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Research Papers

# Energy Harvesting Utilizing Single Crystal PMN-PT Material and Application to a Self-Powered Accelerometer

[+] Author and Article Information
H. J. Song

Department of Aerospace Engineering, Smart Structures Laboratory, University of Maryland, College Park, MD 20742hjsong@umd.edu

Y. T. Choi

Department of Aerospace Engineering, Smart Structures Laboratory, University of Maryland, College Park, MD 20742nicechoi@umd.edu

G. Wang

Techno-Sciences, Inc., Beltsville, MD 20705gwang@technosci.com

N. M. Wereley1

Department of Aerospace Engineering, Smart Structures Laboratory, University of Maryland, College Park, MD 20742wereley@umd.edu

1

Corresponding author.

J. Mech. Des 131(9), 091008 (Aug 18, 2009) (8 pages) doi:10.1115/1.3160311 History: Received December 22, 2008; Revised May 26, 2009; Published August 18, 2009

## Abstract

This study investigates the performance of an energy harvester (EH) utilizing a single crystal lead magnesium niobate-lead titanate (PMN-PT) material via analysis and experiment. The EH, intended to convert mechanical energy at a harmonic frequency such as from a fixed revolutions per minute (RPM) rotating machine, was composed of a cantilever beam having a single crystal PMN-PT patch, a tip mass, a rectifier, and an electric load. The fundamental frequency of the EH was finely adjusted via moving a tip mass spanwise. The analysis was used to select an optimal EH configuration based on a weight constraint (less than 200 g) and a narrow band frequency range (nominally 60 Hz). The analysis and performance were validated experimentally for different excitation levels. The harvested dc power was measured for low acceleration levels of 0.05–0.2 g (where $1 g=9.81 m/s2$) typical of rotating machinery. The maximum dc power generated was 19 mW for an excitation of 0.2 g. The measured power density (i.e., maximum dc power over total device volume) and measured specific power (i.e., maximum dc power over total device mass) of the energy harvester were 0.73 mW/cc and 0.096 mW/g, respectively. The EH developed in this study was compared with other configurations and types via metrics of mean square acceleration weighted power (MSAP) and MSAP density. Charging performance of the single crystal PMN-PT based EH was evaluated by recharging a battery. In addition, the effect of the capacitance of the rectifier circuit on charging time was also investigated. Finally, the EH was also used to drive an accelerometer using only energy that was harvested from ambient vibration. The accelerometer was continuously and successfully operated when the persistent excitation level exceeded 0.1 g.

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## Figures

Figure 1

Configuration of the energy harvester and rectifier circuit: (a) beam length, (b) beam width, and (c) beam thickness

Figure 2

Simulated design parameters of the energy harvester using the theoretical model (acceleration level=±0.2 g and ωn=60 Hz). Note that the total device mass includes the tip mass, the single crystal PMN-PT patch mass, and the beam mass.

Figure 3

Photograph of the experimental setup of the energy harvester using a single crystal PMN-PT patch: (a) generated dc voltage, (b) generated dc current, and (c) generated dc power

Figure 4

Measured characteristics of the energy harvester in the frequency domain (acceleration level=±0.05 g and ωn=60 Hz): (a) dc power and (b) dc current

Figure 5

Comparison of the predicted and measured characteristics of the energy harvester for different excitation levels (ωn=60 Hz), (a) power density (maximum dc power over total device volume) and (b) specific power (maximum dc power over total device mass)

Figure 6

Power density and specific power of the energy harvesting device for different excitation levels

Figure 7

Performance estimation of the single crystal PMN-PT patch based energy harvester by using the MSAP. Note that the MSAP was defined as the dc power over the mean square acceleration: (a) MSAPD and (b) MSAP.

Figure 8

Comparison of the harvesting performances of different types of energy harvesters. Note that PMN-PT means single crystal PMN-PT, EM means electromagnetic, and ES means electrostatic. In addition, the MSAPD was defined as the dc power density over the mean square acceleration.

Figure 9

Configuration of the charging circuit

Figure 10

Charging characteristics as a function of capacitance (±0.1 g excitation): (a) schematic and (b) photograph

Figure 11

Configuration of the sensor circuit module with the energy harvester

Figure 12

Operation of the accelerometer by the single crystal PMN-PT patch based energy harvester (±0.05 g excitation): (a) initial charging interval, (b) charging interval, and (c) operation interval

Figure 13

Effect of excitation acceleration level on duration of accelerometer operation when using the energy harvester to supply power

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