Piezoelectric Tires: Innovation for Sustainable Electric Mobility

The development of piezoelectric energy harvesting in automobile tires offers a sustainable alternative to battery-powered systems, addressing the environmental and public health risks associated with battery waste and disposal.

Research into these systems focuses on creating energy solutions for tire pressure monitoring systems (TPMS), which are required by law in all new cars in the United States since 2007 and in the European Union since 2022.

Traditional TPMS rely on batteries that eventually require disposal, contributing to environmental pollution. Piezoelectric energy harvesters (PEH) aim to eliminate this reliance by capturing mechanical energy directly from the vehicle’s movement.

Mechanism of Piezoelectric Energy Harvesting

Piezoelectric materials are capable of generating electrical energy when they are subjected to mechanical strain. In the context of automotive tires, this energy is captured from the cyclic deformation of the contact patch, which is the area where the tire meets the road.

One approach involves using PZT (lead zirconate titanate), a common piezoelectric ceramic material. Piezoceramic benders can be attached to pneumatic tires to generate power for onboard electronics. To maximize output, researchers have explored covering as much of the tire’s inner surface as possible with these elements, such as using a 4×40 array of bendable PZT elements bonded with flexible adhesive.

Other research focuses on the use of piezoelectric polymer blends to harness energy from moving cars by combining advanced materials with mechanical systems.

Technical Implementation and Performance

A specific design for a sustainable energy solution utilizes PZT-5 H as the piezoelectric material and an aluminum substrate for structural support. This harvester is mounted on the inner surface of the tire.

Unlike traditional methods that place harvesters on the rim where deformations are lower, mounting the device on the inner surface allows it to harvest energy from constant deformations induced by road contact and tire pressure. This placement results in more stable and higher energy production.

The efficiency of this energy production is tied to the vehicle’s operation:

• Output voltage and power increase as the car’s speed increases.
• Peak output is reached at approximately 90 km/h.
• Energy harvesting also increases based on the applied weight of the vehicle.

This level of power production is sufficient to operate TPMS and allows for the storage of excess power.

Environmental and Public Health Implications

The primary motivation for transitioning to piezoelectric systems is the reduction of environmental risks. The widespread use of batteries in automotive sensors leads to significant waste and disposal challenges, which can impact soil and water quality.

By utilizing waste mechanical energy, these piezo-tires reduce the chemical burden placed on the environment. Life cycle assessments have been used to evaluate the environmental effects of bonding piezoelectric materials to tires to ensure the process remains eco-friendly.

While early piezoelectric devices were only sufficient for low-energy gadgets or intermittent sensors, improvements in material arrays and placement are moving the technology toward providing a reliable and continuous source of energy for moving vehicles.