Thermal energy harvesting by piezoelectric PVDF polymer coupled with shape memory alloy

A novel flexible composite thermal energy harvester is presented, which couples pyroelectric and piezoelectric effects of polyvinylidene fluoride (PVDF) with shape memory effect of TiNiCu alloy. The harvester combines superior flexibility of PVDF with large temperature-induced strain of the shape memory alloy to harvest small and quasi-static temperature variations. The post-stamp size harvester (27.5 mm3) achieved an energy density of 0.41 mJ/cm3 per event of temperature variation of 20 °C. When reaching 70 °C the harvester, consisting of a stack of four PVDF, powered a wireless node instantaneously without any storage unit. The use of PVDF quadruples the energy output, compared to previously reported PZT-based composites.