Effects on efficiency in repetitive lifting of load and frequency combinations at a constant total power output

1992 ◽  
Vol 65 (5) ◽  
pp. 469-474 ◽  
Author(s):  
M. P. de Looze ◽  
H. M. Toussaint ◽  
R. J. Nibbelke ◽  
H. A. Eelderink
Keyword(s):  
Power Output ◽  
Total Power ◽  
Repetitive Lifting ◽  
Total Power Output

scholarly journals Total power output generated during dynamic knee extensor exercise at different contraction frequencies

2000 ◽  
Vol 89 (5) ◽  
pp. 1912-1918 ◽  
Author(s):  
Richard A. Ferguson ◽  
Per Aagaard ◽  
Derek Ball ◽  
Anthony J. Sargeant ◽  
Jens Bangsbo
Keyword(s):  
Power Output ◽  
Accurate Determination ◽  
Knee Extensor ◽  
Mechanical Efficiency ◽  
Muscle Group ◽  
Total Power ◽  
Mechanical Power Output ◽  
External Power ◽  
Power Outputs ◽  
Total Power Output

A novel approach has been developed for the quantification of total mechanical power output produced by an isolated, well-defined muscle group during dynamic exercise in humans at different contraction frequencies. The calculation of total power output comprises the external power delivered to the ergometer (i.e., the external power output setting of the ergometer) and the “internal” power generated to overcome inertial and gravitational forces related to movement of the lower limb. Total power output was determined at contraction frequencies of 60 and 100 rpm. At 60 rpm, the internal power was 18 ± 1 W (range: 16–19 W) at external power outputs that ranged between 0 and 50 W. This was less ( P < 0.05) than the internal power of 33 ± 2 W (27–38 W) at 100 rpm at 0–50 W. Moreover, at 100 rpm, internal power was lower ( P < 0.05) at the higher external power outputs. Pulmonary oxygen uptake was observed to be greater ( P< 0.05) at 100 than at 60 rpm at comparable total power outputs, suggesting that mechanical efficiency is lower at 100 rpm. Thus a method was developed that allowed accurate determination of the total power output during exercise generated by an isolated muscle group at different contraction frequencies.

scholarly journals Performance assessment of a four-air cathode membraneless microbial fuel cell stack for wastewater treatment and energy extraction

2019 ◽  
Vol 116 ◽  
pp. 00093
Author(s):  
Asimina Tremouli ◽  
Pavlos K. Pandis ◽  
Theofilos Kamperidis ◽  
Vassilis N. Stathopoulos ◽  
Christos Argirusis ◽  
...  
Keyword(s):  
Power Output ◽  
Microbial Fuel Cells ◽  
Continuous Operation ◽  
Cod Removal ◽  
Total Power ◽  
Parallel Connection ◽  
Significant Information ◽  
Single Chamber ◽  
In Series ◽  
Total Power Output

A stack of two identical single chamber microbial fuel cells (MFCs) was assessed during using fermentable house hold extract as substrate. The design of the MFC units was based on the single chamber membrane-less technology using four cathode electrodes. The total power output was 492 mW either in series or parallel connection considering a total anolyte volume of 240 cm3. During continuous operation, the COD removal was 80% for each cell and for both operation modes (series and parallel). The electrochemical profiles provided significant information on the behaviour of the stack. During continuous operation, parallel connection is preferred over series connection, as it results to the same power output values, and COD removal but it provides lower internal resistances leading to more stable electrochemical performance behaviour.

scholarly journals Improved Evaluation of The Wind Power Potential of a Large Offshore Wind Farm Using Four Analytical Wake Models

2021 ◽  
Vol 11 (1) ◽  
pp. 35-48
Author(s):  
Mohammed Amine Hassoine ◽  
Fouad Lahlou ◽  
Adnane Addaim ◽  
Abdessalam Ait Madi
Keyword(s):  
Wind Direction ◽  
Power Output ◽  
Power Loss ◽  
Wind Farm ◽  
Offshore Wind ◽  
Total Power ◽  
Offshore Wind Farm ◽  
Wake Effect ◽  
Power Deficit ◽  
Total Power Output

The objective of this paper is to investigate the ability of analytical wake models to estimate the wake effects between wind turbines (WTs). The interaction of multiple wakes reduces the total power output produced by a large offshore wind farm (LOFWF). This power loss is due to the effect of turbine spacing (WTS), if the WTs are too close, the power loss is very significant. Therefore, the optimization of turbine positions within the offshore wind farm requires an understanding of the interaction of wakes inside the wind farm. To better understand the wake effect, the Horns Rev 1 offshore wind farm has been studied with four wake models, Jensen, Larsen, Ishihara, and Frandsen. A comparative study of the wake models has been performed in several situations and configurations, single and multiple wakes are taken into consideration. Results from the Horns Rev1 offshore wind farm case have  been evaluated and compared to observational data, and also  with the previous studies. The power output of a row of WTs is sensitive to the wind direction. For example, if a row of ten turbines is aligned with the 270° wind direction, the full wake condition of WTs is reached and the power deficit limit predicted by Jensen model exceeds 70%. When a wind direction changes only of  10° (260° and 280°), the deficit limit reduces to 30%. The obtained results show that a significant power deficit occurs when the turbines are arranged in an aligned manner. The findings also showed that all four models gave acceptable predictions of the total power output. The comparison between the calculated and reported power output of Horns Revs 1 showed that the differences ranged from - 8.27 MW (12.49%) to 15.27 MW (23.06%) for the Larsen and Frandsen models, respectively.

Optimal Control and Switching Mechanism of a Power Station With Identical Generators

2017 ◽  
Author(s):  
Fulai Yao ◽  
Qingbin Gao
Keyword(s):  
Optimal Control ◽  
Power Supply ◽  
Power Output ◽  
Total Power ◽  
Power Station ◽  
Efficiency Function ◽  
Novel Approach ◽  
Overall Efficiency ◽  
Total Power Output ◽  
Operating Methods

This paper proposes a novel approach for optimizing the total power output of a generalized power station with identical generators by analyzing the characteristics of the efficiency function. The introduced treatment yields the maximum total power supply and the maximum overall efficiency for the generalized power station. To achieve these, the input factor for each generator is kept the same, and the optimal switch points are selected to be the same efficiency points of two operating methods.

scholarly journals Discussion of Some Myths/Features Associated With Gas Turbine Inlet Fogging and Wet Compression

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Ting Wang ◽  
Jobaidur R. Khan
Keyword(s):  
Entropy Production ◽  
Gas Turbine ◽  
Power Output ◽  
Effective Means ◽  
Weather Conditions ◽  
Total Power ◽  
Water Evaporation ◽  
Water Droplets ◽  
Wet Compression ◽  
Total Power Output

Gas turbine (GT) inlet fogging and overspray (high-fogging) have been considered the most cost-effective means of boosting a GT's total power output, especially under hot or dry weather conditions. The result of employing fogging or overspray is indisputably clear—total power output is increased; however, development of the theory and explanation of the phenomena associated with fogging and overspray are not always consistent and are sometimes misleading and incorrect. This paper focuses on reviewing several interesting features and commonly discussed topics, including (a) entropy production of water evaporation, (b) the effect of centrifugal force on water droplets, and (c) whether water droplets can survive the journey in the compressor and enter the combustor. Furthermore, three turbine myths that fogging/overspray increases the air density in the compressor, reduces the compressor power consumption, and noticeably enhances the GT efficiency are examined and discussed. Some common mistakes in describing the compressor work are identified and corrected. A newly constructed multiphase T–s diagram is used to explain the physics of water droplet evaporation process and corresponding entropy production during wet compression.

scholarly journals Brief Communication: On the influence of vertical velocity profiles on the combined power output of two model wind turbines in yaw

2017 ◽  
Author(s):  
Jannik Schottler ◽  
Agnieszka Hölling ◽  
Joachim Peinke ◽  
Michael Hölling
Keyword(s):  
Wind Turbines ◽  
Vertical Velocity ◽  
Velocity Gradient ◽  
Power Output ◽  
Velocity Profiles ◽  
Total Power ◽  
Misalignment Angle ◽  
Velocity Gradients ◽  
Total Power Output ◽  
Vertical Velocity Gradient

Abstract. The effect of vertical velocity gradients on the total power output of two aligned model wind turbines as a function of yaw misalignment of the upstream turbine is studied experimentally. It is shown that asymmetries of the power output of the downstream turbine and the combined power of both with respect to the upstream turbine's yaw misalignment angle can be linked to the vertical velocity gradient of the inflow.

scholarly journals Acceleration and gravity power: a concept for understanding total power output

2010 ◽  
Vol 13 (sup1) ◽  
pp. 113-114
Author(s):  
Jacques Quievre ◽  
John Cronin ◽  
Nigel Harris ◽  
Boris Jidovtseff
Keyword(s):  
Power Output ◽  
Total Power ◽  
Total Power Output
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