Bandwidth Improvement of a Piezoelectric Micro Energy Harvester
Typ
Examensarbete för masterexamen
Program
Applied mechanics (MPAME), MSc
Publicerad
2020
Författare
Andersson, Johan
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Energy harvesting is a technology where electricity is generated from ambient energy resources. A piezoelectric
energy harvester, which converts vibrations to electricity, is a promising power supply for sensors connected to
the Internet of Things (IoT). This kind of power supply is self sustainable and does not need any maintenance
nor external fuels.
The aim of this study is to propose a harvester design with large bandwidth for an IoT application on
micro scale. The eigenfrequencies and frequency response of the harvester are predicted by finite element
simulations and the simulation model is compared to experimental data. An electromechanical model (EMM)
is compared to a simplified pure mechanical model (PMM) and a correlation is found between the two models.
The frequencies are shifted by a factor 0.95, i.e. fEMM=fPMM = 0:95, and 1mV corresponds to 7MPa.
Key factors for bandwidth improvement are a small eigenfrequency gap and a high enough voltage level.
The eigenfrequency gap is reduced with a back folded cantilever beam design with similar beam lengths and
constant uniform thickness. For a given amplitude of the vibration source the total voltage output can be
increased with a smaller coverage of piezoelectric material.
Improved bandwidth is shown for three different beam lengths. The tolerance from the centre frequency is
about 1 %, which corresponds to a 114 Hz bandwidth in the 4100 Hz region.
Beskrivning
Ämne/nyckelord
Energy harvesting , Piezoelectricity , MEMS , Bandwidth