Designing maximum power output into piezoelectric energy harvesters

2012 ◽  
Vol 21 (8) ◽  
pp. 085008 ◽  
Author(s):  
Michael W Shafer ◽  
Matthew Bryant ◽  
Ephrahim Garcia
Keyword(s):  
Power Output ◽  
Maximum Power ◽  
Energy Harvesters ◽  
Maximum Power Output ◽  
Piezoelectric Energy

Erratum: Designing maximum power output into piezoelectric energy harvesters

2012 ◽  
Vol 21 (10) ◽  
pp. 109601 ◽  
Author(s):  
Michael W Shafer ◽  
Matthew Bryant ◽  
Ephrahim Garcia
Keyword(s):  
Power Output ◽  
Maximum Power ◽  
Energy Harvesters ◽  
Maximum Power Output ◽  
Piezoelectric Energy

Modeling of a Piezoelectric Energy Harvester Mounted on a Quick-Return Mechanism

2014 ◽  
Author(s):  
Haileyesus Endeshaw ◽  
Fisseha Alemayehu ◽  
Stephen Ekwaro-Osire
Keyword(s):  
Power Output ◽  
Energy Harvester ◽  
Piezoelectric Materials ◽  
Mechanical Energy ◽  
Research Question ◽  
Electrical Energy ◽  
Maximum Power ◽  
Ambient Vibration ◽  
Maximum Power Output ◽  
Piezoelectric Energy

Piezoelectric materials are being used to harvest mechanical energy from ambient vibration and convert it to electrical energy. They are mainly used to power miniature wireless sensors such as accelerometers, tachometers and proximity probes, which are commonly used for machine monitoring applications. However, exciting a piezoelectric cantilever with its resonance frequency for maximum power output remains to be a challenge. This is because the natural frequency of piezoelectric cantilevers is much higher than the common ambient vibrations. This study answers the research question: “Does a quick-return mechanism enhance the power output of a piezoelectric energy harvester?” For this purpose, analytical methods were employed to model a piezoelectric energy harvester mounted on a quick-return mechanism. The proposed mechanism was able to generate approximately 13.5mW of power, which is 35%–75% greater than the existing designs. A study on the working frequency range of the harvester for maximum power output was employed by varying the dimensional parameters of the quick-return mechanism. It was determined that by varying the dimensions of the quick return it is possible to harvest maximum power at a range of excitation frequencies. It was demonstrated that the system can effectively produce the maximum power when excited at frequencies ranging from 2rad/s to 46rad/s.

Oxidation of combined ingestion of glucose and fructose during exercise

2004 ◽  
Vol 96 (4) ◽  
pp. 1277-1284 ◽  
Author(s):  
Roy L. P. G. Jentjens ◽  
Luke Moseley ◽  
Rosemary H. Waring ◽  
Leslie K. Harding ◽  
Asker E. Jeukendrup
Keyword(s):  
Power Output ◽  
Statistical Significance ◽  
Random Order ◽  
Carbohydrate Oxidation ◽  
Maximum Power ◽  
The Other ◽  
Cycling Exercise ◽  
Oxidation Rates ◽  
Maximum Power Output ◽  
Exercise Period

The purpose of the present study was to examine whether combined ingestion of a large amount of fructose and glucose during cycling exercise would lead to exogenous carbohydrate oxidation rates >1 g/min. Eight trained cyclists (maximal O2consumption: 62 ± 3 ml·kg-1·min-1) performed four exercise trials in random order. Each trial consisted of 120 min of cycling at 50% maximum power output (63 ± 2% maximal O2consumption), while subjects received a solution providing either 1.2 g/min of glucose (Med-Glu), 1.8 g/min of glucose (High-Glu), 0.6 g/min of fructose + 1.2 g/min of glucose (Fruc+Glu), or water. The ingested fructose was labeled with [U-13C]fructose, and the ingested glucose was labeled with [U-14C]glucose. Peak exogenous carbohydrate oxidation rates were ∼55% higher ( P < 0.001) in Fruc+Glu (1.26 ± 0.07 g/min) compared with Med-Glu and High-Glu (0.80 ± 0.04 and 0.83 ± 0.05 g/min, respectively). Furthermore, the average exogenous carbohydrate oxidation rates over the 60- to 120-min exercise period were higher ( P < 0.001) in Fruc+Glu compared with Med-Glu and High-Glu (1.16 ± 0.06, 0.75 ± 0.04, and 0.75 ± 0.04 g/min, respectively). There was a trend toward a lower endogenous carbohydrate oxidation in Fruc+Glu compared with the other two carbohydrate trials, but this failed to reach statistical significance ( P = 0.075). The present results demonstrate that, when fructose and glucose are ingested simultaneously at high rates during cycling exercise, exogenous carbohydrate oxidation rates can reach peak values of ∼1.3 g/min.

Geometric and Material Optimization of Vortex-Induced Vibration Micro Energy Harvesters for Localized Wind Environments

2012 ◽  
Author(s):  
Jesse J. French ◽  
Colton T. Sheets
Keyword(s):  
Energy Harvesting ◽  
Power Output ◽  
Fluid Velocity ◽  
Frequency Variation ◽  
Vortex Induced Vibration ◽  
Energy Harvesters ◽  
Wind Speeds ◽  
Material Optimization ◽  
Piezoelectric Energy ◽  
Wind Velocities

Wind energy capture in today’s environment is often focused on producing large amounts of power through massive turbines operating at high wind speeds. The device presented by the authors performs on the extreme opposite scale of these large wind turbines. Utilizing vortex induced vibration combined with developed and demonstrated piezoelectric energy harvesting techniques, the device produces power consistent with peer technologies in the rapidly growing field of micro-energy harvesting. Vortex-induced vibrations in the Karman vortex street are the catalyst for energy production of the device. To optimize power output, resonant frequency of the harvester is matched to vortex shedding frequency at a given wind speed, producing a lock-on effect that results in the greatest amplitude of oscillation. The frequency of oscillation is varied by altering the effective spring constant of the device, thereby allowing for “tuning” of the device to specific wind environments. While localized wind conditions are never able to be predicted with absolute certainty, patterns can be established through thorough data collection. Sampling of local wind conditions led to the design and testing of harvesters operating within a range of wind velocities between approximately 4 mph and 25 mph. For the extremities of this range, devices were constructed with resonant frequencies of approximately 17 and 163 Hz. Frequency variation was achieved through altering the material composition and geometry of the energy harvester. Experimentation was performed on harvesters to determine power output at optimized fluid velocity, as well as above and below. Analysis was also conducted on shedding characteristics of the device over the tested range of wind velocities. Computational modeling of the device is performed and compared to experimentally produced data.

scholarly journals Determination of maximum power transfer conditions of bimorph piezoelectric energy harvesters

2012 ◽  
Vol 111 (10) ◽  
pp. 102812 ◽  
Author(s):  
Mahmoud Al Ahmad ◽  
A. M. Elshurafa ◽  
K. N. Salama ◽  
H. N. Alshareef
Keyword(s):  
Maximum Power ◽  
Power Transfer ◽  
Energy Harvesters ◽  
Piezoelectric Energy

scholarly journals Scaling of Power Output in Fast Muscle Fibres of the Atlantic Cod During Cyclical Contractions

1992 ◽  
Vol 170 (1) ◽  
pp. 143-154 ◽  
Author(s):  
M. ELIZABETH ANDERSON ◽  
IAN A. JOHNSTON
Keyword(s):  
Steady State ◽  
Power Output ◽  
Standard Length ◽  
Atlantic Cod ◽  
Maximum Power ◽  
Fast Muscle ◽  
Muscle Fibres ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Length Changes

Fast muscle fibres were isolated from abdominal myotomes of Atlantic cod (Gadus morhua L.) ranging in size from 10 to 63 cm standard length (Ls). Muscle fibres were subjected to sinusoidal length changes about their resting length (Lf) and stimulated at a selected phase of the strain cycle. The work performed in each oscillatory cycle was calculated from plots of force against muscle length, the area of the resulting loop being net work. Strain and the number and timing of stimuli were adjusted to maximise positive work per cycle over a range of cycle frequencies at 8°C. Force, and hence power output, declined with increasing cycles of oscillation until reaching a steady state around the ninth cycle. The strain required for maximum power output (Wmax) was ±7-11% of Lf in fish shorter than 18 cm standard length, but decreased to ±5 % of Lf in larger fish. The cycle frequency required for Wmax also declined with increasing fish length, scaling to Ls−0.51 under steady-state conditions (cycles 9–12). At the optimum cycle frequency and strain the maximum contraction velocity scaled to Ls−0.79. The maximum stress (Pmax) produced within a cycle was highest in the second cycle, ranging from 51.3 kPa in 10 cm fish to 81.8 kPa in 60 cm fish (Pmax=28.2Ls0.25). Under steady-state conditions the maximum power output per kilogram wet muscle mass was found to range from 27.5 W in a 10 cm Ls cod to 16.4 W in a 60 cm Ls cod, scaling with Ls−0.29 and body mass (Mb)−0.10 Note: To whom reprint requests should be sent

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