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Energy saving has become a key concern of metro systems to reduce operating costs and meet the requirements of sustainable development. Energy-efficient timetabling, an effective way to reduce traction energy consumption, has gotten much attention in recent decades. However, limited research about energy-efficient timetabling simultaneously considered realistic speed profiles and the influence of train loads, which change greatly in different sections and significantly affect energy consumption. Therefore, this paper proposes an energy-efficient timetabling approach to improve regenerative energy utilization based on varying train loads and realistic speed profiles for bidirectional metro lines. First, based on the operational and safety constraints, this paper constructs an integer energy-efficient timetabling model where dwell times and nonuniform headways are taken as decision variables. Besides, the turnaround process is also considered to ensure rolling stock circulation efficiency. Sectional passenger volumes are employed to determine the varying train loads. Energy consumption is calculated based on realistic speed profiles. Owing to the complexity of the model, an improved adaptive large neighborhood search (ALNS) algorithm is designed to solve this model according to its characteristics. Finally, numerical examples are conducted based on the practical data from Shanghai Metro Line 17. The results indicate that the proposed approach effectively solves the energy-efficient timetabling problem with varying train loads and realistic speed profiles for bi-directional metro lines. The approach is suitable for off peak hours and can reduce energy consumption effectively, and the reduction is up to 11.9% for the presented cases. The improved ALNS algorithm can find good solutions within reasonable times in different cases. Moreover, compared with the widely used genetic algorithm in the literature, the improved ALNS algorithm is more efficient in solving the proposed energy-efficient timetabling problem in different cases. [ABSTRACT FROM AUTHOR]

This paper aims to study the influence of novel macro encapsulated phase change materials (PCMs) on the mechanical and thermal properties of concretes. Thermal energy storage aggregates (TESAs) were prepared using vacuum impregnation. The PCMs were a lauric-myristic acid (LA-MA) eutectic mixture and coconut oil, pure or mixed, and are impregnated in diatomite as a supporting material. Thermal energy storage concrete (TESC) was made by replacing gravel in ordinary concrete with TESAs. Thermal and mechanical properties of prepared TESC were studied using differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, compressive strength, and thermal performance analysis. The results showed that the melting temperature of coconut oil and the eutectic mixture of LA-MA were 25.2°C and 34.5°C, respectively. TESC with 80 wt.% of gravel replaced with TESA had a compressive strength of higher than 17 MPa, which indicates its usability as structural concrete. The results of thermal performance analysis also revealed that prepared TESC had the capability of storing thermal energy and can reduce energy consumption by damping temperature fluctuations caused by the outside environment. In this paper, a thermal energy storage concrete (TESC) was prepared by embedding phase change materials (PCMs) in diatomite used in TESC. Using this type of concrete in the building will reduce the energy consumption of the building and increase its thermal comfort. The produced concrete containing 80 wt.% of gravel replaced with diatomite saturated with PCM had a desirable 28-day cylindrical sample strength of 21 MPa. In the designed thermal test, the time required for this concrete to reach 40°C is almost twice that of concrete without PCM. The results show a reduction of the influence of outside temperature on the temperature inside the buildings made with this type of concrete. [ABSTRACT FROM AUTHOR]

An energy-saving control strategy for wheel loaders is proposed in this paper to address the issue of high energy consumption during their operation. The strategy is based on the intelligent identification of working stages, allowing for staged power matching and resulting in reduced energy consumption. Each work stage of the loader is identified by matching it to the main pump pressure waveform and actuator pilot pressure waveform. Using a sliding time window method, pressure waveforms from each working stage are subjected to feature extraction. A bidirectional long short-term memory neural network (BILSTM) algorithm is then used to establish an intelligent recognition model. Based on work stage identification, an energy-saving control strategy based on power matching is proposed for the shoveling stage of the loader, and the Grey Wolf optimization (GWO)-PID algorithm is utilized for control parameter tuning. Finally, the effectiveness of the energy-saving control strategy based on work stage identification is verified through experiments. The research results indicate that the BILSTM recognition model outperforms other models with a recognition accuracy of 96.1%. The optimal time window width is 0.6 s, and the proposed energy-saving control strategy achieves a fuel-saving rate of 6.81%. This method provides feasibility for reducing energy consumption in construction machinery and achieving energy-saving and carbon-reduction goals. [ABSTRACT FROM AUTHOR]

The global rise in urban energy demand poses severe environmental and economic health challenges. We need adaptive policies in urban planning to reduce the need for urban energy. This has become a prominent agenda in urban planning, encompassing social (education and innovation in consumption), economic (real pricing), and physical (urban morphology) aspects. This research aims to investigate the influential role of urban form, particularly the physical environment, on energy performance. The methodological approach is centered on conducting analytical-comparative research to examine how urban form influences theoretical energy requirements. Yazd City is selected as a case study because of its distinctive features and traditional approaches to urban sustainability, which have been largely overlooked in previous energy consumption investigations. In a broader comparative context, five tissue types (morphological units) have been selected from Rome, Barcelona, Madrid, and Venice and used as the analytical basis of the study. The research categorizes urban forms into three levels: macro (fabric), medium (block), and micro (building patterns). Heating, cooling, and total energy consumption were computed at each level. The findings indicate that, at the macroscale, the Barcelona fabric offers the highest potential for adaptation in the hot, dry climate of Yazd City. Moreover, the paper analyzes the most recurring morphological indices in the tissues and proposes guidelines for new developments tailored to Yazd City's unique climatic conditions. By focusing on urban form's impact on energy performance, this research contributes to the broader understanding of sustainable urban planning. It offers valuable insights for energy-sensitive urban development in other contexts facing similar climate challenges. [ABSTRACT FROM AUTHOR]

In order to further study the possibility and potentiality of hybrid electric propulsion systems applied to helicopters, this paper aims at designing and analyzing power-split hybrid electric propulsion systems (PS-HEPSs) for the AC311 helicopter equipped with a diesel engine, and investigates the fuel consumption potential of PS-HEPSs. For helicopter operating conditions, the operating characteristics of power-split transmission systems are analyzed. It is found that the operating state (power split and power cycle) of PS-HEPSs depends only on the engine speed. Based on that, the paper proposes a three-parameter matching method of transmission ratios with an objective of maximum power-split speed range. Subsequently, by establishing a mathematical model of the PS-HEPSs for helicopters and adopting dynamic programming (DP) as the energy management, the fuel consumption and working points of power sources are calculated under the specific mission and also compared with the fuel economy of parallel hybrid electric propulsion systems (P-HEPSs). Results show that, by using the proposed method, the input power-split hybrid electric propulsion system and output power-split hybrid electric propulsion system (OPS-HEPS) have similar fuel consumption, but both consume less fuel than P-HEPSs. In terms of residual power, the OPS-HEPS still has 150 Kw left, because the generator can perform as a drive motor to provide torque. Although the power-split hybrid electric systems were first applied for automobiles, the comprehensive analysis shows that the PS-HEPSs are more suitable for helicopters because the constant speed of the output shaft reduces control complexity for PS-HEPSs. [ABSTRACT FROM AUTHOR]

To meet increasing energy demands, reduce environmental impacts, and increase economic benefits, many water utilities have installed on-site renewable energy generation and storage facilities. These are commonly referred to as behind-the-meter (BTM) energy systems. This paper proposes a systematic optimization approach to the design and evaluation of water distribution systems (WDS) with BTM solar energy. The trade-offs between economic and environmental costs and the benefits these systems can have throughout their design life are demonstrated using a real-world pressurized irrigation system. Due to the large number of decision variables required during the optimization process and the associated high-computational cost, a hydraulic-power-based search-space reduction method has been developed. This method identifies common features of the pipes across a network based on the potential maximum flow and residual pressure head at the outlet of each pipe, so that pipes having similar hydraulic power capacity and thus similar diameters can be grouped together as a single decision variable. This effectively reduces the search space size and significantly increases the optimization efficiency for complex WDS optimization problems such as the optimal pipe design of WDS incorporating BTM solar energy in this study. In this paper, trade-offs between two objective function values [the total life-cycle cost and total life-cycle greenhouse gas (GHG) emissions] are investigated. A reduction in GHG emissions leads to an increase in the total cost and vice versa. It has also been found that the incorporation of BTM solar energy can significantly improve both objective function values. However, the optimal diameters of pipes and therefore the capital costs and GHG emissions are not sensitive to the increase in solar photovoltaic sizes. [ABSTRACT FROM AUTHOR]

The design of rock-socketed pile foundations requires careful consideration of critical construction aspects such as the socket roughness and smear for accurately estimating the shaft load capacity. Despite the effect of smear being investigated extensively over the years, previous studies are limited in accurately characterizing the effect of smear on the shaft response. This paper presents a comprehensive investigation on the load-bearing mechanisms of model smeared rock-socketed piles with different smear fabrics (configurations) at the pile-rock interface. These model piles were loaded into synthetic soft rocks while being intermittently subjected to three-dimensional (3D) X-ray computed tomography (CT) imaging. Interpretations from the X-ray CT images were correlated with the pile-head load-displacement behavior to gain insights into the load transfer attributes between the pile, smear, and rock. The various interactions between these components were deduced by monitoring the micromechanics at the pile-rock interface through shaft energy utilization, interface void volume, smear volume, and sand density mapping. Based on the observations, it was inferred that the load transfer between the smear and the rock is primarily dependent on the percentage and position of smear occupancy at the interface. Results indicated that for the partially smeared interfaces, the interface mechanics are a combination of smeared and clean shafts with the residual resistances dependent upon the combined compression of smear and rock debris at the interface. Moreover, it was observed that the continuous presence of smear for more than half area of the leading faces of the pile asperities results in the smeared regions of the pile taking precedence over the unsmeared regions in governing the load-carrying capacity of the shaft. The discussions presented in this study can provide a strong base to further study the smear effect, subsequently aiding in enhancing the existing design guidelines to economically construct piles in soft rock. [ABSTRACT FROM AUTHOR]

Wing smarting and eliminating conventional control surfaces are fundamental parameters for improving aircraft aerodynamic performance in future aviation. Twist is a well-known tool that, along with the development of morphing technology, can play a crucial role in controlling next-generation aircraft. However, wing twisting with a control approach requires many aerodynamic studies, particularly at the high aft-swept angle; this is more noticeable in the flying wing configuration. In this paper, a control strategy based on twist morphing has been evaluated aerodynamically at the Swing, a flying wing configuration. Extraction of aerodynamic coefficients and flow field on the wing have been performed using the computational fluid dynamics (CFD) method in an incompressible flight regime. To comprehensively cover the control needs, two control concepts have been introduced, called independent and nonindependent twist. Within the concept of independent twist, a co-oriented twist arrangement (Co-OTA) and counteroriented twist arrangement (Cun-OTA) are applied to the wings, which are used to produce pitching and rolling moments, respectively. The results show these control arrangements have high efficiency at low angles of attack (AoAs), but as the AOA increases, their aerodynamic performance will gradually decrease. In this regard, a significant challenge for Cun-OTA is producing the yawing moment during roll maneuvering. Attempts to solve this problem have led to the idea of a compound twist arrangement (CTA). The existence of a control arrangement to generate yawing moment is beyond the capacity of the independent twist concept. The nonindependent twist has been introduced as a solution to this issue. Conventional control surfaces have various weaknesses, one of the most important of which is the unfavorable effects on aerodynamic efficiency; the reduction of aerodynamic efficiency leads to a drop in flight endurance and an increase in fuel consumption. At a step forward, with the approach of wing smarting and morphing technology, the tasks of conventional control surfaces can be delegated to the wing itself. Therefore, it will be possible to remove the control surfaces and integrate the wing. In this article, according to the mentioned approach, an attempt was made to introduce a control strategy based on the geometric twist. In this strategy, the value and direction of the twist applied to each wing produces a specific control arrangement. Control arrangements (three types of arrangements) are involved in producing longitudinal and lateral and modified lateral moments. The results indicate that the use of twisting in aircraft control is efficient for a wide range of flight conditions, and this capability exists to be used in the next generation of aircraft. In this way of control, challenges are deliberately related to the design of the operating mechanism, safety issues, and weight. [ABSTRACT FROM AUTHOR]

This paper evaluated the cement-based materials incorporated with novel solid–gel phase change materials (PCMs) for improving the energy efficiency of building envelopes. This novel PCM is form-stable, which will not leak as solid–liquid PCMs do and not need encapsulation, and it features high energy-storage capacity. Experimental results showed that the thermal properties of cement-based materials were improved as the increase of PCM content. A 30% replacement of sand by volume with PCM can increase the latent heat of the mixture from around 0 to 7 J/g and decrease the thermal conductivity of PCM mortar based on the generalized self-consistent (GSC) model by about 20%. However, the workability and mechanical properties were compromised. The simulation results indicated that 30% PCM-incorporated walls can contribute to 5% energy saving for cooling in a whole year and 12% reduction in peak cooling load compared with the reference without PCM. The proposed PCM composite offers a promising avenue to achieve energy-efficient building envelopes. [ABSTRACT FROM AUTHOR]

Due to the mismatch between gas production and consumption in the gas delivery system (GDS), reduced customer demand can easily lead to overpressure and gas release. Companies mainly use high-pressure release (HPR) to lower the GDS pressure, which results in significant energy losses for compression and gas separation. This paper (1) proposes a low-pressure release method (LPR) for users' low-demand scenarios to avoid regulating air separation units, and (2) provides a way for obtaining optimal parameters for LPR when used alone and together with HPR. LPR released low-pressure gas by lowing the compressor inlet guide vane opening (IGA) or the inlet valve opening to reduce the compressor load, outlet pressure, and GDS pressure, and reduce the energy consumption of the compressor. Case studies showed LPR reduced effectively the gas emissions and compressor operating energy. When LPR is used alone, the maximum reduction in gas emissions and compressor operating energy consumption compared with HPR was 6,049 Nm3 and 900 kW·h , accounting for 62.96% and 2.18%, respectively, and the gas emission rate was reduced from 0.11% to 0.04%. When LPR was used together with HPR, 43.88% oxygen emissions and 0.28% total compressor energy consumption were reduced, and the total conditioning time can be effectively reduced from 42 to 10 min. The method increases the ability of the compressor to regulate the GDS. [ABSTRACT FROM AUTHOR]

This paper establishes the minimum amount of energy required by a simple system, a benchmark established on the basis of current technology and the requirements by energy regulators, weighting costs, and efficiency. The first step is to normalize the energy intensity (kWh/m3), which is the quotient between the energy consumed and the volume pumped, with the geometric gradient. The new normalized parameter is more objective than the commonly standardized one with the pumping head due to its dependence on friction. In addition, it makes it possible to naturally disaggregate energy needs (in useful and dissipated energy during transport) to establish a target energy intensity and evaluate existing savings. The quotient between energy intensities (actual and target) allows qualifying transport efficiency. At the same time, it permits extending the policy of energy labeling to pressurized water transport, which has been proven to be a successful energy efficiency strategy. The concepts described in this paper establish the minimum amount of energy required by a single system. A simple system is defined as a drive with a single input point and a single output point. The establishment of the minimum amount of energy required allows a reference point to be established, and with this, a possible margin for improvement. These indicators, defined in a simple way and requiring little data, can be of great help to know the current state of simple systems and compare them with the best version of these, as well as with an intermediate state improved on the basis of current technology and the requirements of energy regulators, weighing both costs and efficiency. [ABSTRACT FROM AUTHOR]

China's Hot Summer and Cold Winter zone, with a 550 million population, accounts for 45% of China's building energy consumption; as such, building retrofits could offer substantial energy savings. This paper presents results from a dynamic thermal modeling study of a typical urban multistory residential building under three types of air conditioning (A/C) operating schedules. Seven energy-saving retrofit measures (external wall insulation, roof insulation, double-glazing, air infiltration control, window shading, communal staircase design, and energy-efficient A/C) were evaluated, and the retrofit strategy with the highest annual energy savings and lowest thermal discomfort was identified. This retrofit strategy was subsequently evaluated for other flats (apartments) with different orientations and positions in the typical building. The annual space-conditioning energy could be reduced by 59%–68%, depending on the flat location, orientation and A/C operating schedule. The findings were then scaled up to estimate the potential energy savings in the city of Chongqing. More than 320 multistory residential buildings were represented by 12 archetypes. Space-conditioning energy consumption was reduced by up to 58% (18.8 TWh). This work provides evidence of the potential energy savings of city-scale retrofit that could aid China in reducing building energy consumption and achieving net-zero carbon emissions by 2050. It was possible to explore a wide range of refurbishment options for China's highly energy-consuming Hot Summer and Cold Winter zone with hot, humid summers and mild, chilly winters using dynamic thermal models. The simulation models developed in this paper revealed that double-glazing with air infiltration control is the most effective retrofit measure for middle-floor flats, but for top-floor flats, roof insulation is the most effective; south-facing flats consume more high energy consumption than north-facing flats. Furthermore, high-rise buildings consume less energy than low-rise buildings per square meter, and one-bedroom flats consume more energy than three-bedroom flats per square meter. This study also demonstrated the procedure to develop thermal comfort evaluation methods, A/C operating schedules, and construction parameters from literature in this climate zone when there were no standards or databases available. Findings offer a tangible, clear retrofit strategy that considers different A/C operating schedules, flat locations, and building archetypes. It can assist decision-making by practitioners and homeowners aiming to upgrade the building stock of this climate zone which covers 3.4 billion m2 with a 550 million population to reduce energy consumption and improve occupant comfort. [ABSTRACT FROM AUTHOR]

This paper investigates an optimal orbit design method for single-satellite synthetic aperture radar tomography (TomoSAR) missions. Satellites require multibaseline observations for three-dimensional imaging. Thus, we need to weigh performance indicators such as global coverage, sampling rate, fuel consumption, and revisit accuracy. Considering these performance indicators, this paper proposes a multiobjective optimization algorithm based on multireference transfer orbit (M-RTO), which demonstrates superiority in fuel consumption. Fuel consumption is the primary optimization objective as it determines the lifetime of the satellite. First, we use Pareto optimization for the objectives of revisit time and fuel consumption. Then, we adopt an adaptive hybrid genetic algorithm (AHGA) for the objectives of revisit accuracy and fuel consumption. Numerical simulation verifies that compared with the single-reference transfer orbit method, the multireference transfer orbit method decreases fuel consumption by ∼37% , and the rest of the performance indicators meet the mission requirements. [ABSTRACT FROM AUTHOR]

The building sector is one of the most resource-exhausting areas in global energy consumption. Maintaining good thermal comfort for occupants is the leading energy demand in buildings. The primary purpose of the current study is to identify the development of research areas on occupant comfort, pinpoint the gaps in knowledge and recommend directions for future studies. A scientometric analysis and a comprehensive systematic literature review are conducted using 792 sources. It is evident from the exponential increase in published papers that scholars are highly interested in this research topic. However, discrepancies remain between the two fundamental models of evaluating thermal comfort. There is a pressing need to balance thermal comfort while increasing energy efficiency. The foundation of achieving this balance can only be done by correctly evaluating the surrounding environment of occupants and understanding all the factors influencing human thermal comfort conditions. There is also a high potential in employing industry 4.0 technologies to assist in designing more innovative solutions for thermal comfort. Furthermore, there is a need for local thermal standards targeting specific regions. The lack of interoperability between 3D building information modeling (BIM) and energy simulation tools remains an obstacle. [ABSTRACT FROM AUTHOR]

Office buildings, characterized by high internal heat gains, represent a major share of energy use, mainly due to HVAC systems, especially in commercial facilities. Such energy use becomes more significant in locations with harsh climatic conditions. The careful design, selection, and operation of HVAC and energy systems, however, can contribute to major reductions in the energy use in buildings. In this paper, we present the outcomes of a study conducted to assess the impact of HVAC operational strategies on energy use in office buildings in the hot and humid climate of Saudi Arabia. The study utilized detailed building-energy simulation coupled with utility-use data. The results revealed annual electrical energy savings ranging from an average of 1.9% for each 1°C increase in the thermostat setpoint temperature up to 42.4%, when limiting HVAC system operation to occupied hours only. On an average, there was about a 1.4% penalty in the annual energy for each hour of increase in the HVAC system start-up time. However, this penalty should not be avoided at the expense of compromising thermal comfort. In summary, a combination of appropriate HVAC operational strategies can have a significant impact on a building's annual energy savings, as demonstrated in the presented case study. [ABSTRACT FROM AUTHOR]

This paper proposes an active shape control method for an antenna control system under a limited number of power supplies with a reduction in weight and cost. An analytical model of a grid reflector with embedded piezoelectric actuators was first established, from which an influence coefficient matrix was derived for controller design. A shape controller was designed by synergistically optimizing the actuator group and power supply voltage. The optimization objectives include the root-mean-square (RMS) error, control energy consumption, and a multiobjective combination of both. The design variables include the actuator group and power supply voltage. A dynamic actuator group design with a detached power supply is proposed to improve the control performance, which also significantly increases the design domain of this optimization problem. A hybrid optimization method is proposed based on the general genetic algorithm and least-squares method to reduce the difficulty and complexity of this optimization problem with a large-dimensional design domain. Numerical simulations were carried out to illustrate the effect of the proposed hybrid optimization control method. The results indicate that the RMS error can be reduced by more than 90%, even if only two power supplies are used. The introduction of a group design with a detached power supply can clearly improve the control performance, especially by reducing the energy consumption. By employing multiobjective optimization with a uniform consideration of the RMS error and control energy consumption, a series of Pareto-optimal results can be obtained, and these results can provide meaningful references for engineering designers. [ABSTRACT FROM AUTHOR]

Long-distance oil pipelines consume extensive energy during the operation. Accurate prediction of pipeline's energy consumption is the basis of intelligent management and energy-saving plan. This work demonstrates an effective data-driven model to predict a pipeline's energy consumption. The model first extracts features through correlation analyses and then uses a hybrid support vector machine for prediction. In the hybrid model, the fruit fly optimizer, simulated annealing algorithm, and cross factor are fused to form an improved fruit fly optimizer used to optimize the traditional support vector machine. The proposed model is tested on a pipeline in China, and the results indicate that the model has a high prediction accuracy (prediction accuracy is measured by one minus mean absolute percentage error, and the accuracy exceeds 80%). Compared with the three benchmark models, the accuracy of the proposed model is increased by 4.18%–25.47%. This paper discusses the influence of the kernel function on the prediction. The results show that the support vector machines with radial basis kernel function and polynomial kernel function perform well in Dataset I, while support vector machines with radial basis kernel function, polynomial kernel function, and linear kernel function perform almost the same in Dataset II. Moreover, this paper also discusses the input of the model on a deeper level. More experiments show that removing highly repetitive input can ensure higher prediction accuracy in engineering and reduce the complexity of the model. [ABSTRACT FROM AUTHOR]

The on-ramp area has been a hot spot for research as a bottleneck area. In this paper, an on-ramp cooperative merging control strategy is proposed to make full use of active cooperative vehicles, and alleviate the negative influence of merging on the main road. First, a two-stage framework is proposed to illustrate the merging strategy. At the vehicle level, the cooperative merging controllers of vehicles are designed based on an optimization algorithm that considers the penalty function. At the traffic level, the cooperative distance of the upstream and downstream vehicles at the main road target merging position are optimized to improve merging efficiency. Meanwhile, to ensure the implementation of the proposed strategy in mixed traffic, we propose a method to determine the lead vehicles based on the proximity principle. Numerical experiments were performed to verify the fully proactive and cooperative merging (FPCM) strategy, the effectiveness of the vehicle cooperative controllers, the necessity of optimizing the cooperative distance, the effect of different velocities on the main road and ramp, and the effectiveness of determining the lead vehicles. In the case of multivehicle merging, the proposed strategy can improve merging efficiency by 44.42% and save fuel consumption by 39.11%. In the case of a single merging vehicle, the optimized proposed strategy can improve merging efficiency by 48.4% and save fuel consumption by 31.4%. Finally, the simulation experiments for the different maximum speeds of vehicles show that a sufficient speed adjustment range can improve the advantages of the strategy. [ABSTRACT FROM AUTHOR]

This paper discusses the influence of passive façade design of a detached residential building on its energy performance. The research consists of a parameter analysis performed using commercially available software to assess the influence of different façade wall structures, glazing types, and window-to-wall ratios (WWRs) on the energy required for heating and cooling of a detached building with a sunspace. Eighteen variants of façade wall structure (W1–W18) and 20 variants of façade window glazing type (G1–G20) were created for the base model of a building with a sunspace (Model-FW) for the purpose of investigating their influence on energy consumption in the building. All variants of the base model were examined for WWR=20% , WWR=40% , and WWR=60%. The research was conducted for the location of the urban area in the city of Niš, Serbia. The analysis of the results showed that the best-performing façade wall structure in terms of heating energy consumption was Variant W1, which consists of a 0.40-m-thick concrete layer, 0.14-m-thick expanded polystyrene (EPS) thermal insulation layer, and a render/plaster layer on the outside and the inside with the total thickness of 0.03 m. The W1 variant had the largest thermal mass and thermal insulation thickness of all considered variants. Regarding the total energy required for heating and cooling, in the most favorable W1 model, the energy savings were 75.14% (WWR=20%), 35.04% (WWR=40%), and 17.15% (WWR=60%). The analysis of different glazing types showed that triple low-emissivity glazing performed the best in terms of heating energy required for a building with a sunspace. Among the considered models, benefits from triple glazing systems in terms of total energy consumption were 41.59%, 61.04%, and 47.70% for WWR=20% , WWR=40% , and WWR=60% , respectively. [ABSTRACT FROM AUTHOR]

With the continuous progress of urbanization and the rapid development of building facade floodlighting, problems such as excessive lighting, serious light pollution, and high energy consumption are becoming increasingly prominent. In this paper, three methods comprising field measurement, questionnaire survey, and energy-efficiency simulation were integrated to develop the floodlighting luminance control curve of a building facade at night and also to carry out an energy-efficiency analysis. Through the field measurement of the floodlighting of the building facade, combined with the method of scene simulation, several virtual combined scene pictures with different sky luminance and different floodlighting luminance of the building facade were made. Furthermore, the optimal floodlighting luminance range as the sky luminance varies was obtained in the form of a questionnaire when the virtual scene pictures were presented on a computer. Then, the floodlighting luminance control curve with the decrease of the sky luminance was developed to achieve the purpose of reducing energy consumption. Finally, energy efficiency analysis of the lighting control curve was undertaken. The result revealed that when the sky background luminance is 8.98–0.51 cd/m2, the recommended floodlighting luminance range of the building facade is 6.13–4.44 cd/m2. What is particularly interesting is that the energy-saving effect is remarkable, and the energy-saving rate at each time is greater than 15%. [ABSTRACT FROM AUTHOR]

This paper presents a novel strategy for giving priority to automated guideway transit vehicles (AGTVs) in mixed traffic flow. From the perspective of road segments, a moving-block operation mode (MBOM) was proposed to help AGTVs eliminate the dependence on dedicated lanes. The car-following and lane-changing behaviors of both AGTVs and general vehicles were modeled using the theory of cellular automata. From the perspective of intersections, an MBOM-based dynamic multirequest signal priority (DMSP) model was developed to support the decision of multiple priority requests at the intersection. Notably, the DMSP model can synchronously deal with early green and green extension requests from the same or different phases. Extensive microsimulation experiments were conducted to examine the proposed strategy at various levels of traffic volume and AGTV headway. The results indicated that the MBOM outperforms the traditional strategy of setting up full-time or intermittent dedicated lanes, particularly in traffic conditions where the headway of AGTVs is longer than 300 s and the traffic volume is lower than 9.0 kpcu=h. Furthermore, the MBOM-based DMSP strategy was evaluated in terms of the performance of both traffic and energy efficiency. The per person travel time and coal consumption decreased by 6.93% and 1.61%, respectively, demonstrating the effectiveness of improving operational efficiency and sustainability of public transit. [ABSTRACT FROM AUTHOR]

The reconfiguration of a constellation with several faulty satellites concerns performance improvements in multiple fields, which can be regarded as a multiobjective optimization (MOO) problem. In the optimization design, it is inevitable to evaluate the constellation performance and providing the reconfiguration strategy thousands of times is time-consuming. To decrease the high computational expense, this paper proposes an accurate and efficient MOO method based on the kriging surrogate model, termed as the surrogate-based MOO (SBMOO) algorithm. A new hybrid refinement method is presented to select infilling samples for updating the surrogate model. Different from the orbital phasing maneuver, the low-thrust reconfiguration strategy is implemented to optimize the transfer trajectory with low fuel consumption, by changing the orbital inclination and right ascension of the ascending node. With the tradeoff between the constellation performance and the uniformity of fuel consumption, the MOO problem of constellation reconfiguration can be investigated and settled by the proposed SBMOO algorithm. The simulations confirm that the preferable constellation reconfigurations are achieved with a low computational expense for optimization and a low fuel cost for orbital transfer. [ABSTRACT FROM AUTHOR]

Water distribution is an important service due to its economic, social, and health purpose. Therefore, a continuous supply is required to keep consumers satisfied. However, emergency scenarios of water scarcity, caused by recurrent or exceptional droughts, can impair supply, forcing intermittent operation. This operation has clear disadvantages, such as the increased risk of pathogen intrusion and pipe bursts during filling. However, a reduced number of operation hours, mainly during high-pressure periods, can significantly reduce leakage. It is helpful to preserve the quantity and quality of the main water source during a longer period to maintain its multiple purposes. Considering this new operation, pump stations must be adapted, and energy consumption can significantly increase if an optimal schedule is not determined. Accordingly, this paper studies different levels of intermittency as a strategy to operate under severe water scarcity conditions and identify the gains that can be made in leakage reduction, combined with optimal pump operation, to maintain operational costs at the same level, or better, as continuous operation. [ABSTRACT FROM AUTHOR]

A dynamic dispatch program schedules the controllable generation units during the entire dispatch period to minimize the economic cost and increase other benefits. On the other hand, demand response (DR) improves energy utilization and increases power quality. The coordination of dynamic dispatch with DR is potentially important to increase the benefits to distribution network areas. In this paper, a dynamic multiobjective optimal dispatch (DMOD) problem is developed to effectively integrate with the time of use (TOU)-based DR for optimal distribution network dispatch. DR is concerned with the optimal pricing during peak, off-peak, and valley periods such that the load curve of the dispatch is optimally shaped. In a combined dispatch procedure, dynamic multistage generators, energy storage operations, and power exchanged between upstream grid dispatches are simultaneously optimized to decrease the system operational cost and the active power loss along with the responsive load based on a DR scheme. In addition, a hybrid teaching-learning multiobjective particle swarm optimization algorithm (HTL-MOPSO) is proposed for solving the DMOD incorporation with the DR model. The proposed method is validated in a simulation study using an IEEE 33 bus system. The comprehensive numerical results reveal not only the efficiency of the proposed combined DMOD with the DR model but also the practical DR benefits to customers and distribution network operators. [ABSTRACT FROM AUTHOR]

Building's energy and water consumption and associated utility costs can be significantly reduced if proper energy and water-efficiency upgrades are applied. Due to the limitations of the upgrade budgets and the availability of a wide range of energy and water-efficiency measures, decision makers are always faced with a challenging task to identify optimal sets of building upgrade measures. This paper presents the development of a new model that is capable of identifying an optimum selection of building upgrade measures to minimize equivalent annual cost (EAC) while maintaining the performance of existing buildings and complying with available upgrade budgets. The model is developed in three main phases: (1) formulation phase, where decision variables, objective function, and constraints are identified and formulated; (2) implementation phase that performs the model computations and specifies the model input and output data; and (3) performance evaluation phase where two case studies of university buildings are analyzed to demonstrate the capabilities of the model. Furthermore, a case study from the literature is used to verify the model performance and document its new capabilities. The primary contributions that this research adds to the body of knowledge are: (1) developing new model that can identify optimal selection of building upgrades while complying with user-specified requirements for building operational performance and available upgrade budgets in short computation time, (2) modeling a wide range of upgrade measures for building fixtures and equipment as well as envelope components, and (3) integrating updatable databases from vendors and suppliers to generate up-to-date and practical recommendations. The model is designed to use OpenStudio to analyze combinations of feasible alternatives such as HVAC systems, wall and roof insulations, window types, and water heaters to calculate the corresponding building energy consumption. The model is designed to perform its computations using binary linear programming to identify global optimum solutions in short computational time. The results of the case studies illustrated the capabilities of the model in optimizing building upgrade measures to reduce the building utility costs up to 38% while complying with specified upgrade budgets. [ABSTRACT FROM AUTHOR]

Natural gas transmission networks (NGTNs) are the main facility connecting upstream gas sources and downstream consumers. For a cyclic NGTN with multiple gas transmission routes, different gas transportation schemes will affect not only the energy consumption of the system but also the pipeline transportation costs paid by consumers. In this paper, three operation optimization models are established to determine the optimal operating state of a multiroute cyclic NGTN under different scenarios. The three mathematical models correspond to three different objective functions: minimize the cost of compressor energy consumption, minimize the expense of pipeline transportation, and minimize the sum of the two expenses. The decision variables of the models include the pipeline flow rate, the number of operating compressors, and the outlet pressure of the compressors. In addition, a series of linear and nonlinear constraints of nodes, pipelines, and compressors is also proposed to guarantee the feasibility of solutions. The operation optimization problem is solved by the General Algebraic Modeling System (GAMS), and the effectiveness of this method is tested on a small double-route cyclic NGTN and a large three-route cyclic NGTN. The results show that the developed optimization model is able to find optimal solutions under different models. In the cyclic network, the difference in the flow distribution of gas transmission routes is the key factor affecting the optimization result. In addition, compared with the compressor energy consumption cost minimization objective, the pipeline transportation expense minimization objective can create greater economic benefits for consumers. In the two network cases, consumers can save 14.51 and 59.18×104 RMB. Finally, optimizing the two objectives at the same time makes it possible to achieve an effective balance between them. [ABSTRACT FROM AUTHOR]

The deep surrounding rock under true triaxial stress is easy to break at the new excavation face, which will induce engineering disasters to threaten personnel and equipment. Many studies have shown that the intermediate principal stress (IPS) has a great influence on rock failure. To accurately understand the influence of IPS on the gradual failure mechanism of the new excavation face under true triaxial stress and extract the key precursor information of rock failure, this study is based on true triaxial tests of acoustic emission (AE) monitoring, which provides a creative explanation to the phenomenon that sometimes the sudden increase of the AE counts rate (ACR) and the energy release rate (ERR) changes asynchronously. This paper analyzes the influence of IPS on the crack type in the failure process, studies the transitional behavior and gradual evolution of AE dominant frequency, and presents the precursor information index for rock failure. The results show that the sudden increase times of ACR and ERR under different IPS values are different. The rock under lower IPS is prone to produce intergranular fracture with low energy consumption, while the rock under higher IPS is prone to produce transgranular fracture with high energy consumption. Near the peak stress, the dominant frequency at lower IPS shows obvious downward transitional behavior, and the dominant frequency under higher IPS presents downward and upward transitional behavior. This study verified that tIII−max can be used as the key precursor information for predicting rock failure. [ABSTRACT FROM AUTHOR]

An alcohol-based emulsified fuel is formed by mixing ethanol, biodiesel, and water in different proportions. This fuel can be used in internal combustion engines to reduce fossil fuel consumption. In high-temperature environments, the microexplosion phenomenon of alcohol-based emulsified fuel can be observed directly. In this study, a high-temperature fuel evaporation test device was set up. The microexplosion process of alcohol-based emulsified fuel with varying water content (0%, 1%, 2%, and 3%) in different temperatures (773 K, 873 K, and 973 K) was studied by high-speed photography, and the data were analyzed by morphological treatment. To evaluate the microexplosion characteristics of alcohol-based emulsified fuel, some kinetic parameters—such as microexplosion delay, mean interfacial tension, number of bubbles, and mean microexplosion intensity—were proposed. The results show that the kinetic parameters put forward in this paper are reasonable for evaluating the microexplosion process. If the water content in the alcohol-based emulsified fuel is kept the same, the microexplosion delay decreases, while the mean interfacial tension increases with increasing temperature. If the evaporation temperature is kept the same, the microexplosion delay and the number of bubbles increase with the content of water increasing. Within the range of tested content of water and temperature, the mean microexplosion intensity of emulsion fuel is 0.05366 N·(m·s)−1 when the temperature is 973 K and the content of water is 3%, which is the largest. [ABSTRACT FROM AUTHOR]

Microwave-assisted concrete liberation and aggregate recycling is highlighted by many research groups due to its efficient and effective recycling process. In this paper, a series of experiments are conducted to study the heating results of concrete under microwave and conventional heating processes. The temperature variations of concrete under two different heating approaches are obtained. The crack characteristic and material damage during the different heating processes are illustrated. Particularly, the energy efficiency was investigated for two approaches. Results proved that concretes were broken more effectively under microwave irradiation than in conventional furnaces, and the aggregates can be easily separated under the sufficient power input. Scanning electron microscope (SEM) analysis proved that after microwave treatment, intergranular fractures are formed at mortar-aggregate interfaces, few cracks occurred after conventional heating processes. The research proves that, compared with conventional heating, microwave irradiation could liberate concrete and recycle aggregate effectively, with less heating duration and lower energy input required. [ABSTRACT FROM AUTHOR]

Benchmarking the energy efficiency of buildings is important for optimizing the efficient use of energy and reducing carbon footprint. Healthcare facilities have especially high energy usage, but the historical difficulty of collecting energy data from a relatively large number of healthcare facilities has made it challenging to develop the appropriate benchmarking system. In this paper, we seek to foster the task of benchmarking the energy efficiency of healthcare facilities using three different methods: multiple linear regression (MLR), generalized additive model (GAM), and energy performance index (EPI). The analysis was applied using a unique dataset that contained information on energy consumption and various building features for 22 large-size public hospitals managed by the Shanghai hospital development center (SHDC). Findings suggest that different benchmarking methods yield substantially different energy performance ranking results. Furthermore, a comparative analysis of the three benchmarking methods was conducted in terms of goodness-of-fit, consistency, and robustness. The results show that MLR tends to be the most consistent and robust benchmarking model, while GAM appears to have the best goodness-of-fit. The proposed methodology can assist hospital managers identify potential improvements for more efficient use of energy in healthcare facilities. [ABSTRACT FROM AUTHOR]