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• Literature review papers related to the tourism-energy nexus are analyzed. • Four main groups are identified considering the quantitative methodology used. • Topics and discussions on the nexus between tourism and energy are developed. • Future research is discussed. The high dependence of tourism activities on energy consumption, and particularly on non-renewable energy, is a major barrier to building sustainable tourism models. For this reason, the analysis of tourism and energy use is a growing field of study within sustainability debates. Despite this, there is a gap in the literature and, to the best of our knowledge, there is no previous study that critically reviews the vast literature on the energy-tourism nexus. This paper aims to fill this gap in tourism knowledge. The main objective of this article is to conduct a systematic review of scientific studies with a quantitative empirical basis that examine this nexus, trying to answer the following questions: What are the main methodologies used to approach the tourism-energy nexus? which indicators or variables are relevant?; is there a consensus on the results?; and what are the main lines of discussion on the use of energy in tourism? To this end, we particularly focus on the main methodologies, results and perspectives during the period 2001–2021. A total of 1,189 articles were reviewed by abstract and title, 236 were included for the full review and 163 were finally selected. The results show how the nexus and energy dependence of tourism is assessed mainly from four major methodological groups: G1) econometric models, regressions and other statistical methodologies (67% of the sample); G2) surveys, questionnaires and energy audits (15%); G3) Life Cycle Analysis (13%) and G4) other approaches and environmental impact indicators to assess the relationship between energy and tourism (5%). The analysis between the causal relationships between tourism development, economic growth, energy use, environmental degradation and energy efficiency of accommodations are the main issues evaluated, considering a wide range of indicators/variables. Based on the gaps and limitations found in the literature review on tourism and energy, it is discussed how some findings should be interpreted with caution due to their methodological approaches and differences. Finally, some of the main lines of future research in this field are also presented. [ABSTRACT FROM AUTHOR]

• The internal losses of track systems can be represented by a single coefficient. • More complex models are needed to optimize the energy efficiency of track systems. • The literature describes the phenomena leading to internal losses in track systems. • Some of those phenomena are described by at least several alternative models. • Complex models of the internal losses of rubber-track systems need to be developed. This article summarizes the known methods for calculating the internal resistance of tracked undercarriages. The values of the coefficient of internal resistance for sample tracked vehicles are available in the literature and presented in this paper. Although they are suitable for simple computations, they cannot be used to optimize the energy efficiency of new generation tracked undercarriages. This problem might be solved by the models where every phenomenon leading to energy dissipation during vehicle motion is described by a separate submodel as a function of vehicle speed, track tension, undercarriage layout, design features of the undercarriage components, etc. This kind of model is still missing for vehicles with conventional rubber tracks. The article presents multiple state-of-the-art models describing rolling resistance of road wheels, bending resistance of rubber belts, etc., including the models of belt conveyors resistance. A vast majority of the phenomena discussed herein are described by several incompatible models whose parameters have not yet been determined for conventional rubber tracks. Consequently, in the second and the third part of the article, the authors have undertaken a theoretical and experimental studies on the methods for calculating and optimizing the internal motion resistance of vehicles with conventional rubber tracks. [ABSTRACT FROM AUTHOR]

In this paper, two generic photovoltaic (PV) panels (poly-Si and mono-Si) were experimentally tested in typical Mediterranean climatic conditions. The focus of the applied experimental approach was to examine the effect of backside convective thermal profile and its impact on temperature distribution, i.e. on panel electrical efficiency. Therefore, a series of measurements was made in 2015, from April to July, as well as CFD modeling in order to obtain a detailed analysis of the possible working regimes. According to the obtained experimental and CFD results, the present design of typical PV panels have an unfavorable impact on PV panel electrical efficiency. Namely, typical contemporary panel designs lead to two typical backside convective air temperature profiles which have a direct impact on the effectiveness of natural cooling. As shown in the obtained measurements, the specific convective profiles at the backside of PV panels have a significant influence on the degradation rate of panel electrical efficiency in the estimated amount of 2.5% up to 4.5%. The results of the research discussed in this paper signal the need to provide a possible redesign of the backside surface in conventional PV panels, in order to increase their average efficiency (more efficient backside thermal dissipation). [ABSTRACT FROM AUTHOR]

Multistage centrifugal pumps are widely used, and improving their efficiency is an indispensable part of energy conservation. A multi-objective optimization method combining experimental design, surrogate model, and optimization algorithm is proposed to re-design impellers and diffusers for improving pump performance. In the paper, nine variables were selected by the Plackett–Burman design with the head and minimum efficiency index (MEI) as the optimization objectives. The Gaussian process regression (GPR) was used to establish the surrogate model, and multi-objective optimization of the impeller and diffuser was carried out by non-dominated sorting genetic algorithm II (NSGA-II). The optimization results show that head and efficiency at the designed point 1.0 Q d increased by 8.8% and 2.8% respectively, and C MEI decreased by 1.34%. Meanwhile, the energy loss and flow characteristics of the original and optimization models were analyzed with the entropy production theory. Compared with the original model, the energy loss was reduced, and the flow in the interaction area between the impeller and diffuser becomes more stable for the optimized model. Moreover, the influencing mechanism of the pump geometrical parameters on the hydraulic performance and flow characteristics were discussed and analyzed. • A PB-GRP-GA multi-objective optimization method is proposed. • Internal energy losses were identified by Entropy Production Rate. • Influence mechanism of geometry on performance was revealed. • Higher MEI of pump model was achieved and verified by experiments. [ABSTRACT FROM AUTHOR]

The electrification of many mobile applications such as wearable robots has led to the need for carrying batteries to store electrical energy. However, low-efficient actuators require larger batteries that have to be carried along, which limits the range and performance of such devices. In addition, collaborating with robots require safe cobots and actuators. To address this challenge, parallel and series elastic actuators have been adopted in many applications to increase safety and energy efficiency. Meanwhile, some industries, including the automotive industry, have put much research effort into dual motor actuation to decrease the energy consumption of the overall drivetrain. In this paper, we introduce a Spring-Embedded Planetary Dual-Motor Actuator (SEP-DMA) which combines both technologies using a planetary gear unit and a spring. We derive and validate a dynamic model for all possible configurations and discuss their operating modes, including active and passive actuation. To demonstrate the potential of the actuator, we compare it with a traditional stiff actuator consisting of a gearbox and electric motor. The former shows a 40% decrease in the overall energy consumption for a standard task of lifting and oscillating a mass. • Development of a dual motor model using a PGT and embedded spring. • The DMA can switch among different operating modes by enabling/disabling compliance. • Simulations show an efficiency reduction of 40% for an oscillating lifting task. • Experiments show a good correlation between the proposed model and experimental data. [ABSTRACT FROM AUTHOR]

Environmental degradation has become one of the major challenges facing the global community. This paper aims to explore the more effective options to combat environmental degradation by investigating the linearity and nonlinearity (trade openness set as a threshold variable) of energy efficiency, natural gas, renewable energy and ecological footprint. To this end, linear and non-linear panel models were constructed using panel data from 60 countries. The results of the linear analysis show that improving energy efficiency, and increasing the consumption of natural gas and renewable energy are conducive to inhibiting environmental degradation. Energy efficiency has the most significant negative correlation with ecological footprint, followed by renewable energy, and then natural gas, implying that improving energy efficiency and developing renewable energy is a more effective strategy to combat environmental degradation. The results of the nonlinear analysis show that there are threshold effects of trade openness between energy efficiency and ecological footprint, and between renewable energy and ecological footprint. The negative impact of both renewable energy and energy efficiency on the ecological footprint increases when trade openness exceeds the threshold. This suggests that, in terms of curbing environmental degradation, enhancing trade openness may further increase the negative impacts of energy efficiency and renewable energy on ecological footprint. At the same time, this confirms the positive role of trade openness in environmental protection. [Display omitted] • Exploring more effective option to combat environmental degradation. • Energy efficiency, renewable energy, natural gas can reduce ecological footprint. • Trade openness help energy efficiency, renewables lower ecological footprint. • The most effective strategy is energy efficiency, followed by renewables and natural gas. [ABSTRACT FROM AUTHOR]

This paper conducts a systematic study to address the problems of high flow loss and low energy efficiency of centrifugal pumps caused by the development of secondary flow within the impeller. Based on the forces balance in the direction perpendicular to the streamline, theoretical calculations are drawn to redesign blade thickness for a 5-blade centrifugal impeller to suppress the secondary flow. The correlations between the development of internal secondary flow within the impeller and energy efficiency of centrifugal pump under full flow rate conditions are illustrated by numerical simulations validated by experimental tests. Secondary flow coefficient and entropy production rate (EPR) are introduced and extracted to quantitative analysis the secondary flow level and energy loss inside the impeller. Results indicate that the blade redesign methods proposed here can efficiently inhibit the development of secondary flow and improve the energy efficiency. Moreover, the secondary flow coefficient introduced in this paper can quantitatively reflect the intensity of secondary flow under various flow rates of different impellers. Combining with the entropy production analysis of impeller, the consistent change trend of total secondary flow coefficient and entropy production reveals that the improvement of pump energy efficiency benefits from the reduction of turbulence EPR which results from the suppression of internal secondary flow. • Theoretical calculations of blade thickness for low specific speed centrifugal pump. • Blade redesign based on secondary flow suppression to improve energy efficiency. • Quantitative analysis of secondary flow and energy losses in the impeller. • Improvement of energy efficiency attributes to the reduction of turbulence EPR. [ABSTRACT FROM AUTHOR]

Abstract: There is currently a lack of harmonization in the building energy efficiency requirements that are mandated by different countries. Energy efficiency is defined by the energy yield of the facilities and by the envelope energy losses. These energy losses are mainly conditioned by the thermal envelope transmittance, the compactness factor, and the indoor temperature. This paper compares the requirements imposed on these three energy factors in residential buildings by various countries of the European Union (Germany, France, the UK, and Spain) and the United States of America. The paper also discusses the causes of the divergences in the requirements and their degrees of disparity. The paper further compares the requirements of the Passivhaus construction standard, which is highlighted by the European Union as an example of residential buildings with virtually zero energy consumption (nearly zero-energy buildings), similarly to the buildings that European countries will be forced to build by 2020. Within the current regulations, the thermal transmittance is the only factor that is used to compare the thermal insulation of buildings. However, this paper demonstrates that the thermal transmittance is not a valid parameter for the comparison and harmonization of the envelope energy losses because countries set different transmittance values for each climate zone, which are defined on the basis of different ranges of degree-day variation and are calculated using different base temperatures. Furthermore, this paper proposes a new methodology that can be used to regulate the thermal insulation of buildings to ultimately harmonize the envelope energy losses across all countries. [Copyright &y& Elsevier]

Abstract: Thermal energy loss in the process industry is a significant issue due to the high temperatures and multiple heat intensive processes involved. High-grade thermal energy is typically recovered within processes. However, lower grade heat is often rejected to the environment. The benefits of capturing and utilising low grade thermal energy are highly dependent on the qualities and properties of the heat in the waste streams. The temperature of the low grade heat stream is the most important parameter, as the effective use of the residual heat or the efficiency of energy recovery from the low grade heat sources will mainly depend on the temperature difference between the source and a suitable sink, e.g. another process or space heating/cooling. In general, the temperatures of these waste heat sources are too low to produce electricity and direct heat use will depend on whether potential user can be found. This paper presents past and current drivers for heat recovery studies. High and low grade heat sources are defined according to the viability of recovery within the processes. Firstly, high grade heat capture within the processes is reviewed. Then, the focus is on the potential for low grade heat capture outside of the original plant. The paper addresses the potential for low grade heat recovery with regard to new incentives and technological advances. Finally, different aspects which influence the decision making for low grade heat recovery in the process industry are discussed. It is concluded that organisational, financial and economic barriers might be overcome and benefits from a holistic vision could be gained with stronger governmental policy and regulation incentives. [Copyright &y& Elsevier]

High-powered, medium-speed diesel engines are widely used in merchant ships. Improving energy efficiency by using energy rationally is critical to reducing both environmental pollution and transport charges. In this paper, the energy efficiency of marine high-powered, medium-speed diesel engine is investigated. A new thermal cycle model of the marine engine is developed using AVL-Boost software. The thermodynamic data of the engine thermal cycle are obtained from the AVL-Boost software. The energy efficiency of the marine diesel engine is evaluated using both energy balance and exergy analysis. From the energy balance analysis, about 25% of the total energy is lost through exhaust heat. This forms the largest energy loss. However, using exergy analysis the largest energy loss originates from the irreversible exergy loss produced during the combustion process. This represents about 36% of the total energy loss. To explore ways to reduce energy loss and improve the energy efficiency, the effects of critical combustion parameters in the thermal cycle (combustion quality index, combustion starting angle and combustion duration angle) on energy distributions are discussed. The decrease in the combustion quality index, combustion starting angle and combustion duration angle (within a reasonable range) all contribute to reduce the total energy loss, increasing the indicated work and improving energy efficiency. • Evaluation of energy efficiency of high-powered medium-speed marine diesel engine by both energy balance and exergy analysis. • Model of diesel engine thermodynamic cycle is developed. • Effects of combustion parameters on energy loss are investigated to improve the energy efficiency. [ABSTRACT FROM AUTHOR]

Abstract Constraint networks consist of a large number of nodes, where each node is limited by its resources like memory, bandwidth, and energy. Most of the applications being developed in such networks are meant for critical a service which requires high computation leading to power dissipation and energy consumption. In such constraint networks, energy consumption is a significant cost factor for computing resources. Hence, there is a need for design and development of an efficient mechanism for optimal utilization of energy. This paper proposes a Software Defined Networking based resource reservation mechanism for optimal utilization of energy by reducing the energy consumption of each node thereby reducing the overall energy consumption of the system. Results of the proposed work have proven the reduced energy consumption and hence increasing the system performance. [ABSTRACT FROM AUTHOR]

Water Distribution Networks (WDNs) represent a major investment for water supply systems development. The standard procedure for their design is to search for the minimum cost, which is produced by the smaller diameters capable of maintaining the minimum required pressure. However, some District Metered Areas (DMAs) have a significant topographic elevation difference, and even if the minimum diameters are reached, the pressure remains high, and a Pressure Reducing Valve (PRV) is necessary. However, if the pipe diameters of the network are increased, distributed headloss will be reduced, and this additional energy will be locally dissipated in PRVs to maintain the pressure in the DMA below the maximum allowed value. If a turbine is installed instead, the dissipated energy can be used, creating a benefit that can justify the additional investment due to the diameter increment. Therefore, this paper presents a method for the optimal design of a WDN considering energy recovery. The use of Pumps as Turbines (PATs) is considered for energy production. The optimal design is obtained using a two-level optimization procedure: the first is used to obtain pipe diameters, and the second is used for PAT selection. Particle Swarm Optimization is used, and two case studies are presented. [ABSTRACT FROM AUTHOR]

Plasma technology is gaining increasing interest for CO 2 conversion, but to maximize the energy efficiency, it is important to track the different energy transfers taking place in the plasma. In this paper, we study these mechanisms by a 0D chemical kinetics model, including the vibrational kinetics, for different conditions of reduced electric field, gas temperature and ionization degree, at a pressure of 100 mbar. Our model predicts a maximum conversion and energy efficiency of 32% and 47%, respectively, at conditions that are particularly beneficial for energy efficient CO 2 conversion, i.e. a low reduced electric field (10 Td) and a low gas temperature (300 K). We study the effect of the efficiency by which the vibrational energy is used to dissociate CO 2 , as well as of the activation energy of the reaction CO 2  + O → CO + O 2 , to elucidate the theoretical limitations to the energy efficiency. Our model reveals that these parameters are mainly responsible for the limitations in the energy efficiency. By varying these parameters, we can reach a maximum conversion and energy efficiency of 86%. Finally, we derive an empirical formula to estimate the maximum possible energy efficiency that can be reached under the assumptions of the model. [ABSTRACT FROM AUTHOR]

Battery equalization is a critical technology in energy storage systems, so that each storage cell has equal state. In the application of electric vehicle, equalization circuits and algorithms have been widely studied for the purpose of prolonging driving time, but optimization of equalization efficiency is a difficult task in the battery equalization of electric vehicle. In this paper, an optimization model with a linear form is proposed to incorporate both energy loss and equalization time for an energy-bus equalizer. In the consideration of different working status of electric vehicle, i.e., charging, discharging, and driving, dynamic equalization has been investigated, and a model predictive control approach is proposed to cope with frequent change of working status. According to simulation and experimental results, it can be concluded that energy and time efficiency can be significantly improved during dynamic battery equalization, and that the proposed equalization system is easily implemented with competitive simplicity due to the linearized system model. [ABSTRACT FROM AUTHOR]

Pressure control is a fundamental component of safe operation of water supply systems, mainly to reduce leakage, risk of disruption, and maintenance costs. System topology and topography can define high-pressure zones, and the use of Pressure Reducing Valves (PRVs) to maintain standard pressures in these zones is common. However, all energy available in the fluid is dissipated trough headloss. A turbine could be used instead of PRVs to produce electrical energy and to control pressure. The use of Pumps as Turbines (PATs) is recommended to reduce investment cost. Due to dynamic operations throughout the day, PATs operate under varying conditions of flow and head. This variation affects efficiency and headloss, which makes difficult the selection of PATs to substitute PRVs through conventional methods; therefore, this paper proposes a method for such selection. The method is based on maximization of energy produced, restricted to the system pressure limits. To solve this selection problem, the optimization technique of Particle Swarm Optimization (PSO) is used, and complete pump curves are used to simulate the PATs. In addition, this method is capable of identifying the best location on the network to install the PATs. [ABSTRACT FROM AUTHOR]

Major factors affecting efficiency of plasma synthetic jet actuator (PSJA) are analyzed based on a new discharge model in the present paper. The model couples the magnetohydrodynamics (MHD) equations with the resistor–inductor–capacitor (RLC) equations, and is able to resolve the time-dependent voltage fall on the sheath region and arc region, which is critical in analyzing energy loss in the heating process. This model is integrated into the commercial CFD software by a two-equation method. Results show that in a typical capacitive discharge at microsecond scale, the maximum energy loss is the sheath energy loss, which accounts for nearly half of the discharge energy, while the radiation loss is less than 5%. The discharge time is an important parameter for the PSJA efficiency. A short discharge time less than 1 μs will effectively reduce the sheath energy loss, while a longer discharge time will decrease the thermodynamic efficiency. [ABSTRACT FROM AUTHOR]

The contents of this paper address the concept of net zero energy in industrial and commercial buildings, focusing on the definition which accounts for energy losses by converting each energy carrier used in the building to source energy. Therefore, this paper presents a sample of several source energy conversion factors commonly used in the United States, Canada and in most European countries. Energy efficiency in industrial and commercial buildings is discussed throughout the work, including a brief review of energy-efficiency measures which can be implemented in order to increase the efficiency and improve the performance of these energy-intensive buildings. Net metering is introduced due to its importance towards achieving net zero energy, along with its potential benefits and challenges, as well as a brief overview of policies currently being implemented around the world. In addition, various aspects regarding the classification of the weighting system and calculation of zero energy balance are also addressed. Finally, a case study is presented to evaluate whether five distinct enterprises located in Portugal can achieve annual net zero energy by deploying on-site renewable sources in the area available within their site boundary. This case study is based on a developed algorithm which allows the evaluation of these enterprises according to different symmetric and asymmetric weighting systems. The concepts of demand response and net metering are also briefly discussed and presented as a viable and cost-effective solution to aid any building achieving annual net zero energy. • Energy efficiency is mandatory to achieve net zero energy in industrial buildings. • Several process specific measures can be adopted in each industrial sector. • Source energy conversion factors are presented to assist the balance calculation. • The choice of weighting factors heavily influences the building energy balance. • Asymmetric weights favouring generation are suitable for net zero-energy buildings. [ABSTRACT FROM AUTHOR]

Concerns regarding the environment have forced manufacturing organisations not only to aim for operational excellence but also to rethink how their operations and processes can become more environmentally sustainable. Companies need to decrease their unnecessary energy consumption while maintaining their productivity. Lean manufacturing is considered as one of the most influential energy management initiatives, since it increases the effective use of resources by identifying and eliminating losses. In this paper, a novel lean method called Energy Cost Deployment (ECD) is presented, whose objective are to classify, analyse, and eliminate energy losses within the factory. Modifying the well-known Manufacturing cost deployment, the novel ECD uses five matrices, which are built in sequence from the first one (i.e., A-matrix) to the last (i.e., E-matrix), in order to classify and analyse the causal factor of losses related to energy, with the focus on reducing and eliminating the greatest causal losses, and thus providing opportunities for greater efficiency. Each causal loss is quantified in monetary terms. Improvement techniques that deal with each causal loss are identified and then evaluated by means of a quantitative measure in order to find the preferable approaches. Finally, a practical decision procedure is used to select which improvement projects should be started, and hence which causal losses to tackle should be tackled, according to technical and economic factors. The effectiveness and practicality of the ECD method in tackling energy losses are illustrated using an industrial case study concerning a tissue-paper mill. Thanks to its structured step-by-step procedure, the ECD method improves the energy efficiency within a factory. • Energy Cost Deployment (ECD) is a novel Lean approach able to tackling energy losses. • The ECD method permits to improve the energy efficiency of the factory. • A novel structure to classify and analyse the energy losses is presented. • Corrective actions are prioritized according to technical and economic factors. • A case study is presented to show the practicality and effectiveness of the method. [ABSTRACT FROM AUTHOR]

Flotation is not a particularly energy intensive process. Therefore, flotation optimization has traditionally been focused on grade and recovery performance improvements. However, with the growing need for energy efficiency and the dramatic increase in flotation cell size in recent years it is worth considering how well energy is utilised within flotation cells. In conventional flotation cells a certain amount of energy is required to meet the basic requirements for flotation (air dispersion, solids suspension and particle-bubble collision). This paper investigates how that energy is dissipated in the flotation cell to determine the most efficient use of the imparted energy. The distribution of turbulence and its effect on flotation kinetics are investigated in a mechanical 3 m 3 flotation cell for a range of hydrodynamic conditions. The effect of the different conditions are evaluated considering the Power Number (N P ); a dimensionless number that is a useful hydrodynamic indicator as it represents the ratio of energy added to the flotation cell dissipated as shear to that used to generate bulk flow. Results show that flotation rate in the collection zone and the fraction of the cell with higher turbulence increases as more of the power drawn by the impeller is dissipated as shear in the impeller-stator region (higher Power Number). This should promote higher collision rates and more efficient use of the energy imparted in the flotation cell. [ABSTRACT FROM AUTHOR]

This paper presents a study on the characterization of the performance of a water-to-water heat pump of 40.5 kW fixed heating capacity under different cycling conditions scenarios. Semi-virtual laboratory experiments were conducted to analyse the influence of inertia from 1.23 to 24.7 L/kW on the efficiency of the heat pump operating at partial load. Different parameterizations in standards were compared to assess their ability to predict the energy efficiency degradation caused by cycling. Performance deterioration at part load was found to be highly dependent on inertia conditions, with non-negligible start-up parasitic effects detected for the heat pump under study, particularly for decreasing inertia. Results suggest that current standards for characterising the performance of systems at partial load, such as the European EN14825, should be reviewed to account for the influence of inertia on equipment performance and for the potential occurrence of start-up efficiency losses for water-to-water heat pumps. An expression is derived in this study for the start-up losses degradation coefficient C d and a single parameterization accounting for different sources of efficiency losses is proposed, together with a simple method to determine degradation coefficients from reduced experimentation. [ABSTRACT FROM AUTHOR]

The paper presents the analysis of some potentially suitable actions for reducing the energy losses of an islanded Medium Voltage distribution network, with the aim of improving electricity distribution efficiency. For this purpose, four actions are considered: 1) increasing the network's rated voltage; 2) reactive power compensation through static capacitor banks; 3) reactive power compensation through switchable capacitor banks; 4) installation of distributed photovoltaic (PV) generation. The first two measures are typically taken into account by the distribution system operators and can be examined by means of classical design methods, whereas the latter two more innovative actions are tested here using specialized software based on the NSGA-II multi-objective optimization algorithm. The fourth action, expanding distributed PV generation, can be motivated through public or private incentives. It is investigated here using an innovative approach to the optimization problem formulation considering the perspectives of both the utility and the consumer. A case study on a small Mediterranean island real existing network is also presented. [ABSTRACT FROM AUTHOR]

The present paper introduces new pipe-level energy metrics to evaluate the energy transformations in the individual pipes of water distribution systems. To evaluate these metrics, energy supplied to each pipe is categorized into delivered and required energy, leakage, friction and surplus energy and then compared to each other. The results of the pipe-level energy assessment of the two systems imply that the energy performance of pipes can vary considerably across a distribution system. Also, the proximity of pipes to major components (e.g., pumps and tanks) and pipe flow rates can have a large impact on the energy efficiency of pipes. [ABSTRACT FROM AUTHOR]

In energy constrained wireless sensor networks, maximizing network coverage lifetime while ensuring optimized coverage is important. The challenge is to determine an appropriate duty cycle for the nodes while maintaining sufficient count of active nodes for optimal network coverage. Most of the existing work, for coverage optimization based on duty cycle, does not consider the residual energy of the active nodes. This can result in suboptimal wake-up of sleeping nodes. RBSP considers the residual energy but ignores the active nodes’ battery discharge rate. In this paper, we propose DCBSP ( Discharge Curve Backo ff Sleep Protocol ), which considers the battery discharge curve of the active nodes to determine the duty cycle of the inactive nodes. Thus in DCBSP, inactive nodes wake-up close to death of the active nodes which leads to lesser energy consumption and increased network lifetime. NS-2 simulations show the energy consumption of DCBSP is lesser than that of PEAS by 39% and lesser by 25% and 15% as compared to RBSP and PECAS respectively. Further, the coverage ratio of DCBSP is higher than PEAS by 32% and higher by 17% and 6% as compared to RBSP, PECAS respectively. Hence, DCBSP is effective in ensuring higher coverage while extending the network lifetime. [ABSTRACT FROM AUTHOR]

• Seismic safety and environmental sustainability need to be considered simultaneously. • A probabilistic risk assessment is proposed to support building investment decisions. • Integrated seismic and energy economic losses are used as design decision variable. • Traditional vs low-damage seismic-resisting technologies are investigated. • Design solutions are assessed and compared in terms of reliability and risk values. Structural safety and environmental sustainability are major factors in investment decisions for building systems, but are rarely considered simultaneously. Recent research efforts have redressed this by developing assessment methodologies and technical solutions for integrated energy efficiency and seismic performance. These studies are typically limited to existing buildings and retrofit interventions at global building scale, whereas an effective framework could and should be part of the design process of either new or existing buildings at both building and component scales. This paper proposes a probabilistic-based assessment framework to assess the building performance in terms of integrated economic losses and support the selection of resilience-enhanced solutions. The proposed methodology is validated through its application to reinforced concrete case-study buildings consisting of traditional vs low-damage earthquake-resistant technologies coupled with energy efficiency strategies. Seismic and energy risk assessment analyses are performed accounting for both modelling uncertainties and earthquake/weather variability. Probabilistic distributions of the integrated economic losses are finally derived to compare the design solutions in terms of risk and reliability. The research outcomes demonstrate the effectiveness of the probabilistic approach for decision-making in building projects. Specifically, it is found that the economic losses can be highly underestimated (greater than40 %) in the single domains (energy or seismic); greater savings and return on investment can be achieved when the seismic safety is involved in the design process; probabilistic distributions and reliability/risk values can represent an effective tool to assess and compare design solutions. [ABSTRACT FROM AUTHOR]

Abstract: We can get an (energy efficiency) EE improvement if we produce a flatter daily load curve, leading to a higher efficiency of the power system, making better use of the generation and transport electricity chain, thus avoiding over-investment in equipment used just few hours a year. Tariff flexibility of the (Time of Use) TOU type is one of these measures. Generally, TOU systems are designed to minimize total system cost, which may cause losses in distribution companies (DISCOs), generating opposition. On the contrary, the present paper proposes a TOU system for electricity consumption in Chile where optimal prices are obtained in order to maximize total income of DISCOs. In this manner, the proposed TOU system is, by definition, beneficial for DISCOs and it may lead to a win–win situation among DISCOs and consumers. In particular, we show that such a system, implemented in a country like Chile, would allow for DISCOs a total potential benefit of 811.7 millions of dollars for the 3-year study period (2005–2007), considering initiatives that promote a 5% savings in real consumption during on-peak hours, obtained by the spread or difference between the proposed and the current systems. [Copyright &y& Elsevier]

Abstract: Improving the heating performance of district heating networks (DHNs), one of the most important components in district heating systems, has significant influence on the promotion of energy efficiency. Based on the entransy theory, this paper develops an entransy dissipation-based method for global optimization of DHNs. We analyze the irreversibility of three types of heat transfer processes in DHNs: (1) the heat transfer process between the waters in primary heating networks and DHNs in substation heat exchangers; (2) the heat transfer process between supply water and indoor airs in radiators; and (3) the return water mixing process, then derive the expressions of entransy dissipation for each process, and finally deduce two different formulas of the total entransy dissipation in DHNs by the users’ demands and the structural and operating parameters of DHNs, respectively, from which we establish the mathematical relation between the users’ demands and the structural and operating parameters of DHNs. Based on this relation, two typical optimization problems of DHNs are converted into conditional extremum problems to deduce two optimization equation groups. Solving the equation groups gives the optimal structural and operating parameters for DHNs with highest energy efficiency. Finally, the method is proved valid and advantageous through the optimization for both 1-column-2-user and 2-column-4-user DHNs. [Copyright &y& Elsevier]

Abstract: This paper is presented to investigate operational characteristics of a direct methanol fuel cell (DMFC) stack with regard to fuel and energy efficiency, including its performance and stability under various operating conditions. Fuel efficiency of the DMFC stack is strongly dependent on fuel concentration, working temperature, current density, and anode channel configuration in the bipolar plates and noticeably increases due to the reduced methanol crossover through the membrane, as the current density increases and the methanol concentration, anode channel depth, and temperature decreases. It is, however, revealed that the energy efficiency of the DMFC stack is not always improved with increased fuel efficiency, since the reduced methanol crossover does not always indicate an increase in the power of the DMFC stack. Further, a lower methanol concentration and temperature sacrifice the power and operational stability of the stack with the large difference of cell voltages, even though the stack shows more than 90% of fuel efficiency in this operating condition. The energy efficiency is therefore a more important characteristic to find optimal operating conditions in the DMFC stack than fuel efficiency based on the methanol utilization and crossover, since it considers both fuel efficiency and cell electrical power. These efforts may contribute to commercialization of the highly efficient DMFC system, through reduction of the loss of energy and fuel. [Copyright &y& Elsevier]

Abstract: The recently developed entransy theory is introduced in this paper to tackle the heat transfer processes in building central chilled water systems so as to improve their energy efficiency. We first divide the irreversible heat transfer processes into four categories: (1) air mixing processes; (2) heat transfer processes between chilled water and air; (3) chilled water mixing processes; and (4) heat transfer processes between chilled water and refrigerant. The formulas of entransy dissipation rates for each irreversible process are derived, and then the total entransy dissipation rate in the whole chilled water systems is obtained, which connects the geometrical structures of each heat exchanger and the operating parameters of each fluid directly to the demands of users and the supply of refrigerating unit. Based on the formula of entransy dissipation rate together with the conditional extremum method in mathematics, two optimization equation groups are deduced theoretically. Simultaneously solving such equation groups will easily find the optimal central chilled water system with the highest energy efficiency. Finally, a simple building central chilled water system with two users is taken as an example to illustrate the applications of the newly proposed optimization principle. [Copyright &y& Elsevier]

Abstract: In wireless sensor networks (WSNs), hierarchical network structures have the advantage of providing scalable and resource efficient solutions. To find an efficient way to generate clusters, this paper adapts the well-understood hierarchical agglomerative clustering (HAC) algorithm by proposing a distributed HAC (DHAC) algorithm. With simple six-step clustering, DHAC provides a bottom-up clustering approach by grouping similar nodes together before the cluster head (CH) is selected. DHAC can accommodate both quantitative and qualitative information types in clustering, while offering flexible combinations using four commonly used HAC algorithm methods, SLINK, CLINK, UPGMA, and WPGMA. With automatic CH rotation and re-scheduling, DHAC avoids reclustering and achieves uniform energy dissipation through the whole network. Simulation results in the NS-2 platform demonstrate the longer network lifetime of the DHAC than the better-known clustering protocols, LEACH and LEACH-C. [Copyright &y& Elsevier]

Abstract: Minimizing energy dissipation and maximizing network lifetime are among the central concerns when designing applications and protocols for sensor networks. Clustering has been proven to be energy-efficient in sensor networks since data routing and relaying are only operated by cluster heads. Besides, cluster heads can process, filter and aggregate data sent by cluster members, thus reducing network load and alleviating the bandwidth. In this paper, we propose a novel distributed clustering algorithm where cluster heads are elected following a three-way message exchange between each sensor and its neighbors. Sensor’s eligibility to be elected cluster head is based on its residual energy and its degree. Our protocol has a message exchange complexity of and a worst-case convergence time complexity of . Simulations show that our algorithm outperforms EESH, one of the most recently published distributed clustering algorithms, in terms of network lifetime and ratio of elected cluster heads. [Copyright &y& Elsevier]

Abstract: The red ceramic industry in Brazil, consisting of over 7000 companies, requires large amounts of thermal energy, currently being met mainly by native fuelwood, which causes serious deforestation and soil erosion problems. The use of firewood does not allow achieving good energy performance in industrial ceramic kilns, causing high energy losses, low productivity and low quality products (bricks and roof tiles). Thus, to implement higher added value products, besides mitigate environmental problems caused by deforestation, the use of natural gas by the sector seems to be a promising alternative. Brazil’s natural gas market has grown at a fast pace in recent years. Its share in the country’s primary energy consumption increased from 3.7% to 9.3% between 1998 and 2007, compared to almost 21% in the world. The development of the Brazilian natural gas industry was grounded on stepping up supplies through integration with Bolivia from where natural gas is imported, together with fiscal incentives for promoting the demand. This paper estimates that the natural gas market that could be developed in the Brazilian red ceramic industry corresponds to less than 5% of the total industrial natural gas consumption, meaning that a major technological transformation of the country’s red ceramic industry will not severely affect the natural gas market equilibrium, contributing to reduce the country’s high rates of deforestation. [Copyright &y& Elsevier]

Low-temperature combustion in homogeneous charge compression ignition (HCCI) engine is one of the most promising technologies allowing to meet future emission targets for internal combustion engines. Whereas majority of research is centred on combustion itself, this paper for the first time points out the piston's energy losses induced by friction and blow-by in HCCI engine with negative valve overlap. The energy losses for HCCI and spark ignition (SI) operating modes were compared and thoroughly analysed with the use of the ring pack model. The input data for the simulations came from measurements made on a single-cylinder research engine capable of dual-mode combustion. The energy losses associated with friction of the rings against the cylinder varied from 8.2% of the indicated energy at the lowest load to 2.2% at the highest load tested, and were higher than in the SI mode by approximately 7%. The losses due to the gas leakage through the ring pack in the HCCI mode varied from 8% to 3.3%, respectively, and these losses were about twice as high as in the SI engine. The results demonstrated that energy losses due to blow-by are comparable with the friction losses of the rings, which are usually regarded as the prime source of inefficiency. • HCCI cycle effect on the ring pack energy losses is demonstrated. • Negative valve overlap in HCCI engine highly affects the ring pack performance. • The energy losses due to blow-by in an HCCI mode are 100% higher than in an SI mode. • The energy losses due to friction of the rings are higher by 7% in an HCCI engine. • The energy losses related to blow-by and rings' friction are comparable. [ABSTRACT FROM AUTHOR]

This paper examines the asymmetric long-run and short-run impacts of energy efficiency on carbon emissions for 28 developed and 34 developing economies, covering the period 1990–2017. The asymmetries are investigated by employing a nonlinear panel autoregressive distributed lag modelling framework. The analysis accounts for nonlinear complexities in energy relations and heterogeneity between developed and developing economies. The asymmetric long-run impacts of energy efficiency on carbon emissions are evident for developed and developing economies, but the effects are heterogeneous. In the long-run, a 1% increase in positive shocks (in energy efficiency) leads to a fall in carbon emissions by 1.24% and 1.19% for developed and developing economies, respectively. A similar rise in negative shocks (in energy efficiency) leads to an increase in carbon emissions by 0.37% and 1.06% for developed and developing economies, respectively. The short-run impacts are observed to be symmetric for both developed and developing economies. These results imply that the broader benefits of energy efficiency, like employment and energy productivity, should be considered in energy efficiency policy assessment. The developing economies should create a strong substitution effect between energy and other inputs to compensate for energy efficiency losses. [Display omitted] • Asymmetric impacts of energy efficiency on carbon emissions are examined. • Data covers 28 developed economies and 34 developing economies over the period 1990–2017. • A nonlinear panel autoregressive distributed lag model is employed. • Asymmetric long-run impacts are evident for developed and developing economies. • Symmetric short-run impacts exist for developed and developing economies. [ABSTRACT FROM AUTHOR]

Integrating energy efficiency as a key criterion in production management is critical to increasing energy efficiency while maintaining productivity in manufacturing systems. However, this integration still poses a huge challenge for decision-makers due to a lack of knowledge about the linkage between energy efficiency and productivity. Consequently, related energy-saving potential remains unexploited. In this context, this paper presents an innovative Energy Value Mapping (EVM) method to promote the systematic integration of energy efficiency into production management. The method includes three consecutive phases: (i) energy loss modeling to reveal the coupling relation between energy losses and productivity variables; (ii) lean energy analysis using production-oriented energy performance indicators to highlight energy inefficiencies and indicate improvement directions; (iii) improvement strategies determination to improve energy efficiency simultaneously considering traditional production management decisions. Furthermore, an industrial case study of a die-casting plant has demonstrated the effeteness and practicality of the method, showing its great potential in identifying, visualizing, quantifying, analyzing, and decreasing the energy losses related to production and operations management. The results showed that the overall energy demand of the process chain could be reduced by 6.17% with the energy utilization and time utilization being increased by 5.0%, 4.8%, respectively. • A method for integrating energy efficiency into production management is proposed. • The coupling relation between energy losses and productivity variables is studied. • A set of energy performance indicators is developed to expose energy losses. • The method permits to increase energy efficiency while maintaining productivity. • Overall energy demand was reduced by 6.17% by implementing the proposed method. [ABSTRACT FROM AUTHOR]

• A multi-source hydraulic architecture is presented for high energy efficiency. • The power management of this system can reduce power consumption. • The switching supervisory controller is proposed for selecting the power modes. • Logical threshold control is designed for different power modes switching. • Experiments show that about 60% input energy can be reduced from the engine. The mismatch between the load and pump sources and the restriction of energy recovery lead to large energy losses and lower energy efficiency in high power multi-actuator hydraulic systems. To obtain high energy efficiency, this paper develops a Multi-Source Network Hydraulic System (MSNHS) with multiple actuators and a corresponding power management strategy (PMS) to reduce the throttling losses and recover energy. The multiple energy-saving power modes based on the path of power transmissions, composed of different combinations of six power units with energy conversion and transfer, are implemented on MSNHS to supply and regenerate or recover power for various load conditions. Thus, the power consumption models of each power unit are established to analyze the power consumption characteristics for itself and power modes. On this basis, the switching supervisory controller is proposed to select an optimal mode for the current condition by utilizing an objective optimized function of minimal power consumption. Besides, the switching rules among power modes are designed, and the logical threshold control is presented for the multi-mode switching under different working conditions. The combination of the switching supervisory controller of optimal mode and the logical threshold control realizes the power management of the MSNHS with multiple actuators to accommodate with time-varying load and recover potential energy. The experimental validation is conducted on the MSNHS platform by simulating a 90° truck-loading cycle of the excavator. Experimental results demonstrate that the PMS applied to the MSNHS can downsize engine input power by up to 60.27% compared with the theoretical calculation of conventional one, and then improve overall system energy efficiency. [ABSTRACT FROM AUTHOR]