Hybrid/Adaptive Ambient Vibration Energy Harvesting
The Hybrid Adaptive Low Frequency, Low Intensity Vibration Energy Scavenging, or HALF-LIVES, is a system that converts ambient vibration in the environment into usable power for small scale microelectronic systems. Most ambient vibration energy is found at low frequency harmonics of 50/60 Hz from powered electromechanical devices. Devices resonating at this frequency require either sizeable or compliance and are thus difficult to miniaturize in the MEMS domain (below one cubic centimeter). The systems are designed for the smallest feasible volume while preserving low frequency operation. To offset this, MEMS research utilize the entire volume for energy transduction capturing the vibration simultaneously with both piezoelectric and electrostatic structures that comprise of the mechanical system components. The piezoelectric provides initial power rails and an inherent displacement feedback signal while the electrostatic device is a charge pump for voltage/power amplification. Being a resonant device, the maximum power is harvested when the device resonates at the dominant environmental frequency, so adaptive resonant shifting is being integrated using grayscale MEMS technology to form electrostatic virtual springs.
Figure 1: Half-Lives testing setup