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UK scientists develop optimum piezoelectric energy harvesters

March 2, 2012 - Scientists working as part of the Metrology for Energy Harvesting Project say they have developed a new model to deliver the maximum power output for piezoelectric energy harvesters.


March 2, 2012
By Anthony Capkun

Piezoelectric energy harvesters utilize energy from unwanted mechanical vibrations, such as the rattling of an air-conditioning duct or the movement of a bridge with passing traffic. Power levels are small, usually a few milliwatts or less, but the scavenged energy could be used to power autonomous devices, such as wireless sensors.

Piezoelectric energy harvesters are typically vibrating cantilevers, covered with a piezoelectric layer that converts mechanical strain to an electrical charge to power devices. Most developers cover the entire length of the cantilever with piezoelectric material in an attempt to maximize the conversion efficiency.

However, scientists based at the UK’s National Physical Laboratory—one of seven national measurement institutes involved in the European Metrology Research Programme-funded project—have discovered this approach is counterproductive. Their research shows that, due to the charge redistribution across the cantilever, there is an internal loss of power of up to 25% of potential output. To counter this, the team has developed a model to show that more energy can be converted when the beam is only covered with piezoelectric for two-thirds its length.

Current piezoelectric energy harvesting devices are used in applications such as wireless and battery-less light switches, and sensors. However, their potential applications range from the predictive maintenance of any moving or rotating machine parts, to electronic devices that harvest their own wasted operational energy to be more energy efficient. Harvesting energy that would otherwise be wasted is key to meeting future energy demands while reducing carbon emissions, say the researchers. This energy can come from light, heat, movement or vibrations.

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“The energy-harvesting market was worth $605 million in 2010 but is predicted to reach $4.4 billion by the end of this decade,” said Markys Cain, knowledge leader at NPL. “For the market to reach its true potential, we need to develop the products that can guarantee a greater energy yield and drive industrial adoption of energy-harvesting products.”

The research was originally published in Applied Physics Letters 100, 073901 (2012).