Energy Efficiency Perspective Research Articles

Are shared electric scooters energy efficient?

Shared electric scooters (e-scooter) are booming across the world and widely regarded as a sustainable mobility service. An increasing number of studies have investigated the e-scooter trip patterns, safety risks, and environmental impacts, but few considered the energy efficiency of e-scooters. In this research, we collected the operational data of e-scooters from a major provider in Gothenburg to shed light on the energy efficiency performance of e-scooters in real cases. We first develop a multiple logarithmic regression model to examine the energy consumption of single trips and influencing factors. With the regression model, a Monte Carlo simulation framework is proposed to estimate the fleet energy consumption in various scenarios, taking into account both trip-related energy usage and energy loss in idle status. The results indicate that 40% of e-scooter battery energy was wasted in idle status in the current practice, mainly due to the relatively low usage rate (0.83) of e-scooters. If the average usage rate drops below 0.5, the wasted energy could reach up to 53%. In the end, we present a field example to showcase how to optimally integrate public transport with e-scooters from the perspective of energy efficiency. We hope the findings of this study could help understand and resolve the current and future challenges regarding the ever-growing e-scooter services.

Parametric Energy Simulation Methods for Solar-NIR Selective Glazing Systems

Solar near-infrared (NIR) selective glazing systems have been proposed by incorporating photothermal effects (PTE) of a nanoparticle film into building windows. From an energy efficiency perspective, the nanoscale PTE forms unique inward-flowing heat by heating up the window interior surface temperature under solar near-infrared, significantly improving the window thermal performance. Also, the PTE-driven solar heat gains are dynamic upon solar radiation and weather conditions. However, the PTE on annual building energy use has not been investigated thoroughly, due to the lack of an accurate and appropriate energy simulation method. In this study, we used the EnergyPlus energy management system to develop a parametric energy model and simulation approach in which a solar-temperature-dependent thermal model was embedded into the parametric energy simulation workflow. Applying this method, we examined the solar near-infrared-dependent PTE-induced thermal performances of glazing systems and their effects on annual heating energy use in representative cold climates (i.e., Zones 4, 5, and 6). The results show that the dynamic model considering the PTE demonstrated more heating energy savings, up to 11.64% in cold climates, as opposed to the baseline model that ignored the PTE. This work presents a method to model and simulate the dynamic thermal performance of windows with PTE.

Guest Editorial: AI and 6G Convergence: An Energy Efficiency Perspective

Nowadays, researchers have started to conceptualize 6G with the vision of connecting everything, transmission over millimeter-wave (mmWave) and THz, and integrating sensing, communication, computation, and control functionalities. The resultant technical and network complexity puts considerable pressure on energy efficiency and sustainability.

Evaluation of the Efficiency of a High Temperature Proton Exchange Membrane Water Electrolysis System

In recent years, a significant interest has been growing for the development of high temperature (HT) electrolytes for proton exchange membrane water electrolysis (PEMWE), promising a lower reversible potential and improved reaction kinetics and ionic conductivity.In this study, the energy and exergy analysis developed for PEMWE has been extended to evaluate the performance of HT-PEMWE, with the model aiming to utilise the energy in the most efficient manner and also take into account potential heat losses, which is particularly important considering that these become more pronounced with higher temperature differences.The model shows that the stack operates in autothermic mode over a considerable range of current density. Thus heating inputs to the stack and feed water become progressively unnecessary as polarization losses make up for these heating requirements. For the considered model, a current density above 1.44 A/cm2 would allow surplus heat to be utilised for secondary applications whilst not recovering any heat would result in an exergy efficiency loss of 4.2 % points. The effect of accounting for pipework and stack heat losses is most evident in the lower region of current density. This however diminishes as the losses start constituting a minor fraction of the total power share.The exergy efficiency for HT has been calculated to surpass that for low temperature (LT) at 0.54 A/cm2. This improvement is attributed to a lower electrical power input for the same production of hydrogen and the heat management strategy incorporated within the model. The maximum improvement reaches 3.8 % points at 3 A/cm2. Taking into account exergy favours higher temperature differences – a benefit which outweighs the fact that a greater quantity of thermal power is recovered in the LT system (due to higher polarization losses). This finding also shows the suitability of adopting exergy efficiency as the performance indicator for PEMWE systems.Given the novelty in opting for HT operation, this study offers further understanding on its performance and evaluates the cost borne with opting for more demanding operating conditions from the perspective of energy and exergy efficiency.

Heat Mapping, a Method for Enhancing the Sustainability of the Smart District Heat Networks

District heating (DH) has a major potential to increase the efficiency, security, and sustainability of energy management at the community scale. However, there is a huge challenge for decision makers due to the lack of knowledge about thermal energy demand during a year. Thermal energy demand is strongly dependent on the outdoor temperature, building area, and activities. In this context, this paper presents an innovative monthly thermal energy mapping method to calculate and visualize heat demand accurately for various types of buildings. The method includes three consecutive phases: (i) calculating energy loss, (ii) completing a dataset that includes energy and building information, and (iii) generating the monthly heat demand maps for the community. Determining the amount of demand and the best location for energy generators from the perspective of energy efficiency in a DH system in an urban context is one of the important applications of heat maps. Exploring heat demand characteristics and visualizing them on maps is the foundation of smart DHs.

Adaptive and Dynamic Security in AI-Empowered 6G: From an Energy Efficiency Perspective

Emerging AI-empowered services and techniques, such as connected vehicle, intelligent industry, and smart city, are forthcoming with the sixth generation (6G) cellular network to benefit daily life, industry, and society. However, the increasing integration of the 6G network with the physical world leads to a plethora of new scenarios that bring new challenges to 6G, especially from the security and energy aspects. In 5G networks, security solutions across all devices and base stations are configured with universal settings for certain types of attacks. This one-size-fit-all strategy no longer suits 6G security due to the higher diversity in device capabilities, service features, energy conditions, attack vulnerabilities, and other time-varying attributes. Since each scenario may have unique security requirements and energy availability, the selection and configuration of security strategies need to be optimized for 6G networks in an adaptive and dynamic manner. In this article, we explore 6G security from an energy efficiency perspective by balancing the tradeoff between security and energy consumption in various scenarios. Specifically, we first investigate the AI-empowered 6G network architecture with promising applications and visions. Then we identify the challenges for adaptive and dynamic security optimization in 6G from the aspects of heterogeneity, dynamics, and modeling complexity. To balance security-energy trade-off, we propose an optimization framework that provides customized recommendations of security strategy to different user devices and base stations. Finally, open issues are discussed on 6G security from an energy efficiency perspective.

Secure and Reliable Downlink Transmission for Energy-Efficient User-Centric Ultra-Dense Networks: An Accelerated DRL Approach

Due to the inherent openness of wireless channels, data transmission in user-centric ultra-dense networks (UUDNs) is vulnerable to eavesdropping and malicious jamming attacks (EJA). This paper addresses the user-centric clustering, beamforming, and artificial noise design to combat with the EJA, and an accelerated deep reinforcement learning (DRL) based approach has been proposed for the downlink of UUDNs from a security, reliability and energy efficiency (SREE) perspective. In contrast to the existing approaches, the proposed approach divides the UE's communication behavior into association phase and transmission phase to perform a fast and adaptive response to the EJA. For the association phase, the proposed approach aims at achieving a fast response to EJA by optimization algorithms from a short-term perspective. For the transmission phase, we propose a DRL based algorithm to achieve optimal adaptive response by dealing with the dynamic and persistent effects of EJA from a long-term perspective. To accelerate the training process, fast response achieved in the association phase will be regarded as the initial experience to update the parameters of the deep neural networks adopted by the DRL based algorithm for transmission phase. Comparing with the existing methods, simulation results show that our proposed accelerated DRL approach achieves better performance in terms of SREE and convergence speed.

High-speed nanoLEDs for chip-scale communication

Fast and efficient light generation and transport are at the heart of modern on-chip optical communication and information processing technologies. Next generation on-chip light sources must have a high modulation bandwidth and low energy consumption while maintaining a small footprint to be competitive. Enabled by metal-cladded nanocavities, fast subwavelength light emitters in the form of both lasers and LEDs have been analytically or experimentally demonstrated. From the modulation bandwidth perspective, nanolasers are ultimately limited by gain compression at high injection currents. From the energy efficiency perspective, nanolasers are inefficient due to the required high injection current to compensate for the losses in order to reach the lasing threshold. In contrast, nanoLEDs can simultaneously have Purcell effect enhanced speed, high energy efficiency, and output power that is above the thermal noise limit. This brief review aims to bolster, in a comparative approach, rationales of why nanoLEDs are a competitive alternative to nanolasers as light sources in chip-scale optical communication systems.

The analysing energy efficiency for sailing ships in optimal travel route planning. Case study: World voyage of the training ship "Mircea"

Reducing fuel consumption is a major goal in planning a ship's voyage. In addition to reducing the operational costs of the voyage, this planning objective influences the energy efficiency of the voyage. This study presents a method for identifying the operational energy efficiency in planning a voyage route to sailboats. In this regard, in the first part of the study was developed a method for determining the Energy Efficiency Performance Indicator (EEOI) of a voyage route for sailing ships. In the second part of the study, to validate the developed method, were analyzed two voyage routes, with imposed limitations, to identify the optimal voyage route around the world for the Training ship „Mircea”. The Training ship „Mircea” is a training ship for the students of the "Mircea cel Bătrân" Naval Academy. The analysis was performed for two navigation routes, namely from East to West and from West to East, departing/arriving from the port of Constanța. The results of the analysis indicate that the route from West to East is the optimal route for Mircea's voyage around the world from the perspective of the ship's energy efficiency.

Environmental protection and energy efficiency improvement by using natural gas fuel in maritime transportation.

Emissions from vessels are a major environmental concern because of their impacts on the deterioration of the environment, especially global warming of the atmosphere. Therefore, the International Maritime Organization (IMO) concerns significant care to environmental protection through the reduction of exhaust emission and improvement of energy efficiency through technical and operational measures. Among the suggested measures from IMO, the alternative fuel such as natural gas has the priority to be used instead of fossil fuels. The present paper calculates the effect of using natural gas in a dual-fuel engine from environmental and energy efficiency perspectives. As a case study, a container ship has been investigated. The results of the analysis show that the percent of CO2, NOx, and SOx emission reduction corresponding to using a dual-fuel engine operated by natural gas instead of a diesel engine operated by heavy fuel oil is about 30.4%, 85.3%, and 97%, respectively. Moreover, it found that NOx and SOx emission rates of the dual-fuel engine comply with the IMO 2016 and 2020 limits, respectively. Furthermore, the Energy Efficiency Design Index value in the case of using dual-fuel engine is lower than the value by using diesel engine by about 30%, and this value will be 77.18%, 86.84%, and 99.27% of the required value for the first, second, and third phases, respectively, as recommended by IMO.

Energy, exergy, and hydrodynamic performance of a spiral heat exchanger: Process intensification by a nanofluid containing different particle shapes

The energy, exergy, and hydrodynamic characteristics of employing a boehmite alumina nanofluid inside a spiral heat exchanger are investigated through CFD analysis regarding five different nanoparticle shapes. The numerical simulations are performed at four different volume fractions ranging from 0 to 0.04. It is found that utilizing the nanofluid at a higher volume fraction enhances the heat exchange amount, overall heat transfer coefficient (U), and effectiveness. It is unveiled that the highest rise in the U at the constant Reynolds number (Re) is about 25.4%, while this value at the constant pumping power (W˙) is 6.35%. Additionally, concerning the thermal efficiency viewpoint, it is proposed to use the platelet-shaped nanoparticles at the constant Re. The oblate spheroid-shaped nanoparticles are suggested considering the energy efficiency perspective. Based on the second law of thermodynamics, the platelet-shaped particles demonstrate the best performance at the invariant Re, while at the constant W˙, the oblate spheroid-shaped nanoparticles are recommended. The thermal irreversibility of the nanofluid in the case of constant Re only reduces using the oblate spheroid-shaped nanoparticles. The smallest exergy destruction in the case of constant Ẇ belongs to the blade-shaped nanoparticles.

Role of Clustering, Routing Protocols, MAC protocols and Load Balancing in Wireless Sensor Networks: An Energy-Efficiency Perspective

Abstract Wireless networks play an important role in science, including medicine, agriculture, the military, geography, and so on. The main issue with a network of wireless sensors is how to manage resource utilization to extend its lifetime. This paper investigates the various aspects of increased energy usage that may improve network life. Variables related to energy consumption and various performance metrics are investigated in terms of energy efficiency. To investigate how the network’s energy usage can be managed, a quick overview of clustering protocols, routing protocols, MAC protocols, and load balancing protocols is conducted. This paper can provide researchers with an idea of the various parameters that influence energy consumption and what methodologies could be adapted by each parameter to conserve energy, thereby extending the network’s lifetime.

Device-Level Parallel-in-Time Simulation of MMC-Based Energy System for Electric Vehicles

The device-level electromagnetic transient (EMT) simulation with the nonlinear behaviour model (NBM) of insulated-gate bipolar transistors (IGBTs) and diodes can provide an accurate insight into the power converters from the perspective of thermal performance and energy efficiency. However, device-level simulation is rarely implemented in electric vehicles (EVs) due to its extreme computation complexity natively introduced by the device models. To solve this problem, an interpolation strategy is designed based on the parallel-in-time algorithm for the device-level simulation of the modular multilevel converter (MMC) connected with the induction machine in EV applications. The MMC is mathematically separated as multiple submodules with the same attributes, which can be processed in a parallel manner in the graphics processing unit (GPU). By implementing the device-level simulation in the different time-step in GPU, the interpolation strategy provides the precise initial values for the nonlinear solution process iteratively. The accuracy of the proposed simulation scheme is validated by commercial simulation tools at the device level. In addition, the system-level simulation of EVs is carried out at different driving cycles, and the results demonstrate a significant reduction in simulation time.

Highly energy-efficient degradation of antibiotics in soil: Extensive cold plasma discharges generation in soil pores driven by high voltage nanopulses

Cold atmospheric plasma (CAP) is a green and promising soil remediation approach with significant advantages in terms of energy consumption, removal efficiency and treatment time. The most critical factor for exploiting CAP is the accomplishment of very low remediation cost, while in parallel, the limited penetration of plasma species at soil layers holds back its wider implementation. In this study, we developed a novel dielectric barrier discharge plasma reactor driven by high voltage nanosecond pulses (NSP) able to generate micro-discharges within the interconnected soil pores facilitating the effective transport of reactive species within soil layers. Key-role parameters were investigated such as pulse voltage and pulse frequency, soil thickness and air flow rate. The effectiveness of the method was identified against different types of soil (sandy soil and loam soil), both under high and low ciprofloxacin concentration in soil, while soil moisture impact on degradation efficiency was also explored. An energy efficiency of 21.2 mg of pollutant/kJ was accomplished, which is the highest ever reported for CAP-based soil remediation. The most stable intermediate degradants of ciprofloxacin, and the associated degradation pathways were identified in a kinetic point of view, while the elimination of the toxic intermediates after treatment was ensured. The present effort provides a new highly energy efficient perspective for future development of a CAP-based soil remediation technology as it maximizes the transfer and penetration of plasma species in soil layers under very low estimated remediation cost (~0.4-1.2 €/tn of soil).

Energy-efficient resource allocation optimization algorithm in industrial IoTs scenarios based on energy harvesting

Due to the rapid development of the mobile Internet and the Internet of Things (IoTs), the requirements of users and enterprises for data transmission have increased exponentially. Non-orthogonal multiple access technology can improve the spectrum efficiency of the system, but it also brings huge energy consumption. This paper studies the resource allocation of non-orthogonal multiple access systems from the perspective of energy efficiency. For the multi-carrier downlink NOMA communication scenario, the circuit energy consumption model related to the transmission rate is considered. Based on the GPE energy efficiency criterion that helps reduce the complexity of channel estimation, the joint optimization algorithm of channel resources and power resources is studied. By establishing a bilateral matching model between users and sub-channels, a low-complexity channel resource allocation algorithm based on centralized scheduling is proposed. In order to avoid the phenomenon that the data transmission quality is seriously degraded due to the energy saving of the system, the limitation of user service quality requirements is also added to the established optimization problem. The algorithm performance simulation experiment shows that the algorithm in this paper has higher average energy efficiency of the system compared with the non-cooperative centralized scheduling and the distributed RB allocation algorithm.

Determining a Return on Investment for Cybersecurity Technologies in Networked Critical Infrastructures

Much of modern life is dependent on networked critical infrastructure systems—many known to be susceptible to cyberattacks—such as the electrical grid, water purification, and transportation systems. The consequences of a successful cyberattack on these systems could be catastrophic. Appropriate levels and strategies for cybersecurity investment for networked critical infrastructures present a serious challenge that administering organizations, whether public or private, must overcome in order to provide resilient services. This challenge includes understanding the actual vulnerabilities of an organization's networked systems, as well as the cost of a successful cyberattack on those systems. On top of this, an organization's cybersecurity acquisition workforce must be able to discern reality from the marketing hype that is produced by cybersecurity sales forces. Many product offerings from industry promise to secure critical infrastructures, but there is no good method for determining which product (or combination of products) is most effective for a specific environment or scenario. This paper presents a return on cybersecurity investment (ROCI) model utilized, together with a previously-developed framework for evaluating cybersecurity technologies, by the resilient critical infrastructures through secure and efficient microgrids (ReCIst) capability. ReCIst uses this model to guide decision makers on how to best implement cybersecurity towards energy resiliency, from financial, security posture, and energy efficiency perspectives. Challenges and the current state of cyber investment modeling in this domain are presented along with technical details on ReCIst's ROCI model and future work.

Energy Efficiency in Short and Wide-Area IoT Technologies—A Survey

In the last years, the Internet of Things (IoT) has emerged as a key application context in the design and evolution of technologies in the transition toward a 5G ecosystem. More and more IoT technologies have entered the market and represent important enablers in the deployment of networks of interconnected devices. As network and spatial device densities grow, energy efficiency and consumption are becoming an important aspect in analyzing the performance and suitability of different technologies. In this framework, this survey presents an extensive review of IoT technologies, including both Low-Power Short-Area Networks (LPSANs) and Low-Power Wide-Area Networks (LPWANs), from the perspective of energy efficiency and power consumption. Existing consumption models and energy efficiency mechanisms are categorized, analyzed and discussed, in order to highlight the main trends proposed in literature and standards toward achieving energy-efficient IoT networks. Current limitations and open challenges are also discussed, aiming at highlighting new possible research directions.

Energy efficiency financing strategies and obstacles for residential public buildings in the Balkan region

The energy efficiency represents an international and multi-faceted phenomenon. It is especially important in the countries belonging to the Balkan’s region of the Southeastern Europe (SE). The research problem addressed in this paper focuses on the improvements in the inherent energy inefficiency by the means of quality financing of investment arrangements. This paper utilizes detailed literature review of multi-faceted sources, journal articles, private and government publications. Furthermore, the obstacles to attracting viable sources of private financing shall also be researched and addressed. Semi- developed and still developing Balkan countries have been experiencing severe lack of diversified financial instruments. The financial risks, energy poverty and low incomes, lack of appropriate understanding of the market and the absence of the appropriate regulatory framework have been identified as the major obstacles to attracting viable private financing. There are several issues impacting the attraction of private financing arrangements. These barriers could be summed up as the lack of appropriate regulatory framework, deficiencies in the proper market understanding, inherent presence of energy poverty and low incomes, multitude of financial risks, lack of skilled human resources, the presence of the so-called split incentives and fragmentation issues in common decision-making process. The so-called multiple benefits approach (MBA) to energy efficiency investments tend to widen the energy efficiency perspectives beyond the traditional measures of reducing energy demand and lowering greenhouse gas emissions. This approach looks into multiple spheres by assessing multitude of different benefits to stakeholders. In conclusion, the big disparity in size and variety or financial supporting instruments between the EU members and non-member states must be addressed and reduced.

Energy efficiency financing strategies and obstacles for residential public buildings in the Balkan region

The energy efficiency represents an international and multi-faceted phenomenon. It is especially important in the countries belonging to the Balkan’s region of the Southeastern Europe (SE). The research problem addressed in this paper focuses on the improvements in the inherent energy inefficiency by the means of quality financing of investment arrangements. This paper utilizes detailed literature review of multi-faceted sources, journal articles, private and government publications. Furthermore, the obstacles to attracting viable sources of private financing shall also be researched and addressed. Semi- developed and still developing Balkan countries have been experiencing severe lack of diversified financial instruments. The financial risks, energy poverty and low incomes, lack of appropriate understanding of the market and the absence of the appropriate regulatory framework have been identified as the major obstacles to attracting viable private financing. There are several issues impacting the attraction of private financing arrangements. These barriers could be summed up as the lack of appropriate regulatory framework, deficiencies in the proper market understanding, inherent presence of energy poverty and low incomes, multitude of financial risks, lack of skilled human resources, the presence of the so-called split incentives and fragmentation issues in common decision-making process. The so-called multiple benefits approach (MBA) to energy efficiency investments tend to widen the energy efficiency perspectives beyond the traditional measures of reducing energy demand and lowering greenhouse gas emissions. This approach looks into multiple spheres by assessing multitude of different benefits to stakeholders. In conclusion, the big disparity in size and variety or financial supporting instruments between the EU members and non-member states must be addressed and reduced.

Energy efficiency analysis of mass transport enhancement in time-periodic oscillatory electroosmosis

The streamwise mass transport of passive, neutral non-reacting solutes in oscillatory electroosmotic microchannel flows is theoretically investigated from an energy consumption and efficiency perspective for general asymmetric wall zeta potentials and slip velocities. Analytical solutions to the averaged mass transport and total power input (consisting of Joule heating, viscous dissipation, and sliding friction) are obtained and expressed in terms of the relevant parameters governing the system. Particularly, we define a “χg-parameter” to quantify the mass transport gained (excluding pure diffusion) per total power input in our analysis and discussions. While the no-slip, symmetric potential χg-performances agree with the mass transport results reported in previous literature, a “resonance like” behavior in the χg-performances is identified for large enough Womersley numbers and symmetric slip lengths despite the extra sliding friction, viscous dissipation, and Joule heating consumptions in the symmetric zeta potential configuration. When favorable asymmetries in the wall potentials and slip lengths are introduced, the χg-performances are not only considerably improved, but also highly correlated with the magnitudes of the velocity gradients in the oscillatory velocity profiles, hence reinforcing the physical picture of Taylor–Aris dispersion. Geometric symmetry can be identified among distinct velocity profiles which yield the same χg-performance. These profiles are generally associated with particular families of wall potential and/or slip length combinations also exhibiting symmetry among one another. Finally, the aspect ratio of the slit microchannel (width divided by length) is found to play a crucial role in significantly improving the χg-energy efficiency of mass transport in time-periodic electroosmosis.