Thermoacoustic energy harvesting using thermally-stabilized polyacrylonitrile nanofibers

The piezoelectric conversion of thermoacoustic waves into electricity is a simple, flexible, and low-cost approach to recycle waste heat. It requires sufficient energy conversion and high material sustainability at high temperatures but remains a challenge to attain. This study demonstrates that thermally stabilized polyacrylonitrile (PAN) nanofiber membranes prepared by electrospinning and a program of heat treatment can effectively and stably convert thermoacoustic waves into sizeable electric energy at a temperature as high as 450 °C. Under mono-frequency sound (118 dB, 230 Hz), the membrane device (working area 3 × 3 cm2) can produce an open-circuit voltage as high as 118 V and short-circuit current of 12 μA (power density 392 mW/m2) in a broad temperature range (room temperature-450 °C). The working temperature has little effect on acoustoelectric output. We used a mini-thermoacoustic engine to generate thermoacoustic sound and in-situ converted the thermoacoustic waves into electric power using our acoustoelectric device. Under thermoacoustic waves, where the acoustoelectric device was heated to 280 °C, the device worked stably for at least 2 h. The electric energy generated by a single device (peak outputs 102 V and 10 μA from a 3 × 3 cm2 device) can either run commercial electronic devices (e.g., 30 LEDs) or be stored in an energy storage device such as a lithium battery and capacitor for further use. Our study differs from the prior arts in that it demonstrates the stable acoustoelectric conversion capability of thermally stabilized PAN nanofiber membranes at high temperatures and their ability to convert heat into electricity through thermoacoustic waves. This novel acoustoelectric material may be useful to develop acoustoelectric energy harvesters for various applications.