Piezoelectric Energy Scavenging In Shoes
Joe Paradiso, Nate Shenck
 

Goal: To develop a rugged piezoelectric shoe insert and complementary conditioning electronics for unobtrusive, parasitic harvesting of the compression energy normally lost while walking....
 
 

Energy is readily available at two locations in a shoe.

Layup.GIF (3106 bytes)
 
 
 

Curvature and relaxation at the ball of the foot, and Heel strike displacement at the heel cup




Previous ML demonstrations of  Energy Scavenging in the Shoes:
 


PVDF_stave.GIF (45611 bytes)

The Media Lab PVDF flexible film stave
 


THUNDER(tm) PZT unimorph with power conditioning electronics, 12-bit encoder and RFID transmitter





The implants are unobtrusive and do not affect the gait of the bearer.  They generated 20-80 mW of peak power (1-2 mW average) during brisk walk and were demonstrated in a low-power, wireless application:


 
 
 

Work continues... ML working with TTT consortium member, Draper Laboratory:

Undetectable and interchangeable when imbedded in an insole package:

Bimorph Insole from below





A bimorph PZT design, connected in parallel, doubles the source power and cuts source impedance.

Power.GIF

Power measurements at 1.1 Hz







Power conditioningMust regulate very high-voltage, low-frequency, micro-power, capacitive source... "Direct Discharge" is lossy

Topology.GIF

Hybrid "Forward-Converter" topology





This work in progress; thesis will be completed in early May '99.

Smoothbar.GIF (1873 bytes)