Average Output Research Articles

High-power and narrow-linewidth nanosecond pulsed intracavity crystalline Raman laser operating at 1.7 µm

We report on a high-power and narrow-linewidth nanosecond pulsed intracavity crystalline Raman laser at 1.7 µm. Driven by an acousto-optically Q-switched 1314 nm two-crystal Nd:YLF laser, the highly efficient cascaded YVO4 Raman laser at 1715nm was obtained within the well-designed L-shaped resonator. Thanks to the absence of spatial hole burning in the stimulated Raman scattering process, significant spectral purification of second-Stokes radiation was observed by incorporating a fused silica etalon in the high-Q fundamental cavity. Under the repetition rate of 4 kHz, the highest average output power for single longitudinal mode operation was up to 2.2 W with the aid of precision vibration isolation and precision temperature controlling, corresponding to the pulse duration of ∼2.8 ns and the spectral linewidth of ∼330 MHz. Further increasing the launched pump power, the second-Stokes laser tended toward be always multimode, and the maximum average output power amounted to 4.8 W with the peak power of ∼0.8 MW and the spectral linewidth of ∼0.08 nm. The second-Stokes emission was near diffraction limited with M2 < 1.4 across the whole pump power range.

A compact-size and high-power energy harvester using stacked flexible-PCB coils for rotational shaft applications

In this Letter, a compact-size and high-power energy harvester (EH) based on multilayer flexible printed circuit board (F-PCB) sheets is presented for wireless sensor system (WSS) applications on propulsion shafts. A 2 mm thin rotor is designed using two F-PCB sheets that integrate 12 coil bundles with a total number of coil turns of 368. A stator is designed in a fixture that can be installed in the bearing housing. Voltage and power of the fabricated EH were measured and analyzed at a rotational speed of 10–100 rpm. At 80–100 rpm, the average voltage and output increased linearly with increasing speed. In particular, at 100 rpm, the average voltage and power were 5.43 V and 1714 mW, respectively. This performance represents a significant improvement compared to previously published EHs. The proposed EH features the straightforward structure, facilitating easier power design and prediction, and it is adaptable to various rotational shaft applications.

A 8.83 ppm/°C temperature coefficient, 75 dB PSRR subthreshold CMOS voltage reference with piecewise curvature compensation

A subthreshold CMOS voltage reference (CVR) with low temperature coefficient (TC) over a wide temperature range and low power is proposed in this paper. The proposed CVR utilizes the ΔVGS of different-threshold and same-threshold nMOS pairs to generate complementary-to-absolute-temperature (CTAT) and proportional-to-absolute-temperature (PTAT) voltages, respectively. To compensate for the low-temperature and high-temperature segments of the temperature characteristic curve, the nonlinear compensation currents generated by the exponential-like relationship between the drain current and the gate-source voltage of two MOSFETs work in the subthreshold region is used. Based on a 0.18-μm CMOS process, post-layout simulation results show that the proposed CVR achieves an average output voltage of 263 mV. The power supply ripple rejection (PSRR) is −75 dB at 10 Hz and the line sensitivity (LS) is 0.0069 %/V when the supply voltage varies from 0.8 V to 2.5 V. The average TC is 8.83 ppm/°C for a wide temperature range of −40 °C–120 °C, and the minimum TC is only 3.65 ppm/°C.

Experimental Validation of Power Output and Efficiency for an Oscillating Water Column (OWC)

With the global energy demand escalating and concerns over the environmental impact of fossil fuels, there's a pressing need for cleaner, sustainable alternatives. This study highlights the potential contribution of wave energy to the power needs of coastal structures in the context of renewable energy. The research evaluates the power output and efficiency for an Oscillating Water Column (OWC) system that can be integrated into coastal structures to meet part of their power needs. Findings from both theoretical calculations and a 1:10 scale model experiment are presented. The mechanical power output and efficiency of the system for a full-scale prototype were calculated for deep water conditions with a wave height of 3m. The water surface oscillation inside the chamber is assumed to reflect the oscillation occurring outside the chamber. The maximum average mechanical power output for the full-scale prototype, corresponding to a wavelength of 22.5 m, was determined to be 64.8 kW, achieving a mechanical efficiency of 64.4%. The overall efficiency of the system is calculated as 55% by assuming the generator efficiency to be 85%, resulting in an average power output of approximately 55 kW. A 1:10 scale model of the OWC system with a Wells turbine was constructed and tested in a tank for deep water conditions. Froude similarity and Keulegan-Carpenter similarity were used, ensuring a seamless transition from the model to the prototype. The OWC model was subjected to controlled heaving motion with a period of T=1.2 s. The power generated by the OWC model illuminated four integrated 3.4V LEDs on the Wells turbine, which were used to measure the power output produced. The power output of the model was measured to be a minimum of 0.12 W for a rotational speed of 107 rpm, which corresponds to a power output of 12 kW for the scaled-up prototype. This system has the potential for further enhancement by incorporating multiple OWCs into coastal structures exposed to wave action. Such development could facilitate meeting the power requirements of coastal structures, thereby contributing to the promotion of both renewable energy generation and a sustainable environment. Future research will focus on optimizing OWC chamber sizes for specific sites and refining the model to better capture water surface oscillation dynamics. l

Bidirectional Rotating Turbine Hybrid Triboelectric‐Electromagnetic Wave Energy Harvester for Marine Environment Monitoring

AbstractHydrokinetic energy, a vital renewable resource, holds promise for addressing fossil fuel shortages to ensure a sustainable future. This study proposes an efficient and stable ocean wave energy harvesting system that combines a triboelectric nanogenerator (TENG), an electromagnetic generator (EMG) with a planetary gear system, and a driving turbine. The turbine transforms the up‐and‐down motion in water into continuous, unidirectional rotational motion. An EMG device accelerated by a planetary gear system further ensures sustained output at very low frequencies (0.25 Hz) and boosts the upper limit of power generation at medium to high frequencies. Under water wave conditions with a 1 Hz frequency, the TENG component yields an output of up to 2200 V and 122 µA, while the average EMG output is 15 V and 80 mA. Remarkably, the entire system maintains a steady and uninterrupted output even at extremely low frequencies (0.25 Hz). The peak power outputs for the TENG and EMG components are 115 and 350 mW, respectively, with power densities of 32.55 and 329.78 W m−3, surpassing prior achievements. This research demonstrates self‐powered applications and provides an efficient method to amplify water wave forces, enhancing energy harvesting capabilities for practical marine environmental monitoring.

Research on Heliostat Field Optimization Based on Monte Carlo Theorem and Randomized Algorithms

The text discusses a mathematical model established for calculating the optical efficiency of heliostat fields in solar power systems. It's grounded in geometric optics algorithms and considers factors affecting the field's optical efficiency. Each heliostat and the ground have independent coordinate systems for assessing whether light is blocked. The Monte Carlo method is utilized to determine the proportion of blocked light in reflected rays. This approach accommodates the conical nature of solar radiation, enhancing accuracy by transitioning from parallel to conical light representation. The results indicate an annual average optical efficiency of 0.5084 for the heliostat field, an annual average thermal power output of 30.879 MW, and 0.4915 kW/m2 as the annual average thermal power output per unit mirror area.

Performance analysis of deep borehole heat exchangers for decarbonization of heating systems

AbstractMeeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector. Heat pumps with deep borehole exchangers are a promising solution to reduce emissions. Here the thermal behavior of deep borehole exchangers (DBHEs) ranging from 1 to 2 km was analyzed for various heat flow profiles. A strong correlation between thermal energy extraction and power output from DBHEs was found, also influenced by the heating profile employed. Longer operating time over the year typically resulted in higher energy production, while shorter one yielded higher average thermal power output, highlighting the importance of the choice of heating strategy and system design for optimal performance of DBHEs. Short breaks in operation for regenerating the borehole, for example, with waste heat, proved to be favorable for the performance yielding an overall heat output close to the same as with continuous extraction of heat. The results demonstrate the usefulness of deep boreholes for dense urban areas with less available space. As the heat production from a single DBHE in Finnish conditions ranges from half up to even a few GWh a year, the technology is best suitable for larger heat loads.

Research on Multi-Objective Optimization of Heliostat Field Based on DELSOL3 Layout

With the intensification of global climate change, it is urgent to reduce greenhouse gas emissions and protect the environment. To address this issue, it is crucial to develop the new energy industry and increase the proportion of clean energy. Tower solar power, as an innovative and environmentally friendly technology with low carbon emissions, has great potential and broad prospects. This study determines the position of the absorption tower, heliostat size, and installation height. By utilizing the ground coordinates of the heliostats and given formulas, parameters such as average optical efficiency, cosine efficiency, shadow blocking efficiency, and cut-off efficiency are calculated. The focus is on power loss caused by shading, so a shadow blocking model is constructed by using differential methods. The heliostat plane is divided into equal sections, and it is determined whether the transformed coordinates of the mirror plane are within the grid. The effective blocked area is then calculated to obtain the shadow blocking efficiency. To improve the efficiency and reduce costs of solar thermal power plants, the standard radial staggered layout in DELSOL3 empirical layout is adopted. A multi-objective optimization model is established with heliostat size and height as variables. The optimal solution for the average output thermal power per unit mirror area is obtained through genetic algorithms. Through mathematical modeling and solution methods, this study provides theoretical basis for the application of tower solar power.

2D Materials‐Based Pulsed Solid‐State Laser: Status and Prospect

AbstractPulsed solid‐state lasers comprise 2D materials as saturable absorbers that contain transparent windows of the atmosphere and characteristic fingerprint spectra of several vital molecules that are significant in various applications and research. Over the past few decades, significant progress has been made in the development of narrow pulse width, high energy, high average output power, high efficiency, and simple construction of passively Q‐switched and mode‐locked lasers with 2D materials as saturable absorbers. This review summarizes the development of 2D materials, including graphene, transition metal dichalcogenides, black phosphorus, topological insulators, and MXenes, as modulator devices for solid‐state lasers owing to their broadband operation, excellent nonlinear optical response, low recovery time, ultrafast dynamic processing, and easy fabrication. Then, some new emerging and representative applications of pulsed solid‐state lasers are introduced and illustrated such as laser surgery, material processing, and lidar. Finally, future challenges and perspectives of pulsed solid‐state lasers with 2D materials‐based saturable absorbers are analyzed and addressed. The rapid development of pulsed solid‐state lasers with the continuous improvement of modulation technology is expected to expand opportunities for application in industry, scientific, medical, and other areas.

The Use of Markov Chain Model for Rating Location Based Turbine Performance

It is shown how a 12-state Markov chain model can be used in rating turbine performance in a given location. A 1.8 MW wind turbine exposed to wind speed in San Angelo, USA is used for illustration. The model fits the data. As such, features of the model are used in providing indices for rating the performance of the turbine in this location. Probability distribution of the wind speed in this location is introduced into each of the traditional methods of computing average power output from the turbine power curve and expected extract-able power. The estimates obtained are 937 kW and 826 kW, respectively.

Performance enhancement of porous clay cooler for BIPV applications using hollowed clay structures and metallic extended fins as evaporation and thermal conductivity enhancers

This paper investigates the employing of a passive evaporative cooling approach to mitigate the temperature rise of PV panels within building-integrated photovoltaic (BIPV) systems. The investigation explores enhancing the heat transfer capabilities of composite clay layers by incorporating thermal conductive materials such as iron-oxide and zinc-oxide. This enhancement aimed to improve the overall thermal properties of the composite clay structures, thereby boosting heat transfer rates. Additionally, two distinct designs were evaluated as well: one integrating hollowed clay layer and the other featuring a clay layer with extended fins to enhance both heat and mass transfer rates within the evaporative porous clay structure. A series of experiments conducted under real conditions using prototyped building rooms to simulate real BIPV systems to assess the cooling performance of the presented scenarios. The results revealed that the hollowed clay layer achieved the most substantial decrease in PV panel temperature, with a reduction of 16.5 % compared to the findings with a solid clay layer. In contrast, the composite Iron-oxide/clay layer demonstrated the smallest decrease in PV temperature at 11 %. Moreover, utilizing the hollowed clay structure led to a 6.3 % increase in average PV output power, as well as around 4.5 % enhancement in average photovoltaic’s efficiency compared to the outcomes observed with the solid clay layer. Moreover, incorporating the hollowed clay layer resulted in the most significant decrease in the building's annual load, achieving a reduction of 79.6 %. This signifies approximately a 2 % higher enhancement in cooling capabilities compared to utilizing solid clay layer. Further, the cost of electricity production decreased by 7.7 % (from 0.104 $/kWh to 0.096 $/kWh) following the incorporation of the hollowed clay layer, while the payback time was reduced by roughly 0.8 years compared to utilizing the solid clay layer and by 1.7 years in comparison to the non-cooled BIPV system.

First thin-disk oscillator with ceramic Yb:LuScO3 in comparison to the operation with ceramic Yb:Lu2O3

We report on the characterization and first laser operation of ceramic Yb:LuScO3 in a thin-disk oscillator. The optical performance achieved with a ceramic Yb:LuScO3 disk is compared to the one obtained with an existing ceramic Yb:Lu2O3 disk for reference. The characterization covers the measurement of the fluorescence spectra, the fluorescence lifetimes, and nomarsky imaging. The investigation on the laser operation covers the measurement of resonator losses, output powers, and thermal behavior during continuous-wave operation in a multimode thin-disk oscillator. An average output power of 149 W and a slope efficiency of 51.8% were achieved with the ceramic Yb:LuScO3 disk which reached a maximum surface temperature of about 150 °C. At the same temperature level, a disk made of the already established ceramic Yb:Lu2O3 delivered 957 W of output power with a slope efficiency of 75.7%.

Study and Analysis of RBFN based MPPT controller for wind energy integrated with Traction Power Supply System

The need of energy for railway is rising due to the increased speed at which trains must operate to maintain safety and dependability. This situation implies more electricity consumption and more challenges to railway operation stability. Therefore, this research suggests configuring wind energy integration with the current railway traction substations built on the current traction substation. The suggested setup consists of a converter that converts DC to DC with RBFN-based MPPT regulator wind energy source linked to a permanent magnet synchronous generator (PMSG), a rectifier, and a conventional traction system. The proposed system is modelled and analyzed by utilizing a radial basis function network (RBFN) in this study. Three traction substations: Aysha, Adegla and Dewanle:-are the subject of the case study, which integrates wind energy with the railway electric power system working at 25 kV AC. For the Aysha wind farm, a MATLAB/Simulink simulation is run in order to confirm the suggested technology. The setup with or without MPPT was used in order to evaluate the results. The proposed system produces an average output of 260.3kW without MPPT and 289.3kW with MPPT controller at wind speed of 20m/sec. The simulation findings suggest that the RBFN-based control method performs better under diverse wind conditions and is more suited for wind energy integration with traction system.

A Broadband Three-Way Series Doherty Power Amplifier with Deep Power Back-Off Efficiency Enhancement for 5G Application

This article presents a new broadband three-way series Doherty power amplifier (DPA) topology, which enables a broadband output power back-off (OBO) efficiency enhancement of up to 10 dB or higher. The proposed DPA topology achieves Doherty load modulation and three-way power combining through a transformer, which requires only a low coupling factor, thus facilitating its implementation in double-sided PCBs or monolithic microwave integrated circuit (MMIC) processes. The design equations for the proposed DPA topology are proposed and analyzed in detail. A proof-of-concept PA at the 2.1–2.8 GHz band using commercial GaN transistors was designed and fabricated to validate the proposed concept. Within the operating frequency band, it achieves a saturated output power (Psat) of 44.5–46.5 dBm with a peak drain efficiency (DE) of 60–72%, and 43–52% DE at 10 dB OBO. Moreover, under a 20 MHz long-term evolution (LTE)-modulated signal, the PA demonstrates a 36.8–37.5 dBm average output power (Pavg) and 47–53% average drain efficiency (DEavg). Notably, the adjacent channel leakage ratio (ACLR) is as low as −35–−28.2 dBc without any digital predistortion (DPD).

Gain-Switched Er-Doped Fluoride Fiber Laser at ~3.75 μm

We demonstrate a pulsed Er-doped ZBLAN fiber laser operating at 3.75 μm based on the gain-switching scheme. A diffraction grating is introduced as a wavelength selection component to enable stable lasing in this long-wavelength region that deviates from the emission peak of 4F9/2→4I9/2 transition in Er3+. Different from the conventional gain-switching behavior where the pulse repetition frequency of the output laser is same as the that of the pump, the gain-switched laser demonstrated here shows a variable pulse repetition frequency, which accounts for 1/n (n = 4, 3, 2) of the pump pulse repetition frequency, in response to the 1950 nm pump power. The output pulse characteristics, including average output power, repetition frequency, pulse duration, and peak power, are investigated in detail. Over 200 mW average output power at 3.75 μm was obtained at 12 W of 1950 nm pump power. This work demonstrates that the Er-doped ZBLAN fiber laser, in combination with gain-switched scheme, is a feasible and promising approach to generate powerful pulsed emission > 3.7 μm.

Investigation of Torque and Reduction of Torque Ripples through Assisted-Poles in Low-Speed, High-Torque Density Spoke-Type PMSMs

In this article, rotor designs utilizing assisted-poles are investigated for a high-torque density spoke-type permanent magnet synchronous machine (PMSM) with fractional slot concentrated winding (FSCW) to explore the rich air-gap magnetic field harmonics and torque generation mechanism. Due to their higher average torque output, spoke-type PMSMs with FSCW are increasingly used in high-torque density applications. However, slot harmonics generate torque ripples that are difficult to eliminate in FSCW spoke-type PMSMs. Removing slot harmonics from the stator or winding results in a large drop in torque since their winding factors are identical to those of the main harmonic. Therefore, rotor designs having assisted-poles (symmetrical and asymmetrical) are investigated in this work to mitigate slot harmonics and minimize torque ripples. Firstly, the air-gap flux density is analyzed for the machines having assisted-poles, and a model of interaction between the stator and rotor-MMF harmonics is created and validated through Finite element analysis (FEA) to analyze the torque production mechanism. In addition, an analytical relationship between the assisted-poles’ dimensions and the generated torque harmonics is proposed. Furthermore, a generalized torque ripple reduction concept for the FSCW spoke-type PMSM having asymmetrically designed assisted-poles is presented. The proposed design and optimization method are validated through analytical calculations and FEA simulations, and a brief comparative analysis is presented for the analyzed machine prototypes. It has been established that the machine designed by applying the proposed asymmetrical assisted-poles can achieve a reduction in torque ripples while also significantly lowering cogging torque in comparison to the conventional spoke-type PMSMs and other spoke-type PMSMs with rotor having symmetrical assisted-poles.

Amplification-free GW-level, 150 W, 14 MHz, and 8 fs thin-disk laser based on compression in multipass cells.

We report an amplification-free thin-disk laser system delivering 0.9 GW peak power. The 120 fs pulses, at 14 MHz, centered around 1 µm, containing 12.8 µJ delivered by a thin-disk oscillator, were compressed by factor 15 down to 8.0 fs with 148 W average output power and overall 82% efficiency. Additionally, we showed that even a sub-two-cycle operation with 6.2 fs can be reached with this technology. The system will be a crucial part of the XUV frequency comb being developed and a unique high-repetition rate driver for attosecond pulse generation.

Continuous production machine for separating and shaping Taiping Houkui tea.

In response to the challenges of low automation and a lack of a continuous processing system for Taiping Houkui tea, this study proposed a design scheme for a continuous processing line and built a continuous processing prototype for testing by combining the production requirements of Taiping Houkui tea, the characteristics of withered leaves, and the existing relevant production equipment. First, the physical properties of Taiping Houkui tea were determined. A simulation was performed using the Hertz-Mindlin model, and the motion states of the tea leaves were obtained under different conditions to define the parameter design range of the experimental platform and verify its structural rationality. Then, the response surface methodology was used to optimize the working parameter ranges and obtain the best working parameters for the feeding and kneading mechanisms. Finally, a continuous production prototype was constructed for further production verification. The experimental results show that the success rate of continuous production on this platform was 70.68%, with an average output of approximately 0.4kg/h for Taiping Houkui dry tea on a single slide track, and the produced tea was similar to manually made tea. This demonstrates that the continuous production technique has high feasibility and provides a reference for continuous production of Taiping Houkui tea.

Miniaturized design of multi-octave PA using spoof surface plasmon polaritons

Surface Plasmon Polariton (SSPP), which exhibits subwavelength-scaled field confinement, can be realized at microwave frequencies by ultrathin corrugated metallic strips, providing significant potential for circuit and system miniaturization. A number of SSPP units were employed in this study to design input and output matching networks of a multi-octave RF power amplifier (PA) for the purpose of reducing the overall circuit size. The designed SSPP-based PAs were fabricated and demonstrated to have an output power between 39.1 dBm and 41.8 dBm, and a power added efficiency (PAE) ranging between 60.2 % and 69.8 % in the frequency range of 0.8 GHz to 3.1 GHz, with a size of 35.5 mm * 46.7 mm, which achieves a 47 % size reduction compared to the traditional transmission-line based PA. A highly efficient global optimization method, the Bayesian Optimization (BO), was utilized to further enhance performance. SSPP PA's average output power and PAE have been improved by approximately 0.3 dBm and 2.6 %, respectively. Its overall size remains at the same level. With the use of a 20 MHz 5GNR signal, digital pre-distortion (DPD) has been implemented, and the linearity of the PA has been improved.

Using stacked pot connection of wetland microbial fuel cells to charge the battery: Potential and effecting factor

In the practical application of wetland microbial fuel cells (WMFCs), suitable designs and stacked connection systems have consistently been employed to increase and harvest power generation. Our study compares different WMFCs designs and demonstrates that the cylinder pot design outperforms the small hanging pot design in terms of electrical energy production. Moreover, power generation from the cylinder pot can be further optimized through separator modification and stacked connections. The stacked WMFCs design exhibited no voltage reversal, with an average power output ranging from 0.03 ± 0.01 mW (single pot) to 0.11 ± 0.05 mW (stacked connection of 5 pots) over a 60-day operational period. Additionally, our study identifies distinct patterns in both anodic and cathodic physiochemical factors including electrical conductivity (EC), pH, and nitrate (NO3−), highlighting the significant influence of plant involvement on altering concentrations and levels in different electrode zones. The WMFCs bioelectricity production system, employing 15 pots stacked connections achieves an impressive maximum power density of 9.02 mW/m2. The system's practical application is evidenced by its ability to successfully power a DC-DC circuit and charge a 1.2 V AAA battery over a period of 30 h, achieving an average charging rate of 0.0.2 V per hour.