Maximum Output Power Research Articles

Rational strategy for power doubling of monolithic multijunction III-V photovoltaics by accommodating attachable scattering waveguides

While waveguide-based light concentrators offer significant advantages, their application has not been considered an interesting option for assisting multijunction or other two-terminal tandem solar cells. In this study, we present a simple yet effective approach to enhancing the output power of transfer-printed multijunction InGaP/GaAs solar cells. By utilizing a simply combinable waveguide concentrator featuring a coplanar waveguide with BaSO4 Mie scattering elements, we enable the simultaneous absorption of directly illuminated solar flux and indirectly waveguided flux. The deployment of cells is optimized for front-surface photon collection in monofacial cells. Through systematic comparisons across various waveguide parameters, supported by both experimental and theoretical quantifications, we demonstrate a remarkable improvement in the maximum output power of a 26%-efficient cell, achieving an enhancement of ~93% with the integration of the optimal scattering waveguide. Additionally, a series of supplementary tests are conducted to explore the effective waveguide size, validate enhancements in arrayed cell module performance, and assess the drawbacks associated with rear illumination. These findings provide a comprehensive understanding of our proposed approach towards advancing multi-junction photovoltaics.

Zn-MOF as a saturable absorber for thulium/holmium-doped fiber laser

Metal–organic framework (MOF) is a class of material that is highly porous and modular. Due to their unique properties, MOFs have found applications in gas storage, gas separation, sensing, and supercapacitors. [Zn2(H2L)2(1,2-Bis(4-pyridyl)ethene)4]n, zinc (Zn)-based MOF was used in this work to achieve mode-locked operation in a thulium/holmium-doped fiber laser due to its excellent optical absorption at a wavelength of 1925 nm. The saturable absorber (SA) was fabricated by drop-casting a mixture of Zn-MOF and isopropanol on an arc-shaped fiber. The center wavelength of the mode-locked laser is 1906.75 nm, with a maximum average output power of 3.251 mW. The fundamental repetition rate and the pulse width were 12.89 MHz and 1.772 ps. At the same time, the pulse energy and peak power were 252 pJ and 142 W, respectively. To the authors’ knowledge, this is the first time an MOF has been used for mode-locked pulse generation in a thulium/holmium-doped all-fiber laser. This work extends the use of MOF material as a saturable absorber for mode-locking applications in near-infrared fiber lasers.

Scalable MXene/Sepiolite film-based hydrovoltaic generators with outstanding output power

Harvesting energy from the ambient environment via hydrovoltaic effect is an emerging technology for environmentally friendly and sustainable power generation. However, its practical utilization has been hindered by the lack of scalable electrode materials with high output power. Here, novel MXene/Sepiolite composite films with scalable surface areas were designed and fabricated using highly concentrated MXene/Sepiolite ink via Meyer rod-coating, which showed promising performance used for transpiration-driven electrokinetic power generators (TEPGs). This was owing to the confined water and ion transfer in the composite films. The added Sepiolite could substantially adjust the layer spacing and hydrophilicity of the films, resulting in boosted performance. The MXene/Sepiolite composite films showed composition, size, and electrolyte-dependent power generator performance due to the controlled mass transfer in the films, producing TEPGs with tunable output power. An MXene/Sepiolite-based TEPG (MSTEPG) could generate a short-circuit current (ISC) of 163.82 μA in 1.75 wt% NaCl solution, demonstrating a maximum output power of 70.68 μW, which was larger than most reported TEPGs. This simple yet efficient roll-to-roll strategy provided a promising way for fabricating MXene-based electrodes on a large scale and represented a critical step toward the practical utilization of massive energy produced by the hydrovoltaic effect.

Healable Liquid-Free Osmotic Power Generator Using Nanofluidic Membranes of 2D Vanadium Pentoxide Nanosheets.

Here, we report an osmotic power generator (OPG) using a restacked membrane of vanadium pentoxide (V2O5) nanosheets and an ion-infused gelatin hydrogel. This gel osmotic power generator (GOPG) has several advantages over traditional liquid-based OPG in portability, power output, and spillage safety. Under a 1000-fold salinity gradient, the GOPG achieved an output power density of 0.13 W m-2. We have studied the effect of different ions, the concentration gradient, and the membrane thickness to achieve maximum power output. Notably, physical damage to the V2O5 membrane can be healed by adding a drop of water. Cracks or damage to the gelatin gel can be healed by reheating and cooling. The GOPGs can be easily connected in series and/or parallel to add up the voltage and/or current values generated by individual devices for practical powering applications. We have demonstrated lighting up an LED and powering a humidity meter using a series of combinations with the GOPG.

Hardware implementation of Firefly algorithm-based maximum power point tracking on Arduino

In this paper, we present the design and implementation of a Firefly Algorithm-based Maximum Power Point Tracking (MPPT) system on an Arduino platform, aimed at optimizing the performance of photovoltaic systems under variable environmental conditions, particularly partial shading. The Firefly Algorithm was chosen for its ability to efficiently locate the global maximum power point in the presence of multiple local maxima caused by non-uniform irradiance. The experimental setup utilized a Boost converter controlled by the Arduino, dynamically adjusting the duty cycle to maintain the PV system at its optimal operating point. Results demonstrated the system's effectiveness in responding to changes in solar irradiance, ensuring consistent maximum power output. Building on this, our research highlights the use of low-cost hardware like Arduino for implementing advanced MPPT algorithms, bridging the gap between theoretical research and practical applications. The study emphasizes that even with limited resources, significant gains in efficiency can be achieved in renewable energy systems. The findings suggest that using such a platform not only reduces costs but also enhances the accessibility of advanced MPPT technologies in real-world applications, making them a viable option for broader adoption.

COVID-19's Impact on Athletes: Reduced Cardiorespiratory fitness after a SARS-CoV-2 Infection.

This study aimed to identify potential changes in cardiorespiratory fitness among athletes who had previously been infected with SARS-CoV-2. In this prospective observational multicenter hybrid study (CoSmo-S), cardiopulmonary exercise testing on treadmills or bicycle ergometers involving 2314 athletes (39.6% female) was conducted. German federal squad members (59.6%) and non-squad athletes were included in the study. 1170 (37.2% female) subjects were tested positive for SARS-CoV-2 via PCR from which we had pre-SARS-CoV-2 infection examinations available for 289 subjects. Mixed effect models were employed to analyze amongst others the following dependent variables: Power output at individual anaerobic threshold (POIAT/kg), maximal power output (POmax/kg), measured V̇O2max/kg, heart rate at individual anaerobic threshold (HRIAT) and maximal heart rate (HRmax). A SARS-CoV-2 infection was associated with a decrease in POIAT/kg (-0.123 W/kg, p < 0.001), POmax/kg (-0.099 W/kg, p = 0.002), measured V̇O2max/kg (-1.70 ml/min/kg, p = 0.050) and an increase HRIAT (2.50 b/min, p = 0.008), HRmax (2.59 b/min, p < 0.001) within the first 60 days after SARS-CoV-2 infection. Using the pandemic onset in Germany as longitudinal reference point, the healthy control group showed no change over time in these variables respectively an increase in POmax (+0.126 W/kg, p = 0.039) during the first 60 days after the reference point. Subgroup analyses showed that both squad members and endurance athletes experienced greater decreases in cardiorespiratory fitness compared to non-squad members respectively athletes from explosive power sports. A SARS-CoV-2 infection is associated with a decline in cardiorespiratory fitness in athletes for approximately 60 days. Potential factors contributing to this outcome seem to be cardio-pulmonary and vascular alterations in consequence of SARS-CoV-2. A minor effect on cardiorespiratory fitness has training interruption due to acute symptoms and/or quarantine.

Compact widely tunable laser integrated on an indium phosphide membrane platform

We present the design, fabrication, and characterization results of a compact, widely tunable laser realized on an indium phosphide membrane-on-silicon (IMOS) platform. The laser features a compact Mach–Zehnder interferometric structure as the wavelength-selective intracavity filter with a footprint of 0.13 mm2. The filter design is optimized to ensure narrow filter transmission and high side-mode-to-main-mode-ratio, enabling single-mode operation for the laser. The high optical confinement on the IMOS platform can support tight waveguide bends. Leveraging this, the laser achieves a short cavity length, further enhancing the single-mode operation. Measurement results indicate a threshold current of 29 mA and a maximum on-chip output power of approximately 3.6 dBm and wall plug efficiency of 1.8%. The side-mode suppression ratio ranges from 30 to 44 dB, with a tuning range spanning 40 nm, from 1555 to 1595 nm. A complete tuning lookup table is generated via an automated setup incorporating a stochastic search algorithm.

All-solid-state continuous-wave mode-locked Er:Lu2O3 laser at 3 µm

In this paper, we demonstrated stable continuous-wave passively mode-locked operation of an Er:Lu2O3 laser at 3 µm, utilizing a semiconductor saturable absorber mirror (SESAM). By operating the laser in a dry nitrogen environment and utilizing a thermoelectric cooler (TEC) temperature control device to mitigate the thermal effects of Er:Lu2O3 and enhance laser stability, we further compensated for group delay dispersion within the laser cavity through chirped mirrors, an shortest pulse duration of 12.0 ps at a average output power of 150 mW was achieved, which occurred at a center wavelength of 2844 nm, and a pulse repetition rate of 83.5 MHz. Additionally, we achieved a maximum continuous-wave mode-locked output power of 213 mW at an absorbed pump power of 8.3 W, equivalent to a pulse energy of 1.3 nJ. The RF spectrum analysis of the pulse train indicated a high SNR of nearly 70 dB, signifying excellent stability. To the best of our knowledge, This is the first report on the realization of an ultrashort pulse width mode-locked Er:Lu2O3 laser in the mid-infrared band.

Isolator-free 60 W diamond Raman laser at 607 nm.

We report an intra-cavity frequency doubled diamond Raman laser operating at 607 nm. A z-fold cavity design was configured to prevent back reflections into the fiber amplifier, which avoided the use of isolators in the pump beam path. A maximum output power of 60 W was generated in two output beams at an optical conversion efficiency of 28% from the 1045 nm pump. A maximum single-beam output power of 40 W was obtained using a highly reflecting end mirror for the visible. Output power and single frequency stability are negatively impacted by an increasing role of stimulated Brillouin scattering at output powers above 10 W.

Self-powered piezoelectric sensing system for rotational speed detection of AUV propellers

To realize high-precision self-supplied speed measurement of Autonomous Underwater Vehicle (AUV) propellers, a self-powered piezoelectric speed sensing and detecting system is developed, which consists of a self-powered piezoelectric detection module and energy management and sensing circuits. The system uses three piezoelectric cantilevers for power and sensing detection. The proposed speed detection system is based on the piezoelectric effect and realizes self-powered sensing by utilizing the kinetic energy generated during the rotation of the propeller into electrical energy. The comprehensive model of the proposed piezoelectric sensing system under periodic toggled excitation is established and analyzed. The optimal output power of the system is investigated through theoretical analysis and simulation. The experimental system of the self-powered speed sensing system is constructed and the effect of speed measurement is tested. Experimental results show that the maximum output power of the piezoelectric self-powered sensing system developed in this work is 218 μW, which is much higher than that of the purely triboelectric sensing system. And the average detection error of the self-powered sensing system is 1.4% and the linearity is 1.09% when the propeller speed ranges from 0 to 300 r/min. Compared with similar self-powered systems, the proposed piezoelectric self-powered system is more advantageous in terms of measurement accuracy and can provide more accurate propeller speed measurement.

The Effects of Diabetes on Gas Transfer Capacity, Lung Volumes, Muscle Strength, and Cardio-pulmonary Responses During Exercise.

Diabetes is a risk factor for the development of vascular disease, chronic kidney disease, retinopathy, and neuropathy. Diabetes is a co-morbid condition commonly present in patients with respiratory disorders but the extent to which it influences ventilatory capacity, gas exchange, and functional capacity is not well known. Research question Does the presence of diabetes contribute to impairment in spirometry, gas transfer, and exercise capacity? Retrospective analysis of all subjects who performed incremental cardio-pulmonary exercise testing (CPET) between 1988 and 2012 at McMaster University Medical Centre. The impact of diabetes on physiological outcomes and maximum power output (MPO) was assessed using stepwise multiple additive linear regression models including age, height, weight, sex, muscle strength, and previous myocardial infarct as co-variates, and was also stratified based on BMI categories. 40,776 subjects were included in the analysis; 1938 (5%, 66% male) had diabetes. Diabetics were older (59 vs. 53 years), heavier (88.3 vs.78.0 kg), and had a higher BMI (31 vs. 27kg/m2). The presence of diabetes was independently associated with a reduction in FEV1 (-130ml), FVC (-220ml), DLCO (-1.52ml/min/mmHg), and VA (-340ml) but not KCO. Patients with diabetes achieved a lower % predicted MPO[diabetic subjects 70% predicted (670 kpm/min ± 95% CI 284) vs. 80% in non-diabetics (786 kpm/min ± 342), p < 0.001]. With the exception of KCO, these differences persisted across BMI categories and after adjusting for MI. The presence of diabetes is independently associated with weaker muscles, lower ventilatory and gas transfer capacity and translates to a lower exercise capacity. These differences are independent of age, height, weight, sex, and previous MI.

Output characteristics of an actively Q-switched Tm:GdScO3 slab laser at 2 μm band

An acousto-optic Q-switched Tm:GdScO3 slab laser at different pulse repetition frequencies was successfully demonstrated for the first time. The size of a slab crystal doped with a 2 at% Tm3+ is 2 mm × 4 mm × 20 mm. With the pump power of 33 W, a maximum average output power of 3.03 W was obtained with center wavelength of 1980 nm at pulse repetition frequency of 20 kHz. The optical-to-optical conversion efficiency and slope efficiency were 9.18% and 16.66%, respectively. The maximum pulse energy was 0.60 mJ with pulse width of 160 ns at 1 kHz, corresponding to the peak power of 3.75 kW. In addition, at the pump power of 33 W, the beam quality factors M 2 for horizontal and vertical directions were 1.33 and 1.08, respectively.

Strategic optimization of PV integrated fuel cell systems for energy surplus utilization in grid failure scenarios

Effective energy management in grid-connected renewable energy systems is essential for achieving cost-efficiency and reliability. This work presents a versatile control technique to tackle power system difficulties in grid-connected and grid-failure modes. The concept employs a digital iterative approach to optimize the operation of a DC-DC converter, guaranteeing the attainment of maximum power output and stability. During a grid breakdown, the system injects carefully adjusted active power into the grid to ensure that voltage and current levels are maintained at appropriate levels, hence preventing overloading. The proposed strategy exhibits a 99% enhancement in system responsiveness and a 96% decrease in overshoot when compared to conventional methods, thus substantiating its efficacy in practical scenarios.

An enhanced electromagnetic energy harvester based on dual ratchet structure with secondary energy recovery

Abstract With the continuous advancement of ultra-low-power electronic devices, capturing energy from the surrounding environment to power these smart devices has emerged as a new direction. However, most of the mechanical energy available for harvesting in the environment exhibits ultra-low frequencies. Therefore, the feasibility of self-powering low-power devices largely depends on the effective utilization of this ultra-low-frequency mechanical energy. Consequently, this work proposes an enhanced electromagnetic energy harvester based on a dual ratchet structure with secondary energy recovery. It converts ultra-low frequency vibrations into fast rotational movements by means of a rack and pinion mechanism, thus achieving high power output while maintaining a simple structure. Experimental tests demonstrate that the proposed harvester exhibits excellent power output under ultra-low-frequency external excitation. Under external excitation with a frequency of 1.5 Hz and an amplitude of 22 mm, with the optimal load matched at 20 Ω, the maximum power output reaches 598 mW, with a power density of 1572.65 μW/cm³. The secondary energy recovery power accounts for 34.4 %, resulting in a 52.56 % enhancement in the energy harvester's output performance. Additionally, hand-cranking tests indicate that the fabricated prototype of the electromagnetic energy harvester can power some common electronic devices, including smartphones, showcasing significant application potential.

Thermoelectric generator efficiency: An experimental and computational approach to analysing thermoelectric generator performance

TEGs are devices that convert heat directly into electricity through the Seebeck effect, offering a promising solution for waste heat recovery in various industries. In this research, COMSOL Multiphysics 6.0 was used to conduct a comprehensive 3-dimensional computational study of TEGs. Integrating thermal and electrical models in COMSOL facilitates a detailed understanding of the thermoelectric phenomenon. Applying six distinct temperature gradients, temperature and electrical distribution, power output, and efficiency of the TEG was thoroughly analysed. Experimental validation confirms strong agreement between simulation and experimental data, emphasizing accuracy. The average efficiency for the TEG at 1 Ω load is 3.12 %, increasing to 3.62 % for a 2 Ω load. The relative error between the computational model and the experimental model was 5 % for open circuit, 12.56 % for closed circuit at 1 Ω, and 12.14 % for closed circuit at 2 Ω, affirming the accuracy of the computational approach. Therefore, the computational model is validated by experimental results.Moreover, the findings highlight the relationship between external load resistance and power output, revealing that the maximum output power was achieved when the external load resistance matched the internal load resistance at 2 Ω. This work also significantly contributes to advancing the computational modelling of TEGs, validated through rigorous experimental analysis.

Childhood Physical Fitness as a Predictor of Cognition and Mental Health in Adolescence: The PANIC Study.

Cognitive and mental health problems are highly prevalent in adolescence. While higher levels of physical fitness may mitigate these problems, there is a lack of long-term follow-up studies on the associations of physical fitness from childhood with cognition and mental health in adolescence. We investigated the associations of physical fitness from childhood to adolescence over an 8-year follow-up with cognition and mental health in adolescence. The participants were 241 adolescents (112 girls), who were 6-9years at baseline and 15-17years at 8-year follow-up. Average and change scores for cardiorespiratory fitness (maximal power output [Wmax]; peak oxygen uptake [VO2peak]), motor fitness (10 × 5-m shuttle run), and muscular fitness (standing long jump; hand grip strength) were calculated. Global cognition score was computed from six individual cognitive tasks, and perceived stress and depressive symptoms were assessed at the 8-year follow-up. The data were analysed using linear regression models adjusted for age, sex, and parental education. Average motor fitness was positively associated with global cognition score (standardised regression coefficient [β] - 0.164, 95% confidence interval [CI] - 0.318 to - 0.010) and inversely with perceived stress (β = 0.182, 95% CI 0.032-0.333) and depressive symptoms (β = 0.181, 95% CI 0.028-0.333). Average cardiorespiratory fitness was inversely associated with perceived stress (Wmax: β = - 0.166, 95% CI - 0.296 to - 0.036; VO2peak: β = - 0.149, 95% CI - 0.295 to - 0.002) and depressive symptoms (Wmax: β = - 0.276, 95% CI - 0.405 to - 0.147; VO2peak: β = - 0.247, 95% CI - 0.393 to - 0.102). A larger increase in cardiorespiratory fitness was associated with lower perceived stress (Wmax: β = - 0.158, 95%CI - 0.312 to - 0.003; VO2peak: β = - 0.220, 95%CI - 0.395 to - 0.044) and depressive symptoms (Wmax: β = - 0.216, 95% CI - 0.371 to - 0.061; VO2peak: β = - 0.257, 95%CI - 0.433 to - 0.080). Higher levels of motor fitness in childhood and adolescence were associated with better cognition in adolescence. Higher levels of and larger increases in cardiorespiratory fitness from childhood to adolescence were associated with better mental health in adolescence.

Enhancing PV receiver efficiency in laser wireless power transmission through square elliptic hyperboloid concentrator

AbstractLaser wireless energy transmission is a widely utilized method, yet its efficiency is constrained by a variety of factors. In order to improve the conversion efficiency of the receivers of the laser wireless power transmission (LWPT) system, the square elliptic hyperboloid (SEH) concentrating module designed for LWPT system receivers is developed. By analysing the I–V characteristic curves from the results of the experiments and employing non‐linear parameter regression, a corrected battery characteristic curve was derived within a specific laser irradiation range. On this basis, an optical–thermal–electric multi‐field coupling characteristic model was developed. The finite element method is used to simulate the multi‐field coupling characteristics and conversion efficiency of the receiving end under diverse working conditions (including different rotation angles and different divergence angles) of the concentrating photovoltaic module. Research shows: First, the larger the divergence half‐angle β of the laser beam, the more obvious the improvement of the effective optical efficiency of the system by the SEH concentrator. Second, the short‐circuit current and the maximum output power of the PV cell at the receiving end are significantly improved by the SEH concentrator, and the improvement effect is more obvious with the increase of the divergence angle and the rotation angle. Third, SEH concentrators did not significantly affect the fill factor of PV cells.

First Achievement of Yellow Laser Operation in Dy3+-Doped Borate Crystals.

Continuous-wave (CW) yellow lasers have been demonstrated successfully by using a GaN laser-diode (LD) pumping in borate crystals for the first time. The Dy3+:GdMgB5O10 (Dy:GMB) crystal with dimensions up to 33 × 19 × 15 mm3 is grown by the top-seeded solution growth method, and the polarized spectroscopic properties are investigated systematically at room temperature. The line strengths, Judd-Ofelt (J-O) intensity, spontaneous transition rates, fluorescence branching ratios, and radiative lifetimes are calculated in detail by the Judd-Ofelt theory. Under direct pumping of 452 nm LD, a compact continuous-wave yellow laser with a maximum output power of 628 mW and laser wavelength of 581 nm is generated based on a Y-cut Dy:GMB crystal. To our knowledge, it is not only the highest output power for yellow laser obtained in Dy3+-doped crystals but also the first yellow laser operation achieved by borate crystals under direct LD pumping. The results reveal that the Dy:GMB crystal is an optical material with important application prospects in yellow laser.

Study of ash deposition characteristics of photovoltaic arrays taking into account the effect of photovoltaic module spacing and its effect on output characteristics: Indoor experiment

The problem of ash deposition on the surface of photovoltaic (PV) arrays during actual operation seriously affects their power generation efficiency. Because traditional research does not consider the PV module spacing, it cannot reflect the actual PV array ash deposition problem. This study explored the influence of PV module spacing, combined with different tilt angles and inlet wind speeds, on the characteristics of ash deposition and power output of the PV array through indoor experiments. The study designed a set of experimental equipment for simulating the formation process of ash deposition on the surface of PV arrays and set up an experimental platform to measure the influence of ash deposition on the maximum output power (Pmax), open-circuit voltage (Uoc), and short-circuit current (Isc) of the PV modules. The findings indicate that as the tilt angle increases, the PV array experiences reduced ash deposition and increased output power. Conversely, higher inlet wind speeds lead to greater ash deposition and decreased output power. Moreover, widening the spacing between PV modules results in increased ash deposition and reduced output power. Notably, within the PV array, the front PV module accumulates more ash than the rear module, with larger particle sizes. These research findings have significant implications for optimizing PV array design and enhancing power generation efficiency.

Design and characterization of a wind-adaptable piezoelectric energy harvester utilizing a rigid-flexible compound blunt body

In response to the challenges posed by uncontrolled amplitude during galloping and narrow effective bandwidth during vortex-induced vibrations in current energy harvesters, a novel wind-adaptable piezoelectric energy harvester utilizing a rigid-flexible compound blunt body (W-APEH) is proposed. The rigid-flexible compound blunt body improves environmental adaptability and power generation capacity. During the transformation process of the rigid-flexible compound blunt body from a Y-shape to an r-shape, a vibration pattern changes from galloping to coupled vibration, then to vortex-induced vibration. The feasibility of the structure and principle of the W-APEH were proved through a series of simulations and experiments. The higher proportion of rigid wings within a blunt body increases the susceptibility to galloping. A larger windward angle will delay the occurrence of galloping in the W-APEH, shorten the time of coupled vibration, and reduce the output voltage. In the case of the flexible wing thickness remains below 0.3 mm, an increase in thickness leads to an extended galloping time, with vortex-induced vibrations occurring later. Specifically, the onset wind speed is only 3.5 m/s, and the working wind speed range is 5–21 m/s with appropriate structural dimensions. Furthermore, the W-APEH provides a maximum output power of 3.78 mW at an optimal load resistance of 250 kΩ.