Two Reports on PZT Energy Harvesting 10-27

Trying to get my ideas together.

Hurlebaus meeting tomorrow to discuss the possibility of building circuit at his lab.

Two papers:

1. Sodano, Henry A. ; Magliula, Elizabeth A.; Park, Gyuhae; Inman, Daniel J. "Electric Power Generation using Piezo Electric Devices" Center for Intelligent Material Systems and Structures, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
2. Lesieutre, George A.; Hofmann, Heath F.; Ottman, Geffrey K. "Structural Damping Due to Piezoelectric Energy Harvesting" Thirteen International Conference on Adaptive Structures and Technologies.

Sodano et al. estimate the amount of power generated by a PZT using an automobile compressor, and focus on two storing methods: using a capacitor, and a nickel metal hydride battery. For the capacitor the results show that the maximum power harvested was 2 mW, which occurs at resonance of the test plate. The average power was between 0.14-0.2 mW. The estimated power would certainly is not sufficient to operate commonly available sensors, nevertheless MRDs. The 40 mAh nickel metal hydride button cell battery was tested with two methods: (1) using a sinusoidal input signal at the resonant frequency of 63 Hz; (2) using the random signal from 0-1000Hz. The battery's charge time is about an hour for method (1) and 1.5 hours for method (2).

Lesieutre et al. state that using a piezoelectric energy harvesting system results in a damping system for the structure since it removes the mechanical energy from a vibrating structure. The system researched in the paper consists of a full bridge rectifier, a filter capacitor, a switching DC-DC step-down converter, and a battery. Testing is done with harmonic forcing.

Results:

(1)optimal switching freq 1 kHz

At high excitations: peak excitation of 68Voc, harvested power increased to 36 mW. At 50 Voc, it becomes 4 times more than 9.45 mW.

(2) step down converter

(3) breakeven point for converter operation reached when open-circuit voltage reached 21V, power consumed by harvesting circuit less than about 4.5 mW.

Under conditions of harmonic forcing, the effective modal loss factor depends on the piezoelectric system coupling coefficient and on the ratio of the operating rectifier output voltage to its maximum open-circuit value.