Stable Output Power Research Articles

Targeted design strategies for a highly activated carbon cloth cathode/anode to construct flexible and cuttable sodium Ion capacitors with an all-woven-structure

A flexible carbon cloth cathode and anode with high energy storage activity are constructed via targeted strategies using cotton cloth. The assembled all-cloth sodium ion capacitor provides stable power output even under bending/cutting conditions.

Realizing one-step two-electron transfer of naphthalene diimides via a regional charge buffering strategy for aqueous organic redox flow batteries.

Naphthalene diimide derivatives show great potential for application in neutral aqueous organic redox flow batteries (AORFBs) due to their highly conjugated molecular structure and stable two-electron storage capacity. However, the two-electron redox process of naphthalene diimides typically occurs via two separate steps with the transfer of one electron per step ("two-step two-electron" transfer process), which leads to an inevitable loss of voltage and energy. Herein, we report a novel regional charge buffering strategy that utilizes the core-substituted electron-donating group to adjust the redox properties of naphthalene diimides, realizing two electron transfer via a single-step redox process ("one-step two-electron" transfer process). The symmetrical battery testing of NDI-DEtOH revealed exceptional intrinsic stability lasting for 11 days with a daily decay rate of only 0.11%. Meanwhile, AORFBs with NDI-DMe/FcNCl and NDI-DEtOH/FcNCl exhibited a remarkable 40% improvement in peak power density at 50% state of charge (SOC) in comparison to NDI/FcNCl-based AORFBs. In addition, the battery's energy efficiency has increased by 24%, resulting in much more stable output power and significantly improved energy efficiency. These results are of great significance to practical applications of AORFBs.

Comparative circuit analysis for piezoelectric generators in low-power applications

This paper presents the results of experimental analysis of piezoelectric-based power conversion circuits under vibration. Three types of circuits were evaluated: a standard full bridge rectifier (S-FBR) circuit, a self power synchronous electrical charge extraction circuit (SECE-sp), and an optimized self power synchronous charge extraction circuit (SECEopt-sp). Experiments were conducted to evaluate the effectiveness of energy conversion under real operating conditions. The results showed that the SECEopt-sp scheme has the highest energy conversion effectiveness and stable output power, outperforming other tested schemes. The optimum operating parameters of the circuit are identified to ensure minimum energy loss and maximum output power. SECEopt-sp provides maximum output power and stability under varying load conditions. Thus, SECEopt-sp was found to be the most efficient circuit for harvesting energy from low-frequency mechanical vibrations such as water motion or waves.

Topotactic transformation of zeolitic imidazolate frameworks into high-performance battery type electrodes for supercapattery application.

Supercapacitors (SCs) are well recognized for their excessive power output and cycling stability, but they often suffer from limited energy density. A promising solution to this challenge is the hybrid supercapattery (HSC) concept, which integrates two different electrodes with disparate charge-storage systems to provide energy and power. In this work, transition-metal phosphides (TMPs), specifically a Cu-doped cobalt phosphide wrapped with an N-doped porous carbon network (CCP-NPC), were used as positive electrode materials in HSCs. With a specific capacitance of 5.99 F cm-2 and a capacitance retention of 87% after 10 000 cycles, the extremely active CCP-5-NPC (5% Cu-doped cobalt phosphide wrapped with an N-doped porous carbon network) exhibits numerous redox sites. The unique structure of CCP-5-NPC, characterized by its cubical shape, coarse surface, and porous structure, greatly enhances the electrochemically active sites (EAS) and specific surface areas (SSA) of the electrode material, facilitating efficient charge transfer kinetics for ions and electrons in HSCs. The potential hybrid supercapattery (CCP-5-NPC||r-GO device) also demonstrated a higher energy density of 0.563 mW h cm-2 at a power density of 4.8 mW cm-2 at 3 mA cm-2 and a cyclic stability of 87.7% after 10 000 cycles. This work provides a basis for the development of highly efficient HSCs in the future by topotactically converting extremely porous materials into energy storage devices.

Strong misalignment tolerance wireless power transfer with active adjustment of magnetic shielding

The variation of mutual-inductance is the essential reason for fluctuation of transmission power and efficiency during wireless power transfer (WPT) misalign. To maintain output power stability, current methods, such as primary regulation, secondary conversion, magnetic coupling mechanism (MCM) optimization, and compensation topology design, have not changed the characteristic of mutual-inductance changing with misalignment. A strong misalignment tolerance WPT system based on the influence of high permeability magnetic materials on equivalent electrical parameters of MCM is proposed. When the primary and secondary sides of MCM shift, the relative distance between magnetic shielding and coil (RDMSC) is adjusted to maintain the stability of mutual-inductance. The transmission efficiency and power are not affected by misalignment. Alternatively, RDMSC can be actively adjusted to meet the various needs of diverse loads at different times. Simulations and experiments are conducted. The effectiveness of the proposed scheme that RDMSC is actively adjusted to overcome misalignment is verified. This is a new method based on active adjustment of spatial electromagnetic coupling, which provides a new idea for WPT to overcome the influence of misalignment and maintain stable output.

Decoupled tin-silver batteries with long cycle life and power output stability based on dendrite-free tin anode and halide insertion cathode chemistry.

Conventional Ag-Zn batteries have historically faced the challenge of poor cycling stability, rooting in issues associated with Ag cathode dissolution and Zn anode dendrites. Herein, we present a pioneering decoupled Sn-Ag cell, which features two chambers separated by a cation-exchange membrane, containing a dendrite-free Sn metal anode immersed in an alkaline anolyte, and an Ag nanowires/carbon nanotube 3D thick-network cathode in a neutral catholyte. Benefiting from the achieved high electroplating/stripping stability of the metallic Sn anode in the alkaline electrolyte and the electrochemical reversibility of the Ag/AgCl cathode redox couple in the neutral electrolyte, the assembled decoupled Sn-Ag cell demonstrates superior cycling stability, retaining 82.4% of its initial capacity even after 4000 cycles (2 mA cm-2), significantly outperforming both the contrastive decoupled Ag-Zn cell (1500 cycles) and conventional alkaline Ag-Zn batteries (<100 cycles). Furthermore, through the integration of the decoupled Sn-Ag battery with solar cells and power management circuits, an intelligent power system of photovoltaic charging and energy storage was designed, demonstrating its practical viability through maintenance-free charging-discharging during day-night cycles. This research not only significantly increases the lifespan of Ag-batteries with an ultra-flat voltage platform but also opens avenues for the decoupled design of a wide variety of aqueous battery systems.

Unjuk Kerja Mesin Diesel Berbahan Bakar Campuran Biodiesel Jatropha- Jelantah 1:9

In the context of a rapidly growing industry and increasing energy needs, the dwindling sources of fossil fuels prompt the necessity for alternative fuels. This study focuses on the performance of diesel engines running on a blended biodiesel made from jatropha oil and waste cooking oil in a 1:9 ratio. The aim of this study is to investigate the effects of biodiesel fuel made from jatropha oil and waste cooking oil on diesel engine performance and fuel physical properties. The tests include an evaluation of the fuels physical properties, injection characteristics, engine speed, generated power, and specific fuel consumption (SFC). Results indicate that although this blended biodiesel has higher density and viscosity compared to diesel, it offers promising calorific value and spray angle. Moreover, engines using this fuel showed relatively stable engine speeds and power outputs, along with efficient SFC at higher loads. The jatropha-waste cooking oil biodiesel blend shows potential as a sustainable and environmentally-friendly alternative fuel

Current Situation and Engineering Application Prospect of Liquid Air Energy Storage Technology

Liquid air energy storage (LAES)technology is a new-coming energy storage method using cryogenic technology as basic theory. It managed to reach consumption of new energy in a grid-connected way, absorbing low power properly, and stable output of many other forms of energy like industrial gas and electricity. This paper introduces the technical principle and advantages of LAES, analyzes and discusses the problems faced by the development of LAES technology and the corresponding solutions, summarizes the applied fields of LAES technology. It also looks forward to the development direction of LAES technology. LAES has the advantages of high energy storage density and low storage pressure, and is less restricted by geographical conditions. It can store the remaining or discontinuous power for a certain time and produce stable power output. LAES technology has a wide range of application prospects in the power system, providing a variety of energy storage services and market opportunities for the power system, the industrial field, providing a variety of energy recovery, peak-valley balance, emergency backup and energy conversion services for industrial production, and urban gas systems, providing a variety of energy reserve, peak load emergency, emergency backup and auxiliary services for urban gas systems. It is of great significance to improve the phenomenon of "wind abandonment" and "light abandonment" in the power generation industry and meet the demand of "peak cutting and valley filling" in the power grid system.

A flat radiative cooling thermoelectric generator for high performance power generation

Thermoelectric generators (TEGs) based on radiative cooling have attracted significant attention in the energy conversion field because they are energy-independent and pollution-free. However, the development of a thin TEG with high and stable output power is still a challenge. Herein, we demonstrate a flat TEG based on radiative cooling, non-radiative heat transfer cooling, and building waste heat. The flat structure of the designed TEG is thin and enables the non-radiative heat transfer to contribute to the cold end of TEG. A porous Poly(vinylidene fluoride-co-hexafluoropropylene) film, adhered to a copper substrate, is prepared by non-solvent-induced phase separation as the radiative cooling emitter (RCE). The temperature of RCE is 19.9 °C lower than that of the building. To harvest the building waste heat efficiently, a copper plate is designed as the heat collector, which increases the temperature difference between the two ends of TEG to 228 % with respect to one without the heat collector. The uninterrupted output power of the designed TEG matches well with residential electricity and reaches 153.1 mW/m2, which exceeds most previous works. 95 light emitting diodes are lit up successfully by the designed TEG, which shows great potential in off-grid, continuous power-consumed applications.

Performance evaluation of a novel self-tuning particle swarm optimization algorithm-based maximum power point tracker for porton exchange membrane fuel cells under different operating conditions

The power generated by a proton exchange membrane fuel cell (PEMFC) is heavily impacted by the change in membrane water content (MWC) and cell temperature. Since PEMFC stacks exhibit nonlinear characteristics, it is crucial to employ a controller that can accurately track the maximum power point (MPP) and extract the most efficient power from the fuel cell (FC) stack. This article introduces a novel MPP tracking technique, based on a self-tuning particle swarm optimization (ST-PSO) algorithm, to maximize power output from PEMFC under different operational conditions. The performance of the ST-PSO algorithm is evaluated through numerical simulations and compared to four well-known metaheuristic algorithms. The results indicate that the proposed ST-PSO-based MPPT technique surpasses the other metaheuristic methods in terms of extracting the maximum power, achieving fast-tracking, and minimizing power fluctuations in various operating conditions. It attained an MPPT efficiency, consistently exceeding 99.602 % and 99.545 %, while also achieving rapid tracking times of no more than 0.366 s and 0.297 s for the two tested scenarios. Moreover, the ST-PSO controller exhibits robustness and consistent tracking of the MPP. Experimental validation of the ST-PSO controller confirms its robustness and superiority over the other tested algorithm, achieving the highest MPPT efficiency of approximately 98.94 % with a rapid tracking time of 2.0 s. Additionally, it demonstrates the lowest power fluctuations of about 2.26 %, providing a stable power output.

Multi-condition operating characteristics and optimization of a small-scale ORC system

The multi-condition operating characteristics of an organic Rankine cycle (ORC) are crucial to the development of the practical unit. This work developed a steady-state model of a small-scale ORC prototype built and tested in the lab. The influence of heat source/sink parameters, component design, and operation strategies are analyzed. It is found that the optimal output power and thermal efficiency correspond to the similar expander rotating speed but diverse working fluid mass flow rate. The higher mass flow rate is beneficial to the output power whereas deteriorates the thermal efficiency. Heat source temperature and flow rates mainly affect the unit output power while the ambient temperature and humidity influence both the output power and thermal efficiency. The condenser fouling resistance leads to a significant reduction of expander output power and system thermal efficiency. However, the effect of the evaporator fouling resistance could be neglected due to its sufficient redundant area. The long-term climate conditions and operating strategies profoundly impact the unit's off-design performance. The annual constant output power operation can be achieved by adjusting the working fluid mass flow rate. The thermal efficiency of the unit is damaged while pursuing the output power stability in winter and spring.

Towards Sustainable Integration: Techno-Economic Analysis and Future Perspectives of Co-Located Wind and Hydrogen Energy Systems

Abstract This article presents a comprehensive study that focuses on the techno-economic analysis of co-located wind and hydrogen energy integration within an integrated energy system (IES). The research investigates four distinct cases, each exploring various configurations of wind farms, electrolyzers, batteries, hydrogen storage tanks, and fuel cells. To obtain optimal results, the study employs a sophisticated mathematical optimization model formulated as a mixed-integer linear program. This model helps determine the most suitable component sizes and hourly energy scheduling patterns. The research utilizes historical meteorological data and wholesale market prices from diverse regions as inputs, enhancing the study’s applicability and relevance across different geographical locations. Moreover, sensitivity analyses are conducted to assess the impact of hydrogen prices, regional wind profiles, and potential future fluctuations in component prices. These analyses provide valuable insights into the robustness and flexibility of the proposed IES configurations under varying market conditions and uncertainties. The findings reveal cost-effective system configurations, strategic component selections, and implications of future energy scenarios. Specifically comparing to configurations that only have wind and battery combinations, we find that incorporating an electrolyzer results in a 7% reduction in the total cost of the IES, and utilizing hydrogen as the storage medium for fuel cells leads to a 26% cost reduction. Additionally, the IES with hybrid hydrogen and battery energy storage achieves even higher and stable power output. This research facilitates decision-making, risk mitigation, and optimized investment strategies, fostering sustainable planning for a resilient and environmentally friendly energy future.

Evaluation of laser power stability of repeatedly used SubCyclo probe in micropulse transscleral cyclophotocoagulation for glaucoma: A step towards sustainable ophthalmic surgery

Purpose To evaluate the laser power stability of the SubCyclo probe for micropulse transscleral cyclophotocoagulation after repeated use. Materials and methods This experimental study involved 6 new probes. Each probe was connected to the SubCyclo mode (2,000 mW power, 31.3% duty cycle, and 100 seconds duration) of the Vitra 810 laser delivery system (Quantel Medical, France). Laser power measurements were taken using a calibrated laser power meter (Nova, Ophir Optronics Solutions, Israel) every 10 seconds from 10 to 90 seconds during each of the 40 cycles. Intra-rater reliability was assessed using intraclass correlation (ICC). A linear mixed model for repeated measures and pairwise comparisons with Bonferroni adjustment were used for the analysis. Results The mean (SD) power outputs of all probes for the first cycle and all cycles were 421.9 (19.7) mW and 436.7 (16.1) mW, respectively. During the first cycle, the mean (SD) laser power gradually decreased from 444.3 (13.4) mW at 10 seconds to 407.3 (17.0) mW at 90 seconds (Fig 3). For all cycles, the power was 446.0 (13.6) mW at 10 seconds and gradually declined to 426.8 (21.0) mW at 90 seconds. Pairwise comparisons revealed significant differences in mean laser power outputs after 16 cycles of repeated use compared to the first cycle. The ICC estimate (95% CI) for intra-rater reliability was 0.96 (0.89, 0.99). Conclusions The SubCyclo probe maintains stable laser power outputs throughout repeated use for up to 16 cycles, with a significant increase observed after 16 cycles.

A Composite Super-Twisting Sliding Mode Approach for Platform Motion Suppression and Power Regulation of Floating Offshore Wind Turbine

The floating platform motion of an offshore wind turbine system can exacerbate output power fluctuations and increase fatigue loads. This paper proposes a new scheme based on a fast second-order sliding mode (SOSM) control and an adaptive super-twisting extended state observer to suppress the platform motion and power fluctuation. Firstly, an affine nonlinear model of the floating wind turbine pitch system is constructed. Then, a fast SOSM pitch control law is adopted to adjust the blade pitch angle, and a new adaptive super-twisting extended state observer is constructed to achieve total disturbance observation. Finally, simulations are conducted under two cases of wind and wave conditions based on FAST (fatigue, aerodynamics, structures, and turbulence) and MATLAB/Simulink. Compared with the traditional proportional integral (PI) control scheme and standard super-twisting control scheme, the platform roll under the proposed scheme is reduced by 13% and 4%, and pitch is reduced by 16% and 3% in Case 1. Correspondingly, the roll is reduced by 9% and 15%, and pitch is reduced by 7% and 1% in Case 2. For the tower top pitch and yaw moment, load reductions of 7% and 3% or more are achievable compared with those under the PI control scheme. It is indicated that the proposed scheme is more effective in suppressing floating platform motion, stabilizing output power of the wind turbine system, and reducing tower loads.

Design and analysis of a coupling coil structure for high‐efficiency wireless charging system for consumer electronics

SummaryThis paper introduces a novel type of coupling coil structure that can be used for wireless charging of consumer electronics. The coupling loop configuration includes an eight‐shaped transceiver coil and dual rectangular coils integrated on the printed circuit board (PCB). Moreover, when numerous transmitting coils of this structure are staged in parallel, it can sustain a consistent mutual inductance even when the receiver coil is not aligned, which can efficiently stabilize output power during charging. The article first models three different coil structures based on circuit theory and simulates their electromagnetic fields in commercial software and then performs a comparison among the three types of coils. Finally, it verifies the anti‐offset capability of the modified structure through a 25 W wireless power transmission experimental platform. The experimental outcomes are in accordance with the simulation and theoretical analysis, and compared with traditional dual‐transmitting coil structures, better overall power transmission efficiency has been achieved.

Using a fuzzy logic controller in photovoltaic power systems for maximizing PV array efficiency

The goal of this work is to design a high-efficiency photovoltaic system (PV) with a fuzzy logic controller. This PV system consists of a PV panel, DC/DC Buck-Boost converter with a 24V DC load, and a fuzzy logic controller. Because the efficiency of normal solar PV modules is very low, we implemented the fuzzy logic controller. In this paper, we have proposed a system that is designed and simulated in MATLAB Simulink. In the fourth section of the paper are shown obtained results which show that using the fuzzy logic controller for photovoltaic systems has better performance. This controller can facilitate the PV array to reach the MPPT faster and provide more stable output power.

Achieving Stable Output Power and Efficiency of a Class E Power Amplifier while Changing the Self-Inductance of the Frequency Filter and the Load Resistance

Achieving Stable Output Power and Efficiency of a Class E Power Amplifier while Changing the Self-Inductance of the Frequency Filter and the Load Resistance

Research on energy management and control for six-wheel-drive electric bus rapid transit with photovoltaic-battery-supercapacitor

Electric Bus Rapid Transit is an effective solution to traffic congestion and environmental pollution. At present, Electric Bus Rapid Transit needs to be equipped with a large number of power batteries, which brings the key problems of long charging time, short driving range, and high comprehensive utilization cost. To solve the above problems, a novel six in-wheel motors driving Electric Bus Rapid Transit scheme with photovoltaic cells, lithium-ion batteries and supercapacitors (SWEBRT-PBS) is studied, constrained by the cost and comprehensive energy efficiency of vehicle. First, the system architecture for hybrid energy storage system composed of photovoltaic cells, lithium-ion batteries and supercapacitors (PBS) is analyzed. The life cycle cost function for PBS based on the degradation cost of lithium-ion batteries and the electricity cost of each energy source is proposed. The dynamic programming algorithm is employed to optimize the life cycle cost function of PBS, and then to obtain the optimal size of matches for supercapacitors. Second, the fixed step disturbance observation method is adopted to ensure stable power output in the maximum power point tracking controller of photovoltaic cells based on the vehicle application environment. Third, the power control rules are extracted based on the optimization results of dynamic programming algorithm, and the power allocation strategy for PBS with dynamic programming algorithm joint rules is formulated. Fourth, the overall efficiency function for driving system is established and optimized based on the sequential quadratic programming algorithm. The collaborative optimization strategy for SWEBRT-PBS is developed based on the corresponding optimization results, PBS operating modes and vehicle operating modes. The results show that the SWEBRT-PBS can reduce the number of lithium-ion batteries, thereby reducing the vehicle mass by 1.27 % and increasing the vehicle space utilization by 1.81 %. In addition, the comprehensive energy efficiency of vehicle can be improved by 28.79 %.

A Novel Composite Pitch Control Scheme for Floating Offshore Wind Turbines with Actuator Fault Consideration

It is of great importance to simultaneously stabilize output power and suppress platform motion and fatigue loads in floating offshore wind turbine control systems. In this paper, a novel composite blade pitch control scheme considering actuator fault is proposed based on an augmented linear quadratic regulator (LQR), a fuzzy proportional integral (PI) and an adaptive second-order sliding-mode observer. Collective pitch control was achieved via the fuzzy PI, while individual pitch control was based on the augmented LQR. In the case of actuator fault, an adaptive second-order sliding-mode observer was constructed to effectively eliminate the need for the upper bound of unknown fault derivatives and suppress the chattering effect. This paper conducted co-simulations based on FAST (Fatigue, Aerodynamics, Structures, and Turbulence) and MATLAB/Simulink to verify the effectiveness and superiority of the proposed scheme under different environmental conditions. It is shown that platform roll was reduced by approximately 54% compared to that under PI control. For the tower fore–aft moment, load reductions of 45% or more were achievable. The proposed scheme can greatly reduce the pitch and roll of the floating platform and loads in the windward direction of the wind turbine.

Design of hydraulic power take-off systems unit parameters for multi-point absorbers wave energy converter

Ocean waves represent a substantial renewable energy source, prompting this study's exploration of harnessing this potential via multi-point floating absorbers equipped with hydraulic Power Take-Off (PTO) systems. The study's primary motivation is to comprehensively model a Wave Energy Converter (WEC), including the hydraulic PTO system's control mechanism and protection system. To optimize the WEC design, we first investigate the hydrodynamic parameters of the floating absorber, employing potential flow theories and assessing the effects of varying the diameter-to-draft ratio. Our research involves analyzing Response Amplitude Operators (RAOs) and hydrodynamic forces for different ratios to identify the most effective design, followed by using computed wave forces as inputs for PTO simulations in MATLAB/SimScape to determine the unit parameters. The analysis of RAOs and wave-exciting forces reveals that diameter-to-draft ratios between 0.67 and 1.0 yield the best WEC performance, offering promising recommendations. In the final step, we compare the performance of single and multi-point absorber system simulations, assessing factors such as pressure drop, flow rate, and power output at the hydraulic motor. This comparison concludes that multi-point absorbers generate a more stable power output than their single-absorber counterparts.