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Being inspired by the “seismonastic reaction” of Mimosa pudica, an asymmetric swelling system was constructed to induce the controllable directional deformation of filter paper. In this work, multifunctional biomimetic Janus paper was facilely fabricated via depositing poly(vinylidene fluoride) (PVDF) on one side of Qualitative Filter Paper (QFP), the permeation of polymer solutions within filter paper was well controlled during fabrication. The wetting and swelling behavior of the prepared Janus paper were detected. The Janus paper showed controllable swelling-induced deformations in water. Both the degree and orientation of the deformation were fully investigated. On the one hand, the degree of deformation depends on the gradient wettability and hygroscopicity of the Janus paper, on the other hand, the orientation of deformation is related to the storage and release of stress. Additionally, the steady deformation during swelling endows the Janus paper with novel shape memory property both under idling and loading conditions. The Janus paper was also applied to achieve reversible energy conversion from the swelling potential energy to mechanical potential energy.

Space nuclear reactor power (SNRP) using a gas-cooled reactor (GCR) and a closed Brayton cycle (CBC) is the ideal choice for future high-power space missions. To investigate the safety characteristics and develop the control strategies for gas-cooled SNRP, transient models for GCR, energy conversion unit, pipes, heat exchangers, pump and heat pipe radiator are established and a system analysis code is developed in this paper. Then, analyses of several operation conditions are performed using this code. In full-power steady-state operation, the core hot spot of 1293 K occurs near the upper part of the core. If 0.4 $ reactivity is introduced into the core, the maximum temperature that the fuel can reach is 2059 K, which is 914 K lower than the fuel melting point. The system finally has the ability to achieve a new steady-state with a higher reactor power. When the GCR is shut down in an emergency, the residual heat of the reactor can be removed through the conduction of the core and radiation heat transfer. The results indicate that the designed GCR is inherently safe owing to its negative reactivity feedback and passive decay heat removal. This paper may provide valuable references for safety design and analysis of the gas-cooled SNRP coupled with CBC.

This paper presents a dynamic voltage restorer to solve the voltage sag problem that causes the most serious economic loss among various grid accidents. The proposed method, which uses a direct AC–AC converter, consists of a simple controller unlike methods using a voltage source inverter that is controlled using complex operations. Unlike the energy storage type, there is no additional energy storage device, which reduces system cost. In addition, unlike the back-to-back type, energy conversion loss is reduced by one stage conversion. A switching cell-structured direct AC–AC converter that solves the rectification problem without a separate sensor is a reliable structure that reduces the volumes of the passive filters by increasing the switching frequency. In addition, using interphase voltages, it can take a wide range of voltage compensations to compensate for most of the voltage sag in various situations. In this paper, the background of the study is revealed and the operating principles and control schemes of the proposed system are analyzed. Then, the validity of this study is confirmed through simulation and experiment results.

Micro/nanostructures play a key role in tuning the radiative properties of materials and have been applied to high-temperature energy conversion systems for improved performance. Among the various radiative properties, spectral emittance is of integral importance for the design and analysis of materials that function as radiative absorbers or emitters. This paper presents an overview of the spectral emittance measurement techniques using both the direct and indirect methods. Besides, several micro/nanostructures are also introduced, and a special emphasis is placed on the emissometers developed for characterizing engineered micro/nanostructures in high-temperature applications (e.g., solar energy conversion and thermophotovoltaic devices). In addition, both experimental facilities and measured results for different materials are summarized. Furthermore, future prospects in developing instrumentation and micro/nanostructured surfaces for practical applications are also outlined. This paper provides a comprehensive source of information for the application of micro/nanostructures in high-temperature energy conversion engineering.

This paper presents a new structure of solar cells based on NEMS (Nano Electro Mechanical System) technology to eliminate dependence of cell to band gap energy and improve efficiency. In this paper, the process of converting solar energy to electrical energy using NEMS solar cell, which is able to convert the thermal to mechanical energy and then to electrical energy by changing the temperature and using direct piezoelectric effect, is investigated. Thus, unlike photovoltaic cells, these cells have ability to absorb the full spectrum of the sun’s radiation. Energy conversion is such that at first a two-layer cantilever with different thermal expansion coefficient (Al aluminum and SiO2 Silicon Oxide) is diverted by solar energy absorption, thus the solar energy is converted to mechanical energy. This structure is capable to receive heat energy from all spectrum of solar radiations. The mechanical oscillation of PZT (Lead Zirconate Titanate) nanowires, which are perpendicular to cantilever beams, is converted to electrical energy. The electrical voltage produced by the proposed structure is an alternating voltage with amplitude of 0.9 volts. Also, the efficiency of this proposed cell, which was introduced at first time and does not have a similar sample, is 40% which shows improved performance and much smaller size compared to previous works.

China’s fossil energy is characterized by an abundance of coal and a relative lack of oil and natural gas. Developing a strategy in which coal can replace oil and natural gas is, therefore, a necessary and practical approach to easing the excessive external dependence on oil and natural gas. Based on the perspective of energy security, this paper proposes a technical framework for defining the substitution of oil and natural gas with coal in China. In this framework, three substitution classifications and 11 industrialized technical routes are reviewed. Then, three scenarios (namely, the cautious scenario, baseline scenario, and positive scenario) are developed to estimate the potential of this strategy for 2020 and 2030. The results indicate that oil and natural gas replaced by coal will reach 67 to 81 Mt and 8.7 to 14.3 Gm3 in 2020 and reach 93 to 138 Mt and 32.3 to 47.3 Gm3 in 2030, respectively. By implementing this strategy, China’s external dependence on oil, natural gas, and primary energy is expected to be curbed at approximately 70%, 40%, and 20% by 2030, respectively. This paper also demonstrates how coal, as a substitute for oil and natural gas, can contribute to carbon and pollution reduction and economic cost savings. It suggests a new direction for the development of the global coal industry and provides a crucial reference for energy transformation in China and other countries with similar energy situations.

This paper presents a fault detection method for induction generators using an unscented Kalman filter. In some applications such as wind turbine energy conversion systems, the induction generators experience oscillations caused by wind speed variation; therefore, the fault detection method should be able to detect fault in the presence of these oscillations. On the other hand, the induction generator may operate in islanded mode of operation, the situation that does not happen in motor application. In the present paper, the type of fault is the rotor electrical asymmetry and the proposed method is able to detect the fault in both grid-connected and islanded modes of operation. Several scenarios are simulated, and the efficacy of the proposed technique is evaluated by means of simulation results. Moreover, experiments are performed to validate the ability of the proposed method.

In order to solve the installation application problem of positive temperature coefficient (PTC) materials in the field of thermal management for electronic devices and energy conversion system, a novel flexible thin film room temperature polymer PTC material is prepared and studied in this paper. The material is prepared by mixing graphite powder (GP) in paraffin/olefin block copolymer (OBC) in which OBC provides flexibility as a supporting material. Besides, the PTC characteristics and mechanical properties of the material are studied experimentally. It is found that the prepared composites have good PTC characteristics and flexibility. The measuring results show that flexibility of the novel PTC material is optimal when the content of graphite powder is 40% and mass proportion of OBC/paraffin is 30:70; at this time, the PTC intensity of the material can reach 2.9 and low temperature resistivity of the material is about 1800 Ω∙cm. Meanwhile, the novel PTC material is compared with the conventional PTC material through various experiments. It is found that the novel PTC material prepared in this paper has better performance than the conventional PTC material in many aspects, and has better prospect and practical value.

A multi-blade ducted wind turbine, also called the diffuser augmented wind turbine (DAWT) has a good wind energy conversion effect over the traditional wind turbine. The market potential for energy recovery from the chimney flue gases made it necessary to explore the possibility of extraction of the energy from flue gases using the DAWT. The duct is a converging-diverging nozzle with the turbineblades located at the throat. In general 3 or more number of blades is frequently used to maximize the energy conversion to the bladetorque. The effect of number of blades on the power extraction by the energy recovery ducted turbine has been studied in this paper. A CFD-based simulation study has been carried out. The results so obtained have been benchmarked with the published data for the results for the ducted turbines for wind power generation. The general airfoil NACA4420, NACA4416 and NACA4412 were adopted to produce various composite profiles for turbine-blade. The large number of blades appears to provide the sufficient blade areas for the conversion of energy of flue gases to the turbine-rotor torque. On other hand the more number of blades also increases the blockage to the flue gases, resulting in increased back-flow. This paper presents the variation of power coefficient (CP) and torque coefficient (CT) with respect to the tip speed ratio (λ) for different number of blades, and varying blade geometry.

This paper represents an electrical modeling of a photovoltaic water pumping system composed of photovoltaic panels. The system reassures electrical energy generation applying a DC buck converter in order to supply a DC motor to pump water. Known for its optimal electrical and physical properties, the super capacitor is integrated into the PV pumping system to allow storing electrical energy and powering the pumping motor at nights and cloudy days. The implementation of the perturbation and observation algorithm in the DC buck converter reassures the system’s operation around the maximum power point produced by the photovoltaic panel. Moving from quantity problem to quality problem, several internal and external factors can infect the stability of the PV pumping system and disrupt its operation around nominal point. On account of this, a pole placement technique is proposed in this paper. This technique is advocated not only for its simple processing and rapid execution, but also for being based on the conversion of the electrical model of the PV pumping system into a mathematical model that comprises matrix equations. This energy conversion process allows variations in output values in proportion to the input evolution along with positioning the system’s poles in the stable points of the S-plane. The equation of this technique applied to the photovoltaic pumping system is indicated in this paper having its program created in Matlab and installed in PLC S7-200 on account of its ability to monitor the inputs instantaneously and modify the outputs in a way proportional to the installed program. Subsequently, the validation of the robustness of this technique is reassured by the comparison between the simulation in Matlab and the experimental tests carried out in sunny periods having the engine powered by photovoltaic panels, and shaded periods where power supply is reassured by the super capacitor.

This paper investigates the wave energy conversion performance of floating and submerged heaving vertical-cylinder buoys. Two types of reactive control strategies are evaluated for their effect on energy absorption in irregular waves described by uni-modal spectra. Approximate near-optimal reactive control based on up-wave surface elevation measurement and peak-frequency tuning are compared for performance improvements over constant-damping load. The paper describes time-domain calculations under unconstrained oscillation in long-crested irregular waves for two sets of buoy dimensions. Supporting analysis and frequency-domain calculations suggest that near-optimal control performs considerably better than peak-frequency tuning for the submerged buoys and somewhat better for the floating buoys. The relative contributions of the Froude–Krylov and diffraction force components, and wave radiation properties for the two configurations are found to be important in this context.

The integration and accommodation of the wind and solar energy pose great challenges on todays power system operation due to the intermittent nature and volatility of the wind and solar resources. High efficient large-scale electrical energy storage is one of the most effective and economical solutions to those problems. After the comprehensive review of the existing storage technologies, this paper proposes an overall design scheme for the Non-supplementary Fired Compressed Air Energy Storage (NFCAES) system, including system design, modeling and efficiency assessment, as well as protection and control. Especially, the design principles of the multistage regenerative, i.e. heat recovery system which is used to fully recycle and utilize the waste heat from compression are provided, so as the overall system efficiency evaluation method. This paper theoretically ascertains the storage decoupling rules in the potential and internal energy of molecular compressed air and reveals the conversion mechanism of gas, heat, power, electricity and other forms of energy. On this basis, a 500-kW physical simulation system of CAES system (TICC-500, Tsinghua-IPCCAS-CEPRI-CAES) is built, which passed a system-wide 420-kW load power generation test with less pollution and zero carbon emissions. Besides, the multi-form energy conversion of multi-stage regenerative CAES and storage efficiency is verified, especially its incomparable superiority in solving the uncertainty problem in wind and solar power generation. Finally, the propaganda and application scenario of the CAES system in China is introduced.

The design scheme of a sandwich-structure betavoltaic microbattery based on silicon using 63Ni is presented in this paper. This structure differs from a monolayer energy conversion unit. The optimization of various physical parameters and the effects of temperature on the microbattery were studied through MCNP. For the proposed optimization design, P-type silicon was used as the substrate for the betavoltaic microbattery. Based on the proposed theory, a sandwich microbattery with a shallow junction was fabricated. The temperature dependence of the device was also measured. The open-circuit voltaic (Voc) temperature dependence of the optimized sandwich betavoltaic microbattery was linear. However, the Voc of the betavoltaic microbattery with a high-resistance substrate exponentially decreased over the range of room temperature in the experiment and simulation. In addition, the sandwich betavoltaic microbattery offered higher power than the monolayer betavoltaic one. The results of this paper provide a significant technical reference for optimizing the design and studying temperature effects on betavoltaics of the same type.

The study of ecosystems suggests principles by which energy flows generate hierarchies in all systems. All ecosystems in the landscapes are associated with energy transformation and the convergence of transformed products toward higher hierarchical levels, the recycling of materials to dispersed backgrounds, and feedbacks to reinforce the supporting environment. A hierarchy can be seen as an organized pattern with many small units at one level contributing to fewer units at the next higher level. Due to spatial variability in the natural environment, different types and amounts of energy received on the earth are not homogeneous; this in turn generates a heterogeneous pattern on the landscape. Energy from life-support and production systems of a heterogeneous landscape is transformed and converged spatially toward consumption centers. All energy transformation can be arranged in a series. The concept of transformity is used in this paper to indicate the position of an energy flow in the series. A hierarchical system can help to explain how energy and matter can be produced and recycled through each level of energy transfer. Building on the brief reviews of the concept of hierarchy in the landscape and the theoretical development of the concept of an ecological energetic hierarchy, this paper proposes two principles of energetic hierarchy for landscape sustainability. First, the landscape must be arranged spatially according to its energy hierarchy. Evaluation of normalized energy flows (emergy) can help identify zones of different spatial hierarchies, which will help establish the strategies needed for the landscapes to be sustainable. Second, a sustainable landscape must comprise a hierarchy of self-organizing ecosystems that can enable the systems to maximize useful power at all levels of the energy hierarchy.

A class of one-way isothermal mass transfer processes with Fick’s diffusive mass transfer law [g ∝ Δ(c)] is investigated in this paper. Based on the definition of the mass entransy, the entransy dissipation function which reflects the irreversibility of mass transfer ability loss is derived. The optimal concentration allocations of the key components corresponding to the highand low-concentration sides for the minimum entransy dissipation of the mass transfer process are obtained by applying optimal control theory and compared with the strategies of the minimum entropy generation, constant mass transfer flux (constant concentration difference), and constant concentration ratio (constant chemical potential difference). The results are as follows. For the optimal mass transfer strategy of the minimum entransy dissipation, the product of the square of the key component concentration difference between the high- and the low-concentration sides and the inert component concentration at the low-concentration side is a constant, while for that of the minimum entropy generation, the ratio of the square of the key component concentration difference between the high- and the low-concentration sides to the key component concentration at the low-concentration side is a constant; when the mass transfer process is not involved in energy conversion process, the optimization principle should be the minimum entransy dissipation; the mass transfer strategy of constant concentration difference is superior to that of constant concentration ratio. The results obtained in this paper can provide some theoretical guidelines for optimal designs and operations of practical mass transfer processes.

This overview will describe briefly key segments of the hydrogen energy cycle from production using various feedstocks to its end use in fuel cells to generate electrical and thermal energy. The paper will also discuss the larger societal context, the so-called “hydrogen economy,” in which such production and use of hydrogen may take place. Although most of the public attention on hydrogen has been focused on its potential as an alternative energy source to petroleum and other fossil fuels, a hydrogen economy will encompass much more than a substitution of one energy source by another. Widespread use of hydrogen as an energy carrier can transform our society in much the same way that personal computing technologies have. This transforming power arises from the unique capability of hydrogen to link renewable energy resources and zero-emission energy conversion technologies. Hydrogen can be produced from locally available renewable resources, such as solar, wind, biomass, and water, and converted to electricity or fuel at or near the point of use with only heat and water vapor as “emissions.” Hydrogen also lies at the confluence of two emerging trends that will shape our energy future during the first quarter of this century: greater reliance on renewable energy sources and the shift from large, centralized power plants to smaller, decentralized facilities located at or near the point of use. This paper describes these emerging trends and the role of hydrogen in linking them in a way that could transform our society.

It's not adequate to just obtain eigenvalue for solving eigenvalue problem. Since the eigenvalues associated with longitudinal characteristic modes in dielectric waveguide array (DWA) has been studied, the paper concentrates on the corresponding eigenvector, namely, the amplitude of these characteristic modes. Through numerical study of the amplitude of longitudinal guided TE and TM modes in DWA, space harmonic (SH) coupling and energy conversion effect have been discovered. The paper not only contribute to deep understand the mechanism of SH interaction, but also do good to analyze the resonance, radiation problem in DWA.

The objective of this paper is to compare the performances of the turbines, which could be used for wave energy conversion in the near future, under various irregular wave conditions. The turbines included in the paper are as follows: (a) Wells turbine with guide vanes; (b) impulse turbine with self-pitch-controlled guide vanes; (c) impulse turbine with fixed guide vanes. In this study, experimental investigations were carried out to clarify the performances of the turbines under steady flow conditions, and then a numerical simulation was used for predicting the performances under irregular wave conditions with various significant wave heights. As a result, it was found that the running and starting characteristics of the impulse turbines could be superior to those of the Wells turbine.

The paper is devoted to recent results concerning investigation of physical processes occurring in a “laser greenhouse” target. Results of experimental and theoretical studies of laser-pulse interaction with a low-density absorber of the target, namely, with a porous substance having density close to the plasma critical density, are presented. On the basis of a vast cycle of experiments carried out in a number of laboratories, it is shown that the absorption of the laser radiation in porous media, including those with a density exceeding the critical one by at least a factor of 4 to 6, has a bulk nature and is distributed over the target depth. In particular, the laser-radiation absorption region in a porous substance with density 10−3–10−2 g/cm3 is extended into the target 400–100 μm, respectively. The coefficient of absorption of laser radiation with intensity 1014–1015 W/cm2 in porous substances, including those of the supercritical density, is 70–90%. Experiments have not shown enhanced (compared to a solid-state target) radiation intensity associated with a possible development of parametric instabilities in an extended laser plasma of low-density porous media, as well as noticeable contribution of fast electrons to the energy balance and their effect on the energy transfer. In this paper, theoretical models are developed explaining features of the laser-radiation absorption and energy transfer in porous media. These models are based on the phenomenon of laser-radiation interaction with solid components of a porous substance and plasma production inside pores and cells of the medium. The efficiency of energy conversion in the vicinity of the ignition threshold for the laser-greenhouse target is investigated in the case of an absorber having the above properties. Numerical calculations have shown that a thermonuclear-gain coefficient of 1 to 2 (with respect to the energy absorbed) is attained for a laser-radiation energy of 100 kJ.

Computationally fast and accurate mathematical models are essential for effective design, optimization, and control of wave energy converters. However, the energy-maximising control strategy, essential for reaching economic viability, inevitably leads to the violation of linearising assumptions, so the common linear models become unreliable and potentially unrealistic. Partially nonlinear models based on the computation of Froude–Krylov forces with respect to the instantaneous wetted surface are promising and popular alternatives, but they are still too slow when floaters of arbitrary complexity are considered; in fact, mesh-based spatial discretisation, required by such geometries, becomes the computational bottle-neck, leading to simulations 2 orders of magnitude slower than real-time, unaffordable for extensive iterative optimizations. This paper proposes an alternative analytical approach for the subset of prismatic floating platforms, common in the wave energy field, ensuring computations 2 orders of magnitude faster than real-time, hence 4 orders of magnitude faster than state-of-the-art mesh-based approaches. The nonlinear Froude–Krylov model is used to investigate the nonlinear hydrodynamics of the floater of a pitching wave energy converter, extracting energy either from pitch or from an inertially coupled internal degree of freedom, especially highlighting the impact of state constraints, controlled/uncontrolled conditions, and impact on control parameters’ optimization, sensitivity and effectiveness.

The magnetoelectric (ME) laminated composite is an important multifunctional material for developing novel electronic devices that provide many applications in sensing, energy conversion, filtering, etc. Following the previous investigations, this paper proposes theoretical modeling to study the relationship between a bar-shaped ME laminated composite's enhancement effects and material properties. This composite has a breakthrough idea that produces two operating modes (sensing and transducing) in the same working process. Our analyses are based on the magneto-elastic-electric equivalent circuit and mechanical connections between an ME laminated composite and a piezoelectric plate. Our works not only predicted the ME outputs against magnetic field bias change but also studied the relationship of the length ratio between the ME laminated composite and the piezoelectric plate. The results showed that the ME outputs of the transduction mode are much bigger than the sensing mode at resonance, which strongly depended on the dimension and the physical properties of the sample. These findings provided a promising gate for the researchers to develop a single electronic device that combined sensing and power conversion.

This paper proposes a deflectable switched reluctance motor/generator, which can be used in wave energy conversion and underwater propulsion systems. When an underwater vehicle stops working, the ocean current drives the turbine blades connected to the motor to rotate, and the rotating turbine blades drive the deflectable generator shaft to generate electricity. The deflectable motor can complete multi-degree-of-freedom motion, so it can receive ocean current energy in multiple directions, thereby improving energy extraction efficiency. When the underwater vehicle starts to work, the deflectable motor can freely adjust the course of the vehicle, so that the vehicle can yaw freely under water. The finite element method is used to analyze the air gap flux density during rotation and deflection. The relationship between the flux, torque and current of a single coil under different rotor positions is obtained, and then the output current and voltage of the deflectable generator are obtained. Finally, a prototype was made for experimental verification.

The torsional vibration is a technical problem during the rolling process, which seriously affects rolling stability and production efficiency. In order to study the influence of axis deviation of the rolling mill transmission system on torsional vibration, a reasonable dynamic model can be established to explore its dynamic characteristics. In this paper, considering the periodic excitation caused by the axis deviations and the torsional torque change under the torsional vibration, the nonlinear dynamic model of the transmission system was established. The simulation results show the energy input to the main transmission system approximately periodically through obtaining the drive energy of the rolling mill motor by the equivalent eccentric mass. The dynamic change of tension and friction moment of the strip is caused by the torsional vibration of the transmission system, which leads to an unstable energy conversion process in the rolling interface. Through the monitoring experiment data by taking the 7-stand tandem hot rolling mill of Chengde Steel Co. for example, the theory reliability was further verified. All these research results are significant to solving the torsional vibration problem of rolling mill drive system with axis deviations and provide references for the operation in the strip production process.

A variety of energy sources will compete to provide the energy services that humans will require over the next 100 years. The balance of these sources will depend upon the availability of fossil fuels and the development of new technologies including renewable energy technologies, and will be one of the keys in projecting greenhouse gas emissions. There is uncertainty about each of the energy sources. With oil, for example, there are two alternate views of future reserves, one that reserves are geologically limited and that supplies will decline within a decade or two, the other that there are enormous quantities of hydrocarbon in the earth’s crust and that reserves are a function of developing technology and price. With solar voltaics, as a second example, there is optimism that the technology will become increasingly competitive, but there is uncertainty about the rate at which costs can come down and about ultimate cost levels. This paper reviews the reserves of fossil fuels and the prospects for nuclear power and the renewables. It also reviews the main energy conversion technologies that are available now or are expected to become increasingly available through time. However, it should be noted that, over a time horizon of 100 years, there may be quite radical changes in both production and conversion technologies that cannot be predicted and it is quite possible for some as yet unheard of technology to be developed and to transform the markets. The paper has been written to aid the development of new scenarios for the emission of greenhouse gases for the Intergovernmental Panel on Climate Change.

The increased demand and production of tyres led to vast quantities of discarded tyres. Landfilling and open burning of waste tyres (WT) are associated with significant environmental implications. Life cycle assessment of WT indicates that a considerable amount of energy can be recovered from them, which can help to lower their environmental impacts. Stricter global regulations have prompted researchers to look for thermal treatments such as gasification and pyrolysis of WT to produce gaseous (syngas and hydrogen gas), liquid (bio-oil), and solid (char) fuels under controlled conditions. The key parameters affecting the quality of these products are the kind of reactors, reaction conditions, quality and nature of WT. This review aims to address the properties of tyres and their life cycle assessment. The paper provides insights into the latest development in a fixed bed, fluidized bed and rotary bed gasifiers and pyrolyzers to recover the maximum energy from WT. The outcomes of various laboratory-scale studies, scale-up of technology, global commercial status, and gaps for the broader acceptance of energy conversion technologies are discussed here.

Energy conversion and storage in a Li-ion cell involves multiple closely coupled transport processes, such as species diffusion through solid and solution phases in the electrode. Mathematical modeling of these processes is critical for fully understanding and optimizing the performance of a Li-ion cell. While a number of analytical and numerical models have been presented for solution phase diffusion, most of such work is based on the assumption of a constant current density. This paper presents analytical modeling of solution phase diffusion in a separate–electrode composite for a generalized, time-dependent current density. An analytical solution for the concentration field in a separator–electrode composite in such conditions is derived using the method of eigenfunction expansion. Good agreement with past work as well as numerical simulations is shown. Results for linear, periodic and step-function boundary conditions are discussed. The theoretical analysis presented here may help accurately model realistic processes where the applied current changes over time, for example, cyclic charge and discharge in an electric vehicle, or sudden changes in the battery load. Results presented here contribute towards the fundamental understanding of solution phase diffusion in Li-ion cells, and provide a basis for improving electrochemical energy conversion and storage processes.

In this study, it is aimed to determine the energy generation capability of the designed and manufactured thermoelectric system when mounted on the two-axis solar tracking system. Thus, it was possible to compare the results obtained from current study with previous study. The system used in previous study was comprised of a thermoelectric generator (TEG) for energy conversion, a linear Fresnel lens for concentrating solar rays, and a one-axis tracking system to increase the electrical and thermal efficiency of the system. In this study, a dual-axis (two-axis) tracking system was used as a tracking system to examine the change in thermal and electrical efficiency. Therefore, experimental measurements were performed again using both two-axis and one-axis solar tracking systems on 16th October 2019 and 17th October 2019, respectively, at the location which falls at 41°14′ N and 36°26′ E. Additionally, the heat transfer and electricity generation performance of TEG was theoretically analyzed using CFD model. For this purpose, a numerical model consisting TEG with heat sink was developed. It was observed that the model data obtained and the experimental data were in good agreement. The values of parameters such as temperature, solar radiation, wind speed and TEG open circuit voltage were measured instantaneously during the measurements. The maximum open circuit voltages obtained is 1.02 and 1.13 V for one-axis and dual-axis systems, respectively. The solar radiation values were measured as 464 and 472 $$\mathrm{W}/{\mathrm{m}}^{2}$$ , respectively when the maximum open circuit voltages value is obtained. The duration for measurements was kept about 15 min so that the average values of these parameters were used in calculations. Thus, the values of maximum output power $$\left({\mathrm{P}}_{\mathrm{maxout}}\right)$$ , electrical efficiency $$\left({\upeta }_{\mathrm{e}}\right)$$ and Seebeck coefficient $$\left( {\alpha _{{{\text{TEG}}}} } \right)$$ were calculated and given in the paper.

There is a large amount of inertial kinetic energy wasted during the driving of new energy driverless buses. In this paper, a novel multidirectional pendulum kinetic energy harvester, based on homopolar repulsion, is designed for low-powered sensors in new-energy driverless buses. The proposed system consists of three main components: kinetic energy harvest module, energy conversion module and power storage module. The kinetic energy harvest module includes a multidirectional capture mechanism and a deformation amplification mechanism, which captures the acceleration direction of the vehicle, and harvests the inertial kinetic energy through the pendulum swinging respectively. In the energy conversion module, deformation of the piezoelectric beam generates electricity, due to homopolar repulsion from the magnets on the pendulum and piezoelectric beam. The power storage module stores electricity in supercapacitors to power the inertial measurement unit, acceleration sensor and other low-power sensors. The proposed system has completed simulation analysis and prototype tests, which show that the system featuring voltage of 13.6 V and power of 1.233 mW, illustrating the feasibility of self-powered applications in low-power sensors for new energy driverless buses. Flow chart of the proposed kinetic energy harvester

The exploration of cost-effective, high-performance, and stable electrocatalysts for the hydrogen evolution reaction (HER) over wide pH range (0–14) is of paramount importance for future renewable energy conversion technologies. Regulation of electronic structure through doping vanadium atoms is a feasible construction strategy to enhance catalytic activities, electron transfer capability, and stability of the HER electrode. Herein, V-doped NiCoP nanosheets on carbon fiber paper (CFP) (denoted as Vx-NiCoP/CFP) were constructed by doping V modulation on NiCoP nanosheets on CFP and used for pH-universal HER. Benefiting from the abundant catalytic sites and optimized hydrogen binding thermodynamics, the resultant V15-NiCoP/CFP demonstrates a significantly improved HER catalytic activity, requiring overpotentials of 46.5, 52.4, and 85.3 mV to reach a current density of 10 mA·cm−2 in 1 mol·L−1 KOH, 0.5 mol·L−1 H2SO4, and 1 mol·L−1 phosphate buffer solution (PBS) electrolytes, respectively. This proposed cation-doping strategy provides a new inspiration to rationally enhance or design new-type nonprecious metal-based, highly efficient, and pH-universal electrocatalysts for various energy conversion systems.

A multiproduct lignocellulosic biorefinery converts various types of biomass into value-added products or energy through different conversion pathways. However, its operation is susceptible to the changing nature of biomass properties, biomass feedstock supply, ambient temperature, and product demands. Therefore, a new optimal resource allocation scheme must be devised instantly upon detecting any fluctuations in the biorefinery to avoid oversupply or undersupply issues. Previous literature on biorefinery resource allocation uses a mainly nonlinear programming approach that assumes steady state for all parameters during simulation; this may result in a delay of response time due to the time taken during the optimization stage. In this paper, a resource allocation system based on deep neural network (DNN) is proposed for the biorefinery. The input nodes of the DNN are the parameters that undergo fluctuations while the output nodes are the flowrate allocation of biomass to different chemical and energy conversion pathways. The connection weights and topology of the DNN are optimized using the neuro-differential evolution (NDE) algorithm. The optimization results of the DNN yields an average optimality of 97.7% and reduces the response time by 99.5% as compared to the conventional nonlinear solver. The proposed DNN-NDE framework accounts for both responsiveness and cost performance during the synthesis of a smart resource allocation system.

Generally, plastics pose a variety of environmental impacts due to their increased use and non-biodegradability. End-of-life treatment is a viable way of recovering energy from plastics while at the same time reducing the amount of plastics disposed of in landfills. This paper studies the environmental impact of Non-Recycled Plastics (NRP)-to-energy processes. Three waste treatment processes were considered for NRP: pyrolysis, waste-to-energy (WtE), and landfill. The environmental impact assessment results indicated that conversion technologies such as pyrolysis and WtE are preferred over landfill. The total energy consumed in the pyrolysis process was 24635.7 MJ/tonne. The conversion technologies have a lower environmental impact and produced net positive energy from NRP. The global warming potential shows that pyrolysis (3.91 kg eq. CO2) contributes the least to global warming than waste-to-energy (18.56 kg eq. CO2) and landfill (17.5 kg eq. CO2). However, sensitivity analysis suggested that the inefficiencies of the current conversion technologies should be addressed. Between the two technologies studied, pyrolysis contributed less environmental burden, having a lower global warming potential, a higher efficiency in energy conversion, and less harmful emissions such as selenium and methane.

In searching for cost-efficient strategies to reduce emissions from energy conversion, most western countries use energy-emission models. In these models, the whole energy conversion chain and possible future options for energy supply and emission reduction are mapped into a network of energy flows. Total discounted cost of energy supply and emission reduction is minimized under the restriction of maximum allowed emissions of SO2, NO x , or CO2. The present paper extends one of these models to allow for fuzzy parameters. Such an extension appears to be useful when the data situation is weak. In this paper, a fuzzy linear program is developed, which has been applied to an energy-emission model of Lithuania.

Programs in the Defense Sciences Office (DSO) at the Defense Advanced Research Projects Agency (DARPA) bridge the gap from fundamental science to applications by identifying and pursuing the most promising ideas within the science and engineering research communities and transforming these ideas into new DoD capabilities. The Department of Defense (DoD) recognizes that our dependence on fossil fuel must be reduced and is actively supporting new technical solutions to this challenge. Moreover, advancements in alternative energy generation and storage technologies will render the warfighter more efficient, capable and mobile. Energy harvesting is a central pathway to solving this critical need. This paper will highlight two DARPA DSO programs which are making significant strides in the advancement in materials to improve energy harvesting technology with a focus on rapid transition to the end user. The Nanostructured Materials for Power (NMP) program is developing high performance thermoelectric materials and devices for energy harvesting with goals of energy conversion of 30%. The Low-Cost, Lightweight Portable Photovoltaics (PoP) program is developing integrated PV technologies with high power conversion efficiency (20%) in a form factor capable of being produced at low cost on flexible substrates. The paper will review the goals of the programs, discuss their implications, and highlight some of the research strategies underway.

Subway transportation is being promoted worldwide to effectively solve urban congestion. However, the vibration induced by subway traffic has caused a major adverse impact on building safety, precision instrument operation and human health. Wave barriers have been proven effective in mitigating ground vibration, whereas they have some limitations in achieving ideal attenuation zone and high efficiency to cover the low-frequency vibration in underground railway system. Based on locally resonant phononic crystals theory, this paper designs three-component locally resonant periodic wave barriers (LRPWBs), and investigates the effects of geometrical and material parameters on the bandgap features in detail. The band structures are calculated using improved plane wave expansion (IPWE), the transmission spectra and vibration modes are obtained by finite element method (FEM). The results indicate LRPWBs are able to give lower and wider bandgap to cover the main frequency of subway environment, which is proved by time and frequency domain analysis. For the bandgap mechanism, the local resonance features of LRPWBs result in the energy conversion between kinetic energy and elastic strain energy, thus the elastic wave energy is localized in resonance unit and then the locally resonant bandgap is created. In addition, the bandgap can be adjusted by carefully selecting proper geometrical and material parameters to actualize low-frequency broadband attenuation. Further studies about multi-oscillator system indicate that the appropriate combination of multiple LRPWBs are conductive to diverse and broad bandgaps. The investigations can provide inspiration for periodic wave barriers design in multi-frequency vibration attenuation field.

The revolution represented by third-generation photovoltaic devices relied on the discovery of various hybrid organic–inorganic perovskite materials to convert solar into electrical energy. One of the advantages of such cells is their low cost due to the raw materials and cheap production methods used. Nevertheless, these cells face several challenges, such as inadequate stability and the hysteresis phenomenon. To overcome these, perovskite solar cell (PSCs) with planar and inverted structures have been utilized with an inorganic hole transport layer (HTL), achieving acceptable efficiency. As there is no closed-form system of equations to describe the operation of such cells, neural networks have been employed for their modeling. In optimization algorithms, the values of the parameters must be swept, since most current simulation tools cannot use them directly. Such software optimization can notably decrease the cost of cell design. This paper presents a practical way to achieve the mentioned aim. In particular, an artificial neural network (ANN) is exploited for the modeling, then an evolutionary particle swarm optimization (E-PSO) algorithm is developed to optimize the structure to achieve the highest efficiency based on searching the energy conversion. The results of the simulations are then employed in SCAPS software to train the neural network. This optimization leads to the achievement of an efficiency of 23.76% for the proposed structure, better than values reported in literature.

Plentiful accessibility of fuels, non-erratic, reliable performance, low maintenance, low cost and high life are the significant factors for solar-PV-powered water pumping scheme for irrigation applications. It is highly used in irrigation system for cultivation where the utility-grid is non-available, hilly areas, forests, etc., by utilizing solar source with energy conversion methodology. However, the performance of overall irrigation scheme relies on energy conversion methodology by using feasible DC–DC converter. In this paper, a novel non-isolated switching cell type DC–DC converter has been proposed for acquiring greater performance of Brushless-DC motor to lift the water from ponds or canal through submersible pump. This observation is clearly presented and validated under steady-state condition by using Xilinx FPGA SPARTAN-6 hardware prototype; results are carried out and compared with various converter topologies.

A novel semi-active vibration control concept with a serial-switch-stiffness-system was previously presented in our work. Differing from conventional vibration control systems, this system does not dissipate but converts vibration energy as potential energy stored in springs and then reacts against external disturbance. As a piecewise linear system, whether or not energy conversion limit happens is an interesting nonlinear dynamic issue related to the systems steady state response. This paper formulates this issue in depth using the approach called equivalence in control. The systems control force represented by the converted vibration energy is approximately decomposed into two portions. One is responsible for low-frequency free response and the other for high-frequency switching response. An equivalent linear system suffering from a decomposed high-frequency switching force is obtained instead of the original switched system. The steady state response of the disturbed system can be delivered through linear superposition as executed in a linear system. Energy conversion limit occurring in the system under a harmonic disturbance is numerically shown by means of fast Fourier transformation. Analytical formulation and numerical simulation for open- and closed-loop control of the system are further carried out, respectively. The results give that the proposed approach is capable of solving the stead state response of the switched system accurately, and meanwhile, energy conversion limit occurs in the vibration control system indeed. Experimental discussion is also executed.

The rapid consumption of fossil fuels has caused increasingly climatic issues and energy crisis, which leads to the urgent demand for developing sustainable and clean energies. Electrocatalysts play a key role in the development of electrochemical energy conversion and storage devices. Especially, developing efficient and cost-effective catalysts is important for the large-scale application of these devices. Among various electrocatalyst candidates, earth abundant transition metal compound (TMC)-based electrocatalysts are being widely and rapidly studied owing to their high electrocatalytic performances. This paper reviews the recent and representative advances in efficient TMC-based electrocatalysts (i.e., oxides, sulfides, selenides, phosphides, carbides and nitrides) for energy electrocatalytic reactions, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Different compounds with different applications are summarized and the relative mechanisms are also discussed. The strategies for developing earth-abundant and low-cost TMC-based electrocatalysts are introduced. In the end, the current challenges and future perspectives in the development of TMC research are briefly discussed. This review also provides the latest advance and outlines the frontiers in TMC-based electrocatalysts, which should provide inspirations for the further development of low-cost and high-efficiency catalysts for sustainable clean energy technologies.

Harvesting ultra-low frequency random vibration, such as human motion or turbine tower oscillations, has always been a challenge, but could enable many potential self-powered sensing applications. In this paper, a methodology to effectively harness this type of energy is proposed using rotary-translational motion and bi-stability. A sphere rolling magnet is designed to oscillate in a tube with two tethering magnets underneath the rolling path, providing two stable positions for the oscillating magnet. The generated magnetic restoring forces are of periodic form with regard to the sphere magnet location, providing unique nonlinear dynamics and allowing the harvester to operate effectively at ultra-low frequencies (< 1 Hz). Two sets of coils are mounted above the rolling path, and the change of magnetic flux within the coils accomplishes the energy conversion. A theoretical model, including the magnetic forces, the electromagnetic conversion and the occurring bi-stability, is established to understand the electromechanical dynamics and guide the harvester design. End linear springs are designed to maintain the periodic double-well oscillation when the excitation magnitude is high. Parametric studies considering different design factors and operation conditions are conducted to analyze the nonlinear electromechanical dynamics. The harvester illustrates its capabilities in effectively harnessing ultra-low frequency motions over a wide range of low excitation magnitudes., Nonlinear Dynamics, 101 (4), ISSN:0924-090X, ISSN:1573-269X

Recent expansions in the emerging technologies have enlarged the consumption of electric power enormously which, conventionally, leads to the installation of power plants of huge capacity. So, to meet the electric power demand, the usage of renewable energy resources has become predominant in the present scenario. Solar photovoltaic energy conversion system that converts solar irradiance directly into electrical energy is a great opportunity among the available renewable energy resources as it is very abundant. In this paper, the key objective is to elucidate the detailed procedure of the maximum power-point tracking process for the solar panel with both stand-alone and grid-connected solar energy conversion system using a boost converter. The proposed system is simulated using MATLAB/Simulink, and comparative analysis shows the better performance of the proposed scheme.

Increasing the generation of renewable energies to reduce the consumption of fossil fuels that produce high concentration of greenhouse gases is the priority that several governments have set for themselves in the medium term. In this paper, the modeling of a solar thermal energy generation plant is carried out. The climatic data correspond to two coastal cities and an island in Ecuador. The main contribution is the simulation of a complete model of solar collector fields and power conversion systems, in which the variables of output temperature and oil flow intervene at the same time. Previous research uses only the outlet temperature to evaluate the power plants. The model of the solar thermal plant is composed of a solar collector field, a storage tank, and an energy conversion system. As a result, a model of a solar thermal plant is obtained that allows to make decisions when considering the incorporation of microgrids in electrical systems isolated. The use of solar thermal technology allows to reduce the risk of spills from the transport of fossil fuels on ships. In addition, the CO2 emissions involved in the construction, operation, and maintenance of a solar thermal power plant are detailed.

Graphene Quantum Dots (GQDs), zero-dimensional nanoparticles which are derived from carbon-based sources owned the new pavement for the energy storage applications. With the varying synthesis routes, the in-built properties of GQDs are enhanced in different categories like quantum efficiency, nominal size range, and irradiation wavelength which could be applied for the several of energy and optoelectronics applications. GQDs are especially applicable in the specific energy storage devices such as super capacitors, solar cells, and lithium-ion batteries which were demonstrated in this work. This paper critically reviews about the synthesis techniques used for the GQDs involving energy storage applications with increased capacitance, energy conversion, retention capability, and stability.

Ocean wave energy conversion as one of the renewable clean energy sources is attracting the research interests of many people. This review introduces different types of power take-off (PTO) technology of wave energy converters. The novelty of this paper is to present advantages and disadvantages of the linear direct and indirect drive PTO devices for ocean wave energy conversion. The designs and optimizations of PTO systems of ocean wave energy converters have been studied from reviewing the recently published literature. The novel mechanical designs of the PTO systems have been compared and investigated in order to increase the energy harvesting efficiency.

The heaving buoy wave energy device is popular for wave conditions with small wave heights and short periods. This paper presents the design of a wave energy converter composed of a gyro buoy, a hydraulic power take-off, and an electricity generation system. The energy accumulators are used to improve the output power with different control strategies. The quantity relations between each component are established using theoretical methods. The simulation model describes the energy conversion and calculates the operation time, energy capacity, and output power of the device under different initial pressures, release pressures, and electric resistances. As a result, the capacity is determined by the electronic load, and the maximum output power can be obtained when the accumulators are turned on and off at the same time. This study investigates the factors influencing the electric energy production and can be used to guide the optimization of this type of device.

Magneto-electro-elastic (MEE) materials have been receiving a special attention from the research community owing to their specialized performance and coupled behavior under thermal, electric, magnetic and mechanical loads. The possibility of prospective energy conversion means, have additionally been added to the cause of researching about these materials. Therefore, the review presented here may be considered as a topical discussion on MEE materials and structures. Through this paper, all critical concepts revolving around MEE materials are discussed in separate sections ranging from the very definition of MEE materials, their material phenomenon, types and properties, to certain fundamental theories and micromechanical models, structural analyses of MEE structures and their nano-sized counterparts, effects of various external and internal parameters and prospective applications of these materials. The present study is in no ways exhaustive to the methods and results observed, but it may be considered as a guide to researchers and scholars about the behavior of MEE materials, wherein critical observations and analyses’ techniques are discussed.

In China, the power industry contributes significantly to carbon emissions, reducing carbon emissions in this industry is conducive to China's adaptation and mitigation of climate change. Researches on green and low-carbon power have attracted increasing attention. In this paper, we analyze and compare the carbon emissions from thermal power sector in 30 Chinese provinces, divided into three main regions. Based on the panel data over the period 2002–2016, we use a slacks-based measurement (SBM) model to measure the carbon emission efficiency of China’s power sector. The results show that the carbon emission efficiency of the system is relatively low, with marked differences among regions. Based on the Moran’s I, we further found spatial heterogeneity in carbon emission efficiency of provincial power sector. Policies for adaptation and mitigation of climate change should have regional differences. Interregional collaboration also plays a key role in adapting to and mitigating climate change. For China, it is an important issue to develop clean coal-fired power generation and vigorously develop renewable energy. From a global perspective, energy transformation needs to be continuously promoted. Promoting low-carbon transformation of global energy system requires deep technical cooperation and synergy. Global mitigation strategy should focus on the orientation of structural reform and constantly optimize the energy structure.

The use of solar energy in the present era is necessary and important as well. Solar chimney technology for power generation is one of the solar energy harvesting techniques where the direct and dispersed solar radiations are absorbed in the solar chimney power plant. The effectiveness of solar chimneys has been proven for power generation, and it is a promising approach to future energy generation plans. This article provides a comprehensive scenario of the research and development of solar energy technology as well as the history of solar chimneys in the last few decades. It describes the state of empirical and theoretical studies and the physical processes for this commonly used technology. Finally, this paper presents some avenues to cover the practical required approaches for solar chimney power generation plant. In this study, the numerical investigation is also considered to study the stack configuration effect on the performance of a solar chimney power plant. Numerical simulation of the proposed configuration shows that the speculated geometry can reduce the throttling effect of the deflected plume.

Wireless capsule endoscopy has the distinctive advantage of providing trustworthy results without substantial discomforts to patients. However, lack of capsule active motion control and energy supply have been significant obstacles preventing wider applications of this technology. To overcome these problems, this paper presents a micro piezoelectric motor with energy harvesting feature. The motor is driven by a single-phase voltage and can be used in capsule endoscopy. The stator was constructed by bonding two PZT plates (PZT1 and PZT2) onto the adjacent outer surfaces of a metal base. PZT1 and PZT2 can both be used to excite the in-plane bending modes of the stator to generate a traveling wave in the stator. The PZT plate supplied with no-exciting voltage source can be used to convert the superfluous vibration energy of stator body into electric energy to power small electronic devices. The elliptical trajectories of points on the stator surface result from a superposition of the two bending modes. The vibration and energy conversion characteristics of the stator were analyzed by using the finite element analysis software ANSYS. The structure parameters of the stator were adjusted until the mode mixture of the stator disappeared. A prototype motor was fabricated and tested to explore its mechanical and electric energy output abilities. The size of the prototype motor is about 9.8×9.2×22.0 mm3. The tested resonance frequencies of the operating modes are 15.305 kHz and 15.815 kHz, respectively. The maximum no-load speed is 85 rpm. The applied single-phase driving voltage is 100 Vo-p (peak voltage) at frequency of 15.54 kHz. The stall torque is 0.98 mN·m, and the maximum output power of the harvesting PZT plate is 127 mW under an optimal equivalent load resistance of 5.16 kΩ.

Prediction of manufacturing equipment’s energy consumption plays an important role in selecting appropriate process parameters for energy saving. However, it is difficult to model the energy consumption of metal forming equipment during the drawing process characterized by variable process parameters and dynamic loads. In this paper, a model was developed to quantify the energy consumption of a typical hydraulic press during the drawing process under a range of operating conditions. The hydraulic press studied consists of two different circuits and two controllable parameters, i.e., punch velocity and blank holder force can be set for drawing processes performed. To start, the energy flow during the drawing process was analyzed by using the energy conversion mechanism and components’ specifications to understand the detailed energy characteristics of each circuit. Then, orthogonal experiments including these two parameters at three levels were designed and carried out to find significant parameters. Finally, the contribution of each parameter, which was obtained from the analysis of variance (ANOVA) of the experimental results, was used to simplify energy flow modeling efforts. Consequently, a model of the press was established and used to predict the energy consumption of the drawing processes with different parameters. Good agreement with the experimental results was observed. The model can be used to identify parameters for minimal energy consumption, while the approach could be adapted to develop an energy consumption model for different hydraulic equipment.

The paper is focused on a very hot topic of SMART materials and their architectures for energy conversion systems designed for conversion of mechanical to electrical energy using the piezoelectric effect. The aim of the study is to increase both the reliability and efficiency of electromechanical conversion compared to standard concepts. Our new design of piezoelectric cantilever is made with multi-layer ceramic composite, where piezoelectric layer BaTiO3 is covered by protective ceramics layers of different residual stresses, where Al2O3 and ZrO2 is used. Utilization of controlled residual stresses into new multi-layer architecture is the key idea and it is crucial for optimal design of the individual layers of the proposed concept. The multi-layer ceramic composite is fabricated by electrophoretic deposition, where the composite is assembled from different ceramic materials during processing and after sintering we get inseparable ceramic laminate consisting of piezoelectric and protective layers of ceramics. This approach of processing multi-layer ceramic material including lead free piezoelectric layers is innovative and has never been published before.