Multifunctional Materials Research at Piezo 2011

NPL's multifunctional materials team was strongly represented at the important international event, Piezo 2011. Our paper on the measurement and quantification of energy losses in piezoelectric energy harvesters provided novel insight into important loss mechanisms in energy harvesting cantilevers. This work forms part of our EMRP Metrology for Energy Harvesting project.

Charge distribution and energy loss mechanisms in piezoelectric energy harvesting cantilevers

Author(s):

Weaver P.M.,  Stewart M., Cain M.

Abstract:

Modern wireless technology offers the promise of remote sensing, communications and control, widely distributed in structures or in mobile, remote or inaccessible locations. A major limitation is imposed by the power supply requirements. Energy harvesting technology aims to use largely untapped sources of ambient energy resulting from human activity and environmental energy flows to provide the power. Piezoelectric materials are one of the most promising methods for harvesting energy from movement and vibration, particularly for micro- and nano-scale devices. Power output from piezoelectric harvesters is typically quite low so that efficiency in the harvester as well as the energy collection, storage and use is a crucial consideration. This paper presents new results on a significant source of energy loss in piezoelectric cantilevers that results from redistribution of the generated charge. It is shown that losses of 25% can occur by this mechanism. The loss mechanism is quantified and it is demonstrated  that surprisingly, the overall energy output as well as efficiency can be boosted by reducing the amount of piezoelectric material used.