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This paper aims to investigate the effect of frictional materials and surface texture on the energy conversion efficiency and the mechanical output performance of the ultrasonic motor (USM).

A newly designed testing system was set up to measure the mechanical output performance of the USM. The influence of different frictional materials on the output performance of the USM was studied under the same assembly process and parameters. The surface texture was fabricated by laser ablation processing. The effects of surface texture and input parameters on the energy conversion efficiency and mechanical output performance of the USM were studied.

The results show that polyimide (PI) composites as frictional material can significantly improve the output performance of the USM compared to polytetrafluoroethylene (PTFE) composites. When the pre-load is 240 N, the energy conversion efficiency of the USM using textured PI composites as frictional material can reach 41.93 per cent, increased by 29.21 per cent compared to PTFE composites, and the effective output range of the USM is increased to 0.7-1.1 N m. Besides, the pre-load and surface texture have a great influence on the output performance of the USM.

PI composites can improve the mechanical output performance of the USM. Surface texture can also improve the interface tribological properties and the energy conversion efficiency based on the advanced frictional materials, which will contribute to the increment of the output performance of the USM under the same input conditions.

Helical coil electromagnetic launchers (HEMLs) using motion-induced commutation strategy solve the problem of synchronization control perfectly. HEMLs can meet the requirements of multiple applications such as the electromagnetic catapult, electromagnetic mortar and high-velocity coilgun. The trade-off between the velocity and efficiency is an important basis for these different applications. To optimize such objectives before actual design, the purpose of this paper is to focus on the efficient and flexible calculation model and algorithm. A novel structure of HEML is proposed after the transient simulation by this algorithm, which can improve the energy conversion efficiency and suppress the muzzle arc without affecting the velocity too much.

The equivalent circuit model of the launcher is established and the governing equations are derived. A combination of the four-stage Runge–Kutta method and the trapezoidal quadrature formula are used to solve the governing equations.

With smaller number of turns in the coils of HEML, the velocity is larger and the efficiency is lower. The non-uniform HEML is an effective option to improve the energy conversion efficiency and to suppress the muzzle arc with almost the same muzzle velocity as the conventional HEML.

The paper presents a common model and a flexible fast numerical method which can be used in multi-objective optimization of HEMLs such as the genetic algorithm. A new structure of the non-uniform HEML is proposed to improve the energy conversion efficiency and to suppress the muzzle arc of the launcher.

To analyze the work principle and capacity of energy conversion in each segment of profile lines, the energy transfer from impeller to transmission medium is separated into head coefficient and load coefficient to analyze the energy transfer process. The concepts of airfoil lift coefficient and drag coefficient are used; the third manifestation of the Euler equations is used as well.

The numerical simulation of energy conversion mechanism based on load criteria of vane airfoil has been established in screw centrifugal pump to explain its energy conversion mechanism in an impeller. Upon this basis, the velocity and pressure along the entire blade are investigated through the numerical simulation of internal solid–liquid flow in the pump. The energy conversion process under load criteria in the blade airfoil has also been obtained.

The research suggests that the mathematical model of energy conversion mechanism based on the load criteria of the vane airfoil is reliable in the screw centrifugal pump. The screw centrifugal blade has twice or even several times the wrap angle than the ordinary centrifugal blade. It is a large wrap angle that forms the unique flow channel which lays the foundation for solid particles to pass smoothly and for soft energy conversion. At the same time, load distribution along the profile line on the long-screw centrifugal blade is an important factor affecting the energy conversion efficiency of the impeller.

The quantitative analysis method of energy in the screw centrifugal pump can help the pump designer improve certain features of the pump and shorten the research cycle.

The purpose of this paper is to present the design of a piezoelectric vibration energy generator with a power conditioning circuit to power a wireless sensor node. Frequency and voltage characterization of the piezoelectric energy harvester is performed. A single-stage AC–DC power converter that integrates the rectification and boosting circuit is designed, simulated and implemented in hardware.

The designed power conditioning circuit incorporates bridgeless boost rectification, a lithium ion battery as an energy storage unit and voltage regulation to extract maximum power from PZT-5H and to attain higher efficiency. The sensor node is modelled in active and sleep states on the basis of the power consumption. Dynamic modelling of the lithium ion battery with its state of charging and discharging is analysed.

The test result shows that the energy harvester produces a maximum power of 65.9 mW at the resonant frequency of 21.4 Hz. The designed circuit will operate even at a minimum input voltage of 0.5 V. The output from the harvester is rectified, boosted to a 7-V DC output and regulated to 3.3 V to the power C_Mote wireless sensor node. The conversion efficiency of the circuit is improved to 70.03 per cent with a reduced loss of 19.76 mW.

The performance of the energy harvester and the single-stage power conditioning circuit is analysed. Further, the design and implementation of the proposed circuit lead to an improved conversion efficiency of 70.03 per cent with a reduced loss of 19.76 mW. The vibration energy harvester is integrated with a power conditioning circuit to power a wireless sensor node C_Mote. The piezoelectric vibration energy harvester is implemented in real time to power C_Mote.

The aim of this study was to first establish foundational algebraic expressions that parametrically describe any advanced dual-energy storage–propulsion–power system (DESPPS) and then proceed to declare the array of fundamental independent variables necessary for the sizing and optimisation of such systems. Upon procurement of a pre-design-level integrated aircraft performance model and the subsequent verification against previously published high-end low-fidelity generated results, opportunity was taken in formulating a set of battery-based DESPPS related design axioms and sizing heuristics.

Derivation of algebraic expressions related to describing DESPPS architectures are based on first principles. Integrated performance modelling by way of full analytical fractional change transformations anchored according to a previously published Energy Specific Air Range (ESAR) figure-of-merit originally derived using the Breguet–Coffin differential equation for vehicular efficiency. Weights prediction of sub-systems that constitute the entire aircraft including DESPPS constituents emphasises an analytical foundation with minimal implementation of linear correlation factors or coefficients of proportionality. An iterative maximum take-off weight build-up algorithm emphasising expedient and stable convergence was fashioned. All prediction methods pertaining to integrated performance were verified according to previously published battery-based DESPPS results utilising high-end low-fidelity methods.

For all types of DESPPS, two new fundamental independent non-dimensional variables were declared: the Supplied Power Ratio (related to converted power afforded by each energy carrier); and, the Activation Ratio (describing the relative nature of utilisation with respect to time afforded by the motive power device associated with each energy source). For a given set of standalone sub-system energy conversion efficiencies, the parametric descriptor of degree-of-hybridisation (DoH) for Power was found to be solely a function of the Supplied Power Ratio, whereas in contrast, the DoH for Energy was found to be a more complex synthetic function described by comingling of Supplied Power Ratio and the Activation Ratio. Upon examination of the integrated aircraft performance model derived in this treatise, for purposes of investigating CO₂-emissions reduction potential for battery-based DESPPS using kerosene as one of the energy sources, one salient observation was maximising the ESAR figure-of-merit is not an appropriate objective or intermediary function for future optimisation work. It was found maximising block fuel reduction through the use of maximum ESAR would lead to ever diminishing design ranges and curtailment of the payload-range working capacity of the aircraft.

Opportunity is now given to design and optimise aircraft utilising any type of DESPPS architecture. It was established that designing for battery-based DESPPS aircraft can be achieved effectively in a two-stage process that may not require aircraft morphologies more exotic than the so-called “wing-and-tube”. Firstly, a suitably projected state-of-the-art aircraft with solely advanced gas-turbine technology for the propulsion and power system needs to be produced. Thereafter, a revised version of this baseline projected aircraft now using DESPPS architecture should be conceived. A recommendation related to CO₂-emissions reduction potential for battery-based DESPPS using kerosene as one of the energy sources is that during optimisation work the multi-objective formulation should comprise at least two functions: block fuel and operating economics. In all instances, it was advised that the objective function of block fuel should be tempered by an equality constraint of ESAR parity with the baseline projected aircraft using gas-turbine only technology.

A complete, unified analytical description of DESPPS that is universally applicable to any type of energy carrier has been derived and verified for battery-based dual-energy systems. Correspondingly, a set of aircraft design axioms and sizing heuristics relevant to battery-based DESPPS have been presented.

This study aims to identify sustainability indicators in the energy sector through a literature review and validate them from the perspective and context of professionals working in the sector in an emerging economy country, Brazil, considering the relationship of these indicators with the achievement of the targets set by the United Nations sustainable development goals (UN SDGs).

To accomplish this, a literature review on sustainability indicators specific to the energy sector was conducted. Subsequently, a research instrument (questionnaire) based on the identified indicators was developed and a survey was administered to professionals in the field. The collected data were analyzed using the Lawshe method.

The results revealed 20 indicators, distributed across environmental, economic and social dimensions. Among these, nine indicators were validated, including global impacts, local impacts, renewable energy production as a percentage of total production, greenhouse gas emissions, access to electricity, investment in the energy sector, installed capacity in the electricity sector, energy prices in the end-use sector and energy distribution and conversion efficiency.

Consequently, it was possible to determine which SDGs are directly impacted and provide a foundation for future actions that can contribute to the sustainable advancement of the energy sector in emerging countries.

The limited energy density of batteries generates the need for high-performance power sources for emerging eVTOL applications with radical operational improvement potential over traditional aircraft. This paper aims to evaluate on-design and off-design recuperated turbogenerator performances based on newly developed compression loaded ceramic turbines, the Inside-out Ceramic Turbine (ICT), in order to select the optimum engine configuration for sub-megawatt systems.

System-level thermal engine modeling is combined with electric generators and power electronics performance predictions to obtain the Pareto front between efficiency and power density for a variety of engine designs, both for recuperated and simple cycle turbines. Part load efficiency for those engines are evaluated, and the results are used for an engine selection based on a simplified eVTOL mission capability.

By operating with high turbine inlet temperature, variable output speed and adequately sized recuperator, a turbogenerator provides exceptional efficiency at both nominal power and part load operation for a turbomachine, while maintaining the high power density required for aircraft. In application with a high peak-to-cruise power ratio, such power source would provide eight times the range of battery-electric power pack and an 80% improvement over the state-of-the-art simple cycle turbogenerator.

The implementation of a recuperator would provide additional gains especially important for military and on-demand mobility applications, notably reducing the heat signature and noise of the system. The engine low-pressure ratio reduces its complexity and combined with the fuel savings, the system could significantly reduce operational cost.

Implementation of radically new ICT architecture provides the key element to make a sub-megawatt recuperated turbogenerator viable in terms of power density. The synergetic combination of a recuperator, high temperature turbine and variable speed electric generator provides drastic improvement over simple-cycle turbines, making such a system highly relevant as the power source for future eVTOL applications.

The purpose of this study is to investigate the influence mechanism of different interface component surface textures on the ultrasonic motor (USM) output performance.

The energy transmission mechanism of the traveling-wave ultrasonic motor 60 (TRUM-60) was numerically and experimentally investigated by fabricating dimple textures with different feature types on the friction material and the stator.

Textured friction material can increase the contact range effectively, and thus, can improve the friction characteristics of the interface and the output performance of the TRUM-60. The experimental results verified the expected influence mechanism and demonstrated that the use of either a textured friction material or stator has a very different effect on USM output performance. A textured PI-based friction material improved the TRUM-60 output performance, resulting in a maximum energy conversion efficiency of 57.11%. However, a textured stator degraded the TRUM-60 output performance, resulting in a minimum energy conversion efficiency of only 44.92%.

The results of this study provide a theoretical foundation for improved USM designs with textured interfaces.

To better understand bioenergy's role in sustainable rural development and cleaner environment, it is necessary to place it in a local regional context. This paper aims to provide a conceptual approach for biomass-based energy self-sufficiency in rural areas of developing and underdeveloped countries having a strong agricultural sector. It further provides a framework for the estimation of surplus biomass and bioenergy potential and the biomass power emissions in a rural area.

A detailed approach is laid out to attain energy self-sufficiency in rural areas encompassing identification of surplus biomass resources in a selected area, suitable conversion technologies, consideration of local end-use priorities, skill development and monitoring of the project.

Following the novel approach proposed in this paper a case study analysis for Thanagazi block (Alwar District, India) is done, and it is observed that locally available biomass in the block can substitute more than 75% of the conventional energy demand and save 78% emissions vis-à-vis equivalent coal power. This indicates that creating local bioenergy production system as a means of substituting/complementing fossil energy can contribute to a cleaner self-sufficient ecosystem.

Biomass is a spatio-temporal resource. Prior works have looked at bioenergy potential for national or state levels; however, granular data to reveal a more realistic outlook in a rural area is the novelty of this work. Furthermore, biomass assessment studies largely focus on crop residual biomass, whereas the present study also includes livestock manure assessment which is a major resource in rural areas. This paper highlights the need and the approach for exploring locally available biomass to meet the local energy demands for clean energy security while considering the involvement of the local population in bioenergy planning and implementation.

This paper aims to deal with the development of a software tool to simulate and study vehicle – road interaction (VRI) to quantify the forces induced and energy released from vehicles to the road pavement, in different vehicle motion scenarios, and the energy absorbed by the road surface, speed reducers or a specific energy harvester surface or device. The software tool also enables users to quantify the energetic efficiency of the process.

Existing software tools were analysed and its limitations were identified in terms of performing energetic analysis on the interaction between the vehicle and the road pavement elements, such as speed reducers or energy harvest devices. The software tool presented in this paper intends to overcome those limitations and precisely quantify the energy transfer.

Different vehicle models and VRI models were evaluated, allowing to conclude about each model precision: bicycle car model has a 60 per cent higher precision when compared with quarter-car model, and contact patch analysis model has a 67 per cent higher precision than single force analysis model. Also, a technical study was performed for different equipment surface shapes and displacements, concluding that these variables have a great influence on the energy released by the vehicle and on the energy harvested by the equipment surface.

The developed software tool allows to study VRI with a higher precision than existing tools, especially when energetic analyses are performed and when speed reduction or energy harvesting devices are applied on the pavement.