Energy Conversion Rate Research Articles

Relaxation Dynamics of a Granular Pile on a Vertically Vibrating Plate.

Nonlinear relaxation dynamics of a vertically vibrated granular pile is experimentally studied. In the experiment, the flux and slope on the relaxing pile are measured by using a high-speed laser profiler. The relation of these quantities can be modeled by the nonlinear transport law assuming the uniform vibrofluidization of an entire pile. The fitting parameter in this model is only the relaxation efficiency, which characterizes the energy conversion rate from vertical vibration into horizontal transport. We demonstrate that this value is a constant independent of experimental conditions. The actual relaxation is successfully reproduced by the continuity equation with the proposed model. Finally, its specific applicability toward an astrophysical phenomenon is shown.

Study on single raindrop noise and energy conversion

The measurement of rainfall in the ocean is more difficult than in land, but the noise signals produced by rainfall can be used for measuring the rainfall in the ocean. In this paper, a single raindrop measurement system was set up to measure the noise of the raindrop, the bubble sound are classified by the radius of the raindrop which was measured by the splash method. The mechanism of the initial impact and the bubble sound are analyzed, and the kinetic energy threshold and acoustic energy conversion efficiency of the single raindrops are also investigated. The results show that the bubble noise is the main noise compared with initial impact noise, the initial impact noise will become larger with the radius of raindrop, the acoustic energy of great and large raindrop is much larger than that of small one, but the tiny and medium raindrop have no acoustic energy. The kinetic energy threshold is not a constant, but it is proportional to the raindrop size.The acoustic energy conversion rate is about 1.04×10-3% for small raindrops, 10-5% for heavy rains and great raindrops, there are almost no acoustic energy for tiny raindrops and medium-sized raindrops.

Design and Experiment of an 8kJ-pulsed Seismic Source

In this paper, an 8kJ-pulsed seismic source with a closed cavity transducer is designed and the discharge experiment is carried out in which the selected variables are electrode materials, voltage and electrode spacing. We focus on the resistance of the plasma channel and the discharge power. By comparison, the effective power of the output of electrodes in non-metallic materials is larger than that of metallic materials. With the decrease of the voltage, the longer the duration of low resistance is. With the increase of the voltage, the electric energy conversion rate of the discharge plasma is also increased. This study provides the necessary reference for the improvement of the pulsed seismic source.

Dark states and delocalization: Competing effects of quantum coherence on the efficiency of light harvesting systems.

Natural light harvesting systems exploit electronic coupling of identical chromophores to generate efficient and robust excitation transfer and conversion. Dark states created by strong coupling between chromophores in the antenna structure can significantly reduce radiative recombination and enhance energy conversion efficiency. Increasing the number of the chromophores increases the number of dark states and the associated enhanced energy conversion efficiency yet also delocalizes excitations away from the trapping center and reduces the energy conversion rate. Therefore, a competition between dark state protection and delocalization must be considered when designing the optimal size of a light harvesting system. In this study, we explore the two competing mechanisms in a chain-structured antenna and show that dark state protection is the dominant mechanism, with an intriguing dependence on the parity of the number of chromophores. This dependence is linked to the exciton distribution among eigenstates, which is strongly affected by the coupling strength between chromophores and the temperature. Combining these findings, we propose that increasing the coupling strength between the chromophores can significantly increase the power output of the light harvesting system.

Active Dynamics Model with Asymmetric Energy Conversion Rate

We consider an energy depot model with an asymmetric energy conversion mechanism where the energy conversion rate depends not only on the particle’s speed but also on the particle’s direction of motion. The effects of the asymmetric energy conversion on the dynamics are examined, and the dynamic phase diagram is constructed in terms of the energy conversion apparatus and the external forces. We find a new dynamical state in the phase diagram as well as a discontinuous transition among the dynamical phases, which are absent in the symmetric active dynamics model. Moreover, we found a dynamical state with a negative energy conversion rate, which can be applied to the modeling of the energy storage from the work done by external forces as in chemisomosis.

The Propagation of Stress Wave in the PZT-5H Composite Target and the Influence of Load Resistance on the Electrical Output Under the Strong Shock Loading

To introduce the application background the self-powered technology for Fuze bridge fire, high overload microthermal battery activation, rocket ignition, and the aircraft escape actual condition lifesaving system ignition power supply, which intends to use the high-speed impact of piezoelectric ceramic in the process of missile launching high overload pressure or missile and target intersection in the process of high overload stress wave of piezoelectric ceramics and the transformation of power, for closer to confession technology for Fuze bridge ignition, high overload microthermal battery activation, rocket ignition, and aircraft escape system engineering problems. The stress wave propagation in the PZT-5H piezoelectric ceramic composite target and load resistance effect to the electrical output characteristics is investigated under the strong shock loading; the experiments have been performed about cylindrical steel projectiles normal impact on PZT-5H piezoelectric ceramic composite target by using polyvinylidene fluoride stress test system and electrical output test system combining with one-stage light gas gun loading system. The experimental results show that the stress duration and peak stress are about $9~\mu \text{s}$ and 232 MPa, respectively, when the cylindrical projectile impacts on piezoelectric ceramic composite target at the impact velocity of 345 m/s. The outputs of current pulse peak, voltage pulse peak, and energy peak are 20 A, 734 V, and 11 mJ under the stress interactions of 200–300 MPa. At the near-impact stress conditions, the electrical output characteristics of piezoelectric ceramics are greatly affected by the load resistance. The output voltage pulse increases with the increasing of load resistance value, and the values of the load resistance have a significant effect on output energy; output energy conversion rate is up to 82% when the load resistance is $50~\Omega $ .

Complete Targets Coverage in Wireless Sensor Networks With Energy Transfer

This letter considers energy harvesting sensor nodes monitoring multiple fixed targets. The goal is to monitor these targets for the longest time period. A key challenge, however, is that sensor nodes have varying energy harvesting rates, meaning that the coverage lifetime of targets is limited by sensor nodes with low energy. To this end, we consider energy sharing between sensor nodes. We model the problem as a mixed integer linear program (MILP). Advantageously, our MILP models non-linear energy conversion rates. We also outline a heuristic for large-scale networks. Our results show energy sharing and non-linear energy conversion rates prolong coverage lifetime. Finally, our heuristic achieves 90% of the optimal coverage lifetime.

Highly enhanced electromechanical properties of PVDF-TrFE/SWCNT nanocomposites using an efficient polymer compatibilizer

PVDF-TrFE/SWCNT nanocomposites with outstanding electromechanical properties were produced using P3HT-PMMA block copolymers as a compatibilizer between PVDF-TrFE and SWCNT. P3HT-PMMA block copolymer coated SWCNT (PTMCNT) was first prepared to utilize π-π stacking interactions between SWCNT and the P3HT block segment. The obtained PTMCNTs are highly compatible with the PVDF-TrFE matrix due to strong hydrogen bonding interaction between the polymer matrix and the PMMA block segment on the surface of SWCNT, leading to a very low percolation behavior at 0.05 wt% of SWCNT in PVDF-TrFE. The obtained electroactive PVDF-TrFE/SWCNT nanocomposites showed ca. 50 times increased electromechanical thickness strain, ca. 3200 times increased elastic energy density, and ca. 460 times increased electrical-to-mechanical energy conversion rate in comparison to those of pristine PVDF-TrFE at the relatively low electric field (50 Vppμm-1). These outstanding properties result from the ultra-low percolation of SWCNT along with uniform local field distribution in PVDF-TrFE, which kept not only intrinsic properties of PVDF-TrFE such as all-trans formed crystalline phase and softness but also enhanced electrical properties including dielectric constant.

Energy dissipation from two-glass-bead chains under impact

The mechanisms of energy dissipation during the dynamic fracture and fragmentation of granular materials play a significant role in controlling the evolution of geological structures, enhancing the efficiency of industrial comminution and blasting, and reducing the geoenvironmental hazards. In this research, impact tests on two-glass-bead chains accompanied by micro-CT of crushed fragments are performed. The results reveal that only a small portion of the input stress wave energy is dissipated through the fragmentation of the two-bead-chain system and that the energy dissipation efficiency increases with increasing input energy. It is found that generally the glass bead at the back of the chain always experiences more damage regardless of the input stress wave energy level. The micro-CT results show that the fracture energy only accounts for a small portion (0.3%–1.4%) of the chain system absorbed energy. Such a low conversion rate is attributed to the underestimated surface area of the micro-cracks, caused by the finite resolution of the micro-CT. By pursuing a fractal dimension analysis, designed to account for the undetected micro-crack surface area, it is estimated that the energy conversion rate could be increased to 0.7%–5.1%. It appears that friction dissipation appears to always be predominant, in particular during severe fragmentation.

Mechanism of Ultra-Fast Actin-Myosin Sliding Producing Cytoplasmic Streaming in Giant Algal Cell, Studied Using the Centrifuge Microscope

In giant intermodal cells of green algae Chara collaria, cytoplasmic streaming is produced by ATP-dependent sliding between myosin heads extending from amorphous cytoplasmic organelles and actin filament arrays (actin cables) fixed on chloroplast rows. The velocity of cytoplasmic streaming is many times faster than the maximum myofilament sliding in skeletal muscle. In this article, we compared steady-state force-velocity (P-V) relations between cytoplasmic myosin and skeletal and cardiac muscle myosins using the centrifuge microscope, in which myosincoated latex beads were made to slide along the actin cables under various centrifugal forces. In contrast with the hyperbolic P-V relation of actin-myosin sliding in skeletal and cardiac myosins, the P-V relation of cytoplasmic myosin versus actin cable sliding was a straight line, indicating a very large duty ratio and a very small rate of chemomechanical energy conversion. Possible mechanisms of the ultra-fast actin-myosin sliding are discussed.Highlights• The velocity of cytoplasmic streaming, caused by ATP-dependent sliding between cytoplasmic myosin and actin cables in giant algal cells is many times faster than ATP-dependent actin-myosin sliding in skeletal and cardiac muscles.• The mechanism of ultra-fast actin-myosin sliding was studied using the centrifuge microscope, in which beads coated with cytoplasmic myosin were made to slide along actin cables under various centrifugal forces serving as loads against cytoplasmic myosin versus actin cable sliding.• Unlike the hyperbolic force-velocity (P-V) relation of skeletal and cardiac muscle actin-myosin sliding, the P-V relation of cytoplasmic actin myosin sliding was a straight line irrespective of the force generated by cytoplasmic myosin.• These results indicate a very large duty ratio and a very small efficiency of chemo-mechanical energy conversion in cytoplasmic actin-myosin sliding.

Landing Behavior Analysis of Lunar Probe Based on Drop Tests and RFT in a Vacuum

This letter addresses the influences of footpad shape and ground condition on the motion behavior of a lander in a vacuum. To evaluate the influences, we first developed a drop test apparatus that can conduct repeated drop tests in the vacuum chamber. The footpad drop tests were then conducted with various shaped footpads on different surface conditions. Subsequently, the motion behavior of the footpads in a vacuum was modeled, based on the resistance force theory (RFT) and its penetration characteristics were numerically analyzed. The usefulness of the RFT based model was discussed along with the experimental results. Finally, drop tests were conducted using a four-legged lander to comprehensively analyze its landing behaviors. From the footpad drop tests and numerical analysis based on the RFT, we confirmed the following: 1) the force acting on the footpad is enhanced, and the penetration depth is reduced in a vacuum, 2) the force and kinetic energy conversion rate are smallest for the curved footpad, and 3) an increase in the ground density had a relatively small impact on the penetration depth of the footpads in a vacuum. Furthermore, the drop tests using the lander model confirmed that even if some of the lander's footpads land on regolith simulant with different densities, this does not lead to postural imbalance or turnover of the lander in a vacuum.

Thermal Energy Harvesting WSNs Node for Temperature Monitoring in IIoT

As the backbone of industrial Internet of Things (IIoT), wireless sensor networks (WSNs) are generally powered by batteries with limited energy, which constrain the continuous operations of WSNs and IIoT. Energy harvesting is a promising solution for this problem. Industrial plants have many hot pipelines or walls, and the temperature is one of the critical parameters to be monitored in industrial processes. This paper developed a novel thermal energy harvesting WSN node for temperature monitoring in IIoT. The feasibility of the presented self-powered WSN node is experimentally verified for a range of different sleep periods of the device. These results demonstrate that the designed boost circuit has an energy conversion rate of about 27%, and the proposed thermal energy harvester is able to indefinitely power a commercial WSN node when the sleep period of the device exceeds 16 s, which represents a duty cycle of 5.4%.

Design and fabrication of a prototype solar tapping device

Fossil fuel based energy sources are most commonly used because of the ease of availability and affordability, but have many long lasting negative effects, due to which a shift must be made to renewable and clean energy sources such as solar energy. Efficiency of the photovoltaic cells have increased by 1% every ten months, resulting in reduced costs and increased number of users. The project will explore the design and fabrication of an improved and efficient solar tapping device. An effort will be made to incorporate an architectural concept called “barrel vault” that is primarily used for natural lighting, over a Fresnel lens plate setup to act as a collector. The tracking mechanism incorporated is unique and can be modified to either have single axis or dual axis tracking depending on the requirements. Keeping in mind the environment and cost, an attempt has been made to fabricate the product with higher energy conversion rate, at an affordable cost using the above techniques. Upon analysing the results, the conclusion could be drawn that there was an increase in conversion rate of up to twice the traditional setup.

Plasmoid Instability in Forming Current Sheets

Abstract The plasmoid instability has revolutionized our understanding of magnetic reconnection in astrophysical environments. By preventing the formation of highly elongated reconnection layers, it is crucial in enabling the rapid energy conversion rates that are characteristic of many astrophysical phenomena. Most previous studies have focused on Sweet–Parker current sheets, which are unattainable in typical astrophysical systems. Here we derive a general set of scaling laws for the plasmoid instability in resistive and visco-resistive current sheets that evolve over time. Our method relies on a principle of least time that enables us to determine the properties of the reconnecting current sheet (aspect ratio and elapsed time) and the plasmoid instability (growth rate, wavenumber, inner layer width) at the end of the linear phase. After this phase the reconnecting current sheet is disrupted and fast reconnection can occur. The scaling laws of the plasmoid instability are not simple power laws, and they depend on the Lundquist number (S), the magnetic Prandtl number (P m ), the noise of the system ( ), the characteristic rate of current sheet evolution ( ), and the thinning process. We also demonstrate that previous scalings are inapplicable to the vast majority of astrophysical systems. We explore the implications of the new scaling relations in astrophysical systems such as the solar corona and the interstellar medium. In both of these systems, we show that our scaling laws yield values for the growth rate, wavenumber, and aspect ratio that are much smaller than the Sweet–Parker–based scalings.

Representing non-linear wave energy converters in coastal wave models

Abstract To meet the growing global demand for carbon neutral electricity, wave energy is increasingly being identified for its global prevalence and the emerging clean technologies that can harness it. To provide the scale of electricity needed, Wave Energy Converters (WECs) will need to be deployed in large arrays. However, the effects of a WEC array's layout on the surrounding wave conditions in both the near and far fields is poorly understood. The published literature describes numerous methods to model interactions of incident waves and WEC arrays. Yet, none of the published methods provide a methodology which spectrally resolves the individual WEC's energy conversion characteristics, and has the flexibility to be applied to any emerging WEC design. This study develops and implements two novel candidate high-fidelity representations of a Backwards Bent Duct Buoy Oscillating Water Column (BBDB) WEC within a Simulating WAves Nearshore (SWAN) coastal model. Each candidate representation is developed by post-processing time series data generated from a time domain numerical simulation to form a meta-model, referred to as an obstacle case, consistent with the SWAN governing equations and discretization scheme. The study is executed within the framework of SNL-SWAN – a modified version of SWAN that includes a WEC obstacle case that is built on the established concept of using SWAN's transmission coefficient to emulate the wave-WEC interactions. The two new WEC obstacle cases build on SNL-SWAN by considering the WEC's intercepted power, the rate of energy extraction from the waves, instead of the captured power, the rate of energy conversion by the power-take-off. The two new candidates differ in their level of spectral resolution: one homogenizes the intercepted power across the frequency domain while the other attempts to spectrally resolve the energy transfer mechanisms. The two new candidate obstacle cases were compared by considering up to 5 BBDB devices subject to irregular wave conditions. For an individual device, a region of significantly perturbed wave heights, referred to as a wake, stretched 200 m in the lee of the WEC, with the maximum impact on wave heights seen 50 m behind the device. The wake behind five devices is largely dependent on the device spacing. The five unit WEC array only presented decreases of wave height between 0.2 and 0.7 m 200 m behind the last device in the array. A five unit WEC array model showed that estimates of individual WEC power performance was reduced by 2.3% and 6.0% when implementing the two new obstacle cases.

Heat Transfer and Friction Characteristics of Artificially Roughened Duct used for Solar Air Heaters—a Review

Solar air heater uses the energy coming from the sun to heat the air. The conversion rate of solar energy to heat depends upon the efficiency of the solar air heater and this efficiency can be increased by the use of artificial roughness on the surface of absorber plate. Various studies were carried out to analyse the effect of different roughness geometries on heat transfer and friction factor characteristics. The thermo-hydraulic performance of solar air heater can be evaluated in terms of effective efficiency, thermo-hydraulic performance parameter and exergetic efficiency. In this study various geometries used for artificial roughness and to improve the performance of solar air heaters were studied. Also correlations developed by various researchers are presented in this paper.

The Effect of a Guide Field on Local Energy Conversion During Asymmetric Magnetic Reconnection: Particle‐in‐Cell Simulations

AbstractWe use theory and simulations to study how the out‐of‐plane (guide) magnetic field strength modifies the location where the energy conversion rate between the electric field and the plasma is appreciable during asymmetric magnetic reconnection, motivated by observations (Genestreti et al., 2017). For weak guide fields, energy conversion is maximum on the magnetospheric side of the X line, midway between the X line and electron stagnation point. As the guide field increases, the electron stagnation point gets closer to the X line, and energy conversion occurs closer to the electron stagnation point. We motivate one possible nonrigorous approach to extend the theory of the stagnation point location to include a guide field. The predictions are compared to two‐dimensional particle‐in‐cell (PIC) simulations with vastly different guide fields. The simulations have upstream parameters corresponding to three events observed with Magnetospheric Multiscale (MMS). The predictions agree reasonably well with the simulation results, capturing trends with the guide field. The theory correctly predicts that the X line and stagnation points approach each other as the guide field increases. The results are compared to MMS observations, Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) observations of each event, and a global resistive‐magnetohydrodynamics simulation of the 16 October 2015 event. The PIC simulation results agree well with the global observations and simulation but differ in the strong electric fields and energy conversion rates found in MMS observations. The observational, theoretical, and numerical results suggest that the strong electric fields observed by MMS do not represent a steady global reconnection rate.

Emission properties of suprathermal electrons produced by laser–plasma interactions

AbstractSuprathermal electrons produced by laser–plasma interactions at 0.53-μm laser wavelength have been investigated using 19 electron spectrometers. The targets were 2- and 10-μm-thick Al foils, while the laser average intensities were 2 × 1013 and 7 × 1014 W/cm2. A double temperature distribution was observed in the electron energy spectrum: the lower electron temperature was below 25 keV, whereas the higher was ~50 keV. The angular distribution of the total suprathermal electron energy approximately obeyed the Gaussian distribution, peaking along the k vector of the incident laser beam for perpendicular incidence. Furthermore, the conversion rate of laser energy into escaped suprathermal electron energy over the π sr solid angle was ~10−4 at $\sim \!\!10^{14} \; {\rm W}/{\rm c}{\rm m}^{\rm 2}$, increasing almost linearly with the laser intensity.

Evaluation Method for the Firm Power Escalation of a Wind-Storage Hybrid Power System

To improve the controllability of the electric power output and the economic performance of a large-scale wind farm, an auxiliary energy storage system is required. This paper deals with the rule of planning reasonable energy storage power and capacity based on the historical annual mean wind speed data, the probability density of the pulsating wind power output, and the warranted firm power provided by the wind farm. Specifically, the evaluation index of the fluctuation degree of the firm power is defined in order to optimize the planned energy storage capacity. After that, the firm power escalation affected by the energy storage power and the conversion rate of the storage device are quantitatively evaluated. All of these analyses contribute in a significant way towards determining the acceptable energy conversion rate with the condition of limited energy storage space of a wind-storage hybrid power system. The proposed evaluation method of the firm power escalation is verified by MatLab simulation results.

Regimes during single water droplet impacting on hot ethanol surface

In order to deepen the knowledge of the mechanisms of liquid pool fire suppression with water mist/spray, a series of preliminary experiments were carried out for a water droplet impacting upon target liquid surface. Ethanol was chosen as the target liquid and heated to simulate the temperature conditions as it burned. The water droplet used in the experiments was about 2.0mm with impact Weber number altering from 30 to 695. The results show that three typical impact regimes including crater-jet, penetration and surface bubble are observed. The pool temperature and Weber number have important influences on the impact behaviors and characteristic parameters including the crown height, and the energy conversion rate during the crater evolution and jet evolution. The maximum crown height depends on Weber number but is weakly dependent on the pool temperature. The ratio of the sum of crater potential energy and surface energy to initial impact energy is linearly related to the dimensionless pool temperature. Likewise, for the cases of crater-jet, as the Weber number and pool temperature increase, the conversion rate of crater potential energy and surface energy to jet potential energy and surface energy increases linearly.