacts. The first system uses an electric heat pump that exclusively relies on geothermal energy. The second system operates on a gas boiler system that utilizes non-renewable electricity and natural gas. Lastly, the third system incorporates an absorption heat pump utilizing geothermal energy and natural gas. In the first step, cradle-to-gate assessments were prepared for the renewable, conventional, and mixed systems. The second step involved comparing the system scenarios based on their loads and energy resources. Primary energy, material resources, emissions, and impact categories were normalized and weighted using the CML, ReCiPe, and EF 3.0 methods. Finally, models for environmental reliability and complex decision support were developed. The novelty of this research lies in analyzing the ecological burden and energy usage of a mixed energy system that incorporates both renewable and non-renewable energy sources. The results show that the gas boiler system has a higher load, primarily due to the depletion of abiotic fossil fuels. However, the acidification is higher when an electric heat pump is used. The absorption heat pump system falls between the renewable and conventional systems in terms of both fossil depletion and acidification. [ABSTRACT FROM AUTHOR]

Predictive control has great potential in the home energy management domain. However, such controls need reliable predictions of the system dynamics as well as energy consumption and generation, and the actual implementation in the real system is associated with many challenges. This paper presents the implementation of predictive controls for a heat pump with thermal storage in a real single-family house with a photovoltaic rooftop system. The predictive controls make use of a novel cloud camera-based short-term solar energy prediction and an intraday prediction system that includes additional data sources. In addition, machine learning methods were used to model the dynamics of the heating system and predict loads using extensive measured data. The results of the real and simulated operation will be presented. [ABSTRACT FROM AUTHOR]

Induction heating offers numerous advantages over conventional methods for heating high-pressure fluids in hydraulic testing applications. It simplifies complex processes, mitigates the risks associated with high-pressure environments, and enhances overall safety. The design of an efficient induction heating system requires a clear understanding of its key components, including the resonant tank circuit, impedance matching and isolation stage, high-frequency inverter, driver circuitry, and controller. The configuration of the resonant circuit plays a crucial role in device ratings and control methods. To meet the demanding requirements of switching devices like IGBTs, the driver circuit must ensure high immunity to interferences and failure. Effective system design allows the heating circuit to operate close to resonant switching, minimizing switching losses and cooling requirements. This paper presents the design and development of a 4-kW induction heater specifically tailored for inline heating of aviation fuel under high pressure. The system aims to achieve a precise temperature profile for testing line-replaceable units (LRUs) used in aircraft. The design methodology encompasses the selection of the resonant tank circuit configuration, impedance matching and isolation stage, high-frequency inverter, driver circuitry, and control strategies. Through extensive simulations in LTspice and experimental measurements, power losses in different components of the power conversion circuits are assessed, and overall system efficiency is evaluated. The results demonstrate the proposed induction heating system's remarkable energy efficiency, reduced switching losses, and improved reliability. Furthermore, a comprehensive comparison with existing designs and industry norms is presented, highlighting the distinct advantages of the proposed system in terms of cost-effectiveness, energy efficiency, material utilization, and processing time. This research contributes valuable insights into the design and optimization of induction heating systems for high-pressure fluid heating applications, providing a practical and efficient solution for the aviation industry. [ABSTRACT FROM AUTHOR]

Coordinated fault recovery is essential for the resilience enhancement of integrated electric and heating systems (IEHS) following natural catastrophes as the linkage of the power distribution system (PDS) and district heating system becomes tighter. DHS reconfiguration is a viable method for service restoration because it could adjust the energy between energy sources and achieve uninterrupted energy supplies. In this paper, a collaborative service restoration model considering DHS reconfiguration is proposed to achieve better recovery after natural disasters. DHS reconfiguration could guarantee interrupted power supply in non-fault regions by shifting electric loads between power sources and accomplish optimal service restoration by adjusting the power output of combined heat and power units. Numerous case studies are undertaken to demonstrate the performance of coordinated reconfiguration on resilience enhancement and to confirm the efficacy of the proposed paradigm. [ABSTRACT FROM AUTHOR]

This research paper examined the operational performance and greenhouse gas (GHG) emissions of an existing gas treatment plant. Extensive data collection and analysis were undertaken to assess energy consumption and emissions and identify major emitter units. A GHG emission inventory was developed, and a benchmarking analysis was conducted. The gap analysis revealed excessive emissions, leading to the identification of potential GHG abatement alternatives for the turbo compressor and stabilizer heater. Technical feasibility assessments and economic evaluations were performed for the implementation of waste heat recovery systems, specifically an absorption chiller and a hot oil-driven re-boiler. The results demonstrated significant energy savings, emission reduction, and positive financial returns. The economic evaluation of the abatement opportunities revealed an estimated annual savings of $229,287 US with a simple payback period (SPBP) of 2.96 years and an internal rate of return (IRR) of 32%/year for the absorption chiller. The re-boiler heat system showed an estimated annual savings of $209,456 US with an SPBP of 5.14 years and an IRR of 14%/year. The total investment for both opportunities amounted to $1,755,773 US, with a total annual savings of $438,743 US. The combined SPBP for the opportunities was 4 years, with an IRR of 21%/year. Sensitivity analyses demonstrated the absorption chiller's financial viability, while the hot oil-driven re-boiler opportunity proved more sensitive to variations in investment costs and savings. Therefore, it is recommended to implement both opportunities together. [ABSTRACT FROM AUTHOR]

In this paper, we consider the exponential stabilization for a series system of N heat equations, where one boundary control is only applied to the leading (first) heat equation, and the boundary temperature of the previous heat is fed into the boundary heat flux of the next one. With N invertible transformations, we present a boundary feedback control so that the closed-loop system is equivalent to an exponentially stable target system. Some numerical simulation results are presented to validate the theoretical conclusions. [ABSTRACT FROM AUTHOR]

Advance in renewable penetration has promoted the interaction between the AC and DC power system and multi-energy sources. However, the disparate nature of different energy utilization technologies presents strong challenges for the economic dispatch of such a complex system. This paper proposes a comprehensive characterization of the AC/DC power system considering multi-energy and renewable integration. Detailed models are elaborated for the AC/DC power grid, the district heating system (DHS), coupling units, and renewables to describe their inner interactions accurately. On this basis, an economic dispatch method is developed to minimize the operation cost and renewable's abandonment. Simulations indicate that the interaction between the AC/DC power systems and multi-energy sources can enhance voltage levels and improve operational economy. [ABSTRACT FROM AUTHOR]

The increasing penetration of renewable energy, particularly wind power, and the integration of different energy systems have become two major trends in the development of energy systems. In this context, this paper proposes a robust interval optimization method for combined heat and power dispatch (CHPD) to address the challenges associated with wind power accommodation. To enhance the flexibility of a power system and support the integration of wind power, flexibility resources from a district heating system are introduced in the economic dispatch. To ensure the safety and reliability of the CHPD results, a robust interval optimization method is employed. By considering a range of possible wind power outputs, the robust interval optimization method provides a robust and reliable dispatch plan that can accommodate uncertainties and fluctuations in wind power generation. To verify the effectiveness of the proposed model and method, case studies were conducted on a 6-bus electrical power system connected with a 6-node district heating system. The results demonstrate that the proposed approach can effectively enhance the integration of wind power and improve the overall reliability and flexibility of the energy system. [ABSTRACT FROM AUTHOR]

This study investigates a two-temperature hygrothermoelastic model to describe the effects of coupled temperature and moisture in a non-simple nano-beam subjected to hygrothermal loading. This paper analyses the hygrothermal distribution of an Euler–Bernoulli beam with a rectangular cross-section beam. A closed-form solution for temperature, moisture, displacement and hygrothermal stresses is obtained using the decoupling and integral transform methods along the thickness direction. A numerical example with porous composite material in the picoseconds scale has been calculated to illustrate the effect of the ramping time parameter within the hygrothermal field. The relevance of the influence of various characteristics is examined. The appropriate discussions and conclusions are reached. [ABSTRACT FROM AUTHOR]

This research provides a comprehensive exploration of energy efficiency dynamics in non-residential public buildings such as schools, swimming pools, hospitals, and museums. Recognizing the distinct energy consumption patterns of each building type, the study accentuates the unique challenges they present, with a particular focus on the continuous and intensive energy demands of hospitals and the unparalleled energy needs of swimming pools. Through an extensive review of various case studies, the research unveils prevailing energy consumption trends, highlighting the role of metrics in assessing energy efficiency and the inherent challenges these metrics face in ensuring uniformity and direct comparability. A core element of this analysis emphasizes the dual nature of technical retrofitting, categorizing interventions into passive and active measures. The research delves into the sustainability imperatives of energy interventions, exploring the economic motivations underpinning retrofit decisions, and the intricate relationship between advanced technological solutions and the behavioral tendencies of building operators and users. Additionally, the study uncovers the influence of external determinants such as climatic factors and government policies in shaping energy consumption in public buildings. In synthesizing these findings, the paper offers insightful recommendations, emphasizing the need for an integrated approach that harmonizes technological innovations with informed operational habits, aiming to optimize energy efficiency in public non-residential buildings. [ABSTRACT FROM AUTHOR]

Heating furnaces fueled by fossil fuels are commonly utilized in oilfields to provide heat to the settling tank, which heats the layer of crude oil. However, this traditional heating method consumes a significant amount of oil and gas resources, resulting in low energy utilization and environmental pollution. As the water content of the extracted crude oil increases over time, the operating costs of the settling tanks also continue to increase. Therefore, it is crucial to develop and implement clean and efficient heating technologies to facilitate the efficient operation of settling tanks. This paper proposes a solar–gas combined heating technology for settling tanks. A simulation model for the solar–gas combined heating system for the settling tank is constructed, considering the overall perspective of the system. The simulation model analyzes the impact of the control strategy for the oil collection period of the settling tank on the system performance. This analysis covers various aspects including the heat collection of the solar collector, the heat supply of the gas boiler, and the heat storage and release of the phase-change heat storage tank. The results demonstrate that when the oil collection cycle is Scheme E (4:00–8:00), the collector achieves the highest annual cumulative heat collection, the gas boiler provides the lowest annual total heat supply, and the phase-change heat storage tank exhibits the highest heat storage and release efficiency. Over the course of the system's 15 year service life, the settling tank solar–gas combined heating system saves 727,988.69 MJ of energy annually, resulting in total energy-saving costs of CNY 397,007. The dynamic investment payback period is estimated at 9.14 years, and the system reduces CO2 emissions by 753,069.8 kg. [ABSTRACT FROM AUTHOR]

A person's body temperature is an important indicator of their health status. A deviation of that temperature by just 2 °C already has or can lead to serious consequences, such as fever or hypothermia. Hence, the development of a temperature-sensing and heatable yarn is an important step toward enabling and improving the monitoring and regulation of a person's body temperature. This technology offers benefits to several industries, such as health care and sports. This paper focuses on the characterization and development of a hybrid yarn, which can measure and visualize temperature changes through a thermoresistive and thermochromic effect. Moreover, the yarn is able to serve as a flexible heating element by connecting to a power source. The structure of the yarn is designed in three layers. Each layer and component ensures the functionality and flexibility of the yarn and additional compatibility with further processing steps. A flexible stainless steel core was used as the heat-sensitive and heat-conducting material. The layer of polyester wrapped around the stainless steel yarn improves the wearing comfort and serves as substrate material for the thermochromic coating. The resulting hybrid yarn has a reproducible sensory function and changes its resistance by 0.15 Ω between 20 and 60 °C for a length of 30 cm. In addition, the yarn has a uniform and reproducible heating power, so that temperature steps can be achieved at a defined length by selecting certain voltages. The thermochromic color change is clearly visible between 28 and 29 °C. Due to its textile structure, the hybrid sensory and actuating yarn can easily be incorporated into a woven fabric or into a textile by means of joining technology sewing. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the performance of induction motors subjected to single phasing on the primary side of a distribution transformer that feeds the motors. While single phasing caused by, for example, loss of fuse or bad contact is permanent in nature, that caused by recloser operation is momentary and is the focus of this paper. Several motors and transformer connections were used to investigate the effects of the momentary interruptions of a phase on the performance of the induction motors. The conditions under which the motors are able to ride through the single phasing are presented and discussed. [ABSTRACT FROM PUBLISHER]

Adding water to fuel droplets is known to lead to puffing and micro-explosion. Puffing and micro-explosion lead to a rapid increase in the liquid fuel surface area. This, in turn, leads to an increase in the fuel evaporation rate and the formation of a homogeneous fuel vapor/air mixture. The latter is important for improving the efficiency of combustion technologies, including those used in internal combustion engines. The effects produced by puffing and micro-explosion lead to a reduction in fuel consumption, improved fuel/air mixing, and a reduction in harmful emissions. The contributions of puffing and micro-explosion to fire extinguishing have also been discussed in many papers. In this paper, we review the state of the art in the investigation of composite droplet micro-explosion and discuss the sufficient conditions for the start of puffing/micro-explosion as well as child droplet characteristics. [ABSTRACT FROM AUTHOR]

Many European and some other developed countries have addressed the use of geothermal energy systems as a renewable source of energy worthy of investment and development. Geothermal energy is a non-intermittent and potentially inexhaustible source that can be used for energy saving and environmental energy production, as well as to provide heating and cooling to buildings, by increasing the energy efficiency of conventional systems. This editorial paper collects the most significant and recent studies, dealing with geothermal source exploitation, the possible role of geothermal systems in the building retrofit measures, the use of shallow geothermal sources, and specific aspects of systems that exploit geothermal energy. [ABSTRACT FROM AUTHOR]

Combined heat and power (CHP) plants are known as efficient technologies to reduce environmental emissions, balance energy costs, and increase total energy efficiency. To obtain a more efficient system, various optimization methods have been employed, based on numerical, experimental, parametric, and algorithmic optimization routes. Due to the significance of algorithmic optimization, as a systematic method for optimizing energy systems, this novel review paper is focused on the meta-heuristic optimization algorithms, implemented in CHP energy systems. By considering the applied objective functions, the main sections are divided into single-objective and multi-objective algorithms. In each case, the units' combination is briefly detailed, the objective functions are introduced, and analyses are conducted. The main aim of this paper is to gather a database for the optimization of CHPs, demonstrate the effect of the applied optimization methods on the objective functions, and finally, introduce the most efficient methods. The most significant feature of this paper is that it covers all types of CHP optimization issues including scheduling, sizing, and designing problems, finding the extent of each optimization issue in the relevant papers in the last decade. Based on the findings, in the single-objective problems the combined heat and power economic dispatch (CHPED) issue as a subcategory of the scheduling problems is introduced as the most paid topic; the designing issue is known as the lowest paid topic. In the multi-objective problems, working on various types of CHP optimization problems has been conducted with an almost similar share. The combined heat and power economic emission dispatch (CHPEED) problem with the most share, and the sizing issue with the lowest share. The CHP designing and sizing optimization issues could be introduced as topics to work on more in the future. Additionally, the numerical results of CHPED and CHPEED problems solved by various algorithms are presented and compared. In this regard, specified test systems are considered. [ABSTRACT FROM AUTHOR]

Against a background of the energy internet and low-carbon electricity, regional integrated energy system (RIES) has become a key way to achieve sustainable energy development, leading to reduced operating costs and system carbon emissions, and improved system operating efficiency. This paper puts forward a low-carbon economic dispatching optimization method for RIES with a heating network and power-to-gas (P2G). First, the heating network model and the mathematical model of P2G were constructed. Second, the carbon trading mechanism was introduced, the objective function being: to minimize the sum of the system operating cost and carbon trading cost; and ensure that the balance of cooling, heating, electric power, and the operating constraints—of RIES and the heating network—were comprehensively considered. Finally, the CPLEX optimization software simulation was used. The results show that the proposed method can take into account both low-carbon and economic factors, and can provide a reference for RIES low-carbon economic dispatch. [ABSTRACT FROM AUTHOR]

The main objective of this study was to evaluate the effect of transformer construction materials, such as kraft insulation paper, varnish, core steel and gasket materials (rubber), on the physicochemical properties of natural ester-based insulating oils (NEIs) and mineral insulating oil (MIO) under heating. We evaluated two NEIs, one formulated with soya oil (Envirotemp FR3) and other with corn oil (Biovolt A). The test specimens were placed in a 1-L jar with 800 mL of insulating oil and then the jar was placed in an oven at 100 °C for 716 h. The insulating fluids were analyzed before and after the heating tests by physicochemical analyses, such as kinematic viscosity, acid number (or neutralization number), dissipation factor and interfacial tension for MIO. Properties of the aged reference and the test specimen oils for a standard testing method for compatibility of construction materials with NEIs are proposed. The only parameter that showed variation after the NEI compatibility testing with different materials was the dissipation factor at 90 °C. The results show that besides compatibility and aging tests, mechanical tests for the gasket or seal materials should also be performed to conclude whether a material is suitable for construction of transformers insulated with NEIs. [ABSTRACT FROM AUTHOR]

In this paper, we generalize a fast Fourier transforms (FFTs) based preconditioner and propose a novel α -absolute value preconditioner for all-at-once systems from heat equations. Our preconditioner is symmetric positive definite and can also be computed efficiently using fast Fourier transforms or discrete sine transforms (DSTs). Furthermore, we prove that the corresponding preconditioned matrix has a unitary-plus-low-rank decomposition, and the eigenvalues of the preconditioned matrix are clustered at ±1, which leads to fast convergence rate of the preconditioned MINRES method. Finally, numerical examples on all-at-once systems from heat equations with different discretization scheme demonstrate the effectiveness of our new preconditioner. [ABSTRACT FROM AUTHOR]

At present, most of the existing research on low-speed permanent magnet motors (LSPMMs) focuses on the surface-mounted type. There are few other rotor structures, and there is no comprehensive comparison of several widely used rotor structures. A comprehensive comparison of three different rotor structures for low-speed mining motors is carried out, including electromagnetic and loss characteristics, permanent magnet consumption, temperature distribution, etc. Firstly, three rotor structures of a 500 kW, 60 rpm low-speed motor are introduced, and the initial design parameters are determined. Secondly, the influence of each rotor design parameter on the electromagnetic characteristics is analyzed. Next, the electromagnetic optimization of the three rotor structures is carried out, and the motor performance of the three rotor structure optimization schemes is compared, including electromagnetic performance, permanent magnet consumption, motor temperature distribution, etc. Finally, in order to verify the correctness of the theoretical analysis, a prototype is made and tested based on the above analysis. The results show that for the electromagnetic characteristics, when the motors with three different rotor structures meet the performance requirements, the no-load line back-EMF of the inset surface-mounted motor is the lowest, but the back-EMF harmonic content of the inset surface-mounted motor is the highest. The copper loss of the spoke-type motor is the smallest, the efficiency is the highest, and the power factor is the lowest. In addition, the surface-mounted motor has the least consumption of permanent magnets and is more economical. Regarding the temperature distribution, when the same heat dissipation system is used, the temperature of the spoke-type motor with minimum copper loss is the lowest. [ABSTRACT FROM AUTHOR]

Laser-assisted automated tape placement systems are currently the state of the art regarding thermoplastic tape placement. Flashlamp heating systems are rather new in this field of application and offer high energy density with low safety requirements and moderate costs compared to laser-assisted automated tape placement systems. In this study, the effect of processing parameters on interlaminar bonding of carbon fiber-reinforced polyamide 6 tapes is investigated using a flashlamp heating system. The temperature during placement is monitored using an infrared camera, and the bonding strength is characterized by a wedge peel test. The bonding quality of the tapes placed between 210 °C and 330 °C at a lay-up speed of 50 mm/s is investigated. Thermogravimetric analysis, differential scanning calorimetry, and micrographs are used to investigate the material properties and effects of the processing conditions on the thermophysical properties and geometric properties of the tape. No significant changes in the thermophysical or geometric properties were found. Moisture within the tapes and staining of the quartz guides of the flashlamp system have significant influence on the bonding strength. The highest wedge peel strength of dried tapes was found at around 330 °C. [ABSTRACT FROM AUTHOR]

In recent years, SiC single crystal growth technology has been developed toward larger size and thickness to reduce the cost of SiC-based power devices. Resistance heating has gradually become a hot spot for research because the crystals grown by the induction heating display the disadvantages of high stress and defect density. In this paper, the design of resistance heaters for SiC crystal growth was thoroughly investigated via numerical simulation. A simulation of the thermal field generated by different resistive heater arrangements was performed. The stress and dislocation distribution in crystals under different growth conditions were studied. Based on the comprehensive requirements of a small radial temperature gradient and a large growth rate, the arrangement and length of the resistance heater were proposed. This study would serve as a useful guidance for the study of SiC growth by resistive heating. [ABSTRACT FROM AUTHOR]

The paper presents the design of a two-stage subcritical compressor heat pump operating in an air-to-water system and running on environmentally friendly refrigerants. The pump is dedicated to buildings where there is a hightemperature central heating system and wall-mounted radiators are used as heat receivers. The first stage of the unit was supplied with R290 refrigerant and the second stage with R1234 ze(E) refrigerant. The nominal heating capacity of the unit is 10 kW for a lower source temperature in the range-20÷10 °C. The unit›s refrigeration system was designed and simulation tests were carried out to determine the unit›s operating parameters for the lower source temperature in the range -20÷10 °C, the condensation temperature of the stage I refrigerant for values: 20 °C, 25 °C, 30 °C and the condensation temperature of the stage II refrigerant in the range 30÷60 °C. The value of the coefficient of performance (COP) was determined in relation to the heating capacity generated in stages I and II to the electricity consumed, which value, depending on the operating parameters, ranges from 2.55 to 5.6. The value of the COP related to the heating capacity received from the stage II condenser to the total capacity consumed by the stage I and II compressor, depending on the operating parameters, ranges from 1.5 to 2.9. It was found that by using a stepless adjustment of the volumetric efficiency of the stage I and II compressor, it is possible to match the heating capacity of stage I to the cooling capacity of stage II and thus increase the COP value by 50%. [ABSTRACT FROM AUTHOR]