System Implementation Trade-Offs for Low-Speed Rotational Variable Reluctance Energy Harvesters

Area of Science:

• Electrical Engineering
• Energy Harvesting
• Power Electronics

Background:

• Low-power energy harvesting is crucial for powering smart sensors and IoT devices.
• Kinetic energy harvesters often produce alternating current (AC) that requires rectification.
• Rectifier choice significantly impacts energy harvesting system efficiency and power output.

Purpose of the Study:

• To quantitatively compare the performance of three passive rectifiers: full-wave bridge rectifier (FWR), voltage doubler (VD), and negative voltage converter (NVC).
• To evaluate their impact on power conversion efficiency (PCE) and power extraction efficiency (PEE) in a low-voltage electromagnetic energy harvesting system.
• To assess rectifier performance in a low-speed rotational energy harvesting application (5-20 rpm) and an end-to-end self-powered sensing system.

Main Methods:

• Experimental investigation of FWR, VD, and NVC rectifiers integrated with a variable reluctance energy harvesting system.
• Measurements conducted at rotational speeds ranging from 5 rpm to 20 rpm.
• Performance evaluation using power conversion efficiency (PCE) and power extraction efficiency (PEE) metrics, followed by an end-to-end system test.

Main Results:

• The FWR exhibited lower performance (20-40% PEE) compared to VD (40-60% PEE) and NVC (20-70% PEE).
• The VD rectifier showed superior performance at lower rotational speeds.
• The NVC rectifier outperformed the VD at higher speeds (above 18 rpm).

Conclusions:

• The VD rectifier is the optimal choice for low rotational speed energy harvesting applications.
• The NVC rectifier offers better performance at higher rotational speeds.
• An end-to-end evaluation demonstrated that the VD rectifier enabled a self-powered RPM sensing system to reach its maximum sampling rate at 15.5 rpm.