Energy Conversion Efficiency Research Articles

Environmental performance of a multi-energy liquid air energy storage (LAES) system in cogeneration asset – A life cycle assessment-based comparison with lithium ion (Li-ion) battery

Increase in energy demand is shaping both developed and developing countries globally. As a result, the endeavour to reduce carbon emissions also encompasses electrical energy storage systems to ensure environmentally friendly power production and distribution. Currently, the scientific community is actively exploring and developing new storage technologies for this purpose. The focus of this work is to compare the eco-friendliness of a relatively novel technology such as liquid air energy storage (LAES) with an established storage solution such as Li-Ion battery (Li-ion). The comparison is carried out through Life Cycle Assessment (LCA) methodology which aims to assess the environmental impacts from each life stage, according to different impact categories. In particular, the study refers to the unitary storage and the delivery of electricity as well as cooling energy, considering all the inefficiencies and limits of each technology. The results show that in the full electric case study Li-ion battery environmentally outperform LAES due to (1) the higher round trip efficiency and (2) the significantly high environmental impact of the diathermic oil utilized by LAES, accounting for 92 % of the manufacture and disposal phase. Conversely, the cogeneration case study highlights that the “flexibility” and “dualism” of LAES, capable to efficiently deliver both electricity and cooling, offset the impact related to the higher electricity consumption during the use phase. Notably in energy mix frameworks with high share of primary energy source from fossil fuels, cogenerative LAES demonstrates superior environmental performance compared to Li-ion battery (i.e. 1302 kgCO2eq/MWhe vs 1140 kgCO2eq/MWhe for Singapore energy mix), attributable to its reduced electricity consumption.

Efficiency limits of concentrated solar thermophotonic converters under realistic conditions: The impact of nonradiative recombination and temperature dependence

A concentrated solar thermophotonic converter (CSTC) that efficiently harvests the entire solar spectrum under non-ideal conditions is proposed. This device includes an optical concentrator, a solar absorber, a GaAs light-emitting diode (LED) on the hot side, and an InP photovoltaic (PV) cell on the cold side. The electric power generated by the PV cell is utilized to positively bias the heated LED, resulting in a substantial increase in LED emission power. A comprehensive theoretical model is developed to accurately predict the output electrical performance and overall energy conversion efficiency of the CSTC device, especially considering the impact of the nonradiative recombination and temperature dependence. The calculated results show that when the solar concentrating factor is 30, and the LED and PV cell voltages are 0.989 V and 1.13 V, respectively, the overall peak efficiency can reach 12.8% and the corresponding output power density is 384 mW cm−2, achieving performance metrics nearly 4 orders of magnitude higher than solar thermophotovoltaics (TPV). Additionally, increasing the solar concentration ratio and decreasing the thickness of the semiconductor materials can further improve the overall output performance. This work reveals that CSTC offers several advantages over solar TPV, including more efficient conversion of narrow-spectrum electroluminescence, higher radiated power from the LED emitter, and the ability to operate at lower solar concentrations and lower costs.

Nitrogen-doped carbon embedded with heterostructured Co3Fe7-Co5.47N nanoalloys for electrocatalytic oxygen reduction reaction in zinc-air battery

The oxygen reduction reaction (ORR) is the cathodic process in zinc-air batteries, but its sluggish kinetics significantly limit the energy conversion efficiency of these batteries. Therefore, developing high-performance ORR electrocatalysts is essential to support the advancement of zinc-air battery technology. Herein, a nitrogen-doped carbon embedded with heterostructured Co3Fe7-Co5.47N nanoalloys (FeCo@NC-900) was fabricated, and its electrocatalytic ORR activity and stability of FeCo@NC-900 were investigated in alkaline media. The FeCo@NC-900 catalyst exhibited a half-wave potential of 0.84 V, a Tafel slope of 76.06 mV·dec−1, and an electron transfer number (n) of approximately 3.83 for ORR. A rechargeable zinc-air battery was assembled using FeCo@NC-900 as the air cathode, achieving an open-circuit voltage of 1.435 V and a maximum power density of 81 mW cm−2, along with good cycling stability.

Surface functionalized porous MXene (Ti3C2Tx)/Polyethyleneimine membrane for efficient osmotic energy conversion

The development of ion-selective membranes is crucial for achieving efficient osmotic power conversion in reverse electrodialysis system. However, balancing ion selectivity and ion permeability in membranes remains a challenge, limiting improvements in energy conversion efficiency for practical applications. In this study, we develop efficient cation exchange membranes by integrating versatile aromatic hydroxyl groups with MXene nanosheets and polyethyleneimine (PEI) into their lamellar structure. This approach holds promise for achieving non-swelling, high selectivity, and enhanced power density for osmotic energy conversion. The abundance positive surface charge within PEI molecules, combined with the 2D sub-nanochannels of MXene nanosheets, facilitates the biomimetic replication of channel size, chemical groups, and adjustable charge density in the resulting membranes. The fabrication of these membranes is easily achieved through simple hydrothermal, functionalization, and surface-charged techniques, suggesting promising scalability. These membranes exhibit remarkable stability against swelling in aqueous solutions for up to 25 days and demonstrate a high selectivity of 0.95 and a superior output power density of 18.3 W/m2 in artificial river water and seawater.

Simulasi karakteristik mesin termoakustik pembangkit listrik dengan penambahan model kerugian minor dari dua segmen konis

Acoustic energy output level from regenerator segment of a thermoacoustic engine model is attenuated along it’s loop due to several conditions including minor losses. This article discusses the result of Delta EC simulation of a thermoacoustic engine model acting as simple electric power generator that inserted with two conical segments. The cone segments are capable to lower the energy loss which in turn improve the overall performance of the engine in term of nett heat to acoustic energy conversion efficiency. Combined acoustic energy loss induced by both cones is equivalent to 4.94 watts minor losses. At this condition, regenerator segment amplifies the incoming acoustic energy flow of 57.02 watt up to 93.57 watt, which is equals to 36.55 watts acoustic amplification. It leads to increasing of overall engines heat to acoustic efficiency into 14.05%, which is 1.29% higher than those at the case of without cones. This engine performance improvement addressed to smoother streamline of working fluid flow inside the loop.

Enhanced Antireflection and Absorption in Thin Film GaAs Solar Cells Using Dielectric Composite Nanostructures

This study investigates the application of dielectric composite nanostructures (DCNs) to enhance both antireflection and absorption properties in thin film GaAs solar cells, which are crucial for reducing production costs and improving energy conversion efficiency in photovoltaic devices. Building upon previous experimental validations, this work systematically explores the underlying theoretical mechanisms using the finite difference time domain (FDTD) method to analyze the light interaction with the proposed DCNs. The results show that the combination of Mie resonance, Fabry–Perot resonance, and guided resonance, induced by the surface structuring of the DCNs, significantly enhances light absorption in the active layer, particularly at longer wavelengths. For solar cells featuring a 500-nm-thick absorber layer, SARL-decorated solar cells demonstrated an average reflectivity of 12.18%, whereas those incorporating DCNs exhibited a significantly reduced average reflectivity of 4.52%. These findings indicate that DCNs structures are highly effective in enhancing the performance of thin and ultra-thin GaAs solar cells by minimizing surface reflection and increasing photon utilization, offering a promising solution for high efficiency, cost effective photovoltaic devices.

Strategy for enhancing energy conversion efficiency and cyclist helmet safety: A theoretical and experimental study of diverse thermoelectric generator models

Recent studies have focused on Thermoelectric Generators (TEGs) as a key to sustainable energy, using thermal power through temperature differentials to produce electric power. Despite the promise of TEGs, there is diversity of TEG models and the shortage of comprehensive evaluations on energy conversion. In particular, measuring the output of electrical energy and time of production across temperature variances, which has impeded their broad adoption. This research conducted a comprehensive analysis of TEG models. It used a new test rig designed in SolidWorks and actualized, coupled with MATLAB simulations to validate the predicted results. This includes developing a wearable device such as a helmet-mounted warning light for motorcyclists or cyclists. In the study, five different thermoelectric generator models (TEG1-12703, TEG1-12706, TEG1-12709, TEG1-12712, and TEG1-12715) were tested, these models showed varying power outputs of 66.46, 97.51, 117.5, 191.72 and 358.74 mW. Their efficiencies were 1.78 %, 1.982 %, 2.097 %, 2.567 % and 2.93 %, respectively, when ΔT reaches 30 °C. The experimental and theoretical data indicate discrepancies in results and thermal response delays due to heat transfer and energy conversion within the test rig’s layers. These discrepancies were addressed to adjust simulations closer to reality. A differential correction ratio (19.133 % for power, 17.94 % for efficiency) was applied to enhance prediction accuracy. After adjustment, the maximum power generation reached 1.64355, 2.8386, 3.83433, 4.6843, 4.96746 W. The maximum efficiency peaked at 2.236, 3.59462, 4.1184, 6.278154, 6.75779 %, respectively, when ΔT reaches 70 °C. The output power and efficiency from these TEGs could run certain sensors.The study shows that TEG model 12,715 excels in generating electrical energy with large temperature differences. However, its output nearly vanished under a 1 °C differential, ending tests prematurely. In contrast, the model 12,703 consistently generates electricity over long periods (more than 420 min) under minimal temperature differential, while it is unable to produce high power under greater differentials. This suggests that using diverse TEG models and integrating together to enhance the efficiency and continuity of free energy generation, depends on the models’ varied performance and temperature differences. Utilizing the results, five TEG units connected in parallel were installed on a cyclist’s helmet to power a rear warning light, this installation enhances night-time safety. These TEG models demonstrated continuous power generation, producing an average of 55.7 mW per hour with a temperature difference ΔT between 3.2 °C and 7.4 °C.

Development, process optimization and assessment of sustainable mobile biochar kiln for agricultural use

A novel and energy-efficient biochar kiln that can be operated in the field with few requirements has been developed. The generated syngas are recirculated into the combustion chamber to heat biomass. This study optimized the feedstock parameters, biochar yield, and economics of producing biochar from soybean straw using the Response Surface Methodology (RSM) based on Central Composite Design (CCD). The biochar kilns had an energy conversion efficiency of 47.02% and an overall kiln efficiency of 41.03% at steady-state operation over 500 °C. It produced an average of 29.43 ± 1.42% biochar with a minimal fuel-to-biochar ratio of 0.19 ± 0.02 and a payback period of 4.02 months. The statistical analysis confirmed that the characteristics of the feedstock affect the biochar output and economic aspects of the biochar production process. Based on the optimization studies, it was concluded that the feedstock's moisture content should be 8% and particle size should be 15 mm for higher biochar yield with maximum energy efficiency and benefit-cost ratio. Biochar produced at optimal conditions obtained from the optimization process was also characterized. Physical-chemical analysis reveals that biochar has a higher carbon content (79.38 ± 1.04 %) and a lower atomic ratio of H/C (0.696), O/C (0.14), and (N + O)/C (0.08), indicating higher carbon stability and aromaticity. The TGA analysis demonstrated the high thermal stability of biochar by showing a lower (2.15%) mass loss between the 343.8 and 407.1 °C temperature range. The SEM and TEM micrographs showed the microporous structure of the soybean straw biochar with a worm-like pattern and a cylindrical shape.

Fabrication and evaluation of a CMOS-based energy harvesting chip integrating photovoltaic and thermoelectric energy harvesters

This study explores the development of an energy harvesting chip (EHC) using a complementary metal oxide semiconductor (CMOS) process, addressing the need for efficient micro-scale energy harvesters in modern electronics. The EHC integrates a thermoelectric energy harvester (TEH) and a photovoltaic energy harvester (PEH) to maximize energy conversion efficiency. A key challenge in TEH design is enhancing power output, which is addressed by suspending the cold ends of 41 thermocouples within the TEH structure through post-processing. Experimental methods were employed to assess the performance of the TEH, revealing an output voltage of 21.4 mV and a maximum output power of 9.32 nW under a 3 K temperature difference. The TEH demonstrated a voltage factor of 8.9 mV/(mm2·K) and a power factor of 1.3 nW/(mm2·K2). The PEH was designed with novel patterned p-n junctions, integrating lightly doped n-type regions with interdigitated p-type doping to increase junction density, resulting in high conversion efficiency. The experimental results confirm the effectiveness of the EHC design, showcasing its potential in energy harvesting applications.

High-performance Sr1.9Fe1.45Pd0.05Mo0.5O6−δ electrode for reversible symmetrical solid oxide cells

Reversible symmetrical solid oxide cells (RS-SOCs) have attracted much attention due to their high energy conversion efficiency and fabrication simplicity. The double perovskite with the general formula A2BB’O6 is often used as the electrode material. In this study, Fe was substituted with Pd in the B-site of Sr1.9Fe1.5Mo0.5O6−δ to enhance the electrochemical performance above 50 %. The characterization results showed that the doping of Pd promoted the kinetics of the electrode reaction and thus improved the electrochemical activity. A maximum power density of 870 mW cm−2 at 800 ℃ on a La0.9Sr0.1Ga0.8Mg0.2O3–δ (LSGM)-supported symmetrical cell with Sr1.9Fe1.45Pd0.05Mo0.5O6-δ electrode was achieved in the solid oxide fuel cells (SOFCs).

Enhanced performance of polydimethylsiloxane-based triboelectric nanogenerator using BaTiO3/MWCNTs

Triboelectric nanogenerators (TENGs) that operate in the contact-separation mode are widely utilized for energy harvesting owing to their simple structure, excellent durability, and high energy-conversion efficiency. This study investigated the enhanced performance of TENGs using polydimethylsiloxane (PDMS) incorporating barium titanate (BTO) and multiwalled carbon nanotubes (MWCNTs). The negative triboelectric layer, comprising PDMS with BTO and MWCNTs, and aluminum foil as both the positive triboelectric layer and electrode, were optimized to improve the TENG performance. The optimal composition of PDMS incorporating 0.01 wt% MWCNTs and 10 wt% BTO yielded output voltage and current of 394.75 V and 28.24 µA, respectively. Further enhancement was realized via the application of radio frequency plasma treatment, which increased the surface roughness and fluorine incorporation. Consequently, the output voltage and current improved to 421.06 V and 32.33 µA, respectively, with a peak power density of 4.76 W/m2 at 10 MΩ. The optimized TENG maintained consistent performance over 2000 cycles and successfully illuminated commercial LEDs, thereby demonstrating its potential for practical energy-harvesting applications.

Solid-liquid flow characteristics of twin-screw pump under solid-containing transportation

Abstract Twin-screw pumps have the wear risk when the fluid contains particles. In order to clarify the flow characteristics of the twin-screw pump under solid-containing transportation, the solid-liquid flow characteristics research on a twin-screw pump are carried out using numerical simulation and experimental methods in this paper. The results show that the particle concentration has a small effect on the volumetric efficiency and hydraulic efficiency of the twin-screw pump under each differential pressure, but the presence of particles could increase the volumetric efficiency limitedly. The velocity of main flow and the turbulent kinetic energy have been restrained by the particles in the tooth chamber, and the inhibition phenomenon is more significant with the increase of particle concentration. The particles in the tooth chamber are inhaled by the leakage flow at the tooth-tip clearance. Some particles hit the tooth-tip and cause the abrasion, others flow into the tip clearances, which decreases the leakage flow velocity and results in a higher volumetric efficiency than that of the pure-liquid condition. The results of the study will provide a theoretical basis for the study of solid-containing transportation and particle wear in twin-screw pumps.

Experience in Monitoring Brazed Aluminium Heat Exchanger, after Major Repairs

Brazed Aluminium Heat Exchangers are fundamental for a natural gas liquid recovery plant. Refrigeration at cryogenic temperatures and the liquefaction process take advantages from their thermal hydraulic efficiency and compactness characteristics, making such units economically feasible. These exchangers are proprietary design, with only a few manufacturers around the world and limited knowledge about their maintenance. After two failures in the same equipment with possible thermal fatigue contributions, occurring only nine months apart, two complex repair procedures had to be carried out. To ensure operational safety, online monitoring through Acoustic Emission Technique has been performed. This monitoring led to discoveries of systems and routine maneuverer that triggered damage mechanisms. This allowed for the implementation of adjustments to mitigate the propagation of damage, thereby increasing the equipment's lifespan. The procedure applied in this type of equipment constitutes an innovative approach using the Acoustic Emission technique, which has resulted in a successful strategy of condition monitoring.

Effect of Axial Clearance Between Turbine and Guide Wheel on Hydraulic Performance of Mine Borehole Turbo Generator

Abstract In order to study the influence law of axial clearance between turbine and guide wheel on the performance of mine turbine generator. The three-dimensional unsteady internal flow and external characteristics of 8 kinds of turbine generator models with different coaxial clearance are calculated. The results show that: As the axial clearance coefficient between the turbine and the guide wheel increases, the pressure loss at the inlet and outlet of the guide wheel and turbine increases gradually, the torque and shaft power of the turbine are reduced, the hydraulic efficiency of turbine generator decreases gradually; The hydraulic efficiency of the turbine increases first and then decreases. Considering the external and internal flow characteristics comprehensively, the axial clearance coefficient between the turbine and the guide wheel is between 0.12 and 0.15, and the turbine generator performance is the best. It can provide some reference for the design optimization of Mine Borehole Turbo Generator.

Analysis of submersible axial flow pump fitted with variable IGV at design and off-design conditions

Abstract Submersible axial flow pump is capable of generating large flow rate at high efficiency and is widely used in agriculture, irrigation, water supply and drainage in factories, urban areas, etc. Pumps are always designed to operate at the designed conditions of flowrate and head, but in certain practical applications, their off- design operation seems to be more important, like if there is waterflooding due to heavy rainfall or in case of variable flowrate, variable head operations or long-distance water supply. These situations arise for limited operation (time) and hence it is not economical to change the existing pumping system. The present work deals with the analysis of submersible axial flow pump at design as well as off-design conditions. This off-design operation was controlled by the variable inlet guide vane (VIGV) with the task of making it energy efficient for all conditions. The scope of this work was to investigate the performance of selected pump at designed rotational speed, at designed flowrate (Q/Qd =1) as well as Q/Qd =0.8 and Q/Qd =1.2, using Computational Fluid Dynamics (CFD) and at various VIGV angles in the range of ±25°. The fluid flow analysis was performed using commercial CFD tool ANSYS CFX v17.0. From the numerical study, it was concluded that the performance of the considered AFP significantly increased due to the presence of VIGV at positive rotation angles. The best performance was observed for IGV angle of +25° for all flowrates. As compared to the reference case of 0° IGV rotation, the performance of the AFP increased by 28.42% in terms of head ratio and 0.235% in terms of hydraulic efficiency, for +25° IGV angle, at the designed flowrate. Also, an increment of 69.05% in terms of head ratio and 14.49% in terms of hydraulic efficiency was observed at overload condition of Q/Qd =1.2.

Application of drag reduction agents as a method for reducing heat loss during pumping through a pipeline

Relevance. The need to maintain the temperature regime of product pumping under increasingly complex conditions of pipeline routes by reducing heat losses of oil and petroleum product pipelines, as well as expanding the scope of application of anti-turbulence additives. Aim. To determine the effect of anti-turbulence additives on heat and hydraulic losses in the pipeline and to propose cost-effective ways to use additives when pumping through pipelines. Objects. Heat and hydraulic losses in pipelines pumping oil and oil products. Methods. Mathematical analysis of the influence of anti-turbulence additives on the thermohydraulic properties of the flow to assess the prospects for increasing the energy efficiency of pumping liquid through pipelines by introducing polymer additives. Results. The flow temperature was calculated using anti-turbulence additive depending on its concentration and efficiency, taking into account the dependence of the properties of the pumped product on temperature. The authors have constructed the graphic dependences of the economic components of heat and hydraulic losses on the concentration of anti-turbulence additives. The economic feasibility of the decision was estimated in terms of calculating the difference in pumping costs with and without anti-turbulence additives. The authors identified the relationship between the impact of losses from friction heat and heat exchange with the environment on heat losses, and analyzed the change in these parameters after the introduction of anti-turbulence additives. For the pipeline under consideration, the parameters of which correspond to standard pumping ones, the сonclusions were drawn on the predominance of the contribution of the additive hydraulic efficiency over the thermal one. This indicates the advisability of using an anti-turbulence additive as an agent for reducing heat losses at high values of the efficiency of the polymer additive, however, the overall economic efficiency is maximum at lower concentrations of the agent. The authors constructed a planar graph reflecting the dependence of the temperature at the end of the pipeline section on two coordinates: the length of the section and the hydraulic efficiency of the introduced additive.

From waste to wonder: Developing engineered nanomaterials for multifaceted applications

The escalating generation of industrial and consumer waste poses a significant environmental challenge, necessitating innovative approaches to waste management and resource utilization. One promising solution lies in the transformation of waste materials into engineered nanomaterials (ENMs), which hold immense potential for a diverse range of applications. This review explores the development of ENMs from waste, highlighting their multifaceted uses in environmental remediation, energy storage, medical applications, and advanced manufacturing. The process of converting waste into ENMs involves sophisticated techniques such as chemical vapour deposition, sol-gel synthesis, and hydrothermal methods, which enable the creation of materials with precise structural and functional properties at the nanoscale. By utilizing waste as a raw material, this approach not only addresses waste disposal issues but also provides a sustainable and cost-effective source of high-value nanomaterials. ENMs derived from waste exhibit unique properties, including high surface area, tunable porosity, and enhanced reactivity, making them suitable for environmental applications such as pollutant adsorption, water purification, and air filtration. In the energy sector, these nanomaterials contribute to the development of advanced batteries, supercapacitors, and fuel cells, enhancing energy storage and conversion efficiency. The biomedical field benefits from waste-derived ENMs through their application in drug delivery systems, diagnostic tools, and tissue engineering. The biocompatibility and functional versatility of these materials enable targeted therapeutic interventions and innovative medical solutions. Furthermore, in advanced manufacturing, ENMs improve the performance and durability of materials used in electronics, coatings, and composites, fostering the development of next-generation products with superior properties. The integration of waste-derived ENMs into various industries represents a paradigm shift towards a circular economy, where waste is not merely a byproduct but a valuable resource. This approach aligns with global sustainability goals, promoting resource efficiency, reducing environmental impact, and driving technological advancements. In conclusion, the development of engineered nanomaterials from waste exemplifies the transformative potential of nanotechnology in addressing critical environmental and industrial challenges. By harnessing waste as a resource, this innovative approach paves the way for multifaceted applications that contribute to environmental sustainability, technological progress, and economic growth. Further research and development in this field will continue to expand the possibilities and impact of waste-derived ENMs in various sectors.

CALCULATION TO DETERMINE THE TECHNICAL AND ECONOMIC EFFICIENCY OF PUMPING UNITS FOR LIFTING WATER FROM WATERCOURSES POWERED BY WATER ENERGY FOR WATERING PASTURES AND IRRIGATION OF LAND

The problem of effective water supply using natural energy resources of water in modern conditions is promising and relevant, the solution of which is rationally carried out from watercourses with the necessary standard sizes of a hydraulic ram pumping unit, the design of which has a novelty. At the Kazakh National Agrarian Research University conducted applied research to improve the efficiency of water supply from watercourses in the system of irrigation of lands and irrigation of pastures of peasant and farm farms of the agro-industrial complex of the Republic of Kazakhstan through the development of an improved hydraulic ram pumping unit with an increase in its energy indicators: hydraulic shock pressure, supply, pressure and efficiency. This article presents a calculation to substantiate the economic efficiency of the studies carried out on the use of the necessary standard sizes of an improved hydraulic ram pumping unit (NUV-7-12 and NUV-17-20) for water supply to peasant and farm farms of the Republic of Kazakhstan and irrigation of lands located in areas of adjacent watercourses, compared with basic pumping units (AN - 2K - 9 - M1 and ANS-60 D).

Charge Transfer Kinetics and Thermodynamics Control the Energy Conversion Efficiency of a Gallium Phosphide Solar Hydrogen Photocathode.

P-type gallium phosphide (GaP) photocathodes for hydrogen evolution from water have a theoretical energy conversion efficiency of 12% based on the 2.4 eV optical band gap of the material. The performance of actual GaP photocathodes is much lower, for reasons not entirely clear. Here we use vibrating Kelvin probe surface photovoltage (VKP-SPV), open circuit potential (OCP) measurements, and photoelectrochemical (PEC) experiments to evaluate the kinetic and thermodynamic factors that control energy conversion with GaP photocathodes for the hydrogen evolution reaction (HER). We find that the open circuit photovoltage of the bare GaP-H2O junction is limited by recombination at surface states and that an CdS overlayer increases both photovoltage and photocurrent due to formation of a n-p-junction. An optimized GaP/CdS/Pt photocathode drives hydrogen evolution with a quantum efficiency of 62% at 400 nm and 0.0 V RHE and an open circuit photovoltage of 0.43 V at 250 mW cm-2. The Pt cocatalyst increases the photocurrent due to improve HER kinetics but reduces the photovoltage by promoting recombination. Added hydrogen or oxygen gas raise or lower the photovoltage by modifying the electrostatic barrier (band bending) in GaP. This shows that the GaP/CdS junction is not "buried" but behaves like a Schottky junction whose charge separating properties are controlled by the electrochemical potential of the electrolyte. The dynamic junction properties need to be considered in the design of optimized hydrogen evolution photoelectrodes and photocatalysts. Additionally, the work reveals that PEC or OCP measurements tend to underestimate the photovoltage because they do not account for changes in the electrochemical potential at the electrode-liquid contact. In contrast, the VKP-SPV method provides the open circuit photovoltage value directly. By combining the photovoltage data with OCP data, the minority carrier electrochemical potential at the electrode-liquid contact can be measured in a contactless way. This provides an improved understanding of illuminated photoelectrodes for the production of solar fuels.

Flexible Thermoelectric and Piezoelectric Hybrid Energy harvester by Adopting a Multifunctional Cellulose-based Composite Film

Thermoelectric (TE) and piezoelectric (PE) energy harvesting are the most advantageous conversion mechanisms for converting energy generated by the human body into electrical energy, respectively. However, the development of a hybrid energy harvester is essential for achieving high energy conversion efficiency since a single energy harvester cannot convert enough energy. Herein, we present a flexible TE-PE hybrid energy harvester (f-TPHEH) based on a self-assembled single film consisting of Bi2Te2.7Sn0.3 particles, BaTiO3 nanoparticles, and cellulose. The fabricated f-TPHEH exhibited a maximum TE output power of 18.47 nW and a PE instantaneous output of 13.5 nW under integrated thermal and bending conditions (ΔT = 40 K, bending displacement = 7 mm). We conducted a theoretical analysis using multiphysics simulation based on finite element analysis to support the experimental measurements of the fabricated f-TPHEH. In addition, to demonstrate the mechanical stability of the cellulose matrix-based f-TPHEH, a durability test was performed up to 5,000 cycles of bending deformation. This study presents a method for developing the flexible hybrid energy harvester using a low-cost and simple fabrication process.