Integrated Structures for Multimode Ambient Energy Harvesting

Harvesting energy from the environment can allow wireless electronic devices to operate indefinitely. This project is for the development of a flexible, multifunctional structure that can generate electrical power from both incident sunlight and ambient wind flow. Such a device could be an ideal power source for wireless sensors or mobile robots in areas where hardwired power is unavailable and battery replacement is costly or impractical. Combining wind and solar power takes advantage of the two major sources of ambient energy and would allow the energy harvesting system to operate both day and night. The technology developed here will benefit society and the environment by offering a new approach for creating self-reliant sensing devices that does not rely on short-term and environmentally hazardous consumable batteries. These sensors could provide structural health monitoring for bridges and buildings, collect weather or ecological data in remote areas to help understand global climate change, improve security around critical infrastructure, or even provide early warnings about natural disasters like floods or Tsunamis. In addition, the low profile and integrated nature of a wind and solar hybrid energy harvester could also be useful on rooftops and exteriors in urban areas to power sustainable buildings. In addition to its technical objectives, this project will train graduate students and provide mentored summer research experiences for underrepresented undergraduate students through a multi-university program among North Carolina's public colleges.

This work will create an integrated, solar and wind hybrid energy harvester that offers unparalleled simplicity and robustness, low mass, and a negligible increase in geometric footprint compared to a solar array alone. The envisioned device will consist of an array of slender, ribbon-like, flexible thin film solar cells that are laminated with piezoelectric patches. These piezo-solar ribbons will be mounted in longitudinal tension and exposed to a transverse wind flow, creating a fluid-elastic system that will experience aeroelastic limit cycle oscillations (LCO) over a broad range of wind speeds, causing them to vibrate in the flow like plucked guitar strings. These vibrations will produce cyclic strains in the piezoelectric layers, generating an alternating current that can be rectified and used to charge storage elements or power electrical loads. The solar cells, on the other hand, will directly transduce incident sunlight into direct current.