Exploiting Bi-Stability to Enhance Energy Capture From Turbulent Flows

This paper investigates utilizing a nonlinear (bi-stable) restoring force to enhance the transduction of galloping energy harvesters in turbulent flows. To that end, a harvester consisting of a piezoelectric cantilever beam augmented with a square-sectioned bluff body at the free end is considered. Two repulsive magnets located at the tip of the beam are used to introduce the bi-stable restoring force. Turbulence is generated in a wind tunnel using static-grid structures located in the upstream of the bluff body. Three different mesh screens with square bars are designed with different bar and mesh widths to control the Reynolds numbers and associated turbulence intensity. A series of wind tunnel tests are then used to experimentally investigate the response of the harvester with and without the tip magnets. Results demonstrate that the bi-stable restoring force can be used to improve the output power of the harvester for sufficiently large turbulence intensities.