Following measurements will evaluate effectiveness of photovoltaic panel(100x80mm) and piezoelectric element(PN:LDT2-028K/L) in energy harvesting application. Photovoltaic panel is tested indoor at illuminance of about 150 lux and outside in full daylight(~10000 lux).

Conclusion: Indoor, maximum power output(red marked area) achieved with input 2.2V@440uA while outdoor with input 3.8V@13.8mA. Average current draw of the device should be around those values.

Piezoelectic element is attached to speaker membrane and driven with 50Hz sine wave to emulate vibrations produced by operating machinery. Small mass(magnets) are added to tip to see its effect on output voltage. Magnets used are: 2x1mm - 2pcs(0.04g), 3x1mm - 2pcs(0.09g), 5x1mm - 2pcs(0.26g).

Conclusion: Adding bigger mass to the tip dampens the element(lowers the resonant frequency). For maximum power output tip mass coresponding the resonant frequency of the vibration source should be chosen.