Search

Hexavalent chromium [Cr(VI)] is a toxic metal that poses huge threat to environment and living bodies. Recently, microbial fuel cell (MFC) systems based on highly efficient cathodes have been widely applied for Cr(VI) remediation. In this study, a novel cathode loaded with magnetic nanoparticles (NPs)-doped biochar (Fe NPs/biochar) is introduced into a two-chamber MFC to investigate its power output and Cr(VI) reduction. Results showed that the removal efficiency of Cr(VI) using Fe NPs/biochar group was 98.19%, which is significantly higher than that of carbon felt (53.31%). The maximum power density of the Fe NPs/biochar is 8.41 times higher than that of carbon felt. An adsorption–reduction mechanism is obtained for Cr(VI) reduction of Fe NPs/biochar through characteristic and electrochemical analyses, such as scanning electron microscopy-energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry test. The microbial community analysis showed that the biofilm of the anode were enriched with electrochemically active bacteria, such as Geobacter and Pseudomonas , after operation. Thus, this study presents a highly effective electrode for enhancing the power output and Cr(VI) reduction for Cr(VI)-containing wastewater treatment. • The system showed high removal efficiency (∼98.19 %) for Cr(VI). • Fe NPs/Biochar cathode produced 144 mV of the bioelectricity. • Fe NPs can improve the performance of MFC as an electron shuttle carrier. [ABSTRACT FROM AUTHOR]

This study aimed to verify if different stretch–shortening cycle (SSC) methods, obtained by the vertical jump test, present the same characteristics through consistency and agreement analysis, and to compare the SSC methods between athletes of different sports. Three hundred and forty-one male athletes of three sports groups (combat sports, team sports, and runners) participated in this study. Athletes performed the countermovement jump and squat jump tests to identify the SSC using three methods: reactive strength index (RSI), pre-stretch augmentation percentage (PSA), and eccentric utilization ratio (EUR). The results demonstrated very large correlations between the methods for jump height (r = 0.96–0.98) and power output (r = 0.95–0.98), almost perfect agreement for jump height (k = 0.86–0.91) and substantial to almost perfect agreement for power output (k = 0.77–0.92). The RSI, PSA, and EUR were higher in team sports than combat sports for jump height (P = 0.006, P = 0.008, P = 0.007, respectively), EUR was higher for team sports than combat sports for power output (P = 0.041). The methods of SSC are strongly correlated and present excellent agreement. Team sports athletes presented greater use of SSC compared to combat sports regardless of the method. [ABSTRACT FROM AUTHOR]

This study aimed to investigate predictors of cycling performance in U23 cyclists by comparing traditional approaches to a novel method – the compound score. Thirty male U23 cyclists (N = 30, age 20.1 ± 1.1 yrs, body mass 69.0 ± 6.9 kg, height 182.6 ± 6.2 cm, V ̇ O 2max 73.8 ± 2.5 mL·kg−1·min−1) participated in this study. Power output information was derived from laboratory and field-testing during pre-season and mean maximal power outputs (MMP) from racing season. Absolute and relative 5-min MMP, 5-min MMP after 2000 kJ (MMP 2000 kJ), allometric scaling and the compound score were compared to the race score and podium (top 3) performance during a competitive season. Positive and negative predictive values were calculated for all significant performance variables for the likelihood of a podium performance. The absolute 5-min MMP of the field test revealed the highest negative predictive capacity (82.4%, p = 0.012) for a podium performance. The compound score of the 5-min MMP 2000 kJ demonstrated the highest positive and average predictive capacity (83.3%, 78.0%, p = 0.007 - respectively). The multi-linear regression analysis revealed a significant predictive capacity between performance variables and the race score (R2 = 0.55, p = 0.015). Collectively the results of the present study reveal that the compound score, alongside absolute power, was able to predict the highest positive and average likelihood for a podium performance. These findings can help to better understand performance capacity from field data to predict future cycling success. [ABSTRACT FROM AUTHOR]

Rooftop solar arrays are a way of harvesting the energy from sun rays falling on the roof of buildings. These arrays can help buildings to generate power for themselves, either completely or partially fulfilling their energy needs. These systems however have their own sets of factors that can cause losses in them and reduce their power output. In this research work, the effect of mutual shading and design parameters are studied. The rooftop solar arrays with different parameters are simulated that help to estimate results closely agreeable with practical outcomes. The software 'DIVA for Rhino' was used to perform the simulations. The effect of various parameters such as the inclination of the roof surface, inter-row spacing of the panels, and their inclination, were studied. The degree of mutual shading was observed by varying these parameters. The power outputs and payback periods of the simulated systems were compared and their trends were observed to give a better understanding of how these factors affect rooftop solar arrays. The shading loss was high for higher panel inclination values coupled with smaller inter-row spacing. A higher roof inclination reduced the level of shading loss as it reduced the panel inclination with respect to the roof surface. The roof surface area increases with its inclination, which means more space for solar panels and hence a higher array power output. The results of the simulations will help in better decision-making during the construction of rooftop solar arrays as it helps to see the extent to which each of these parameters affects them. • Rooftop PV arrays were simulated. • This paper examines the effects of various design parameters on mutual shading. • The software 'DIVA for Rhino' was used to perform the simulations. • Annual power generation of the PV arrays was simulated. • Payback periods of the PV arrays were calculated. [ABSTRACT FROM AUTHOR]

The free-piston linear generator (FPLG) with a dual-piston air-driven system is a novel type of energy conversion device that converts mechanical energy into electric power through a linear generator. This paper investigates a novel FPLG utilising different generator stator core configurations (GA, GB, GC, GD, and GD) with an optimised valve opening control and the inlet pressure of 5 bar and 8 bar. The effect of generator configuration on the translator motion characteristics, root mean square (RMS) power output, as well as the system stability and the conversion efficiency, are duly discussed. The results show that the piston motion is affected by the generator configuration and the inlet pressure. The maximum RMS power achieved is 203.9 W when GB is used, whereas the maximum operating frequency of 13.8 Hz and a peak power output of 396 W are achieved when GD is used. The FPLG stability within the range for all generator configurations except for GA when the inlet pressure is 5 bar. The FPLG system conversion efficiency (thermal to work and work to electrical) is duly discussed. [ABSTRACT FROM AUTHOR]

In traditional wind farm planning, the design of wind turbine locations and cable layouts is usually undertaken sequentially. However, this approach may potentially result in suboptimal solutions. While the increased spacing between wind turbines enhances power output by reducing wake losses, it also imposes a negative impact by raising cable costs. Addressing this challenge, we propose a novel multi-objective optimization model that simultaneously considers the micrositing of wind turbines and cable routing. A joint framework of the Non-dominated Sorting Genetic Algorithm II (NSGA-II) and the Mixed-Integer Linear Programming (MILP) is established to optimize the layout of wind turbine locations, points of connection, and cable paths. The results indicate that, compared to the traditional sequential optimization, our integrated optimization exhibits significant economic advantages since improved the balance between micro siting and cable routing. By strategically sacrificing a portion of power generation to reduce cable costs, the overall investment profitability can be remarkably improved, with a maximum gain equivalent to 10.02 % of the cable costs. • Proposing a layout optimization model considering micro-siting and cable routing. • An integrated framework of the NSGA-II and the MILP is established. • The comparison between sequential and integrated designs for windfarm is studied. • Wake effects and cable crossing constraints are considered in the proposed model. [ABSTRACT FROM AUTHOR]

Efficient body heat harvesting with paper-based thermoelectric generator. [Display omitted] • Using paper as a flexible, lightweight, and biodegradable substrate for TEGs. • An easy, energy-efficient fabrication process suitable for large-scale production. • Maximum V oc and P max achieved were ∼42.60 mV and ∼10.65 nW at a Δ T of 30 °C. • Body attached PTG produces an output voltage of 11.95 mV and output power of 1.5 nW. • Effective low-grade heat harvesting from body, improving energy efficiency. The study presents the fabrication and characterization of paper-based thermoelectric generators (PTGs) using p -type Bi 0.5 Sb 1.5 Te 3 (BST) and n -type Bi 2 Te 2.7 Se 0.3 (BTS) thermoelectric (TE) materials, deposited via a novel cotton swab powder deposition technique. This method eliminates the need for complex equipment or high-temperature processes, reducing fabrication complexity and enabling large-scale production. The key advancements of this method are its simplicity, cost-effectiveness, and practical applicability, ensuring uniform coating and good material adherence to the paper substrate. The PTGs, consisting of five p - n pairs interconnected with various materials, were laminated for enhanced stability and humidity protection. Experimental measurements under temperature gradients(ΔT s) of 5–30 °C revealed an optimal configuration achieving an open-circuit voltage(V oc) of 42.60 mV, internal resistance(R int) of 42.50kΩ, short-circuit current(I sc) of 1.00µA, and maximum power output(P max) of 10.65nW for the carbon paste/copper sheet interconnected PTG at ΔT of 30 °C. The obtained normalized power density is 5.68nWcm-2K-1pair-1, which is one of the best among the reported Bi 2 Te 3 -based PTGs. A preliminary demonstration on an arm showed the PTG generating an 11.95 mV output voltage in hot weather conditions (ΔT ≈ 8 °C), effectively harnessing body heat for wearable electronics. This work highlights a simple, cost-effective, and scalable method for fabricating PTGs for sustainable energy harvesting in low-power wearable applications. Future efforts will focus on optimizing materials, fabrication techniques, and novel designs to enhance efficiency and scalability. [ABSTRACT FROM AUTHOR]

The nonlinear energy harvesting systems of the forced vibration with an electron-mechanical coupling are widely used to capture ambient vibration energy and convert mechanical energy into electrical energy. However, the nonlinear response mechanism of the friction induced vibration (FIV) energy harvesting system with multiple stability and stick-slip motion is still unclear. In the current paper, a novel nonlinear energy harvesting model with multiple stability of single-, double- and triple-well potential is proposed based on V-shaped structure spring and the belt conveying system. The dynamic equations for the energy harvesting system with multiple stability and self-excited friction are established by using Euler-Lagrangian equations. Secondly, the static characteristics of the nonlinear restoring force, the friction force, and the potential energy surfaces are obtained to show the nonlinear stiffness, multiple equilibrium points, discontinuous behaviors and multiple well responses. Then, the equilibrium surface of bifurcation sets for the autonomous system is given to show the third-order quasi zero stiffness (QZS3), fifth-order quasi zero stiffness (QZS5), double well (DW) and triple well (TW). The co-dimension bifurcation sets of the self-excited vibration system are analyzed and the corresponding phase portraits for the coexistent of multiple limit cycles are obtained. Furthermore, the analytical formula of amplitude frequency response of the approximated system are obtained by the complex harmonic method. The response amplitudes of charge, current, voltage and power of the forced electron-mechanical coupled vibration system for QZS3, QZS5, DW and TW are analyzed by using the numerically solution. Finally, a prototype of FIV energy harvesting system is manufactured and the experimental system is setup. The experimental works of static restoring forces, damping forcse and the electrical outputs are well agreeable with the numerical results, which testified the proposed FIV energy harvesting model. • A novel energy harvesting model with multiple stability is proposed. • The equations of motion for the energy harvesting system is established. • The freely oscillation and the forced vibration are investigated. • The prototype of the harvester is manufactured and the experiment is carried out. • The proposed mechanism can be extended to other engineering applications. [ABSTRACT FROM AUTHOR]

Increasing concerns over energy consumption and greenhouse gas emissions in buildings have contributed to the emerging of innovative PV glazing technologies to improve the building energy performance. However, some of these glazing systems have complex structures, making it challenging to investigate their optical, thermal and electrical performance for estimating their energy saving potential in buildings. In this research, a validated Computational Fluid Dynamics (CFD) combined with a ray-tracing model has been developed to accurately predict the optical, thermal and electrical performance of complex PV glazing systems under varying incident angles. A ray-tracing model is developed to calculate the light transmittance of the window and the solar energy absorbed by each solid element and PV cells. To estimate temperature profiles (e.g., PV temperature and window temperature) and secondary heat within the window, the results from the ray-tracing analysis, which detail the solar flux absorbed by each layer, are inputted into a validated CFD model as boundary conditions. Using the CFD combined ray-tracing calculation illustrated above, the Solar Heat Gain Coefficient (SHGC) of these complex PV window systems can be obtained. Furthermore, a PV modelling algorithm is developed to predict the power output based on the simulated PV temperature. This procedure is implemented to investigate a Crossed Compound Parabolic Concentrator Photovoltaic (CCPC-PV) window, which serves as an example of a complex PV glazing system in this study. The developed optical, thermal and electrical models have been validated through experimental tests. Additionally, new configurations have been designed to explore the impact of the pitch between adjacent optics on the SHGC and power output of the window. The results show that the original window (1.77 mm-pitch) possesses the maximum PV temperature of 64.73 °C and the maximum window inside surface temperature of 61.58 °C under National Fenestration Rating Council (NFRC) standard. Meanwhile the PV efficiency is 15.21 % and the SHGC is 0.463. The SHGC value of this innovative PV window is notably lower than that of a conventional double-glazed window, which has a SHGC value of 0.813. This reduction in SHGC decreases the likelihood of overheating issues, especially during the summer months. • Integrating CCPC PV into windows enhanced both energy efficiency and indoor comfort. • CFD combined ray-tracing method was proposed to estimate CCPC PV window performance. • Numerical simulation was validated using indoor testing through spectrometer and solar simulator. • New algorism for window power output was obtained using incident solar energy and modified PV efficiency. • In addition to power generation, approximately 43 % SHGC reduction was achieved compared with double glazing. [ABSTRACT FROM AUTHOR]

In the present study, wind tunnel experiments were performed to investigate the power and thrust characteristics of a wind turbine model subjected to a variety of surge and sway motions. The turbine model was mounted on a translational stage to simulate the surge and sway motions at prescribed amplitudes and frequencies. The power output and rotor thrust were measured in each sets of the motion frequencies and amplitudes, respectively; and the measurements were also performed in a base-fixed turbine for comparison. Results show that the surge and sway motions with various amplitudes and frequencies all have slight impact on the mean power output and mean rotor thrust of a wind turbine. However, the rotor thrust fluctuations of the surging turbine, not only appeared significantly higher than those of the swaying turbine and base-fixed turbine at the same sets of amplitudes and frequencies, but also increased with the surge frequency and surge amplitude. Moreover, for both the surging and swaying turbine, the rotor thrust fluctuated with the same period as the surge and sway motions, respectively; and the power spectral density of the rotor thrust both exhibited a peak at the motion frequency and its odd multiple frequencies. • Turbine power and thrust characteristics under surge and sway motions were studied. • Motions had slight effect on mean turbine power and thrust in various conditions. • Thrust fluctuations of surging turbine were higher than swaying and fixed turbine. • Surging turbine thrust fluctuations increased with surge frequency and amplitude. • The PSD of thrust for surging and swaying turbine peaked at motion frequency. [ABSTRACT FROM AUTHOR]

Understanding the effect of thermal stratification on wind turbine wakes in complex terrain is essential to optimize wind farm design. The effect of a three-dimensional hill on the performance of a downwind turbine is studied by performing large eddy simulations for different atmospheric conditions. The distance between the hill and the turbine is six times the turbine diameter, and the hill height is equal to the hub height. It is shown that the hill wake reduces the power production of the downstream turbine by 35 % for the convective boundary layer case under consideration. However, surprisingly, the wind turbine power production is increased by about 24 % for the stable boundary layer case considered here. This phenomenon results from the entrainment of kinetic energy from the low-level jet due to the increased mixing induced by the hill wake. This effect strongly depends on the Coriolis force-induced wind veer. The increased turbulence intensity by the hill results in a strong increase in the forces experienced by the blades, which suggest the turbine is experiencing much higher unsteady turbulence loading. It is shown that the increase in the power fluctuations may not fully reflect the increase in the force fluctuations on the blades. • Hill wake can improve the power production of the downstream turbine. • Power increase results from the Coriolis force induced wind veer and low-level jet. • The low-level jet energy is entrained due to the hill wake induced vortex shedding. • Hill wake strongly increases the power fluctuations of the downstream turbine. • Force fluctuations on blades are stronger than power fluctuations. [ABSTRACT FROM AUTHOR]

[Display omitted] Organic photovoltaic (OPV) cells have found their potential applications in the harvest of indoor light photons. However, the output power of such indoor devices is usually far from the demand of the internet of things. Therefore, it is essential to boost the output power of indoor organic photovoltaics to a much higher level. As wildly deployed among industrial and civil luminous environments, thermal radiation-based indoor light sources are alternative candidates to supply the essential power of the off-grid electronics with a broad consecutive emission spectrum. In this work, we evaluated the photovoltaic performance of organic solar cells under indoor incandescent and halogen illuminations. Impressively, under such thermal radiations, an improvement over 500% of the output power density can be achieved in comparison with that under light-emitting diodes and fluorescent lamps, reaching a record high value of 279.1 μW cm−2 by the PM6:Y6-based device. The remarkable power output is originated from the extra near-infrared spectrum of indoor thermal lights, which restricts the effective area under 10 cm2 in achieving 1 mW output power. This work clarifies the feasibility of collecting photons radiated from indoor thermal light sources through OPV cells, and enlightens the further applications of indoor OPV cells under multiple illumination environments. [ABSTRACT FROM AUTHOR]

• Parametric study and optimization of installation parameters for bi-facial solar PV system. • Optimization of bi-facial solar PV using response surface methodology. • New correlations for the energy yield and bifacial gain are presented. • The coefficients of determination R2 for the new developed correlations are 0.99. • The average daily bifacial gain is 35.68% at the optimum installation parameters. Sensitivity analysis of design parameters and power gain correlations of bi-facial solar PV system is presented in this paper. The main objectives are to study the effects of albedo, tilt angle and height from the ground on the performance of the system; determine the optimum operating conditions; and the development of new correlations for the annual energy yield and bifacial gain of bPV solar system. Three primarily significant installation parameters, albedo [10%, 50%, 90%], tilt angle [15°, 25°, 35°] and height [0.5 m, 1 m, 1.5 m] are investigated with PVSYST for bifacial and mono-facial PV modules. The response surface methodology (RSM) based optimization method is used to determine the optimum conditions and the interaction of these three parameters on the performance of bPV solar system. New quadratic equations or correlations are introduced to estimate the annual energy yield and bifacial gain of bPV. The results show that the albedo is the most significant parameter between tilt angle and height. The increase in albedo factor and height of bPV modules from ground increase the energy yield. In this study, the optimum tilt angle of bPV is found to be 35°for higher albedo and elevation of bPV from the ground as compared to 25° of mPV. An average daily bifacial gain of 35.68% can be achieved in clear sunny day with 90% albedo, tilt angle of 35° and at height of 1.5 m. The maximum specific productions of 192.4 kWh/kWp and 160.6 kWh/kWp are observed in May for bPV and mPV, respectively while the maximum bifacial gain of 21.93% is found in July. [ABSTRACT FROM AUTHOR]

A new hybrid system mainly composed of a dye-sensitized solar cell (DSSC), a solar selective absorber (SSA) and an absorption heat transformer (AHT) is theoretically put forward to harness the long wavelength sunlight transmitted through the DSSC. The models of both DSSC and AHT are adopted from the current literature and the condition enables the AHT to involve in heat upgrading is obtained. The model validations of DSSC and AHT are conducted using experimental data. Mathematical expressions of power output and efficiency for the hybrid system are formulated by taking a variety of irreversible losses into account. The effectiveness of the hybrid system is justified and evaluated. Maximum power density (MPD) and maximum energy efficiency (MEE) of the integrated system are, respectively, 158.2 W m−2 and 16.3 %, having evidently improvement compared to that of a single DSSC. A variety of operating conditions and design parameters affecting the hybrid system performance are studied. Numerical calculation results show that the working temperature, photoelectron absorption coefficient of DSSC and total heat-transfer area of the AHT have positive effects on the hybrid system performance. There exists an optimum TiO 2 thin film thickness to optimize the hybrid system performance. However, a greater Schottky barrier has negative influence on the hybrid system performance. The results obtained here may provide some guidance for designing such a practical hybrid system. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Fe@Mn-codoped biochar gas diffusion cathode was prepared. • A new type of electro-Fenton system was developed by sediment microbial fuel cell. • NSAIDs with different absorbability in both aqueous and solid phase can be removed. • Power output, sludge reduction and NSAIDs removal can be achieved simultaneously. Electro-Fenton (e-Fenton) reactions boosted using microbial fuel cells (MFCs) can degrade contaminants with high efficiency, the treatment is generally performed in the aqueous phase and the sludge pollution is ignored in such MFCs. In this study, a sediment MFC e-Fenton (SMFC-e-Fenton) system was proposed for the degradation of nonsteroidal anti-inflammatory drugs (NSAIDs) in both aqueous and solid phases. A Fe@Mn-codoped biochar gas diffusion cathode was fabricated to produce hydroxyl radicals without any additional power input. The studied NSAIDs of ibuprofen (IBU), naproxen (NPX), and diclofenac (DCF) exhibited total degradation efficiencies (including aqueous and sludge phase) of 99.1%, 98.5%, and 80.6%, respectively, in the SMFC-e-Fenton system. Compared with sludge anaerobic digestion, the residual amounts of IBU, NPX, and DCF reduced from 10.2%, 24.6%, and 32.2% to 2.7%, 4.4%, and 8.5%, respectively, in the sludge phase. Moreover, the electricity generation and sludge reduction improved owing to the e-Fenton process. Using the SMFC-e-Fenton system, the effects of NSAIDs were reduced and the richness and diversity of the microbial community are maintained, improving the overall system performance. These results demonstrate that the SMFC-e-Fenton method is a high-efficiency, economic and environmental friendly technology for simultaneously treating NSAIDs in the aqueous and sludge phases. [ABSTRACT FROM AUTHOR]

An assessment of potential for wind energy in Zambia was carried out to help address the shortage of energy due to increasing energy needs arising from energy requirements for newly opened mining industries and unreliable hydropower generation due to climate change. The assessment was carried out by collecting wind speed data of 25 sites owned by Zambia Meteorological Department. The objective of the study was to analyse wind patterns and determine areas in Zambia where production of electricity from wind can be invested. The analysis was based on the use of Weibull shape factor and yielded 3.32 m/s wind speed and 13.2 shape factor from a site with the most suitable wind speeds (Kasama Meteorological Station). A correlation study was carried out using these results and Goldwin 1.5 MW wind turbine of model GW82/1500. The study results showed that 44.46 kW power output could be obtained at 3.83 m/s wind speed by a correlation equation of this turbine power output with wind speeds. A series of similar power output results were obtained for wind speeds recorded in the years from 2013 to 2021 and compared with those obtained in the same period by using model equation due to Al Buhariri, and found that the power outputs compared very closely at low wind speeds ranging 3 to 3.2 m/s but rather widely at higher wind speeds. This study is significant in that it provides information on decision making and helps determine policy direction for wind utilization in Zambia and it can also help influence investment decision by Zambian mining companies who have financial ability to undertake large scale investments. [ABSTRACT FROM AUTHOR]

• The impact of air cavity on performance of PV-DSF was studied experimentally. • A photovoltaic triple skin facade system was investigated and compared with PV-DSF system. • The impact of perforation ratio was studied on performance of PV-TSF and light transmittance. A new skin of perforated metallic sheet is introduced in the cavity of a photo-voltaic double skin façade (PV-DSF) system for an efficient heat removal from the cavity without losing substantial light into the built space. Quantitative experimental analysis is conducted to evaluate its thermal and electrical performance for various combinations of ventilation modes, air cavities, and perforation ratios. The advantages of Photo-Voltaic Triple Skin Facade system (PV-TSF) over commonly used PV-DSF are also evaluated experimentally. The results showed that naturally ventilated PV-TSF provides lower temperatures and Solar Heat Gain Coefficient (SHGC) with slightly higher power when compared to no ventilation mode in PV-DSF system. The SHGC of the PV-DSF system can be reduced by nearly 4.7% with variation in air cavity (Thickness 50–200 mm); after which no noticeable improvement is observed. In the case of PV-TSF system, SHGC can be reduced by almost 14.7% compared to the PV-DSF system without significant loss of natural daylight into built space. Experimental results also showed that the reduction in perforation ratio from 60% to 20% reduced the SHGC by 3.8% with an average illuminance of 334 lux (minimum perforation, 20%). It was also observed that the addition of a perforated sheet can offset the large air cavity of a PV-DSF system. Therefore, the benefit of the PV-TSF system is profound as compared to PV-DSF. [ABSTRACT FROM AUTHOR]

• An intuitive methodology for assessment of shading losses in PV systems is proposed. • The methodology proposes tools for shadow prediction and power output estimation. • A study of different shadow pattern impact was performed. • The annual shading losses of a PV plant were evaluated. Frequently, PV systems are affected by dirt, dust or shadowing from surrounding elements, such as trees and buildings. The shadows can cause partial shading conditions, when the irradiance is not uniform on PV installation, which lead to losses of power. Thus, the shadow prediction is primordial for a better output power estimation and to minimize its losses. The aim of this article is to propose a methodology using intuitive and available tools for shading prediction and losses assessment on PV installations. A study about the shadow pattern and module orientation (portrait and landscape) influence and an analysis of the shading losses on a PV plant were performed in order to demonstrate the applicability of the methodology. The shading effect is drastic when the shading is parallel to the short edge, whereas the effect is lower when it is parallel to the long edge. On the other hand, the losses due to shading and the difference in the position of the modules (landscape or portrait) have a lower impact on the photovoltaic plant case. It was concluded that the methodology is feasible and applicable for shading impact evaluation, despite limitations for large systems due to the simulation time. [ABSTRACT FROM AUTHOR]

• High-velocity sand and dust test apparatus was constructed in our lab. • Sand and dust test was performed on PV modules provided by 53 manufactures. • Effect of sand and dust on functional property of bypass diode in parallel with solar cell was assessed. The performance of solar modules is of grave concern in dusty regions. According to the relevant standards of IEC 60068–2-68:1994, we constructed a high-velocity sand and dust test apparatus in our lab. The sand and dust tests were performed on 330 PV modules provided by 53 manufacturers in China, Japan, American, India, and other countries during 2015–2019. The unqualified ratio of PV modules performed is about 5.76% in recent 5 years. The sand and dust certification test promotes continuous performance improvement of PV modules. The effect of sand and dust on the performance of module and bypass diode in parallel with solar cell was assessed. [ABSTRACT FROM AUTHOR]

If made in porous foam, thermoelectric ceramics for power generation can enhance the power output by directly extracting thermal energy from heat sources. This paper discusses the time-dependent power output and elastic/plastic fracture of the porous thermoelectric generator (TEG) with a small oblique-through crack. Analytical solutions of temperature and thermal stress of the TEG are derived based on an effective model of porous foam. The finite element numerical model is created to validate the analytical solutions and to explore more thermomechanical properties and constitutive behaviors of the porous materials. Comparing to the traditional bulk TEG, porous TEG can greatly improve the power output however the thermal stress is enhanced therefore the strength is substantially reduced. The power output gradually increases to a peak value and then decreases with the length of the TEG. Based on the criterion of fracture mechanics, a simplified and useful expression of the critical heat flux for crack propagation is identified. The critical heat flux for crack growth is inversely proportional to the porosity and the crack length. A more rigid contact between the TEG and the elastic boundary results in a larger thermal stress and a smaller critical heat flux. The velocity of crack propagation is mostly determined by the porosity and the ratio of the initial crack length to the arbitrary crack length. Also observed is that the length of plastic zone at the crack tips increases with the increasing porosity. [ABSTRACT FROM AUTHOR]

Advanced solar thermal devices with a high performance/cost ratio is a major concern nowadays. In this paper, we investigate the energetic efficiency of a new concept based on a direct coupling of a solar water heater with a thermoelectric module, in order to exploit the maximum of the solar spectrum, produce heat and electricity at the same time and improve the normal solar collector efficiency. An unsteady-state mathematical model of the system is presented in details to describe the system behavior. Using state-of-the-art thermal transfer calculations, the differential equations of the global system were established and solved numerically. The system model is solved using MATLAB program, while the finite difference method is based. Our major finding shows that the new hybrid system significantly improves the storage process by controlling the flow rate according to the concentration ratio variation. This flow rate attains a capacity of 1200.453 L/day, for 0.92 × 1.9 × 0.05 m3 a collector tilted at 30° under 20 suns, and produces a significant additional electrical energy about 10.41 Watts, which is very promising for future thermal/electrical applications. • A novel solar thermal thermoelectric system is proposed and explored. • Theoretical model is presented, numerically simulated, and smart program is developed. • The effect of the cooling system on the thermoelectric performance is analyzed. • Evaluated performances of this system under real concentrated sunlight are presented. • The system produces heat, electricity and increase the quantity of hot water stored. [ABSTRACT FROM AUTHOR]

Large scale wind turbines have been extensively examined for decades, but a very few studies have been conducted on small-scale wind turbines especially for the applications where artificial wind speed is of the order of 15 m per second. This study provides systematic effort towards design and development of small scale wind turbine aimed to operate at high wind speeds. The drag-based wind turbine has an enormous potential for small-scale power generation in cement manufacturing plant. It uses bag filter to prevent environmental pollution so as to let out the clean high velocity exhaust air through the duct. The work reported here presents to utilize exhaust air for electrical power generation. Exhaust air flow has been analysed in Ansys Fluent Software. Ansys Computational Fluid Dynamics (CFD) technology was adopted to evaluate the performance of the wind turbine. The results of torque assessment of the wind turbine in its static as well as dynamic condition have been presented. Experimental setup consisting turbine, generator, battery and load has been tested and validated. • The authors aim to develop wind turbine to operate at high speeds. • It uses exhaust air for power generation. • The ANSYS software is used for analysis. • The experimental and simulation results have been validated. [ABSTRACT FROM AUTHOR]

Objectives: We investigated if cold water immersion (CWI) affects exercise performance during a prolonged intermittent sprint test (IST), designed to mimic activity patterns of team-sports.Design: Randomized-crossover design.Methods: Ten male team-sport players completed 3 IST protocols (two 40-min "halves" of repeated 2-min blocks consisting of a 8-s "all-out" sprint, 100-s active recovery and 12-s rest) on a cycle ergometer at normothermic conditions. Each "half" was separated by a 15 min recovery period of either: (i) passive rest, (ii) 5-min CWI at 8 °C (CWI-5) or (iii) 2.5-min CWI at 8 °C (CWI-2.5), in a random counterbalanced order.Results: Physical performance, core temperature (Tcore) and heart rate were not different among conditions in the first half. In the passive rest trial, total work (TW) and peak power (PP) were lower during the second half (TW: 5.04 ± 1.11 kJ; PP: 929 ± 286 W) than the first half (TW: 5.66 ± 1.02 kJ; PP: 1009 ± 266 W); while TW and PP were not different between halves following CWI-5 (first half, TW: 5.34 ± 1.02 kJ, PP: 1016 ± 283 W; second half, TW: 5.19 ± 1.38 kJ; PP: 996 ± 318 W) and CWI-2.5 (first half, TW: 5.47 ± 1.19 kJ, PP: 966 ± 261 W; second half, TW: 5.25 ± 1.17 kJ; PP: 952 ± 231 W). Tcore was lower until the 20th minute of the second half after CWI-5 and CWI-2.5 compared with passive rest.Conclusions: A post-exercise 2.5-5-min CWI attenuates the reductions in prolonged sprint performance that occur in the second half of team sports, due, at least partly, to reductions in core temperature and associated increase in heat storage. [ABSTRACT FROM AUTHOR]

This study ranks the effective factors in the output power of the low concentrator photovoltaic system (LCPVS) with 4 mirrors using Feature Selection (FS) approach through Ant Colony Optimization (ACO) method based on the analysis of the system improvements in summer and winter. The aim was to improve the intensity of solar irradiation on the same surface area of photovoltaic (PV) panel using mirrors, which led to an increase in power output. The proposed system comprised 4 mirrors that reflected solar radiation to PV panel surface, that was cooled by water spraying, in the most perpendicular position possible. Having done with the related experiments, the results were compared with reference panel. It was demonstrated that the average DC power output of the LCPVS with 4 mirrors was roughly the same, and it was 2.8 times more than that of the reference panel in summer and winter. Moreover, the average DC power output improvement in PV panel was 184.01% in summer and 179.42% in winter. The parameters influencing the output power of PV panel were ranked accordingly by FS approach through ACO. The developed system has the potential to be useful throughout the winter and can also be set up in the majority of regions across the globe. [ABSTRACT FROM AUTHOR]

Wake interference between wind turbines potentially decreases the power output of offshore wind farms. While the staggered arrangement shows promise for mitigating this interference, the understanding of the impact of vertically staggered setup remains ambiguous, especially in the case of vertical-axis wind turbines (VAWTs). Also, the difference between horizontally and vertically staggered arrangements needs to be clarified. This study aims to shed light on these ambiguities, systematically evaluating the effectiveness of vertically staggered arrangement in mitigating wake interference between offshore VAWTs. High-fidelity computational fluid dynamics simulations are used to investigate the wake interference between two vertically staggered MW-class VAWTs. Typical separation distances (3 D ≤ L S ≤ 7 D) and different vertically staggered distances (−0.25 H ≤ L V ≤ 0.75 H) are considered, where D and H denote the turbine diameter and blade span length, respectively. Employing the Taguchi method, the effectiveness of horizontally and vertically staggered arrangements is compared, and the relatively optimal layout of the turbine array is identified. The results show that the vertically staggered arrangement significantly improves the power performance of the downstream turbine, e.g., the power output increases by 75.96% when L S = 7 D and L V = 0.25 H. When dealing with smaller L S (e.g., 3 D), a negative L V is suggested, which reduces the tower cost while preserving the performance improvement. The vertically staggered arrangement has a greater impact on wake interference than the horizontally staggered arrangement. In terms of the relatively optimal layout, the power output of the turbine array is increased by 46.27%. These findings would contribute to the layout design of offshore wind farms. • Wake interference between two staggered offshore MW-class VAWTs is investigated. • Knowledge of how vertically staggered arrangement affects wake interference is enriched. • Effectiveness of horizontally and vertically staggered arrangements is compared. • Relatively optimal layout of the turbine array is identified based on the Taguchi method. • Findings would contribute to the layout design of offshore wind farms. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) are an efficient approach to converting energy existing in waste into electricity. However, MFCs still face problems such as low electron transfer rate and low power density. Herein, the anode properties dominate the performance of MFC. This study manufactured a high-performance MnCo 2 S 4 –CoS 1.097 /carbon black carbon felt (T-MCS-CS/CB-CF) anode through a two-step hydrothermal method. T-MCS-CS/CB catalyst exhibited superior surface roughness and mesoporous structure. Besides, the excellent electrocatalytic activity of the T-MCS-CS/CB catalyst with the heterostructure resulted in the higher power output. After biofilm formation, T-MCS-CS/CB-CF anode exhibited lower Rct (9.29 Ω) than MnCo 2 S 4 -Co 4 S 3 / carbon black carbon felt (MCS-CS/CB-CF (15.83 Ω)), carbon black carbon felt (CB-CF (29.52 Ω)) and CF anode (116.1 Ω), exhibiting higher electrochemical activity. T-MCS-CS/CB-CF anode enhanced extracellular electron transfer (EET) and improved the power density, which was 12.29 times higher (1299.27 mW/m2) than the bare CF (105.70 mW/m2). The relative abundance of Geobacter for T-MCS-CS/CB-CF (21.65 %) was 7.24 times higher than the control CF anode (2.99 %). Moreover, T-MCS-CS/CB modification enriched exoelectrogens/sulfate-reducing bacteria, Desulfovibrio , 4.69 % higher than the CF anode, which attributed to the introduction of CoS 1.097. The excellent electrocatalytic activity, surface properties and biocompatibility of T-MCS-CS/CB-CF promoted the power output in MFC. This study provided an effective way of anodic electrocatalyst fabrication for enhancing the power generation of MFC. • Unique geometry structure of the T-MCS-CS facilitated the biofilm formation. • T-MCS-CS/CB-CF electrode exhibited remarkable electrocatalytic activity. • Stimulated electron transfer efficiency of electrochemically active bacteria by T-MCS-CS. • The introduction of CoS 1.097 resulted in the abundance of Desulfovibrio. • T-MCS-CS/CB modification resulted in the enrichment of exoelectrogens Geobacter and Desulfovibrio. [ABSTRACT FROM AUTHOR]

• A hybrid solar energy conversion system consisting of PV/T-PCM, and TEG was designed. • The solar PV/T-PCM-TEG hybrid energy conversion system was experimentally investigated. • The efficiency of the PV/T-PCM-TEG system was increased with copper fins and the addition of Al 2 O 3 to the PCM. • The efficiency of the standard PV panel, which was about 30%, was increased to 35.2% with the PV/T-PCM-TEG hybrid system. In PV cells consisting of p-type and n-type semiconductor materials, electricity is produced with part of the solar radiation coming to the cell surfaces, while the rest causes the cells to rise in temperature, thus decreasing the conversion efficiency. Therefore, controlling the cell temperature is very important in terms of conversion efficiency. In this paper, passive cooling was performed by storing the heat acting on the PV panel with a 40 W harvesting capacity in the phase change material (PCM) in contact with the back surface. Simultaneously, active cooling was achieved by transferring the heat stored in the PCM to the hot-side surface of the integrated thermoelectric generator (TEG) with the help of the heat transfer fluid circulated in the copper pipes inside the PCM. Thus, the base hybrid system (PV/T-PCM-TEG) design (Case_1), which increases thermal stabilization of cells, was realized. While 20 thermoelectric modules are used in TEG, RT55 paraffin wax is used as PCM in the empty space on the back surface of the PV panel. In addition, to improve the PV/T-PCM-TEG system efficiency, three different cases were created by adding Al 2 O 3 nanoparticles into the PCM (Case_2) and by placing copper fins around the copper pipes (Case_3). As a result, the power output of PV/T-PCM-TEG is 10.29%, 12.73%, and 14.22% higher for Case_1, Case_2, and Case_3, respectively, than the standard PV panel. In addition, the maximum PV panel efficiency is 30%, while the efficiency of PV/T-PCM-TEG increased to 32.8% with Case_1, 33.9% with Case_2, and 35.2% with Case_3. [ABSTRACT FROM AUTHOR]

Polymer electrolyte fuel cell (PEFC) development goes hand in hand with a complete understanding of its behavior in realistic operating conditions. Hence, analysis based on characterizations is essential to determine the predominant effects strongly affecting PEFC performance. Experimental research is carried out using a single PEFC under controlled conditions. The primary objective is to examine the cell's maximum power output through polarization curves, Nyquist diagrams, and internal resistant graphs. The analysis is performed, varying the cell's relative humidity (RH) from 16% to 100%. The results are accomplished by employing current sweep load and electrochemical impedance spectroscopy. It was demonstrated that the operation at the maximum power of a PEFC is optimized in the relative humidity range of 66-100%. This range allows for a balance of proper hydration of the polymer membrane and the availability and activation of reaction sites. The internal resistances were evaluated individually and presented in graphs showing a decrease when the RH increases, where ohmic and mass transport resistances are the most affected by the RH. Furthermore, the mass transport and ohmic resistances were dominant at low RH. In contrast, ohmic and charge transfer resistance were prevalent at high RH, indicating the required improvements at these points. Finally, several correlations are proposed to obtain internal resistance values as a function of the RH with a confidence interval of 95%. [ABSTRACT FROM AUTHOR]

The cathode air flow rate and relative humidity (RH) of a trickle-bed microbial fuel cell (TB-MFC) were optimized using the response surface methodology to obtain a high oxygen flux and a low electrical resistance at the cathode and thereby promote the oxygen reduction reaction. Under optimal air flow rate (2.20 L/min) and RH (20%) conditions, the TB-MFC system exhibited the highest oxygen flux (3.08%/cm2‧min) and the lowest resistance (5.33 Ω); its regression model had an R2 > 0.95 and the desirability coefficient was 0.78. These results demonstrate that the optimized air flow rate and RH support high oxygen flux and low resistance at the cathode. Using biochar combined with conductive carbon black (CCB) as the cathodic catalyst and optimal cathodic operating conditions, yielded a mineralization efficiency of isopropanol of 96.9% and a power density of 555 mW/m3 at an empty bed residence time and isopropanol influx concentration of 60 s and 300 ppmv, respectively. These results suggest that isopropanol can be effectively mineralized directly into CO 2 and H 2 O by a TB-MFC, reducing the by-product accumulation, and thus increasing the power generation of the TB-MFC. Optimizing the air flow rate and RH of the biochar/CCB-based cathode in the TB-MFC increases the oxygen flux and reduces the electrical resistance of the cathode of TB-MFC, which can thus be used to treat exhaust gases that contain organics. [Display omitted] • A trickle-bed microbial fuel cell (TB-MFC) was optimized to output high power. • Use of biochar as a cathodic catalyst in TB-MFC promoted oxygen reduction reaction. • Electrical resistance was positively correlated with air flow rate and humidity. [ABSTRACT FROM AUTHOR]

• A novel photovoltaic-electrochemical hybrid system is proposed. • Multiple irreversible losses within the proposed system are described. • Performance parameters for the proposed system are obtained. • The proposed system is effective to harvest relatively high wavelength sunlight. • Effects of some microstructure parameter and operating conditions are revealed. To harvest the relatively high wavelength sunlight, a novel hybrid system coupling a thermally regenerative electrochemical cycle to a dye-sensitized solar cell is proposed. Efficiencies and power outputs of dye-sensitized solar cell and thermally regenerative electrochemical cycle are calculated, and the mathematical relationship between the electric current of thermally regenerative electrochemical cycle and the working current density of dye-sensitized solar cell is deduced. The power output and efficiency of the hybrid system are also derived considering multiple irreversible losses. The feasibility and effectiveness of the proposed hybrid system will be assessed by comparing the performances between the hybrid system and the single dye-sensitized solar cell. Numerical calculations show that the maximum efficiency and power density of the hybrid system allow 32.04% and 32.18% greater than that of the single dye-sensitized solar cell, respectively. Comprehensive parametric studies are undertaken to examine the dependences of the hybrid system performance on some operating conditions and microstructure parameters, including electrode porosity, photoelectron absorption coefficient, Schottky barrier, film thickness and internal resistance of thermally regenerative electrochemical cycle. The derived results may offer new insights into design and optimization of such an actual hybrid system. [ABSTRACT FROM AUTHOR]

This paper concerns the prediction of the power outputs of wave energy converters (WECs) operating in shallow water nonlinear waves. The bottom effects on the power performances of WECs (a phenomenon that has always been overlooked by the previous researchers) have been taken into account during the calculations. Using an oscillating surge wave energy converter (OSWEC) as an example, it is demonstrated in this article that for each sea state using linearly simulated waves without bottom effects as inputs in the simulation will always predict the OSWEC's power output more than 200% higher than the result predicted by inputting nonlinearly simulated waves with bottom effects. Therefore, nonlinear simulated waves with bottom effects should instead be utilized as inputs in the simulation process. In order to further improve the simulation efficiency, a novel transformed linear simulation method is first proposed in this paper for generating equivalent waves as those obtained from the nonlinear simulation method. Further calculation examples show that the relative error of the predicted power output value when inputting transformed linearly simulated waves is always less than or equal to 1.97%. • The power outputs of a wave energy converter are predicted. • The bottom effects are considered. • Nonlinear random waves are simulated. • A novel transformed linear simulation method is proposed. • The accuracy and efficiency of the novel method are substantiated. [ABSTRACT FROM AUTHOR]

Abstract The operating temperature of concentrated photovoltaic (CPV) system has a significant impact on the transient response of the CPV system. The heat generated inside the CPV module degrades the performance, reliability and life span of the system. Therefore, in order to regulate the temperature of CPV system, phase change materials (PCM) are used as an effective passive thermal management method. A CPV integrated with heat sink and PCM has been developed in finite element software COMSOL Multiphysics. The PCM was integrated at the back side of CPV module to maintain constant and low temperature in the CPV module. The performance of low CPV was carried out by varying the fill volume of PCM and solar concentration ratio (CR). The results showed a significant reduction in the temperature of the CPV module with the addition of PCM compared to the CPV without PCM. The CPV temperature observed was 55 °C with PCM height of 0.75 mm with a reduction to 32 °C with the PCM height of 3 mm in the heat sink. The CPV temperature was maintained constant during the melting period of the PCM from 25s to 120s with PCM height of 3 mm and CR of 3. The results showed an increase in the power output and efficiency of the CPV module with increase in the fill volume of PCM in the heat sink. For a typical operating condition with CR of 3 and PCM height of 3 mm, the power output and efficiency of CPV with PCM was found to be 27% and 22% higher than the case without PCM respectively. Highlights • CPV integrated PCM system has been developed in COMSOL Multiphysics. • Effect of fill volume of PCM and CR have been studied on PCM temperature. • A significant reduction in CPV temperature is observed with addition of PCM. • CPV temperature is maintained constant during the melting period of the PCM. • CPV module power output and efficiency increase with increase in PCM fill volume. [ABSTRACT FROM AUTHOR]

Abstract Conversion of mechanical energy into electricity using triboelectric nanogenerators (TENGs) is a rapidly expanding research area. Although the theoretical origin of TENGs has been proven using the Maxwell's displacement current (I D), a profound quantitative understanding of its generation is not available. Moreover, a comprehensive analysis of the fundamental charging behavior of TENGs and building a standard to evaluate each TENG's unique charging characteristic are critical to ensure efficient use of them in practice. We present a thorough analysis of TENG's charging behavior through which a more complete evaluation of TENG charging is proposed by introducing the structural figure of merit (FOMCs) in a charging system (powering capacitors). The analysis is based on Maxwell's displacement current and results are verified experimentally. To achieve this, according to the distance-dependent electric field model, we provide a systematic discussion on the generation of I D in TENGs, along with the derived analytical formula and numerical calculations. This work suggests a new way to deeply understand the nature of the I D generated within the TENGs; and the modified FOMC S can be used to predict the charging characteristics of TENGs in an energy storage system, allowing us to utilize the TENGs more efficiently towards different applications. Graphical abstract fx1 Highlights • A standardized evaluation of TENGs, i.e. , the structural figure of merit in a TENG charging system (FOMC S) is proposed. • The modified FOMC S can be used to predict the charging characteristics of TENGs in an energy storage system. • This work establishes an in-depth understanding of the nature of the Maxwell displacement current in a TENG. [ABSTRACT FROM AUTHOR]

Abstract This paper concerns the prediction of the power output performances of an oscillating surge wave energy converter in irregular waves. The generated power has been calculated using a new methodology by incorporating a stochastic Lagrange wave model into a non-linear filter which takes also hydrodynamic forces into account. It is shown that the stochastic Lagrange wave model in this paper can be utilized to generate irregular waves with realistic crest-trough and front-back asymmetries, and when used in combination with the non-linear filter will produce more accurate power output predictions than the traditional Gaussian wave model can do. The research findings in this paper demonstrate that the stochastic Lagrange wave model together with a non-linear filter can be utilized as a robust tool for engineers in their design, analysis and optimization of wave energy converters. Highlights • The power performances of a wave energy converter are investigated. • The generated power is calculated using a new methodology. • A stochastic Lagrange wave model is utilized. • A non-linear filter is utilized. • The new methodology is demonstrated to be robust. [ABSTRACT FROM AUTHOR]

Abstract The design of the current collectors (CCs) used in fuel cells is crucial as it affects the energy density generated from these systems. This is due to the fact that different designs will lead to different charge, heat and mass transport phenomena. Therefore, towards the optimization of these devices, it is required to have a deep knowledge of the effect of the CC geometry on the cell performance. The present work intends to evaluate that, by studying the effect of the anode and cathode CC configuration on the power output of a passive direct methanol fuel cell (pDMFC) operated at ambient conditions. Three different perforated CCs, each one with a different open ratio, and an open window frame CC were tested at both anode and cathode sides. The pDMFC performance was evaluated through the polarization and power density curves and the experimental results were explained under the light of the electrochemical impedance spectroscopy (EIS) measurements. At this point we introduced an innovative electric equivalent circuit allowing the identification of the different losses, including the activation resistance of the parasitic cathode methanol oxidation. The best power output, 3.14 mW/cm2, was achieved with the perforated CC with the lower open ratio (34%) on both sides and feeding the cell with a methanol concentration of 2 M. [ABSTRACT FROM AUTHOR]

Abstract Large-eddy simulation (LES) is used to investigate the effect of the spatial arrangement of a utility-scale wind turbine array on the power outputs. Eight turbine-array layouts are considered, where each has 120 turbines installed in 30 rows with aligned or staggered configurations along the wakewise direction. We perform the LESs of neutrally-stratified atmospheric boundary layer over the eight large wind farms with the turbines arranged with a perfectly-aligned configuration, four laterally-staggered configurations, and three vertically-staggered configurations. Unlike the alignment of the turbine micro-siting in the aligned wind farm, both the laterally-staggered and vertically-staggered configurations lead to the misalignment of the turbines with staggered arrangement in the lateral and vertical directions. Simulation results show that the power outputs in the wind farms have obvious decreases to 45–65% within the first 12 turbine rows and retain within that range in the rest. In general, the staggered wind farms produce more power than the aligned wind farm. The laterally-staggered wind farm configurations due to the better adaptability in spatial configuration provide higher power production in the first 6th turbine rows. Moreover, the vertically-staggered configuration causes clear reduction in the maxima of the velocity deficit and the turbulence intensity inside the farm wake flow. Highlights • A validated LES framework is used to quantify the power output in a large wind farm with 120 turbines installed. • Three types of turbine arrays are considered: aligned, laterally-staggered, and vertically-staggered configurations. • The laterally-staggered configuration can promote more power generation in the first 6 turbine rows. • The vertically-staggered configuration leads to clear reduction in the maxima of the velocity deficit and the turbulence intensity. [ABSTRACT FROM AUTHOR]

Abstract A solar parabolic dish photovoltaic (PV)-thermoelectric (TE) power generation system was devised, and its behavior continuously measured under realistic outdoor circumstances. The effect of focal distance was also analyzed. The experimental results showed that the conversion of TE, PV and overall efficiency were 2.96, 16.69 and 19.65%, respectively at the focal distance of 57 cm. The unit obtained its electrical power out from a 2.94 W TE generator and a 1.93 W PV module. The PV module was used to drive a fan for cooling the TE generator and itself. Because of its noiseless operation, light weight, high reliability, and overall environmental friendliness, this concept can be used to solve power supply limitation for low-power wireless sensors. [ABSTRACT FROM AUTHOR]

Background: The force- and power-velocity (F-V and P-V, respectively) relationships have been extensively studied in recent years. However, its use and application in endurance running events is limited.Research Question: This study aimed to determine if the P-V relationship in endurance runners fits a linear model when running at submaximal velocities, as well as to examine the feasibility of the "two-point method" for estimating power values at different running velocities.Methods: Eighteen endurance runners performed, on a motorized treadmill, an incremental running protocol to exhaustion. Power output was obtained at each stage with the Stryd™ power meter. The P-V relationship was determined from a multiple-point method (10, 12, 14, and 17 km·h-1) as well as from three two-point methods based on proximal (10 and 12 km·h-1), intermediate (10 and 14 km·h-1) and distal (10 and 17 km·h-1) velocities.Results: The P-V relationship was highly linear ( r = 0.999). The ANOVAs revealed significant, although generally trivial (effect size < 0.20), differences between measured and estimated power values at all the velocities tested. Very high correlations ( r = 0.92) were observed between measured and estimated power values from the 4 methods, while only the multiple-point method ( r2 = 0.091) and two-point method distal ( r2 = 0.092) did not show heteroscedasticity of the error.Significance: The two-point method based on distant velocities (i.e., 10 and 17 km·h-1) is able to provide power output with the same accuracy than the multiple-point method. Therefore, since the two-point method is quicker and less prone to fatigue, we recommend the assessment of power output under only two distant velocities to obtain an accurate estimation of power under a wide range of submaximal running velocities. [ABSTRACT FROM AUTHOR]

Highlights • Relationship of shaded proportion with photocurrent and series resistor is studied. • A simplified mathematical model for power output predicting is proposed. • Electrical performance for shaded photovoltaic module is simulated. • More power output when the shadow is parallel with long edges than short edges. • Solutions to maximize output power of Building Integrated Photovoltaic is analyzed. Abstract Shadow will make power output loss for Building Integrated Photovoltaic system. Power output predicting of Building Integrated Photovoltaic is always complicated due to multi-parameters, especially under partial shading conditions. In this paper, effects of partial shadow on the photocurrent and series resistor is analyzed, relationship of shaded cell area proportion with photocurrent and series resistor is obtained respectively, and based on this, a simplified mathematical model to describe the relationship between shaded cell area proportion and current-voltage, power-voltage characteristics of a photovoltaic module under partial shading conditions is proposed and verified by experiments. Electrical performance of the photovoltaic module under different shading scenarios is predicted using the simplified mathematical model, and the predicted results have a high consistency with experiments using the monocrystalline silicon photovoltaic module. The results show that under same shaded area proportion, the shadow distributing in parallel with the short edge, which makes photovoltaic modules power output 3 W/m2 under 10% shaded area, has much more negative effects than distributing in parallel with the long edge. The power output of a photovoltaic string protected by one bypass diode depends on the largest shaded cell area proportion, when the largest shaded cell area proportion is around 45%, the photovoltaic string has no contribution to power output of the whole photovoltaic module. Therefore, in order to minimize the influence of shadow on the power output of a photovoltaic module, for Building Integrated Photovoltaic system meeting inevitable shadow with regular shape, the photovoltaic module should be arranged to make the shadow distributed uniformly on the cells protected with one bypass diode; but for Building Integrated Photovoltaic system meeting inevitable shadow with irregular shape, the module of whom every piece of cells parallels a diode is recommended. [ABSTRACT FROM AUTHOR]

Abstract Microbial fuel cells (MFCs) have been receiving an increased attention over the last years due to their potential to combat two global problems: waste pollution and energy demand. Additionally, when a wastewater is used, MFCs can perform its treatment while recovering energy, leading to the possibility of energy-producing wastewater treatment plants, offsetting their operational costs. However, to overcome their current limitations (lower power outputs and higher costs), a clear understanding of the effect of operation and design parameters on its overall performance is mandatory. Therefore, the goal of this work was to evaluate the effect of operating conditions - batch cycle and yeast extract concentration, and design parameters - anode electrode area, membrane thickness and active area, on the overall performance of a single chamber MFC. The MFC operated with a pure culture of Lactobacillus pentosus and a synthetic wastewater based on a real dairy industry effluent. The overall performance was evaluated through the power output and the COD removal rate. Additionally, the biofilm formed at the anode electrode was characterized in terms of biomass, proteins and polysaccharides content. For the conditions used in this work, a maximum power density of 5.04 ± 0.39 mW/m2 was achieved with an anode electrode area of 61 cm2, a batch cycle of 48 h, 50 mg/L of yeast extract and a Nafion 212 membrane with an active area of 25 cm2. The different conditions tested had a clear effect on the MFC energy production and biofilm characteristics, but not on the ability of L. pentosus to treat the dairy wastewater. The COD removal rates were in the range between 42% and 58%, for all the conditions tested. Graphical abstract Unlabelled Image Highlights • An experimental study of a feed-batch SCMFC with L. pentosus is described. • The effect of different parameters on the SCMFC performance is presented. • Different parameters were tested in order to achieve high power outputs. • The biofilm formed on the anode electrode was characterized for each parameter studied. • The maximum power density achieved was 5.04 mW/m2 with a COD removal rate of 50%. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cathodic autotrophic (AD) and heterotrophic (HD) denitrification were compared. • Power density (4.45 W m−3) was high in AD MFC. • Nitrate removal rate (2.06 kg N O 3 - -N m−3 d−1) was high in HD MFC. • High microbial diversity and some common species were found in both conditions. • RT-PCR studies confirmed narG , nirS , and nosZ presence in both conditions. Abstract A comparison of autotrophic (AD) and heterotrophic (HD) cathodic denitrification in a Microbial Fuel Cell (MFC) was made in this study. Denitrifying microbial consortia were developed from cow manure and soil and acclimatized under AD and HD conditions. The AD MFC supported the power output of 4.45 W m−3 while removing nitrate nitrogen (N O 3 - -N) at the rate of 0.118 kg N O 3 - -N m−3 d−1. Significant power output (3.02 W m−3) and nitrate removal rate (2.06 kg N O 3 - -N m−3 d−1) were achieved in HD MFC. Further, 16S rDNA based community analysis revealed higher diversity in HDMFC. The genus Thauera and Pseudomonas were predominant in ADMFC while genus Klebsiella and Alkaliphilus were abundant in HDMFC. The abundance of the denitrifying genes namely narG , nirS , and nosZ were assessed with the help of quantitative PCR and presence of all the genes in both the conditions ensured the necessary molecular requirements for complete denitrification. [ABSTRACT FROM AUTHOR]

Abstract Despite the net energy yield be the primary goal of ethanol electro-oxidation reaction (EOR), it is never measured in fundamental electrochemical studies. By combining galvanodynamic and potentiodynamic profiles of the steady states of the system, we demonstrate a methodology to estimate the dissipation of chemical energy that allows the inference of the fuel cell power output in relative terms. Apart from the empirical energy dissipation, several kinetic information are unravelled: (a) the kinetics is governed by ethanol adsorption rate for both media and for both external control modes; and (b) either the maximum current sustained by EOR or the steady state currents are, in addition, governed by a global coverage of poisonings species, which includes the contributions from CO ad and non-reactive OH ad. The blocking effect of potassium cations over EOR is clearly verified, reducing the maximum activity up to a factor of 0.19, which is interpreted as an effect of the high coverage of non-reactive OH ad. Finally, it is expected a slightly improvement of the power output of a direct ethanol fuel cell operating at steady state in alkaline media due to the lower chemical dissipation at fixed interfacial current value. Nonetheless, the blocking effect of potassium in alkaline media may, depending on the concentration, either induces an oscillatory regime at higher overvoltage (above 0.57 V) along with the preservation of the energy generation at lower overvoltage or completely decrease the energy generation due to a drastic loss of energy used to polarize the EOR. Graphical abstract Image [ABSTRACT FROM AUTHOR]

Abstract The main purpose of this study was to assess the influence of the environmental temperature on both the aerodynamic flow evolving around the bicycle and cycling power output. The CFD method was used to investigate the detailed flow field around the cyclist/bicycle system for a constant speed of 11.1 m/s (40 km/h) without wind. In complement, a mathematical model was used to determine the temperature-dependent power output in the range [−10; 40 °C]. The numerical investigation gives valuable information about the turbulent flow field in the cyclist's wake which evolves accordingly the surrounding temperature. A major result of this study is that the areas of overpressure upstream of the cyclist and of underpressure downstream of him are less extensive for a temperature of 40 °C compared to −10 °C. The results suggest that the aerodynamic braking effect of the bicycle is minimized when the air temperature is high, as a lower air density results in a reduction in drag on the cyclist. This study showed that the power required to maintain a constant speed is reduced when the temperature is high, the reason being a lower aerodynamic resistance. [ABSTRACT FROM AUTHOR]

Summary Aims To analyse performance across the menstrual cycle using optimal load and a velocity-based training, and to check the impact of dysmenorrhea in this type of training. Methods Five eumenorrheic women with a normal menstrual cycle participated in four performance tests: 20-meter linear sprint, counter-movement jump, bench-press and half-squat. The tests were performed at the time of menstruation and in the luteal-phase. In addition, data of mood states, sleep quality and rate of perceived exertion in both phases were collected. To analyse dysmenorrhea, subjects fulfilled a menstrual pain questionnaire. Analysing the group as a whole, better results were only found in the repetition maximum of the half-squat in the menstruation phase. Results When analysing the group dividing it according to pain variables, the group that presented some pain variable showed worse test results in both phases with respect to the no pain group in both half-squat and bench-press. In addition, the pain group showed a lower repetition maximum in both half-squat and bench-press in the luteal-phase, whereas the no pain group presented a similar repetition maximum in both phases. There were no differences in any other tests. Menstrual pain seems to be involved in the differences obtained in the test results, since the no pain group obtained better results than the pain group in both phases, and they also maintained their values constant throughout the menstrual cycle, whereas the pain group presented a decrease in performance in the luteal-phase. [ABSTRACT FROM AUTHOR]

Based on finite time thermodynamics, a simple irreversible supercritical organic Rankine cycle (SORC) model is set up. Subjected to the total heat conductance constraint of heat exchangers, the power output (PO) and thermal efficiency (TE) of the SORC are maximized firstly by varying the heat conductance distributions of heat exchangers and mass flow rate of organic working fluid. The results reveal that in the discussed variation ranges of the optimization variables, the PO and TE of the SORC after triple optimizations are augmented by 39.45% and 7.13%, respectively, and the optimization effects of the triple optimizations are remarkable. Moreover, the optimization results gained by the triple maximizations of the PO and TE, respectively, are evidently different. In the discussed working fluids, the order of the triple maximum POs of the SORCs is R143a > R218 > R125 > R41 > R245fa, thus the recommended working fluid corresponding to the largest PO is R143a. The multi-optimization of the PO and TE are secondly performed by using NSGA-II, the optimal parameters of the SORCs with R125 and R143a acquired by TOPSIS and Shannon Entropy decision-making methods are taken for the optimal design schemes, respectively. The gained results in this paper offer useful design guidelines for the practical SORCs. [Display omitted] • A simple supercritical organic Rankine cycle model with finite temperature difference is built. • Power output and thermal efficiency are optimized with fixed total heat conductance. • Power output and thermal efficiency after optimizations are augmented by 39.45% and 7.13%. • The recommended working fluid corresponding to a higher power output is R143a. • The optimal scheme for the cycle with R143a is the one selected by Shannon Entropy method. [ABSTRACT FROM AUTHOR]

• Prediction of power production of photovoltaic module considering ambient weather conditions. • Predictive models have been developed using both artificial neural network and regression analysis. • Solar irradiation, ambient and module temperature are key factors and important variables to estimate PV power generation. • Performance of developed models was evaluated and compared to other models in the literature. This paper proposes artificial neural network (ANN) and regression models for photovoltaic modules power output predictions and investigates the effects of climatic conditions and operating temperature on the estimated output. The models use six days of experimental data creating a large dataset of 172,800 × 7. After data preprocessing, the appropriate attributes were selected as inputs and taken into account as features; solar irradiation, ambient air and module temperature, wind speed, and relative humidity, while the power generation as a target. In light of these data, the effect of training algorithm on the predictive performance of the ANN model was investigated. Results show that solar irradiation, ambient and module temperatures are key factors in predicting PV module power generation, as these variables are strongly correlated with PV power output. Moreover, the Levenberg-Marquardt algorithm was found to be the best training procedure. The ANN model demonstrated higher accuracy than the developed multiple linear regression models. However, the proposed Rational-Power-Law (RPL) and Power-Law (PL) models were able to capture the nonlinearity in the system, as assessed by coefficient of determination (R2) and the Mean Absolute Error (MAE), and successfully supplied a very high level of precision. The ANN, and both RPL and PL models provided comparable performance, attaining an R2 of 0.997, 0.998 and 0.996, and a MAE of 1.998, 1.156, and 1.242, respectively, when compared to experimental results. Furthermore, models proposed in this study were evaluated and compared with others available in literature and have demonstrated superior performance and better accuracy. [ABSTRACT FROM AUTHOR]

Objective To compare the effects of 12 weeks of high-speed resistance training on functional performance and quality of life in elderly women when using either a traditional-set (TS) or a cluster-set (CS) configuration for inter-set rest. Methods Three groups of subjects were formed by block-design randomization as follows: (i) control group (CG, n  = 17; age, 66.5 ± 5.4 years); (ii) 12-week high-speed resistance training group under a CS configuration (CSG, n  = 15; age, 67.6 ± 5.4 years); and (iii) 12-week high-speed resistance training group under a TS configuration (TSG, n  = 20; age, 68.0 ± 5.3 years). Training was undertaken three times per week, including high-speed resistance training exercises. The main difference between the training groups was the recovery set structure. In the TSG, women rested for 150 s after each set of eight repetitions, whereas the CSG used an interest rest redistribution, such that after two consecutive repetitions, a 30-s rest was allowed. Results Group × test interactions were observed for a 10-m walking speed test, an 8-foot up-and-go test, a sit-to-stand test, and physical quality of life (p < 0.05; d = 0.12–0.81). The main results suggest that both training methods improve functional performance and quality of life, however, the CS configuration induced significantly greater improvements in functional performance and quality of life than the TS configuration. Conclusion These results should be considered when designing appropriate and better resistance training programs for older adults. [ABSTRACT FROM AUTHOR]

This paper establishes an air-standard irreversible Dual-Miller cycle (DMC) model with the specific heat ratio (SHR) of working fluid (WF) linearly varying with its temperature. Because the specific heat (SH) of WF varies with combustion reaction in actual internal combustion engine (ICE), the SHR of WF should be a function of temperature but not a constant. In order to accurately reflect the practical characteristics of DMC engine, performance of DMC with linearly variable SHR, and with heat transfer (HT) loss, friction loss (FL) and other internal irreversible losses (IILs) is analyzed and optimized by applying finite-time thermodynamics. Analytical formulae of the power output ( P ), efficiency ( η ), entropy generation rate (EGR) and ecological function ( E ) are derived. Relationships among P , η , E and compression ratio are obtained via numerical calculations. Effects of the design parameters, cycle temperatures and linearly variable SHR of WF on P , η and E are investigated. Performance differences among the DMC and its simplified cycles, including Otto cycle (OC), Dual cycle (DDC) and Miller cycle (OMC) are compared. Performance characteristics of the DMC with different optimization objective functions (OOFs) are analyzed. The results indicate that the maximum power output ( MP ), maximum efficiency ( MEF ) and maximum ecological function ( ME ) of the DMC are superior to those of OC, DDC and OMC, and optimizing E is the best compromise between optimizing P and optimizing η . The presented results may be helpful to optimize the performance of practical DMC engines. [ABSTRACT FROM AUTHOR]

It is well known that muscular force production is history-dependent, which results in enhanced (RFE) and depressed (RFD) steady-state forces after stretching and shortening, respectively. However, it remains unclear if force-enhancing mechanisms can contribute to increased performance during in vivo stretch-shortening cycles (SSCs) of human locomotor muscles. The purpose of this study was to investigate whether RFE-related mechanisms contribute to enhanced force and power output during SSCs of the human plantar flexor muscles. Net ankle torques of fourteen participants were measured during and after pure isometric, pure stretch, pure shortening, and SSC contractions when the triceps surae muscles were electrically stimulated at a submaximal level that resulted in 30% of their maximum isometric torque. Dynamic contractions were performed over an amplitude of 15°, from 5° plantar flexion to 10° dorsiflexion, at a speed of 120° s −1 . External ankle work during shortening was 11.6% greater during SSCs compared to pure shortening contractions (p = .003). Additionally, RFD after SSCs (8.6%) was reduced compared to RFD after pure shortening contractions (12.0%; p < .05). It is therefore concluded that RFE-related mechanisms contribute to increased performance following SSCs of human locomotor muscles. Since RFD after SSCs decreased although work during shortening was increased, we speculate that the relevant mechanism lies outside actin-myosin interaction. Finally, our data suggests that RFE might be relevant and beneficial for human locomotion whenever a muscle is stretched, but this needs to be confirmed. [ABSTRACT FROM AUTHOR]