Hybrid Energy Harvesting From Keyboard

This paper presents a hybrid energy harvester which combines piezoelectric (PZT) and electromagnetic (EM) transduction mechanisms to scavenge vibration energy from a keyboard. The system comprises of improvements to the dome structure presented in previous studies, in which only PZT transduction mechanism was used to harvest 16.95 mu W of experimentally verified power. An in-house modeling and simulation tool is first introduced in this work to evaluate the integration of EM transduction into the PZT system. The tool combines analytical mechanical equations and FEM results for magnetic fields for the optimization of the electromagnetically generated power. Two designs of different cost are then compared. It is concluded that the design utilizing the frequency-up-conversion technique at an incrementally higher cost is superior due to significantly higher contribution to the generated power compared to the alternative implementation without frequency-up-conversion. Modeling and simulations show an additional 2.81 mu W power can be generated through EM integration to the previous PZT based keyboard energy harvester system.