Improve Energy Conversion Efficiency Research Articles

A developed convolutional neural network model for accurately and stably predicting effective thermal conductivity of gradient porous ceramic materials

Accurate and stable prediction of the effective thermal conductivity (ETC) of porous ceramic materials is of great significance for their application in areas such as optimizing the design of thermal barrier coatings and improving energy conversion efficiency. Porous ceramic materials exhibit complex porous structures with gradient porosity distributions that pose a great challenge for effective medium theory (EMT) and conventional convolutional neural networks (CNN) in attempting to accurately and stably predict the ETC of porous media. In this study, a CNN model that integrates self-attention and a multiscale feature-fusion mechanism is proposed to predict the ETC of porous media with greater accuracy and stability. The integration of the self-attention and multiscale feature-fusion mechanisms enhances the CNN's ability to learn long-range dependencies and preserve detailed information. The optimization of the CNN's accuracy and stability is visually illustrated using gradient-weighted class activation mapping (Grad-CAM) for ETC. Additionally, by employing the proposed gradient quartet structure generation set (QSGS), a gradient porous ceramic media dataset comprising 10 000 images was built to train the CNN model. Finally, the prediction results and relative error distribution of the ETC were compared across different models. Our model demonstrated improvements in statistical metrics, including a 33.7 % decrease in mean error, 25.2 % decrease in median error, and 59.6 % decrease in maximum error. The decreases in these metrics and Grad-CAM for the ETC strongly demonstrates that the model proposed in this work greatly improved the accuracy and stability of predicting the ETC of ceramic materials with gradient porosity distributions.

Simulation and optimization of 30.17% high performance N-type TCO-free inverted perovskite solar cell using inorganic transport materials

Perovskite solar cells (PSCs) have gained much attention in recent years because of their improved energy conversion efficiency, simple fabrication process, low processing temperature, flexibility, light weight, and low cost of constituent materials when compared with their counterpart silicon based solar cells. Besides, stability and toxicity of PSCs and low power conversion efficiency have been an obstacle towards commercialization of PSCs which has attracted intense research attention. In this research paper, a Glass/Cu2O/CH3NH3SnI3/ZnO/Al inverted device structure which is made of cheap inorganic materials, n-type transparent conducting oxide (TCO)-free, stable, photoexcited toxic-free perovskite have been carefully designed, simulated and optimized using a one-dimensional solar cell capacitance simulator (SCAPS-1D) software. The effects of layers’ thickness, perovskite’s doping concentration and back contact electrodes have been investigated, and the optimized structure produced an open circuit voltage (Voc) of 1.0867 V, short circuit current density (JSC) of 33.4942 mA/cm2, fill factor (FF) of 82.88% and power conversion efficiency (PCE) of 30.17%. This paper presents a model that is first of its kind where the highest PCE performance and eco-friendly n-type TCO-free inverted CH3NH3SnI3 based perovskite solar cell is achieved using all-inorganic transport materials.

Boosting 5-Hydroxymethylfurfural Electrooxidation by Porous Biochar via Loading Numerous Surface-Exposed Cobalt Phosphonates.

The electrooxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) demonstrated its unique superiority, not only in reducing overpotential and improving energy conversion efficiency for green hydrogen production but also in utilizing abundant biomass resources and producing high-value-added chemicals. However, designing highly efficient electrocatalysts for HMF electrooxidation (HMF-EOR) with low cost and high performance for large-scale production remained a huge challenge. Herein, we introduced an easy one-step activation process to produce P-doped porous biochar loaded with multiple crystal surfaces exposed to CoP2O6 catalysts (CoP2O6@PC), which exhibited outstanding electrooxidation performance. To achieve a current density of 50 mA cm-2, only a low overpotential of 200 mV was needed for the electrooxidation of HMF in 1.0 M KOH + 10 mM HMF. This performance far surpassed that of other similar materials. CoP2O6@PC exhibited outstanding HMF-EOR performance with high conversion (nearly 100%), selectivity (97.1%), faradaic efficiency (95.3%), and robust stability. This work represents a promising strategy to fabricate macroscale and low-cost HMF-EOR electrocatalysts and achieve potential industrial applications of HMF-EOR.

Patterned Liquid Crystal Polymer Thin Films Improved Energy Conversion Efficiency at High Incident Angles for Photovoltaic Cells.

In this report, micro-patterned silicon semiconductor photovoltaic cells have been proposed to improve the efficiency in various incident sunlight angles, using homeotropic liquid crystal polymers. The anisotropic liquid crystal precursor solution based on a reactive mesogen has good flowing characteristics. It can be evenly coated on the silicon solar cells' surface by a conventional spreading technique, such as spin coating. Once cured, the polymers exhibit asymmetric transmittance properties. The optical retardation characteristics of the coated polymer films can be eventually determined by the applicable coating and curing parameters during the processes. The birefringence of light then influences the optical path and the divergence of any encountered sunlight. This allows more photons to enter the active semiconductor layers for optical absorption, resulting in an increase in the photon-to-electron conversion, and thus improving the photovoltaic cell efficiency. This new design is straightforward and could allow various patterns to be created for scientific development. The experimental results have evidenced that the energy conversion efficiency could be improved by 2-3% for the silicon photovoltaic cells, under direct sunlight or at no inclination, when the liquid crystal polymer precursor solution is prepared at 5%. In addition, the efficiency could be much more significantly improved to 14-16% when the angle is inclined to 45°. The unique patterned liquid crystal polymer thin films provide enhanced energy conversion efficiency for silicon photovoltaic cells. The design could be further evaluated for other solar cell applications.

Optimizing thin-film silicon solar cells with nanostructured TiO2 and a silver back reflector for enhanced energy conversion efficiency

This paper investigates the improvement of energy conversion efficiency in thin-film silicon solar cells by employing periodic nanostructures of TiO2 on the silicon active layer and a back reflector featuring periodic nanostructures of silver. The objective is to increase the optical path length, enhance absorption probability for longer wavelengths, and subsequently improve solar cell performance. Three silicon-based solar cell configurations are proposed and simulated using the finite difference time domain (FDTD) method to assess their performance. Electrical characteristics are obtained through the drift-diffusion method. The resulting short-circuit current density increased from 40.93 to 65.28 to 95.373mA/cm2 for the three cells, leading to significant improvements in conversion efficiency with observed values of 20.39%, 33.26%, and 47.28%, respectively, in the optimized structures. Furthermore, we compare the simulation results of the three structures with those of a reference structure and several structures previously proposed in the literature.

Green energy breakthroughs: Harnessing nano-catalysts and enzymatic catalysts for bioenergy generation

Microbial fuel cells and anaerobic digestion are promising bioenergy methods but inefficient and scalable. With its exceptional surface area-to-volume ratio, nano-catalysts are revolutionizing this field. Researchers have improved energy conversion efficiency by immobilizing or embedding nanoparticles on electrodes or catalytic supports to promote electron transport. Nanomaterials like graphene-based catalysts and metal nanoparticles speed up organic matter breakdown and make bioenergy systems more profitable. Researchers are working harder to find new bioenergy-generating methods to address environmental concerns and the demand for sustainable energy. The study discusses how nano-catalysts and enzymatic catalysts are revolutionizing bioenergy production in green energy. Additionally, enzymatic catalysts are the best bioenergy catalysts. Highly specialized, biocompatible, and renewable enzymes provide unrivaled biofuel production potential. Protein engineering and immobilization have improved enzymes for bioenergy systems. Enzymatic catalysts enable biofuel generation from more feedstocks without harsh chemical procedures by controlling biological reactions quickly and precisely. Combining nano- and enzymatic catalysts is promising. Nano-catalysts improve enzymatic processes by creating a favorable microenvironment, enhancing surface binding sites, and enabling substrate transport. This combination may maximize bioenergy systems' biofuel output and wastewater treatment capabilities. According to this study, integrating nano- and enzymatic catalysts is a green energy breakthrough. These advances will improve bioenergy generation by overcoming current techniques, opening new sustainable energy production prospects, and expediting our transition to a greener, more sustainable future.

Finite Element Analysis and Design of a Flexible Thermoelectric Generator with a Rhombus Gap Structure.

Flexible thermoelectric generators (f-TEGs) offer an opportunity to realize wearable, self-powered electronic devices. A typical f-TEG consists of flexible electrodes and rigid thermoelectric (TE) legs in a flexible package. In the realm of f-TEGs utilizing flexible electrodes and TE cuboids, our unwavering objective lies in the attainment of enhanced flexibility and elevated energy conversion efficiency. In this paper, we employ a quasi-three-dimensional thermal model to design an f-TEG with a rhombus gap structure (E/A-RhTEG) with its optimized performance validated by simulation and experiment. Additionally, the lateral and vertical thermal resistances are introduced to further explain the optimizing principle in the f-TEG's output performance. Compared with the conventional TEG with a rectangular air gap structure (E/A-ReTEG), E/A-RhTEG demonstrates improved energy conversion efficiency to some extent. Simulation results indicate that the output power and energy conversion efficiency of a 25-np-pair E/A-RhTEG at a 30 K temperature gradient reach 8.45 mW and 2.55%, which represent a performance improvement of 3.09 and 6.28%, respectively, compared to E/A-ReTEG. To further elucidate the optimization principle in the performance of f-TEGs, additional considerations are given to the lateral and vertical resistances. In this study, E/A-RhTEG comprising 25 np pairs is fabricated utilizing TE cuboids. Experimental findings indicate that E/A-RhTEG exhibits a voltage output of 127.07 mV when subjected to a temperature difference of 30 K, which demonstrates a performance enhancement of 4.06% compared to E/A-ReTEG. Furthermore, this study also demonstrates its implementation when wrapped around a curved surface and successfully achieves a self-powered device system after device performance optimization.

Enhancing Thermal Performance of Thermodynamic Cycle through Zeotropic Mixture Composition Regulation: An Overview

Composition regulation of zeotropic mixture working fluid for a thermodynamic cycle is an effective way to improve energy conversion efficiency, which offers the potential to construct efficient, flexible and intelligent cycles. Current research on cycle construction of zeotropic mixture composition regulation still heavily relies on construction methods using pure working fluids, where the characteristics of flexible composition variations fail to be utilized. In this paper, the research progress of cycle construction methods and composition regulated structures are comprehensively reviewed, aiming to clarify the potential for enhancing a thermodynamic cycle based on composition regulation. The characteristics of different cycle construction methods are firstly summarized and compared. Then, the composition-regulated structures of a physical-based method and chemical-based method are introduced, and the composition regulation performance are also concluded. Finally, a future outlook on the cycle design and structure design is provided. The review results show that the combination of 3D construction method and superstructure/intelligences construction method has the potential to maximize the cycle performance, where the improvement of each thermal process and the optimization of complex cycles can be considered simultaneously. The composition regulation based on a passive physical method has the advantage of being readily applicable; however, the composition regulation range is limited. In addition, the distillation and hydrate method have a wider regulation range through extra energy input, where the trade-off between energy consumption and cycle performance improvement should be considered in the future. This study greatly assists in the design of thermodynamic cycles involving zeotropic mixture composition regulation and the corresponding composition regulation structures.

Aeroacoustic investigation of a ducted wind turbine employing bio-inspired airfoil profiles

Ducted wind turbines for residential purposes are characterized by a lower diameter with respect to conventional wind turbines for on-shore applications. The noise generated by the rotor plays a significant role in the overall aerodynamic noise. By making modifications to the blade sections of the wind turbine, we can alter the contributions of aeroacoustic noise sources. This study introduces innovative wind turbine blade designs inspired by owl wing characteristics, achieving significant noise reduction without compromising aerodynamic performance. A three-dimensional scan of an owl wing was first employed to derive a family of airfoils. The airfoils were employed to modify the blade of a referenced wind turbine airfoil section at various positions on the blade span to determine a blade operating more efficiently at the tip-speed ratio of the original one. While maintaining the same aerodynamic performance, the bio-inspired profiles show a more uniform pressure coefficient distribution, considerably decreasing in the noise level. Furthermore, this study makes considerable progress in ducted wind turbine design by obtaining an 8 dB noise reduction and a 12% improvement in sound pressure level. An in-depth aerodynamic examination shows a 6.4% rise in thrust force coefficient and optimized power coefficients, reaching a peak at a tip speed ratio of 8, demonstrating improved energy conversion efficiency. The results highlight the dual advantage of the innovative design: significant noise reduction and enhanced aerodynamic efficiency, offering a promising alternative for urban wind generation.

Improvement of energy conversion efficiency in traveling wave rotary ultrasonic motor by increasing friction coefficient

This article introduces a method of enhancing the energy conversion efficiency of a traveling wave rotary ultrasonic motor with a flexible rotor by increasing the friction coefficient at the stator–rotor interface. The increased friction coefficient leads to improvements in energy conversion efficiency by increasing the output power and reducing friction loss power. Experimental verification showed that the friction coefficient in the interface increased from 0.21 to 0.32, the maximum energy conversion efficiency increased from 36.8% to 46.3%, and the interface friction loss was reduced.

Functional Grading Between Soft-Magnetic Fe-Co/Fe-Ni Alloys and the Effect on Magnetic and Microstructural Properties.

Producing soft magnetic alloys by additive manufacturing has the potential to overcome cracking and brittle fracture issues associated with conventional thermomechanical processing. Fe-Co alloys exhibit high magnetic saturation but low ductility that makes them difficult to process by commercial methods. Ni-Fe alloys have good ductility and high permeability in comparison to Fe-Co, but they suffer from low magnetic saturation. Functional grading between Fe-Co and Ni-Fe alloys through blown powder directed energy deposition can produce soft magnetic materials that combine and enhance properties beyond the strengths of the individual magnetic materials. This work focuses on the microstructure, crystal structure, and magnetic properties of functionally graded Fe49Co49V2/Ni80Fe16Mo4 coupons. The grading between the two materials is found to refine the microstructure, thereby improving the mechanical hardness without the use of a nonmagnetic element. Postbuild thermal treatments are found to recrystallize the microstructure and increase the grain size, leading to improved magnetic properties. Analysis of crystal structures provides an understanding of the solubility limits and phase equilibria between the BCC (Fe-Co) and FCC (Ni-Fe) structures. Success in functional grading of soft magnets may provide a pathway toward improving energy conversion efficiency through strategic combinations of high saturation and high strength materials.

Enhanced Indoor Conversion Efficiency of Dye-Sensitized Solar Cells by Optimizing Ball-Milling Process of TiO2 Paste

The rapid spread of the Internet of Things (IoT) along with the development of innovative low-power electronic devices has also driven the development of indoor photovoltaics. In this paper, we propose a simple and economically feasible solution that can improve the efficiency of dye-sensitized solar cells (DSSCs) under indoor light conditions by ~112%, without requiring a complex TiO2 photoanode architecture or the design of new dyes. The ball milling process of the TiO2 paste was optimized for indoor light conditions for the first time, both in terms of efficiency and production costs, by developing a rapid preparation method that can be used industrially for the application of DSSCs. A simple use of 12 mm diameter balls caused beneficial structural modifications, decreasing the size of the crystallites, and leading to a high OH generation on the TiO2 surface responsible for the improvement of energy conversion efficiency.

Multipoint Energy-Balanced Laser-Ultrasonic Transducer Based on a Thin-Cladding Fiber.

This study proposes a novel multipoint transducer system by utilizing the single-mode-multimode-thin-cladding fiber (SMTC) structure. This structure leverages the disparity in mode field diameter between the multimode fiber (MMF) and thin-cladding fiber (TCF) to generate high-amplitude ultrasonic signals safely and efficiently. The fabricated transducer exhibits signal amplitudes 2-3-fold higher compared to conventional laser-ultrasonic transducers. Simulation analysis investigates the impact of the length of the MMF and the diameter of the TCF on coupling efficiency. The coupling efficiency of individual transducer units can be accurately controlled by adjusting the length of the MMF. A three-point energy-balanced laser-ultrasonic transducer system was achieved, with improved energy conversion efficiencies, and the optimal thickness of candle soot nanoparticles (CSNPs) is experimentally determined. Additionally, we carried out experiments to compare the performance of the proposed SMTC-based transducer system under different material conditions using two different photoacoustic materials: graphite-epoxy resin and candle soot nanoparticle-polydimethylsiloxane (CSNP-PDMS) composite. CSNPs, as a cost-effective and easy-to-prepare composite material, exhibit higher photoacoustic conversion efficiency compared to graphite-epoxy resin. The proposed system demonstrates the potential for applications in non-destructive testing techniques.

Investigation of interfacial thermal resistance between Bi2Te3 thin films and metal electrodes via TDTR

A challenge on promoting thermoelectric application is the low energy conversion efficiency of thermoelectric devices. Reducing the contact thermal resistance of a thermoelectric device can improve efficiency effectively. However, study on interfacial thermal transport is lack due to the difficulty on contact thermal resistance measurement. Herein, a study on contact thermal resistance between thermoelectric and electrode materials was reported. We prepared various heterostructures of Bi2Te3–Cu and Bi2Te3–Ni via magnetron sputtering, and measured the contact thermal resistance using a time-domain thermoreflectance technique. Our results show that the contact thermal resistance is affected by both chemical and physical properties of interface. The chemical and physical stability of interfaces, the surface roughness and porosity of films, as well as electrical properties of Bi2Te3, are all related to the contact thermal resistance. The contact thermal resistance of Bi2Te3–Ni prepared at 400 °C can be reduced to 3.96 × 10−7 m2KW−1. Our work provides important experimental data and theoretical basis for optimizing the interlayer between thermoelectric materials and electrodes, and improving energy conversion efficiency of thermoelectric devices.

Hybrid Piezoelectric/Triboelectric Wearable Nanogenerator Based on Stretchable PVDF-PDMS Composite Films.

Hybrid piezoelectric/triboelectric nanogenerators combine the merits of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), possessing enhanced electrical output and sensitivity. However, the structures of the majority of hybrid nanogenerators are rather complex in integrating both functions, limiting their practical application in wearable electronics. Herein, we propose to construct a piezoelectric/triboelectric hybrid nanogenerator (PT-NG) with a simple structure based on a composite film to simultaneously achieve the coupling of piezoelectric charge generation and triboelectrification with improved energy conversion efficiency. The composite film consists of electrospun PVDF nanofibers embedded in the surface of the PDMS film, which not only forms a rough nanomorphology on the surface of PDMS but also provides structural protection to the PVDF nanofibers by PDMS during compressive deformation. The results have shown that the PT-NG can generate much higher electrical outputs than individual TENG and PENG devices. The PT-NG devices exhibit a high level of mechanical-to-electrical energy conversion efficiency with superior performance in charging capacitors and functioning as self-powered wearable sensors for the detection of different signals from finger movement, the recognition of various gestures, and the monitoring of respiration. More importantly, the composite device possesses an impressive structure durability, maintaining its layered structure over 5000 testing cycles without noticing any obvious damage on the nanofibers or detachment between the layers. Our results have demonstrated that the combining of piezoelectric nanofibers and triboelectric substrate is an efficient way to fabricate highly efficient energy harvesting devices for intelligent identification and health monitoring.

Constructing vacancy-rich metal phosphates by the spatial effect of ionic oligomers for enhanced OER activity

By rationally selecting ionic oligomers as building blocks, sub-nano-sized gaps can be constructed in the solid structure of catalysts. This can overcome the inherent limitations associated with vacancy formation of the traditional nucleation pathway.

Innovations in Laser-Driven Plasma Propulsion Systems for Space Exploration

Laser propulsion has emerged as a promising technology for revolutionizing space exploration by offering rapid and efficient spacecraft propulsion. This paper proposes a novel system that integrates dense corona discharge with electrical mechanisms to significantly enhance the efficiency and effectiveness of laser propulsion. Leveraging plasma physics and laser technology, this system harnesses the synergy between dense plasma and laser-driven propulsion, significantly exceeding the capabilities of conventional systems. Theoretical analysis and computational simulations reveal the potential for increased thrust, improved energy conversion efficiency, and enhanced controllability, paving the way for next-generation spacecraft propulsion technologies.

IMPROVING ENERGY CONVERSION USING MXENES: EFFICIENCY ANALYSIS

Maximizing energy conversion efficiency is a major goal in the field of sustainable energy systems. In recent years, MXenes, a new class of two-dimensional materials, have attracted much attention in the context of improving energy conversion efficiency. This literature review provides an overview of the current state of energy research on MXenes, including their synthesis, characterization, and applications in energy storage and conversion systems. There are various methods for the synthesis of MXenes that are being developed to obtain materials with optimal structural and electrochemical properties. Characterization studies of MXenes examine their electrochemical properties, structure, surface, and physicochemical behavior to understand the underlying energy conversion mechanisms and optimize their performance. Applications of MXenes in energy storage and conversion systems include their use in solar cells, thermoelectric devices and batteries. MXenes have high conductivity, mechanical strength, and chemical stability, making them attractive for these applications. Continued research is needed to more fully understand the physical and chemical properties of MXenes and to develop optimal synthesis and application methods to achieve maximum energy conversion efficiency.

Investigation into the hydrogen production performance of a novel 5-kW hybrid-system composed of a solar steam generator directly connected with conventional solid oxide electrolysis cells

Coupling solar energy with solid oxide electrolysis cell has the potential to reduce electricity consumption and improve energy conversion efficiency. This study introduces a pioneering 5 kW direct-connected hybrid system that couples a solar steam generator with solid oxide electrolysis cells utilizing conventional electrical energy for the electrolysis process. The successful demonstration of hydrogen production showcases promising results. When the solar irradiation power is 2.26 kW, the inlet water flow rate is 1.23 kg/h under operations at 700 °C, the hydrogen production efficiency of the system reaches 95.2 %, and the steam conversion ratio approaches 92 %, giving a cumulative hydrogen production yield of 5,840 NL in 6.3 h. The solid oxide electrolysis system is further tested under different operating conditions of the stack and solar irradiation. The experimental results show that a greater operating temperature is conducive to more efficient hydrogen production, while more water vapor at the cathode leads to a larger steam conversion ratio. The results indicate that increasing the irradiation power is beneficial to hydrogen production while decreasing the irradiation power will lead to fluctuations of hydrogen yield. In addition, the system efficiency (45.3 %) is higher than that of a photovoltaic alkaline water electrolysis (12.6 %) or photovoltaic proton exchange membrane electrolysis (14.76 %) system at the same irradiation power. Under the same electrolysis power and cathode inlet temperature, the total power consumption of a traditional solid oxide electrolysis system is significantly greater than that of the proposed hybrid system. The comparison shows that the saved electricity of the proposed hybrid system can account for about 30 %. Therefore, the proposed hybrid system has significant efficiency and power savings advantages.

Surface-grafting modification of attapulgite nanorods with polysiloxane coupling agents for highly-efficient mechanical and triboelectric performance enhancement of silicone rubbers

The quest for polymeric materials that combine mechanical robustness with high triboelectric charge density is paramount in a novel kind of triboelectric nanogenerators (TENGs) that can directly convert mechanical energy into electricity in a clean and green way. Silicone rubbers (SRs) are one of the most frequently-used triboelectric materials owing to their excellent processability and high tendency of being negatively charged via contact electrification (CE), but their potential can be further maximized by strategic doping with nanomaterials. Herein, we introduced a novel kind of naturally occurring clay mineral attapulgite nanorods with surfaces modified by elaborately-synthesized polysiloxane coupling agents (PCA@ATP) to elevate the mechanical and triboelectric performance of silicone rubbers (SRs) efficiently. The modified SRs not only amplified the tensile strength by over 21 % with the addition of only 4 phr PCA@ATP, but also possessed a significant increase by 40.11 % in triboelectric charge density (ρ(Q)). Moreover, the ρ(Q) of modified SR films showed a continuously increasing trend with a further increase of PCA@ATP content. Particularly, SR films doped with 8 phr PCA@ATP showcased a ρ(Q) enhancement by 59 %, rendering them as exceptional candidates for TENGs. Through rigorous experimentation, we observed that increasing the impact frequency and PCA@ATP content consistently enhanced both the output voltage and current of the SR-based TENGs. In comparison to undoped SR films, doping with 4 phr and 8 phr PCA@ATP resulted in an impressive 122 % and 146.68 % boost in voltage and a 393 % and 508.53 % surge in power, respectively. This highly-efficient mechanical and triboelectric performance enhancement of SRs can be ascribed to the homogeneous incorporation of 1D inorganic nanomaterials PCA@ATPs with high Young's modulus, dielectric constant, and topologically-reinforced interface, leading to a comprehensive improvement of mechanical energy transfer, conversion, storage, and dissipation efficiency. This study presents a pioneering strategy for crafting robust triboelectric materials with superior CE performance, paving the way for more effective mechanical energy harvesting.