Flexible composite thermal energy harvester using piezoelectric PVDF polymer and shape memory alloy

Abstract

A novel flexible composite thermal energy harvester is presented, which couples pyroelectric and piezoelectric effects of polyvinylidene fluoride (PVDF) with shape memory effect of a TiNiCu alloy. The harvester combines superior flexibility of PVDF with large temperature-induced strain of the shape memory alloy (SMA) to harvest small and quasi-static temperature variations. The composite with a volume of 27.5 mm 3 (post-stamp size) can harvest an energy density of 0.41 mJ/cm 3 per event, i.e. a temperature variation of 20°C. The harvester can directly power a lightemitting diode (LED) without any storage unit. The use of PVDF quadruples the energy, compared to previously reported harvesters based on PZT-fiber composites.

The Effect of Temperature and Strain on Power Conversion Efficiency of PVDF-Based Thermal Energy Harvesters

“…The power management circuit is shown in Figure 4a, comprising a switch that commutes when the PVDF capacitor is fully charged [1]. Component references are: (D) diode MURS120G3T, (L) inductor MSS1210-105KED Coilcraft (1 mH), and (C) capacitor VJ0805Y472KXCAC-Vishay (20 nF).…”

“…Recent results showed that PVDF composite harvesters are able to harvest DC-energy from thermal fluctuations or small temperature changes when coupled with shape memory materials (SMA) [1]. A power conversion circuit is connected to the harvester by a switch (thermal).…”

“…The open-circuit piezoelectric pick voltage is then discharged into the circuit. A pick voltage of 400 V for a temperature threshold at 80 °C was reported [1]. The circuit described in [1] comprises a voltage rectifier stage, an inductor, an output capacity and a free-wheeling diode.…”

“…A pick voltage of 400 V for a temperature threshold at 80 °C was reported [1]. The circuit described in [1] comprises a voltage rectifier stage, an inductor, an output capacity and a free-wheeling diode. The aim of the circuit is to convert the high voltage generated by the PVDF into a useful voltage of 1.5 V. The theoretical conversion efficiency of the circuit can reach 90% at room temperature.…”