Maximum Energy Conversion Research Articles

Manipulation of metavalent bonding to stabilize metastable phase: A strategy for enhancing zT in GeSe

AbstractExploration of metastable phases holds profound implications for functional materials. Herein, we engineer the metastable phase to enhance the thermoelectric performance of germanium selenide (GeSe) through tailoring the chemical bonding mechanism. Initially, AgInTe2 alloying fosters a transition from stable orthorhombic to metastable rhombohedral phase in GeSe by substantially promoting p‐state electron bonding to form metavalent bonding (MVB). Besides, extra Pb is employed to prevent a transition into a stable hexagonal phase at elevated temperatures by moderately enhancing the degree of MVB. The stabilization of the metastable rhombohedral phase generates an optimized bandgap, sharpened valence band edge, and stimulative band convergence compared to stable phases. This leads to decent carrier concentration, improved carrier mobility, and enhanced density‐of‐state effective mass, culminating in a superior power factor. Moreover, lattice thermal conductivity is suppressed by pronounced lattice anharmonicity, low sound velocity, and strong phonon scattering induced by multiple defects. Consequently, a maximum zT of 1.0 at 773 K is achieved in (Ge0.98Pb0.02Se)0.875(AgInTe2)0.125, resulting in a maximum energy conversion efficiency of 4.90% under the temperature difference of 500 K. This work underscores the significance of regulating MVB to stabilize metastable phases in chalcogenides.

A generalized model for a triboelectric nanogenerator energy harvesting system

A triboelectric nanogenerator (TENG) energy harvesting system involves at least three components: the mechanical source that inputs mechanical energy to drive TENGs, the TENG device itself as an energy converter, and an external electrical circuit that output the energy from TENGs. Multiple theoretical models have been developed for structural optimization design and maximum power output, yet there has been less emphasis on dynamic modelling of the entire energy harvesting system. This work presents attempts to establish such system-level models that encompass both mechanical and electrical systems. Special consideration is paid to the dynamic contact problem in this generalized model, since dynamic response of impacts can significantly affect the electric outputs. To address contact constraint problems, the penalty function method is utilized to handle non-smoothness and discontinuity. Subsequently, this research specifies how to improve the maximum energy conversion efficiency, and suggest optimal executive strategies for maximizing the energy output through a thorough parametric study. The anticipated outcome is that the generalized model will not only guide optimization design and predict the dynamic characteristics of the energy harvesting system but also assess the potential feasibility of mechanical energy harvesting technology across diverse application domains.

Efficient single-cycle mid-infrared femtosecond laser pulse generation by spectrally temporally cascaded optical parametric amplification with pump energy recycling.

We proposed spectrally temporally cascaded optical parametric amplification (STOPA) using pump energy recycling to simultaneously increase spectral bandwidth and conversion efficiency in optical parametric amplification (OPA). Using BiB3O6 and KTiOAsO4 nonlinear crystals, near-single-cycle mid-infrared (MIR) pulses with maximum energy conversion efficiencies exceeding 25% were obtained in simulations. We successfully demonstrated sub-two-cycle, CEP-stable pulse generation at 1.8 µm using a four-step STOPA system in the experiment. This method provides a solution to solve the limitations of the gain bandwidth of nonlinear crystals and the low conversion efficiency in broadband OPA systems, which is helpful for intense attosecond pulse generation and strong laser field physics studies.

High‐Temperature Semiconductor CuO/SiC‐Based Catalyst for Artificial Photosynthesis

AbstractArtificial photosynthesis can convert CO2 and H2O into hydrocarbons via solar energy. However, the extremely low process efficiency is a major obstacle to this application. The photocatalyst is considered to be the key factor to raise the overall solar energy conversion efficiency. Much research focused on co‐catalysts, but less attention has been paid on the high‐temperature semiconductor. Herein, a strategy is proposed involving high‐temperature semiconductor to design target photocatalyst dealing with the artificial photosynthesis at high temperature. Based upon this strategy, a CuO/SiC catalyst with single atom characteristic was designed, prepared and the activity of CO2 photoreduction with H2O was tested in a high temperature environment. Above 150 °C, the catalyst activity was boosted and unprecedented performance values were attained. Under the irradiation condition delivered by a 1000 W Xe light and at 350 °C, the obtained yields of CH4, C2H4, and C2H6 were 2041.4 μmol ⋅ g−1, 15.2 μmol ⋅ g−1, and 63.6 μmol ⋅ g−1, respectively. The overall CO2 conversion reached 24.6 % and the maximum solar energy conversion efficiency was 2.3 % without any sacrificed agents. This strategy will be helpful to overcome the current limitations for the industrialization of artificial photosynthesis and accelerate the related research on photothermal catalysis.

A Unique Amorphous Porous BiSbOx Nanotube with Abundant Unsaturated Sb‐Stabilized BiO8−x Sites for Efficient CO2 Electroreduction in a Wide Potential Window

AbstractThe CO2 electroreduction reaction using sustainable electricity emerges as a viable strategy to produce high‐value‐added and profitable chemicals. The achievement of superior activity at a lower overpotential and higher selectivity in a wide potential window is vitally important for large‐scale industrial applications. Herein, a carbon‐composite amorphous porous BiSbOx nanotube with abundant unsaturated sites is reported to boost the conversion of CO2 to formate, exhibiting a formate selectivity of >90% in an extremely broad range of potentials from −0.5 to −1.4 V versus reversible hydrogen electrode (RHE) and a maximal energy conversion efficiency of 77.1%. Importantly, pure formic acid solution is directly obtained in a solid‐electrolyte cell for industrial‐scale applications. The porous tubular structure can expose more catalytic active sites, accelerate the mass transfer, and show fast surface charge transfer. Moreover, the unique coordination‐unsaturated Sb‐stabilized BiO8−x site can not only enhance the adsorption and activation of CO2 but also reasonably balance the stabilization and hydrogenation of *OCHO intermediate, thus leading to its obviously higher catalytic performance. As a result, a novel amorphous porous BiSbOx nanotube is successfully designed for efficient CO2 electroreduction, which may shed new light on developing many more amorphous composite metal oxide catalysts for conversion of inert small molecules.

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.

Comparative analysis of the hybrid gazelle‐Nelder–Mead algorithm for parameter extraction and optimization of solar photovoltaic systems

AbstractThe pressing need for sustainable energy solutions has driven significant research in optimizing solar photovoltaic (PV) systems which is crucial for maximizing energy conversion efficiency. Here, a novel hybrid gazelle‐Nelder–Mead (GOANM) algorithm is proposed and evaluated. The GOANM algorithm synergistically integrates the gazelle optimization algorithm (GOA) with the Nelder–Mead (NM) algorithm, offering an efficient and powerful approach for parameter extraction in solar PV models. This investigation involves a thorough assessment of the algorithm's performance across diverse benchmark functions, including unimodal, multimodal, fixed‐dimensional multimodal, and CEC2020 benchmark functions. Notably, the GOANM consistently outperforms other optimization approaches, demonstrating enhanced convergence speed, accuracy, and reliability. Furthermore, the application of the GOANM is extended to the parameter extraction of the single diode and double diode models of RTC France solar cell and PV model of Photowatt‐PWP201 PV module. The experimental results consistently demonstrate that the GOANM outperforms other optimization approaches in terms of accurate parameter estimation, low root mean square values, fast convergence, and alignment with experimental data. These results emphasize its role in achieving superior performance and efficiency in renewable energy systems.

Investigation of γ-photon sources using near-critical density targets towards the optimization of the linear Breit–Wheeler process

In this paper we analyze the production of high energy synchrotron gamma photons in laser-plasma interaction for a laser intensity in 1022– 5⋅1023Wcm−2 and a near-critical density target using two dimensional particle-in-cell simulations. In the optimum configuration to maximize the conversion efficiency of the laser energy to γ-photons, we studied the production of electron–positron pairs by the linear Breit–Wheeler process in the collision of two identical γ-photon beams using a dedicated photon-photon collision simulation code. A maximum laser energy conversion coefficient of 33% in high energy photons was obtained and a photon beam intensity, with energies above 1MeV , of 2⋅1020Wcm−2 at 150μm distance from the initial position of the target (for the highest laser intensity considered). We show that the optimum case to detect the linear Breit–Wheeler pairs corresponds to a laser intensity of 1023Wcm−2 . Our results can be used for the preparation of experimental campaigns for the detection of linear Breit–Wheeler pairs at the Apollon and ELI laser facilities.

Improved VIV energy harvesting with a virtual damper–spring system

In recent years, energy harvesting systems driven by vortex induced vibrations (VIV) emerged as potential alternative to conventional rotor-based installations, in particular for low flow speeds in water. Best energy outputs are obtained when the flow-dependent VIV frequency locks in the natural frequency of the energy harvesting structure. However, placed in tidal currents or rivers with variable flow rates, the VIV frequency changes, leading to frequency mismatch with efficiency losses. In this paper, we present a new mechatronic experimental set-up to study the harvesting efficiency of a VIV driven cylinder under various flow rates. In particular, we explore options to improve harvesting efficiency by adding computer controlled virtual damping and stiffness to the mechanical system. The setup comprises an elastically mounted, single-degree-of-freedom cylinder within a low-speed water tunnel. Virtual damping and stiffness are applied by controlling the force exerted through a mechanically coupled DC motor. The experiments reveal that optimal values for damping and stiffness are consistent with previous results from the literature. The maximum energy conversion efficiency of around 18% is achieved when oscillation and vortex shedding frequencies are synchronized. The explored parameter space highlights in particular that mismatches between oscillation and vortex shedding frequency strongly decrease the achievable efficiency. By contrast, the peak efficiency is less sensitive to an increase of damping due to energy harvesting. All these observations suggest that VIV driven energy harvesting systems need a real-time structural stiffness control to maintain an economically acceptable efficiency under various flow conditions. In the near future, we plan to automate the structural stiffness control under various flow rates by testing Machine Learning algorithms with our mechatronic set-up.

Study on energy conversion efficiency of wave generation in shake plate mode

In recent years, increasing attention has been paid to factors affecting the efficiency of converting wave energy from kinetic energy using shake plates. This research was based on the volume of fluid method to evaluate the energy conversion efficiency of waves generated in the shake plate mode. The effects of different shake plate parameters and water depths on the kinetic energy conversion efficiency were studied, and the results agreed well with experimental data. Results indicated that the angular velocity of the shake plate had the highest influence on kinetic energy conversion efficiency. In the range of ωx to 1.8ωx, the maximum kinetic energy conversion efficiency was 52.1 %. The influence of the oscillation amplitude of the shake plate on the kinetic energy conversion rate was relatively low. As a result, the kinetic energy conversion efficiency remained at approximately 18.10 % even with changes in oscillation amplitude. The kinetic energy conversion efficiency of the shake plate increased with an increase in water depth, with maximum increase 87.39 % seen between 0.15 and 0.2 m. Our research is expected to serve as a reference for the implementation of efficient wave energy generation systems worldwide.

Hydrogen‐bonded organic framework core–shell composite for synergistic antimicrobial therapy

AbstractHydrogen‐bonded organic frameworks (HOFs) are crystalline porous materials with permanent voids formed via self‐assembly of organic molecules through hydrogen bonding and intermolecular forces. Further combination of HOFs with functional material would broaden their application horizon but were less explored in existing literature. Herein, a highly porous and photosensitive HOF was successfully coated onto upconversion nanoparticles (UCNPs) to construct a core–shell structure named UNCPs@PFC‐73‐Ni. To enhance spectral overlap and maximize energy conversion efficiency, this study utilized the Er and Tm co‐doped UCNPs, which can effectively convert infrared light into visible light emission thereby exciting the porphyrin shell. Subsequent investigation reveals that the composite exhibits significant photodynamic and photothermal effects under infrared light. Encouraged by its noticeable photoactivity, UCNPs@PFC‐73‐Ni was evaluated as an antibacterial agent against Escherichia coli. Notably, significant antibacterial efficacy was observed, highlighting the potential of UCNPs@PFC‐73‐Ni as an effective antibacterial agent under infrared light irradiation.

Improve methanol efficiency for direct methanol fuel cell system via investigation and control of optimal operating methanol concentration

This study investigates and controls the optimal operating methanol concentration for direct methanol fuel cell (DMFC) system, which effectively improves the efficiency of DMFC system. Firstly, a DMFC output characteristic model and a nonlinear stack methanol concentration model were established. Moreover, an adaptive observer was developed to reconstruct unmeasurable stack methanol concentration to estimate methanol concentration. Then, in order to achieve the minimum methanol consumption under required power, the reference methanol concentration was determined by analyzing DMFC system with its maximum energy conversion efficiency. Finally, the sliding mode algorithm was adopted to track reference optimal methanol concentration. The estimated performance of adaptive observer and non-adaptive observer for methanol concentration was compared through experimental bench data. Furthermore, the methanol consumption and energy conversion efficiency under proposed optimal methanol concentration strategy and fixed methanol concentration were compared. The comprehensive result demonstrates that the adaptive observer has better performance than non-adaptive observer in terms of estimated performance. Moreover, the proposed strategy for optimal methanol concentration was compared with fixed methanol concentration of 0.3 mol/L and 0.4 mol/L, and the fuel consumption of DMFC system was reduced by 7.9% and 30.9% respectively.

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.

Maximizing the energy conversion of triboelectric nanogenerator through the synergistic effect of high coupling and dual-track circuit for marine monitoring

The wave energy harvesting efficiency (EHE) and electrical energy storage efficiency (ESE) significantly impact ocean power at the front-end and back-end stages, respectively. In this work, to maximize the overall energy conversion affected by these two factors, a clip-like structured pendulum coupled nanogenerator (CP-CNG) integrated with a dual-track circuit (DTC) is elaborately designed to address poor energy conversion of the TENGs for marine monitoring. The optimized EHE was realized through coupling one freestanding triboelectric nanogenerator (FR-TENG) unit and two electromagnetic generator (EMG) units into two contact-separation triboelectric nanogenerator (CS-TENG) units. The space utilization rate of CP-CNG can be as high as 91.9%. Meanwhile, increased ESE is achieved by integrating DTC as voltage regulators, which perform backend energy management for CS-TENG and EMG, respectively. It is worth noting that for a 1 mF capacitor, the stored energy via the cooperation of CP-CNG and DTC can reach 60.7 mJ in 110 s, which is about 164 times that of CS-TENG (0.37 mJ) coupling with FR-TENG and EMG and 1.6 times that of CS-TENG (36.8 mJ) with buck circuit, demonstrating excellent synergistic effects. Owing to the synergistic effect, one CP-CNG can continuously drive four thermohygrometers under simulated water wave conditions. In additional, a hazard alarm system, including an immersion sensor, Bluetooth and gateway support, can also be powered by one CP-CNG successfully. This work develops a state-of-the-art concept for maximum energy conversion of TENGs, which should have a profound impact on the design of high-performance TENGs in the future.

Synergistic actuation performance of artificial fern muscle with a double nanocarbon structure

Electrochemically powered carbon nanotube (CNT) yarn muscles are of increasing interest because of their advantageous features as artificial muscles. They are light, and have high electrical properties, mechanical strength, and chemical stability. Twist-based CNT yarn muscles show superior actuation performance: 30 times the work capacity and 85 times the power density of natural muscles. Despite achieving these high performances, there is still potential for performance improvement because their twisted structure is not fully utilized. In particular, designing a cross-sectional structure that allows ions to freely enter and exit the twisted structure of the yarn muscle is necessary. Here, we propose highly enhanced artificial muscles with high chemical stability that consist of only nanocarbon materials of carbon nanoscroll (CNS) and twisted CNT yarns. The CNS/CNT yarn muscles (CCYM) can improve the ion accessibility and utilization of the twist structure. The maximum contractile stroke, work capacity, power density, and energy conversion efficiency of the CCYM were 20.11%, 2.26 J g−1, 0.53 W g−1, and 3.39%, which are 1.4-, 1.4-, 4.8, and 4.3 times that of the pristine CNT yarn muscles, respectively. The effects of CNS on CCYM were confirmed by experimental and theoretical analyses. Additionally, in a solid electrolyte, which opens up new application possibilities, the CCYM demonstrates high actuation performance (16.38%) with very low input energy.

A numerical simulation of solar cells based on the CuO and Cu2O absorber layers with ZnMgO window layer

In this paper the software of Solar Sell Capacitance Simulator (SCAPS) is used to study the performance of ZnO:Al /Zn1-xMgxO/CuxO solar cells. As an absorber layer are used CuO and Cu2O compounds. The photovoltaic parameters have been calculated for the samples prepared at different deposition conditions (layer thickness, magnesium concentration in window layer). Simulated current–voltage curves allow to determinate the optimal deposition conditions. As a result of the numerical simulation there were determined the optimal solar cells layers fabrication parameters, which provide their maximal solar energy conversion efficiency. They are: in case of CuO/ZMO/AZO structure - fill-factor is 76.46 %, photo-conversion efficiency is 23.89 %; in case of Cu2O/ZMO/AZO structure – fill-factor is 69.44 %, photo-conversion efficiency is 9.63 %, respectively.

Effects of Sodium Selenite on the Growth and Photosystem II Activity of Arthrospira platensis Gom.

Arthrospira platensis (A. platensis) is a species of cyanobacteria with high economic value; the species is commercially well known as Spirulina platensis, and A. platensis was used in this paper. Its high adaptability, high photosynthetic efficiency, and fast growth rate make it one of the few cyanobacteria that can be cultivated on a large scale. Therefore, using the selenium enrichment property of A. platensis to cultivate selenium-enriched A. platensis will not only enhance the physiological efficacy of A. platensis but also increase its economic value significantly. In this study, we investigated the effects of sodium selenite on the growth and photosynthetic performance of A. platensis selenium by setting different amounts and methods of sodium selenite addition, and we explored the optimal culture conditions of the best dosage and method of sodium selenite addition. The results showed that the experimental group treated with sodium selenite at 700 μmol/L had the fastest growth, and the contents of soluble protein, phycocyanin C, and chlorophyll a increased by approximately 67.9%, 1.44 times, and 38.8% compared to the control group, respectively. Superoxide dismutase (SOD) and catalase (CAT) activity increased by 1.88-fold and 65%, respectively, and malondialdehyde (MDA) levels were reduced by 62% compared to the control group. The results of the OJIP assay showed that the J and I points were significantly higher at the batch addition and treatment concentration of 700 μmol/L, with the rate of QA being reduced and the proportion of the slowly reduced PQ pool being increased. The values of the maximum light energy conversion efficiency (Fv/Fm) per unit of reaction center were higher in both sodium selenite treatment groups than in the control group, indicating that the light energy conversion efficiency of A. platensis was promoted under all concentration treatment conditions. The batch addition of sodium selenite at concentrations less than 700 μmol/L resulted in significantly higher ABS/RC values than the control, and they were far superior to the one-time addition method. The reason for this may have been that the batch addition of sodium selenite at low concentrations increased the light absorption capacity of the unit reaction center of PSII, resulting in a rise in captured light energy, a rise in the energy captured by the reaction center for electron transfer (ETo/RC), a decrease in the energy dissipated in the absorption of light energy by the reaction center (DIo/RC), and an increase in the photosynthetic performance index (PI abs).

Enhanced thermal and angular velocity-induced hybrid piezoelectric energy harvesting of smart turbine blades

In this study, an approach is proposed to examine hybrid piezoelectric energy harvesting performances from vibrations induced by thermal and angular velocity loads in order to generate energy from the smart turbine blade. In the proposed method, a smart turbine blade is formed by patching the piezoelectric material to the root surface of the turbine blade. A finite element (FE) model of the smart turbine blade is established and then it is validated with a smart blade model in a reference study to test the reliability and accuracy of the FE method. The defined loads are applied to the smart blade to obtain energy from mechanical vibrations induced by thermal and angular velocity loads. Temperature distribution, voltage, and vibration results obtained from energy harvesting analysis under different thermal and angular velocity loads are presented. In order to investigate the energy conversion efficiency of the energy obtained from the system, the energy harvesting circuit is tested in terms of battery discharge times and power output values. The results show that while the maximum energy conversion in the thermally induced smart turbine blade is 11.9 W, a power output of 12.3 W is obtained from the hybrid energy harvesting mechanism under angular velocity and heat flux loads.

Impacts of thermal and electric contact resistance on the material design in segmented thermoelectric generators

Segmented thermoelectric generators (STEGs) can exhibit present superior performance than those of the conventional thermoelectric generators. Thermal and electrical contact resistances exist between the thermoelectric material interfaces in each thermoelectric leg. This may significantly hinder performance improvement. In this study, a five-layer STEG with three pairs of thermoelectric (TE) materials was investigated considering the thermal and electrical contact resistances on the material contact surface. The STEG performance under different contact resistances with various combinations of TE materials were analyzed. The relationship between the material sequence and performance indicators under different contact resistances is established by machine learning. Based on the genetic algorithm, for each contact resistance combination, the optimal material sequences were identified by maximizing the electric power and energy conversion efficiency. To reveal the underlying mechanism that determines the heat-to-electrical performance, the total electrical resistance, output voltage, ZT value, and temperature distribution under each optimized scenario were analyzed. The STEG can augment the heat-to-electricity performance only at small contact resistances. A large contact resistance significantly reduces the performance. At an electrical contact resistance of RE = 10–3 K·m2·W−1 and thermal contact resistance of RT = 10–8 Ω·m2, the maximum electric power was reduced to 5.71 mW (90.86 mW without considering the contact resistance). And the maximum energy conversion efficiency is lowered to 2.54% (12.59% without considering the contact resistance).

Analytical modeling and experimental verification of a multi-DOF spherical pendulum electromagnetic energy harvester

Low-frequency vibration energy harvesting is a promising technology for providing floating buoys and small marine robots with sustainable energy from ocean waves. A spherical vibration energy harvester with multiple degrees of freedom has the advantages of good multi-directional adaptability and compact structure. However, its magnetic field distribution in three-dimension space is much more complex due to the combined effect of a series of cylindrical permanent magnets mounted on the surface of a gimbaled pendulum. The traditional finite element method is too time-consuming to perform efficient parameter design and optimization. To solve this problem, this work develops an analytical electromagnetic model for the spherical vibration energy harvester based on Biot-Savart Law. This model can be used to predict spatial magnetic flux distribution and electromotive force for given magnet and coil parameters. The accuracy and computational cost of the analytical model is verified by the comparison with the finite element method. Furthermore, the optimization of electromagnetic parameters is implemented to achieve maximum energy conversion efficiency. Finally, an optimized prototype is fabricated and tested in both laboratory and real sea. The resonant frequency and energy conversion efficiency of the prototype reaches 1.0 Hz and 25.45 %, respectively. It is shown that the experimental results are in good accordance with the analytical results.