Energy Conversion Research Articles

Considering Micro/nanostructures at the Surface of Photothermal Materials: A Game Changer in Correct Estimation of Evaporation Rate and Energy Conversion Efficiency in Interfacial Solar Vapor Generation Systems.

Interfacial solar evaporator generation (ISVG) is a new, cost-effective, and eco-friendly emerging method for water desalination. Two main criteria for evaluating ISVG performance are evaporation rate (ṁ) and solar-to-vapor conversion efficiency (η). The main challenge of the previously presented models for the estimation of ṁ and η in 2D systems is that in most cases the calculated values are beyond the theoretical limits, ṁ > 1.47 kg m-2 h-1 and η > 100%, both of which are not acceptable from the thermodynamics viewpoint. Also, the recently presented strategy of reduced vaporization enthalpy for obtaining η < 100% is unacceptable from the thermodynamics approach for ISVG as a two-step continuous process. Therefore, this work aims to present a model and consequently new equations for the correct estimation of evaporation rate and energy conversion efficiency in two-dimensional (2D)-ISVG systems, which are consistent with their corresponding theoretical limits. The basis of the present model is discrimination between the projection area and evaporation area by considering the micro/nanostructures on the surface of interfacial support (photothermal material). This leads to the presentation of new equations for ṁ and η having consistency with thermodynamics laws. The presence of micro/nanostructures on the surface of photothermal material provides a higher evaporation area which is not considered in the previous models and led to theoretically inconsistent results. The results of the present study provide a theoretical basis for the correct estimation of the evaporation rate and energy conversion efficiency in 2D-ISVG systems in future works.

Factors Influencing the Efficiency of Solar Energy Systems

The efficiency of solar panels is significantly influenced by temperature and irradiance, which are crucial in solar energy conversion. As temperatures rise, solar panel efficiency typically decreases due to increased electrical resistance, resulting in lower output voltage and power production. This efficiency loss is quantified by the temperature coefficient, indicating the drop per degree Celsius above 25°C. Advanced cooling systems and optimal thermal management can mitigate these effects. Irradiance, the sunlight intensity reaching the panels, directly affects electricity generation. While higher irradiance increases efficiency by providing more photons for conversion, it can also raise temperatures, negatively impacting performance. Solar panels achieve maximum efficiency under optimal irradiance and moderate temperatures, typically 1000 W/m² at 25°C. Variations in irradiance due to geographical location, time of day, and weather conditions cause fluctuations in power output. Efficient system design must consider local irradiance patterns and utilize tracking systems to maintain optimal panel orientation. To optimize efficiency, innovative methods such as advanced materials, cooling techniques, and smart tracking systems are employed. Additionally, integrating energy storage solutions and predictive analytics helps manage environmental impacts. Proper design, installation, and maintenance strategies are crucial for maximizing solar panel efficiency and lifespan under varying conditions. Understanding the interplay between temperature and irradiance is essential for advancing solar energy technologies, and enhancing their reliability and effectiveness in diverse environments.

Recent Advances in Ruddlesden-Popper Phase-Layered Perovskite Sr2TiO4 Photocatalysts.

Sr2TiO4, a prominent member of the Ruddlesden-Popper (RP) perovskite family, has garnered significant interest in photocatalysis, primarily owing to its distinctive two-dimensional (2D) layered structure. In this review, we provide an insightful and concise summary of the intrinsic properties of Sr2TiO4, focusing on the electronic, optical, and structural characteristics that render it a promising candidate for photocatalytic applications. Moreover, we delve into the innovative strategies that have been developed to optimize the structural attributes of Sr2TiO4. These strategies aim to maximize light absorption, improve charge separation, and accelerate the photocatalytic reaction rates. By highlighting these unique approaches, we strive to contribute to a more profound understanding of the material's potential and stimulate further advancements in developing Sr2TiO4-based photocatalytic systems. The review not only synthesizes the existing knowledge but also offers a perspective in future directions for research and application. As the field of photocatalysis continues to evolve, Sr2TiO4 stands poised to play a pivotal role in the quest for more efficient and sustainable solar energy conversion technology.

Micro-Grid Wind Energy Conversion Systems: Conventional and Modern Embedded Technologies - A Review

This study assesses the effectiveness of an electric microgrid wind energy conversion system using both traditional techniques and contemporary embedded systems, such as artificial neural network-based control mechanisms and fuzzy logic control. The text compares and lists the advantages and disadvantages of various types of wind turbines (WTs). Moreover, this control falls into one of two groups: conventional power control or non-traditional power control. On the other side, conventional control describes methods of control such as manually controlling the turbine rotor's rotation speed and using computational analysis. The current work, in contrast, investigates and evaluates contemporary embedded control techniques used in wind energy conversion systems (WECS), including maximum power point tracking, Artificially intelligent control systems, in relation to the control mechanism, provide complete control over the pitch angle, power coefficient, and tip speed ratio for the best possible wind energy extraction. This makes a direct comparison possible. Nonetheless, there are a few drawbacks and difficulties with the two widely utilized contemporary techniques for power quality extractions: artificially intelligent neural networks and their embedded control systems. However, combining contemporary technology with integrated artificial intelligence controllers may be a workable strategy to lessen and even eliminate these difficulties, as well as advantageous for upcoming studies.

Engineering of Metal-Organic Framework-Derived CoTiO3 Micro-Prisms for Lithium-Ion Batteries.

Metal-organic framework (MOF)-derived transition metal compounds and their composites have attracted great interest for applications in energy conversion and storage. In this work, hexagonal micro-prisms of Ni-doped CoTiO3 composited with amorphous carbon (NixCTO/C) were synthesized using Ti-Co-based MOFs as precursors. The experimental results indicate the substitutional doping of Ni2+ for Co2+ in CoTiO3 (CTO), leading to improved conductivity, as further confirmed by density functional theory calculations. Thus, the carbon-free sample of Ni-doped CTO exhibits improved lithium storage properties compared to the pristine one. Furthermore, when coupled with in situ-formed carbon, the dually modified Ni0.05CTO/C micro-prisms demonstrated a significantly increased reversible capacity of 584.8 mA h g-1, excellent rate capability, and superior cycling stability at a high current density of 500 mA g-1. This enhanced electrochemical performance can be attributed to the synergistic effect of Ni doping and carbon coating.

High-Performance and Anti-Freezing Moisture-Electric Generator Combining Ion-Exchange Membrane and Ionic Hydrogel.

Moisture-electric generators (MEGs), which convert moisture chemical potential energy into electrical power, are attracting increasing attention as clean energy harvesting and conversion technologies. However, existing devices suffer from inadequate moisture trapping, intermittent electric output, suboptimal performance at low relative humidity (RH), and limited ion separation efficiency. This study designs an ionic hydrogel MEG capable of continuously generating energy with enhanced selective ion transport and sustained ion-to-electron current conversion at low RH by integrating an ion-exchange membrane (IEM-MEG). A single IEM-MEG exhibits a maximum open-circuit voltage (VOC) of 0.815 V and a short-circuit current (ISC) of 101 µA at 80% RH. Even at a low RH of 10%, a stable VOC of 0.43 V and ISC of 11 µA can be generated. Moreover, the antifreeze performance of the device is improved by adding LiCl, which significantly expands its operational range in low-temperature environments. Finally, a simple series-parallel connection of six IEM-MEGs can yield an enhanced VOC of 4.8 V and a ISC of ≈0.6 mA, and the scalable units can directly power commercial electronics. This study provides new insights into the design of MEGs that will advance the development of green energy conversion technologies in the future.

Single Axis Solar Tracker

The pace of electricity consumption is rising every day, and people's reliance on traditional energy sources is growing. If it persists, use of traditional energy sources will cease quickly. Therefore, the timing is right to combine conventional and renewable energy sources. The cleanest and most sustainable renewable energy source is solar power. The conversion of solar energy into electrical power is possible using a solar photovoltaic (PV) panel. Several variables, including sun irradiation, solar cell composition, surface temperature, and others, affect how quickly a solar photovoltaic panel produces energy. The solar cell generates more power the more sunshine it receives. Due to variations in the sun's location in the sky, a fixed state solar panel cannot receive the most sunlight during the daylight hour

Grain-Boundary-Rich Pt/Co3O4 Nanosheets for Solar-Driven Overall Water Splitting.

Interfacial engineering is considered an effective strategy to improve the electrochemical water-splitting activity of catalysts by modulating the local electronic structure to expose more active sites. Therefore, we report a platinum-cobaltic oxide nanosheets (Pt/Co3O4 NSs) with plentiful grain boundary as the efficient bifunctional electrocatalyst for water splitting. The Pt/Co3O4 NSs exhibit a low overpotential of 55 and 201 mV at a current density of 10 mA cm-2 for the hydrogen evolution reaction and oxygen evolution reaction in 1.0 M potassium hydroxide, respectively. A negligible degradation of 1.52 V at a current density of 10 mA cm-2 after continuous operation for 100 h, demonstrates the long-term stability of the catalyst. Furthermore, the overall water-splitting performance of the Pt/Co3O4 NSs surpasses that of the commercial Pt/C||RuO2. The density functional theory calculation results explain that the improvement of catalyst activity is attributed to the moderate adsorption/desorption energy of *H and the low reaction energy barrier of the rate-determining step. This work presents a novel vision to design bifunctional catalysts for the storage and conversion of hydrogen energy.

Fractional order control of Wind Energy Conversion System based on DFIG

The paper deals with the elaboration of a robust and efficient decoupled active and reactive powers control algorithm of double-fed induction generator (DFIG) using fractional order control based on proportional and integral controllers. First, the models of wind turbine and electrical generator are established, as well as a decoupled active and reactive powers control of DFIG. Second, the used fractional order controllers are designed using an analytical design method based on frequency domain specifications, namely phase margin, robustness to gain variations and gain limitation at the crossover frequency. Third, to evaluate the fractional order controller control performances, simulation results are presented and discussed for all the operating region of the WECS. Then, simulation results are presented and interpreted considering a variable wind speed in order to reach all the operating regions of the WECS. Finally, a conclusion is given in the light of the obtained results.

COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF NEW CONCEPT HEAT EXCHANGER FOR OTEC APPLICATION

This paper presents a comprehensive analysis of a new concept of heat exchanger for Ocean Thermal Energy Conversion (OTEC) applications. The study utilizes Computational Fluid Dynamics (CFD) simulations to evaluate the performance of different heat exchanger designs for extracting thermal energy from oceanic sources, specifically using water and R717 liquid. Key performance parameters including cold vapor fraction, temperature difference, and pressure drop are evaluated through a combination of numerical simulations and experimental validations. The analysis of the cold vapor fraction provides insights into evaporation rates and their distribution across multiple prototypes, highlighting the impact of the wetted area on heat transfer effectiveness. The evaluation of temperature differences reveals variations in discharge fluid temperatures, with some prototypes deviating from thermodynamic principles at a default evaporation frequency of 0.1. Various evaporation frequencies are simulated and compared with experimental data to select the optimal frequency for each prototype. The simulations and experiments, conducted under similar conditions, ensure accurate validation despite inconsistencies arising from variations in heat exchanger design and boundary conditions. The performance evaluation demonstrates the effectiveness of the three prototypes, with Prototype 2 achieving the highest effectiveness up to 59% for OTEC applications. The findings contribute to a better understanding of heat exchanger performance in OTEC and provide valuable insights for design optimization and future application development. This paper emphasizes the significance of efficient heat transfer and highlights the potential of ocean thermal energy as a renewable and sustainable resource.

Preferentially Stabilizing the Watershed Intermediates by Adsorbate‐adsorbate Interaction to Accelerate CO2 Electroreduction to Ethanol

AbstractReturning CO2 to liquid ethanol powered by clean energy offers considerable economic benefits and contributes to reaching the goal of carbon neutrality, but it remains a formidable challenge to achieve high ethanol selectivity due to the inevitable strong competition among various pathways. Herein, an investigation is presented to accelerate CO2 electroreduction to ethanol via preferentially stabilizing the precarious watershed intermediates (*CHCOH) by creating strong adsorbate‐adsorbate interaction. The highly ordered CuOx nanoplates (HO‐CuOx NPLs) featuring abundant amorphous‐crystalline interface exhibit an exceptional ethanol Faradaic efficiency (FEEtOH) of 63.8% and an ethanol‐to‐ethylene ratio of 6.1 at a large ethanol partial current density (jethanol) of 232.8 mA cm−2. The findings decipher that abundant in‐between nanogaps in the amorphous‐crystalline interface enhance the adsorption of *OH, which can preferentially strengthen C─O bonds while weakening the Cu─C interaction of *CHCOH through adsorbate‐adsorbate interaction, thereby enabling a predilection for CO2 to ethanol conversion. Beyond an efficient ethanol‐oriented CO2RR electrocatalyst, the investigations provide an in‐depth understanding of adsorbate‐adsorbate interaction on key CO2RR steps and precise intermediates regulation, which can be extended to a range of energy conversion technologies.

Heterogeneous Interface Engineering of 2D Black Phosphorus-Based Materials for Enhanced Photocatalytic Performance.

Photocatalysis has garnered significant attention as a sustainable approach for energy conversion and environmental management. 2D black phosphorus (BP) has emerged as a highly promising semiconductor photocatalyst owing to its distinctive properties. However, inherent issues such as rapid recombination of photogenerated electrons and holes severely impede the photocatalytic efficacy of single BP. The construction/stacking mode of BP with other nanomaterials decreases the recombination rate of carriers and extend its functionalities. Herein, from the perspective of atomic interface and electronic interface, the enhancement mechanism of photocatalytic performance by heterogeneous interface engineering is discussed. Based on the intrinsic properties of BP and corresponding photocatalytic principles, the effects of diverse interface characteristics (point,linear, and planar interface) and charge transfer mechanisms (type I, type II, Z-scheme, and S-scheme heterojunctions) on photocatalysis are summarized systematically. The modulation of heterogeneous interfaces and rational regulation of charge transfer mechanisms can enhance charge migration between interfaces and even maximize redox capability. Furthermore, research progress of heterogeneous interface engineering based on BP is summarized and their prospects are looked ahead. It is anticipated that a novel concept would be presented for constructing superior BP-based photocatalysts and designing other 2D photocatalytic materials.

Modeling Diffusive Motion of Ferredoxin and Plastocyanin on the PSI Domain of Procholorococcus marinus MIT9313.

Diffusion of mobile charge carriers, such as ferredoxin and plastocyanin, often constitutes a rate-determining step in photosynthetic energy conversion. The diffusion time scales typically exceed that of other primary bioenergetic processes and remain beyond the reach of direct simulation at the molecular level. We characterize the diffusive kinetics of ferredoxin and plastocyanin upon the photosystem I-rich domain of Prochlorococcus, the most abundant phototroph on Earth by mass. A modeling approach for ferredoxin and plastocyanin diffusion is presented that uses ensembles of coarse-grained molecular dynamics simulations in Martini 2.2P with GROMACS 2021.2. The simulation ensembles are used to construct the diffusion coefficient and drift for ferredoxin and plastocyanin as spatial functions in the photosystem I domain of the MIT9313 ecotype. Four separate models are constructed, corresponding to ferredoxin and plastocyanin in reduced and oxidized states. A single scaling constant of 0.7 is found to be sufficient to adjust the diffusion coefficient obtained from the Martini simulation ensemble to match the in vitro values for both ferredoxin and plastocyanin. A comparison of Martini versions (2.2P, 2.2, 3) is presented with respect to diffusion scaling. The diffusion coefficient and drift together quantify the inhomogeneity of diffusive behavior. Notably, a funnel-like convergence toward the corresponding putative binding positions is observed for both ferredoxin and plastocyanin, even without such a priori foreknowledge supplied in the simulation protocol. The approach presented here is of relevance for studying diffusion kinetics in photosynthetic and other bioenergetic processes.

Regenerative Biomimetic Photosynthesis by Covalent-Organic Framework-Based Nanobiohybrids.

Biomimetic photosynthesis, which leverages nanomaterials with light-responsive capabilities, represents an innovative approach for replicating natural photosynthetic processes for green and sustainable energy conversion. In this study, a covalent-organic framework (COF)-based artificial photosynthesis system is realized through the co-assembly of adenosine triphosphate (ATP) synthase and a light-responsive proton generator onto an imine-based COF, RT-COF-1. This system demonstrates an ATP production rate of 0.64 µmol ATP per mg protein within 90 s of light exposure and, for the first time, exhibites regenerative ATP production through multiple light on/off cycles. Furthermore, the ATP generated by the system facilitates the biocoupling of monosaccharides into disaccharides, confirming the hybrid system's capability to convert solar energy into chemical energy in the form of organic molecules. This approach shows significant potential for renewable bioenergy generation, offering precise and reliable control over biochemical processes through artificial photosynthesis.

Exogenous Application of Lanthanum Chloride to Rice at Booting Stage Can Increase Chlorophyll Content, Modulate Chlorophyll Fluorescence and Promote Grain Yield Under Deficit Irrigation

To sustain agricultural productivity and safeguard global food security, and confront the escalating challenges posed by climate change and water scarcity, it is essential to enhance the growth and productivity of rice under water stress. This study investigated the effects of lanthanum chloride on the chlorophyll fluorescence characteristics and grain yield of rice under different irrigation modes. The rice cultivar H You 518 was selected and sprayed 20, 100, or 200 mg·L−1 lanthanum chloride at the booting and heading stages under deficit irrigation (where no rewatering was applied after the initiation of stress, allowing the water layer to evaporate naturally under high temperatures) or conventional irrigation (with daily rewatering to maintain a consistent water level). The results showed that the application of low concentrations lanthanum chloride promoted the chlorophyll content, whereas high concentrations decreased the chlorophyll content, under deficit irrigation, the effect of lanthanum chloride on the green fluorescence parameters of rice leaves at the booting stage was greater than that at the heading stage, and the booting stage was more sensitive to water deficit. The application of 100 mg·L−1 lanthanum chloride reduced the initial fluorescence (F0) and the non-photochemical quenching coefficient (qN); promoted the activity of leaf photosynthetic system II (PSII); and maximized the photochemical quantum yield (Fv/Fm), photochemical quenching coefficient (qP), and PSII relative electron transfer efficiency (ETR). Under deficit irrigation, this treatment significantly enhanced grain yield by increasing the thousand-grain weight, spikelet filling rate, and number of grains per panicle. These results suggest that spraying 100 mg·L−1 lanthanum chloride at the booting stage under deficit irrigation can effectively increase the chlorophyll content, thereby increasing the light energy conversion efficiency of the PS II reaction center, ultimately resulting in increased spikelet filling rate and grain yields.

In situ and operando characterization techniques for nanocatalyst-based electrochemical hydrogen evolution reactions

The hydrogen evolution reaction is important in energy conversion and storage. This has led to the design of different types of catalysts and production setups. Understanding the status of the catalysts and reaction mechanisms motivated researchers to adopt the operando/in situ techniques. Herein, we present a brief overview of the recent (from 2020) advances in the use of in situ and operando characterization techniques, such as in situ X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis, IR spectroscopy, electrochemical Raman spectroscopy, online inductively coupled plasma - mass spectro­scopy, differential electrochemical mass spectroscopy, optical microscopy, electron micro­scopy, electrochemical atomic microscopy, electrochemical scanning tun­neling microscopy, and scanning electrochemical microscopy, in the electrochemical hydro­gen evolution reaction. Representative examples of the applications of these techniques are also provided. Challenges in this field and future perspectives are discussed.

Entropy Production in an Electro-Membrane Process at Underlimiting Currents—Influence of Temperature

The entropy production in the polarization phenomena occurring in the underlimiting regime, when an electric current circulates through a single cation-exchange membrane system, has been investigated in the 3–40 °C temperature range. From the analysis of the current–voltage curves and considering the electro-membrane system as a unidimensional heterogeneous system, the total entropy generation in the system has been estimated from the contribution of each part of the system. Classical polarization theory and the irreversible thermodynamics approach have been used to determine the total electric potential drop and the entropy generation, respectively, associated with the different transport mechanisms in each part of the system. The results show that part of the electric power input is dissipated as heat due to both electric migration and diffusion ion transports, while another part is converted into chemical energy stored in the saline concentration gradient. Considering the electro-membrane process as an energy conversion process, an efficiency has been defined as the ratio between stored power and electric power input. This efficiency increases as both applied electric current and temperature increase.

Design, Implementation, and Analysis for Reducing Energy Losses in Solar Inverters through the Use of SiC MOSFETs

The integration of Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) in solar inverters has emerged as a promising solution for enhancing energy conversion efficiency. This study presents the design and performance analysis of a high-efficiency solar inverter utilizing SiC MOSFETs, targeting increased power output and improved reliability in photovoltaic (PV) systems. The proposed inverter design focuses on reducing switching losses, minimizing heat dissipation, and achieving higher switching frequencies compared to traditional silicon-based devices. The adoption of SiC technology enables reduced conduction and switching losses due to its superior thermal properties and high breakdown voltage, making it ideal for solar inverter applications. Simulation results demonstrate significant improvements in efficiency—exceeding 98%—under varying load conditions. Additionally, the inverter’s performance was evaluated in terms of total harmonic distortion (THD), with values well within acceptable limits, ensuring clean and stable power output. The thermal management capabilities of SiC MOSFETs are also highlighted, showing reduced heat sink requirements and longer operational lifetimes. This research further explores the practical implementation challenges, such as gate driver considerations and EMI suppression, to optimize inverter design for real-world scenarios. The findings suggest that utilizing SiC MOSFETs in solar inverters not only enhances energy efficiency but also contributes to system compactness, potentially reducing the overall cost of PV installations. The study concludes with recommendations for future developments in SiC-based power electronics for renewable energy applications.

OPTICAL, MORPHOLOGICAL, STRUCTURAL, AND PHOTOCATALYTICAL PROPERTIES OF PLASMONIC AU NPS PRODUCED BY PULSED LASER DEPOSITION

Plasmonic Au NPs exhibit exceptional optical, morphological, and structural properties, making them promising materials for applications in photocatalysis, sensing, and energy conversion. This study explores the synthesis and characterization of plasmonic gold NPs produced by pulsed laser deposition, a versatile physical vapor deposition technique. Pulsed Laser Deposition enables precise control over NP formation through tunable parameters such as laser fluence, ambient gas environment, and deposition duration. The resulting NPs were systematically analyzed to evaluate their optical properties, including localized surface plasmon resonance, as well as their morphological and structural attributes. The localized surface plasmon resonance behavior of the synthesized Au NPs was found to be highly dependent on particle size, shape, and distribution, as revealed by UV-Vis spectroscopy and electron microscopy. Structural analysis via X-ray diffraction confirmed the crystalline nature of the NPs, with lattice parameters correlating to their stability and catalytic efficiency. Photocatalytic activity tests demonstrated that the gold NPs could effectively degrade organic pollutants under visible light, leveraging their strong LSPR-induced hot electron generation and charge transfer properties. In this study, gold NP thin film was produced on microscopic glass by Pulsed Laser Deposition system. Gold NPs thin film photocatalyst efficiency 95.00% and reaction rate constant 0.39 min-1 were calculated. At the end of 210 min, MB dye was degraded and turned into high transparency due to localized surface plasmon resonance property of gold NP. The findings may provide valuable insights into the design and application of plasmonic Au NPs in photocatalysis and other advanced technologies.

Clarifying the Active Structure and Reaction Mechanism of Atomically Dispersed Metal and Nonmetal Sites with Enhanced Activity for Oxygen Reduction Reaction

AbstractAtomically dispersed transition metal (ADTM) catalysts are widely implemented in energy conversion reactions, while the similar properties of TMs make it difficult to continuously improve the activity of ADTMs via tuning the composition of metals. Introducing nonmetal sites into ADTMs may help to effectively modulate the electronic structure of metals and significantly improve the activity. However, it is difficult to achieve the co‐existence of ADTMs with nonmetal atoms and clarify their synergistic effect on the catalytic mechanism. Therefore, elucidating the active sites within atomically dispersed metal‐nonmetal materials and unveiling catalytic mechanism is highly important. Herein, a novel hybrid catalyst, with coexistence of Co single‐atoms and Co─Se dual‐atom sites (Co─Se/Co/NC), is successfully synthesized and exhibits remarkable performance for oxygen reduction reaction (ORR). Theoretical results demonstrate that the Se sites can effectively modulate the charge redistribution at Co active sites. Furthermore, the synergistic effect between Co single‐atom sites and Co─Se dual‐atom sites can further adjust the d‐band center, optimize the adsorption/desorption behavior of intermediates, and finally accelerate the ORR kinetics. This work has clearly clarified the reaction mechanism and shows the great potential of atomically dispersed metal‐nonmetal nanomaterials for energy conversion and storage applications.