# In‐Wheel Piezoelectric DC Power Generator With Zero Resistive Torque

## TL;DR

A new wheel-shaped generator produces electricity from motion without resistance, powering IoT devices using only movement.

## Contribution

A novel in-wheel piezoelectric generator that produces DC power with zero resistive torque and no rectification.

## Key findings

- The generator achieved 4.28 mW peak power under realistic conditions (20 kg load, 3–5 km/h).
- It successfully powered an IoT location sensor and charged a 5 V capacitor in 134 seconds.
- The system eliminates electromagnetic resistance and is suitable for low-speed, low-load environments.

## Abstract

Conventional electromagnetic generators are limited to low‐power applications owing to their mechanical complexity, bulky design, and reduced efficiency at small scales. Their performance is further hindered by the resistive torque according to Lenz's law, which makes them unsuitable for low‐load environments. To overcome these challenges, we propose a novel in‐wheel direct‐current piezoelectric generator (DC‐PG), which enables efficient power generation with zero resistive torque and does not require rectification. The system leverages continuous in‐phase polarization during rotation to deliver a stable low‐ripple DC output with minimal energy loss. Integrated into a suitcase wheel without adding weight or volume, the DC‐PG achieved a peak power of 4.28 mW under realistic conditions (20 kg load, 3–5 km/h), surpassing conventional AC‐based piezoelectric systems. It successfully powered a wireless Internet of things (IoT) location sensor, charging a 5 V capacitor in 134 s. This compact rectification‐free generator is a viable solution for small‐scale power generation and self‐powered IoT applications. Its high‐efficiency performance and elimination of electromagnetic resistance open new possibilities for energy autonomy in low‐speed, low‐load environments.

In this paper, we present a wheel‐shaped direct‐current piezoelectric generator (DC‐PG) that fundamentally overcomes these constraints by producing phase‐stable DC electricity directly from rolling motion. By embedding this system into suitcase wheels, we demonstrated a fully integrated real‐time location tracking system powered solely by mechanical motion, eliminating the need for external power or batteries.