The Specific Power Output of Aerobic Muscle, Related to the Power Density of Mitochondria

1984 ◽  
Vol 108 (1) ◽  
pp. 377-392 ◽  
Author(s):  
C. J. PENNYCUICK ◽  
MARCIO A. REZENDE
Keyword(s):  
Power Density ◽  
Power Output ◽  
Beat Frequency ◽  
Volume Ratio ◽  
Operating Frequency ◽  
Specific Power ◽  
Specific Power Output ◽  
Mechanical Power Output ◽  
Flight Muscles ◽  
High Level

A simple theory is proposed to account for the quantity of mitochondria present in aerobic muscles. Attention is restricted to muscles adapted to operate aerobically at a well-defined ‘operating frequency’. For this special case, it is shown that the volume ratio of mitochondria to myofibrils should depend on the power density of mitochondria, and the operating frequency, but not on the mechanical properties of the myofibrils. If the underlying assumptions are valid, this would mean that the specific power output of such muscles could be determined by examination of electron micrographs. We provisionally estimate that the inverse power density of mitochondria, in flight muscles running at a high temperature, is in the range 1.010−6 to 1.310−6m3W−1, that is, that a little over 1 ml of mitochondria is required to sustain 1 W of mechanical power output. On this basis, a muscle with equal volumes of mitochondria and myofibrils should be able to deliver a specific power of about 430 W kg−1, at an operating frequency around 40 Hz for nonfibrillar, or 230 Hz for fibrillar muscle. The limiting specific power should be twice this level in either case, i.e. about 860Wkg−1. It is predicted that a survey of flight muscles should yield a straight-line relationship between wing-beat frequency and the volume ratio of mitochondria to myofibrils, in a set of muscles of the same general type. It is not known whether lack of exercise, either on a long-term or short-term basis is likely to affect this. As a preliminary to such a survey, we have examined the pectoralis muscles of domesticated quail, and a wild house sparrow. Both showed a high level of variability in the mitochondria: myofibril ratio, but this may be due, at least in part, to sampling artifacts caused by the shape of mitochondrial arrays. The quail showed distinct populations of aerobic and non-aerobic fibres, apparently identical to those described in wild birds with similar flight requirements by George & Berger (1966), but the quantity of mitochondria in the aerobic fibres was less than half that expected, by comparison with other species.

Performance Comparison and Parametric Analysis of sCO2 Power Cycles Configurations

2018 ◽  
Author(s):  
Ali S. Alsagri ◽  
Andrew Chiasson ◽  
Ahmad Aljabr
Keyword(s):  
Power Output ◽  
Thermal Efficiency ◽  
Performance Comparison ◽  
Specific Power ◽  
Brayton Cycle ◽  
Computationally Efficient ◽  
Power Cycles ◽  
Optimization Study ◽  
Specific Power Output ◽  
Improve Calculation

A thermodynamic analysis and optimization of four supercritical CO2 Brayton cycles were conducted in this study in order to improve calculation accuracy; the feasibility of the cycles; and compare the cycles’ design points. In particular, the overall thermal efficiency and the power output are the main targets in the optimization study. With respect to improving the accuracy of the analytical model, a computationally efficient technique using constant conductance (UA) to represent heat exchanger performances is executed. Four Brayton cycles involved in this compression analysis, simple recaptured, recompression, pre-compression, and split expansion. The four cycle configurations were thermodynamically modeled and optimized based on a genetic algorithm (GA) using an Engineering Equation Solver (EES) software. Results show that at any operating condition under 600 °C inlet turbine temperature, the recompression sCO2 Brayton cycle achieves the highest thermal efficiency. Also, the findings show that the simple recuperated cycle has the highest specific power output in spite of its simplicity.

scholarly journals A Double-Bed Adsorptive Heat Transformer for Upgrading Ambient Heat: Design and First Tests

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4037 ◽  
Author(s):  
Mikhail Tokarev
Keyword(s):  
Steady State ◽  
Heat Generation ◽  
Power Output ◽  
Thermal Efficiency ◽  
Natural Source ◽  
Specific Power ◽  
Specific Power Output ◽  
Heat Transformer ◽  
Continuous Heat ◽  
Steady State Cycling

A full scale lab prototype of an adsorptive heat transformer (AHT), consisting of two adsorbers, an evaporator, and a condenser, was designed and tested in subsequent cycles of heat upgrading. The composite LiCl/SiO2 was used as an adsorbent with methanol as an adsorbtive substance under boundary temperatures of TL/TM/TH = −30/20/30 °C. Preliminary experiments demonstrated the feasibility of the tested AHT in continuous heat generation, with specific power output of 520 W/kg over 1–1.5 h steady-state cycling. The formal and experimental thermal efficiency of the tested rig were found to be 0.5 and 0.44, respectively. Although the low potential heat to be upgraded was available for free from a natural source, the electric efficiency of the prototype was found to be as high as 4.4, which demonstrates the promising potential of the “heat from cold” concept. Recommendations for further improvements are also outlined and discussed in this paper.

Some Aspects of the Outline Design Specification of a 0.5 kW Stirling Engine for Domestic Scale Co-Generation

1996 ◽  
Vol 210 (1) ◽  
pp. 25-33 ◽  
Author(s):  
D H Rix
Keyword(s):  
Power Output ◽  
High Volume ◽  
Combined Heat And Power ◽  
Stirling Engine ◽  
Specific Power ◽  
Design Parameters ◽  
Working Fluid ◽  
Design Specification ◽  
Specific Power Output ◽  
Chp System

This paper describes the design considerations that were involved in the production of a prototype Stirling engine, primarily intended for use in a domestic scale combined heat and power (CHP) system. These are discussed in terms of the specification of basic design parameters—configuration, working fluid, etc. First the particular requirements of this application are considered, primarily a power output of 1 kW or less, suitability for high-volume mass production, ultra long life and as high an efficiency as possible. The design that emerges is relatively simple, of low specific power output and with rather conservative operating parameters—temperature, pressure and speed.

Dragonfly flight. III. Lift and power requirements.

1997 ◽  
Vol 200 (3) ◽  
pp. 583-600 ◽  
Author(s):  
JM Wakeling ◽  
CP Ellington
Keyword(s):  
Heat Production ◽  
Power Output ◽  
Aerodynamic Force ◽  
Lift Coefficient ◽  
Mechanical Efficiency ◽  
Specific Power ◽  
Free Flight ◽  
Mechanical Power Output ◽  
Low Costs ◽  
Calopteryx Splendens

A mean lift coefficient quasi-steady analysis has been applied to the free flight of the dragonfly Sympetrum sanguineum and the damselfly Calopteryx splendens. The analysis accommodated the yaw and accelerations involved in free flight. For any given velocity or resultant aerodynamic force (thrust), the damselfly mean lift coefficient was higher than that for the dragonfly because of its clap and fling. For both species, the maximum mean lift coefficient L was higher than the steady CL,max. Both species aligned their strokes planes to be nearly normal to the thrust, a strategy that reduces the L required for flight and which is different from the previously published hovering and slow dragonfly flights with stroke planes steeply inclined to the horizontal. Owing to the relatively low costs of accelerating the wing, the aerodynamic power required for flight represents the mechanical power output from the muscles. The maximum muscle mass-specific power was estimated at 156 and 166 W kg-1 for S. sanguineum and C. splendens, respectively. Measurements of heat production immediately after flight resulted in mechanical efficiency estimates of 13 % and 9 % for S. sanguineum and C. splendens muscles, respectively.

Alternative splicing, muscle contraction and intraspecific variation: associations between troponin T transcripts, Ca2+ sensitivity and the force and power output of dragonfly flight muscles during oscillatory contraction

2001 ◽  
Vol 204 (20) ◽  
pp. 3457-3470 ◽  
Author(s):  
James H. Marden ◽  
Gail H. Fitzhugh ◽  
Mahasweta Girgenrath ◽  
Melisande R. Wolf ◽  
Stefan Girgenrath
Keyword(s):  
Intraspecific Variation ◽  
Relative Abundance ◽  
Power Output ◽  
Troponin T ◽  
Specific Power ◽  
Published Data ◽  
Specific Work ◽  
Wingbeat Frequency ◽  
Flight Muscles ◽  
Contractile Performance

SUMMARYThe flight muscles of Libellula pulchella dragonflies contain a mixture of six alternatively spliced transcripts of a single troponin T (TnT) gene. Here, we examine how intraspecific variation in the relative abundance of different TnT transcripts affects the Ca2+ sensitivity of skinned muscle fibers and the performance of intact muscles during work-loop contraction regimes that approximate in vivo conditions during flight. The relative abundance of one TnT transcript, or the pooled relative abundance of two TnT transcripts, showed a positive correlation with a 10-fold range of variation in Ca2+ sensitivity of skinned fibers (r2=0.77, P<0.0001) and a threefold range in peak specific force (r2=0.74, P<0.0001), specific work per cycle (r2=0.54; P<0.0001) and maximum specific power output (r2=0.48, P=0.0005) of intact muscle. Using these results to reanalyze previously published data for wing kinematics during free flight, we show that the relative abundances of these particular transcripts are also positively correlated with wingbeat frequency and amplitude. TnT variation alone may be responsible for these effects, or TnT variation may be a marker for changes in a suite of co-regulated molecules. Dragonflies from two ponds separated by 16 km differed significantly in both TnT transcript composition and muscle contractile performance, and within each population there are two distinct morphs that showed different maturational trajectories of TnT transcript composition and muscle contractility. Thus, there is broad intraspecific variability and a high degree of population structure for contractile performance phenotypes, TnT ribotypes and ontogenetic patterns involving these traits that affect locomotor performance.

Carbon Capture for Automobiles Using Internal Combustion Rankine Cycle Engines

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Robert W. Bilger ◽  
Zhijun Wu
Keyword(s):  
Water Vapor ◽  
Power Output ◽  
Power Plants ◽  
High Efficiency ◽  
Co2 Storage ◽  
Rankine Cycle ◽  
Internal Combustion ◽  
Production Costs ◽  
Specific Power ◽  
Specific Power Output

Internal combustion Rankine cycle (ICRC) power plants use oxy-fuel firing with recycled water in place of nitrogen to control combustion temperatures. High efficiency and specific power output can be achieved with this cycle, but importantly, the exhaust products are only CO2 and water vapor: The CO2 can be captured cheaply on condensation of the water vapor. Here we investigate the feasibility of using a reciprocating engine version of the ICRC cycle for automotive applications. The vehicle will carry its own supply of oxygen and store the captured CO2. On refueling with conventional gasoline, the CO2 will be off-loaded and the oxygen supply replenished. Cycle performance is investigated on the basis of fuel-oxygen-water cycle calculations. Estimates are made for the system mass, volume, and cost and compared with other power plants for vehicles. It is found that high thermal efficiencies can be obtained and that huge increases in specific power output are achievable. The overall power-plant system mass and volume will be dominated by the requirements for oxygen and CO2 storage. Even so, the performance of vehicles with ICRC power plants will be superior to those based on fuel cells and they will have much lower production costs. Operating costs arising from supply of oxygen and disposal of the CO2 are expected to be around 20 c/l of gasoline consumed and about $25/tonne of carbon controlled. Over all, ICRC engines are found to be a potentially competitive option for the powering of motor vehicles in the forthcoming carbon-controlled energy market.

The Isoengine: A Novel High Efficiency Engine With Optional Compressed Air Energy Storage (CAES)

2003 ◽  
Author(s):  
Claus Linnemann ◽  
Mike W. Coney ◽  
Anthony Price
Keyword(s):  
Energy Storage ◽  
Power Output ◽  
High Efficiency ◽  
Compressed Air ◽  
Specific Power ◽  
Small Scale ◽  
Compressed Air Energy Storage ◽  
Power Cycle ◽  
Specific Power Output ◽  
High Specific Power

A novel high efficiency reciprocating piston engine — the isoengine — is predicted to achieve net electrical efficiencies of up to 60% in units of 5 to 20 MWe size. The high efficiency and at the same time a high specific power output are achieved by integrating isothermal compression, recuperative preheating and isobaric combustion into a novel power cycle. The isoengine can utilize distillate oil, natural gas or suitable biofuels. While the first commercial isoengine is envisaged to have a power output of 7 MW, a 3 MW prototype engine is currently being tested. Since compression and combustion are performed in different cylinders, these processes can also be performed at different times such that the isoengine can be used to create a highly efficient small-scale compressed air energy storage (CAES) system. In such configuration, the engine can operate at more than 140% nominal load for a limited time, which depends on the air storage capacity.

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