Graded Metamaterials for Energy Harvesting

In our new Energy Conversion and Management article, which forms a result of a multidisciplinary collaboration with Politecnico di Milano and EMPA Materials Science and Technology, Bao Zhao and Adrea Colombi, in collaboration with Henrik Thomsen, Jacopo De Ponti, Emanuele Riva, Bart Van Damme, Andrea Bergamini, and Eleni Chatzi, present a graded metamaterial-based energy harvester targeting low-frequency ambient vibrations (<100 Hz).

The harvester combines a graded metamaterial with beam-like resonators, piezoelectric patches, and a self-powered interface circuit for broadband and high-capability energy harvesting. An integrated lumped parameter model is derived from both the mechanical and the electrical sides to determine the power performance of the proposed design. Thorough numerical simulations are carried out to optimise both the grading profile and wave field amplification, as well as to highlight the effects of spatial-frequency separation and the slow-wave phenomenon on energy harvesting performance and efficiency. Finally, experiments are conducted with realistic vibration sources to validate the derived theoretical and numerically simulated results. The harvested power of the proposed design yields a five-fold increase with respect to conventional harvesting solutions based on single cantilever harvesters.

Our results reveal that by bridging the advantages of graded metamaterials with piezoelectric energy harvesting, significant potential is obtained toward realizing self-powered Internet of Things devices.

Highlights:

• A graded metamaterial-based energy harvester is proposed for broadband and high- capability piezoelectric energy harvesting under low-frequency vibrations.
• The power performance, while using a self-powered interface circuit, is evaluated through an integrated model to accommodate the power demand of IoT devices.
• Numerical simulations and experiments are conducted to investigate the spatial frequency separation and slow-wave phenomenon in the proposed design.
• A near-milliwatt output of DC power is achieved experimentally with metamaterials for piezoelectric energy harvesting for the first time. 

Read more in the latest issue of external page Energy Conversion and Management