Energy Conversion Rate Research Articles

Numerical analysis of hydroenergy harvesting from vortex-induced vibrations of a cylinder with groove structures

The energy generated by vortex-induced vibrations is studied through numerical simulation, and the vibration characteristics of the energy-harvesting device are studied using a bidirectional coupled fluid-structure simulation. The energy collector consists of an elastic cylinder with symmetrical grooves, which can effectively improve the energy extraction performance. The studied range of Reynolds numbers is 15 000 to 100 000 (1.86 <U*water< 11.63). The performance of the energy collector can be significantly affected by modifying various parameters of the grooved structure. Moreover, changing the damping ratio ζn will also affect the energy harvesting. The results show that the grooves affect the dynamic response of the structure; the structure will gallop when the angle between the grooves and the inflow direction is α = 30°. For a grooved cylinder with α = 30° or 60°, the effective power Pharn of the system can be effectively increased, and the grooves can also effectively increase the energy conversion rate ηviv; especially in the case of structure galloping, more energy can be collected, and Pharn and ηviv can be dramatically increased. Immediately after the structure has entered the lock-in region, ηviv reaches its maximum. Varying ζn has little effect on the amplitude of the conductor, but it can effectively enhance energy harvesting and energy conversion.

Feasibility of Wireless Horse Monitoring Using a Kinetic Energy Harvester Model

To detect behavioral anomalies (disease/injuries), 24 h monitoring of horses each day is increasingly important. To this end, recent advances in machine learning have used accelerometer data to improve the efficiency of practice sessions and for early detection of health problems. However, current devices are limited in operational lifetime due to the need to manually replace batteries. To remedy this, we investigated the possibilities to power the wireless radio with a vibrational piezoelectric energy harvester at the leg (or in the hoof) of the horse, allowing perpetual monitoring devices. This paper reports the average power that can be delivered to the node by energy harvesting for four different natural gaits of the horse: stand, walking, trot and canter, based on an existing model for a velocity-damped resonant generator (VDRG). To this end, 33 accelerometer datasets were collected over 4.5 h from six horses during different activities. Based on these measurements, a vibrational energy harvester model was calculated that can provide up to 64.04 μW during the energetic canter gait, taking an energy conversion rate of 60% into account. Most energy is provided during canter in the forward direction of the horse. The downwards direction is less suitable for power harvesting. Additionally, different wireless technologies are considered to realize perpetual wireless data sensing. During horse training sessions, BLE allows continues data transmissions (one packet every 0.04 s during canter), whereas IEEE 802.15.4 and UWB technologies are better suited for continuous horse monitoring during less energetic states due to their lower sleep current.

Charged porous asymmetric membrane for enhancing salinity gradient energy conversion

Abstract Salinity gradient energy is an abundant renewable energy source that can help satisfy the growing global demand for energy. Although current approaches based on membrane design for salinity gradient energy conversion have been demonstrated to improve conversion efficiency they suffer from the trade-off between selectivity and intrinsic resistance of the membranes, which impedes the rates of energy conversion. In this study, a charged porous asymmetric membrane was fabricated, consisting of a thin charged nanopore (~1 nm) layer and a charged porous structure (80–100 nm) layer. Its asymmetric electric potential and charged porous structure increase its affinity to uniport of ions and enables high ion conductivity. While maintaining a high degree of selectivity, the membrane exhibited an intrinsic membrane resistance of 0.53 ± 0.12 Ω·cm2, which was lower than that of the commercial and other reported membranes. The maximum power density reached up to 12.5 W/m2 with a 500-fold salinity gradient. This membrane shows great promise in industrialization and provides new insights into high salinity energy conversion.

A safe and efficient bioactive citrate-lysine/miRNA33 agonist nanosystem for high fat diet-induced obesity therapy

The increased prevalence of obesity is recognized as a serious public health problem affecting millions of people. Although some anti-obesity drugs are currently licensed for use, these drugs involve diverse side effects such as diarrhea, vomiting, and low efficiency. Here we developed a safe and efficient biomaterials-based anti-obesity nanosystem (PCG-EPL/miR33agonist), which was formed with poly (citric acid)-glycerol-polylysine (PCG-EPL) and miR33 agonist by self-assembly. The PCG-EPL could efficiently load, protect and deliver the miR33 agonist into the adipocytes and decreased the obesity-related IL-1β expression in adipocytes in vitro. The high-fat diet induced obese rat model experiment showed that the PCG-EPL/miR33agonist via caudal vein injection effectively reduced the body weight by enhancing lipid metabolism and decreasing the inflammatory factors expressions (IL-1β, TNF-α and IL-6) in vivo, without suppressing the appetite of rat. Compared with the obese mice, mice in PCG-EPL/miR33 had higher average food intake but lower energy conversion rate. PCG-EPL/miR33agonist significantly inhibited the growth of adipocytes. Noteworthy, this weight loss strategy is not only safe and efficient, but also does not need diet control. Thus, PCG-EPL may serve as an ideal platform for RNA drug delivery in anti-obesity therapy, especially for those who need to lose weight but unable to autonomously control their diet.

High-Resolution Modeling of Semidiurnal Internal Tidal Waves in the Laptev Sea in the Ice-Free Period: Their Dynamics and Energetics

The QUODDY-4 three-dimensional finite-element hydrostatic model has been used to reproduce the spatial distributions of dynamic and energetic characteristics of the internal tidal waves (ITWs) of the Laptev Sea in the ice-free period. It has been shown that one distinctive feature of ITW amplitudes at the pycnocline depth is that the area with relatively high ITW amplitudes is limited. The peak amplitudes reaching at least 5 m have been detected only in the central part of the sea near the continental slope, but the ITW amplitudes in the western and eastern parts of the sea do not exceed 0.2 and 0.1 m, respectively. Like ITW amplitudes, the baroclinic tidal velocities are expressed mainly in the central part of the sea and almost vanish in its western and eastern parts. The presence of a zone of high baroclinic velocities near the northern open border of the sea and an increase in velocities with approaching the coast of the continent at the mouth of the Lena River is noted. The fields of components of the averaged (over a tidal cycle) baroclinic tidal energy budget (integrated by depth) are discussed. The averaged (over the sea area) values of the density of baroclinic tidal energy, as well as the tidal energy conversion and dissipation rates, are $$1.2\,\, \times \,\,{{10}^{3}}$$ J/m2, $$ - 0.3\,\, \times \,\,{{10}^{{ - 3}}}$$ W/m2, and $$7.3\,\, \times \,\,{{10}^{{ - 3}}}$$ W/m2, respectively. The ITW lifetime in the Laptev Sea, defined as the ratio of the average density of baroclinic tidal energy to the dissipation rate, is around 50 h; i.e., the ITW lifetime in the sea is 4 times higher than the tidal cycle length for the M2 tidal harmonic.

Theoretical elucidation of the energy conversion rate in organic photovoltaic cells of the fullerene nanostructure derivatives. A density functional theory study

A comparative theoretical study of the kinetics of the Diels–Alder (DA) reaction between empty fullerene (C[Formula: see text]) and lithium ion encapsulated fullerene ([Formula: see text]) with 1,3 cyclohexadiene (C[Formula: see text]H[Formula: see text]) was carried out. This reaction takes place in a photovoltaic cell. The effect of the encapsulated [Formula: see text] ion on the conversion rate of solar energy into electricity has been highlighted through calculations based on the density functional theory (DFT). In addition, a static study using the global conceptual DFT indices, as part of the demonstration of the significant electrophilic power of the fullerene nanostructure, was carried out to show the effect of encapsulating the [Formula: see text] ion in this nanoparticle on the electrophilic power of Li[Formula: see text]@C[Formula: see text] and therefore on the acceleration of the reaction. The relationship between the HOMOdonor–LUMOacceptor energy difference and the DA reaction acceleration, and therefore the acceleration of light conversion (a rapid conversion implies a small gap), has been thoroughly examined. Moreover, a mechanistic study of the kinetics of the DA reaction of the fullerene involved in an organic photovoltaic cell has been carried out. In this section, a concerted synchronous mechanism with no effect of [Formula: see text] encapsulation on the synchronicity of the reaction was observed. Finally, it was revealed that Li[Formula: see text]@C[Formula: see text] reacted approximately 2466 times faster than C[Formula: see text]. Moreover, the experimental results were found in good agreement with the computer calculations.

Metal Organic Frameworks Modified Proton Exchange Membranes for Fuel Cells.

Proton exchange membrane fuel cells (PEMFCs) have received considerable interest due to their low operating temperature and high energy conversion rate. However, their practical implement suffers from significant performance challenge. In particular, proton exchange membrane (PEM) as the core component of PEMFCs, have shown a strong correlation between its properties (e.g., proton conductivity, dimensional stability) and the performance of fuel cells. Metal-organic frameworks (MOFs) as porous inorganic-organic hybrid materials have attracted extensive attention in gas storage, gas separation and reaction catalysis. Recently, the MOFs-modified PEMs have shown outstanding performance, which have great merit in commercial application. This manuscript presents an overview of the recent progress in the modification of PEMs with MOFs, with a special focus on the modification mechanism of MOFs on the properties of composite membranes. The characteristics of different types of MOFs in modified application were summarized.

Ion-scale Current Structures in Short Large-amplitude Magnetic Structures

Abstract We investigate electric current structures in Short Large-Amplitude Magnetic Structures (SLAMS) in the terrestrial ion foreshock region observed by the Magnetospheric Multiscale mission. The structures with intense currents ( ) have scale lengths comparable to the local ion inertial length (d i). One current structure type is a current sheet due to the magnetic field rotation of the SLAMS, and a subset of these current sheets can exhibit reconnection features including the electron outflow jet and X-line-type magnetic topology. The d i-scale current sheet near the edge of a SLAMS propagates much more slowly than the overall SLAMS, suggesting that it may result from compression. The current structures also exist as magnetosonic whistler waves with f ci &lt; f &lt; f lh, where f ci and f lh are the ion cyclotron frequency and the lower-hybrid frequency, respectively. The field rotations in the current sheets and whistler waves generate comparable and energy conversion rates. Electron heating is clearly observed in one whistler packet embedded in a larger-scale current sheet of the SLAMS, where the parallel electric field and the curvature drift opposite to the electric field energize electrons. The results give insight about the thin current structure generation and energy conversion at thin current structures in the shock transition region.

Static magnetic field enhanced methane production via stimulating the growth and composition of microbial community

Corn stover has a potentially valuable use as a substrate for biogas production by anaerobic fermentation. Preprocessing of corn stover, such as alkali pretreatment, is usually needed to increase substrate availability. In this study, an experimental biogas production system using a flat circular permanent magnet with a central hole to provide a static magnetic field (SMF) was devised to increase biogas production from corn stover substrate, without pretreatment, by anaerobic fermentation. The effects of varying SMF intensity on the growth of microbe populations in the activated sludge were not linear. Optimal SMF intensity was found to be 11.4 mT (±2%). At this level, the number of microbe populations increased by 85.5% compared to the control. Total gas production and CH4 content of SMF were 19.5% and 20.0% higher than those from the control NMF (no magnetic field). SMF influenced the composition of the bacterial population and significantly increased the percentage of methanogenic archaea in the overall microbe population compared to NMF. Archaea of the order methanocellales were the principal methanogenic archaea found in the decay stage. Our results indicate that SMF can potentially increase biogas production by converting agricultural waste into energy. Life cycle analysis showed that the conversion rate of chemical energy in corn stalks to CH4 was 15.2%.

Annual versus semi-annual eddy kinetic energy variability in the Celebes Sea

Eddy kinetic energy (EKE) in the Celebes Sea (CS) is investigated using a global, eddy-resolving, ocean general circulation model (OGCM) output. The OGCM simulation shows that a strong EKE is confined in the upper 300-m layer. The period of EKE variability varies with depth. In the 0–100-m layer, EKE has a distinct annual cycle that is strong in winter (December–February) and weak in summer (June–August). However, in the 100–300-m layer, semi-annual variation is dominant, which shows stronger EKE in spring and fall and weaker EKE in summer and winter. An eddy energy budget analysis reveals that the barotropic eddy energy conversion rate has a vertical structure similar to that of EKE. Compared to the barotropic eddy energy conversion rate, the baroclinic eddy energy conversion rate is much smaller and does not match the EKE vertical pattern. The budget analysis indicates that the variation in EKE in the CS is governed by barotropic instability of the background circulation. Further analysis reveals that the variation in the regional background circulation with depth is due to a combination of the forcing of the local monsoon and the Mindanao Current (MC) in the western tropical Pacific.

Power generation performance of a bench-scale reverse electrodialysis stack using wastewater discharged from sewage treatment and seawater reverse osmosis

In this study, we evaluated steady state power generation performance of a bench-scale RED stack with an effective membrane area of 40 m2 under different flow rate conditions using brine discharged from a seawater desalination plant and water discharged from a sewage treatment plant. Constant current operation was enabled to evaluate the steady state power output of the stack as the salt concentration profile inside the stack approached equilibrium. In addition, external current loading allowed for measurements of respective resistance of the stack, including membrane resistance, solution compartment resistance with spacers, and the resistance of each electrode; these measurements allowed for an estimation of the intrinsic stack performance when the electrode resistance was negligible. The evaluation of energy conversion efficiency revealed that 25–66% of the salinity gradient energy (SGE) was consumed in the stack and converted to electricity with a conversion efficiency of 17–26%. Furthermore, energy conversion analysis while considering the SGE loss due to both salt leakage and electrode reaction showed an energy conversion rate of 50%. Finally, the existence of flexible membrane deformation was proposed under different flow rates to obtain higher net power output. The obtained results are promising for use in full-scale RED implementation.

Interactions of Multiple Biological Fields in Stored Grain Ecosystems

Biological entities such as fungi in stored grain evolve and interact with the environment in similar fashions as physical fields. An experiment was conducted to study the behavior of the biological field of fungi in stored grain, as well as the interactions between the biological field of fungi and the physical fields of temperature and moisture. A framework of the biological field is presented to describe biological systems in which multiple biological entities co-exist and interact among themselves and with the surrounding environment. The proposed biological field describes the spatio-temporal distribution of a biological entity and its ability of influencing (or being influenced by) the surrounding biotic and abiotic entities through exchange of energy, matter, and/or information. The strength of a biological field of fungi was quantified as the rate of energy conversion by fungi from grain starch to heat. The experimental data showed that the strength of biological field of fungi in stored grain varied in both space and time, with the maximum field strength of 120–133 W m−3 occurred at the location where the biological field of fungi interacted strongly with the temperature and moisture fields.

Motion simulation and performance analysis of two-body floating point absorber wave energy converter

As an important structure for utilizing wave energy, the two-body floating point absorber (FPA) wave energy converter has a simple structure, high energy conversion rate, and wide frequency response range. In this paper, a heave motion model of two-body FPA wave energy converter was established. On this basis, the secondary development of AQWA software programming in Fortran language was conducted by reckoning in the power take-off (PTO) effect, and the motion simulation of the two-body FPA wave energy converter was realized. For the specific oscillating two-body FPA model, the study analysed the frequency domain hydrodynamic performance and the time domain motion characteristics of the device. The results showed that the numerical model was adequate to predict the motion performance of the two-body FPA. The maximum value of the heaving response amplitude operator (RAO) was reached with the frequency of 0.7–0.8 rad/s. As the wave period increased, the generated power of the two-body FPA initially increased and subsequently decreased. The stiffness coefficient has less effect on the generated power than the damping coefficient. The results and conclusions have reference significance for the development of new wave energy devices and the efficient and reliable utilization of wave energy.

Reducing light reflection by processing the surface of silicon solar cells

This study discussed a surface processing technique for improving the energy conversion rate of solar cells with silicon as the substrate. The technique involves texturing the surface of a silicon substrate and coating it with an antireflective layer to enhance its antireflective property and thereby its photoelectric conversion efficiency. Double surface texturing (DST) texture was formed through photolithography and anisotropic wet etching, and radio frequency magnetron sputtering was performed to deposit the SiO2/TiO2 double-layer antireflective coating to reinforce the surface texture of a silicon solar cell. Subsequently, a scanning electron microscope was employed to analyze the DST texture before and after the surface was coated with a double-layer antireflective coating (ARC). An UV–VIS spectrophotometer attached with an integrating sphere was then applied to measure the light absorption rate of the processed surface at different wavelengths. After optimum DST and double-layer ARC treatments, the average reflectance within the visible light reduce to 9.94%, which means the absorption of incident light into the absorption layer was enhanced to improve the energy conversion efficiency of silicon solar cells.

A strategy of using recycled char as a co-catalyst in cyclic in-situ catalytic cattle manure pyrolysis for increasing gas production

Cattle manure is a major livestock waste in agroecosystem, and in-situ catalytic pyrolysis is considered as a potential technology for its disposal. In order to increase the gas production during cattle manure pyrolysis and alleviate the problem of frequent regeneration-separation of the in-situ catalyst, a strategy of in-situ catalytic pyrolysis was proposed in this work, in which the pyrolytic char product was not separated from the pyrolysis catalyst of NiO/γ-Al2O3 but mixed with it and recycled for several times as the co-catalyst for cattle manure pyrolysis instead. Adopting this strategy, it was observed that the mixed-type catalyst could lead to 70% increase in gas production and 82% promotion in syngas energy conversion rate compared with the circumstance of no catalyst added. Through different means of characterization, it was found that there are synergistic effects between char and NiO/γ-Al2O3, which enhance the catalytic performance of catalyst. On one hand, during the pyrolysis process, char can translate NiO into Ni that has higher cracking activity through in-situ reduction. On the other hand, due to its rich porous texture and large pore volume, char can act as an additional adsorbent for the reactants. Based on the experimental results of this work, the proposed strategy of cyclic in-situ catalysis with the recycled char as the co-catalyst can be a promising scheme in the practical biomass pyrolysis process for gas production.

Numerical and experimental investigations of melting process of composite material (nanoPCM/carbon foam) used for thermal energy storage

Abstract Paraffin wax is considered as stable and environmentally convivial phase change materials (PCM) for thermal energy storage systems (TESS). However they suffer to low thermal conductivity which reduced the rate of heat storage and energy conversion, as well as the leakage of materials during the melting process. In this paper, nanocomposites consisting of a paraffin / graphite mixture embedded in carbon foam by vacuum impregnation were prepared in the aim to develop a new formulation of phase change material (PCM) with excellent shape stabilization, thermal conductivity improved and exceptional thermal reliability. Different tests such as Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermal conductivity analyzer are proposed to determine thermal properties of the composite PCM. After the validation of numerical model with experimental results, the numerical analysis is extended to investigate the melting process of the composite PCM under constant temperature. A regular three-dimensional (3D) foam structure was designed. The effects of carbon foam porosity and nanoparticles’ volume fraction on the thermal behavior of composite PCMs were investigated. The results show that the addition of both graphite and carbon foam to paraffin wax enhance the thermal properties and prevent the leakage of the melted paraffin which preserve its stable thermal performance. This is due to the conductive network path created by the 3D structure of the carbon foam and the percolation of graphite, which might facilitate an increased phase change speed of composite PCM.

Moderate drought followed by re-watering initiates beneficial changes in the photosynthesis, biomass production and Rubiaceae-type cyclopeptides (RAs) accumulation of Rubia yunnanensis

Roots and rhizomes of Rubia yunnanensis are important Chinese medicine materials with significant anti-tumor activity, which is mainly obtained from wild resources. There is an urgent need to develop the production practice for the cultivation of R. yunnanensis. The current study was performed to investigate the changes in the photosynthetic pigment content, photosynthetic characteristics, chlorophyll fluorescence parameters, biomass production, and secondary metabolites Rubiaceae-type cyclopeptides (RAs) contents in roots and rhizomes by drought and re-watering in R. yunnanensis grown in four water conditions: well-watered control (C), moderate drought (MD), severe drought (SD), and re-watering after moderate drought (RMD). The results indicated that compared with the control, drought stresses (MD and SD) significantly decreased photosynthetic pigments and impaired photochemical efficiency, as revealed by the reductions of maximum potential PSII efficiency (Fv/Fm), effective quantum yield of photochemical energy conversion (Yield) and electron transport rate (ETR), etc., resulting in limited photosynthetic capacity, and hence reduced biomass accumulation and RAs contents and yields in roots and rhizomes. The RMD plants could produce compensation effect and their photosynthetic ability recovered to control level; they showed the comparable dry biomass of roots and rhizomes and higher contents and yields of RAs compared with the control. This implied that moderate drought-induced injury in R. yunnanensis was reversible. These results reinforce the importance of water management and recommend the re-water operation for the cultivation of R. yunnanensis.

Characteristics of thermoacoustic conversion and coupling effect at different temperature gradients

The thermoacoustic engine that can convert heat into sound offers a promising methodology of energy usage. However, the low energy conversion rate limited the exploitation of this technology. To obtain high acoustic power and energy outputs, effects of temperature gradients on thermoacoustic characteristics were numerically investigated in this study. The results indicated that temperature gradients had significant impacts on the output sound pressure and heat flux. Meanwhile, complicated coupling effects among the temperature, fluid velocity and sound pressure were observed during the thermoacoustic oscillations. Deep insight into the phase changes implied that the temperature difference would initiate the oscillations of the fluid movement and induce the sound pressure afterwards. The study also demonstrated that large temperature differences and abrupt temperature changes were favorable for the acoustic power output.

Experimental study of the mechanical, energy conversion and frictional heating characteristics of locking sections

Experiments on sandstone specimens are conducted to investigate the mechanical, energy conversion and frictional heating characteristics of locking sections in two types of large-scale rockslides. The flaw geometry of the conceptual model is a combination of two preexisting flaws and a locking section. A deep insight into the failure mechanism of locking sections is gained by using digital image correlation (DIC) technology, thermal imaging technology, and thermodynamics theory. Two different types of failure patterns are reproduced in our experiments: the retaining wall type and step-path type, which are shear and tensile in nature, respectively. The results obtained by DIC measurements demonstrate that the failure process of a locking section is a progressive development of strain localization zones, which actually reflects the displacement discontinuity when a crack propagates. The variance and differentiation rate are defined to provide differentiation and precursory information on the deformation and fracturing process of a locking section. From the energy point of view, the strain energy conversion (accumulation, dissipation and release) during loading significantly influences the failure pattern of the locking section. The faster the post-peak conversion rate of strain energy, the more violent is the post-peak fracturing behavior of the locking section. A strong positive correlation is found between the post-peak conversion rate of strain energy and the brittleness index. Furthermore, thermal imaging technology is applied to describe the frictional heating behavior. The correlation among the failure pattern, energy conversion, and thermomechanical response is analyzed. The frictional heating phenomenon is related to the shear failure, and a fast post-peak conversion rate of strain energy occurred along the locking section.

The plasma enhanced surface reactions in a packed bed dielectric barrier discharge reactor

The conversion and utilization of CO2 is one of the greatest global challenges. Plasma assisted catalysis provide a new resolution to this problem. However, the energy efficiency and conversion rates of the plasma process are still insufficient for industrial applications. The key reasons are the highly complex interaction between gaseous plasma and catalytic materials, especially in packed bed dielectric barrier discharges. Our study fills this critical gap by developing a novel numerical approach to study how the ns pulse driving plasma trigger the heterogeneous reactions on the Ni/γ-Al2O3 catalyst surface. The development of plasma inside the reactor is in the form of surface ionization wave (SIW) + filamentary microdischarges. The high electron power in the SIW region and the high ion power density in the sheath region on the catalysts surface provide enough energy to trigger heterogenous reactions. The heterogeneous reactions not only generate the local high CO density region near the Ni/γ-Al2O3 surface, but also increases the space averaged density of CO. The extension of activation time of catalytic material can significantly increase the conversion efficiency of CO2.