Energy harvesting remains a topic of intense interest, and this Spotlight provides a brief timely overview of the energy-harvesting mechanism employed by piezoelectric and pyroelectric candidate materials. Piezoelectric materials provide solid-state conversion between electrical and mechanical energy, can be manufactured at small scale, and can be integrated into microscale devices or even electronic circuits. Several potential materials and device design/configurations along with basic properties are presented. As vibration energy harvesting matures, it is likely that it will be deployed in more hostile environments. The use of pyroelectric harvesting to generate electrical energy from temperature fluctuations is less well studied. Because pyroelectric materials are also piezoelectric, designs that use thermal fluctuations or gradients to generate mechanical motion or an addition of strain to enhance the secondary pyroelectric coefficients are also of interest. Surprisingly, little work has been attempted to combine piezoelectric- and pyroelectric-based harvesting mechanisms. Keeping in view their importance for potential energy harvesters, it is warranted to describe in detail all of the relevant parameters and the available respective measurement techniques. This Spotlight describes all parameters required for piezoelectric and pyroelectric energy harvesters along with measurement techniques used by the authors.
Finally, an ambient energy-harvester testing station, developed to investigate the performance of a cantilever-based energy harvester setup in the authors' Clean Energy Laboratory, is described along with the implementation of LabVIEW software to control instruments and acquire data from a piezoelectric energy-harvesting test station. All of the experiments are performed on an isolated optical bench to avoid interference from mechanical noise that may exist in the surrounding environment. The system provides an integrated approach to characterize key performance indicators for energy-harvesting materials and devices.
This Spotlight provides step-by-step instructions to help readers set up their laboratory in order to characterize and analyze the performance of energy harvesters. The state-of-the-art instruments presented herein intended as examples, and alternative products are commercially available.