Energy Loss Research Articles

Nonlocal-in-time finite-velocity diffusion approach on a ring.

The ubiquitous telegrapher's equationis presented in the context of a non-local-in-time master equationon the lattice. From the exact solution of this transport equation, for different hopping models, the second moment in the infinite lattice and the time evolution of the probability in the ring have been analyzed as a function of the two characteristic timescales appearing in the memory kernel of the finite-velocity approach: the rate of energy loss and the timescale characterizing the jumping process in the lattice. We have demonstrated how these timescales characterize the constraint to find positive solutions, the time variation of entropy and therefore the approach to the disordered stationary state on the ring. This lattice model provides an analytic treatment. Thus, this result is relevant in the study of Shannon entropy, transport of information, and waves in lattices and sheds light on the functional role of the loss of energy in the finite-velocity diffusion dynamics.

Characteristics of wave loading and viscous energy loss of a bottom-sitting U-OWC wave energy device: A validated numerical perspective

This study involves numerical simulations of regular waves interacting with a bottom-sitting circular OWC wave energy converter with a U-shaped duct (circular U-OWC). A numerical wave tank is built based on the RANS equation and is validated against experiments. The effect of water depth and the height of the outer tube of the U-shaped duct on capture efficiency, wave loading, and viscous energy loss is investigated numerically. Results show that the height of the outer tube of the U-shaped duct has a significant effect on the capture efficiency of the device. Wave loading analysis reveals a critical mode of stability that may threaten the operation safety of the device. It is found that increasing the height of the U-shaped duct opening increases the viscous energy loss inside the U-shaped duct. A semi-theoretical model between work done by waves to the device and the viscous energy loss in the U-shaped duct is established, numerical data indicates that a significant amount of work done by waves to the device is lost in viscous effects. This suggests that certain optimization for reducing wave loading could possibly also reduce viscous energy loss, thus improving the overall efficiency of the device.

Hierarchical porous structure design and water activation in hydrogels containing hyperbranched peach gum polysaccharide for efficient solar water evaporation

Solar-powered interfacial evaporation is a developing and sustainable technique increasingly utilized in desalination and wastewater purification. This technology involves the creation of cellulose nanofiber (CNF)/polylactic acid (PLA) composite aerogels through the Pickering emulsion approach. Self-floating aero-hydrogel (E-VGP) with a hierarchical porous structure was formed on a viscous mixture containing polyvinyl alcohol (PVA), peach gum polysaccharide (PGP), and polypyrrole (PPy) via an in-situ polymerization process. Furthermore, by modifying the hydrolysis time of PGP with a hyperbranched polyhydroxy structure, VGP hybrid hydrogels of varying microscopic molecular sizes were produced. Additionally, solar vapor generators (SVG) with diverse macroscopic structures were fabricated using molds. The V8G4-12hP0.2 hybrid hydrogel, synthesized using PGP hydrolyzed for 12 h, exhibited an evaporation enthalpy of water at 1204 J g−1. This capacity effectively activates water and enables low enthalpy evaporation. Conversely, the macrostructural design allows the cylindrical rod raised sundial-shaped structure of SVG3 to possess an expanded evaporation area, minimize energy loss, and even harness additional energy from its nonradiative side. Consequently, this micro-macrostructural design enables SVG3 to attain an exceptionally high evaporation rate of 3.13 kg m−2 h−1 under 1 Sun exposure. Moreover, SVG3 demonstrates robust water purification abilities, suggesting significant potential for application in both desalination and industrial wastewater treatment.

Analysis of film cooling and flow resistance characteristics of turbine blades with thermal barrier coatings

This paper employs numerical simulation to investigate the influence of thermal barrier coatings' (TBCs) thickness and surface roughness on the cooling and flow resistance characteristics of turbine blades. The results indicate that the application of TBCs significantly enhances the surface cooling efficiency of the blades. Turbine blades coated with a 0.4 mm thickness of TBC compared to blades without thermal barrier coatings, the average cooling efficiency of the blade surface increases by 12.3 %, and the maximum temperature drop at the leading edge(LE) is 317.8 K. However, the small increment in TBCs thickness leads to an increase in aerodynamic losses in the vane passage. The static pressure coefficient continuously decreases in the suction side(SS) within the interval 0.3 < x/C < 1.0. The average flow coefficient of the film holes exhibits distinct variations in different regions of the blade. As surface roughness increases, the cooling efficiency on the SS and pressure side(PS) of the blade decreases, while the heat transfer enhancement at the LE and cooling efficiency improve. Compared to a smooth coated surface, when the surface roughness height increases to 20 μm, the blade surface cooling efficiency decreases by 1.12 %, and the average temperature rise is 10.3 K. Simultaneously, the energy loss coefficient and total pressure loss coefficient in the vane passage rise with the increase in surface roughness, while the variation in the average flow coefficient of the film cooling holes remains relatively small.

MPPT control strategy of photovoltaic based on improved zebra optimization algorithm

Abstract According to the power generation principle of solar cells, the mathematical model analysis of photovoltaic cells shows that in order to maintain the maximum output power, the work of photovoltaic cells needs to be maintained at the maximum power point. Energy issues are global concerns, and the rational utilization of renewable energy is key to solving these problems. Solar energy, the most readily available source of energy, is characterized by its cleanliness, renewability, and permanence, meeting the requirements for new energy generation. This paper, addressing the shortcomings of the traditional particle swarm algorithm, proposes an MPPT based on an improved zebra optimization algorithm. This strategy is designed to decrease the energy loss during oscillation processes and increase convergence speed. Its performance advantages are also verified through simulation.

Influence of gate cutoff effect on flow mode conversion and energy dissipation during power-off of prototype tubular pump system

Understanding the cutoff effect of gates is essential for enhancing the overall quality of the pump system's power-off process, minimizing energy losses, and reducing potential risks associated with hydraulic transients. In this study, both numerical simulations and experimental investigations were conducted on the power-off process of a tubular pump system, considering scenarios with and without gate functionality. The simulations utilized a dynamic mesh method to model gate movement, incorporated the torque balance equation to determine the real-time impeller speed, and applied the 3D-VOF method for free surface modeling in reservoirs. Power-off experiments were performed on a model pump system and a prototype pump system to validate the numerical simulation results. To elucidate the mechanism of the gate's cutoff effect, flow modes during the power-off process were categorized based on the four-quadrant static test results of the pump, revealing the deviations between transient and static characteristics. By comparing the transient flow structures of the pump system under different gate operating states, specific energy dissipation behaviors during gate cutoff were analyzed. The research findings enhance the understanding of hydraulic transients, which is essential for developing more sustainable and resilient energy systems.

Heat-dynamics network model and energy analysis of a miniature free piston Stirling cryocooler for application of high operating temperature infrared detector

High Operating Temperature (HOT) infrared detectors with a miniature Stirling cryocooler, operating at 150 K and above, will become smaller size and more popular in applications with the development of infrared detector technology. In this paper a miniature free-piston Stirling cryocooler (FPSC) is developed for the application of HOT infrared detectors. Allowing for the active properties of the regenerator, actual thermal process in each chamber of the Stirling cryocooler, and the heat-dynamic coupling, the two-port network model is derived for each component of the FPSC, and then a heat-dynamics network analysis model is established for the entire cryocooler. Meanwhile, the performance prediction with the experimental verification is performed for the cryocooler prototype developed. Then analyses of energy losses are carried out, and the studied results shows that main loss for the expander of miniature cryocooler is ascribed to the non-ideal heat transfer of the regenerator. For the miniature cryocooler prototype developed, the cooling capacity of 1.35 W@150 K is achieved, at room temperature of 23°C and the input power of 10 WAC. The relative Carnot efficiency of the prototype is 13.5%, and the maximum input power is 20 WAC and the weigh is 200 g. The achieved performance is quite appropriate for the application of high operating temperature infrared detectors.

A novel tensor-based modal decomposition method for reduced order modeling and optimal sparse sensor placement

Data-driven modal decomposition methods have become fundamental algorithms in constructing reduced order models (ROMs), which serve as a critical tool in the digital twin modeling of large complex systems. Classical modal decomposition methods are particularly adept at handling matrix-form input data that contains columnized snapshots without retaining spatial structure and neighborhood information. Focusing on addressing this problem, this paper proposed a Tensor-Based Modal Decomposition (TBMD) method to deal with the high-order tensor-form input data. TBMD method is effective in finding the potential low-order manifolds of a given high-order dynamical system with low energy loss within fewer decomposited modes. Moreover, TBMD is extended to be used in the field of optimal sensor placement via the development of a tensor-based QR factorization method and a tensor-based compressive sensing algorithm. The tensor-based QR factorization method is able to consider the spatial structure and neighborhood information of the basis matrices data in tensor form. This is the first time that a compressive sensing model has been discussed and solved for the frontal slice-wise product of a tensor and a vector. Subsequently, comprehensive case studies are conducted based on the cylinder wake dataset, airfoil vortex dataset, sea surface temperature dataset, eigenfaces dataset and turbulent channel flow dataset. The experiment results show that TBMD can accurately capture lower-order manifolds, and the tensor-based QR factorization is effective in optimizing sensor placement with fewer sensors while maintaining high reconstruction accuracy. The proposed methods in this paper is promising to be utilized in the construction of large-scale complex system digital twins, in which TBMD can serve as a fundamental algorithm in constructing ROM.

A mechanical TiAl/TiAlN multinanolayer coating model based on microstructural analysis and nanoindentation

A finite element model reproducing the mechanical behaviour during nanoindentation tests on Ti0.67Al0.33/Ti0.54Al0.46N multilayer coatings was developed. Coatings with two different nanoperiods (10 and 50 nm) were deposited by radio-frequency magnetron sputtering from a single sintered titanium/aluminium target using the reactive gas pulsing process. X-ray diffraction and transmission electron microscopy confirmed the multilayer stacking of the coatings. The finite element models of coatings with these two stacking periods were built considering successive hypotheses: equal thicknesses for metal and nitride nanolayers stacked without transition layer, equal thicknesses stacking with a transition layer between each metal and nitride nanolayer and finally imbalanced thicknesses stacking with a transition layer. The elastic and plastic properties of the stacked nanolayers were determined on thick monolithic coatings of metal and nitride using indentation testing and the finite element model updating method respectively. The elastic-plastic properties of the interface were introduced in the multilayer model as a rule of mixtures of the metal and nitride properties using two hypotheses: parallel or serial. For 50 nm-period film, the interface has a negligible effect on the overall indentation response. On the other hand, for the 10 nm period, the imbalanced stacking model with precise knowledge of the transition layer thickness obtained by N K-edge electron energy loss spectroscopy is required to reproduce the experimental indentation curve. Compared to classical analytical models accounting for hardness, not only the hardnesses but also the indentation moduli appear to be well predicted and evaluated in this work.

Hierarchical ultra-thin porous Co3O4 nanosheets derived from mixed phase α- and β-Co(OH)2 for high sensitivity and ppb-level acetone sensing

Addressing the energy loss of carriers during transmission and achieving high sensitivity detection of target gases facilitates the synthesis of trace-level acetone sensors, which is of great significance in the fields of air quality early warning, health monitoring, and industrial safety monitoring. Here, we propose a strategy where, under hydrothermal conditions, the content of mixed-phase α- and β-Co(OH)2 is regulated by varying the protonation level of 2-methylimidazole in different solutions, leading to the formation of porous monocrystalline Co3O4 microflower structure. The microflower is assembled from ultrathin nanosheets, and the 3D-interconnected macroporous and mesoporous structure provides high surface area and gas diffusion channels. The monocrystalline and two-dimensional structures favor high carrier mobility, enhancing the signal-to-noise ratio. Furthermore, the thickness of the Co3O4 nanosheets is less than twice the Debye length, making their electrical properties completely dependent on surface. DFT calculations also indicate that the few layers Co3O4 model is conducive to acetone adsorption. The Co3O4 sensor exhibits exceptional gas sensing performance towards acetone, with favourable sensitivity (16.83 to 10 ppm), selectivity, and stability, as well as an ultra-low practical detection limit of 10 ppb. Rich point defects and line defects play a significant role in improving the surface activity of the sensitive material as well. This research offers a pathway for designing sensors with exceptional gas sensitivity by employing a straightforward method to control the morphology of sensitive materials, combined with defect engineering to enhance sensing activity.

Computational study of the structural, mechanical, electronic, optical and thermal properties of BaLiX (X =P, As, Sb) perovskites

This study explores the structural, optical, mechanical, electronic, and thermal characteristics of ionic semiconductor compounds BaLiX (X = P, As, Sb) using Density Functional Theory (DFT). A comprehensive analysis of BaLiX (X = P, As, Sb) is conducted, proving that the estimated and observed lattice parameters coincide well and confirming mechanical stability through elastic stiffness constants. Electronic band structures reveal direct bandgap semiconductor properties with values of 0.70 eV, 0.30 eV, and 0.95 eV for BaLiP, BaLiAs, and BaLiSb, respectively, suggesting specific applications such as mid-infrared photodetectors, terahertz devices, and near-infrared sensors. Optical property analyses, including energy loss function, reflectivity, refractive index, and absorption coefficient, highlight the potential of these materials for optoelectronic and photovoltaic applications. Despite elastic anisotropy, optical anisotropy remains minimal. The materials exhibit potential for use as thermal barrier coatings (TBC) due to their comparatively lower Debye temperature (D), minimum thermal conductivity (Kmin) and lattice thermal conductivity (kph). Moreover, heat capacity calculations and thermal coefficient of expansion are also calculated.

Numerical study on combustion and energy efficiency characteristics of thermophotovoltaic-thermoelectric two-stage utilization system filled with porous media

Addressing the issues of low energy conversion efficiency and unstable combustion at the micro-scale resulting from significant energy loss in micro-energy systems, this paper proposes a two-stage utilization system integrating thermo-photovoltaic-thermoelectric technology filled with porous media. The research explored the impact of the placement, thickness, and porosity of porous media on both combustion and energy efficiency within a two-stage utilization system. Performance evaluation indexes such as temperature distribution, pressure drop loss, output power, and efficiency revealed the combustion characteristics of porous media at the micro-scale. The results indicate that the mean outer wall temperature of MTPV increases by 174.3 K as the porous media transitioned from a partially filled to a fully filled state. After comprehensive consideration of various factors, the optimal layout parameter for porous media is determined to be a two-stage uniform filling of porous media (SS304 with a porosity of 0.86 and a thickness of 14 mm). Consequently, the two-stage combustion system achieves an output power of 14.88 W and an energy conversion efficiency of 7.33 %.

A DFT study of the CaMg2As2 material for photovoltaic applications

The research focused on investigating the structural, elastic, electronic, optical, and thermoelectric characteristics of the CaMg2As2 compound. To inspect these properties, the density functional theory (DFT) method has been applied via the Wien2K code. The electronic analysis revealed that the CaMg2As2 compound demonstrates semiconductor behavior with an indirect band gap of 1.781 eV. Additionally, its elastic properties were examined, revealing a 1.980 % AVR, indicating a variation in elasticity depending on the direction of load or stress applied. We have also studied various optical properties of CaMg2As2, including the refractive index, extinction coefficient, electron energy loss, dielectric tensor, and optical conductivity. the absorption coefficient value is zero for energy levels below 2.60 eV, meaning there is no energy absorption by the material at lower energy levels. However, as the energy surpasses 2.60 eV, the absorption coefficient increases and shows multiple peaks. This signifies that as the incident radiation's energy increases, the material starts absorbing more energy at specific energy levels. In addition, one significant finding is that the thermal conductivity of the lattice (κL) in CaMg2As2 decreases exponentially as the temperature rises. This means that as the material gets hotter, its ability to conduct heat becomes less effective. In simple terms, the material becomes less efficient at transferring heat at higher temperatures. These findings suggest that CaMg2As2 has potential as a thermoelectric material with interesting properties that deserve further investigation.

First-Principles insights to probe structural and opto-electronic properties of [formula omitted] (Y=Mg, Sr) halide perovskites with variety of DFT methods

This study reports the structural, electronic, optical, phonon, thermodynamic and thermoelectric properties of AgYF3 (X=Mg, Sr) for photovoltaic and energy applications. We performed first principles calculations using full potential linearized augmented plane wave, FP-LAPW method implemented in Wien2k. The generalized gradient approximations of Perdew–Burke–Ernzerhof PBE-GGA, and PBE revised for solids, PBEsol, is employed for structural optimization of these lead free halide perovskites. The Birch–Murnaghan energy volume curve fitting comprehend the structural stability. The optimized lattice constant of AgMgF3 and AgSrF3 obtained with PBE-GGA(PBEsol) is 3.99(3.92)Å and 4.42(4.65)Å. The stability is further tested with the help of formation energy and positive phonon dispersion curves calculations. For the calculations of explicit electronic and optical properties, we also employed Trans-Blaha modified Beck–Johnson (TB-mBJ) and Strongly Constrained but Appropriately Normed, SCAN, exchange and correlations functionals. The electronic band gap of AgMgF3 computed with PBEsol, TB-mBJ and SCAN is 1.96 eV, 5.25 eV and 2.59 eV exhibiting M-Γ indirect band gap. The band gap energy of AgSrF3 is 2.06 eV, 6.42 eV and 2.70 eV with PBEsol, TB-mBJ and SCAN. The indirect band gap nature of AgSrF3 is confirmed by PBEsol and TB-mBJ while it anticipated direct band gap behavior with meta GGA SCAN. Different optical parameters like dielectric constant, optical conductivity, energy loss function, absorption, reflectivity and refractive index are calculated to assess optical activity of both perovskites. Comprehensive electronic and optical analysis advocates the utility of AgMgF3 and AgSrF3 for different applications is solar technology and optoelectronic devices.

Modeling the Effect of Material Properties on Liquid-Alkaline Water Electrolysis

Liquid-alkaline water electrolyzers (LAWEs) use electricity to drive the conversion of water to H2 and O2 gas. These devices benefit from the use of low-cost nickel electrodes and metal-oxide separators, but suffer from lower current densities and higher cell voltages than proton-exchange-membrane water electrolyzers. Identifying the inefficiencies that result in this poor performance is key to mitigating losses and optimizing LAWEs. Here, we report an experimentally-validated 1-D continuum model of a LAWE that elucidates the gradients within the cell, simulates H2 crossover, and projects the energy improvements made possible by modulating the properties of the electrodes and separator. The model captures the Nernstian polarization losses and the distribution of gas- and liquid-phases within the electrodes, enabling quantification of energy losses associated with kinetic, ohmic, and bubble-induced (mass-transport) resistances. Simulations demonstrate that LAWE can achieve energy intensities of 50 kWh kg−1 of H2 at 1 A cm−2 using improved electrode and separator properties.

Study of the eddy currents effect in Spinning rotor Gauge

The Spinning Rotor Gauge (SRG) serves as a crucial tool in metrology as a secondary standard vacuum gauge. However, its lower measurement limit is not solely determined by background gas molecular friction damping but is also affected by other contributing factors, collectively termed residual damping. This paper investigates the influence of eddy currents on residual damping. It quantitatively analyzes the electromagnetic torque and eddy current heating power induced within the rotor’s interior and surface, calculates the corresponding kinetic energy loss, and simulates the rotor’s attenuation. The simulation predicts an attenuation of 0.23 Hz within a 12-hour period, corresponding to an average background pressure of 7 × 10-5 Pa. A comparison with observed residual damping data, showing an attenuation of 1.17 Hz and a background pressure of 1.6308 × 10-4 Pa, demonstrates high consistency. This affirms the reliability of the numerical model and calculation results regarding eddy current-induced residual damping presented in this article.

Energy storage comparison of chemical production decarbonization: Application of photovoltaic and solid oxide electrolysis cells

The fossil fuel driven chemical production leads to significant greenhouse emission, and the low-carbon emission technologies are necessary for carbon neutrality. The integration of solid oxide electrolysis cells (SOEC) and H2-O2 combustion can replace the fossil fuel and supply high-temperature heat for reactions. However, the energy demand keeps consistent but the renewable energy fluctuates with time. Therefore, energy storage is important for such a change. Clean fuel replacement and electrification are applied in a case study of ethylene plant, which requires 147 MW of clean fuel and 91.36 MW of grid power. Photovoltaic (PV) solar energy drives SOEC and liquefied H2, compressed H2, compressed air energy storage (CAES) are compared. A mixed integer nonlinear programming model is proposed to evaluate decarbonization effect and cost, which are balanced by multi-objective optimization. The results show that the liquefied H2 is superior to other choices because of the high efficiency. The hydrogen of 126.27 MW is the optimal point, which requires 415 MW SOEC and PV panels. Also, this study proposes that the power grid should communicate with energy consumers such as chemical plants to ensure the energy storage method, or supply renewable energy directly, which avoids energy loss and unreasonable energy transition.

Modulation of monolayer SnSe2 optoelectronic properties by applied electric field and atomic doping

Based on the first principles, we have calculated the influence of the applied electric field and doped X (X = N, P, As, Sb) atoms on the optoelectronic properties and phonon dispersion of the monolayer 2D material SnSe2. The calculation results show that intrinsic SnSe2 is a semiconductor with a band gap value of 0.884 eV. The doping of X atoms improves the energy band tunability of the monolayer SnSe2 system and becomes more stable. The N-doped SnSe2 system has the most stable structure and the best doping performance. When the electric field strength of 0.3 V/Å is applied on the surface of the N-doped system, the band gap of the system increases. The energy gap gradually decreases when the electric field strength continues to increase from 0.3 V/Å to 0.9 V/Å. At an applied electric field strength of 0.9 V/Å, the system changes from semiconductor to metallic properties. As far as the optical properties are concerned, the applied electric field increases the static refractive index of the system, the imaginary part of the photoconductivity increases, the energy loss function decreases, and the light absorption performance improves. The applied electric field successfully enhanced the optical properties of the SnSe2 system. The applied electric field strength of 0.9 V/Å doped N system has the best optical properties. This provides a new way to explore the optoelectronic devices based on the SnSe2 doped system.

Spectroscopic analysis of color origins in titanium-based thin films deposited by cathodic arc deposition

The distinctive colors observed in titanium-based (Ti-based) decorative coatings fabricated by cathodic arc deposition originate from the unique electronic, morphological, and chemical properties of these films. Most Ti-based film colors arise from their surface band gaps, as measured by electron energy loss spectroscopy, with the exception of the lowest brightness (TLB) and green hues. The green color in titanium dioxide films typically results from interference between light reflected from the film and substrate interfaces. In contrast, the black color in Ti-based coatings stems from the chemical structure, specifically the presence of Ti-C and C=C(sp2) bonds within the film. Moreover, the large band gap of the LTB film surface is attributed to surface oxidation, as detected by soft X-ray spectroscopy. Significantly, the film thickness and surface roughness are characterized by field emission secondary electron microscopy and atomic force microscopy, respectively.

Non-contact and non-invasive water level measurement outside metal pipes with electromagnetic acoustic resonance

Accurate measurements of water levels within metal pipes are vital, particularly in environments where thick-walled pipes serve as critical components, such as in nuclear facilities. Measuring water levels in pipes becomes more difficult under high temperatures and pressures. In response to this need, a method involving electromagnetic acoustic measurement is proposed. This method begins with a transducer emitting a high-frequency pulse designed for precise measurements of wall thickness, then calculates the resonance frequency using the time intervals between echoes. Finally, the transducer emits an excitation signal at the fundamental resonance frequency to measure the water level. At low water levels, the measurement is conducted by manually scanning along the pipes, utilizing varying energy losses. At high water levels, the resonance echo method is employed. Numerical simulations have demonstrated that this approach effectively improves signal amplitude, thereby ensuring the robustness of the measurement. Experimental results also demonstrated that the proposed method boosted the echo signal-to-noise ratio to approximately 15 dB. Additionally, it successfully detected water levels in both aluminum and stainless-steel pipes. Therefore, it is considered to be a highly efficient non-contact and non-invasive method to measure liquid levels in metal pipes, and it has proved to hold significant potential for engineering applications.