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Abstract To investigate the effect of force distributions of each turbine component on the power performance of the Darrieus–Savonius combined vertical axis wind turbine (hybrid VAWT), the hybrid VAWT is modeled as idealized turbine under various force distributions. The goal of idealization is to simplify the intricate interactions between the Savonius and Darrieus components. The simulation actuator surfaces with uniform force distributions lead to a cost‐effective way to identify the optimal force distribution of each turbine component. The numerical model was validated against momentum theory. The results demonstrated that the numerical and theoretical results yield similar predictions in the low‐thrust cases but show differences in the high‐thrust cases. The maximum power coefficient cpmax of an idealized hybrid VAWT with given thrust coefficient cTAD is lower than that of a single actuator. This is a consequence of the nonoptimal loading on the actuator. The results indicate that an idealized hybrid VAWT does not show a significant power increase compared with an optimal single Darrieus rotor. Therefore, the presence of a Savonius rotor inside a Darrieus rotor leads to a lower power output in any circumstance. The hybrid configuration is primarily advantageous for the start‐up performance of the combined rotor, which is not explored in this study.

To investigate the effect of force distributions of each turbine component on the power performance of the Darrieus–Savonius combined vertical axis wind turbine (hybrid VAWT), the hybrid VAWT is modeled as idealized turbine under various force distributions. The goal of idealization is to simplify the intricate interactions between the Savonius and Darrieus components. The simulation actuator surfaces with uniform force distributions lead to a cost‐effective way to identify the optimal force distribution of each turbine component. The numerical model was validated against momentum theory. The results demonstrated that the numerical and theoretical results yield similar predictions in the low‐thrust cases but show differences in the high‐thrust cases. The maximum power coefficient cpmax of an idealized hybrid VAWT with given thrust coefficient cTAD is lower than that of a single actuator. This is a consequence of the nonoptimal loading on the actuator. The results indicate that an idealized hybrid VAWT does not show a significant power increase compared with an optimal single Darrieus rotor. Therefore, the presence of a Savonius rotor inside a Darrieus rotor leads to a lower power output in any circumstance. The hybrid configuration is primarily advantageous for the start‐up performance of the combined rotor, which is not explored in this study. [ABSTRACT FROM AUTHOR]

Copyright of Revija Šport is the property of Sport: Revija Za Teoreticna in Praticna Vprasanja Sporta and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The ship-mounted photovoltaic (PV) system was an approach to solve the problem of pollution caused by excessive energy consumption during navigation. However, PV systems used on ships faced problems such as small installation areas, which prevented PV power generation from being utilized on a large scale. This article proposes a space-saving photovoltaic double-skin façade (PV-DSF) window system, which could be used in conjunction with ships to address the insufficient ship-mounted photovoltaics. In this paper, we propose a space-saving photovoltaic double-skinned façade (PV-DSF) window system that could be used in conjunction with a ship to solve the problem of insufficient space for onboard photovoltaics. According to the working principle of the system, we established a mathematical model corresponding to the actual heat transfer process and, at the same time built up a corresponding experimental test rig for thermoelectric performance measurement, and verified the accuracy of the proposed mathematical model based on the experimental results. Finally, the effect of different parameters on the performance of the system and the energy performance of the system on board the ship was discussed using a mathematical model. The simulation data showed that the increase of solar radiation intensity, wind speed, and PV coverage had a positive effect on the system's power generation, while the ambient temperature had a negative effect. The system, in combination with a passenger ship, was able to provide 53.2 kWh of annual electricity generation and reduced CO2 emissions by 17 kg. [ABSTRACT FROM AUTHOR]

The analysis on the measurement uncertainty of output power in the field test of tidal energy converters is an important process to evaluate the power characteristics performance of the tested tidal energy converter. Based on the field test data of the power characteristics performance assessment of a tidal energy converter, the measurement uncertainty calculation results of output power is analyzed. The research results show that: (1) The output power curve with measurement uncertainty information of the tested tidal energy converter that drawn in this paper, can reflect the discreteness and uncertainty of the output power during the field test period; (2) The sensitivity coefficient of tidal current velocity is a component that has a significant impact on the combined uncertainty of output power of tidal energy converters; (3) The change of the output power curve slope of the tested tidal energy converter can reflect the change of the sensitivity coefficient of tidal current velocity. The research results provide a reference for the field test work of power characteristics performance assessment of tidal energy converters in the future.

The output power of hydrogen engines is restricted due to the low volume energy density of hydrogen and lean burn, thus a turbocharger is necessary to boost the power intensity, especially for large-displacement hydrogen engines. However, turbine selection for hydrogen engines is complex comparing gasoline engines because of the different exhaust components and low exhaust temperature. In this research, the turbocharger-matching of a 5.13 L hydrogen engine is studied, and the results show the original turbine, whose maximum reduced mass flow is 0.00966 (kg/s)·Kˆ0.5/kPa, cannot achieve the desired power performance at high speeds. The reduced mass flow rate can be calculated, taking into account the effect that exhausts composition and temperature. The accuracy of the method is validated using data from a 2.3 L turbocharged H2ICE at various engine speeds and throttle openings, and the error between the measured and calculated expansion ratio is less than 5% mostly. At last, a well-matching turbine for high engine speeds of the 5.13 L hydrogen engine to meet the desired power of 120 kW, whose maximum reduced mass flow is extended to 0.0156 (kg/s)·Kˆ0.5/kPa, is selected according to the method, and the maximum power reaches 128.9 kW with a maximum torque of 662.6 N m, improving by 38.7% and 7.7% respectively comparing with the original turbine. However, the output torque reduces by 15.6% at 1200 rpm. The reduced mass flow rate varies significantly in comparison to the turbines that are well suited for low and high engine speeds respectively, thus the Variable Geometry Turbine may be the solution for both low and high speeds simultaneously for hydrogen engines. • The CNG engine turbine is not suited to H2ICE due to the low reduced mass flow rate. • The method considers exhaust components and temperature to reach desired power. • The max power is improved from 93.0 kW to 128.9 kW with the optimized turbine. • The output torque is reduced by 15.6% at 1200 rpm due to poor intake pressure. • The feature of turbocharging of H2ICE is discussed with some potential solutions. [ABSTRACT FROM AUTHOR]

In light of the diminishing reserves of fossil fuels, the escalating threat of global warming, and stringent environmental regulations, renewable energy has risen to prominence in the global energy market. This study meticulously examines the influence of turbulent flow on the performance of H-Type Vertical Axis Wind Turbines (VAWTs), a crucial aspect in the context of aerodynamic load - a significant factor affecting the reliability and longevity of wind turbine systems. The investigation was carried out using a low-speed wind tunnel, measuring 0.3 mx0.3 m, representative of an open jet type inclusive of a power section, diffuser, stilling chamber, and contraction section, cumulatively extending 2.9 m in length. Wind velocities within the range of 1 to 30 m/s were generated by inverter-controlled, electric motor-driven axial fans. To simulate turbulence, wooden grids of varied sizes were strategically placed at the tunnel's entrance. It was observed that the smaller grid size resulted in a markedly higher turbulence intensity of 64.5%, in stark contrast to the larger and medium grids, which registered at 38.1% and 12.6%, respectively. A notable inverse correlation was discerned between turbulence strength and power coefficient. Specifically, at a wind velocity of 7 m/s, the power coefficient demonstrated a substantial decrease of 94.5%, 89.5%, and 67.4% when compared to conditions with no grid, a large grid, and a medium grid, respectively. This finding elucidates the inverse relationship between turbulence strength and power efficiency. Further insights were gleaned through Computational Fluid Dynamics (CFD) simulations, conducted using ANSYS Fluent 15.0 software. The 3D CFD model was intricately constructed utilizing the multi-physics ANSYS Workbench framework, which enabled an integrated workflow from CAD design to result post-processing. The simulation results revealed a direct correlation between increased wind speed and the amount of electricity generated, underscoring the nuanced interplay between wind velocity and turbine performance in turbulent conditions. [ABSTRACT FROM AUTHOR]

Female soccer players performs between 1350-1650 activity changes, along with jumping, accelerating and decelerating. The ability to repeat these actions identically in competition are essential for success in female soccer. Hence, the study aim was to summarize relevant literature on the effects of speed and agility training in female soccer players. Literature identification were conducted according to the PRISMA guidelines and in multiple databases (Google Scholar, PubMed, Scopus, Cochrane Library, ProQuest, EBSCOhost and Science Direct). Based on the pre-defined inclusion criteria (year of publication (2003-2022), full-text study published in English, the experimental study that had included healthy and injury-free female soccer players as participant sample) database search have identified 23502 potential studies. In the end, a total of seven full-text studies were included, with a total of 165 female participants. There were a variety of experimental programs, such as resisted, assisted and traditional sprint training, high-speed treadmill, speed and agility trainings, and repeated agility and strength group, along with their comparison with strength training group. Likewise, different types of duration, intensity and frequency were observed and resulted overall speed and agility improvements in female soccer players. Authors can conclude that only with well prepared and organized program, especially in pre-season, female soccer players should be able to improve important and specific factors, in order to achieve desired aim and result in terms of speed and agility. [ABSTRACT FROM AUTHOR]

Vortex generators (VGs) have been proposed as an alternative to the power loss caused by wind turbine blade surface contamination. However, quantitative data on the effects of VGs on blade fatigue load are limited. In this study, the contamination conditions for blade tip airfoil and changes in power and fatigue load in the presence of VGs were analyzed using computational fluid dynamics and load analyses. The power curve and fatigue load of each condition were generated for a National Renewable Energy Laboratory 5 MW reference wind turbine through aeroelastic analysis. The simulations indicated that applying VGs under contamination improved the power by 1 %–3 %; however, the improvement was insufficient to restore them to the uncontaminated condition (clean); rather, the blade root flapwise damage equivalent load increased by 4 %–7 %. Consequently, regular inspection and maintenance are required to minimize power loss as an alternative to applying VGs to contaminated blades. [ABSTRACT FROM AUTHOR]

An investigation was performed to identify the wind veer impact on wind turbine power performance at a wind farm located on Jeju Island, South Korea. A 2 MW wind turbine was used as a test turbine. An 80 m-tall met mast was located 220 m away from the test wind turbine and a ground lidar was installed close to the met mast. The wind veer conditions were divided into four types: veering in upper and lower rotor (VV), veering in upper and backing in lower rotor (VB), backing in upper and lower rotor (BB) and backing in upper and veering in lower rotor (BV). The frequency of the four types was identified at the wind farm. The characteristics of wind veer was analysed in terms of diurnal variation and wind speed. In addition, the power curves of the four types were compared with that under no veer condition. Also, the power deviation coefficient (PDC) derived from the power outputs was calculated to identify the effect of the four types on the turbine power performance. As a result, the frequencies of the types, VV, VB, BB and BV were 62.7 %, 4.9 %, 9.2 % and 23.1 %, respectively. The PDCs for the types VV and BV were 3.0 % and 4.2 %, respectively, meaning a power gain while those for the types VB and BB were -2.9 % and -3.9 %, respectively, meaning a power loss.

Tidal energy resource characterisation using acoustic velocimetry sensors mounted on the seabed informs developers of the location and performance of a tidal energy converter (TEC). This work studies the consequences of miscalculating the established flow direction, i.e., the direction of assumed maximum energy yield. Considering data only above the proposed TEC cut-in velocities showed a difference in the estimated flow direction of up to 4°. Using a power weighted rotor average (PWRA) method to obtain the established flow direction resulted in a difference of less than 1° compared with the hub-height estimate. This study then analysed the impact of turbine alignment on annual energy production (AEP) estimates for a non-yawing tidal turbine. Three variants of horizontal axis tidal turbines, which operate in different locations of the water column, were examined; one using measured data, and the other two via modelled through power curves. During perfect alignment to the established flow direction, natural variations in flow meant that the estimate of AEP differed by up to 1.1% from the theoretical maximum of a fully yawed turbine. In the case of misalignment from the established flow direction, the difference in AEP increased. For a 15° misalignment, the AEP differed by up to 13%. These results quantify important uncertainties in tidal energy site design and performance assessment. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The increased availability of solar energy potential, especially in southern latitudes as in the Mediterranean Sea and the Aegean Sea regions, constitutes a strong motivation for the design and development of floating offshore solar energy platforms suitable for deployment and operation in the sea environment. In this work, a boundary element method is applied to the hydrodynamic analysis of pontoon-type floating structures carrying photovoltaic panels on the deck. Results are used to estimate the responses of the above floating structures, which are then exploited to calculate the effects of waves and motions on the energy performance of photovoltaics arranged on deck (FPVs). Using as an example a 100 kWp floating module located in the nearshore area of the Pagasitikos Gulf and Evia Island in the central Greece region, the time series of environmental parameters concerning wave, wind and solar data are used, in conjunction with the hydrodynamic responses of the floating structure, to illustrate the effects of waves on the floating PV performance. The results indicate significant variations in energy production due to the dynamic angle of solar incidence generated from the floating module's responses depending on the sea state that should be taken into account in the design process. Additionally, it is shown that the particular concept could be a promising and economically viable alternative of marine renewables contributing to the European Green Deal policies. [ABSTRACT FROM AUTHOR]

Blade extension is an important type of technical transformation to improve the energy production of turbines for early-built wind farms. To evaluate the effects of blade extension on wind turbines, a 1.5 MW commercial wind turbine with three 37.5 m long blades is taken as the research object; the power enhancement and the load variations are systemically evaluated for three different blade extension lengths (1 m, 1.5 m and 2 m) resorting to the software GH-Bladed. The load cases cover all the requirements of the IEC-61400-1 standard. It is found that the optimum tip-speed ratio λopt and the corresponding power coefficient CPmax increase with the blade extension length. The annual energy power production is enhanced by about 3%, 4% and 6% for the extension length of 1 m, 1.5 m and 2 m, respectively. The steady loads and dynamic loads, especially the thrust force of the rotor, the flapwise moment of the blade root and the overturning moment at the tower bottom, are significantly enhanced as the improvement of the power. In particular, the percentage increase of these quantities are over 10% when the extension achieves 2 m. It is also shown that blade extension can produce good economic benefit and the benefit improves with the extension length within the safety margin. The paper provides an important reference for this type of technical transformation. [ABSTRACT FROM AUTHOR]

An experimental study on the performance of a single cylinder engine fueled with hydrogen/gas fule blends was carried out. The performance of engine with different fuel components under the load characteristics of the engine was analyzed. The experimental results showed that with the increase of hydrogen blending ratio, the combustion speed was accelerated, and the maximum torque and maximum pressure in the cylinder were increased; The maximum torque of blended fuel with 40% CO 2 was 68.3% of that without CO 2 ; The maximum pressure in cylinder of blended fuel with 40% H 2 was 1.6 times higher than that without hydrogen; When the proportion of hydrogen was more than 30%, the torque decreased; When the mixture was blended with 30% N 2 , the engine torque reached the maximum at the hydrogen ratio of 15%; With the increase of hydrogen blending ratio, the emission of CO increased and the emission of HC and NOx decreased; When the hydrogen blending ratio remained unchanged, the CO emission was the largest at medium load, the HC emission was the largest at small load, and the NOx emission was the largest at high load; When the mixture was blended with 15% H 2 , with the increase of the proportion of nitrogen, emission of CO decreased, emissions of HC and NOx increased. The research of this paper provided an experimental basis for the design and development of gas fuel engines. • The maximum torque and the maximum pressure in the cylinder increase with the increase of H 2 ratio in mixture. • When the throttle opening is fixed,the engine torque of mixture blended with 15% H 2 is the maximum. • Engine power is affected by both the combustion speed and the calorific value of the mixture. • With the increase of hydrogen blending ratio, CO increases and HC and NOx decreases. • Remain H 2 unchanged, with the increase of N 2 , CO decreases, HC and NOx increase. [ABSTRACT FROM AUTHOR]

Copyright of Collegium Antropologicum is the property of Croatian Anthropological Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An investigation was performed to identify the wind veer impact on wind turbine power performance at a wind farm located on Jeju Island, South Korea. A 2 MW wind turbine was used as a test turbine. An 80 m-tall met mast was located 220 m away from the test wind turbine and a ground lidar was installed close to the met mast. The wind veer conditions were divided into four types: veering in upper and lower rotor (VV), veering in upper and backing in lower rotor (VB), backing in upper and lower rotor (BB) and backing in upper and veering in lower rotor (BV). The frequency of the four types was identified at the wind farm. The characteristics of wind veer was analysed in terms of diurnal variation and wind speed. In addition, the power curves of the four types were compared with that under no veer condition. Also, the power deviation coefficient (PDC) derived from the power outputs was calculated to identify the effect of the four types on the turbine power performance. As a result, the frequencies of the types, VV, VB, BB and BV were 62.7 %, 4.9 %, 9.2 % and 23.1 %, respectively. The PDCs for the types VV and BV were 3.0 % and 4.2 %, respectively, meaning a power gain while those for the types VB and BB were -2.9 % and -3.9 %, respectively, meaning a power loss. [ABSTRACT FROM AUTHOR]

Integration of wave energy devices with coastal protection structures could be a potentially feasible option to produce energy economically. This paper aims to assess the hydrodynamic efficiencies of wave energy converter (WEC) devices under (i) stand-alone floating conditions and (ii) when integrated with a chambered breakwater. Two different WEC model shapes, considered in the study, are a cylinder and a cylinder with a moonpool for constant mass and diameter conditions. The influence of the moonpool is observed on the hydrodynamic coefficients and heave response characteristics. The results reveal that upon integration with the chambered breakwater, the power performances of the WEC model increased by a maximum factor of 3.65 as compared to stand-alone models. The findings of the study encourage such integration of wave energy converters in coastal structures as an alternate option to enhance wave energy. [ABSTRACT FROM AUTHOR]

This long-term time series wind turbine operation dataset is from an 850 kW Vestas V52 wind turbine located in a peri-urban location in Ireland. The wind turbine has a hub height of 60 m and a rotor diameter of 52 m. The dataset ranges from 2006 to 2020 and contains the 10-minute raw data logged by the internal turbine controller system. It includes both external environmental measurements such as wind speed, wind direction and temperature, and wind turbine operating parameters such as rotor speed, blade pitch angle, generator speed and internal component operating temperatures. The data may be of interest for a variety of wind research areas including distributed wind energy, wind turbine ageing, technology improvements, design standards development and wind turbine energy performance in per-urban environments under various atmospheric conditions.

Summary: Power performance of pneumatic motor (PM) limits its application in compressed air vehicle (CAV) as an auxiliary power. This study presents an investigation of the power system with parallel operation mode based on experiments to improve the power performance of PM. First, the test bench of PM in parallel operation mode is built. Then, a series of experiments are conducted to investigate the effect of key parameters on the power performance, economy and energy conversion efficiency of CAV. The interaction among the key parameters of the PM and the influence of them on the power performance are discussed. Subsequently, the power performance, economy and energy conversion efficiency of the PM working in single and parallel operation modes are compared. Experimental results show that the maximum power output of the PM is 979 W, and the energy conversion efficiency of PMs 1 and 2 are 6.54% and 6.80% when the PM works in parallel operation mode. The parallel operation mode of PM can improve the power performance, economy and energy conversion efficiency of CAV. [ABSTRACT FROM AUTHOR]

Abstract Extensive assessment about the efficiency and quality of the power production is important to the floating wind turbine (FWT) development. The power performance of a wind turbine depends on turbine dynamics, control strategy, and atmospheric conditions. As for FWTs, the additional floater oscillations should be particularly incorporated. In this paper, extensive simulations are conducted for a Spar‐type FWT using the FAST software. The relative wind velocity introduced by floater oscillations and the corresponding power capture mechanisms are analyzed in detail. A concept of equivalent turbulence intensity is proposed to generally describe the intensity of floater oscillation. It is observed to satisfyingly serve as an independent variable for FWT power production. The mapping relationship between the FWT power generation and the equivalent turbulence intensity is constructed. Results show that the FWT output power increases linearly with the equivalent turbulence intensity square in the below‐rated region, while it is well regulated around the rated power by the bladepitch controller in the above‐rated region. The normalized power fluctuation augments linearly with equivalent turbulence intensity over the whole operating wind speeds except the rated‐nearby region. The findings are potentially helpful for the power forecasting, controller development, economical evaluation, and wind farm optimizations.

Wave energy converters (WECs) with multiple degrees of freedom based on the concept of parallel manipulators are promising devices to increase power generation. In recently published research, WECs based on parallel mechanisms were studied and showed higher output power than traditional devices. Therefore, this paper introduces the concept of the six-leg WEC and compares its performance against the single-leg and the three-leg WECs, considering they are floating devices with each leg represented by linear electrical generators. A time-domain model is developed for each device to investigate their power output in irregular waves. The annual energy production (AEP) and some indirect cost-related performance measures are assessed at four sea sites in Mexican waters, at which the mean level of wave power resource ranges between 10 and 25 kW per meter of wave-front. The results show that when compared with the single-leg and the three-leg devices, the six-leg WEC: (i) has higher values of AEP, (ii) exhibits lower performance measures, (iii) has the highest cost of energy, and (iv) could have smaller capacity electrical generators. The overall conclusion is that the power take-off machinery connected to each leg should have different capacities depending on the number of legs used. • We study a six-leg wave energy converter (WEC) in irregular waves. • We estimate the annual energy production (AEP) at four sea sites in Mexican waters. • We compare the six-leg WEC with other devices using indirect cost-related measures. • Results show the AEP of the six-leg WEC is higher than the devices analyzed. • The six-leg WEC can have smaller capacity electrical generators. [ABSTRACT FROM AUTHOR]

Six groups of electrodes with different thickness are prepared in the current study by using Li[Ni1/3Co1/3MN1/3]O2 as the active substance; the electrode thicknesses are 71.8, 65.4, 52.6, 39.3, 32.9, and 26.2 μm, respectively, with similar internal microstructures. The effect of electrode thickness on the discharge rate, pulse discharge, internal resistance, and long-term cycle life of a pouch cell are investigated. The results show that, with the decrease in the electrode thickness from 71.8 μm to 26.2 μm, the high-current-discharge performance of the cell gradually improves, the pulse-discharge power density under 50% SOC increases from 1561 W/Kg to 2691 W/Kg, the Rdis decreases from 8.70 mΩ to 3.34 mΩ, and the internal resistance decreases from 3.36 mΩ to 1.21 mΩ. In the long-term cycle-life test, the thinner the electrode thickness, the less the capacity fading of the cell; the internal resistance of the cell is observed with the increase in the cycle index. [ABSTRACT FROM AUTHOR]

Tidal energy resource characterisation using acoustic velocimetry sensors mounted on the seabed informs developers of the location and performance of a tidal energy converter (TEC). This work studies the consequences of miscalculating the established flow direction, i.e., the direction of assumed maximum energy yield. Considering data only above the proposed TEC cut-in velocities showed a difference in the estimated flow direction of up to 4°. Using a power weighted rotor average (PWRA) method to obtain the established flow direction resulted in a difference of less than 1° compared with the hub-height estimate. This study then analysed the impact of turbine alignment on annual energy production (AEP) estimates for a non-yawing tidal turbine. Three variants of horizontal axis tidal turbines, which operate in different locations of the water column, were examined; one using measured data, and the other two via modelled through power curves. During perfect alignment to the established flow direction, natural variations in flow meant that the estimate of AEP differed by up to 1.1% from the theoretical maximum of a fully yawed turbine. In the case of misalignment from the established flow direction, the difference in AEP increased. For a 15° misalignment, the AEP differed by up to 13%. These results quantify important uncertainties in tidal energy site design and performance assessment.

Wind-tunnel experiments are performed to investigate the effect of minor modifications to the roof edge shape on the power performance and wake characteristics of a horizontal-axis wind turbine sited on a cube-shaped building. Three roof edge shapes are considered: a sharp edge, a rounded edge, and a solid fence. The power performance of the turbine is dependent on its streamwise position, and on the roof edge shape due to the difference in the flow shear induced by different roof edges. The sharp edge and solid fence cases show high variation in power with the turbine position, which is reduced significantly in the rounded-edge case. The turbine shows the worst power performance regardless of its position in the fence case. The roof edge shape is also found to affect the wind turbine wake. Specifically, the wake recovery and expansion rates are found to be greatest for the fence case, and they decrease with the increasing smoothness of the roof edges. This is related to the difference in the base flow turbulence induced by different roof edge shapes. Compared to the base flow, turbulence intensity in the wake is reduced on the building, except at the rotor top tip level. [ABSTRACT FROM AUTHOR]

In this paper, an electric supercharger was installed on a GDI gasoline engine with LP EGR system. The engine performance and emission changes were experimentally investigated with electric supercharger and EGR. The experimental result shows that EGR has effects on energy saving and emission reduction. But it also decreases some power performance of engine, which electric supercharger could compensate. Electric supercharger even could enhance the engine dynamic property at low speed. Meanwhile, higher EGR rate could suppress the NOx emission to extremely low levels. But it is noticeable that high EGR rate will cause THC increase. [ABSTRACT FROM AUTHOR]

In the development of actual vehicles, manufacturers usually adopt a simplified control strategy to ensure the reliability of the control strategy based on the application scenarios. There are two main working modes for the fuel cell system in fuel cell electric vehicles in China. One is the stepped power type, and the other is the following power type. Therefore, the analysis and comparison of these two typical working modes in the power test of fuel cell electric vehicles helps determine how the fuel cell system works in the actual vehicle and how to choose energy management strategies in different application scenarios. We do the actual tests to explore how the two typical control strategies perform in actual vehicles. These two typical control strategies show different characteristics in the same test. It shows that the energy management strategies should be adopted according to the application scenarios and optimization goals. In the stepped power control strategy, the fluctuation of the fuel cell system and the frequency of starting and stopping are significantly reduced, which is beneficial to the durability of the fuel cell system. Compared with the stepped control strategy, the fluctuation of the output power of fuel cell electric vehicles with the following power control strategy increased significantly. At the same time, a simplified state of charge (SOC) test method is proposed. Due to the particularity of the stepped power control strategy, the change of capacity can be used to replace the change of SOC. For the following power control strategy, the change of electric energy can be used instead of SOC changes. [ABSTRACT FROM AUTHOR]

In this study, a hydraulic system generator power converter was modeled to verify the performance of a hydraulic-based power take-off (PTO) system. Moreover, the characteristics and output performance of the PTO system were analyzed with various load control algorithms applied for maximum power control. The simulation performance was verified through a comparison with actual sea test results. Unlike previous studies on hydraulic-based PTO system control for input power performance, the performance of a hydraulic-based PTO system was analyzed through electrical load control in this study. The electrical load control was analyzed by applying a speed control algorithm based on the perturb and observe algorithm and an optimal torque control algorithm. A load control algorithm suitable for maximum power control of the PTO system was proposed by analyzing the characteristics and power generation performance of the system according to the control variables of each algorithm. The proposed optimal torque control algorithm proved to be suitable for maximum power control of the considered PTO system. [ABSTRACT FROM AUTHOR]

Zero carbon emissions will dominate the future of internal combustion engines (ICEs). Existing technology has pushed the performance of ICEs operating on traditional working principles to almost reach their limit. The new generation of ICEs needs to explore new efficient combustion modes. For new combustion modes to simplify the emission after treatment, the opposed-piston, two-stroke (OP2S) diesel engine is a powertrain with great potential value. Combined with dual-fuel technology, the OP2S diesel engine can effectively reduce carbon emissions to achieve clean combustion. Hence, methanol/diesel dual fuel was burnt in the OP2S engine to create a clean combustion mode for future demands. In the present work, a 1D simulation model of an OP2S diesel engine was established and verified. We investigated the influence of port height to stroke ratio (HSR) on power and emission performances of the OP2S diesel engine under different methanol ratios. The results show that the methanol ratio extremely influences the indicated power (IP) with the HSR of intake ports increasing. The IP decreases by about 1.8–2.0% for every 5% increase in methanol. Correspondingly, the methanol ratio extremely influences the indicated thermal efficiency (ITE), with the HSR of exhaust ports increasing. The ITE increases by about 2.1–3.1% for every 5% increase in methanol. The increasing methanol ratio reduces the HSR of ports for the optimal IP and ITE. To balance power performance and emission performance, the methanol ratio should be kept to 10–15%. [ABSTRACT FROM AUTHOR]

This study aims to determine the optimized hydrogen–oxygen stoichiometric ratio for power performance improvement in a large-scale proton exchange membrane fuel cell (PEMFC) stack by analyzing the characteristics of internal heat and mass distributions. The power performance of a large-scale PEMFC stack consisting of the designed stack cells with the counter flow directions of hydrogen and oxygen and a coolant flow channel was experimentally evaluated. Temperatures in the central stack cell were monitored. The coupled numerical simulation model was built to analyze the power performance as well as heat and mass distribution characteristics inside a stack cell. It was found that the greatest power performance of the PEMFC stack occurred at a specific hydrogen–oxygen stoichiometric ratio, and this performance had good uniformities of the temperature and water mass fraction distributions at the proton exchange membrane (PEM). The distribution characteristics of the hydrogen and oxygen mass fractions at the interfaces between the gas diffusion layer (GDL) and the catalytic layer (CL) due to the diffusion effect were analyzed. The mechanism of enhancing power performance from an electrochemical reaction was revealed by the greater gas distribution uniformities. Furthermore, a parameter of energy conversion ratio was employed to quantify the hydrogen utilization degree. • Influence of hydrogen–oxygen stoichiometric ratio on PEMFC's performance is studied. • Power performance of a large-scale PEMFC stack is experimentally evaluated. • Mechanism of enhancing power performance is revealed by gas distribution uniformity. • Gas distribution characteristics due to interfacial diffusion effect are discussed. • Energy conversion ratio is employed to quantify the hydrogen utilization degree. [ABSTRACT FROM AUTHOR]

Supercapacitive microbial fuel cells with various anode and cathode dimensions were investigated in order to determine the effect on cell capacitance and delivered power quality. The cathode size was shown to be the limiting component of the system in contrast to anode size. By doubling the cathode area, the peak power output was improved by roughly 120% for a 10ms pulse discharge and internal resistance of the cell was decreased by ∼47%. A model was constructed in order to predict the performance of a hypothetical cylindrical MFC design with larger relative cathode size. It was found that a small device based on conventional materials with a volume of approximately 21cm(3) would be capable of delivering a peak power output of approximately 25mW at 70mA, corresponding to ∼1300Wm(-3).

The present study utilizes high-fidelity large-eddy simulation (LES) to examine the upwind-hill impacts on wind-turbine wakes and power performance. Both the LES and Reynolds-Averaged Navier–Stokes (RANS) show good agreement with the experimental results of average velocity, whereas the LES exhibits great improvements in predicting turbulence characteristics. In turbine simulations, the wake half-width shows different behaviors in the hill and flat cases. The Gaussian and cosine distributions are good representations of the unskewed profiles of velocity deficit, although some discrepancies are seen around the wake edges. However, the spanwise profiles of velocity deficit become skewed in some hill cases. The non-zero pressure gradient (NZPG) model is employed to predict the velocity deficit in the wakes of a hilltop-sited turbine, and a generalized condition is proposed so that the NZPG model can work in the scenario where the pressure gradients at the turbine location or in its near wakes are not zero. Appropriately assigning initial values for the NZPG model is important for its successful use. The presence of the upwind hill has an adverse influence on the power output of the hilltop-sited turbine. The installation of wind turbines in the valley region near upwind hills is not recommended due to the limited wind-energy resources and intense turbulence levels. • LES is employed to reproduce the flow fields over a single hill and consecutive hills. • Effect of hill intervals on turbine wakes and performance is investigated. • Effect of upwind-hill heights on turbine wakes and performance is investigated. • The NZPG model is employed to predict the velocity deficit in the wakes of a hilltop-sited turbine. • Power performance of a wind farm in the valley is evaluated. [ABSTRACT FROM AUTHOR]

An analytical model is applied to investigate the dynamic performance of a type of hybrid system (PAWT) with a semi-submersible floating offshore wind turbine (FOWT) coupled to an array of point-absorbing wave energy converters (PA). In this process, the linear potential flow theory and eigenfunction matching method are employed to study the wave–structure interactions, and a coupled set of equations is proposed to evaluate the motion response in frequency-domain. To account for the pronounced impact of nonlinear factors inherent in the hybrid system, a constellation of mathematical models has been integrated into Cummins equation framework, including aerodynamic, mooring lines, power take-off (PTO), and viscosity modeling. After running the convergence analysis and model validation, the present model is employed to clarify the effects of PTO damping, WEC radius, layout, and real sea states on the motion response and wave energy capture efficiency. Results demonstrate that integrating Wavestar-type WECs is more beneficial for improving the pitch stability of FOWT than heaving-type. Although augmenting the number of integrated WECs cannot enhance FOWT stability, it does contribute to broadening the bandwidth of the capture width ratio (CWR). Notably, the power take-off (PTO) is simplified as a linear damping to model a linear permanent magnet generator (PMG) in this study. Furthermore, the interest of this work lies in the full-process analytical model itself, which is found to be efficient in modeling the interaction of the wind-wave field and can be used in future hybrid system projects. • A full-process analytical model has been developed for hybrid systems. • Multiple types of engineering-practical hybrid systems are introduced. • The effect of PTO damping, WEC radius, layout, and sea states are discussed. • Revealing the effect factors and interconnections on the dynamic characteristic. [ABSTRACT FROM AUTHOR]

The increased availability of solar energy potential, especially in southern latitudes as in the Mediterranean Sea and the Aegean Sea regions, constitutes a strong motivation for the design and development of floating offshore solar energy platforms suitable for deployment and operation in the sea environment. In this work, a boundary element method is applied to the hydrodynamic analysis of pontoon-type floating structures carrying photovoltaic panels on the deck. Results are used to estimate the responses of the above floating structures, which are then exploited to calculate the effects of waves and motions on the energy performance of photovoltaics arranged on deck (FPVs). Using as an example a 100 kWp floating module located in the nearshore area of the Pagasitikos Gulf and Evia Island in the central Greece region, the time series of environmental parameters concerning wave, wind and solar data are used, in conjunction with the hydrodynamic responses of the floating structure, to illustrate the effects of waves on the floating PV performance. The results indicate significant variations in energy production due to the dynamic angle of solar incidence generated from the floating module’s responses depending on the sea state that should be taken into account in the design process. Additionally, it is shown that the particular concept could be a promising and economically viable alternative of marine renewables contributing to the European Green Deal policies.

Blade extension is an important type of technical transformation to improve the energy production of turbines for early-built wind farms. To evaluate the effects of blade extension on wind turbines, a 1.5 MW commercial wind turbine with three 37.5 m long blades is taken as the research object; the power enhancement and the load variations are systemically evaluated for three different blade extension lengths (1 m, 1.5 m and 2 m) resorting to the software GH-Bladed. The load cases cover all the requirements of the IEC-61400-1 standard. It is found that the optimum tip-speed ratio λopt and the corresponding power coefficient CPmax increase with the blade extension length. The annual energy power production is enhanced by about 3%, 4% and 6% for the extension length of 1 m, 1.5 m and 2 m, respectively. The steady loads and dynamic loads, especially the thrust force of the rotor, the flapwise moment of the blade root and the overturning moment at the tower bottom, are significantly enhanced as the improvement of the power. In particular, the percentage increase of these quantities are over 10% when the extension achieves 2 m. It is also shown that blade extension can produce good economic benefit and the benefit improves with the extension length within the safety margin. The paper provides an important reference for this type of technical transformation.

Summary: Microbial fuel cells (MFCs) are an essential technology in the treatment of wastewater through a series of biochemical reaction processes while generating bioenergy. The advancement of MFCs has been extensively noted, however, certain limitations in performance such as low power density and subpar wastewater treatment hinder its up‐scale and commercialization. In addition, the prototyping of MFCs and experimental approach in enhancing its performance is time‐consuming and costly. To address these concerns, this study proposes a three‐dimensional (3D) numerical model of the continuous type of dual‐chambers MFCs to redesign and investigate the effect of changing the inlet and outlet locations. By evaluating the locations of the inlet and outlet, the overall performance of the MFC is projected to improve by addressing the uneven biomass distribution in the electrodes and the uneven concentration of acetic in the solution. With the appropriate changes in the input and output locations, the results revealed that the total current density was increased by 5%. In addition, the maximum percentage of the gap between model A and model B is increased from the original 5% to 8% under 1.5 times the flow rate. This fact implies that an increase in flow rate results in a greater influence of flow field in vortex zone on the performance of MFC. The findings of this work will be useful for the up‐scale usage of MFCs for wastewater treatment in the future. [ABSTRACT FROM AUTHOR]

A novel compound power-split hybrid power system based on two planetary gear sets for commercial vehicles is developed. The equivalent lever diagram is used to investigate the components speed and torque characteristics of the system, and then the system dynamic torque control and transmission efficiency are described in equations. Six types of operating modes which are divided into two pure electric modes and four hybrid modes are analyzed by the simplified combined lever diagrams, and their torque decoupling in form of formula is derived. The hybrid transmission (HT) external characteristic is analyzed simultaneously. A control strategy which implements the rule-based (RB) method for the system is depicted. To evaluate the performance of a hybrid vehicle equipped with this hybrid system, the vehicle control and physical models are developed. Then power performance and economic performance simulations are performed. Meanwhile, corresponding tests are carried out to validate simulations. Simulation and test results indicate that, the fuel consumption for C-WTVC of the vehicle equipped with the proposed hybrid system is about 11 L/100 km and it declines by 21% compared with 14 L/100 km of the traditional vehicle. [ABSTRACT FROM AUTHOR]

Extensive assessment about the efficiency and quality of the power production is important to the floating wind turbine (FWT) development. The power performance of a wind turbine depends on turbine dynamics, control strategy, and atmospheric conditions. As for FWTs, the additional floater oscillations should be particularly incorporated. In this paper, extensive simulations are conducted for a Spar‐type FWT using the FAST software. The relative wind velocity introduced by floater oscillations and the corresponding power capture mechanisms are analyzed in detail. A concept of equivalent turbulence intensity is proposed to generally describe the intensity of floater oscillation. It is observed to satisfyingly serve as an independent variable for FWT power production. The mapping relationship between the FWT power generation and the equivalent turbulence intensity is constructed. Results show that the FWT output power increases linearly with the equivalent turbulence intensity square in the below‐rated region, while it is well regulated around the rated power by the bladepitch controller in the above‐rated region. The normalized power fluctuation augments linearly with equivalent turbulence intensity over the whole operating wind speeds except the rated‐nearby region. The findings are potentially helpful for the power forecasting, controller development, economical evaluation, and wind farm optimizations. [ABSTRACT FROM AUTHOR]

In coastal sea areas with the bimodal Ochi—Hubble wave spectrum, such as parts of the China Sea and Indian Ocean, wave energy is the superposition of wind wave and swell. Traditional heaving buoy wave energy converters developed with narrowband wave spectrums suffer from big energy loss in these areas, leading to lower power absorption efficiency and higher generating costs. In contrast, multi-freedom buoy has different resonant frequencies and maximal power capture wave frequencies in different degrees of freedom (DOFs). Therefore, this study proposed using two DOFs to capture the energy of wind wave and swell correspondingly. A heave and pitch buoy model was established by potential flow theory and validated by experimental data. Coupling effect on the motion and power absorption, power capture frequency distribution and power absorption with different linear power takeoff system damping coefficients were analyzed to reveal the hydrodynamic response and the power performance of the two DOFs. The results indicate that by using heave and pitch DOFs, the wave energy components of wind wave and swell were captured in a targeted manner. It demonstrates that the 2-DOF buoy is an effective tool to avoid the energy loss and realize the efficient power absorption in coastal sea areas with bimodal Ochi—Hubble waves. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) have received great attention for deep water wind energy harvesting. So far, research has been focused on a single floating rotor. However, for final deployment of FOWT farms, interactions of multiple FOWTs and potential impacts of the floating motion on power performance and wake of the rotors need to be investigated. In this study, we employ CFD coupled with an Actuator Disc model to analyze interactions of two tandem FOWTs for the scenario, where the upstream rotor is floating with a prescribed surge motion and the downstream rotor is fixed and influenced by the variations in the incoming flow created by the oscillating motion of the surging rotor. We will investigate three different surge amplitudes and analyze the fluctuations in power performance of the two rotors as well as their wake interactions. The results show a light increase in the mean power coefficient of both rotors for the surging case, compared against the case with no surge motion. The standard deviation of the transient C P of the surging rotor linearly scales with the surge amplitude, while such impact for the downstream rotor is very limited. Surging motion of the upstream rotor is found to enhance flow mixing in the wake, which therefore, accelerates the wake recovery of the downstream rotor. This finding suggests prospects for research into redesigning wind farm layout for FOWTs, aiming for more compact arrangements. [ABSTRACT FROM AUTHOR]

Six groups of electrodes with different thickness are prepared in the current study by using Li[Ni1/3Co1/3MN1/3]O2 as the active substance; the electrode thicknesses are 71.8, 65.4, 52.6, 39.3, 32.9, and 26.2 μm, respectively, with similar internal microstructures. The effect of electrode thickness on the discharge rate, pulse discharge, internal resistance, and long-term cycle life of a pouch cell are investigated. The results show that, with the decrease in the electrode thickness from 71.8 μm to 26.2 μm, the high-current-discharge performance of the cell gradually improves, the pulse-discharge power density under 50% SOC increases from 1561 W/Kg to 2691 W/Kg, the Rdis decreases from 8.70 mΩ to 3.34 mΩ, and the internal resistance decreases from 3.36 mΩ to 1.21 mΩ. In the long-term cycle-life test, the thinner the electrode thickness, the less the capacity fading of the cell; the internal resistance of the cell is observed with the increase in the cycle index.

SOFC solid electrolytes are known for their ionic conductivity characteristics, which increase with increasing SOFC operating temperature. Using COMSOL Multiphysics numerical simulation, analysis of SOFC power performance with yttria-stabilized zirconia (YSZ) and lithium sodium carbonate – gadolinium-doped ceria ({LiNa}2CO3-GDC) electrolytes was conducted to determine the potential of these electrolytes in their application in SOFC. The ionic conductivity of YSZ was differentiated based on the mole value of the yttria content, namely 8, 8.95, 10 and 11.54 mol. Meanwhile, GDC varied based on the (LiNa)2CO3 content such as 7.8, 10, 16.8 and 30 %. With the numerical model, the calculation error is an average of 7.32 % and 6.89 % for the experimental power and voltage values. In SOFC with the YSZ electrolyte, it was found that the power output can increase 26.4–35 times with an increase in operating temperature from 500 °C to 750 °C. SOFC with 8YSZ can produce the highest power compared to other YSZ, which is 123 A/m² at a current of 198 A/m² with an operating temperature of 500 °C and 3,440 A/m² at a current of 5,549 A/m² with an operating temperature of 750 °C. Whereas in SOFC with the GDC electrolyte, it was found that the power output can increase 18.6–22.6 times with an increase in operating temperature from 500 °C to 750 °C. SOFC with 30 % (LiNa)2CO3-GDC produced the highest power compared to other GDC, which is 231 A/m² at a current of 444 A/m² with an operating temperature of 500 °C and 5,240 A/m² at a current of 10,077 A/m² with an operating temperature of 750 °C. YSZ also showed the potential for an increase in power output as the SOFC temperature increases above 750 °C, while the 30 % variation (LiNa)2CO3-GDC shows a limited increase in ionic conductivity at 750 °C. [ABSTRACT FROM AUTHOR]