P(VDF–TrFE) based spiral thermo-magneto-electric generators for harvesting low grade thermal energy

Low-grade thermal energy harvesting remains a challenge because of the low Carnot efficiency. Among various thermal energy harvesting mechanisms available for capturing low-grade heat (hot-side temperature less than 100°C), thermomagnetic effect has been found to be the most promising. Developing a high power density thermo-magneto-electric generator (TMEG) requires developments at both materials as well engineering levels. In this study, we propose a novel P(VDF–TrFE) based spiral-shaped cantilever beam for TMEG. Numerical simulations were performed using COMSOL Multiphysics and it was found that spiral beam experiences higher stresses, and consequently exhibits higher voltage output, as compared to rectangular cantilever beam for the same magnitude of tip deflection. Experiments revealed that the spiral structure of dimension 2.5 mm x 2.5 mm generates output voltage of about 4.0 mV, when oscillation displacement is 0.5 mm and oscillation frequency is 1 Hz. The output voltage increases with increase in tip deflection as well as oscillation frequency and a peak voltage of 25 mV is obtained at oscillation frequency of 10 Hz. (paper)