Vibrational energy harvesting : Research areas and services : Functional Materials : Science + Technology : National Physical Laboratory

Vibrational energy harvesting

Piezoelectric energy harvester

Energy harvesting is used to describe the scavenging of ambient energy in the environment that would otherwise be wasted. This energy could be in the form of heat, vibration, electromagnetic, or even acoustic, where typically the aim is to locally power autonomous devices such as wireless sensors. Generally, power levels are low and the environmental benefit of the technology is to replace batteries rather than saving energy per se.

Piezoelectric vibrational energy harvesters are usually inertial mass based devices, where a cantilever with a piezoelectric outer layer is excited into resonance by a vibration source at the root of the cantilever. The vibration could come from a number of sources for instance a pump in an oil refinery, or a rotating tyre.

Piezoelectric zinc oxide nanorods can be grown on various substrates and show promise as a flexible energy harvesting material (image courtesy of Steve Dunn, Queen Mary, University of London)

NPL's work in this area includes methods to characterise these devices with a view to understanding their efficiency, leading to ways to improve their performance. Recent work at NPL has shown that understanding of the charge redistribution mechanisms in these devices can lead to improved output.

The work also covers the scalability of the behaviour and work is being carried out on macro, micro and nano scaled devices. Recent developments in this area include a shaker table coupled to our Polytec vibrometer to investigate the performance of MEMS scale devices, and also work on the characterisation of zinc oxide nanorod devices with novel semiconductor contacts.