Green Footprints

By Amy Li
Senior Category (Grades 11-12)
Innovation | Energy and Natural Resources

The purpose of this project was to design a more efficient piezoelectric tile generator to harness energy from footsteps. It was expected that by mechanically increasing the frequency of stresses applied to the piezoelectric transducers, a greater and more constant supply of energy could be produced.

A traditional piezoelectric tile was built, consisting of a fibreboard on top of three piezoelectric disks. This was compared against the EnTile, which was constructed with three piezoelectric disks suspended by holders, and a grooved center piece which repeatedly depressed the edges of the disks. The two tiles were tested by applying a 4.238 kg and 5.238 kg for time intervals of 0.6 seconds and 1.0 seconds. The traditional tile was also tested at 0.3 seconds, and the EnTile at 1.3 seconds to provide further data for each individual tile. Consistent time intervals were achieved by rolling a mass specific distances down a ramp and over the piezoelectric tiles.

Graphs of voltage squared versus time were used to calculate the energy produced by each tile for each experimental setup, which clearly indicated an increase in energy production for the EnTile compared to the traditional tile. The EnTile produced more energy with the 4.238 kg mass than the 5.238 kg mass; this suggested that the EnTile can still significantly improve its efficiency by increasing the number of piezoelectric transducers per tile, thereby utilizing the extra force. With 4.238 kg, it generated 12.2 uJ at 0.6 seconds and 8.36 uJ at 1.0 seconds, an increase of 12.7 and 9.01 times compared to the traditional tile under the same conditions. From the graphs of voltage versus time that were obtained, the EnTile did not output a more continuous voltage compared to the traditional tile for the same time interval of force, but may benefit from a longer stance phase due to compression of the tile.

The EnTile has the potential to significantly increase the efficiency of piezoelectric energy harvesting. Further studies include investigating the optimal conditions for energy generation, and the use of bending piezoelectric generators to improve the output of the tile. Piezoelectric energy can be the foundation for greener footprints in the future.

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