Thermal energy harvesting using shape memory/piezoelectric composites

The increasing demand in alternative energy sources for low-power electronics gives rise to substantial research activity in the field of energy harvesting devices in recent years. Among the different energy sources, thermal sources can be used to produce electrical energy by means of thermoelectric materials, which exploit Seebeck effect [1], or pyroelectric materials [2]. However, thermoelectric devices require large spatial temperature gradients in order to be efficient. In much the same way, pyroelectric materials are inefficient with slow variations of ambient temperature. Nevertheless there is a possibility to convert indirectly thermal energy into electrical energy through mechanical transformations [3]. Taking advantage of the large mechanical deformation (up to 10% [4]) of shape memory alloys (SMA) in the vicinity of their thermally induced phase transition one can convert this mechanical energy into electrical energy with relatively good efficiency by coupling SMA with piezoelectric materials.