Energy Conversion Rate Research Articles

Near-Field Enhancement in SPASER Nanostructures for High-Efficiency Energy Conversion

We present in this study a theoretical investigation of the near-field enhancement phenomenon within nanostructures, which have garnered recent attention due to their potential applications in sensing, imaging, and energy harvesting. The analysis reveals a significant intensification of electromagnetic fields proximal to periodically arranged arrays of gold nanoparticles sustaining a highly lossy mode. In addition to the existence of a localized surface plasmon (LSP) mode exhibiting suboptimal quality, our investigation unveils intricate aspects of near-field enhancement closely correlated to the dynamics of lasing mechanisms. Notably, our investigation is focused on elucidating the augmentation’s behavior across varying pumping energies. The achieved enhancement surpasses two orders of magnitude compared to the passive counterparts. We introduce a description of the energy conversion rate specific to the SPASER configuration. The conceptualized SPASER reveals a significant promise. It showcases energy conversion efficiency up to 80%, emphasizing the SPASER’s potential as a highly effective nano-scale energy source.

Deformation mechanism and damage energy evolution of coal body under different gas pressures based on the energy principle

With increasing mining depth, the coal pillars of a coal mine will be in a stressful environment characterized by high gas pressures and unidirectional loading. To investigate the damage evolution characteristics and energy evolution mechanism of coal pillars loaded in a gas pressure environment, a uniaxial compression test was performed on a coal body under different gas pressures using a load testing apparatus for gas-containing coal rocks. The obtained results showed that the mechanical properties of the coal body varied with the gas pressure. Specifically, the peak strain, compressive strength, and elastic modulus decreased with increasing gas pressure; the higher the gas pressure, the lower the conversion rate of the elastic strain energy in the elastic deformation stage of the coal body and the lower its total input energy. With increasing gas pressure, the damage threshold of the coal body decreased, whereas the damage variable corresponding to the peak value, as well as the damage threshold value, increased. According to the theory of continuous damage mechanics, an ontological damage model of the coal body under different gas pressures was established based on the principle of minimum energy dissipation, and the rationality of the model was verified through a comparison between the theoretical and experimental data. Our findings can be useful in ensuring the safety of coal mining in terms of preventing gas disasters.

Performance enhancement of a photovoltaic-thermal system: comprehensive analysis of thermal and electrical efficiency using CuO and Ag nanofluids

This study investigates the performance enhancement of a photovoltaic-thermal (PV/T) system through the incorporation of CuO and Ag nanofluids, aiming to optimize both thermal and electrical efficiencies. The research compares three different working fluids: pure water, water with CuO nanoparticles, and water with Ag nanoparticles. Experimental data were collected from Khenchela, Algeria, which is characterized by a wide range of temperatures throughout the year, providing an ideal environment to evaluate the performance of the PV/T system under realistic conditions. The results show significant improvements in thermal management, particularly when using nanofluids, with silver nanoparticles demonstrating the most substantial effect on heat transfer. This enhanced thermal conductivity allows for better cooling of the photovoltaic cells, reducing the temperature-related losses and improving energy conversion rates. The study underscores the potential of nanofluid technology as a novel approach to boost the overall performance of PV/T systems by enhancing their heat transfer capabilities. These findings contribute to the ongoing development of more efficient, sustainable solar energy solutions and highlight the role of nanofluids in advancing high-performance solar technologies for the future.

Design optimization and active control of unsteady flow in large-scale annular linear induction pumps

This study addresses the issue of unstable flow in large-scale annular linear induction pumps (ALIPs), with a focus on optimizing their design and enhancing performance. Utilizing the ALIP model developed by Toshiba Corporation as a reference, the design process employs the equivalent circuit method to improve the hydraulic performance of high-flow ALIP systems. A comparison of various hydraulic and excitation structure parameters facilitated the identification of an optimal design scheme. A numerical simulation of the ALIP’s internal magneto-fluid coupling field was then conducted, based on magnetohydrodynamic (MHD) theory. The simulation results were validated against experimental data, confirming the model’s accuracy. Further simulations under various operational conditions were performed to analyze the distribution and magnitude of the axial Lorentz force (FL) and the axial pressure gradient across different flow rates and currents. The analysis indicated that the unstable flow primarily results from inverse pressure gradients, which are caused by the uneven distribution of these forces. To mitigate this issue, the study proposes the addition of a regulating coil winding to the inner stator. This addition significantly reduces the uneven distribution of magnetic fields and pressure gradients. These coils generate a compensating magnetic field that enhances FL within the electromagnetic section, thereby improving the axial force on the magnetic fluid. The results demonstrate that this active regulation method markedly reduces unsteady flow phenomena, stabilizes fluid movement, and offers a novel design strategy for large-scale ALIP systems. The ratio of the area of the regulating coils to that of the driving coils is only 0.33, which minimally increases the pump dimension. Additionally, the energy conversion rate of different regulation currents between the inner and outer regulation coils was compared. It was found that variations in the regulation current alter the total efficiency of the ALIP by no more than 1%, indicating that the control coil winding consumes minimal energy and that the stability of the magnetic fluid can be effectively controlled, making this approach feasible for engineering applications.

Evolution characteristics of shock wave in microsecond-scale underwater electrical wire explosion

The underwater electrical wire explosion (UEWE) is a physical phenomenon initiated by the rapid injection of electrical energy, triggering an explosive event. UEWE offers advantages in energy conversion efficiency, repeatability, and controllability, making it valuable in various industrial applications. Building upon established zero-dimensional (0D) and one-dimensional (1D) models, this paper proposes an enhanced 0D-1D coupled cold-start model to describe the plasma channel expansion and subsequent shock wave (SW) propagation characteristics. The model comprises two submodules: a 0D magnetohydrodynamics model that describes plasma channel boundary expansion during the explosion, and a 1D hydrodynamics model using an artificial viscosity algorithm to depict SW propagation. The constructed numerical model facilitates investigation of plasma characteristics, SW propagation behavior, and energy conversion efficiency throughout the UEWE process. Additionally, the influences of wire dimensions and discharge frequency on these characteristics were analyzed. The results indicate that SW propagation characteristics are primarily governed by thermal pressure variations within the wire and that different wire dimensions markedly affect SW amplitude, attenuation, and impulse. The efficiency of electrical-to-SW energy conversion remains relatively low; however, thicker and shorter wires can enhance SW amplitude and improve conversion efficiency. Higher discharge frequencies produce greater impact forces and impulses near the explosion site, while also improving energy conversion rates. This study offers a theoretical basis and technical guidance for prospective engineering applications.

Superinertial Internal Tides Propagating along the Coast: Dynamics and Energetics Revealed through Topographic Modes

Abstract Internal tides are an important energy source for diapycnal mixing in the ocean interior. Subinertial internal tides are known to have a cross-sectional structure that is baroclinic in deep areas but more barotropic in shallower areas, making the conventional barotropic–baroclinic decomposition ineffective to separate internal tides from surface tides. To address this issue, Tanaka introduced a “topographic mode” which represents internal motions with a barotropic vertical structure and proposed a new energy diagram enabling us to quantify the generation of subinertial internal tides. Here, the applicability of this new energy diagram to superinertial internal tides at various latitudes is investigated by idealized numerical experiments with uniform surface tides passing over a continental slope with a bump in the coastline. The calculated results show that both the topographic and baroclinic modes are generated over the bump and propagate downstream along the coast, inseparably forming a topographically modified internal Kelvin wave whose cross-sectional structure closely resembles that obtained by solving a two-dimensional eigenvalue problem for a superinertial frequency. The energy conversion rate from the surface mode to the topographic mode is about half of the energy conversion rate from the surface mode to the baroclinic mode when the tidal frequency is slightly superinertial and maintains a nonnegligible contribution even when the tidal frequency is substantially superinertial. The findings of this study indicate that the new energy diagram can be applied seamlessly across the critical latitudes and possibly provides a global distribution of the internal tide generation significantly larger than the previous estimates. Significance Statement Quantifying the generation of internal tides is essential for accurate climate modeling, since they are a major energy source of vertical mixing in the ocean. It is known that diurnal internal tides change their characteristics poleward of 30° latitude, where their motion is dominated by horizontal rotation rather than vertical oscillation. This study demonstrates that a recently proposed energy diagram for quantifying the generation of diurnal internal tides poleward of 30° latitude is also effective equatorward of 30° latitude. This is because the rotational motion remains significant even equatorward of 30° latitude, being a fundamental component of the internal tides over a sloping seafloor. The application of this energy diagram will improve the global estimate of internal tide generation.

Bouncing dynamics of a droplet impacting onto a superhydrophobic surface with pillar arrays

A superhydrophobic surface (SHS) patterned with pillar arrays has been demonstrated to achieve excellent water repellency and is highly effective for self-cleaning, anti-icing/frosting, etc. However, the droplet impact dynamics and the related mechanism for contact time (tc*) reduction remain elusive, especially when different arrangements of pillar arrays are considered. This study aims to bridge this gap by exploring a droplet impinging on an SHS with square pillar arrays in a cuboid domain. This fluid dynamics problem is numerically simulated by applying the lattice Boltzmann method. The influences of the droplet diameter (D*), the Weber number (Wew), and the pillar spacing and height (s* and h*) on the droplet dynamics and tc* are investigated. The numerical results show that the droplet can exhibit different bouncing patterns, normal or pancake bouncing, depending on Wew, s*, and h*. Pancake bouncing usually occurs when Wew ≥1.28, h*≥1, and s* ≈ 1, yielding a small tc*. Among all cases, a small tc* can be attained when the conversion rate of kinetic energy to surface energy (ΔĖsur*) right after the impacting exceeds a critical value around 0.038. This relation broadens that given in A. M. Moqaddam et al. [J. Fluid Mech. 824, 866–885 (2017)], which reported that the large total change of surface area renders small tc*. Furthermore, the maximum impacting force remains nearly the same in all cases, regardless of the bouncing patterns.

Enhancing Energy Harvesting Efficiency from Ambient Sources through Advanced Materials and Nanotechnology

The utilization of ambient energy sources for powering small-scale electronic devices and sensors has garnered significant attention due to its potential for sustainable and autonomous operation. This research focuses on enhancing the efficiency of energy harvesting from ambient sources, such as vibrations, heat differentials, and electromagnetic fields, through the integration of advanced materials and nanotechnology into energy harvesting systems. The study begins with a comprehensive review of existing energy harvesting technologies, highlighting their limitations in terms of efficiency, scalability, and adaptability to various ambient energy sources. It identifies the key challenges faced in achieving high energy conversion rates and explores the potential of advanced materials and nanoscale structures to address these challenges. One aspect of the research involves the development and characterization of novel materials with superior energy conversion properties. This includes the synthesis of piezoelectric materials for vibration energy harvesting, thermoelectric materials for heat-to-electricity conversion, and nanomaterials for enhancing electromagnetic energy harvesting efficiency. Advanced characterization techniques, such as scanning electron microscopy (SEM) and X-ray diffraction (XRD), are employed to analyze the structural and electrical properties of these materials. Furthermore, the study investigates the design and fabrication of nanostructured energy harvesting devices optimized for specific ambient energy sources. This involves the integration of nanoscale components, such as nanostructured electrodes, into energy harvesting systems to improve energy capture and conversion rates. Finite element analysis (FEA) simulations and experimental testing are conducted to evaluate the performance and efficiency of these nano-enhanced energy harvesting devices under real-world conditions. The research also addresses the optimization of energy harvesting system parameters, including resonance tuning, impedance matching, and energy management circuits, to maximize energy extraction and utilization. Computational modeling techniques, such as multiscale modeling and finite element simulations, are utilized to optimize system configurations and improve overall energy harvesting efficiency. Overall, this research contributes to the advancement of energy harvesting technologies by leveraging advanced materials and nanotechnology, paving the way for sustainable and autonomous power generation from ambient energy sources for a wide range of applications.

Droplet detachment from a vertical filament with one end clamped

Understanding whether a droplet adheres to or detaches from a flexible filament upon axial impact is of significant interest, particularly in the context of raindrop impact on natural surfaces. This process involves dynamic buckling followed by mode coarsening, dissipating the initial droplet kinetic energy and converting the remaining into elastic energy of the filament. To elucidate this phenomenon, we construct two phase diagrams, one while fixing the filament height and the other the droplet diameter. Notably, we observe that the energy conversion rate is inversely proportional to a Cauchy number, defining the transition between attached and detached droplet in the filament length–falling height diagram. This enables us to derive an expression for the critical falling height as a function of the filament parameters, accounting for the energy conversion rate, which emerges as a key factor for droplet detachment. Published by the American Physical Society 2024

Impact of the Out‐Of‐Plane Flow Shear on Magnetic Reconnection at the Flanks of Earth's Magnetopause

AbstractMagnetic reconnection changes the magnetic field topology and facilitates the energy and particle exchange at magnetospheric boundaries such as the Earth's magnetopause. The flow shear perpendicular to the reconnecting plane prevails at the flank magnetopause under southward interplanetary magnetic field conditions. However, the effect of the out‐of‐plane flow shear on asymmetric reconnection is an open question. In this study, we utilize kinetic simulations to investigate the impact of the out‐of‐plane flow shear on asymmetric reconnection. By systematically varying the flow shear strength, we analyze the flow shear effects on the reconnection rate, the diffusion region structure, and the energy conversion rate. We find that the reconnection rate increases with the upstream out‐of‐plane flow shear, and for the same upstream conditions, it is higher at the dusk side than at the dawn side. The diffusion region is squeezed in the outflow direction due to magnetic pressure which is proportional to the square of the Alfvén Mach number of the shear flow. The out‐of‐plane flow shear increases the energy conversion rate , and for the same upstream conditions, the magnitude of is larger at the dusk side than at the dawn side. This study reveals that out‐of‐plane flow shear not only enhances the reconnection rate but also significantly boosts energy conversion, with more pronounced effects on the dusk‐side flank than on the dawn‐side flank. These insights pave the way for better understanding the solar wind‐magnetosphere interactions.

Energy Conversion Associated with Intermittent Currents in the Magnetosheath Downstream of the Quasi-Parallel Shock

Using the data from the Magnetospheric Multiscale (MMS) mission, we studied the energy conversion between electromagnetic fields and particles (ions and electrons) in a spacecraft rest frame inside a turbulent magnetosheath downstream of the quasi-parallel shock. The results show that the energy conversion was highly intermittent in the turbulent magnetosheath, and the perpendicular electric fields dominated the energy conversion process. The energy conversion among the electromagnetic fields, ions, and electrons was related to the current intensity. In the region with weak current, the ions gained energy from electromagnetic fields, while the electron energy was released and transferred into electromagnetic fields. In contrast, in the intense current region, the energy of ions was transferred into the electromagnetic fields, but the electrons gained energy from electromagnetic fields. The results quantitatively established the relationship between energy conversion rate and current density and revealed that the energy conversion among the electromagnetic fields, ions, and electrons was related to the local current intensity inside the shocked turbulence.

Impact regimes of a single water droplet impacting a hot immiscible liquid surface

Impact regimes of a single water droplet impacting a hot immiscible liquid surface

Enhancing corn stover to bio-jet fuel process: Valorizing lignin-enriched residue for energy, economic, and environmental benefits

Enhancing corn stover to bio-jet fuel process: Valorizing lignin-enriched residue for energy, economic, and environmental benefits

Cu-doped ZnCdS-based photocatalyst for efficient photocatalytic hydrogen production by photothermal assistance

Cu-doped ZnCdS-based photocatalyst for efficient photocatalytic hydrogen production by photothermal assistance

A Marine Experiment Using Dielectric Elastomer Generators and Comparative Study with Actual Measured Values and Theoretical Values

Power generators using dielectric elastomer (DE) transducers are inexpensive, highly efficient, lightweight, stackable, and also easy to install. Therefore, it is considered optimal for an eco-energy society and is attracting attention as a renewable energy device. In particular, DE wave power generators are characterized by the fact that it is not limited by the direction and size of waves, which is a problem with existing wave power generation. This paper presents an accurate method for measuring the energy generated by a DE generator (DEG) and compares it with the theory value obtained by calculation. The electrode materials actually used in this study were a variety of carbon-based materials (including muti-wall carbon nanotube (MWCNT) and singe-wall carbon nanotubes (SWCNT)), and the performance of DEs using these materials was compared. Furthermore, ocean experiments in actual sea areas using DEG were also conducted, and the energy conversion rate was calculated based on the electrical results. Received: 30 May 2024 | Revised: 12 July 2024 | Accepted: 31 July 2024 Conflicts of Interest The authors declare that they have no conflicts of interest to this work. Data Availability Statement Data available on request from the corresponding author upon reasonable request. Author Contribution Statement Seiki Chiba: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration, Funding acquisition; Mikio Waki: Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization.

Mechanical properties of rice husk ash and glass powder concrete: Experimental and mesoscopic studies

Mechanical properties of rice husk ash and glass powder concrete: Experimental and mesoscopic studies

Predicting the economic feasibility of solar-based net-zero emission buildings (NZEBs) in the United States non-residential sector

Predicting the economic feasibility of solar-based net-zero emission buildings (NZEBs) in the United States non-residential sector

Numerical Analysis of Dynamic Characteristics of an Asymmetric Tri-Stable Piezoelectric Energy Harvester under Random Vibrations in Building Structures

This study presents a novel design for a tri-stable piezoelectric vibration energy harvester with an asymmetric structure, which is enhanced with an elastic base (TPVEH + EB), meticulously designed to enhance energy extraction from irregular vibrations in architectural structures. The cornerstone of this design is the asymmetric tri-stable piezoelectric cantilever beam, distinctively arranged within a U-shaped block and fortified with an elastic foundation. A carefully positioned spring (kf)-mass (Mf) system between the U-shaped block and the beam’s fixed end significantly boosts the vertical displacement of the beam during oscillations. Utilizing Lagrange’s equations, we formulated a dynamic model for the asymmetric TPVEH + EB, examining the effects of potential well asymmetry, the stiffness of the elastic base and spring-mass system, the mass of the spring-mass system, and the tip magnet mass on the system’s nonlinear dynamic responses. Our results demonstrate that the asymmetric TPVEH + EB significantly enhances energy harvesting from low-amplitude random vibrations (1.5 g), with the output voltage of the asymmetric TPVEH + EB increasing by 30% and the output power by 25%. Extensive numerical and theoretical analyses verify that the asymmetric TPVEH + EB provides a highly efficient solution for scenarios typically hindered by low energy conversion rates. Its reliable performance under varied and unpredictable excitation conditions highlights its excellence in advanced energy harvesting applications. The improvements detailed in this research underscore the potential of the asymmetric TPVEH + EB to boost energy harvesting efficiency, particularly in powering wireless sensor nodes for structural health monitoring in buildings. By overcoming the limitations of traditional harvesters, the asymmetric TPVEH + EB ensures enhanced efficiency and reliability, making it an ideal solution for a wide range of practical applications in diverse environmental conditions within buildings.

Spontaneous near-inertial wave generation from mesoscale eddy: Energy transformation

The energy transformation between inertial oscillations (IOs), near-inertial waves (NIWs), and mesoscale eddies during spontaneous NIW generation is analyzed by the kinetic energy equations of the multiple temporal–spatial scale interaction between slow and fast motions and then quantitatively estimated by numerical simulations. The evolution of perturbed quasi-geostrophic mesoscale eddies is accompanied by IOs. The nonlinear interaction of IOs and mesoscale eddies results in spontaneous energy transfer from mesoscale eddies to NIWs. However, IOs act as catalysts in the spontaneous NIW energy transformation process, because there is no energy transfer between NIWs and IOs for longer than one inertial period and NIW energy is entirely transferred from mesoscale eddies. The energy conversion rate (ECR) from a propagating eddy to NIWs is significantly enhanced by the resonance of NIWs and the nonlinear coupling of IOs and mesoscale eddies during the spontaneous NIW generation. The time-averaged NIW ECR from a propagating an anti-cyclonic mesoscale eddy (AE) is approximately 5.725 × 10−6 Wm−2 and nearly 16 times higher than those from the standing AE. The magnitude of global near-inertial kinetic energy generated spontaneously from mesoscale eddies is approximately on the order of 2 GW. Therefore, the spontaneous adjustment of mesoscale eddies is a non-negligible NIW generation mechanism and plays a crucial role in the process of supplying energy from mesoscale eddies to the diapycnal mixing in the ocean interior.

An enhanced transfer learning based on addernet and deep domain confusion for prognostic of proton exchange membrane fuel cells

An enhanced transfer learning based on addernet and deep domain confusion for prognostic of proton exchange membrane fuel cells